Flame-retardant polyamide resin composition and molded article made thereof

Abstract

[Problem] To provide a flame-retardant polyamide resin composition that is suitable for a molded component having a thin-wall portion such as a hinge portion, that has excellent flame retardancy, and from which it is possible to mold a molded article having excellent bending durability at the hinge portion. [Solution] This flame-retardant polyamide resin composition is characterized by: containing a polyamide resin (A) and a melamine cyanurate (B) at a proportion of 97.5-93 parts by mass and 2.5-7 parts by mass, respectively; containing, with respect to a total of 100 parts by mass of said components (A) and (B), 0.01-2 parts by mass of a hypophosphorous acid metal salt (C), a lubricant (D), a phosphorus-based antioxidant (E), and a phenol-based antioxidant (F); and satisfying the requirements described in (i)-(iii). (i) 10 ≤ Terminal amino group concentration (eq / ton) of polyamide resin (A) ≤ 39 (ii) Melt flow rate (275°C, 1 kgf) ≥ 40 (iii) 236°C ≤ Temperature-lowered crystallization temperature (Tc2) ≤ 242°C

Description

[Technical Field]

[0001] The present invention relates to a non-halogen flame-retardant polyamide resin composition, more particularly to a non-halogen flame-retardant polyamide resin composition that has high flame retardancy and good toughness and is particularly suitable for molded articles having hinge portions. [Background technology]

[0002] Polyamide resins are used in various fields such as electrical and electronic components, automobile components, etc., taking advantage of their excellent mechanical properties, electrical properties, chemical resistance, etc. In these fields, when an unreinforced system and flame retardancy using a non-halogen flame retardant are required, melamine cyanurate is used as the flame retardant (e.g., Patent Documents 1 and 2). However, melamine cyanurate has drawbacks such as poor dispersibility in polyamide resins, which reduces the mechanical properties of the polyamide resins; bleeding when incorporated in large amounts; and susceptibility to thermal decomposition into melamine and cyanuric acid, which then sublimate, resulting in silver smearing on the surface of molded articles during molding due to the effects of the sublimated melamine and cyanuric acid, which can easily contaminate the surface of the mold.

[0003] In recent years, the level of requirements for electrical and electronic components, automotive parts, etc. has been increasing, and not only are flame retardancy at UL94 V-0 level required for parts with thin-walled sections such as hinges at a thickness of 0.4 mm, but molded products with hinges are also expected to have excellent bending durability in the hinge section. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 58-25379 [Patent Document 2] Special Publication No. 58-35541 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a flame-retardant polyamide resin composition that is suitable for molded parts having thin-walled portions such as hinge portions, and that not only has flame retardancy at the UL94 V-0 level at a thickness of 0.4 mm, but also enables the molding of molded articles having hinge portions that have excellent flexural durability at the hinge portion, particularly even in low-temperature environments and after annealing treatment. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0007] That is, the present invention has the following configuration. [1] A flame-retardant polyamide resin composition comprising 97.5 to 93 parts by mass of a polyamide resin (A) and 2.5 to 7 parts by mass of a melamine cyanurate (B), and further comprising 0.01 to 2 parts by mass of a metal hypophosphite (C), a lubricant (D), a phosphorus-based antioxidant (E), and a phenol-based antioxidant (F) relative to 100 parts by mass of the total of the components (A) and (B), and satisfying the requirements (A) to (C) below. (a) 10 ≦ terminal amino group concentration (eq / ton) of polyamide resin (A) ≦ 39 (b) Melt flow rate (275°C, 1kgf) ≥ 40 (c) 236℃ ≦ Cooling crystallization temperature (Tc2) ≦ 242℃ [2] A method for producing a flame-retardant polyamide resin composition, comprising a step of melt-kneading a polyamide resin (A), a melamine cyanurate (B), and a metal hypophosphite (C), wherein the proportions of the polyamide 66 resin (A1) are 45 to 75 mass%, the polyamide 6 resin (A2) are 10 to 40 mass%, and the amorphous polyamide resin (A3) is 0 to 8 mass%, based on the total amount of the polyamide resin (A). [3] The flame-retardant polyamide resin composition according to claim 1 or 2, further comprising 0.01 to 1 part by mass of a lubricant (D), 0.01 to 1 part by mass of a phosphorus-based antioxidant (E), and 0.01 to 1 part by mass of a hindered phenol-based antioxidant (F) relative to 100 parts by mass of the flame-retardant polyamide resin composition. [4] The flame-retardant polyamide resin composition according to any one of claims 1 to 3, wherein the phosphorus-based antioxidant (E) is a compound having a pentaerythritol diphosphite skeleton. [5] A flame-retardant polyamide resin composition for a hinge member according to any one of claims 1 to 4. [6] A molded article having a hinge portion, which is made of the flame-retardant polyamide resin composition according to any one of claims 1 to 4. [7] The molded product according to claim 5, wherein the molded product having the hinge portion is any one of a ferrite core cover, a cable tie, and an electrical wiring protection member. [Effects of the Invention]

[0008] The flame-retardant polyamide resin composition of the present invention not only has flame retardancy of UL94 V-0 level at a thickness of 0.4 mm, but also enables molding of molded articles having hinge portions with excellent bending durability at the hinge portions. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be specifically described below. The flame-retardant polyamide resin composition of the present invention contains 97.5 to 93 parts by mass of polyamide resin (A) and 2.5 to 7 parts by mass of melamine cyanurate (B), and also contains 0.01 to 2 parts by mass of a metal hypophosphite (C) per 100 parts by mass of the total of the components (A) and (B), and is a flame-retardant polyamide resin composition characterized by satisfying the requirements of (i) to (iii) below. (a) 10 ≦ terminal amino group concentration (eq / ton) of polyamide resin (A) ≦ 39 (b) Melt flow rate (275°C, 1kgf) ≥ 40 (c) 236℃ ≦ Cooling crystallization temperature (Tc2) ≦ 242℃

[0010] In the case of a mixture of multiple polyamide resins, the average terminal amino group concentration (eq / ton) in requirement (A) of the present invention is a value (average AEG) calculated from the terminal amino group concentration (eq / ton) of each resin and their blending ratio. Preferably, the average AEG is 10≦(average AEG)≦38, and more preferably, 10≦(average AEG)≦37. If the average AEG exceeds 39, the effect of retarding the crystallization rate due to the transamidation reaction is less likely to be promoted, and relaxation of the resin orientation in the vicinity of the mold is less likely to occur, making the hinge portion more susceptible to cracking.

[0011] The melt flow rate in requirement (ii) of the present invention is the melt fluidity (MFR) of the flame-retardant polyamide resin composition of the present invention according to the ISO 1133 method, and is preferably at least 50, more preferably at least 60. If the melt fluidity (MFR) is lower than requirement (ii) of the present invention, resin orientation occurs near the mold, making the hinge portion more susceptible to cracking.

[0012] The cooling crystallization temperature (Tc2) in requirement (c) of the present invention is a temperature measured by heat flux differential scanning calorimetry (heat flux DSC), and preferably satisfies the condition 238°C ≦ (Tc2) ≦ 241°C. If (Tc2) exceeds 242°C, relaxation of the resin orientation in the vicinity of the mold is difficult, and cracks are likely to occur in the hinge portion. If it is less than 236°C, moldability tends to be poor.

[0013] The various raw materials used in the present invention will be further described in detail below. [Polyamide resin (A)] The polyamide resin (A) in the present invention is not particularly limited as long as it is a polymer having an amide bond (-NHCO-) ​​in the main chain. The polyamide resin (A) is preferably crystalline, and examples thereof include polyamide 6 (PA6), polyamide 66 (PA66), polyamide 46 (PA46), polyamide 11 (PA11), polyamide 12 (PA12), polyamide 610 (PA610), polyamide 612 (PA612), polymetaxylylene adipamide (PAMXD6), hexamethylenediamine-terephthalic acid polymer (PA6T), hexamethylenediamine-terephthalic acid and adipic acid polymer (PA6T / 66), hexamethylenediamine-terephthalic acid and ε Examples include, but are not limited to, crystalline polyamide resins such as caprolactam copolymer (PA6T / 6), trimethylhexamethylenediamine-terephthalic acid polymer (PATMD-T), metaxylylenediamine, adipic acid, and isophthalic acid copolymer (PAMXD6 / MXDI), trihexamethylenediamine, terephthalic acid, and ε-caprolactam copolymer (PATMDT / 6), and diaminodicyclohexylenemethane, isophthalic acid, and lauryllactam copolymer, or blends thereof.

[0014] The blending amount (content) of the polyamide resin (A) is 97.5 to 94 parts by mass when the total of the polyamide resin (A) and the melamine cyanurate (B) is 100 parts by mass. When the blending amount of the polyamide resin (A) is within this range, bleeding of the flame retardant can be suppressed and high flame retardancy can be maintained in the composition. The blending amount (content) of the polyamide resin (A) is preferably 97 to 94.5 parts by mass, more preferably 97 to 95 parts by mass. In the flame-retardant polyamide resin composition of the present invention, the blending amount of each component directly corresponds to the content.

[0015] The flame-retardant polyamide resin composition of the present invention can be obtained by a production method including a step of melt-kneading a polyamide resin (A), a melamine cyanurate (B), and a metal hypophosphite (C). The polyamide resin (A) is preferably mixed in an amount of 45 to 75 mass% of a polyamide 66 resin (A1), 10 to 40 mass% of a polyamide 6 resin (A2), and 0 to 8 mass% of an amorphous polyamide resin (A3) based on the total amount of the polyamide resin (A).

[0016] The polyamide 66 resin (A1) in the present invention may be a polyamide 66 resin obtained by polycondensation of adipic acid and hexamethylenediamine as raw materials. The relative viscosity of the polyamide 66 resin (A1) is preferably 2.2 to 3.5, as measured in accordance with JIS K6810 at a concentration of 1% in 98% sulfuric acid at a temperature of 25°C. If the relative viscosity is less than 2.2, the mechanical properties tend to deteriorate, and if it exceeds 3.5, the melt fluidity tends to be insufficient. The relative viscosity of the polyamide 66 resin (A1) is more preferably 2.3 to 3.0.

[0017] The terminal amino group concentration of the polyamide 66 resin (A1) is preferably 10 to 50 eq / ton, and more preferably 10 to 40 eq / ton in terms of hinge durability and heat discoloration resistance.

[0018] The blending amount of polyamide 66 resin (A1) is preferably 45 to 75 parts by mass, and more preferably 50 to 70 parts by mass, from the viewpoint of hinge durability, when the total amount of polyamide resin is 100 parts by mass. If the blending amount of polyamide 66 resin (A1) exceeds 75 parts by mass, hinge performance (snap-fit ​​performance) decreases, and if it is less than 45 parts by mass, moldability tends to decrease.

[0019] The polyamide 6 resin (A2) in the present invention is a polyamide 6 resin obtained by polycondensation using ε-caprolactam as a raw material. The relative viscosity of the polyamide 6 resin (A2) is preferably 2.0 to 4.0, as measured in 98% sulfuric acid at a concentration of 1% and a temperature of 25°C according to JIS K6810. If the relative viscosity is less than 2.0, mechanical properties tend to deteriorate, and if it exceeds 4.0, flame retardancy tends to be impaired. The relative viscosity of the polyamide 6 resin (A2) is more preferably 2.2 to 3.0.

[0020] The terminal amino group concentration of the polyamide 6 resin (A2) is preferably 5 to 50 eq / ton, and more preferably 10 to 40 eq / ton in terms of the bending durability and heat discoloration resistance of the hinge portion.

[0021] The blending amount of polyamide 6 resin (A2) is preferably 10 to 40 parts by mass when the total amount of polyamide resins is 100 parts by mass. If the blending amount of polyamide 6 resin (A2) is less than 10 parts by mass, the hinge property (snap-fit ​​property) is likely to decrease, and if it exceeds 40 parts by mass, the moldability is likely to decrease. The blending amount of polyamide 6 resin (A2) is more preferably 20 to 40 parts by mass from the viewpoint of the balance between the snap-fit ​​property and the moldability.

[0022] Examples of the amorphous polyamide resin (A3) include those in which no crystalline melting peak is observed in the thermogram measured by DSC, and include polymers, copolymers, or blends obtained by polycondensation of diamines such as 4,4'-diamino-3,3'-dimethyldicyclohexylmethane (CA), 4,4'-diaminodicyclohexylmethane (PACM), metaxylylenediamine (MXD), trimethylhexamethylenediamine (TMD), isophoronediamine (IA), 4,4'-diaminodicyclohexylpropane (PACP), and hexamethylenediamine with dicarboxylic acids such as terphthalic acid, isophthalic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid, and lactams such as caprolactam and lauryllactam.

[0023] Among these, polyamide resins containing aromatic components are preferred because they lower Tc2 and make it easier to prevent cracking at the hinge portion. Preferred polyamide resins containing aromatic components include polyamide 6T / 6I, which is made from terephthalic acid, isophthalic acid, and adipic acid, and polyamide 6T / 66, which is made from terephthalic acid, adipic acid, and hexamethylenediamine, with polyamide 6T / 6I being particularly preferred in terms of moldability.

[0024] [Melamine cyanurate (B)] The melamine cyanurate (B) in the present invention is preferably an equimolar reaction product of cyanuric acid and melamine. Furthermore, some of the amino groups or hydroxyl groups in the melamine cyanurate may be substituted with other substituents. Melamine cyanurate can be obtained, for example, by mixing an aqueous solution of cyanuric acid with an aqueous solution of melamine, reacting them under stirring at 90 to 100°C, and filtering the resulting precipitate. The resulting solid can be used as is, but it is preferably pulverized as needed before use. The particle size is not particularly limited, but from the viewpoints of flame retardancy and toughness, the average particle size is preferably 0.5 to 20 μm, more preferably 1 to 15 μm.

[0025] The blending amount (content) of the melamine cyanurate (B) is 2.5 to 7 parts by mass when the total of the polyamide resin (A) and the melamine cyanurate (B) is 100 parts by mass. From the viewpoint of flame retardancy, it is 2.5 parts by mass or more, and from the viewpoint of toughness, it is 7 parts by mass or less. It is more preferably 2.5 to 6 parts by mass, and even more preferably 3 to 5 parts by mass. In the present invention, toughness is a property related to snap-fit ​​properties.

[0026] [Metal hypophosphites (C)] The metal hypophosphite (C) in the present invention is a salt of hypophosphorous acid with an element of Groups 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, or 13 of the Periodic Table, or a metal such as tin or lead, and may be used alone or in combination of two or more. Among these, sodium hypophosphite (NaH2PO2) and calcium hypophosphite (Ca(H2PO2)2) are preferred, from the viewpoint of achieving a more significant effect of promoting the delay in the crystallization rate through an amide exchange reaction, which leads to improved flexural durability of the hinge portion. The metal hypophosphite may be a hydrate, such as sodium hypophosphite monohydrate (NaH2PO2 H2O).

[0027] The amount of the metal hypophosphite (C) is 0.001 to 2 parts by mass, preferably 0.05 to 1.5 parts by mass, and more preferably 0.1 to 1.0 part by mass, per 100 parts by mass of the total of the polyamide resin (A) and the melamine cyanurate (B). The presence of the metal hypophosphite within a specific range promotes the transamidation reaction between polyamide resins, which is preferable for stabilizing the resin properties.

[0028] The resin composition of the present invention preferably contains a lubricant (D), a phosphorus-based antioxidant (E), a hindered phenol-based antioxidant (F), etc. in order to improve moldability, discoloration resistance, thermal stability, etc.

[0029] [Lubricant (D)] Examples of the lubricant (D) in the present invention include esters and metal salts of long-chain fatty acids, amide compounds such as ethylene bisterephthalamide and methylene bisstearylamide, waxes such as aliphatic hydrocarbons and polyethylene waxes, and polysiloxane silicone oils. These lubricants may be used alone or in combination. The amount of lubricant added may be selected optimally in consideration of moldability and flame retardancy, but fatty acid metal salt-based and fatty acid ester-based lubricants are preferred in terms of the balance between moldability and flame retardancy.

[0030] Examples of fatty acid metal salts include metal salts of fatty acids having 12 to 40 carbon atoms, such as stearic acid, palmitic acid, behenic acid, erucic acid, oleic acid, lauric acid, and montanic acid. Among these, metal salts of aliphatic carboxylic acids having 18 to 30 carbon atoms are preferred, and alkali metal or alkaline earth metal salts of stearic acid, behenic acid, lignoceric acid, and montanic acid are more preferred in terms of releasability. Examples of alkali metal or alkaline earth metal salts include lithium, sodium, magnesium, and calcium salts.

[0031] Examples of fatty acid ester compounds include mixtures containing myricyl palmitate as a main component, stearyl stearate, behenyl behenate, stearyl behenate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, and pentaerythritol tetrastearate.

[0032] The blending amount (content) of the lubricant (D) is 0.01 to 1 part by mass relative to 100 parts by mass of the polyamide resin composition. If it is less than 0.01 part by mass, the mold releasability may decrease, and if it exceeds 1 part by mass, the flame retardancy may decrease. The blending amount of the lubricant (D) is preferably 0.1 to 0.9 parts by mass.

[0033] [Phosphorus-based antioxidant (E)] The phosphorus-based antioxidant (E) in the present invention may be an inorganic compound or an organic compound, and is not particularly limited. Preferred phosphorus-based compounds include inorganic phosphates such as monosodium phosphate, disodium phosphate, trisodium phosphate, sodium phosphite, calcium phosphite, magnesium phosphite, and manganese phosphite, triphenyl phosphite, trioctadecyl phosphite, tridecyl phosphite, triisodecyl phosphite, trinonylphenyl phosphite, diphenylisodecyl phosphite, diphenyl alkyl phosphite, phenyl dialkyl phosphite, tris(nonylphenyl) phosphite, trilauryl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, di Isodecyloxypentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tris(tert-butylphenyl))pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite, 6-isooctyloxy-2,4,8,10-tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite Examples include tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphocin, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenzo[d,g]-1,3,2-dioxaphosphocin, bis(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite, and bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite, which are added to improve resistance to heat discoloration.

[0034] The phosphorus-based antioxidant (E) is preferably a phosphite compound, and among the phosphite compounds, a compound having a pentaerythritol diphosphite skeleton is preferred. Specifically, those having a pentaerythritol diphosphite skeleton and a molecular weight of about 600 to 800, such as bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite ("ADK STAB PEP-36", molecular weight 633), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite ("ADK STAB PEP-24G", molecular weight 604), distearyl pentaerythritol diphosphite ("ADK STAB PEP-8", molecular weight 733), and bis(nonylphenyl)pentaerythritol diphosphite ("ADK STAB PEP-4C", molecular weight 633), are particularly preferred because they can further improve mold releasability without reducing flame retardancy and are also suitable for snap-fit ​​properties.

[0035] The blending amount (content) of the phosphorus-based antioxidant (E) is 0.01 to 1 part by mass per 100 parts by mass of the flame-retardant polyamide resin composition. When the blending amount of the phosphorus-based antioxidant (E) is within this range, discoloration during extrusion processing can be suppressed and secondary oxidative degradation due to phosphorus-derived radicals can be prevented. The blending amount of the phosphorus-based antioxidant (E) is preferably 0.1 to 0.5 parts by mass.

[0036] [Hindered phenolic antioxidant (F)] Examples of the hindered phenol-based antioxidant (F) in the present invention include N,N'-hexamethylene-bis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, bis(3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)butanoic acid) glycol ester, 2,1'-thioethyl bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), triethylene glycol-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate "SONGNOX2450", molecular weight 633), and mixtures of two or more of these can also be used.

[0037] The amount (content) of the hindered phenol-based antioxidant (F) is 0.01 to 1 part by mass per 100 parts by mass of the flame-retardant polyamide resin composition. When the amount of the hindered phenol-based antioxidant (F) is within this range, it is possible to prevent oxidative deterioration over time with an appropriate amount depending on the coordinate bond of the polyamide composition. The amount of the hindered phenol-based antioxidant (F) is preferably 0.1 to 0.5 parts by mass.

[0038] [Other ingredients] In addition to the above-mentioned (A), (B), (C), (D), (E), and (F), other components, such as colorants such as pigments and dyes, additives such as heat stabilizers, weather resistance improvers, nucleating agents, plasticizers, mold release agents, and antistatic agents, other resin polymers, etc., may be added to the flame-retardant polyamide resin composition of the present invention, provided that the objects of the present invention are not impaired. The total amount of the above-mentioned (A), (B), (C), (D), (E), and (F) components preferably accounts for 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, of the flame-retardant polyamide resin composition of the present invention.

[0039] Suitable molded parts obtainable using the flame-retardant polyamide resin composition of the present invention are molded articles having hinge portions, specifically molded parts having thin hinge portions such as connectors, coil bobbins, breakers, electromagnetic switches, holders, plugs, sockets, switches, cases, and covers used in the fields of electric and electronic parts, automobile parts, etc., and more specifically parts requiring heat discoloration resistance and snap fit properties such as ferrite core covers, cable ties, and electrical wiring protection members.

[0040] The method for producing the flame-retardant polyamide resin composition of the present invention is not particularly limited, and a general single-screw extruder, twin-screw extruder, pressure kneader, etc. can be used as a kneading device, but a twin-screw extruder is particularly preferred in the present invention. In one embodiment, the above-mentioned (A), (B), (C), (D), (E), and (F), and, depending on the application, a pigment, etc., are mixed and charged into a twin-screw extruder. By uniformly kneading using a twin-screw extruder, a polyamide-based resin composition with excellent toughness and flame retardancy can be produced. The kneading temperature of the twin-screw extruder is preferably 220 to 300°C, and the kneading time is preferably about 2 to 15 minutes. [Example]

[0041] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0042] The following components were used: Polyamide resin (A); A1-1: Polyamide 66 (RV=2.8) Vydyne 21FSR (manufactured by Ascend), melting point 265°C A1-2: Polyamide 66 (RV=2.4) EPR24 (manufactured by Shanghai Shenma Plastic Technology Co., Ltd.), melting point 265℃ A2-1: Polyamide 6 (RV=2.0) M2000 (manufactured by MEIDA), melting point 225°C A2-2: Polyamide 6 (RV=2.6) ZISAMIDE TP4208 (manufactured by Shuseisha), melting point 225°C A2-3: Polyamide 6 (RV=3.6) ZISAMIDE TP6603 (manufactured by Shuseisha), melting point 225°C A3: Polyamide 6T / 6I (RV=1.9) Grivory® G16 (manufactured by EMS Co., Ltd.) Glass transition temperature 130°C

[0043] Melamine cyanurate (B); B: MC6000 (Nissan Chemical Co., Ltd.)

[0044] Metal hypophosphites (C); C: Sodium hypophosphite (manufactured by Taihei Chemical Industry Co., Ltd.)

[0045] Lubricants (D); D1: Calcium montanate CS-8-CP (manufactured by Nitto Kasei Kogyo Co., Ltd.) Other release agents; D2: Fatty acid ester Ricorb WE-40 (Clariant Japan Co., Ltd.)

[0046] Phosphorus-based antioxidant (E); E: ADK STAB PEP-36 (ADEKA Corporation)

[0047] hindered phenolic antioxidant (F); F: SONGNOX2450 (Songwon International Japan)

[0048] [Examples 1 to 6, Comparative Examples 1 to 4] Production of evaluation samples The raw materials were weighed to obtain the polyamide resin composition in the proportions shown in Table 1, mixed in a tumbler, and then fed into a twin-screw extruder to obtain pellets of the polyamide resin composition. The twin-screw extruder was set at a temperature of 250°C to 300°C, and the kneading time was 5 to 10 minutes. The obtained pellets were molded into various evaluation samples using an injection molding machine. The cylinder temperature of the injection molding machine was set at 250°C to 280°C, and the mold temperature was set at 80°C.

[0049] The various evaluation methods are as follows: The evaluation results are shown in Table 1. 1. Relative viscosity [RV] of polyamide resin (98% sulfuric acid solution method) Using an Ubbelohde viscosity tube, measurements were made at 25°C in a 98% by mass sulfuric acid solution with a polyamide resin concentration of 1 g / dL. 2. Terminal amino group concentration (AEG) of polyamide resin The sample was dissolved in deuterated benzene / HFIP-d (1 / 1:volume ratio) (temperature: 35°C, 1 hour), centrifuged, and 0.2M triethylamine / CDCl3 (CDCl3 containing 0.2M triethylamine) was added to the supernatant. 1 The H-NMR measurement was performed. The sample was cut out from the center of a 100mm x 100mm x 3mm resin plate fabricated by injection molding at a molding temperature of 270°C and a mold temperature of 80°C. 1 From the H-NMR analysis, the amount of amino groups was calculated from the CH2 peak intensity at the α-position of the amino groups based on the weight of the polyamide resin. Here, HFIP is hexafluoro-2-propanol. [NMR measurement] Equipment: Fourier transform nuclear magnetic resonance spectrometer (BRUKER AVANCE-NEO) 1H resonance frequency: 600.13MHz Detection pulse flip angle: 45° Data acquisition time: 4 seconds Delay time: 1 second 3. Cooling crystallization temperature (Tc2) Using a differential scanning calorimeter (EXSTAR 6000, manufactured by Seiko Instruments Inc.), the temperature was raised to 305°C at a rate of 20°C / min under a nitrogen stream, held for 5 minutes, and then measured at a rate of 10°C / min to determine the exothermic peak temperature of the polyamide resin composition during cooling, which was designated as the cooling crystallization temperature (Tc2). 4.Melt flow rate The melt flow rate (MFR: g / 10 min) was measured at a temperature of 275° C. and a load of 1000 g in accordance with the test method (Method A) described in ISO 1133. For the measurement, a polyamide resin composition with a moisture content of 0.1 mass % or less was used. 5. Hinge durability Twenty molded articles with hinges obtained by injection molding were left in a 5°C environment for 15 minutes, and then the hinges were bent once in that environment, and the number of cases in which cracks or breaks occurred in the hinges was defined as "hinge cracks (5°C)" and tallied. Additionally, molded articles were left in an 85°C oven for at least six hours after molding, and then similarly left in a 5°C environment for 15 minutes. The number of cases in which cracks or breaks occurred in the hinges when the hinges were bent once in that environment was defined as "hinge cracks (85°C annealed 5°C)" and tallied. 6. Flammability Measured according to UL94 vertical flame test. V-0 indicates the highest flame retardancy.

[0050] [Table 1]

[0051] In all of Examples 1 to 6, the number of cracks at the hinge portion (5°C) and at the hinge portion (annealed at 85°C and 5°C) was two or less, demonstrating good hinge durability. In terms of flame retardancy at a thickness of 0.4 mm, Examples 1 to 6 also achieved a V-0 rating. It was also confirmed that the Tc2 and melt flow rate of the polyamide resin composition satisfied the requirements. Furthermore, when Examples 1 to 6, which used a metal hypophosphite (C), were compared with Comparative Example 4, which used only a phosphorus compound (only a phosphorus-based antioxidant), it was found that the former had superior hinge durability.

[0052] On the other hand, although Comparative Examples 1 to 4 partially satisfy the properties, none of them achieves good hinge durability. Comparative Examples 1 and 2 do not satisfy the melt flow rate requirement, which leads to resin orientation near the mold and makes the hinge portion prone to cracking, making them undesirable. In addition, Comparative Example 2 has a terminal amino group concentration (eq / ton) of polyamide resin (A) that exceeds the upper limit of the requirement, making it difficult to promote the crystallization rate retardation effect due to the transamidation reaction, making it undesirable. Comparative Example 3 does not satisfy the Tc2 requirement of the composition, which makes it difficult to relax the resin orientation near the mold and makes the hinge portion prone to cracking, making it undesirable. Finally, Comparative Example 4 does not satisfy the content ratio requirement of the composition, which makes it difficult to relax the resin orientation near the mold and makes the hinge portion prone to cracking, making it undesirable. In addition, the flammability rating is V-2, meaning that flame retardancy cannot be ensured, making it undesirable. [Industrial Applicability]

[0053] The flame-retardant polyamide resin composition of the present invention is suitable for molded articles having hinge portions, and the obtained molded articles can be suitably used for electrical and electronic parts, automobile parts, and the like, in which excellent flexural durability of the hinge portion is desired.

Claims

1. A flame-retardant polyamide resin composition containing 97.5 to 93 parts by mass of polyamide resin (A) and 2.5 to 7 parts by mass of melamine cyanurate (B), and containing 0.01 to 2 parts by mass of a metal hypophosphite (C) per 100 parts by mass of the total of components (A) and (B), wherein the polyamide resin (A) satisfies the following requirement (A), and the flame-retardant polyamide resin composition satisfies the following requirements (B) and (C). (A) 10≦Concentration of terminal amino groups (eq / ton) of polyamide resin (A)≦39 (b) Melt flow rate (275°C, 1 kgf) ≧ 40 (c) 236°C ≦ Cooling crystallization temperature (Tc2) ≦ 242°C

2. A flame-retardant polyamide resin composition as described in claim 1, wherein the proportions of polyamide 66 resin (A1) are 45 to 75 mass %, polyamide 6 resin (A2) are 10 to 40 mass %, and amorphous polyamide resin (A3) are 0 to 8 mass %, relative to the total amount of polyamide resin (A).

3. 2. The flame-retardant polyamide resin composition according to claim 1, further comprising 0.01 to 1 part by mass of a lubricant (D), 0.01 to 1 part by mass of a phosphorus-based antioxidant (E), and 0.01 to 1 part by mass of a hindered phenol-based antioxidant (F) relative to 100 parts by mass of the flame-retardant polyamide resin composition.

4. 4. The flame-retardant polyamide resin composition according to claim 3, wherein the phosphorus-based antioxidant (E) is a compound having a pentaerythritol diphosphite skeleton.

5. The flame-retardant polyamide resin composition for hinge members according to any one of claims 1 to 4.

6. A molded article having a hinge portion, comprising the flame-retardant polyamide resin composition according to any one of claims 1 to 4.

7. 7. The molded product according to claim 6, wherein the molded product having the hinge portion is any one of a ferrite core cover, a cable tie, and an electric wiring protection member.

8. A method for producing a flame-retardant polyamide resin composition according to any one of claims 1 to 4, comprising a step of melt-kneading polyamide resin (A), melamine cyanurate (B), and metal hypophosphite (C).

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