Method for producing polyamide resin foam particles and method for producing polyamide resin foam molded article

Abstract

Provided are: a method for producing polyamide-based resin foamed particles, with which it is possible to produce a polyamide-based resin foamed molded article having excellent moldability and excellent heat resistance and lightness; and a method for producing a polyamide-based resin foamed molded article using the polyamide-based resin foamed particles. Polyamide-based resin pellets are obtained by granulating a polyamide-based resin melt obtained by melt-kneading a base resin, an organic compound-based additive (A), and an iodide-based additive (X). Polyamide-based resin particles are foamed using a physical foaming agent to obtain polyamide-based resin foamed particles. A polyamide-based resin foam molded article is produced by in-mold molding of the polyamide-based resin foam particles. The organic compound additive (A) is composed of a hindered phenol compound and / or an organic phosphorus compound. The iodide additive (X) is composed of copper iodide, or copper iodide and potassium iodide.

Description

Technical Field

[0001] The present invention relates to a method for producing polyamide resin foamed particles using a polyamide resin as a base resin and a method for producing a polyamide resin foamed molded article. Background Art

[0002] Polyamide resin is known as a resin having high heat resistance and excellent wear resistance, chemical resistance, etc. The foamed molded body formed by foaming the polyamide resin can achieve lightweight while maintaining excellent properties such as heat resistance, wear resistance and chemical resistance. Therefore, it is expected that the polyamide resin foamed molded body will be used in automotive parts and other applications.

[0003] In order to further improve the heat resistance of polyamide resin foam moldings, the addition of heat-resistant agents such as copper iodide has been studied. For example, Patent Document 1 proposes a technique for making polyamide resin foam particles contain compounds containing base metal elements. According to Patent Document 1, polyamide resin foam particles with excellent thermal stability can be obtained by this technique.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2020 / 196893 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, by containing compounds containing base metal elements such as copper iodide, the heat resistance of polyamide resin foaming molded bodies is improved, but there is room for improvement in formability. Specifically, when attempting to perform in-mold forming of polyamide resin foamed particles containing heat-resistant agents such as copper iodide to obtain a molded body, the secondary foaming property is poor, the gaps between the foamed particles are not buried, the surface property of the molded body is poor, and there is room for improvement in the surface property of the molded body. Especially in the corners of the molded body, there is a problem that the polyamide resin foamed particle molded body is easily formed with poor secondary foaming property and poor surface property.

[0009] The present invention has been completed in view of the above background, and its purpose is to provide a method for producing polyamide resin foam particles that can produce polyamide resin foam molded bodies with excellent moldability and excellent heat resistance, and a method for producing polyamide resin foam molded bodies using the polyamide resin foam particles.

[0010] Means used to solve problems

[0011] One aspect of the present invention is a method for producing foamed polyamide resin particles according to the following [1] to [5].

[0012] [1] A method for producing polyamide resin foamed particles, which is a method for producing polyamide resin foamed particles using a polyamide resin as a base resin, wherein:

[0013] The method for producing the polyamide resin foamed particles comprises:

[0014] a step of preparing polyamide resin pellets obtained by granulating a polyamide resin melt obtained by melt-kneading the base resin, an organic compound additive (A) consisting of a hindered phenol compound and / or an organic phosphorus compound, and an iodide additive (X) consisting of copper iodide or copper iodide and potassium iodide; and

[0015] a step of foaming the polyamide resin particles using a foaming agent to obtain polyamide resin foamed particles;

[0016] The amount of the organic compound additive (A) added is 0.05 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the base resin.

[0017] The ratio of the amount of the organic compound additive (A) added to the amount of the iodide additive (X) added is 0.3 or more and 7 or less.

[0018] [2] The method for producing polyamide resin foamed particles according to [1], wherein the ratio of the amount of the organic compound additive (A) added to the amount of the iodide additive (X) added is 1 or more and 4 or less.

[0019] [3] The method for producing polyamide resin foamed particles according to [1] or [2], wherein the polyamide resin melt contains the hindered phenol compound (A1) and the organophosphorus compound (A2) as the organic compound additive (A), and the ratio of the amount of the organophosphorus compound (A2) added to the amount of the hindered phenol compound (A1) added is greater than 0.5 and less than 2.

[0020] [4] The method for producing polyamide resin foamed particles according to any one of [1] to [3], wherein the amount of the iodide-based additive (X) added is 0.1 parts by mass or more per 100 parts by mass of the base resin.

[0021] [5] The method for producing polyamide resin foamed particles according to any one of [1] to [4], wherein the polyamide resin melt further contains carbon black, and the amount of carbon black added is 0.5 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the base resin.

[0022] Another aspect of the present invention is a method for producing a polyamide-based resin foamed molded article according to the following [6].

[0023] [6] A method for producing a polyamide-based resin foamed molded article, comprising subjecting polyamide-based resin foamed particles produced by the production method described in any one of [1] to [5] to in-mold molding.

[0024] Effects of the Invention

[0025] According to the manufacturing method of the above-mentioned foamed beads, a manufacturing method of polyamide resin foamed beads that can manufacture a polyamide resin foamed molded body with excellent heat resistance with excellent formability can be provided. In addition, according to the manufacturing method of the above-mentioned molded body, a manufacturing method of polyamide resin foamed beads molded body that can manufacture a polyamide resin foamed molded body with excellent heat resistance with excellent formability can be provided. DETAILED DESCRIPTION

[0026] In this specification, "polyamide resin particles" may be referred to as "resin particles", "polyamide resin foamed particles" may be referred to as "foamed particles", and "polyamide resin foamed molded article" may be referred to as "molded article". In addition, in this specification, when a symbol such as "to" is used as an expression to indicate a numerical range, it is used to mean that the numerical values ​​described before and after the symbol are included.

[0027] [Method for producing foamed particles]

[0028] The foamed particles are manufactured by the following preparation process and foaming process, for example, for the manufacture of a molded body. The preparation process is a process for preparing polyamide resin particles. In the preparation process, a polyamide resin melt obtained by melt-kneading a base resin, an organic compound additive (A) composed of a hindered phenol compound (A1) and / or an organic phosphorus compound (A2), and an iodide additive (X) composed of copper iodide or copper iodide and potassium iodide is granulated. In the preparation process, all operations can be performed in one process, or the preparation process can be divided into, for example, a melt-kneading process and a granulation process as described below.

[0029] In the melt-kneading process, a polyamide resin melt is obtained by melt-kneading a base resin, an organic compound additive (A) and an iodide additive (X). The organic compound additive (A) refers to an organic compound composed of a hindered phenol compound and / or an organic phosphorus compound, and is a concept that does not include organic compounds other than hindered phenol compounds and organic phosphorus compounds. The iodide additive (X) refers to a metal iodide composed of copper iodide or copper iodide and potassium iodide, and is a concept that does not include metal iodides other than copper iodide and potassium iodide. In addition, the iodide additive (X) refers to copper iodide when potassium iodide is not used, and refers to copper iodide and potassium iodide when potassium iodide is used together with copper iodide.

[0030] In the granulation step, polyamide resin melt is granulated to obtain polyamide resin particles. In the foaming step, polyamide resin particles are foamed using a foaming agent to obtain polyamide resin foamed particles. Each step is described in detail below.

[0031] <Melt-kneading process>

[0032] Base resin

[0033] In the melt-kneading process, a polyamide resin is used as the base resin of the foamed particles, and the base resin is melt-kneaded together with the organic compound additive (A) and the iodide additive (X). The base resin refers to, for example, a resin whose content in the resin constituting the foamed particles exceeds 50% by mass. The content of the polyamide resin in the resin constituting the foamed particles is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. The resin constituting the foamed particles is particularly preferably substantially composed of only polyamide resin.

[0034] As the polyamide-based resin, for example, polyamide and a polyamide copolymer can be used.

[0035] Examples of the polyamide include poly(6-aminocaproic acid) also known as poly(caprolactam) (also known as polycaprolactam, nylon 6), poly(laurolactam) (also known as nylon 12), poly(hexamethylene adipamide) (also known as nylon 66), poly(7-aminoheptanoic acid) (also known as nylon 7), poly(8-aminooctanoic acid) (also known as nylon 8), poly(9-aminononanoic acid) (also known as nylon 9), poly(10-aminodecanoic acid) (also known as nylon 10), poly Homopolymers include poly(11-aminoundecanoic acid) (also known as nylon 11), poly(hexamethylenediamine sebacamide) (also known as nylon 610), poly(decamethylenediamine sebacamide) (also known as nylon 1010), poly(hexamethylenediamine azelaamide) (also known as nylon 69), poly(butylene adipamide) (also known as nylon 46), poly(butylene adipamide) (also known as nylon 410), poly(pentamethylenediamine adipamide) (also known as nylon 56), and poly(pentamethylenediamine sebacamide) (also known as nylon 510). Polyamide copolymers are those having two or more repeating units, and at least a part of each repeating unit has an amide bond. Examples of the polyamide copolymer include polycaproamide / polyhexamethylene adipamide copolymer (also known as nylon 6 / 66), caprolactam / hexamethylene adipamide / laurolactam (also known as nylon 6 / 66 / 12) copolymer, and caprolactam / laurolactam copolymer (also known as nylon 6 / 12). In the polyamide resin, one of these polyamides and polyamide copolymers may be used alone, or two or more may be used in combination. Among the above polyamide resins, at least one selected from the group consisting of nylon 6, nylon 66, nylon 6 / 66, and nylon 6 / 66 / 12 is preferred, and nylon 6 / 66 and / or nylon 6 / 66 / 12 is more preferred.

[0036] The polyamide copolymer may be a block copolymer in which a certain amount of amide of the same repeating unit is continued, and then different types of amide are continued at a certain amount, or may be a random copolymer in which different types of amide are randomly repeated, preferably a random copolymer. If the polyamide copolymer is a random copolymer, when the foamed particles are molded in-mold, they can be molded at a lower molding pressure.

[0037] The polyamide resin may be a terminal-capped polyamide resin in which the functional groups at the ends of the molecular chains are capped, thereby more reliably suppressing hydrolysis during the production process of the foamed beads and easily obtaining foamed beads that are more resistant to in-mold molding.

[0038] The end-capping of the molecular chain end can use an end-capping agent. As an end-capping agent, for example, a carbodiimide compound, an oxazoline compound, an isocyanate compound, an epoxy compound, etc. can be used, wherein a carbodiimide compound is preferably used. Specifically, aromatic monocarbodiimides such as bis(dipropylphenyl)carbodiimide (such as "Stabaxol 1-LF" manufactured by RheinChemie), aromatic polycarbodiimides (such as "Stabaxol P", "Stabaxol P100", "Stabaxol P400" manufactured by RheinChemie, etc.), aliphatic polycarbodiimides such as poly(4,4'-dicyclohexylmethanecarbodiimide) (such as "Carbodilite LA-1" manufactured by Nisshinbo Chemical (strain)), etc. can be cited. These end-capping agents can be used alone, or two or more can be used in combination.

[0039] The amount of the terminal blocking agent to be added is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, based on 100 parts by mass of the polyamide-based resin.

[0040] Other thermoplastic resins

[0041] In the melt kneading process, in addition to the polyamide resin as the base resin, other thermoplastic resins may be added within the scope of not impairing the purpose and effect of the present invention. Other thermoplastic resins include polyethylene resins, polypropylene resins, polystyrene resins, vinyl acetate resins, thermoplastic polyester resins, acrylate resins, methacrylate resins, modified polyphenylene ether resins, polycarbonate resins, polyacetal resins, polybutylene terephthalate resins, polysulfone resins, polyethersulfone resins, polyamide-imide resins, polyetherimide resins, polyetheretherketone resins, polyarylene sulfide resins, etc.

[0042] ·Organic compound additives (A), iodide additives (X)

[0043] In the melt-kneading process, hindered phenol compounds (A1) and / or organic phosphorus compounds (A2) are used as organic compound additives (A). The organic compound additives (A) are used, for example, as antioxidants for foamed particles. In addition, in the melt-kneading process, copper iodide or copper iodide and potassium iodide are used as iodide additives (X). The iodide additives (X) are used, for example, as heat resistant agents for foamed particles using polyamide resins as base resins.

[0044] In the past, in the foamed particles with polyamide resin as the base resin, the secondary foaming property of the foamed particles was sometimes insufficient, and the surface property of the molded body was poor. Especially in the corner part of the molded body, sometimes it becomes a polyamide resin foamed particle molded body with poor secondary foaming property and poor surface property. In the present disclosure, it is known that by using an organic compound additive (A) and an iodide additive (X), the heat resistance of the polyamide resin foamed particle molded body is improved, and the secondary foaming property is improved. As a result, a polyamide resin foamed particle molded body with good surface property and excellent moldability can be obtained. In addition, it is clear that the molding pressure conditions, especially the tendency to widen to the low pressure side, can be molded under low pressure, can be molded with a small amount of heating medium, and therefore can reduce the heating medium required for molding. It is further known that through the synergistic effect of the organic compound additive (A) and the iodide additive (X), foaming under high magnification can be performed, and the lightweight of the molded body is improved.

[0045] The reason for improving the formability by using the above-mentioned organic compound additive (A) and the above-mentioned iodide additive (X) is considered to be as follows. The process of obtaining a polyamide resin melt by melt-kneading a substrate resin, an organic compound additive (A) and an iodide additive (X) is carried out, for example, by supplying a substrate resin, an organic compound additive (A) and an iodide additive (X) to an extruder and melt-kneading the substrate resin, an organic compound additive (A) and an iodide additive (X) and utilizing an extruder to carry out melt-kneading. At this time, generally speaking, in order to fully melt-knead the substrate resin, the organic compound additive (A) and the iodide additive (X), melt-kneading is carried out near the melting point of the substrate resin to obtain a resin melt. It is believed that when the above-mentioned melt-kneading is carried out, the molecular chain of the polyamide resin is suppressed by the presence of an organic compound additive (A) and an iodide additive (X), and the original foaming performance of the polyamide resin can be maintained, and thus, the secondary foaming property during molding is improved, and polyamide resin foamed particles having a wide molding pressure range and excellent formability can be obtained. In addition, since the molecular chain of the polyamide resin is inhibited from being cut, foamed particles with excellent lightness can be obtained, and since the secondary foaming property during molding is improved, a foamed particle molded body with excellent lightness can be obtained. Regarding the effect of improving the moldability, even the corner portion of the molded body that is difficult to mold can obtain a polyamide resin foamed particle molded body with excellent secondary foaming property and excellent surface property. In the in-mold molding, the excellent secondary foaming property of the corner portion of the molded body means that even a thick-walled molded body or a molded body with a complex shape such as a thick-walled portion and a thin-walled portion can obtain a molded body with excellent moldability.

[0046] In addition, the process of obtaining polyamide resin foamed particles by foaming polyamide resin particles using a foaming agent is carried out, for example, by the following processes: a dispersion process, in which the resin particles are dispersed in a liquid such as water in a closed container to obtain a dispersion; an impregnation process, in which the foaming agent is impregnated in the resin particles in the dispersion; and a foaming process (in other words, an opening process), in which the resin particles containing the foaming agent are released from the closed container together with water at a pressure lower than the pressure in the closed container to foam them. In particular, when the resin particles are dispersed in water, the polyamide resin particles are plasticized and become easy to hydrolyze. It is believed that in the manufacturing method having the above-mentioned dispersion process, the above-mentioned impregnation process, and the above-mentioned foaming process, the molecular chain of the polyamide resin is further suppressed by the presence of the above-mentioned organic compound additive (A) and the above-mentioned iodide additive (X), thereby improving the secondary foaming property during molding, and easily obtaining polyamide resin foamed particles with excellent moldability.

[0047] Relative to 100 parts by mass of the substrate resin, the amount of the organic compound additive (A) added is 0.05 parts by mass or more and 5 parts by mass or less. In the case where the amount of the organic compound additive (A) added is less than 0.05 parts by mass, there is a hidden danger that the moldability improvement effect and the lightness improvement effect become insufficient. On the other hand, in the case where the amount added is greater than 5 parts by mass, there is a hidden danger of reduced moldability. From the same point of view, relative to 100 parts by mass of the substrate resin, the amount of the organic compound additive (A) added is preferably 0.1 parts by mass or more and 3 parts by mass or less, more preferably 0.1 parts by mass or more and 1.5 parts by mass or less. From the viewpoint of maintaining a wider range of moldable pressures and reducing the shrinkage of the molded body, it is further preferred that the amount of the organic compound additive (A) added satisfies 0.3 parts by mass or more and 1 part by mass or less. In addition, the amount of the organic compound additive (A) added is the sum of the amount of the hindered phenol compound (A1) added and the amount of the organic phosphorus compound (A2) added, including the case where the amount of any one of them is 0.

[0048] The organic compound additive (A) preferably includes both a hindered phenol compound (A1) and an organophosphorus compound (A2). In addition, the organic compound additive (A) more preferably includes a hindered phenol compound (A1) and an organophosphorus compound (A2), and the ratio of the amount of the organophosphorus compound (A2) added to the amount of the hindered phenol compound (A1) is greater than 0.5 and less than 2. When the ratio of the amount of the organophosphorus compound (A2) added to the amount of the hindered phenol compound (A1) satisfies a specific range, the synergistic effect of the organic compound additive (A) and the iodide additive (X) can further prevent the hydrolysis of the polyamide resin, and can obtain foamed particles with better lightweight properties. From the viewpoint of further improving this effect, when the organic compound additive (A) contains a hindered phenol compound (A1) and an organic phosphorus compound (A2), the ratio of the amount of the organic phosphorus compound (A2) added to the amount of the hindered phenol compound (A1) added is more preferably 0.7 or more and 1.5 or less, and further preferably 0.8 or more and 1.3 or less.

[0049] The hindered phenol compound (A1) preferably has 2 to 6 hindered phenol structures, and more preferably has 2 hindered phenol structures. In addition, the hindered phenol compound preferably has an amide bond, and more preferably is a hindered hindered phenol compound having an amide bond. When the hindered phenol compound is a hindered hindered phenol compound having an amide bond, the hindered phenol compound preferably has 2 to 6 amide bonds and 2 to 6 hindered hindered phenol structures, and more preferably has 2 to 6 di-tert-butyl-4-hydroxyphenylalkylcarbonylamide groups, and the number of carbon atoms in the alkyl chain part of the di-tert-butyl-4-hydroxyphenylalkylcarbonylamide group is preferably 1 to 5, and more preferably 2 to 4. As the hindered phenol compound, N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide], which is a compound represented by the following general formula (1), is particularly preferred.

[0050]

Chemistry 1

[0051]

[0052] As the organophosphorus compound (A2), for example, a triester of phosphite can be used, and examples thereof include tris(isodecyl)phosphite, tris(tridecyl)phosphite, phenyl isooctylphosphite, phenyl isodecylphosphite, phenyl di(tridecyl)phosphite, diphenyl isooctylphosphite, diphenyl isodecylphosphite, diphenyl tridecylphosphite, triphenylphosphite, tris(nonylphenyl)phosphite, 4,4'-isopropylidene diphenol alkylphosphite, trisnonylphenylphosphite, tris(dinonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, tris(biphenyl)phosphite, distearyl pentaerythritol diphosphite, di(2,4-di-tert-butylphenyl)phosphite, The present invention also includes bis(2-butylphenyl)pentaerythritol diphosphite, di(nonylphenyl)pentaerythritol diphosphite, phenylbisphenol A pentaerythritol diphosphite, tetra(tridecyl)4,4'-butylenebis(3-methyl-6-tert-butylphenol)diphosphite, hexa(tridecyl)1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane triphosphite, 3,5-di-tert-butyl-4-hydroxybenzyl diethylphosphite, sodium bis(4-tert-butylphenyl)phosphite, sodium 2,2-methylene-bis(4,6-di-tert-butylphenyl)phosphite, 1,3-bis(diphenoxyphosphinooxy)-benzene, bis(2,4-di-tert-butyl-6-methylphenyl)ethylphosphite, and the like. In addition, oligomer-type and polymer-type compounds having a phosphite structure may also be used. The organic phosphorus compound is preferably tris(2,4-di-tert-butylphenyl)phosphite represented by the following general formula (2).

[0053]

Chemistry 2

[0054]

[0055] The organic compound additive (A) composed of the hindered phenol compound (A1) and / or the organophosphorus compound (A2) is used as an antioxidant for the foamed particles, for example. Other antioxidants other than the hindered phenol compound (A1) and the organophosphorus compound (A2) may be added to the base resin without impairing the purpose and effect of the present invention. As other antioxidants, sulfur antioxidants, thioether antioxidants, etc. may be used.

[0056] The ratio of the amount of organic compound additive (A) added to the amount of iodide additive (X) added (i.e., the ratio of the total amount of hindered phenol compound (A1) and organophosphorus compound (A2) added to the total amount of copper iodide and potassium iodide added) is 0.3 or more and 7 or less. When the ratio of the amount of addition is less than 0.3, there is a hidden danger that the formability becomes insufficient. On the other hand, when the ratio of the amount of addition exceeds 7, the formability of the foamed particles becomes insufficient, and there is a hidden danger that the heat resistance of the molded body becomes insufficient and the shrinkage in a high temperature environment becomes larger. From the same point of view, the ratio of the amount of organic compound additive (A) added to the amount of iodide additive (X) is preferably 0.5 or more and 5 or less, more preferably 1 or more and 4 or less, and further preferably 1.5 or more and 3 or less. In addition, the amount of iodide additive (X) added is the sum of the amount of copper iodide added and the amount of potassium iodide added, including the case where the amount of any one of them is 0.

[0057] As described above, the iodide-based additive (X) is composed of copper iodide, or copper iodide and potassium iodide. That is, as the iodide-based additive (X), at least copper iodide is used, and potassium iodide may be used together with copper iodide.

[0058] Relative to 100 parts by mass of the substrate resin, the addition amount of the iodide-based additive (X) is preferably 0.01 parts by mass or more and 1 parts by mass or less. In this case, a molded body with better heat resistance can be made. From the same viewpoint, relative to 100 parts by mass of the substrate resin, the addition amount of the iodide-based additive is more preferably 0.02 parts by mass or more and 0.5 parts by mass or less, and further preferably 0.03 parts by mass or more and 0.2 parts by mass or less.

[0059] From the viewpoint of improving flame retardancy and further improving the above-mentioned effect brought by the combination of iodide-based additives (X) and organic compound-based additives (A), iodide-based additives (X) are preferably composed of copper iodide and potassium iodide. The addition of potassium iodide is preferably 0.5 or more and 20 or less relative to the addition of copper iodide. In this case, even if the addition of less iodide-based additives (X) can also be made into a molded body with better heat resistance. From the same viewpoint, the addition of potassium iodide is more preferably 1 or more and 10 or less relative to the addition of copper iodide, and more preferably 2 or more and 6 or less.

[0060] As described above, the iodide-based additive (X) can function as a flame retardant, but in the melt-kneading process, a flame retardant formed of a metal halide other than the iodide-based additive (X) can be added within the range that does not hinder the purpose and effect of the present invention. In this case, the amount of the iodide-based additive (X) added to the metal halide is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more, and it is particularly preferred that the metal halide is substantially composed of the iodide-based additive (X).

[0061] Examples of metal halides other than the iodide-based additive (X) include alkali metal halides such as lithium iodide, sodium iodide, lithium bromide, sodium bromide, potassium bromide, lithium chloride, sodium chloride, and potassium chloride; alkaline earth metal halides such as magnesium iodide, calcium iodide, magnesium bromide, calcium bromide, magnesium chloride, and calcium chloride; Group VII metal halides such as manganese (II) iodide, manganese (II) bromide, and manganese (II) chloride; Group VIII metal halides such as iron (II) iodide, iron (II) bromide, and iron (II) chloride; Group IX metal halides such as cobalt (II) iodide, cobalt (II) bromide, and cobalt (II) chloride; and nickel iodide. The metal halides of Group 10 include copper (I) bromide, copper (I) chloride, and other metal halides of Group 11; zinc iodide, zinc bromide, zinc chloride, and other metal halides of Group 12; aluminum (III) iodide, aluminum (III) bromide, aluminum (III) chloride, and other metal halides of Group 13; tin (II) iodide, tin (II) bromide, tin (II) chloride, and other metal halides of Group 14; antimony triiodide, antimony tribromide, antimony trichloride, bismuth (III) iodide, bismuth (III) bromide, and bismuth (III) chloride, and other metal halides of Group 15. As other metal halides, one of them may be used, or two or more of them may be used in combination.

[0062] From the perspective of further improving formability, reducing costs, and reducing adverse effects on the environment and organisms, the metal constituting the metal halide is preferably copper or zinc. In addition, from the perspective of further improving heat resistance, the halogen constituting the metal halide is preferably iodine.

[0063] The amount of metal halide added (specifically, the total amount of metal halide added other than the iodide-based additive (X) and the iodide-based additive (X)) is preferably 0.05 parts by mass or more and 1 part by mass or less relative to 100 parts by mass of the base resin. In this case, a molded body with better heat resistance can be made. From the same point of view, the amount of metal halide added is more preferably 0.07 parts by mass or more and 0.8 parts by mass or less, and further preferably 0.1 parts by mass or more and 0.6 parts by mass or less. In addition, the amount of metal halide added refers to the total amount of metal halide added including the iodide-based additive (X).

[0064] In the melt kneading process, various additives such as bubble nucleating agent, antistatic agent, conductivity imparting agent, lubricant, ultraviolet absorber, flame retardant, metal deactivator, crystal nucleating agent, colorant, filler, etc. can be appropriately added as needed. The amount of these various additives added varies according to the purpose of use of the molded body, preferably 25 parts by mass or less relative to 100 parts by mass of the base resin. More preferably, 15 parts by mass or less, more preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0065] In the melt kneading process, carbon black can be further added, and the above-mentioned polyamide resin melt can contain carbon black. The polyamide resin melt contains carbon black, and relative to 100 parts by mass of the base resin, the addition amount of carbon black is preferably 0.5 parts by mass or more and 10 parts by mass or less. In this case, black foamed particles and molded bodies with little discoloration over time can be manufactured even under high temperature environments. Therefore, foamed particles and molded bodies are suitable for vehicle components (specifically, interior components, exterior components), etc. From the same point of view, relative to 100 parts by mass of the base resin, the addition amount of carbon black is more preferably 0.7 parts by mass or more and 7 parts by mass or less, and more preferably 1.5 parts by mass or more and 5 parts by mass or less. Generally, if carbon black is added, the moldability is reduced, but in the manufacturing method disclosed in the present invention, since organic compound additives (A) and iodide additives (X) are used in specific amounts and specific ratios, excellent moldability can be maintained even if carbon black is added.

[0066] The melt kneading is performed, for example, by using an extruder. The resin temperature is, for example, 250 to 300° C. The resin temperature is the resin temperature of the head at the front end of the extruder.

[0067] <Granulation process>

[0068] In the granulation step, the polyamide resin melt is granulated. Thus, polyamide resin particles are obtained. Granulation is performed, for example, as follows. First, the polyamide resin melt is extruded from an extruder into a strand shape, and the extruded strand is cooled and solidified. Then, the solidified strand is cut. In this way, the polyamide resin melt is granulated to obtain resin particles.

[0069] <Foaming process>

[0070] As described above, the foaming process is performed, for example, through a dispersion process, an impregnation process, and an opening process. In the foaming process, the resin particles are foamed using a foaming agent to obtain foamed particles. Specifically, the foaming agent is impregnated into the resin particles, and the resin particles containing the foaming agent are foamed by heating, pressure change, volume change, etc.

[0071] As the foaming agent, an organic physical foaming agent or an inorganic physical foaming agent can be used. Examples of organic physical foaming agents include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; halogenated hydrocarbons such as chlorofluoromethane, trifluoromethane, 1,1-difluoroethane, 1,1,1,2-tetrafluoroethane, chloromethane, chloroethane, dichloromethane; and dialkyl ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether. In addition, examples of inorganic physical foaming agents include carbon dioxide, nitrogen, helium, argon, and air.

[0072] Among physical foaming agents, inorganic physical foaming agents are preferred, carbon dioxide or nitrogen is more preferred, and carbon dioxide is further preferred, from the viewpoint of having little impact on the environment, being non-flammable, and being excellent in safety.

[0073] The foaming step is not particularly limited as long as the resin particles are impregnated with the foaming agent and the resin particles are foamed, and may be performed, for example, by the following method [1] or [2].

[0074] [1] A method in which a foaming agent is impregnated into resin particles, the resin particles impregnated with the foaming agent are taken out without foaming, and then heated using a foaming device to obtain foamed particles.

[0075] [2] A method of obtaining foamed particles by impregnating a foaming agent into resin particles dispersed in a dispersion medium (specifically, liquid) in a closed device, raising the temperature to near the softening temperature of the resin, and then releasing the resin particles and the dispersion medium to the outside of the device under low pressure.

[0076] The foaming step is preferably performed by the method of [2] above.

[0077] The method of [2] is described in further detail below.

[0078] The foaming step is preferably performed through the following dispersion step, immersion step, retention step, and release step.

[0079] (1) In the dispersing step, the resin particles are dispersed in water in a sealed container to obtain a dispersion.

[0080] (2) In the impregnation step, the physical foaming agent is impregnated into the resin particles in the dispersion.

[0081] (3) In the holding step, the dispersion is held at a temperature that is 90° C. lower than the melting point (Tm) of the resin particles (Tm-90° C.) or higher and less than 50° C. lower than the melting point (Tm) of the resin particles (Tm-50° C.) for a holding time of 1 minute to 60 minutes.

[0082] (4) In the release step, the temperature (Te) of the dispersion immediately before foaming is set to a temperature that is 90°C lower than the melting point (Tm) of the resin particles (Tm-90°C) or higher and lower than a temperature that is 50°C lower than the melting point (Tm) of the resin particles (Tm-50°C), and the resin particles containing the foaming agent are released together with water from the sealed container at a pressure lower than the pressure in the sealed container to cause foaming.

[0083] The foaming process may include steps other than the dispersion process, the impregnation process, the holding process, and the release process, and other components may be further added in any of the steps. The impregnation process and the holding process may be performed simultaneously, and the holding process may be performed before or after the impregnation process.

[0084] (Dispersion process)

[0085] The dispersion process is a process of dispersing the resin particles in water in a closed container to obtain a dispersion. There is no particular limitation on the method for dispersing the resin particles in water, and a known method can be used. For example, a stirrer is used to add resin particles to water while stirring the water, and further stirring is performed to obtain a dispersion. In addition, it is preferred to add dispersants such as inorganic substances such as aluminum oxide, tricalcium phosphate, magnesium pyrophosphate, zinc oxide, kaolin, mica, talc, and montmorillonite to the dispersion as needed; and dispersing aids such as anionic surfactants such as sodium dodecylbenzene sulfonate and sodium alkane sulfonate. The mass ratio of resin particles to dispersant (resin particles / dispersant) is preferably 20 to 2000, and more preferably 30 to 1000. In addition, the mass ratio of dispersant to dispersant (dispersant / dispersant) is preferably 1 to 500, and more preferably 1 to 100.

[0086] (Immersion process)

[0087] The impregnation step is a step of impregnating the resin particles in the dispersion with the foaming agent. In addition, the resin particles can also be made to absorb water at the same time. The method of impregnating the resin particles with the foaming agent is not particularly limited, and it is preferred that the resin particles are dispersed in water in a pressurized closed container such as an autoclave, and the foaming agent is impregnated in the resin particles. In addition, from the viewpoint of fully impregnating the resin particles with the foaming agent in a short time, the impregnation of the resin particles with the foaming agent is preferably performed by heating on the basis of pressurization.

[0088] The immersion step includes a step of increasing the pressure in the sealed container from the atmospheric pressure to the pressure during immersion (hereinafter also referred to as immersion pressure) when pressurization is performed.

[0089] The step of impregnating the foaming agent includes a step of heating a dispersion obtained by dispersing resin particles in water from room temperature to a temperature for impregnation (hereinafter also referred to as an impregnation temperature).

[0090] When the impregnation process is carried out under heating, from the viewpoint of allowing the foaming agent to be fully impregnated into the resin particles in a short time, the impregnation temperature is preferably 50°C or more, more preferably 80°C or more, and preferably below the melting point (Tm (°C)) of the resin particles, more preferably below (Tm-20 (°C)).

[0091] In addition, regarding the pressure during the impregnation under pressure (hereinafter also referred to as the impregnation pressure), from the viewpoint of sufficiently impregnating the foaming agent into the resin particles in a short time, it is preferred that the pressure in the closed container be 1.5 MPa (G) or more, more preferably 2.5 MPa (G) or more, preferably 7 MPa (G) or less, and more preferably 5 MPa (G) or less by adding the foaming agent into the container containing the dispersion. In addition, "(G)" means a gauge pressure, and for example, "1.5 MPa (G)" means a gauge pressure of 1.5 MPa.

[0092] The dispersion process and the impregnation process also have the function of making the resin particles absorb water. From the viewpoint of allowing the resin particles to fully absorb water and plasticize, the total time of the process of obtaining the dispersion and the process of impregnating the foaming agent is preferably more than 20 minutes, and more preferably more than 30 minutes. On the other hand, from the viewpoint of the productivity of the foamed particles, the above time is preferably less than 60 minutes. In addition, from the viewpoint of allowing the resin particles to fully absorb water and plasticize, the heating rate in the impregnation process is preferably set to less than 10°C / minute, and more preferably to less than 7°C / minute. On the other hand, from the viewpoint of the productivity of the foamed particles, the heating rate is preferably set to more than 1°C / minute, and more preferably to more than 2°C / minute.

[0093] (Maintaining process)

[0094] The holding step is a step of holding the dispersion liquid at a temperature (Tm-90°C) that is 90°C lower than the melting point (Tm) of the resin particles and less than a temperature (Tm-50°C) that is 50°C lower than the melting point (Tm) of the resin particles for a holding time of 1 minute to 60 minutes. From the viewpoint of allowing the polyamide resin to fully absorb water and plasticize, and from the viewpoint of allowing the foaming agent to be uniformly impregnated into the resin particles, the holding temperature of the dispersion liquid in the holding step is a temperature (Tm-90°C) that is 90°C lower than the melting point (Tm) of the resin particles, preferably a temperature (Tm-80°C) that is 80°C lower than the melting point (Tm) of the resin particles, more preferably a temperature (Tm-70°C) that is 70°C lower than the melting point (Tm) of the resin particles, and even more preferably a temperature (Tm-80°C) that is 80°C lower than the melting point (Tm) of the resin particles. The melting point (Tm) of the fat particles is at least a temperature (Tm-65°C) that is 65°C lower than the melting point (Tm) of the resin particles, and is less than a temperature (Tm-50°C) that is 50°C lower than the melting point (Tm) of the resin particles, preferably a temperature (Tm-55°C) that is 55°C lower than the melting point (Tm) of the resin particles, more preferably a temperature (Tm-57°C) that is 57°C lower than the melting point (Tm) of the resin particles, and further preferably a temperature (Tm-59°C) that is 59°C lower than the melting point (Tm) of the resin particles.

[0095] Usually, when manufacturing foamed particles using a general-purpose resin such as a polypropylene resin as a base resin, the particles are maintained near the melting point of the raw material resin. However, in the method for manufacturing foamed particles using a polyamide resin as a base resin, it is preferred to maintain the particles at a temperature (Tm-90°C) that is 90°C lower than the melting point (Tm) of the resin particles and at a temperature (Tm-50°C) that is 50°C lower than the melting point (Tm) of the resin particles. It is believed that this is because, since the polyamide resin is hygroscopic, the resin particles are plasticized by the water used as the dispersion liquid, and the melting point is greatly reduced. As a result, the foamed particles can be manufactured at a temperature that is significantly lower than the melting point of the resin particles.

[0096] From the viewpoint that the foaming agent is uniformly impregnated in the resin particles, the foamed particles with high independent bubble rate are obtained, the holding time in the maintenance process is preferably more than 1 minute, more preferably more than 5 minutes, more preferably more than 10 minutes, and more preferably more than 13 minutes. And, from the viewpoint of the productivity of the foamed particles and the viewpoint of preventing the hydrolysis of the polyamide resin, the holding time in the operation maintained is preferably less than 60 minutes, more preferably less than 40 minutes, more preferably less than 30 minutes, more preferably less than 20 minutes, and particularly preferably less than 18 minutes. By maintaining with the above-mentioned time, it is possible to obtain polyamide resin foamed particles with low apparent density and high independent bubble rate. The operation maintained can also be set to multiple stages within the above-mentioned temperature range, and in addition, it is also possible to slowly heat up by needing sufficient time within the temperature range. From the viewpoint that can be easily manufactured, it is preferably set to a stage (keeping the temperature constant) within the above-mentioned temperature range, and maintain the above-mentioned time.

[0097] From the viewpoint of making the foaming agent uniformly impregnated in the resin particles, the holding step is preferably performed under pressure, and preferably the same pressure as the impregnation pressure is maintained. The pressure in the container containing the dispersion is preferably 1.5 MPa (G) or more, and more preferably 2.5 MPa (G) or more. In addition, the pressure in the container containing the dispersion is preferably 7 MPa (G) or less, and more preferably 5 MPa (G) or less.

[0098] (Release process)

[0099] The release step is a step of foaming the resin particles impregnated with the foaming agent, and is performed by releasing the resin particles impregnated with the foaming agent together with water into a pressure atmosphere lower than the pressure in the holding step (usually atmospheric pressure) to foam them. The release step is performed, for example, following the holding step.

[0100] From the viewpoint of obtaining foamed particles having a low apparent density and a high independent cell ratio, the temperature Te of the dispersion just before foaming (hereinafter also referred to as the foaming temperature) is preferably a temperature 90°C lower than the melting point (Tm) of the resin particles (Tm-90°C) or higher, more preferably a temperature 80°C lower than the melting point (Tm) of the resin particles (Tm-80°C) or higher, further preferably a temperature 70°C lower than the melting point (Tm) of the resin particles (Tm-70°C) or higher, and still further preferably a temperature 65°C lower than the melting point (Tm) of the resin particles (Tm-65°C) or higher. In addition, the foaming temperature is preferably a temperature 50°C lower than the melting point (Tm) of the resin particles (Tm-50°C), more preferably a temperature 55°C lower than the melting point (Tm) of the resin particles (Tm-55°C), further preferably a temperature 57°C lower than the melting point (Tm) of the resin particles (Tm-57°C), and further preferably a temperature 59°C lower than the melting point (Tm) of the resin particles (Tm-59°C).

[0101] The pressure (foaming pressure) immediately before the release in the release process is preferably 0.5 MPa (G) or more, more preferably 1.5 MPa (G) or more, and further preferably 2.5 MPa (G) or more. In addition, the foaming pressure is preferably 10 MPa (G) or less, more preferably 7 MPa (G) or less, and further preferably 5 MPa (G) or less.

[0102] [Foaming particles]

[0103] (Apparent density)

[0104] The apparent density of the foamed particles is preferably 50 to 200 kg / m 3 In this case, the foamed particles and the molded body have excellent lightness and can fully exert the mechanical properties of the polyamide resin. From the viewpoint of further improving this effect, the apparent density of the foamed particles is more preferably 55 to 150 kg / m 3 , more preferably 60 to 130 kg / m 3 The apparent density was measured as follows. First, the apparent density of about 500 cm was measured after being left for 2 days under the conditions of 50% relative humidity, 23°C, and 1 atm. 3 Next, prepare a measuring cylinder filled with water at a temperature of 23°C, and use a metal mesh to sink the foamed particles whose mass has been measured into the measuring cylinder. Considering the volume of the metal mesh, measure the volume V1 of the foamed particles read from the water level rise [unit: cm 3 ], divide the mass W1[g] of the foamed particles by the volume V1 (W1 / V1) and convert the unit to [kg / m 3 ], and the apparent density of the foamed particles is calculated.

[0105] [Method for producing molded article]

[0106] The foamed beads are molded into a mold to obtain a molded body, which is formed by the foamed beads being fused together.

[0107] The in-mold forming method can adopt the conventional known method, preferably using heating using steam. Through steam, the polyamide resin in the foamed particles absorbs water and plasticizes, so the forming pressure can be reduced. In addition, if the obtained molded body is dried and moisture is removed, the original physical property of the polyamide resin is restored, and the molded body is formed into a molded body with high heat resistance.

[0108] In-mold forming is performed, for example, in the following manner. First, the foaming particles are filled into the forming mold. Next, steam is supplied into the forming mold to heat the foaming particles and fuse them. After the heating is completed, the pressure is released and water cooling is performed until the surface pressure caused by the foaming force of the molded body is reduced to a predetermined pressure (for example, 0.02 to 0.04 MPa (gauge pressure)), and then the mold is opened and the molded body is removed from the mold.

[0109] [molded body]

[0110] (thickness)

[0111] The polyamide resin foamed beads obtained by the production method disclosed herein have excellent moldability and are therefore suitable for forming thick (i.e., thick) molded bodies. Specifically, the thickness of the foamed bead molded body is preferably 30 mm or more, more preferably 35 mm or more.

[0112] (density)

[0113] From the viewpoint of further improving the lightness, the density of the molded body is preferably 40 to 200 kg / m 3 , more preferably 45 to 150 kg / m 3 , more preferably 50 to 120 kg / m 3 The density of the molded body is calculated by dividing the mass of the molded body by the outer dimensions and converting the unit to [kg / m 3 ] and find the answer.

[0114] (Welding rate)

[0115] From the viewpoint of further improving the appearance and mechanical properties of the molded body, the fusion rate of the molded body is preferably 90% or more. The method for measuring the fusion rate will be described later.

[0116] (Shrinkage after heating)

[0117] From the viewpoint of being able to more fully prevent shrinkage in a high temperature environment, the shrinkage after heating at a temperature of 160° C. for 20 days is preferably 3% or less, more preferably 1% or less, and further preferably 0.4% or less. The shrinkage of the molded body after heating can be adjusted to the above range by using an iodide-based additive (X) and an organic compound-based additive (A) in combination as described above. The method for measuring the shrinkage will be described later.

[0118] Example

[0119] Next, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to these Examples, and various modifications can be made without departing from the gist of the present invention.

[0120] [Example 1]

[0121] [Manufacturing of resin pellets]

[0122] 100 parts by mass of a polyamide resin, 0.2 parts by mass of a hindered phenol compound, 0.2 parts by mass of an organic phosphorus compound, 0.05 parts by mass of copper iodide, 0.2 parts by mass of potassium iodide, and 0.3 parts by mass of a bubble nucleating agent (specifically, talc) were fed into an extruder and melt-kneaded to obtain a melt-kneaded product. In addition, as the polyamide resin, "UBE Nylon 6434B" manufactured by Ube Industries, Ltd. was used, as the hindered phenol compound, N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide] ("Irganox 1098" manufactured by BASF Japan Co., Ltd.) was used, as the organic phosphorus compound, tris(2,4-di-tert-butylphenyl)phosphite ("Irgafos 168" manufactured by BASF Japan Co., Ltd.) was used, and as the bubble nucleating agent, talc ("Talcan Pawder KHP-125B" manufactured by Hayashi Kasei Co., Ltd.) was used.

[0123] The molten kneaded product was extruded from the fine hole of the die head installed at the front end of the extruder in the form of a strand with a circular cross section. The extruded strand was water-cooled, cut with a pelletizer so that the average mass of each strand was 2 mg, and dried to obtain granular resin pellets. The melting point of the resin pellets is 186°C.

[0124] In addition, the polyamide resin "6434B" is a polyamide 6 / 66 / 12 copolymer (nylon 6 / 66 / 12), melting point (Tm): 188°C, density 1.14 g / cm 3 , flexural modulus: 1070MPa, product name: UBE nylon 6434B.

[0125] [Manufacturing of Foamed Particles]

[0126] In a 5-liter autoclave equipped with a stirrer, 500 g of resin particles and 3.5 liters of water as a dispersion medium are added. Furthermore, 0.3 parts by mass of kaolin as a dispersant and 0.004 parts by mass of sodium alkylbenzene sulfonate as a surfactant are added to 100 parts by mass of the resin particles. While stirring the contents in the autoclave, the temperature is raised from room temperature (specifically, 23°C) to the immersion temperature (131.5°C), and carbon dioxide as a foaming agent is pressed into the autoclave until the pressure in the autoclave reaches the immersion pressure (4.0MPa(G)). At this time, the heating time from room temperature (23°C) to the immersion temperature (131.5°C) is 40 minutes. Then, it is kept at 131°C and 4.0MPa(G) for 15 minutes.

[0127] After that, the resin particles impregnated with the blowing agent were released together with the dispersion medium under atmospheric pressure (0.1 MPa), thereby foaming the resin particles to obtain foamed particles. The foaming temperature (the temperature of the dispersion liquid before foaming) was 131.5°C. Next, the foamed particles were cured in an oven at 60°C for 24 hours, and then slowly cooled to 23°C. The foamed particles thus obtained were used for the evaluation and production of the molded body described later.

[0128] [Manufacturing of Molded Body]

[0129] Specifically, after the forming mold is closed, the obtained expanded beads are filled into a flat plate forming mold of 200 mm in length×65 mm in width×40 mm in thickness, and in-mold forming is performed by steam heating to obtain a plate-shaped expanded mold.

[0130] The heating method is to supply steam for 5 seconds with the discharge valves of both sides of the mold open for preheating (exhaust process), then supply steam from the movable side mold with the discharge valve of the fixed side open, then supply steam from the fixed side mold with the discharge valve of the movable side open, close the exhaust valve, and heat to the molding heating steam pressure of 0.12MPa (molding pressure = molding steam pressure). After the heating is completed, the pressure is released, and water cooling is performed until the surface pressure caused by the foaming force of the molded body decreases to 0.02MPa (gauge pressure), and then the mold is opened and the molded body is taken out from the mold. After that, it is left to stand in an oven at 80°C and taken out after 24 hours to obtain a molded body.

[0131] <Evaluation of Foamed Particles>

[0132] The expanded beads were evaluated as follows. The results are shown in the table.

[0133] (Apparent density)

[0134] First, the 500 cm2 temperature was measured after being placed under the conditions of 50% relative humidity, 23°C, and 1 atm for 2 days. 3 Next, prepare a measuring cylinder filled with water at a temperature of 23°C, and use a metal mesh to sink the foamed particles whose mass has been measured into the measuring cylinder. Considering the volume of the metal mesh, measure the volume V1 of the foamed particles read from the water level rise [unit: cm 3 ], divide the mass W1[g] of the foamed particles by the volume V1 (W1 / V1) and convert the unit to [kg / m 3 ], and the apparent density of the foamed particles is calculated.

[0135] <Evaluation of Formability>

[0136] The evaluation of formability is performed by performing in-mold forming of the foamed particles while changing the forming pressure and evaluating the formable range. First, the forming pressure is changed by 0.02MPa at a time between 0.10 and 0.18 [MPa (G): gauge pressure], and in-mold forming is performed with a total of 4 forming pressures. Next, the weldability, recovery, and surface properties (central part of the formed body, corners of the formed body) of the formed body manufactured with each forming pressure are evaluated. The case where there are more than 2 forming pressures that can form a formed body that passes the above evaluation is evaluated as "A", the case where there is 1 forming pressure that can form a formed body that passes the above evaluation is evaluated as "B", and the case where there is no forming pressure that can form a formed body that passes the above evaluation is evaluated as "C".

[0137] (Weldability)

[0138] In order to evaluate the weldability of the formed body, the welding rate was measured, and the case where the welding rate was 80% or more was evaluated as "A (acceptable)", the case where the welding rate was 40% or more and less than 80% was evaluated as "B (unacceptable)", and the case where the welding rate was less than 40% was evaluated as "C (unacceptable)".

[0139] The fusion rate of the molded body is measured by the following method. A flat molded body is used as a test piece. On one side of its main surface (i.e., the surface with the largest area), a cut of about 10 mm in depth is made in the thickness direction at a position that divides the longitudinal length of the molded body into two equal parts using a cutting knife. The molded body is bent from the cut portion to break it. The ratio of the number m of foamed particles whose material is destroyed on the fracture surface to the number n of all foamed particles on the fracture surface (m / n×100[%]) is calculated, i.e., the material destruction rate. In addition, in the case where the molded body cannot be broken even if it is bent, its fusion rate is 100%. The above measurement is carried out five times using different test pieces, and the respective material destruction rates are calculated, and they are arithmetic averaged as the fusion rate.

[0140] (Restoration)

[0141] After the formed body is left to stand for 24 hours in an environment with a temperature of 23°C and a relative humidity of 50%, the thickness of the central part of the main surface (i.e., the surface with the largest area) and the four corners of the main surface of the flat-plate-shaped formed body are measured respectively. When the ratio of the thickness of the central part to the thickest part of the four corners is 90% or more, it is evaluated as "A (qualified)", and when it is less than 90%, it is evaluated as "C (unqualified)".

[0142] (Surface)

[0143] Central

[0144] The central portion of the surface of the flat plate-shaped molded product (specifically, the central portion of each surface of the molded product) was visually observed, and the appearance was evaluated according to the following criteria.

[0145] A (Pass): The center of the surface is beautiful and has excellent appearance

[0146] B (Unacceptable): Voids (specifically, gaps between foamed particles) are visible in the center of the surface, and the appearance is poor

[0147] C (failure): Clearly observed voids (specifically, gaps between foamed particles) in the center of the surface, poor appearance

[0148] ·Corner

[0149] The corners of the surface of the flat-plate-shaped molded product (range from the corner of the molded product to a radius of 10 mm) were visually observed, and the appearance was evaluated according to the following criteria.

[0150] A (pass): The corners of the surface are beautiful and the appearance is excellent

[0151] B (Unacceptable): Gaps (specifically, gaps between foamed particles) are visible at the corners of the surface, and the appearance is poor.

[0152] C (failure): Clearly observed voids (specifically, gaps between foamed particles) at the corners of the surface, poor appearance

[0153] <Evaluation of Molded Body>

[0154] The expanded beads were evaluated as follows. The results are shown in the table.

[0155] (density)

[0156] Divide the mass of the molded body by its dimensions and convert the unit to [kg / m 3 ], and the density of the formed body is calculated accordingly.

[0157] (Molding shrinkage of molded body)

[0158] After the molded body is formed, the molded body is heated in a dryer at 160°C for 20 days. Thereafter, the dimensions of the molded body are measured, and the values ​​shown in the following formula when the lengths of the longitudinal, transverse, and thickness are respectively set to a', b', and c', and the lengths of the longitudinal, transverse, and thickness of the mold size (inner dimensions) are respectively set to a, b, and c are taken as the molding shrinkage (%) of the molded body. The smaller the value of the molding shrinkage of the molded body, the more the molding shrinkage is suppressed.

[0159] (Formula) Molding shrinkage (%) = [|(a-a') / a|+|(b-b') / b|+|(c-c') / c|]×100 / 3

[0160] [Example 2]

[0161] The same procedures as in Example 1 were performed except that the amount of the hindered phenol compound added was changed to 0.1 part by mass and the amount of the organic phosphorus compound added was changed to 0.1 part by mass based on 100 parts by mass of the base resin.

[0162] [Example 3]

[0163] The process was the same as in Example 1 except that 2.5 parts by mass of carbon black was further added to 100 parts by mass of the base resin during melt kneading.

[0164] [Example 4]

[0165] The same procedures as in Example 1 were repeated except that the amount of the organic phosphorus compound added was changed to 0.4 parts by mass based on 100 parts by mass of the base resin.

[0166] [Example 5]

[0167] The same procedures as in Example 1 were performed except that the amount of the hindered phenol compound added was changed to 0.4 parts by mass and the amount of the organic phosphorus compound added was changed to 0.4 parts by mass based on 100 parts by mass of the base resin.

[0168] [Example 6]

[0169] The same procedures as in Example 1 were performed except that the amount of the hindered phenol compound added was changed to 0.6 parts by mass and the amount of the organic phosphorus compound added was changed to 0.6 parts by mass based on 100 parts by mass of the base resin.

[0170] [Comparative Example 1]

[0171] The process was the same as in Example 1 except that the organic compound additive (A) (hindered phenol compound, organic phosphorus compound) and the iodide additive (X) (copper iodide, potassium iodide) were not supplied to the extruder during melt kneading.

[0172] [Comparative Example 2]

[0173] The process was the same as in Example 1 except that the organic compound additive (A) (hindered phenol compound, organic phosphorus compound) was not supplied to the extruder during melt kneading.

[0174] [Comparative Example 3]

[0175] The same procedures as in Example 1 were performed except that the iodide-based additive (X) (copper iodide, potassium iodide) was not supplied to the extruder during melt kneading.

[0176] [Comparative Example 4]

[0177] The same procedures as in Example 1 were followed except that the amount of the organic compound additive (A) (hindered phenol compound, organic phosphorus compound) added was reduced and the amount of the iodide additive (X) (copper iodide, potassium iodide) added was increased.

[0178] [Comparative Example 5]

[0179] The same procedures as in Example 1 were carried out except that the amount of the iodide-based additive (X) (copper iodide, potassium iodide) added was reduced.

[0180] [Comparative Example 6]

[0181] The same procedures as in Example 1 were carried out except that the amount of the organic compound additive (A) (hindered phenol compound, organic phosphorus compound) added was increased.

[0182]

[0183]

[0184]

[0185]

[0186]

[0187]

[0188] It can be understood from Tables 1 and 2 that the foamed particles of the examples are foamed at a high ratio, are lightweight, and have excellent moldability. In addition, the molded bodies of the examples have low density, are lightweight, have a small shrinkage after heating, and are excellent in heat resistance.

[0189] As can be understood from Tables 3 to 6, the molded bodies of the Examples have excellent surface properties and can be obtained within a wide range of molding pressures. In addition, the molded bodies of the Examples have excellent moldability even when the molding pressure conditions are low pressures. This is because, in the Examples, the organic compound additive (A) and the iodide additive (X) are added to the base resin at a predetermined ratio during melt kneading.

[0190] In addition, in this example, although a polyamide resin in which the functional groups at the ends of the molecular chains are not blocked (i.e., easily hydrolyzed) without using an end-blocking agent such as a carbodiimide compound is used, the moldability is also excellent. It is believed that this is because the organic compound additive (A) and the iodide additive (X) are used in a predetermined ratio as described above. It is believed that by using an end-blocking agent, hydrolysis is suppressed, and thus the moldability is further improved. In addition, regarding the density and shrinkage of the molded bodies in Tables 1 and 2, the molded bodies obtained with the lowest molding pressure among the molded bodies with all qualified evaluations in Tables 3 to 6 were used, and for the comparative examples in which all qualified molded bodies were not obtained, the molded bodies obtained with the best molding pressure with unqualified moldability were used.

[0191] In Comparative Example 1, since the organic compound-based additive (A) and the iodide-based additive (X) were not added, the heat resistance and moldability were poor.

[0192] In Comparative Example 2, although the iodide-based additive (X) was added, the organic compound-based additive (A) was not added, so the moldability was insufficient.

[0193] In Comparative Example 3, although the organic compound additive (A) was added, the iodide additive (X) was not added. Therefore, the heat resistance was poor and the moldability was also insufficient.

[0194] In Comparative Example 4, the amount of the organic compound additive (A) added was small, and the ratio of the amount of the organic compound additive (A) added to the amount of the iodide additive (X) added was too low. Therefore, the moldability was insufficient.

[0195] In Comparative Example 5, the amount of the iodide-based additive (X) added was small, and the ratio of the amount of the organic compound-based additive (A) added to the amount of the iodide-based additive (X) added was too high. Therefore, the heat resistance was poor and the moldability was insufficient.

[0196] In Comparative Example 6, the amount of the organic compound additive (A) added was large, and the ratio of the amount of the organic compound additive (A) added to the amount of the iodide additive (X) added was too high. Therefore, the moldability was insufficient.

[0197] Thus, during melt kneading, by adding an organic compound additive (A) composed of a hindered phenol compound and / or an organic phosphorus compound, and an iodide additive (X) composed of copper iodide, or copper iodide and potassium iodide to the base resin, and adjusting the amounts added, a polyamide resin foamed molded article having excellent heat resistance and lightness can be produced, and foamed particles having excellent moldability can be obtained.

Claims

1. A method for producing polyamide resin foamed particles, which is a method for producing polyamide resin foamed particles using polyamide resin as a base resin, wherein: The method for producing the polyamide resin foamed particles comprises: a step of preparing polyamide resin pellets obtained by granulating a polyamide resin melt obtained by melt-kneading the base resin, an organic compound additive (A) consisting of a hindered phenol compound and / or an organic phosphorus compound, and an iodide additive (X) consisting of copper iodide or copper iodide and potassium iodide; and a step of foaming the polyamide resin particles using a foaming agent to obtain polyamide resin foamed particles; The amount of the organic compound additive (A) added is 0.05 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the base resin. The ratio of the amount of the organic compound additive (A) added to the amount of the iodide additive (X) added is 0.3 or more and 7 or less.

2. The method for producing polyamide resin foamed particles according to claim 1, wherein: The ratio of the amount of the organic compound additive (A) added to the amount of the iodide additive (X) added is 1 or more and 4 or less.

3. The method for producing polyamide resin foamed particles according to claim 1 or 2, wherein: The polyamide resin melt contains the hindered phenol compound (A1) and the organophosphorus compound (A2) as the organic compound additive (A), and the ratio of the amount of the organophosphorus compound (A2) added to the amount of the hindered phenol compound (A1) added is 0.5 or more and 2 or less.

4. The method for producing polyamide resin foamed particles according to claim 1 or 2, wherein: The amount of the iodide-based additive (X) added is 0.1 parts by mass or more relative to 100 parts by mass of the base resin.

5. The method for producing polyamide resin foamed particles according to claim 1 or 2, wherein: The polyamide resin melt further contains carbon black, and the amount of the carbon black added is 0.5 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the base resin.

6. A method for producing a polyamide resin foamed molded body, wherein: The polyamide resin foamed particles produced by the production method according to claim 1 or 2 are subjected to in-mold molding.

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