High-heat-stable antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic and preparation method thereof

Abstract

This invention discloses a high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic and its preparation method. The engineering plastic is a polyamide composition, consisting of the following raw materials by weight percentage: 25.5-89.97% polyamide resin, 10-35% filler, 0.01-25% flame retardant, 0.01-10% synergistic flame retardant, 0.01-1.5% antioxidant, 0-2% processing aid, and 0-1% masterbatch. The polyamide composition of this invention achieves a UL94 V-0 flame retardant rating. Furthermore, the halogen-free synergistic flame retardant effectively neutralizes the environmental shortcomings of bromine-based flame retardants, completely avoiding the negative impact of traditional antimony-halogen flame retardants on the electrical properties of the material. The system also exhibits lower ecotoxicity. The resulting flame-retardant polyamide material possesses low ecotoxicity, high flame retardancy, and excellent mechanical properties, making it widely applicable in high-performance fields such as automotive parts and electronic appliance housings.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and in particular to high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastics and their preparation methods. Background Technology

[0002] Halogenated flame-retardant nylon materials significantly improve flame-retardant efficiency by adding bromine- or chlorine-based flame retardants to the nylon matrix. Small amounts can achieve the UL94 V-0 standard, effectively interrupting the combustion chain reaction and forming a char layer to isolate oxygen. Its performance characteristics include excellent mechanical strength, dimensional stability, and heat resistance, while maintaining high electrical insulation and processing fluidity, making it suitable for injection molding of thin-walled and complex structures. However, this material releases toxic and corrosive gases such as hydrogen halides and dense smoke during combustion, posing environmental and health risks. It also exhibits poor weather resistance and light stability. Applications are concentrated in scenarios with high safety requirements, such as electronics, automotive manufacturing, and home appliances, meeting the demands for lightweighting, cost-effectiveness, and fire safety regulations. Although environmental trends are driving halogen-free alternatives, halogenated systems still hold an important position during the transition period due to their high flame-retardant efficiency.

[0003] Antimony trioxide (Sb₂O₃), as a key synergist in brominated flame-retardant nylon, significantly improves flame-retardant efficiency through a bromine-antimony synergistic mechanism: at high temperatures, the HBr released by the brominated flame retardant reacts with Sb₂O₃ to generate gaseous antimony halide. On the one hand, it captures active free radicals (HO·) from the combustion chain reaction in the gas phase, interrupting flame propagation; on the other hand, it melts and covers the material surface to form a dense char layer, isolating oxygen and inhibiting heat conduction, allowing nylon to achieve the UL94 V-0 standard with a low addition amount, while maintaining mechanical properties and processing fluidity. However, its application has significant limitations: combustion releases toxic gases such as hydrogen halides and dioxins, as well as dense smoke, causing secondary environmental and health hazards; antimony is a strategic non-renewable resource, and the strict control of heavy metal antimony by the EU RoHS / WEEE directives promotes halogen-free alternatives; high-temperature processing easily causes yellowing and carbonization of nylon, affecting the appearance and performance stability of products, necessitating the development of environmentally friendly antimony substitutes or optimized flame-retardant technologies.

[0004] Chinese patent CN201710540503.1 discloses a method for preparing a UV-resistant flame-retardant nylon composite material. By using brominated epoxy resin and zinc stannate flame-retardant nylon, and adding UV absorbers and light stabilizers, the resulting modified nylon composite material possesses flame-retardant, UV-resistant, and antimony-free properties, making it suitable for manufacturing automotive and electronic components requiring weather resistance. Chinese patent CN202510182344.7 relates to an antimony-free high glow wire temperature flame-retardant nylon material, its preparation method, and applications. It uses a phosphorus-based flame retardant instead of antimony trioxide, achieving synergistic flame retardancy with bromine, reaching UL94V-0 and achieving a high glow wire temperature (GWIT) of 850℃, while preventing whitening at the glue joints of black parts. Chinese patent CN202511331900.9 provides an antimony-free halogenated flame-retardant polyamide composite material. By synergistically replacing the traditional bromine-antimony flame-retardant system with organic phosphonates and zirconium compounds, the prepared polyamide composite material has excellent mechanical properties, flame-retardant properties and excellent thermal decomposition stability.

[0005] It is evident that current research has explored replacing antimony trioxide with flame retardants such as organophosphorus compounds, zirconium compounds, or zinc stannate in halogenated flame-retardant nylon materials. However, most studies focus on single-component modifications or increased addition amounts to enhance flame retardancy, often resulting in a sacrifice of flame retardant efficiency and mechanical properties. Therefore, developing a low-addition, highly efficient, and synergistic antimony-free bromide-based flame-retardant nylon system is of significant strategic importance for overcoming technological bottlenecks, mitigating the environmental and health risks associated with antimony, and improving the overall performance of the material. Summary of the Invention

[0006] To overcome existing technological bottlenecks and fill gaps in related fields, this invention proposes an antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic and its preparation method. This technology successfully constructs an antimony-free bromine-phosphorus flame-retardant polyamide system with both low addition amounts and high-efficiency synergistic flame-retardant properties through the precise design of a ternary synergistic mechanism involving flame retardants, synergists, and antioxidants. The introduced antioxidant system significantly improves the material's heat resistance. This material not only stably meets the UL94 V-0 flame retardant standard, effectively avoiding the environmental and health risks of traditional antimony-based flame retardants, but also achieves significant improvements in key indicators such as mechanical and electrical properties, providing an innovative path for the green and high-performance development of flame-retardant polyamide materials.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic, which is composed of the following raw materials by weight percentage:

[0009] Polyamide resin 25.5-89.97%;

[0010] Filler 10-35%;

[0011] Flame retardant 0.01-25%;

[0012] Synergistic flame retardant 0.01-10%;

[0013] Antioxidant 0.01-1.5%;

[0014] Processing aids 0-2%;

[0015] Masterbatch 0-1%.

[0016] Further, the polyamide resin may be selected from one or more of PA6, PA56, PA66, PA6 / 66, PA66 / 6, PA66 / 6T, PA6T / X, PA9T, PA10T, PA10T / X, PA46, PA4T, PA5T, and PA5T / X.

[0017] Furthermore, the filler is classified into two types according to its morphology: fibrous and non-fibrous. The fibrous filler can be selected from one or more of glass fiber, carbon fiber, aramid fiber, and basalt fiber, while the non-fibrous filler can be selected from one or more of whiskers, mica, kaolin, talc, glass microspheres, calcium carbonate, and wollastonite. This invention preferably uses glass fiber as the filler, with an alkali content <0.8%, a bulk density of 0.6-0.8 g / cm³, a monofilament fiber diameter of 7-13 μm, a chopped length of 2-5 mm, and a moisture content ≤0.05%.

[0018] Furthermore, the flame retardant is a composition of brominated flame retardant A and brominated flame retardant B, wherein the weight ratio of brominated flame retardant A to brominated flame retardant B is 2:1 to 4:1, brominated flame retardant A is selected from brominated polystyrene, and brominated flame retardant B is selected from ethylene bis(tetrabromophthalimide).

[0019] Furthermore, the synergistic flame retardant is a combination of polydimethylsiloxane PEG-7 phosphate and 1,3-dimethylimidazolium dinitrile amine salt, with a weight ratio of 3:1 to 4:1.

[0020] Furthermore, the antioxidant is a combination of bispentaerythritol hexabromotoluenesulfonic acid and 4,4'-(naphthalene-1,5-diyl)diphenylamine, with a weight ratio of 5:1 to 6.5:1.

[0021] Furthermore, the processing aid is selected from at least one of silicone powder, silicone masterbatch, pentaerythritol stearate (PETS), montan wax, polyethylene wax, oxidized polyethylene wax, and calcium stearate, which has both internal and external lubrication functions and does not affect the flame retardant properties; wherein the silicone powder is compounded from phenyl silicone and silicon dioxide in a 1:1 weight ratio.

[0022] Furthermore, the carbon black content of the masterbatch is 10%-99%, and the carrier is selected from polyamide 6 (PA6) or lubricant.

[0023] Secondly, the present invention provides a method for preparing the above-mentioned high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic, comprising the following steps:

[0024] (1) Control the moisture content of polyamide resin to ≤2000ppm;

[0025] (2) Weigh the dried polyamide resin, flame retardant, synergistic flame retardant, antioxidant, processing aid and color masterbatch according to the formula, and mix them by high-speed stirring to obtain a premix; weigh the filler at the same time for later use;

[0026] (3) The premixed material is added through the main feed port of the twin-screw extruder, and the filler is added through the side feed port. The polyamide engineering plastic is obtained by melt extrusion at 260℃±10℃-granulation-drying.

[0027] Thirdly, the present invention provides the application of the above-mentioned high thermal stability antimony-free bromine-phosphorus flame-retardant polyamide engineering plastic in the fields of automotive parts and electronic and electrical housings.

[0028] The core advantage of this invention lies in constructing a novel flame-retardant system: by compounding two bromine-based flame retardants with a decomposition temperature difference ≥50℃, the complementary thermal behaviors simultaneously achieve synergistic effects of gas-phase free radical quenching and condensed-phase physical barrier; the silicon-based synergist migrates to the material surface during combustion to form a dense Si-O-Si / Si-C cross-linked char layer; the ionic liquid synergist catalyzes the formation of an expanded char layer, isolating heat and oxygen transfer; the two work together through a dual pathway of condensed-phase flame retardancy and physical barrier to produce multiphase synergy with the bromine-based system, significantly improving flame-retardant efficiency. In addition to thermo-oxidative aging protection, the specific antioxidant also possesses the triple functions of condensed-phase char formation catalysis, gas-phase free radical capture, and endothermic decomposition, enabling the composition to achieve UL94 V-0 rating (1.6mm thickness). The system does not contain heavy metals such as antimony, overcoming the environmental and electrical performance deficiencies of traditional halogen flame-retardant systems.

[0029] The beneficial effects of this invention are:

[0030] 1) This invention innovatively employs two bromine-based flame retardants with complementary thermal decomposition behaviors. The gas-phase flame retardancy of brominated polystyrene and the solid-phase stability of ethylene bis(tetrabromophthalimide) produce a synergistic effect, reducing the total amount of flame retardant used. At the same time, the non-precipitation and heat resistance of ethylene bis(tetrabromophthalimide) can compensate for the potential defects of brominated polystyrene at high processing temperatures. After compounding, it can enhance the retention rate of the mechanical properties of polyamide.

[0031] 2) The synergistic flame retardant of this invention utilizes a composite system formed by polydimethylsiloxane PEG-7 phosphate and 1,3-dimethylimidazolium dinitrile amine salt to enhance the performance of polyamide flame retardants through a multi-level synergistic mechanism. The phosphate groups of polydimethylsiloxane PEG-7 phosphate catalyze the dehydration and crosslinking of nylon, forming an expanded char layer rich in phosphorus-carbon structures. The PEG segments improve compatibility with the nylon matrix, preventing flame retardant aggregation. The thermal decomposition of siloxane generates SiO2, enhancing the density of the char layer and blocking oxygen and heat. The high-temperature decomposition of nitrile amine anions generates nitrogen-containing free radicals (such as N·, CN·), capturing gas-phase combustion free radicals; the imidazolium cation promotes the formation of a crosslinked network, increasing the graphitization degree of the char layer. This reduces the high addition amount of single synergistic flame retardant and solves the defects of synergistic agents such as phosphate esters being prone to migration.

[0032] 3) The antioxidant components used in this invention are a combination of hexabromotoluenesulfonic acid dipentaerythritol and 4,4'-(naphthalene-1,5-diyl)diphenylamine. The aromatic amine structure of 4,4'-(naphthalene-1,5-diyl)diphenylamine can capture alkyl free radicals (R·) and peroxide free radicals (ROO·) generated during the thermal oxidation of nylon, interrupting the free radical chain reaction and decomposing the hydroperoxides (ROOH) generated by thermal oxidation. The rigid naphthalene ring structure enhances the thermal stability of the molecules, reduces the oxidative cracking of the nylon backbone at high temperatures, and delays material degradation. The sulfonic acid group of hexabromotoluenesulfonic acid dipentaerythritol catalyzes the cross-linking of nylon molecular chains at high temperatures, promoting the formation of a dense carbon layer and preventing oxygen penetration. The pentaerythritol skeleton stabilizes the structure; the rigid tetraol structure decomposes at high temperatures to generate a stable carbon skeleton, physically blocking heat transfer. Additionally, the free radical capture of bromine and the complexation of metal ions in the nylon material by the sulfonic acid group act as passivation agents. These two factors synergistically achieve excellent thermal stability of the flame-retardant polyamide material. In addition, the bromine element in hexabromotoluenesulfonic acid dipentaerythritol can play a gas-phase flame retardant role, while the pentaerythritol derivative acts as a carbon source to form solid-phase protection. The two work together to form a physical barrier, creating a dual protection mechanism that significantly slows down the combustion process of nylon.

[0033] 4) This invention successfully developed a low-addition, highly efficient, antimony-free bromide-based flame-retardant nylon system through a ternary synergistic mechanism of flame retardant, synergistic flame retardant, and antioxidant. This system not only stably achieves the UL94 V-0 flame retardant standard, but also significantly reduces the total amount of flame retardant added through the synergistic effect between components, while ensuring that the prepared material possesses excellent mechanical properties and thermal stability, providing an innovative solution for the lightweighting and high-performance of flame-retardant nylon materials.

[0034] The aforementioned beneficial effects enable polyamide materials to achieve excellent mechanical, flame-retardant, and electrical properties. Detailed Implementation

[0035] The core innovation of this invention lies in the compounding of two brominated flame retardants with complementary thermal decomposition behaviors. By utilizing the gradient difference in their decomposition temperatures, a dual flame retardant mechanism is constructed, which combines gas-phase free radical quenching with the synergistic effect of condensed-phase physical barriers. At the same time, a silicon-phosphorus composite synergistic system is introduced to further enhance the flame retardant performance through multi-level synergistic effects. This results in a polyamide composition with a flame retardant rating of UL94 V-0. Furthermore, the halogen-free synergistic flame retardant used can effectively neutralize the environmental shortcomings of brominated flame retardants, completely avoiding the negative impact of traditional antimony-halogen flame retardants on the electrical properties of the material. The system also has lower ecotoxicity, and the resulting flame-retardant polyamide material combines low ecotoxicity, high flame retardancy, and excellent mechanical properties.

[0036] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0037] The embodiments and comparative examples of the present invention use the following materials, but are not limited to the following materials:

[0038] Polyamide resin, nylon PA6 resin, trade name YH800, produced by Yueyang Petrochemical;

[0039] Polyamide resin, nylon PA66 resin, trade name EP158, produced by Huafeng Group Co., Ltd.

[0040] Flame retardant brominated polystyrene 7010 is produced by Shandong Xurui New Material Co., Ltd.

[0041] Flame retardant ethylenebistetrabromophthalimide, produced by Shouguang Weidong Chemical Co., Ltd.

[0042] Synergistic flame retardant polydimethylsiloxane PEG-7 phosphate ester, commercially available;

[0043] Synergistic flame retardant 1,3-dimethylimidazolium dinitrile amine salt, produced by Zhengzhou Jacks Chemical Products Co., Ltd.

[0044] The synergistic flame retardant bisphenol A-bis(diphenyl phosphate) is produced by Zhejiang Wansheng Co., Ltd.

[0045] Glass fiber, trade name ECS301HP-3, produced by Chongqing International Composite Materials Co., Ltd.

[0046] Antimony trioxide, a synergistic flame retardant, was purchased from Foshan Chenti Trade Co., Ltd.

[0047] The antioxidant dipentaerythritol hexabromotoluenesulfonic acid is produced by Beijing Bailingwei Technology Co., Ltd.

[0048] Antioxidant 4,4'-(naphthalene-1,5-diyl)diphenylamine, produced by Zhengzhou Alpha Chemical Co., Ltd.

[0049] The additive dipentaerythritol is produced by Hubei Xinjiecheng Chemical Technology Co., Ltd.

[0050] Antioxidant 1098, a hindered phenolic antioxidant, is produced from extremely easy sources;

[0051] Antioxidant 168, a phosphite antioxidant, is produced from extremely easy sources;

[0052] Black masterbatch, PA6-2015, commercially available.

[0053] The raw material compositions of the engineering plastics in Examples 1-5 and Comparative Examples 1-10 are shown in Table 1 below, and the preparation methods are as follows:

[0054] Preparation of flame-retardant polyamide engineering plastics:

[0055] (1) The moisture content of polyamide resin is controlled to be ≤2000ppm by drying process;

[0056] (2) Weigh the dried polyamide resin, flame retardant, synergistic flame retardant, antioxidant, processing aid and color masterbatch according to the formula (the specific types of additives are based on the component formula in Table 1), and mix them by high-speed stirring to obtain a premix; weigh the filler at the same time for later use;

[0057] (3) The premixed material is added through the main feed port of the twin-screw extruder, and the filler is added through the side feed port. The polyamide engineering plastic is obtained by melt extrusion at 260℃±10℃-granulation-drying.

[0058] Preparation of flame-retardant polyamide engineering plastic test strips:

[0059] The above materials were dried in a forced-air drying oven at 120℃ for 4 hours, and then injection molded into standard specimens at an injection molding temperature of 260-280℃. The injection-molded mechanical property specimens were then conditioned in a standard laboratory environment (23℃, 50%RH) for 24 hours before testing.

[0060] The performance indicators and testing methods are as follows:

[0061] Tensile properties: According to ISO 527 method, specimen size: 170*10*4mm, test speed 5mm / min.

[0062] Bending performance: According to ISO 178 method, the sample size is 80*10*4mm, and the test speed is 2mm / min.

[0063] Notched impact performance: according to ISO 179 method, spline size: 80*10*4mm.

[0064] Flame retardant performance: According to UL94 method, the sample size is 127*12.7*1.6mm.

[0065] Tracking Indices (CTI), according to IEC 601112, with a strip size of 15*15*3.2mm.

[0066] Tensile strength retention rate (thermal-oxidative aging): 1) The tensile strength of the injection-molded specimen after conditioning in a laboratory environment, tested according to ISO 527, is recorded as the tensile strength before aging; 2) The standard test specimen is placed in a 150℃ oven for 3000 hours, then conditioned in a laboratory environment (23℃, 50%RH) for 24 hours, and the tensile strength is tested according to ISO 527 method, recorded as the tensile strength after aging; 3) Tensile strength retention rate = tensile strength after aging / tensile strength before aging × 100%. This invention investigates the effect of antioxidant changes on tensile strength retention rate by testing the tensile strength retention rates of Example 1 and Comparative Examples 5, 6, and 8.

[0067] Table 1: Composition (by mass percentage) and properties of polyamide engineering plastics in Examples 1-5 and Comparative Examples 1-10

[0068]

[0069] As shown in Table 1, the antimony-free bromide-based flame retardant of the present invention requires a significantly reduced amount to achieve the same flame retardant rating (UL 94 V-0), while also exhibiting superior mechanical and electrical properties. Specifically, comparing Examples 1-4 with Comparative Example 10 reveals that, compared to traditional halogen flame retardant systems, the present invention achieves higher flame retardant efficiency and has less negative impact on the mechanical and electrical properties of the material at the same amount of addition.

[0070] Furthermore, the comparison between Examples 1-4 and Comparative Examples 1-2 shows that the compound of halogen flame retardants selected in this invention is superior to the use of a single halogen flame retardant. This is because the gas-phase flame retardancy of brominated polystyrene and the solid-phase stability of ethylene bis(tetrabromophthalimide) produce a synergistic effect, reducing the total amount of flame retardant used.

[0071] Furthermore, a comparison between Examples 1-4 and Comparative Examples 3-4 shows that: the silicon-based synergist migrates to the material surface to form a dense Si-O-Si / Si-C cross-linked carbon layer, isolating oxygen and heat transfer; the ionic liquid synergist catalyzes the formation of an expanded carbon layer, blocking heat and oxygen exchange; the two work synergistically with the bromine-based flame retardant through a dual pathway of condensed-phase flame retardancy and physical barrier, significantly improving flame retardant efficiency. A comparison between Examples 1-4 and Comparative Examples 5-6 confirms that, in addition to its heat and oxygen protection function, the specific antioxidant exerts a synergistic flame retardant effect through a triple mechanism of condensed-phase carbonization catalysis, gas-phase free radical capture, and endothermic decomposition. Data from Examples 1-4 and Comparative Examples 5-9 further show that the antioxidant in this system has significantly better thermal stability than conventional systems, and its flame retardant enhancement effect depends on the compounded components. A comparison between Example 1 and Comparative Examples 5, 6, and 8 shows that the combination of hexabromotoluenesulfonic acid dipentaerythritol and 4,4'-(naphthalene-1,5-diyl)diphenylamine, an antioxidant of the present invention, can effectively improve the tensile strength retention rate of the material.

[0072] Based on the aforementioned synergistic effect, this invention successfully developed a low-addition, highly efficient synergistic antimony-free bromide-based flame-retardant nylon material through a ternary synergistic system of flame retardant, synergistic flame retardant, and antioxidant. Its flame-retardant performance meets the UL 94 V-0 standard. This flame-retardant polyamide composition can be widely used in automotive parts, electronic and electrical housings, and other fields.

Claims

1. A high thermal stability, antimony-free, bromine-phosphorus synergistic flame-retardant polyamide engineering plastic, characterized in that: Composed of the following raw materials by weight percentage: Polyamide resin 25.5-89.97%; Filler 10-35%; Flame retardant 0.01-25%; Synergistic flame retardant 0.01-10%; Antioxidant 0.01-1.5%; Processing aids 0-2%; Masterbatch 0-1%; The flame retardant is a combination of brominated flame retardant A and brominated flame retardant B, wherein brominated flame retardant A is selected from brominated polystyrene and brominated flame retardant B is selected from ethylene bis(tetrabromophthalimide); the synergistic flame retardant is a combination of polydimethylsiloxane PEG-7 phosphate and 1,3-dimethylimidazolium dinitrile amine salt; and the antioxidant is a combination of hexabromotoluenesulfonic acid bispentaerythritol and 4,4'-(naphthalene-1,5-diyl)diphenylamine.

2. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 1, characterized in that: The polyamide resin is selected from one or more of PA6, PA56, PA66, PA6 / 66, PA66 / 6, PA66 / 6T, PA6T / X, PA9T, PA10T, PA10T / X, PA46, PA4T, PA5T, and PA5T / X.

3. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 1, characterized in that: The fillers are classified into two types according to their morphology: fibrous and non-fibrous. The fibrous fillers are selected from one or more of glass fiber, carbon fiber, aramid fiber, and basalt fiber, while the non-fibrous fillers are selected from one or more of whiskers, mica, kaolin, talc, glass microspheres, calcium carbonate, and wollastonite.

4. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 3, characterized in that: The filler is glass fiber with an alkali content of <0.8%, a bulk density of 0.6-0.8 g / cm³, a monofilament diameter of 7-13 μm, a chopped length of 2-5 mm, and a moisture content of ≤0.05%.

5. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 1, characterized in that: The weight ratio of the brominated flame retardant A to the brominated flame retardant B is 2:1 to 4:

1.

6. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 1, characterized in that: The weight ratio of the synergistic flame retardant polydimethylsiloxane PEG-7 phosphate to 1,3-dimethylimidazolium dinitrile amine salt is 3:1 to 4:

1.

7. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 1, characterized in that: The antioxidant hexabromotoluenesulfonic acid dipentaerythritol and 4,4'-(naphthalene-1,5-diyl)diphenylamine are present in a weight ratio of 5:1 to 6.5:

1.

8. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 1, characterized in that: The processing aid is selected from at least one of silicone powder, silicone masterbatch, pentaerythritol stearate, montan wax, polyethylene wax, oxidized polyethylene wax, and calcium stearate; wherein the silicone powder is a compound of phenyl silicone and silicon dioxide in a 1:1 weight ratio.

9. The high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to claim 1, characterized in that: The masterbatch has a carbon black content of 10%-99%, and the carrier is selected from polyamide 6 or lubricant.

10. The method for preparing the high thermal stability antimony-free bromine-phosphorus synergistic flame-retardant polyamide engineering plastic according to any one of claims 1-9, characterized in that: Includes the following steps: (1) Control the moisture content of polyamide resin to ≤2000ppm; (2) Weigh the dried polyamide resin, flame retardant, synergistic flame retardant, antioxidant, processing aid and color masterbatch according to the formula, and mix them to obtain a premix; weigh the filler at the same time for later use. (3) The premixed material is added through the main feed port of the twin-screw extruder, and the filler is added through the side feed port. The polyamide engineering plastic is obtained by melt extrusion at 260℃±10℃-granulation-drying.

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