High-temperature-resistant nylon continuous melt polymerization method and high-temperature-resistant nylon

Abstract

The invention discloses a high-temperature-resistant nylon continuous melt polymerization method and high-temperature-resistant nylon, and the continuous melt polymerization method comprises the following steps: (1) adding a catalyst, semi-aromatic salt and desalted water into a polymerization kettle, or adding the catalyst, semi-aromatic salt, PA66 salt and desalted water, and carrying out prepolymerization reaction to obtain a prepolymer; (2) carrying out spray drying on the obtained prepolymer to obtain a powdery prepolymer; and (3) carrying out solid phase polycondensation tackifying reaction on the powdery prepolymer to obtain the high-temperature-resistant nylon. According to the spray drying method, moisture can be rapidly removed, compared with a traditional drying method, energy consumption can be remarkably reduced, energy efficiency can be improved, oxidation or hydrolysis reaction caused by moisture can be effectively avoided, and therefore the color stability of the product is kept; the prepolymer can keep good fluidity in the drying process, performance fluctuation caused by excessive drying or non-uniform drying is avoided, meanwhile, the low moisture content of the prepolymer can be kept, and it is ensured that follow-up reaction is carried out smoothly.

Description

Technical Field

[0001] The invention belongs to the field of nylon continuous melt polymerization method, and in particular relates to a high-temperature resistant nylon continuous melt polymerization method and high-temperature resistant nylon. Background Art

[0002] High temperature resistant nylon is a type of engineering plastic with excellent heat resistance, which is widely used in various engineering fields under high temperature environment. It has high rigidity and strength, and can maintain excellent dimensional accuracy and stability under high temperature conditions, especially its physical properties under high temperature. Therefore, high temperature resistant nylon performs well in thermal, electrical, physical and chemical resistance. Common high temperature resistant nylon resins include PA6T, PA9T, PA10T and their copolymers.

[0003] At present, the production process of high temperature resistant nylon generally adopts the two-step method of intermittent reactor prepolymerization and solid phase viscosity enhancement. Although this process can guarantee the performance of the product to a certain extent, there are still many problems in practical application. First, the production process of the prepolymer requires drying and crushing operations, which not only increases energy consumption, but also significantly reduces production efficiency; secondly, the solid phase polymerization reaction time is relatively long, which further delays the production progress; in addition, the temperature control and time control during the reaction process are complicated, which easily leads to unstable product quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a continuous melt polymerization method for high-temperature resistant nylon and high-temperature resistant nylon. The continuous preparation method of the present invention not only simplifies the preparation process of high-temperature resistant nylon, reduces the cumbersome steps of solid-liquid separation, drying and crushing in the traditional process, but also significantly improves the quality stability of the product; at the same time, the present invention effectively reduces production energy consumption and improves production efficiency, has broad industrial production application prospects, and is suitable for large-scale production of high-temperature resistant nylon resin.

[0005] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is: A high temperature resistant nylon continuous melt polymerization method comprises the following steps: (1) Adding a catalyst, a semi-aromatic salt and desalted water, or adding a catalyst, a semi-aromatic salt, a PA66 salt and desalted water into a polymerization kettle, and performing a prepolymerization reaction to obtain a prepolymer; (2) spray drying the obtained prepolymer to obtain a powdered prepolymer; (3) The powdered prepolymer is subjected to a solid phase polycondensation and viscosity-increasing reaction to obtain high temperature resistant nylon.

[0006] The prepolymer is converted into a powder form through spray drying, which eliminates the complicated solid-liquid separation, drying and crushing steps in the traditional process, which not only simplifies the production process, but also reduces the complexity of operation and equipment; spray drying controls parameters such as airflow and temperature to quickly remove moisture. Compared with traditional drying methods, it can significantly reduce energy consumption, improve energy efficiency, and avoid oxidation or hydrolysis reactions caused by moisture to the greatest extent, thereby maintaining the color stability of the product; the prepolymer of the present invention can maintain good fluidity during the drying process, avoid performance fluctuations caused by excessive drying or uneven drying, and at the same time maintain a low moisture content of the prepolymer to ensure smooth subsequent reactions.

[0007] Furthermore, during the prepolymerization reaction in step (1), the pressure in the polymerization kettle is increased from 0.5-1.0 Mpa to 1.8-3.0 Mpa; in step (2), the prepolymer under high pressure in the polymerization kettle is introduced into a pressure spray dryer for spray drying.

[0008] Furthermore, in the step (2), after the prepolymer under high pressure is introduced into the pressure spray dryer, the pressure is first released, and after the pressure release is completed, spray drying is performed; Preferably, the pressure is released to 0.5-0.8 Mpa in 45-120 min.

[0009] The main function of the pressure relief process is to reduce the moisture content in the system, and to balance the molecular weight growth rate of the polymer by controlling the rate of pressure drop. The pressure relief process of the present invention is relatively slow, so that the viscosity of the prepolymer can be steadily increased, avoiding sudden viscosity surges. This gradual pressure regulation helps to optimize the growth rhythm of the molecular chain, prevent the molecular chain from extending rapidly due to excessive water removal, causing a sharp increase in viscosity, and thus affecting the fluidity and transportation performance of the material.

[0010] During the slow pressure relief process, the prepolymer still maintains a certain fluidity, so that it can be smoothly transported to the spray dryer. Appropriate fluidity is crucial for the subsequent transportation, drying and solid phase viscosity increase process. Once the prepolymer viscosity is too high, it may cause the transportation pipeline to be blocked or material to be retained, affecting the continuity of production. Therefore, it is of great significance to reasonably control the pressure relief rate to ensure that the prepolymer has good fluidity while reaching the target viscosity, which is of great significance to improving the stability and efficiency of the entire process.

[0011] Furthermore, in step (2), the drying temperature of the spray drying is 100-220° C., and the gas medium is an inert gas, such as nitrogen, helium, or argon.

[0012] Too high drying temperature will cause polymer degradation and affect the molecular weight and mechanical properties of the product. By limiting the drying temperature within the range of 100-220°C, it can effectively avoid damage to the polymer structure caused by excessive temperature and ensure stable product quality.

[0013] Furthermore, in the step (3), the powdered prepolymer is transported to a continuous fluidized bed for solid phase polycondensation and viscosity enhancement to obtain a high temperature resistant nylon powder.

[0014] Furthermore, the continuous fluidized bed is a hot inert gas flow with a temperature of 230 to 280° C. and a residence time of 2 to 5 hours.

[0015] The continuous fluidized bed uses a hot inert gas flow (such as nitrogen) to uniformly heat the powdered prepolymer, thereby promoting the solid-phase polycondensation viscosity-increasing reaction. Compared with traditional solid-phase viscosity-increasing methods (such as static solid-phase polymerization or vacuum drum method), the fluidized bed has higher heat and mass transfer rates, greatly improving the growth rate of polymer molecular weight and effectively shortening the time required for solid-phase polycondensation. The viscosity-increasing reaction can be completed in a short residence time of only 2h to 5h, while the traditional vacuum drum process often takes 6 to 12 hours or even longer, and the production efficiency is significantly improved.

[0016] In the continuous fluidized bed system, the powdered prepolymer is evenly suspended and heated under the action of the hot inert gas flow, making its temperature distribution more uniform, effectively avoiding the problems of local overheating and uneven temperature gradient. In contrast, the traditional solid phase viscosity increasing method (such as fixed bed or vacuum drum) may lead to large differences in the degree of polymerization of different particles due to low heat transfer efficiency and uneven heat distribution. Some particles may affect the uniformity of the molecular weight distribution of the final product due to insufficient reaction. In the continuous fluidized bed, all powdered particles are in a uniform suspension environment of hot nitrogen gas flow, ensuring that the entire batch of products has a stable and consistent molecular weight distribution, thereby improving the overall performance and quality consistency of the material.

[0017] In addition, the continuous fluidized bed uses a hot inert gas flow (such as nitrogen) to perform solid-phase polycondensation in an oxygen-free environment, which fundamentally inhibits the oxidative degradation and color change of the polymer. In contrast, traditional solid-phase viscosity-increasing methods (such as air drying or vacuum drum method) may still cause oxidation reactions even in a low-oxygen environment due to long-term exposure to high temperatures, causing the polymer to turn yellow. While the continuous fluidized bed technology performs high-temperature solid-phase viscosity-increasing, it effectively reduces the risk of oxidation through the continuous protection of an inert gas flow, making the final product have a lower yellow index and more stable color, thereby improving the appearance quality of the product.

[0018] During the solid phase polycondensation process, the polymer may have a small amount of residual moisture and low molecular weight by-products (such as water, amide, etc.). If these by-products are not discharged in time, they may affect the viscosity and mechanical properties of the final product. Continuous fluidized bed technology relies on the efficient heat and mass transfer characteristics of hot air flow to quickly remove moisture and low molecular weight volatiles, ensuring that the solid phase polycondensation process is steadily promoted in the direction of high molecular weight, thereby increasing the relative viscosity of the polymer (such as from 1.9 to 2.1 or higher). In contrast, the traditional static solid phase thickening method has a slow water removal rate, which can easily lead to the accumulation of by-products in local areas, affecting the quality stability and final performance of the polymer.

[0019] It is worth noting that traditional solid-phase thickening methods, such as static solid-phase polymerization or vacuum drum processes, usually use batch production, which not only has low production efficiency, but also has large fluctuations in product quality between different batches. The continuous fluidized bed thickening process can achieve continuous production, that is, the powdered prepolymer can continuously enter the fluidized bed and be continuously discharged after thickening, avoiding the problems of shutdown, loading and unloading materials in traditional batch processes. This continuous production mode greatly improves production efficiency, reduces production costs, and ensures the stability of product quality, making large-scale industrial production of high-temperature resistant nylon possible.

[0020] Furthermore, in the step (3), the high temperature resistant nylon powder is input into a twin-screw extruder for continuous melt extrusion to obtain high temperature resistant nylon; Preferably, the temperature of the continuous melt extrusion is 300 to 340° C., the vacuum pressure is -0.08 to -0.10 MPa, the screw speed is 200 to 350 rpm, and the residence time is 40 to 90 s.

[0021] Through a series of processes such as prepolymerization reaction in a polymerization kettle, spray drying, and fluidized bed solid phase viscosity enhancement, high-temperature resistant nylon powder was successfully prepared. After entering the twin-screw extruder, the high-temperature resistant nylon powder was melted and sheared at high temperature to obtain more uniform mixing and plasticization, converting the granular powder into uniform resin, thus avoiding unstable performance caused by uneven materials.

[0022] Secondly, after the melt extrusion of the twin-screw extruder, this process not only helps the uniform mixing and full plasticization of the materials, but also promotes the amide exchange reaction in the melt through the action of high temperature and high shear force; the occurrence of the amide exchange reaction allows the molecular weight to further increase during the polymerization process, while optimizing the molecular weight distribution of the polymer, making it more uniform and reducing the distribution coefficient, thereby improving the mechanical properties of the material. In addition, the twin-screw extrusion process promotes the stability of the polymer system while ensuring full mixing, so that the mechanical properties of the resulting material have been further improved.

[0023] In addition, the melt extrusion of the twin-screw extruder at high temperature can also effectively remove residual bubbles and volatiles in the material. Although some moisture and gas have been removed after the powder has been spray-dried and fluidized bed treated, the residual gas and moisture can be completely removed in the twin-screw extruder due to the vacuum environment and high shear force. This can not only reduce the formation of bubbles and avoid the formation of holes or uneven structures in the final product, but also further increase the density of the resin, thereby improving the mechanical properties and thermal stability of the final product.

[0024] Furthermore, during the prepolymerization reaction of step (1), the temperature in the polymerization kettle is increased in stages from 170°C to 195°C to 250°C to 280°C; Preferably, the temperature is first raised to 170° C. to 195° C. for reaction for 0.5 h to 2 h, then raised to 200° C. to 240° C. for reaction for 1 h to 4 h, and then raised to 250° C. to 280° C. for reaction for 1 h to 3 h.

[0025] Furthermore, during the prepolymerization reaction of step (1), the temperature is first raised to 170°C to 195°C for reaction for 0.5 h to 2 h, the water is drained to keep the pressure stable at 0.5-1.0 MPa, the temperature is continued to be raised to 200°C to 240°C, the pressure is raised to 1.8 to 3.0 MPa, the reaction is carried out for 1 h to 4 h, and then the temperature is continued to be raised to 250°C to 280°C for reaction for 1 h to 3 h.

[0026] In the initial temperature reaction stage of 170℃~195℃, nylon salt first undergoes amidation reaction and generates polymers with lower molecular weight through addition reaction. During this process, the reaction system is under positive pressure conditions, which effectively inhibits the volatilization of diamines produced during the decomposition of nylon salts and ensures that they remain in the system, thereby maintaining the stoichiometric balance of carboxyl and amino groups. The temperature control design at this stage helps the initial reaction and cross-linking of the monomers, ensures the smooth progress of the polymerization process, and avoids unnecessary side reactions caused by excessive temperature.

[0027] Entering the medium temperature 200℃~240℃ reaction stage, the reaction pressure is further increased, which promotes the condensation reaction of nylon oligomers and further grows the molecular chain. The reaction in this stage is relatively complete, which can effectively promote the gradual extension of the molecular chain and increase the molecular weight of the polymer. At the same time, it optimizes the controllability of the system, prevents the degradation of the polymer due to excessive temperature increase, and ensures the stable quality of the final product.

[0028] In the high temperature 250℃~280℃ reaction stage, the system is under high temperature and high pressure conditions, which further promotes the polycondensation reaction and amide exchange reaction. This stage is crucial, which can significantly improve the molecular weight and distribution uniformity of the prepolymer, optimize the viscosity and structural stability of the polymer, and thus ensure that the final high temperature resistant nylon product has excellent mechanical properties and thermal stability.

[0029] By increasing the temperature in stages, the reaction process can gradually transition to a higher temperature, avoiding polymer degradation or uneven reaction caused by excessively high temperatures, thereby ensuring the uniformity and high performance of the product.

[0030] If the temperature in the polymerization kettle is directly raised to 250℃~280℃, the polymer will undergo thermal degradation or oxidation reaction, produce unnecessary by-products, and affect the color, molecular weight, viscosity and other properties of the final product. Staged heating reduces the high temperature exposure time by gradually controlling the temperature, making the polymerization process more gentle and effectively avoiding side reactions at excessively high temperatures.

[0031] The present invention also provides a high temperature resistant nylon, which is prepared by the polymerization method described in any one of the above technical schemes. The high temperature resistant nylon has a yellow index of 7.2 to 8.5, a relative viscosity of 1.9 to 2.6, a tensile strength of 85 to 113 MPa, and a bending strength of 132 to 164 MPa.

[0032] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art.

[0033] The introduction of the spray drying step of the present invention allows the prepolymer to be directly converted into a powder form, eliminating the cumbersome processes of solid-liquid separation, drying and crushing in the traditional process, thereby greatly reducing the energy consumption in the production process and simplifying the equipment configuration and operation process; the powdered prepolymer is passed through high-efficiency equipment such as a continuous fluidized bed to carry out a solid-phase polycondensation thickening reaction, thereby improving the efficiency of the thickening reaction, ensuring the uniformity of the mechanical properties and molecular weight of the polymer, and further improving the stability of the product.

[0034] The present invention adopts treatment processes such as spray drying and fluidized bed solid phase thickening that can be completed in a short time, and the removal of moisture and volatiles are more efficient, which avoids the prepolymer from being exposed to high temperature for too long, effectively reduces the occurrence of oxidation reactions, and improves the color stability of the polymer. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with an embodiment. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0036] The present invention will be related to the product color, relative viscosity, melting point, mechanical properties of the test method as follows: Yellowness index determination: Determined in accordance with GB / T 39822-2021 (Determination of the yellowness index of plastics and its change value).

[0037] Relative viscosity test conditions: The relative viscosity of the solution after dissolving high temperature resistant nylon in 98% concentrated sulfuric acid, the test temperature is 25°C, the concentration is 0.01g / ml, and the test is carried out in accordance with ISO 307 standard.

[0038] Melting point: Using the DSC method, weigh 5-8 mg of the sample, and in a nitrogen atmosphere, heat from room temperature to 400°C at a rate of 20°C / min, hold for 5 minutes, then cool to room temperature at a rate of 20°C / min, and then heat to 400°C at a rate of 10°C / min. The endothermic peak temperature at this time is the melting point of the polymer.

[0039] Mechanical property test: The prepared high temperature resistant nylon injection molding test specimens were tested for tensile strength according to GB / T1040.2 standard, for flexural strength and flexural modulus according to GB / T9341-2008 standard, and for simply supported beam impact strength according to GB / T1043.1 standard.

[0040] Unless otherwise specified, the experimental materials used in the present invention were purchased from biochemical reagent companies.

[0041] Embodiment 1, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) Add 60 parts of PA6T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water into the polymerization reactor, and fill with inert gas N 2 The air in the polymerization kettle was replaced, the air was inflated and pressurized to 0.8 MPa, heated and stirred, the temperature was raised to 180°C for reaction for 1.5 h, and the pressure was kept stable by draining; the temperature was further raised to 225°C, the pressure was kept at 2.2 MPa, and the reaction was continued for 3 h; the temperature was further raised to 275°C, and the reaction was continued for 2 h to obtain PA6T / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa within 60 min. After the pressure release is completed, spray drying is started at a drying temperature of 150° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 260° C. and the residence time of the powdered prepolymer is 3 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 330°C, the vacuum pressure is -0.08MPa, the screw speed is 280rpm, and the residence time is 80s to obtain PA6T / 66 chips.

[0042] Embodiment 2, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 68 parts of PA6T salt, 38 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 184°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 230°C, the pressure was kept at 2.2 MPa, and the reaction was continued for 3 h; the temperature was further raised to 260°C, and the reaction was continued for 2 h to obtain PA6T / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.6 MPa within 45 min. After the pressure release is completed, spray drying is started at a drying temperature of 150° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow, the temperature is 260° C., and the residence time is 3 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 330°C, the vacuum pressure is -0.08MPa, the screw speed is 280rpm, and the residence time is 80s to obtain PA6T / 66 chips.

[0043] Embodiment 3, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 43 parts of PA6T salt, 40 parts of PA6I salt, 0.5 parts of sodium pyrophosphate and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 182°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 232°C, the pressure was kept at 2.8 MPa, and the reaction was continued for 3 h; the temperature was further raised to 262°C, and the reaction was continued for 2.2 h to obtain PA6T / 6I prepolymer; (2) The prepolymer under high pressure obtained in step (1) is fed into a pressure spray dryer and slowly depressurized to 0.5 MPa within 80 min. After the depressurization is completed, spray drying is started. The drying temperature is 130° C. and the gas medium is nitrogen. A powdered prepolymer is obtained; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 272° C. and the residence time of the powdered prepolymer is 2.5 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 325°C, the vacuum pressure is -0.08 MPa, the screw speed is 300 rpm, and the residence time is 70 s to obtain PA6T / 6I chips.

[0044] Embodiment 4, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 60 parts of PA6T salt, 20 parts of PA6I salt, 16 parts of PA66 salt, 0.5 parts of triphenyl hypophosphite and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 180°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 231°C, the pressure was kept at 2.2 MPa, and the reaction was continued for 3 h; the temperature was further raised to 263°C, and the reaction was continued for 1.5 h to obtain PA6T / 6I / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa within 105 min. After the pressure release is completed, spray drying is started at a drying temperature of 180° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas in the continuous fluidized bed is a hot nitrogen flow at a temperature of 255° C. and a residence time of 4 hours, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 340°C, the vacuum pressure is -0.08 MPa, the screw speed is 245 rpm, and the residence time is 90 s to obtain PA6T / 6I / 66 chips.

[0045] Embodiment 5, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) Add 60 parts of PA6F salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water into the polymerization reactor, and fill it with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 180°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 231°C, the pressure was kept at 2.6 MPa, and the reaction was continued for 3 h; the temperature was further raised to 263°C, and the reaction was continued for 2 h to obtain PA6F / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa within 100 min. After the pressure release is completed, spray drying is started at a drying temperature of 120° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 280° C. and the residence time of the powdered prepolymer is 2.2 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 335°C, the vacuum pressure is -0.09 MPa, the screw speed is 320 rpm, and the residence time is 45 s to obtain PA6F / 66 chips.

[0046] Embodiment 6, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 57 parts of PA6F salt, 39 parts of PA6I salt, 0.25 parts of phosphoric acid and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 180°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 231°C, the pressure was kept at 1.9 MPa, and the reaction was continued for 3 h; the temperature was further raised to 273°C, and the reaction was continued for 1.2 h to obtain PA6F / 6I prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa over 65 min. After the pressure release is completed, spray drying is started at a drying temperature of 190° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 256° C. and the residence time of the powdered prepolymer is 3 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 328°C, the vacuum pressure is -0.08 MPa, the screw speed is 258 rpm, and the residence time is 75 s to obtain PA6F / 6I chips.

[0047] Embodiment 7, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) Add 59 parts of PA6I salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water into the polymerization reactor, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 186°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 231°C, the pressure was kept at 2.6 MPa, and the reaction was continued for 3 h; the temperature was further raised to 262°C, and the reaction was continued for 2 h to obtain PA6I / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa within 55 min. After the pressure release is completed, spray drying is started at a drying temperature of 195° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow, the temperature is 240° C., and the residence time is 3 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 310°C, the vacuum pressure is -0.1 MPa, the screw speed is 340 rpm, and the residence time is 65 s to obtain PA6I / 66 chips.

[0048] Embodiment 8, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 60 parts of PA6F salt, 19 parts of PA6I salt, 17 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 182°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 230°C, the pressure was kept at 2.4 MPa, and the reaction was continued for 3 h; the temperature was further raised to 264°C, and the reaction was continued for 2 h to obtain a PA6F / 6I / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa over 90 min. After the pressure release is completed, spray drying is started at a drying temperature of 110° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow, the temperature is 235° C., and the residence time is 5 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 330°C, the vacuum pressure is -0.08MPa, the screw speed is 280rpm, and the residence time is 80s to obtain PA6F / 6I / 66 chips.

[0049] Embodiment 9, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 60 parts of PA10T salt, 39 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water, and fill with inert gas N 2The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 183°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 228°C, the pressure was kept at 2.8 MPa, and the reaction was continued for 3 h; the temperature was further raised to 258°C, and the reaction was continued for 3 h to obtain PA6T / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer, and slowly releasing the pressure to 0.8 MPa after 105 min. After the pressure release is completed, spray drying is started at a drying temperature of 210° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 270° C. and the residence time of the powdered prepolymer is 3 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 330°C, the vacuum pressure is -0.08MPa, the screw speed is 300rpm, and the residence time is 75s to obtain PA6T / 66 chips.

[0050] Embodiment 10 This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 57 parts of PA10I salt, 48 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 187°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 229°C, the pressure was kept at 1.8 MPa, and the reaction was continued for 3 h; the temperature was further raised to 255°C, and the reaction was continued for 2.5 h to obtain a PA10I / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa over 50 min. After the pressure release is completed, spray drying is started at a drying temperature of 140° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 260° C. and the residence time of the powdered prepolymer is 4.5 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 340°C, the vacuum pressure is -0.08MPa, the screw speed is 350rpm, and the residence time is 90s to obtain PA10I / 66 chips.

[0051] Embodiment 11, This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 57 parts of PA12T salt, 47 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 180°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 226°C, the pressure was kept at 2.2 MPa, and the reaction was continued for 3 h; the temperature was further raised to 275°C, and the reaction was continued for 1.5 h to obtain a PA12T / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa over 60 min. After the pressure release is completed, spray drying is started at a drying temperature of 165° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 255° C. and the residence time of the powdered prepolymer is 5.5 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 315°C, the vacuum pressure is -0.08MPa, the screw speed is 315rpm, and the residence time is 80s to obtain PA12T / 66 chips.

[0052] Embodiment 12 This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) In the polymerization reactor, add 60 parts of PA10T salt, 40 parts of PA10I salt, 0.5 parts of sodium hypophosphite and desalted water, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 186°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 230°C, the pressure was kept at 2.6 MPa, and the reaction was continued for 3 h; the temperature was further raised to 280°C, and the reaction was continued for 1 h to obtain PA10T / 10I prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa over 70 min. After the pressure release is completed, spray drying is started at a drying temperature of 187° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 270° C. and the residence time of the powdered prepolymer is 2.5 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder, wherein the temperature of continuous melt extrusion is 340°C, the vacuum pressure is -0.08 MPa, the screw speed is 260 rpm, and the residence time is 90 s to obtain PA10T / 10I chips.

[0053] Embodiment 13 This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) Add 60 parts of PA9T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water into the polymerization reactor, and fill it with inert gas N 2 The air in the polymerization reactor was replaced, the reactor was inflated and pressurized to 0.8 MPa, heated and stirred, and the temperature was raised to 184°C for reaction for 1.5 h, and the pressure was kept stable by draining the water; the temperature was further raised to 229°C, the pressure was kept at 3 MPa, and the reaction was continued for 3 h; the temperature was further raised to 259°C, and the reaction was continued for 2 h; and the PA9T / 66 prepolymer was obtained; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer, and slowly releasing the pressure to 0.8 MPa after 120 min, and starting spray drying after the pressure release, the drying temperature is 180° C., the gas medium is nitrogen, and a powdered prepolymer is obtained; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 260° C. and the residence time of the powdered prepolymer is 4.5 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 320°C, the vacuum pressure is -0.08 MPa, the screw speed is 315 rpm, and the residence time is 55 s to obtain PA9T / 66 chips.

[0054] Embodiment 14 The difference between this embodiment and embodiment 1 is that step (4) is not performed, and high temperature resistant nylon powder is directly prepared according to steps (1) to (3).

[0055] Embodiment 15 The difference between this example and Example 1 is that the "prepolymer preparation method" is different from step (1) of Example 1; specifically, in step (1) of this comparative example, after adding the raw materials into the polymerization kettle, the temperature is directly raised to 275° C. and the reaction is carried out for 6.5 hours.

[0056] Example 16 This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) Add 60 parts of PA6T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water into the polymerization reactor, and fill with inert gas N 2The air in the polymerization kettle was replaced, the air was inflated and pressurized to 0.5 MPa, heated and stirred, the temperature was raised to 170°C for reaction for 2 hours, and the pressure was kept stable by draining; the temperature was further raised to 200°C, the pressure was kept at 1.8 MPa, and the reaction was continued for 4 hours; the temperature was further raised to 250°C, and the reaction was continued for 3 hours to obtain PA6T / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa within 60 min. After the pressure release is completed, spray drying is started at a drying temperature of 100° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 230° C. and the residence time of the powdered prepolymer is 5 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 300°C, the vacuum pressure is -0.09 MPa, the screw speed is 200 rpm, and the residence time is 90 s to obtain PA6T / 66 chips.

[0057] Embodiment 17 This embodiment adopts the following steps to prepare high temperature resistant nylon: (1) Add 60 parts of PA6T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water into the polymerization reactor, and fill with inert gas N 2 The air in the polymerization reactor was replaced, the air was inflated and pressurized to 1 MPa, heated and stirred, the temperature was raised to 195°C for reaction for 0.5 h, and the pressure was kept stable by draining; the temperature was further raised to 240°C, the pressure was kept at 3.0 MPa, and the reaction was continued for 1 h; the temperature was further raised to 280°C, and the reaction was continued for 1 h to obtain PA6T / 66 prepolymer; (2) feeding the prepolymer under high pressure obtained in step (1) into a pressure spray dryer and slowly releasing the pressure to 0.8 MPa within 60 min. After the pressure release is completed, spray drying is started at a drying temperature of 220° C. and the gas medium is nitrogen to obtain a powdered prepolymer; (3) conveying the powdered prepolymer obtained in step (2) to a continuous fluidized bed, wherein the gas of the continuous fluidized bed is a hot nitrogen flow at a temperature of 280° C. and the residence time of the powdered prepolymer is 2 h, to obtain a high temperature resistant nylon powder; (4) The high temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The temperature of the twin-screw extruder for continuous melt extrusion is 340°C, the vacuum pressure is -0.10 MPa, the screw speed is 350 rpm, and the residence time is 40 s to obtain PA6T / 66 chips.

[0058] Comparative Example 1 The difference between this comparative example and Example 1 is that the "drying method" is different from step (2) of Example 1; specifically, in this comparative example, the prepolymer obtained in step (1) is blown-dried at 80°C, and after the surface moisture is dried, it is crushed. The crushed prepolymer is further sent to a vacuum oven and dried at 110°C until the water content is less than 800ppm, and then the material is further crushed to obtain a powdered prepolymer with a particle size of less than 0.5mm.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that the "solid phase polycondensation viscosity enhancement" method is different from step (3) of Example 1; specifically, this comparative example adopts a vacuum drum method to carry out the solid phase polycondensation reaction, the reaction temperature is 260°C, and the residence time is 8h.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is only the pressure relief speed. This comparative example relieves the pressure to 0.8 MPa within 5 minutes.

[0061] The main function of the pressure relief process is to reduce the moisture content in the system and balance the molecular weight growth rate of the polymer by controlling the rate of pressure drop. In Example 1, the pressure relief process is relatively slow (60min), so that the viscosity of the prepolymer can gradually increase without a sudden viscosity surge. This gradual pressure release helps to control the growth rate of the molecular chain, avoiding the rapid growth of the polymer molecular chain and the sharp increase in viscosity due to excessive water removal, which affects the fluidity and transportation performance. During the slow pressure relief process of Example 1, the prepolymer still maintains a certain fluidity, so that it can be smoothly transported to the spray dryer. Appropriate fluidity is crucial for subsequent transportation, drying and solid phase thickening processes. If the viscosity of the prepolymer is too high, pipeline blockage or material retention will occur during transportation, affecting continuous production.

[0062] In contrast, Comparative Example 3 uses a rapid decompression to 0.8 MPa within 5 minutes, which causes the water in the system to evaporate rapidly in a short period of time. Due to the rapid removal of water, the polycondensation reaction in the system is instantly pushed to the high molecular weight direction, resulting in rapid growth of the molecular chain and a sharp increase in viscosity; the rapid increase in viscosity makes it difficult for the prepolymer to maintain good fluidity, and ultimately cannot be transported normally, and thus cannot complete subsequent processes such as spray drying, solid phase viscosity enhancement and twin-screw extrusion.

[0063] The present invention tests the properties of the high temperature resistant nylon obtained in Examples 1 to 15, Comparative Example 1 and Comparative Example 2, and the results are shown in Table 1 below: Table 1: Comparing Example 1 and Example 14, in Example 1, continuous melt extrusion by a twin-screw extruder is performed, which not only helps to evenly mix and fully plasticize the materials, but also promotes the amide exchange reaction in the melt through the action of high temperature and high shear force; the occurrence of the amide exchange reaction allows the molecular weight to further increase during the polymerization process, while optimizing the molecular weight distribution of the polymer, making it more uniform and reducing the distribution coefficient, thereby improving the mechanical properties of the material. In addition, the twin-screw extrusion process promotes the stability of the polymer system while ensuring sufficient mixing, so that the mechanical properties of the obtained material are further improved.

[0064] Although Example 14 has not been melt-extruded, its yellow index is 8.5, showing relatively low color change and good color stability compared with Comparative Examples 1 and 2. It can be seen that despite the lack of the melt-extrusion step, the effective removal of moisture and volatiles during spray drying and solid phase thickening plays a key role in reducing oxidation reactions. During the spray drying process, the moisture in the material is effectively removed, and the residual moisture will cause the polymer to hydrolyze during the heating process, further inducing oxidation reactions or color changes. The present invention uses spray drying to quickly dry the material, reducing the chemical reactions caused by moisture, thereby effectively controlling the occurrence of oxidation and maintaining good color stability. In addition, the conditions of the continuous fluidized bed solid phase thickening are relatively mild and the time is short, which can avoid excessive oxidation, so that the product maintains a low yellow index.

[0065] In Example 1, due to the high temperature and vacuum environment of the twin-screw extruder, volatiles, bubbles and moisture in the material are fully and effectively removed, oxidation reaction and pigment formation are minimized, and the yellow index of the product is kept low. In contrast, although Example 14 does not perform melt extrusion, the control of temperature and reaction conditions during the solid phase viscosity increase may not be sufficient to completely avoid color changes. Although the color change is not significant, there is still a certain gap compared to Example 1.

[0066] Comparing Example 1 with Comparative Example 1, the only difference between Comparative Example 1 and Example 1 is that the "drying method" is different from Example 1; Example 1 adopts two efficient process treatment methods, spray drying and continuous fluidized bed solid phase viscosity enhancement, which can not only remove moisture in a shorter time, but also effectively reduce the exposure time of the polymer under high temperature conditions, thereby effectively preventing the occurrence of oxidation reaction and maintaining a low yellow index.

[0067] In contrast, Comparative Example 1 uses a more traditional and time-consuming drying process. In step (2) of Comparative Example 1, the prepolymer is first treated under 80°C forced air drying, and after the surface moisture is evaporated, it is then dried in a vacuum oven at 110°C, and finally a small particle powder is obtained by crushing. Although this process also has an effect on moisture removal, the drying process is relatively slow, especially when forced air drying is performed at a lower temperature, which may result in the moisture not being completely removed during the long drying process. Even if the water content is further reduced by a vacuum oven, oxidation reactions may still occur on the surface and inside of the polymer due to the long-term drying exposure. Especially when drying at a higher temperature, the presence of oxygen leads to pigment formation and discoloration of the polymer, thereby significantly increasing the yellow index.

[0068] In Example 1, due to the use of spray drying and fluidized bed solid phase thickening and other treatment processes that are completed in a short time, the removal of moisture and volatiles are more efficient, avoiding the material from being exposed to high temperature for too long, thereby effectively reducing the occurrence of oxidation reactions. Relatively speaking, the drying process in Comparative Example 1 is relatively slow, and the exposure time is long, especially in the vacuum oven drying stage, the high temperature and long exposure time make it difficult to completely remove moisture and volatile substances, which accelerates the oxidation reaction to a certain extent, resulting in a significant increase in the yellow index.

[0069] Comparing Example 1 and Comparative Example 2, the only difference between Comparative Example 2 and Example 1 is the different "solid phase polycondensation viscosity enhancement" method; Comparative Example 2 adopts a vacuum drum process, and the temperature of its solid phase polycondensation reaction is 260°C, but the residence time is as long as 8 hours. A longer reaction time will cause the polymer to be exposed to a higher temperature for a longer time, and the oxidation reaction will intensify, and the oxidation reaction will cause the polymer to turn yellow.

[0070] In comparison, the continuous fluidized bed process used in Example 1 has a shorter residence time (3 hours) and the material is exposed to high temperature for a shorter time, thereby reducing the occurrence of oxidation reaction and effectively maintaining a low yellow index. The short reaction time and efficient gas-solid contact ensure the rapid removal of moisture and volatiles, avoiding color changes caused by oxidation.

[0071] The long reaction time of the vacuum drum process in Comparative Example 2 leads to uneven molecular weight distribution. As mentioned above, long-term high-temperature treatment easily causes uneven extension or degradation of molecular chains, resulting in a looser molecular structure of the polymer and more difficult viscosity control. The continuous fluidized bed process in Example 1, although shorter in time, can better control the molecular weight distribution and ensure stable viscosity due to its more uniform gas-solid contact and milder reaction conditions.

[0072] As can be seen from Table 1, the relative viscosity of Example 1 is 2.1, while the relative viscosity of Comparative Example 2 is 2.2, and the difference between the two is not large, but the mechanical properties of Example 1 are more superior. Although the relative viscosity of Comparative Example 2 is slightly higher, indicating that the molecular weight is slightly larger, the longer reaction time may lead to non-uniform viscosity, affecting the overall performance of the polymer.

[0073] Comparing Example 1 and Example 15, the gradual heating method of Example 1 can better control the structure of the polymer, so that its molecular chain grows evenly, thereby improving the mechanical properties. In contrast, Example 15 adopts direct heating to 275°C, which leads to uneven molecular structure and decreased mechanical properties, especially the decrease in tensile strength, bending strength and impact strength. Although the yellow index and melting point of the two are similar, the mechanical properties of Example 15 are reduced, indicating that the staged heating process is crucial to improving the mechanical properties and overall stability of the polymer, and the direct heating to high temperature may accelerate the degradation of the polymer and damage its mechanical properties.

[0074] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the present invention can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for continuous melt polymerization of high temperature resistant nylon, characterized in that: The following steps are involved: (1) Adding a catalyst, a semi-aromatic salt and desalted water, or adding a catalyst, a semi-aromatic salt, a PA66 salt and desalted water into a polymerization kettle, and performing a prepolymerization reaction to obtain a prepolymer; (2) spray drying the obtained prepolymer to obtain a powdered prepolymer; (3) The powdered prepolymer is subjected to a solid phase polycondensation and viscosity-increasing reaction to obtain high temperature resistant nylon.

2. A high temperature resistant nylon continuous melt polymerization method according to claim 1, characterized in that: During the prepolymerization reaction in step (1), the pressure in the polymerization kettle is increased from 0.5-1.0 Mpa to 1.8-3.0 Mpa. In step (2), the prepolymer under high pressure in the polymerization kettle is introduced into a pressure spray dryer for spray drying.

3. A high temperature resistant nylon continuous melt polymerization method according to claim 2, characterized in that: In the step (2), after the prepolymer under high pressure is introduced into the pressure spray dryer, the pressure is first released, and after the pressure is released, spray drying is performed; Preferably, the pressure is released to 0.5-0.8 Mpa in 45-120 min.

4. A high temperature resistant nylon continuous melt polymerization method according to any one of claims 1 to 3, characterized in that: In the step (2), the drying temperature of the spray drying is 100 to 220° C., and the gas medium is an inert gas.

5. A high temperature resistant nylon continuous melt polymerization method according to any one of claims 1 to 3, characterized in that: In the step (3), the powdered prepolymer is transported to a continuous fluidized bed for solid phase polycondensation and viscosity enhancement to obtain a high temperature resistant nylon powder.

6. A high temperature resistant nylon continuous melt polymerization method according to claim 5, characterized in that: The continuous fluidized bed is a hot inert gas flow with a temperature of 230 to 280° C. and a residence time of 2 to 5 hours.

7. A high temperature resistant nylon continuous melt polymerization method according to claim 6, characterized in that: In the step (3), the high temperature resistant nylon powder is input into a twin-screw extruder for continuous melt extrusion to obtain high temperature resistant nylon; Preferably, the temperature of the continuous melt extrusion is 300 to 340° C., the vacuum pressure is -0.08 to -0.10 MPa, the screw speed is 200 to 350 rpm, and the residence time is 40 to 90 s.

8. A high temperature resistant nylon continuous melt polymerization method according to any one of claims 1 to 7, characterized in that: During the prepolymerization reaction of step (1), the temperature in the polymerization kettle is increased in stages from 170°C to 195°C to 250°C to 280°C; Preferably, the temperature is first raised to 170° C. to 195° C. for reaction for 0.5 h to 2 h, then raised to 200° C. to 240° C. for reaction for 1 h to 4 h, and then raised to 250° C. to 280° C. for reaction for 1 h to 3 h.

9. A high temperature resistant nylon continuous melt polymerization method according to claim 8, characterized in that: During the prepolymerization reaction of step (1), the temperature is first raised to 170°C to 195°C for reaction for 0.5 h to 2 h, the water is drained to keep the pressure stable at 0.5-1.0 MPa, the temperature is continued to be raised to 200°C to 240°C, the pressure is raised to 1.8 to 3.0 MPa, the reaction is carried out for 1 h to 4 h, and then the temperature is continued to be raised to 250°C to 280°C for reaction for 1 h to 3 h.

10. A high temperature resistant nylon, characterized in that: The high temperature resistant nylon is prepared by the polymerization method according to any one of claims 1 to 9, and has a yellow index of 7.2 to 8.5, a relative viscosity of 1.9 to 2.6, a tensile strength of 85 to 113 MPa, and a flexural strength of 132 to 164 MPa.

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