High-temperature resistant polyamide resin and its synthesis method

Abstract

This invention discloses a high-temperature resistant polyamide resin and its synthesis method. The high-temperature resistant polyamide resin is synthesized from the following raw materials: 1,5-pentanediamine, terephthalic acid, glutaric acid, phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, and a high-temperature resistant antioxidant. This high-temperature resistant polyamide resin possesses excellent mechanical properties, flame retardant properties, and electromagnetic shielding properties, and can be widely used in communication devices requiring flame retardancy and electromagnetic shielding.

Description

Technical Field

[0001] This invention belongs to the field of materials, and in particular relates to a high-temperature resistant polyamide resin and its synthesis method. Background Technology

[0002] The synthesis methods of polyamide (PA) resins mainly include lactam self-polymerization and condensation reaction of diamines and diacids. Based on the different main chain chemical structures, PA materials can be divided into three main categories: aliphatic PA, semi-aromatic PA, and fully aromatic PA. Among them, aliphatic PA6 and PA66, which are most widely used in industry, exhibit excellent mechanical strength, wear resistance, and self-lubricating properties, but they are significantly lacking in flame retardancy (only reaching UL94 V-2 level) and completely lack electromagnetic shielding capabilities. With the stringent requirements for material temperature resistance (≥270℃) in surface mount technology (SMT) and the continuous improvement of comprehensive material performance standards in the aerospace field, the limitations of traditional PA materials are becoming increasingly significant. They are prone to thermal decomposition at high temperatures (thermal weight loss initiation temperature below 300℃) and produce molten dripping during combustion. Although fully aromatic PA has excellent heat resistance, it faces fundamental problems such as complex melt processing, high cost of flame retardant modification, and lack of electromagnetic shielding function. Although semi-aromatic PA improves heat resistance by introducing benzene ring structure, its flame retardant properties (oxygen index of about 27%) are still far from meeting the flame retardant standards of engineering plastics, and its electromagnetic shielding effectiveness cannot meet the protection requirements of modern electronic devices.

[0003] Modification techniques for the flame retardant properties of polyamide materials are mainly divided into three categories: additive flame retardants, reactive flame retardants, and composite flame retardant systems. Among additive flame retardants, halogen-antimony synergistic systems (such as the combination of decabromodiphenyl ethane and antimony oxide) can significantly improve flame retardant efficiency, but suffer from insufficient environmental friendliness. Phosphorus-based flame retardants (such as ammonium polyphosphate) achieve their barrier effect by forming a dense char layer during combustion. Inorganic hydroxides (such as aluminum hydroxide and magnesium hydroxide) have environmental advantages, but usually require a high proportion of over 50% to meet flame retardant requirements, which often leads to a decrease in the material's mechanical properties. Reactive flame retardants embed flame retardant elements (such as phosphorus- or nitrogen-containing monomers) into the polymer backbone through chemical copolymerization. Representative substances include bis(hydroxyethyl)methylphosphine oxide. This method can achieve a long-lasting flame retardant effect, but the preparation process is relatively complex. Composite flame retardant systems combine various modification methods, such as the synergistic effect of glass fiber reinforcement and flame retardants, or the use of nanomaterials such as carbon nanotubes and layered silicates. These technologies can not only improve flame retardant performance, but also improve the mechanical properties of materials, thus becoming a current research hotspot.

[0004] Currently, some research has been conducted on copolymer flame-retardant polyamide resins in existing technologies. For example, Chinese patent CN112048061A uses N,N-bis(6-aminohexyl)phenylphosphamide and diacid to synthesize flame retardant salts, which are then directly polycondensed with PA6 / PA66 oligomers; CN104231262A prepares textile flame-retardant polyamides via a prepolymer method, first reacting the flame retardant with diamine to generate a prepolymer before copolymerization; CN112144141A uses DOPO derivative-based flame retardant salts to produce... The material is a spinning raw material; CN112048779A and CN112048061A have similar technical routes but optimized reaction conditions (210-220℃ / 1.7-1.9MPa); CN115894903A innovatively uses DOPO-barium itaconic acid flame retardant and prepares PA66 through a post-feeding process; CN105131280A prepares halogen-free flame-retardant PA66 resin through phosphine oxide dicarboxylic acid; CN116789959A solves the molecular weight distribution problem of flame-retardant polyamide through solid-phase thickening polymerization. In summary, the existing patented technologies mainly exhibit three characteristics: First, the process routes are divided into two categories: prepolymer method and direct copolymerization method, the core of which is the polycondensation reaction of phosphorus-based flame retardant salts and PA6 / PA66 oligomers; second, the technological innovations are concentrated in flame retardant structure design (such as DOPO derivatives, organophosphorus ammonium salts), process optimization (solid phase thickening, post-feeding) and halogen-free direction; third, the applications cover engineering plastics, fibers and films, among which fiber preparation mostly adopts the process route of direct spinning of flame retardant copolymers. Summary of the Invention

[0005] Based on this, one of the objectives of the present invention is to provide a high-temperature resistant polyamide resin, which has excellent mechanical properties, flame retardant properties and electromagnetic shielding properties, and can be widely used in the field of communication devices that require flame retardancy and electromagnetic shielding.

[0006] The specific technical solution to achieve the above-mentioned objectives is as follows:

[0007] A high-temperature resistant polyamide resin is prepared from raw materials comprising the following parts by weight:

[0008] 102.2 parts of 1,5-pentanediamine

[0009] Terephthalic acid 66.5–99.7 parts,

[0010] Glutaric acid 52.9–79.3 parts,

[0011] Contains 30-60 parts of phosphoramide salt,

[0012] 5.5–7.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0013] 23–31 parts of organic carbon nanotubes,

[0014] 5-7 parts benzoic acid

[0015] 0.5–1.5 parts of high-temperature resistant antioxidant;

[0016] The diamine (1,5-pentanediamine) and the dicarboxylic acid (the molar sum of terephthalic acid and glutaric acid) are in an equimolar ratio; the phosphoramide salt is obtained by a salt-forming reaction of 2-carboxyethylphenyl hypophosphite and 1,5-pentanediamine; the organic carbon nanotubes are obtained by organic modification of carbon nanotubes with γ-aminopropyltriethoxysilane; the high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0017] In some embodiments, the high-temperature resistant polyamide resin is prepared from raw materials comprising the following parts by weight:

[0018] 102.2 parts of 1,5-pentanediamine

[0019] Terephthalic acid 74.8–91.4 parts,

[0020] Glutaric acid 59.5–72.7 parts,

[0021] Contains 35-55 parts of phosphoramide salt.

[0022] 2,2'-(1,3-phenylene)-dioxazoline 5.8–7.2 parts,

[0023] 25–29 parts of organic carbon nanotubes,

[0024] Benzoic acid 5.3–6.7 parts,

[0025] 0.7 to 1.3 parts of high-temperature resistant antioxidant.

[0026] In some embodiments, the high-temperature resistant polyamide resin is prepared from raw materials comprising the following parts by weight:

[0027] 102.2 parts of 1,5-pentanediamine

[0028] 78.1–88 parts of terephthalic acid

[0029] Glutaric acid 62.1–70 parts,

[0030] Contains 40-50 parts of phosphoramide salt,

[0031] 2,2'-(1,3-phenylene)-dioxazoline 6.1–6.9 parts,

[0032] 26–28 parts of organic carbon nanotubes,

[0033] Benzoic acid 5.6–6.4 parts,

[0034] 0.8 to 1.2 parts of high-temperature resistant antioxidant.

[0035] In some embodiments, the preparation method of the phosphoramide salt includes the following steps: 214.16 g of 2-carboxyethylphenyl hypophosphite and 102.18 g of 1,5-pentanediamine are added to a stirred polymerization reactor, followed by the addition of 150 mL to 200 mL of deionized water. The reactor is then evacuated for 2 to 6 minutes, and nitrogen is purged for 2 to 6 minutes. This cycle is repeated 3 to 5 times, controlling the system pressure inside the stirred polymerization reactor to 0.1 MPa to 0.3 MPa. The stirred polymerization reactor is then heated to 85°C to 95°C in a sealed environment for 0.5 to 1.5 hours, with the stirring speed controlled at 50 r / min to 100 r / min. After the salt-forming reaction is completed for 1 to 2 hours, the pressure inside the reactor is reduced to 0.1 MPa, the product is discharged, and vacuum dried.

[0036] In some embodiments, the method for preparing the organic carbon nanotubes includes the following steps: adding 100 g of carbon nanotubes and 2.5 g to 3.5 g of γ-aminopropyltriethoxysilane to a high-speed stirrer and stirring at room temperature for 6 min to 10 min to obtain organic carbon nanotubes.

[0037] In some embodiments, the average diameter of the carbon nanotubes in the organic carbon nanotubes is 8 nm to 10 nm, and their structure is array-type.

[0038] Another object of the present invention is to provide a method for preparing the above-mentioned high-temperature resistant polyamide resin.

[0039] The specific technical solution to achieve the above-mentioned objectives is as follows:

[0040] A method for preparing a high-temperature resistant polyamide resin includes the following steps:

[0041] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and appropriate amount of water. Then, the reactor is evacuated for 2 min to 6 min and purged with nitrogen for 2 min to 6 min. This cycle is repeated 3 to 5 times, and the system pressure in the stirred polymerization reactor is controlled to be 0.1 MPa to 0.3 MPa.

[0042] (2) Adjust the stirring speed of the stirred polymerization reactor to 20 r / min to 40 r / min, and heat the stirred polymerization reactor to 279℃ to 283℃ in a closed and uniform manner for 2 to 4 hours. When the temperature of the stirred polymerization reactor reaches 211℃, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1 to 2 hours (prepolymerization reaction), release the gas to atmospheric pressure and raise the temperature to 313℃ to 317℃. Continue to react for 1 to 2 hours (postpolymerization reaction). Maintain constant temperature and vacuum for 15 min to 45 min (viscosification reaction). When the reaction is completed, add nitrogen gas when discharging to obtain the product.

[0043] In some embodiments, the method for preparing the high-temperature resistant polyamide resin includes the following steps:

[0044] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and appropriate amount of water. Then, the reactor is evacuated for 3 min to 5 min and purged with nitrogen for 3 min to 5 min. This cycle is repeated 3 to 5 times, and the system pressure in the stirred polymerization reactor is controlled to be 0.15 MPa to 0.25 MPa.

[0045] (2) Adjust the stirring speed of the stirred polymerization reactor to 25 r / min to 35 r / min, and heat the stirred polymerization reactor to 280℃ to 282℃ in a closed and uniform manner for 2.5 hours to 3.5 hours. When the temperature of the stirred polymerization reactor reaches 211℃, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.2 hours to 1.8 hours (prepolymerization reaction), release the gas to atmospheric pressure and simultaneously raise the temperature to 314℃ to 316℃. Continue to react for 1.2 hours to 1.8 hours (postpolymerization reaction). Maintain constant temperature and continuously evacuate for 20 min to 40 min (viscosification reaction). When the reaction is completed, add nitrogen gas when discharging to obtain the final product.

[0046] The functions of each raw material in the high-temperature resistant polyamide resin of this invention are as follows:

[0047] This invention reduces the melting point of high-temperature resistant polyamide resin (PA5T) by adding glutaric acid as a comonomer. The mechanism is mainly reflected in the following aspects: (1) Enhanced molecular chain flexibility. Glutaric acid, as an aliphatic diacid monomer, forms flexible segments (PA55) by polycondensation with pentanediamine. Its introduction disrupts the regularity of the benzene ring structure in PA5T, reduces the intermolecular forces, and the random distribution of this flexible segment reduces the crystallinity of the copolymer (PA5T / 55), thereby significantly reducing the melting point. (2) Balance between thermal stability and processing window. The addition of glutaric acid reduces the piperidine cyclization side reaction, avoiding the viscosity decrease caused by molecular chain end capping. (3) Regulation of copolymer sequence structure. By controlling the feed ratio of glutaric acid to terephthalic acid, the distribution of aromatic and aliphatic segments in the copolymer can be adjusted. At the same time, this random copolymer structure reduces the crystallinity by disrupting the symmetry of the molecular chain, thereby achieving melting point regulation.

[0048] This invention utilizes a combination of phosphoramide salts (polymerized and inserted into the PA5T backbone) and organic carbon nanotubes to significantly enhance the flame retardant properties of high-temperature resistant polyamide resins through multiple synergistic mechanisms. The mechanism is as follows: First, the phosphoramide salts decompose at high temperatures to generate dehydrating agents such as phosphoric acid and polyphosphoric acid, promoting the charring of the PA5T backbone and forming a dense char layer. Simultaneously, the released phosphorus free radicals can capture active free radicals in the combustion chain reaction. Second, the organic carbon nanotubes rapidly disperse heat due to their high thermal conductivity, and their tubular structure forms a physical barrier within the char layer, delaying the diffusion of heat and oxygen. Furthermore, the amide groups of the carbon nanotubes and the PA5T backbone enhance interfacial bonding through entanglement and adsorption, making the char layer structure more stable. The catalytic effect of phosphorus further enhances the oxidation resistance of the char layer. This synergistic mechanism of chemical inhibition, physical barrier, and structural reinforcement significantly reduces the heat release rate and smoke generation of the material, achieving a balance between high-efficiency flame retardancy and mechanical properties. Meanwhile, organic carbon nanotubes significantly enhance the electromagnetic shielding performance of high-temperature resistant polyamide resins through a multi-dimensional synergistic mechanism. Surface modifications (such as amylation) optimize dispersibility, constructing a continuous conductive network within the matrix. Electromagnetic wave reflection loss is achieved through free electron migration, and polarization relaxation induced by tube wall defects and functional groups enhances absorption loss. The stable matrix of the high-temperature resistant polyamide maintains network integrity, while interfacial hydrogen bonding reduces signal transmission. Ultimately, efficient electromagnetic shielding is achieved through a synergistic effect of "conductivity-dissipation-interface."

[0049] This invention effectively enhances the interfacial bonding performance between organic carbon nanotubes and high-temperature resistant polyamide resin by introducing 2,2'-(1,3-phenylene)-dioxazoline as a compatibilizer. The oxazoline group in this compound can simultaneously react chemically with the functional groups on the surface of carbon nanotubes and the terminal amino groups of polyamide resin to form a stable chemical bonding network, thereby significantly enhancing the compatibility and interfacial adhesion strength between the two phases.

[0050] As a monofunctional compound, benzoic acid undergoes a condensation reaction between its carboxyl group and the terminal amino group of high-temperature resistant polyamide during melt polymerization. Because this reaction causes the benzoic acid molecule to lose its ability to continue participating in chain growth, it can act as a molecular weight regulator, effectively controlling the molecular weight (intrinsic viscosity) of the polymer by limiting the extension of the polymer chain.

[0051] The high-temperature resistant antioxidant N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide exhibits excellent thermal stability under high-temperature conditions due to the steric hindrance effect of the four methyl groups on the piperidine ring. Its steric hindrance structure can efficiently capture free radicals and effectively delay material aging. During the synthesis of high-temperature resistant polyamide resins, the amide groups of this compound can react with the resin end groups, acting as end-capping agents to precisely control the molecular weight, and also permanently anchoring to the polymer backbone through chemical bonding, thereby significantly improving the compatibility of the copolymer. This dual-action mechanism not only endows the material with durable antioxidant properties but also improves the dyeing properties of the copolymer, achieving synergistic optimization of functionality and processability.

[0052] Compared with the prior art, the high-temperature resistant polyamide resin and its synthesis method provided by the present invention have the following beneficial effects:

[0053] 1. To address the shortcomings of high-temperature resistant polyamide resins, such as a narrow processing temperature range, poor flame retardancy, and lack of electromagnetic shielding, this invention designs a new resin molecular structure. By adding glutaric acid to lower the melting point of the copolymer, and by compounding with phosphoramide salts and organic carbon nanotubes, the flame retardancy of the high-temperature resistant polyamide resin is synergistically improved. Furthermore, the electromagnetic shielding performance of the high-temperature resistant polyamide resin is enhanced by organic carbon nanotubes. This results in a high-temperature resistant polyamide resin with excellent mechanical properties, flame retardancy, and electromagnetic shielding properties, which can be widely used in communication devices requiring flame retardancy and electromagnetic shielding.

[0054] 2. This invention achieves multiple synergistic performance enhancements in high-temperature resistant polyamide resin by combining phosphoramide-containing salts and organic carbon nanotubes: In terms of flame retardancy, carbon nanotubes form a nano-network structure upon heating, delaying heat diffusion and synergistically enhancing the char layer strength with the char layer catalyzed by phosphoramide; carbon nanotubes adsorb free radicals to terminate chain reactions, while phosphoramide decomposes inert gases to dilute the concentration of combustibles, and simultaneously optimizes the degradation pathway to reduce combustible release, significantly improving flame retardant efficiency. In terms of electromagnetic shielding performance, the surface modification of organic carbon nanotubes optimizes dispersibility, constructing a continuous conductive network to achieve reflection loss through free electron migration; tube wall defects and functional groups induce polarization relaxation to enhance absorption loss, while the high-temperature resistant polyamide matrix maintains network integrity, and interfacial hydrogen bonds reduce signal transmission, ultimately achieving efficient electromagnetic shielding through a synergistic mechanism of "conduction-dissipation-interface".

[0055] 3. This invention provides a highly efficient preparation method for high-temperature resistant polyamide resin, whose innovative process design significantly improves reaction efficiency and product quality. The specific implementation steps include: firstly, nitrogen gas is introduced to replace oxygen in the system before the reaction to effectively suppress side reactions; then, an appropriate amount of water is injected to optimize the mass and heat transfer conditions in the reactor by utilizing the steam pressure generated during heating. Vacuum treatment is used during the reaction stage to remove low-molecular-weight byproducts generated during polymerization in a timely manner, thereby promoting the forward shift of the reaction equilibrium. The advantages of this process are: (1) low-molecular-weight substances can be separated without the need for additional extraction equipment, which shortens the process flow and reduces energy consumption; (2) the melt polycondensation process is used throughout, avoiding the use of organic solvents and fundamentally eliminating the solvent recovery link; (3) residual trace amounts of low-molecular-weight substances have no negative impact on material performance, ensuring the stability of product quality. This simple and environmentally friendly preparation method achieves a dual improvement in production efficiency and product performance. Attached Figure Description

[0056] Figure 1 This is a flow chart of the preparation process of the high-temperature resistant polyamide resin of the present invention. Detailed Implementation

[0057] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0058] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this invention includes any and all combinations of one or more of the associated listed items.

[0059] The reaction mechanism of the high-temperature resistant polyamide resin of this invention is as follows (see the preparation process flow chart). Figure 1 ):

[0060]

[0061] Where a = 20~60, b = 20~60, c = 1~10, d = 1~3.

[0062] Reaction mechanism

[0063] As can be seen from the above reaction formula, the terminal carboxyl group of 2-carboxyethylphenyl hypophosphite reacts with the terminal amino group of 1,5-pentanediamine to obtain a phosphorus-containing amide salt. Then, the phosphorus-containing amide salt, terephthalic acid, 1,5-pentanediamine, glutaric acid, and 2,2'-(1,3-phenylene)-dioxazoline react to obtain a high-temperature resistant polyamide resin.

[0064] The raw materials used in the embodiments of the present invention are as follows:

[0065] 1,5-Pentanediamine was selected from Shanghai Kaisai Biotechnology Co., Ltd.

[0066] Terephthalic acid, selected from Beijing Yanshan Petrochemical Company.

[0067] Glutaric acid, selected from Liaoyang Hengye Chemical Co., Ltd.

[0068] Contains phosphoramide salts, self-made; the 2-carboxyethylphenyl hypophosphite in the raw materials is selected from Zhejiang Jiaxing Alpha Fine Chemical Co., Ltd.

[0069] 2,2'-(1,3-phenylene)-dioxazoline was selected from Hubei Jiufenglong Chemical Co., Ltd.

[0070] Organic carbon nanotubes, self-made, with an average diameter of 9 nm and an array structure, were selected from LG Chem (China) Investment Co., Ltd., and γ-aminopropyltriethoxysilane was selected from Nanjing Youpu Chemical Co., Ltd.

[0071] Benzoic acid was selected from Sinopharm Chemical Reagent Co., Ltd.

[0072] N,N'-Bis(2,2,6,6-Tetramethyl-4-piperidinyl)-1,3-phenylenediamide, selected from Clariant Chemicals (China) Co., Ltd.

[0073] The phosphoramide salts used in the following examples were prepared using the following steps: 214.16 g of 2-carboxyethylphenyl hypophosphite and 102.18 g of 1,5-pentanediamine were added to a stirred polymerization reactor, followed by the addition of 175 mL of deionized water. The reactor was evacuated for 4 min, then purged with nitrogen for 4 min, and this cycle was repeated 4 times, maintaining the system pressure in the stirred polymerization reactor at 0.2 MPa. The stirred polymerization reactor was then heated to 90°C in a sealed environment within 1 hour, with the stirring speed controlled at 75 r / min. After a 1.5-hour salt formation reaction, the reaction was completed, the pressure inside the reactor was reduced to 0.1 MPa, the product was discharged, and vacuum dried for later use.

[0074] The organic carbon nanotubes used in the following examples are prepared by the following steps: 100 g of carbon nanotubes and 3 g of γ-aminopropyltriethoxysilane are added to a high-speed stirrer and stirred at room temperature for 8 min to obtain organic carbon nanotubes.

[0075] The present invention will be described in detail below with reference to specific embodiments.

[0076] Example 1: High-temperature resistant polyamide resin and its synthesis method

[0077] The high-temperature resistant polyamide resin of this embodiment is prepared from raw materials comprising the following parts by weight:

[0078] 102.2 parts of 1,5-pentanediamine

[0079] 99.7 parts of terephthalic acid

[0080] Glutaric acid 52.9 parts,

[0081] Contains 30 parts of phosphoramide salt,

[0082] 5.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0083] 23 portions of organic carbon nanotubes,

[0084] 5 parts benzoic acid

[0085] 0.5 parts of high-temperature resistant antioxidant;

[0086] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0087] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0088] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor is then evacuated for 2 min and purged with nitrogen for 2 min. This cycle is repeated 5 times, and the system pressure in the stirred polymerization reactor is controlled to be 0.1 MPa.

[0089] (2) Adjust the stirring speed of the stirred polymerization reactor to 20 r / min, and heat the stirred polymerization reactor to 279°C in a closed and uniform manner within 2 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 2 hours, release the gas to atmospheric pressure and raise the temperature to 313°C. Continue to react for 2 hours, maintain the temperature and continuously evacuate for 15 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0090] Example 2 High-temperature resistant polyamide resin and its synthesis method

[0091] The high-temperature resistant polyamide resin of this embodiment is prepared from raw materials comprising the following parts by weight:

[0092] 102.2 parts of 1,5-pentanediamine

[0093] 91.4 parts of terephthalic acid

[0094] Glutaric acid 59.5 parts,

[0095] Contains 35 parts of phosphoramide salt,

[0096] 5.8 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0097] 25 parts of organic carbon nanotubes,

[0098] Benzoic acid 5.3 parts,

[0099] 0.7 parts of high-temperature resistant antioxidant;

[0100] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0101] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0102] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid were added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor was then evacuated for 6 min and purged with nitrogen for 6 min. This cycle was repeated 3 times, and the system pressure in the stirred polymerization reactor was controlled to be 0.3 MPa.

[0103] (2) Adjust the stirring speed of the stirred polymerization reactor to 40 r / min, and heat the stirred polymerization reactor to 283°C in a closed and uniform manner within 4 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1 hour, release the gas to atmospheric pressure and raise the temperature to 317°C. Continue to react for 1 hour, maintain the temperature and continuously evacuate for 45 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0104] Example 3 High-temperature resistant polyamide resin and its synthesis method

[0105] The high-temperature resistant polyamide resin of this embodiment is prepared from raw materials comprising the following parts by weight:

[0106] 102.2 parts of 1,5-pentanediamine

[0107] 88 parts of terephthalic acid

[0108] 62.1 parts of glutaric acid

[0109] Contains 40 parts of phosphoramide salt,

[0110] 6.1 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0111] 26 portions of organic carbon nanotubes,

[0112] Benzoic acid 5.6 parts,

[0113] 0.8 parts of high-temperature resistant antioxidant;

[0114] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0115] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0116] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. Then, the reactor is evacuated for 3 min and purged with nitrogen for 3 min. This cycle is repeated 5 times, and the system pressure in the stirred polymerization reactor is controlled to be 0.15 MPa.

[0117] (2) Adjust the stirring speed of the stirred polymerization reactor to 25 r / min, and heat the stirred polymerization reactor to 280°C in a closed and uniform manner within 2.5 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.8 hours, release the gas to atmospheric pressure and raise the temperature to 314°C. Continue to react for 1.8 hours, maintain the temperature and continuously evacuate for 20 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0118] Example 4 High-temperature resistant polyamide resin and its synthesis method

[0119] The high-temperature resistant polyamide resin of this embodiment is prepared from raw materials comprising the following parts by weight:

[0120] 102.2 parts of 1,5-pentanediamine

[0121] 83.1 parts of terephthalic acid

[0122] 66.1 parts of glutaric acid

[0123] Contains 45 parts of phosphoramide salt,

[0124] 6.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0125] 27 portions of organic carbon nanotubes,

[0126] Benzoic acid 6 parts,

[0127] 1 part of high-temperature resistant antioxidant;

[0128] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0129] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0130] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor is then evacuated for 5 min and purged with nitrogen for 5 min. This cycle is repeated 3 times, and the system pressure in the stirred polymerization reactor is controlled to be 0.25 MPa.

[0131] (2) Adjust the stirring speed of the stirred polymerization reactor to 35 r / min, and heat the stirred polymerization reactor to 282°C in a closed and uniform manner within 3.5 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.2 hours, release the gas to atmospheric pressure and raise the temperature to 316°C. Continue to react for 1.2 hours, maintain the temperature and continuously evacuate for 40 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0132] Example 5 High-temperature resistant polyamide resin and its synthesis method

[0133] The high-temperature resistant polyamide resin of this embodiment is prepared from raw materials comprising the following parts by weight:

[0134] 102.2 parts of 1,5-pentanediamine

[0135] 78.1 parts of terephthalic acid

[0136] 70 parts of glutaric acid

[0137] Contains 50 parts of phosphoramide salt,

[0138] 6.9 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0139] 28 portions of organic carbon nanotubes,

[0140] Benzoic acid 6.4 parts,

[0141] 1.2 parts of high-temperature resistant antioxidant;

[0142] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0143] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0144] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid were added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor was then evacuated for 4 min and purged with nitrogen for 4 min. This cycle was repeated 4 times, and the system pressure in the stirred polymerization reactor was controlled to be 0.2 MPa.

[0145] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0146] Example 6 High-temperature resistant polyamide resin and its synthesis method

[0147] The high-temperature resistant polyamide resin of this embodiment is prepared from raw materials comprising the following parts by weight:

[0148] 102.2 parts of 1,5-pentanediamine

[0149] 74.8 parts of terephthalic acid

[0150] 72.7 parts of glutaric acid

[0151] Contains 55 parts of phosphoramide salt,

[0152] 7.2 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0153] 29 portions of organic carbon nanotubes,

[0154] Benzoic acid 6.7 parts,

[0155] 1.3 parts of high-temperature resistant antioxidant;

[0156] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0157] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0158] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid were added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor was then evacuated for 4 min and purged with nitrogen for 4 min. This cycle was repeated 4 times, and the system pressure in the stirred polymerization reactor was controlled to be 0.2 MPa.

[0159] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0160] Example 7 High-temperature resistant polyamide resin and its synthesis method

[0161] The high-temperature resistant polyamide resin of this embodiment is prepared from raw materials comprising the following parts by weight:

[0162] 102.2 parts of 1,5-pentanediamine

[0163] 66.5 parts of terephthalic acid

[0164] 79.3 parts of glutaric acid

[0165] Contains 60 parts of phosphoramide salt,

[0166] 7.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0167] 31 portions of organic carbon nanotubes,

[0168] 7 parts benzoic acid

[0169] 1.5 parts of high-temperature resistant antioxidant;

[0170] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0171] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0172] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid were added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor was then evacuated for 4 min and purged with nitrogen for 4 min. This cycle was repeated 4 times, and the system pressure in the stirred polymerization reactor was controlled to be 0.2 MPa.

[0173] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0174] Comparative Example 1

[0175] The high-temperature resistant polyamide resin of this comparative example is prepared from raw materials comprising the following parts by weight:

[0176] 102.2 parts of 1,5-pentanediamine

[0177] 66.5 parts of terephthalic acid

[0178] 79.3 parts of glutaric acid

[0179] 7.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0180] 31 portions of organic carbon nanotubes,

[0181] 7 parts benzoic acid

[0182] 1.5 parts of high-temperature resistant antioxidant;

[0183] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0184] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0185] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid were added to a stirred polymerization reactor, along with 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor was then evacuated for 4 min and purged with nitrogen for 4 min. This cycle was repeated 4 times to control the system pressure in the stirred polymerization reactor to 0.2 MPa.

[0186] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0187] Comparative Example 2

[0188] The high-temperature resistant polyamide resin of this comparative example is prepared from raw materials comprising the following parts by weight:

[0189] 102.2 parts of 1,5-pentanediamine

[0190] 66.5 parts of terephthalic acid

[0191] 79.3 parts of glutaric acid

[0192] Contains 60 parts of phosphoramide salt,

[0193] 31 portions of organic carbon nanotubes,

[0194] 7 parts benzoic acid

[0195] 1.5 parts of high-temperature resistant antioxidant;

[0196] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0197] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0198] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor is then evacuated for 4 min and purged with nitrogen for 4 min. This cycle is repeated 4 times to control the system pressure in the stirred polymerization reactor to 0.2 MPa.

[0199] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0200] Comparative Example 3

[0201] The high-temperature resistant polyamide resin of this comparative example is prepared from raw materials comprising the following parts by weight:

[0202] 102.2 parts of 1,5-pentanediamine

[0203] 66.5 parts of terephthalic acid

[0204] 79.3 parts of glutaric acid

[0205] Contains 60 parts of phosphoramide salt,

[0206] 7.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0207] 7 parts benzoic acid

[0208] 1.5 parts of high-temperature resistant antioxidant;

[0209] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0210] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0211] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, benzoic acid, high-temperature antioxidant and 200 mL of water. The reactor is then evacuated for 4 min and purged with nitrogen for 4 min. This cycle is repeated 4 times to control the system pressure in the stirred polymerization reactor to 0.2 MPa.

[0212] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0213] Comparative Example 4

[0214] The high-temperature resistant polyamide resin of this comparative example is prepared from raw materials comprising the following parts by weight:

[0215] 102.2 parts of 1,5-pentanediamine

[0216] 66.5 parts of terephthalic acid

[0217] 79.3 parts of glutaric acid

[0218] Contains 60 parts of phosphoramide salt,

[0219] 7.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0220] 31 portions of organic carbon nanotubes,

[0221] 1.5 parts of high-temperature resistant antioxidant;

[0222] The high-temperature resistant antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0223] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0224] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid were added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, high-temperature antioxidant and 200 mL of water. The reactor was then evacuated for 4 min and purged with nitrogen for 4 min. This cycle was repeated 4 times to control the system pressure in the stirred polymerization reactor to 0.2 MPa.

[0225] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0226] Comparative Example 5

[0227] The high-temperature resistant polyamide resin of this comparative example is prepared from raw materials comprising the following parts by weight:

[0228] 102.2 parts of 1,5-pentanediamine

[0229] 66.5 parts of terephthalic acid

[0230] 79.3 parts of glutaric acid

[0231] Contains 60 parts of phosphoramide salt,

[0232] 7.5 parts of 2,2'-(1,3-phenylene)-dioxazoline

[0233] 31 portions of organic carbon nanotubes,

[0234] 7 parts benzoic acid.

[0235] The preparation method of the above-mentioned high-temperature resistant polyamide resin includes the following steps:

[0236] (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid were added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid and 200 mL of water. The reactor was then evacuated for 4 min and purged with nitrogen for 4 min. This cycle was repeated 4 times to control the system pressure in the stirred polymerization reactor to 0.2 MPa.

[0237] (2) Adjust the stirring speed of the stirred polymerization reactor to 30 r / min, and heat the stirred polymerization reactor to 281°C in a sealed and uniform manner within 3 hours. When the temperature of the stirred polymerization reactor reaches 211°C, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1.5 hours, release the gas to atmospheric pressure and raise the temperature to 315°C. Continue to react for 1.5 hours, maintain the temperature and continuously evacuate for 30 minutes. When the reaction ends, add nitrogen gas when discharging to obtain the final product.

[0238] The following is a list of the raw material composition of Examples 1-7 and Comparative Examples 1-5.

[0239] Table 1. Summary of raw material composition for Examples 1-7 and Comparative Examples 1-5

[0240]

[0241]

[0242] In the above examples and comparative examples, the amount of 1,5-pentanediamine added was 102.2 parts; the high-temperature antioxidant was N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0243] Examples 1-7 were used to prepare high-temperature resistant polyamide resins by adjusting the amounts of terephthalic acid, glutaric acid, phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, and high-temperature antioxidants. Comparative Examples 1-5 were used to prepare high-temperature resistant polyamide resins based on the raw materials of Example 7. Comparative Example 1 prepared a high-temperature resistant polyamide resin without adding phosphoramide salt; Comparative Example 2 prepared a high-temperature resistant polyamide resin without adding 2,2'-(1,3-phenylene)-dioxazoline; Comparative Example 3 prepared a high-temperature resistant polyamide resin without adding organic carbon nanotubes; Comparative Example 4 prepared a high-temperature resistant polyamide resin without adding benzoic acid; and Comparative Example 5 prepared a high-temperature resistant polyamide resin without adding a high-temperature antioxidant. The high-temperature resistant polyamide resins prepared in the above examples and comparative examples were subjected to the following performance tests:

[0244] Tensile properties: Tested according to GB / T 1040-2006 standard, the tensile rate is 50 mm / min.

[0245] Notched impact performance: tested according to GB / T 1843-2008 standard.

[0246] Flame retardant performance: According to GB / T 2406.2-2009 standard, the limiting oxygen index of the sample was determined using an oxygen index meter. The sample size was 100 mm × 10 mm × 4 mm.

[0247] Microwave absorption performance: Tested according to GJB 5239-2004 standard using a vector network analyzer from Agilent Technologies, USA. The sample was a coaxial ring specimen with a thickness of 2mm, an outer diameter of 7mm, and an inner diameter of 3mm. A wider microwave frequency bandwidth indicates better coverage, and a higher microwave frequency indicates even better performance. Microwave absorption performance reflects a material's ability to absorb electromagnetic waves; a larger absolute value indicates greater attenuation of electromagnetic waves after passing through the material, resulting in better absorption performance and thus better electromagnetic shielding.

[0248] Intrinsic viscosity: Tested according to GB / T 1632-2008 standard, with concentrated sulfuric acid as the solvent.

[0249] Melting temperature: Tested according to GB / T 19466.3-2004 standard.

[0250] The performance test results are shown in Table 2.

[0251] Table 2. Performance of the high-temperature resistant polyamide resins in Examples 1-7 and Comparative Examples 1-5

[0252]

[0253]

[0254] As can be seen from Table 2:

[0255] As the amount of organic carbon nanotubes added increases, the tensile strength of high-temperature resistant polyamide resin shows an increasing trend. This is mainly due to the influence of two factors: (1) Organic carbon nanotubes play a reinforcing role for high-temperature resistant polyamide resin, which is the main effect; (2) The higher the intrinsic viscosity of high-temperature resistant polyamide resin, the higher the van der Waals force between its molecules, and the higher its tensile strength, which is the secondary effect.

[0256] With the increase of glutaric acid addition, the notched impact properties of high-temperature resistant polyamide resin show an increasing trend. This is because glutaric acid, as an aliphatic diacid monomer, forms a flexible chain segment (PA55) through polycondensation with pentanediamine. Its introduction disrupts the regularity of the benzene ring structure in PA5T, reduces the intermolecular forces, and enhances the flexibility of the molecular chain.

[0257] With increasing additions of phosphoramide salts and organic carbon nanotubes, the flame retardant and microwave absorption properties of high-temperature resistant polyamide resins show an increasing trend. This is because phosphoramide salts decompose at high temperatures to generate dehydrating agents such as phosphoric acid and polyphosphoric acid, promoting the charring of the PA5T main chain to form a dense carbon layer. Simultaneously, the released phosphorus free radicals can capture active free radicals in the combustion chain reaction. Secondly, the organic carbon nanotubes rapidly disperse heat through their high thermal conductivity, and their tubular structure forms a physical barrier in the carbon layer, delaying the diffusion of heat and oxygen. Furthermore, the amide groups of the carbon nanotubes and PA5T main chain enhance interfacial bonding through entanglement and adsorption, making the carbon layer structure more stable, while the catalytic effect of phosphorus further improves the oxidation resistance of the carbon layer. This synergistic mechanism of chemical inhibition, physical barrier, and structural reinforcement significantly reduces the heat release rate and smoke generation of the material, achieving a balance between high-efficiency flame retardancy and mechanical properties. Meanwhile, organic carbon nanotubes significantly enhance the electromagnetic shielding performance of high-temperature resistant polyamide resins through a multi-dimensional synergistic mechanism. Surface modifications (such as amylation) optimize dispersibility, constructing a continuous conductive network within the matrix. Electromagnetic wave reflection loss is achieved through free electron migration, and polarization relaxation induced by tube wall defects and functional groups enhances absorption loss. The stable matrix of the high-temperature resistant polyamide maintains network integrity, while interfacial hydrogen bonding reduces signal transmission. Ultimately, efficient electromagnetic shielding is achieved through a synergistic effect of "conductivity-dissipation-interface."

[0258] As the amount of benzoic acid added increases, the intrinsic viscosity of the high-temperature resistant polyamide resin shows a decreasing trend. This is because, as a monofunctional compound, the carboxyl group of benzoic acid undergoes a condensation reaction with the terminal amino group of the high-temperature resistant polyamide during melt polymerization. Since this reaction causes the benzoic acid molecule to lose its ability to continue participating in chain growth, it can act as a molecular weight regulator, effectively controlling the molecular weight (intrinsic viscosity) of the polymer by limiting the extension of the polymer chain.

[0259] As the amount of glutaric acid added increases, the melting temperature of the high-temperature resistant polyamide resin shows a decreasing trend. This is because glutaric acid, as an aliphatic diacid monomer, condenses with pentanediamine to form flexible segments (PA55). Its introduction disrupts the regularity of the benzene ring structure in PA5T, reducing the intermolecular forces. Furthermore, the random distribution of these flexible segments decreases the crystallinity of the copolymer (PA5T / 55), thus significantly lowering the melting point. Moreover, by controlling the feed ratio of glutaric acid to terephthalic acid, the distribution of aromatic and aliphatic segments in the copolymer can be adjusted. Simultaneously, this random copolymer structure reduces crystallinity by disrupting the symmetry of the molecular chains, thereby achieving melting point control.

[0260] In summary, by adjusting the amounts of terephthalic acid, glutaric acid, phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, and high-temperature antioxidant, the high-temperature resistant polyamide resin of this invention, with its excellent mechanical properties, flame retardant properties, and electromagnetic shielding properties, can be obtained under the synergistic effect of these additives.

[0261] Compared to Example 7, Comparative Example 1 prepared a high-temperature resistant polyamide resin without the addition of phosphoramide salt. The combination of phosphoramide salt (polymerized and inserted into the PA5T backbone) and organic carbon nanotubes significantly improved the flame retardant properties of the high-temperature resistant polyamide resin through multiple synergistic mechanisms. The mechanisms are as follows: First, the phosphoramide salt decomposes at high temperatures to generate dehydrating agents such as phosphoric acid and polyphosphoric acid, promoting the charring of the PA5T backbone to form a dense carbon layer. Simultaneously, the released phosphorus free radicals can capture active free radicals in the combustion chain reaction. Second, the organic carbon nanotubes rapidly disperse heat through their high thermal conductivity, and their tubular structure forms a physical barrier in the carbon layer, delaying the diffusion of heat and oxygen. Furthermore, the amide groups of the carbon nanotubes and the PA5T backbone enhance the interfacial bonding force through entanglement and adsorption, making the carbon layer structure more stable. The catalytic effect of phosphorus further enhances the oxidation resistance of the carbon layer. This synergistic mechanism of chemical inhibition, physical barrier, and structural reinforcement significantly reduces the heat release rate and smoke generation of the material, achieving a balance between high-efficiency flame retardancy and mechanical properties. Therefore, the flame retardant performance of Comparative Example 1 is lower than that of Example 7.

[0262] Compared to Example 7, Comparative Example 2 prepared a high-temperature resistant polyamide resin without the addition of 2,2'-(1,3-phenylene)-dioxazoline. Since 2,2'-(1,3-phenylene)-dioxazoline acts as a compatibilizer, it effectively improves the interfacial bonding performance between the organic carbon nanotubes and the high-temperature resistant polyamide resin. The oxazoline groups in this compound can simultaneously react chemically with the functional groups on the surface of the carbon nanotubes and the terminal amino groups of the polyamide resin, forming a stable chemical bond network, thereby significantly enhancing the compatibility and interfacial adhesion strength between the two phases. Therefore, the tensile strength and notched impact resistance of Comparative Example 2 are lower than those of Example 7.

[0263] Compared to Example 7, Comparative Example 3 prepared a high-temperature resistant polyamide resin without the addition of organic carbon nanotubes. Because organic carbon nanotubes significantly improve the electromagnetic shielding performance of the high-temperature resistant polyamide resin through a multi-dimensional synergistic mechanism, their surface modifications (such as amylation) optimize dispersibility, construct a continuous conductive network in the matrix, achieve electromagnetic wave reflection loss through free electron migration, and enhance absorption loss through polarization relaxation induced by tube wall defects and functional groups. The stable matrix of the high-temperature resistant polyamide maintains network integrity, while interfacial hydrogen bonding reduces signal transmission, ultimately achieving efficient electromagnetic shielding through a synergistic effect of "conductivity-dissipation-interface." Therefore, Comparative Example 3 does not possess microwave absorption properties.

[0264] Compared to Example 7, Comparative Example 4 prepared a high-temperature resistant polyamide resin without the addition of benzoic acid. Since benzoic acid is a monofunctional compound, its carboxyl group undergoes a condensation reaction with the terminal amino group of the high-temperature resistant polyamide during melt polymerization. Because this reaction causes the benzoic acid molecule to lose its ability to continue participating in chain growth, it can act as a molecular weight regulator, effectively controlling the polymer's molecular weight (intrinsic viscosity) by limiting the extension of the polymer chain. Therefore, the intrinsic viscosity of Comparative Example 4 is higher than that of Example 7.

[0265] Compared to Example 7, Comparative Example 5 prepared a high-temperature resistant polyamide resin without the addition of a high-temperature antioxidant. Due to the steric hindrance effect of the four methyl groups on the piperidine ring, the high-temperature antioxidant N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide exhibits excellent thermal stability under high-temperature conditions. Its steric hindrance structure can efficiently capture free radicals, effectively delaying material aging. During the synthesis of the high-temperature resistant polyamide resin, the amide groups of this compound can react with the resin end groups, acting as end-capping agents to precisely control the molecular weight, and also permanently anchoring to the polymer backbone through chemical bonding, thereby significantly improving the compatibility of the copolymer. This dual-action mechanism not only endows the material with durable antioxidant properties but also improves the dyeing properties of the copolymer, achieving synergistic optimization of functionality and processability. Therefore, the tensile strength and notched impact strength of Comparative Example 5 are lower than those of Example 7.

[0266] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0267] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high-temperature resistant polyamide resin, characterized in that, It is prepared from the following raw materials in parts by weight: 102.2 parts of 1,5-pentanediamine Terephthalic acid 66.5–99.7 parts, Glutaric acid 52.9–79.3 parts, Contains 30-60 parts of phosphoramide salt, 5.5–7.5 parts of 2,2'-(1,3-phenylene)-dioxazoline 23–31 parts of organic carbon nanotubes, 5-7 parts benzoic acid 0.5–1.5 parts of high-temperature resistant antioxidant; The 1,5-pentanediamine is in an equimolar ratio with terephthalic acid and glutaric acid; and / or, the phosphoramide salt is obtained by a salt-forming reaction of 2-carboxyethylphenyl hypophosphite and 1,5-pentanediamine; and / or, the organic carbon nanotubes are obtained by organic modification of carbon nanotubes with γ-aminopropyltriethoxysilane; and / or, the high-temperature antioxidant is N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

2. The high-temperature resistant polyamide resin according to claim 1, characterized in that, It is prepared from the following raw materials in parts by weight: 102.2 parts of 1,5-pentanediamine Terephthalic acid 74.8–91.4 parts, Glutaric acid 59.5–72.7 parts, Contains 35-55 parts of phosphoramide salt. 2,2'-(1,3-phenylene)-dioxazoline 5.8–7.2 parts, 25–29 parts of organic carbon nanotubes, Benzoic acid 5.3–6.7 parts, 0.7 to 1.3 parts of high-temperature resistant antioxidant.

3. The high-temperature resistant polyamide resin according to claim 2, characterized in that, It is prepared from the following raw materials in parts by weight: 102.2 parts of 1,5-pentanediamine 78.1–88 parts of terephthalic acid Glutaric acid 62.1–70 parts, Contains 40-50 parts of phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline 6.1–6.9 parts, 26–28 parts of organic carbon nanotubes, Benzoic acid 5.6–6.4 parts, 0.8 to 1.2 parts of high-temperature resistant antioxidant.

4. The high-temperature resistant polyamide resin according to any one of claims 1 to 3, characterized in that, The preparation method of the phosphoramide salt includes the following steps: 214.16 g of 2-carboxyethylphenyl hypophosphite and 102.18 g of 1,5-pentanediamine are added to a stirred polymerization reactor, followed by the addition of 150 mL to 200 mL of deionized water. The reactor is then evacuated for 2 to 6 minutes and purged with nitrogen for 2 to 6 minutes. This cycle is repeated 3 to 5 times, and the system pressure inside the stirred polymerization reactor is controlled at 0.1 MPa to 0.3 MPa. The stirred polymerization reactor is then sealed and heated to 85°C to 95°C for 0.5 to 1.5 hours, with the stirring speed controlled at 50 r / min to 100 r / min. After the salt formation reaction is carried out for 1 to 2 hours, the reaction is completed, the pressure inside the reactor is reduced to 0.1 MPa, the material is discharged, and vacuum dried.

5. The high-temperature resistant polyamide resin according to any one of claims 1 to 3, characterized in that, The preparation method of the organic carbon nanotubes includes the following steps: 100 g of carbon nanotubes and 2.5 g to 3.5 g of γ-aminopropyltriethoxysilane are added to a high-speed stirrer and stirred at room temperature for 6 min to 10 min to obtain the product.

6. The high-temperature resistant polyamide resin according to any one of claims 1 to 3, characterized in that, The average diameter of the carbon nanotubes in the organic carbon nanotubes is 8 nm to 10 nm, and their structure is array-type.

7. The method for preparing the high-temperature resistant polyamide resin according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Vacuum-dried 1,5-pentanediamine, terephthalic acid and glutaric acid are added to a stirred polymerization reactor, along with phosphoramide salt, 2,2'-(1,3-phenylene)-dioxazoline, organic carbon nanotubes, benzoic acid, high-temperature antioxidant and appropriate amount of water. Then, the reactor is evacuated for 2 min to 6 min and purged with nitrogen for 2 min to 6 min. This cycle is repeated 3 to 5 times, and the system pressure in the stirred polymerization reactor is controlled to be 0.1 MPa to 0.3 MPa. (2) Adjust the stirring speed of the stirred polymerization reactor to 20 r / min to 40 r / min, and heat the stirred polymerization reactor to 279℃ to 283℃ in a closed and uniform manner for 2 to 4 hours. When the temperature of the stirred polymerization reactor reaches 211℃, release the gas to 1.95 MPa and maintain the pressure at 1.95 MPa. After reacting for 1 to 2 hours, release the gas to atmospheric pressure and raise the temperature to 313℃ to 317℃. Continue to react for 1 to 2 hours, and maintain the constant temperature and vacuum for 15 to 45 minutes. When the reaction is completed, add nitrogen gas when discharging to obtain the product.

8. The method for preparing the high-temperature resistant polyamide resin according to claim 7, characterized in that, In step (1), the vacuum is drawn for 3 min to 5 min, and nitrogen is purged for 3 min to 5 min. This cycle is repeated 3 to 5 times to control the system pressure inside the stirred polymerization reactor to be 0.15 MPa to 0.25 MPa.

9. The method for preparing the high-temperature resistant polyamide resin according to claim 7, characterized in that, In step (2), the stirring speed of the stirred polymerization reactor is adjusted to 25 r / min to 35 r / min. The stirred polymerization reactor is heated to 280℃ to 282℃ in a closed and uniform manner for 2.5 hours to 3.5 hours. When the temperature of the stirred polymerization reactor reaches 211℃, the pressure is released to 1.95 MPa and maintained at 1.95 MPa. After reacting for 1.2 hours to 1.8 hours, the pressure is released to atmospheric pressure, and the temperature is raised to 314℃ to 316℃. The reaction continues for 1.2 hours to 1.8 hours. The temperature is kept constant and the vacuum is continuously applied for 20 minutes to 40 minutes. When the reaction ends, nitrogen is added when discharging the product to obtain the final product.

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