A continuous melt polymerization method of high-temperature-resistant nylon and high-temperature-resistant nylon

Abstract

The application discloses a continuous melt polymerization method of high-temperature-resistant nylon and the high-temperature-resistant nylon, and the continuous melt polymerization method comprises the following steps: (1) adding a catalyst, a semi-aromatic salt and desalted water, or adding the catalyst, the semi-aromatic salt, a PA66 salt and the desalted water in a polymerization kettle to perform a prepolymerization reaction, so as to obtain a prepolymer; (2) performing spray drying on the obtained prepolymer, so as to obtain a powdery prepolymer; and (3) performing a solid-phase polycondensation tackifying reaction on the powdery prepolymer, so as to obtain the high-temperature-resistant nylon. The spray drying can rapidly remove water, compared with a traditional drying method, can significantly reduce energy consumption, improve energy efficiency, effectively avoid oxidation or hydrolysis reactions caused by water, and thus maintain color stability of the product; the prepolymer can maintain good fluidity during the drying process, avoid performance fluctuations caused by excessive drying or uneven drying, and meanwhile, the prepolymer can maintain a low water content, so as to ensure that subsequent reactions are smoothly performed.

Description

Technical Field

[0001] This invention belongs to the field of continuous melt polymerization methods for nylon, and more specifically, relates to a continuous melt polymerization method for high-temperature resistant nylon and high-temperature resistant nylon. Background Technology

[0002] High-temperature resistant nylon is a class of engineering plastics with excellent heat resistance, widely used in various engineering fields under high-temperature environments. It possesses high rigidity and strength, maintaining excellent dimensional accuracy and stability under high-temperature conditions, especially retaining its physical properties at high temperatures. Therefore, high-temperature resistant nylon exhibits outstanding performance in terms of thermal, electrical, physical, and chemical resistance. Common high-temperature resistant nylon resins include PA6T, PA9T, PA10T, and their copolymers.

[0003] Currently, the production process of high-temperature resistant nylon generally adopts a two-step method of batch reactor prepolymerization and solid-state thickening. Although this process can guarantee the performance of the product to a certain extent, there are still many problems in practical applications. First, the production of prepolymer requires drying and pulverizing operations, which not only increases energy consumption but also significantly reduces production efficiency. Second, the solid-state polymerization reaction takes a long time, further delaying the production progress. In addition, the temperature and time control during the reaction process are complex, which can easily lead to unstable product quality. Summary of the Invention

[0004] The technical problem to be solved by this 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 this invention not only simplifies the preparation process of high-temperature resistant nylon and reduces the cumbersome steps such as solid-liquid separation, drying and pulverization in the traditional process, but also significantly improves the quality stability of the product. At the same time, this invention effectively reduces production energy consumption and improves production efficiency, and has broad prospects for industrial production applications, and is suitable for the large-scale production of high-temperature resistant nylon resin.

[0005] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0006] A continuous melt polymerization method for high-temperature resistant nylon includes the following steps:

[0007] (1) Add catalyst, semi-aromatic salt and demineralized water to the polymerization reactor, or add catalyst, semi-aromatic salt, PA66 salt and demineralized water to carry out prepolymerization reaction to obtain prepolymer;

[0008] (2) The obtained prepolymer is spray-dried to obtain a powdered prepolymer;

[0009] (3) High-temperature resistant nylon is obtained by solid-phase polycondensation and thickening reaction of powdered prepolymer.

[0010] The prepolymer is converted into a powdery form through a spray drying process, which omits the complicated solid-liquid separation, drying and crushing steps in the traditional process, simplifies the production process, and reduces the complexity of operation and equipment; the spray drying rapidly removes the moisture by controlling the parameters such as airflow and temperature, can significantly reduce the energy consumption and improve the energy efficiency compared with the traditional drying method, and avoids the oxidation or hydrolysis reaction caused by the moisture to the greatest extent, thereby maintaining the color stability of the product; the prepolymer can maintain good fluidity during the drying process, avoids the performance fluctuation caused by excessive drying or uneven drying, and can maintain a low moisture content of the prepolymer, thereby ensuring the smooth subsequent reaction.

[0011] Further, in the prepolymerization process of 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.

[0012] Further, in step (2), after the prepolymer under high pressure is introduced into the pressure spray dryer, pressure relief is first performed, and then spray drying is performed after the pressure relief is completed.

[0013] Preferably, the pressure is relieved to 0.5-0.8 Mpa in 45-120 min.

[0014] The main role of the pressure relief process is to reduce the moisture content in the system, and the pressure drop rate is controlled to balance the molecular weight growth rate of the polymer. The pressure relief process of the application is relatively slow, so that the viscosity of the prepolymer can stably rise, avoiding sudden viscosity surge. This gradual pressure control helps to optimize the growth rate of the molecular chain, prevents the molecular chain from rapidly extending due to the rapid removal of moisture, causes the viscosity to rise sharply, and thus affects the flowability and delivery performance of the material.

[0015] During the slow pressure relief process, the prepolymer still maintains a certain fluidity, so that it can be smoothly delivered to the spray dryer. Suitable fluidity is crucial for subsequent delivery, drying and solid-phase thickening processes. Once the viscosity of the prepolymer is too high, it may cause pipeline blockage or material retention, affecting the continuity of production. Therefore, reasonable control of the pressure relief rate to ensure that the prepolymer has good fluidity while reaching the target viscosity is of great significance to improve the stability and efficiency of the entire process.

[0016] Further, in step (2), the drying temperature of the spray drying is 100-220 DEG C, and the gas medium is an inert gas, such as nitrogen, helium, argon.

[0017] Too high drying temperature will cause polymer degradation, affecting the molecular weight and mechanical properties of the product. By limiting the drying temperature in the range of 100-220℃, the damage to the polymer structure caused by too high temperature can be effectively avoided, ensuring the stable quality of the product.

[0018] Further, in step (3), the powdery prepolymer is transported to a continuous fluidized bed for solid-phase polycondensation and viscosity increase to obtain high-temperature-resistant nylon powder.

[0019] Further, the continuous fluidized bed is a hot inert gas stream with a temperature of 230-280℃ and a residence time of 2h-5h.

[0020] The continuous fluidized bed uses a hot inert gas stream (such as nitrogen) to uniformly heat the powdery prepolymer, thereby promoting the solid-phase polycondensation and viscosity increase reaction. Compared with traditional solid-phase viscosity increase methods (such as static solid-phase polymerization or vacuum drum method), the heat and mass transfer rates of the fluidized bed are higher, greatly improving the growth rate of the polymer molecular weight and effectively shortening the time required for solid-phase polycondensation. The viscosity increase reaction can be completed in only 2h-5h of short residence time, while the traditional vacuum drum process often takes 6-12 hours or even longer, significantly improving the production efficiency.

[0021] In the continuous fluidized bed system, the powdery prepolymer is uniformly suspended and heated under the action of the hot inert gas stream, making the temperature distribution more uniform and effectively avoiding the problems of local overheating and uneven temperature gradient. In contrast, traditional solid-phase viscosity increase methods (such as fixed bed or vacuum drum) may result in large differences in polymerization degree among different particles due to low heat transfer efficiency and uneven heat distribution, and some particles may not react enough, affecting the uniformity of the molecular weight distribution of the final product. In the continuous fluidized bed, all powdery particles are in a uniform suspension environment of hot nitrogen gas stream, 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.

[0022] In addition, the continuous fluidized bed uses a hot inert gas stream (such as nitrogen) to perform solid-phase polycondensation in an oxygen-free environment, fundamentally inhibiting the oxidative degradation and color change of the polymer. In contrast, traditional solid-phase viscosity increase methods (such as forced air drying or vacuum drum method) may still cause oxidation even in a low-oxygen environment due to long-term exposure at high temperature, resulting in yellowing of the polymer. The continuous fluidized bed technology, while performing high-temperature solid-phase viscosity increase, effectively reduces the risk of oxidation through the continuous protection of the inert gas stream, making the final product have a lower yellow index and more stable color, thereby improving the appearance quality of the product.

[0023] In the solid phase polycondensation process, the polymer can remain a small amount of moisture and low molecular weight byproducts (such as water, amide, etc.), which, if not removed in time, can affect the viscosity and mechanical properties of the final product. Continuous fluidized bed technology relies on the efficient heat transfer and mass transfer characteristics of hot gas flow, which can quickly remove moisture and low molecular volatile substances, ensuring that the solid phase polycondensation process is steadily pushed towards high molecular weight, thereby increasing the relative viscosity of the polymer (e.g. from 1.9 to 2.1 or higher). In contrast, the traditional static solid phase thickening method has a slower moisture removal rate, which can easily lead to the accumulation of byproducts in local areas, affecting the quality stability and final performance of the polymer.

[0024] 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 batches. The continuous fluidized bed thickening process can achieve continuous production, i.e. the powdered prepolymer can continuously enter the fluidized bed and be continuously discharged after thickening, avoiding the problems of stopping, loading and unloading materials in traditional batch processes. This continuous production mode greatly improves production efficiency, reduces production cost, and ensures the stability of product quality, making it possible to scale up the industrial production of high-temperature-resistant nylon.

[0025] Further, in the step (3), the high-temperature-resistant nylon powder is input into a double screw extruder for continuous melt extrusion to obtain the high-temperature-resistant nylon.

[0026] Preferably, the temperature for the continuous melt extrusion is 300-340°C, the vacuum pressure is -0.08 to -0.10 MPa, the screw rotation speed is 200-350 rpm, and the residence time is 40-90 s.

[0027] Through a series of processes such as prepolymerization in a polymerization kettle, spray drying, and fluidized bed solid phase thickening, high-temperature-resistant nylon powder is successfully prepared. After entering the double screw extruder, the high-temperature-resistant nylon powder can be uniformly mixed and plasticized through high-temperature melting and shearing, converting the granular powder into uniform resin and avoiding performance instability caused by uneven material.

[0028] Secondly, after melt extrusion by the double screw extruder, the process not only helps to uniformly mix and fully plasticize the material, but also promotes the amide exchange reaction in the melt through high temperature and high shear force. The occurrence of amide exchange reaction allows the molecular weight to further increase during polymerization, 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 double screw extrusion process ensures sufficient mixing while promoting the stability of the polymer system, resulting in further improvement in the mechanical properties of the obtained material.

[0029] In addition, the melt extrusion of the twin-screw extruder at high temperature can also effectively remove the residual bubbles and volatile substances in the material. After the powder is treated by spray drying and fluidized bed, although a part of the moisture and gas has been removed, in the twin-screw extruder, due to the vacuum environment and high shear force, the residual gas and moisture can be completely removed. This not only can reduce the formation of bubbles, avoid the formation of holes or uneven structure in the final product, but also can further improve the density of the resin, thereby improving the mechanical properties and thermal stability of the final product.

[0030] Further, in the prepolymerization process of step (1), the temperature in the polymerization kettle is increased from 170°C to 195°C in stages to 250°C to 280°C;

[0031] Preferably, the temperature is first increased to 170°C to 195°C for 0.5 h to 2 h, then increased to 200°C to 240°C for 1 h to 4 h, and then increased to 250°C to 280°C for 1 h to 3 h.

[0032] Further, in the prepolymerization process of step (1), the temperature is first increased to 170°C to 195°C for 0.5 h to 2 h, then increased to 200°C to 240°C for 1 h to 4 h, and then increased to 250°C to 280°C for 1 h to 3 h.

[0033] In the initial temperature 170°C to 195°C reaction stage, the nylon salt first undergoes amidation reaction and generates a lower molecular weight polymer through addition reaction. In this process, the reaction system is under positive pressure conditions, effectively inhibiting the volatilization of the diamine generated during the decomposition of the nylon salt, ensuring that it still remains in the system, thereby maintaining the stoichiometric ratio balance of the carboxyl and amino groups. The temperature control design of this stage helps the preliminary reaction and crosslinking of the monomer, ensuring the smooth progress of the polymerization process, while avoiding unnecessary side reactions caused by excessive temperature.

[0034] In the medium temperature 200°C to 240°C reaction stage, the reaction pressure is further increased to promote the polycondensation reaction of the nylon oligomers, allowing the molecular chain to further grow. This stage of reaction is relatively complete, which can effectively promote the gradual extension of the molecular chain, increase the molecular weight of the polymer, and optimize the controllability of the system, preventing the degradation of the polymer caused by excessive temperature rise, and ensuring the quality stability of the final product.

[0035] In the high-temperature 250℃-280℃ reaction stage, the system is in high-temperature and high-pressure conditions, which further promotes the progress of the polycondensation reaction and the amide exchange reaction. This stage is crucial, which can significantly improve the molecular weight of the prepolymer and the uniformity of its distribution, optimize the viscosity and structural stability of the polymer, thereby ensuring that the final high-temperature-resistant nylon product has excellent mechanical properties and thermal stability.

[0036] By staged temperature rising, the reaction process can gradually transition to a higher temperature, avoiding the degradation or uneven reaction of the polymer caused by excessively high temperature, thereby ensuring the uniformity and high performance of the product.

[0037] If the temperature in the polymerization kettle is directly increased to 250℃-280℃, it will cause thermal degradation or oxidation reaction of the polymer, producing unnecessary by-products, affecting the color, molecular weight, viscosity and other properties of the final product. The staged temperature rising gradually controls the temperature, reduces the time of high-temperature exposure, and makes the polymerization process more gentle, effectively avoiding side reactions at high temperature.

[0038] The application also provides a high-temperature-resistant nylon prepared by the polymerization method described in any of the above technical solutions. The high-temperature-resistant nylon has a yellow index of 7.2-8.5, a relative viscosity of 1.9-2.6, a tensile strength of 85-113 MPa, and a bending strength of 132-164 MPa.

[0039] Compared with the prior art, the application has the following beneficial effects after using the above technical solutions.

[0040] The introduction of the spray drying step in the application allows the prepolymer to be directly converted into a powdery form, eliminating the complicated processes such as solid-liquid separation, drying and crushing in traditional processes, thereby greatly reducing the energy consumption in the production process and simplifying the equipment configuration and operation process. The powdery prepolymer is subjected to solid-phase polycondensation and viscosity-increasing reaction in a high-efficiency device such as a continuous fluidized bed, improving the efficiency of the viscosity-increasing reaction and ensuring the mechanical properties and molecular weight uniformity of the polymer, thereby further improving the stability of the product.

[0041] The application uses a treatment process completed in a short time, such as spray drying and fluidized bed solid-phase viscosity-increasing, which is more efficient in removing water and excluding volatile matter, avoids long exposure of the prepolymer to high temperature, effectively reduces the occurrence of oxidation reaction, and improves the color stability of the polymer. DETAILED DESCRIPTION

[0042] The application will be further described below in conjunction with examples. The examples are implemented on the premise of the technical solutions of the application and give detailed implementation modes and specific operation processes, but the protection scope of the application is not limited to the examples.

[0043] The test methods of the color, relative viscosity, melting point and mechanical properties of the product involved in the present application are described as follows:

[0044] Yellow index determination: determined according to GB / T 39822-2021 (Determination of the yellowing index of plastics and its change value).

[0045] Relative viscosity test conditions: the relative viscosity of the high-temperature-resistant nylon solution after dissolving with concentrated sulfuric acid with a concentration of 98% is tested at a temperature of 25 DEG C and a concentration of 0.01 g / ml according to the ISO 307 standard.

[0046] Melting point: using the DSC method, weighing 5-8 mg of the sample, under a nitrogen atmosphere, heating from room temperature to 400 DEG C at a rate of 20 DEG C / min, holding for 5 min, then cooling to room temperature at a rate of 20 DEG C / min, and then heating to 400 DEG C at a rate of 10 DEG C / min, the endothermic peak temperature at this time is the melting point of the polymer.

[0047] Mechanical property test: the prepared high-temperature-resistant nylon is injection molded into a test sample strip, the tensile strength is tested according to the GB / T1040.2 standard, the bending strength and bending modulus are tested according to the GB / T9341-2008 standard, and the simply supported beam impact strength is tested according to the GB / T1043.1 standard.

[0048] The experimental materials used in the present application are purchased from biochemical reagent companies, unless otherwise specified.

[0049] Example 1,

[0050] In this embodiment, the high-temperature-resistant nylon is prepared by the following steps:

[0051] (1) In the polymerization kettle, 60 parts of PA6T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water are added, the polymerization kettle is replaced with inert gas N2 to replace the air in the polymerization kettle, and the gas is pressurized to 0.8 MPa, heated and stirred, and the temperature is raised to 180 DEG C and reacted for 1.5 h, and the water is drained to keep the pressure stable; continue to heat to 225 DEG C, and the pressure is kept at 2.2 MPa, and react for 3 h; continue to heat to 275 DEG C, and react for 2 h, to obtain a PA6T / 66 prepolymer;

[0052] (2) The prepolymer under high pressure obtained in step (1) is sent to a pressure spray dryer, and slowly released to 0.8 MPa within 60 min, and after the pressure release is completed, the spray drying is started, and the drying temperature is 150 DEG C, and the gas medium is nitrogen, to obtain a powdery prepolymer;

[0053] (3) The powdery prepolymer obtained in step (2) is transported to a continuous fluidized bed, the gas of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 260 DEG C, and the residence time of the powdery prepolymer is 3 h, to obtain a high-temperature-resistant nylon powder.

[0054] (4) The high-temperature-resistant nylon powder obtained in step (3) is sent into a double screw extruder, the temperature of continuous melt extrusion of the double screw extruder is 330°C, the vacuum pressure is -0.08 MPa, the screw rotation speed is 280 rpm, and the residence time is 80 s, to obtain PA6T / 66 chips.

[0055] Example 2,

[0056] The high-temperature-resistant nylon is prepared by the following steps in this example:

[0057] (1) After 68 parts of PA6T salt, 38 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water are added into a polymerization kettle, the air in the polymerization kettle is replaced by inert gas N2, the polymerization kettle is pressurized to 0.8 MPa, heating and stirring are performed, the temperature is raised to 184°C, and reaction is performed for 1.5 h, water is drained to keep the pressure stable; the temperature is continuously raised to 230°C, the pressure is kept at 2.2 MPa, and reaction is performed for 3 h; the temperature is continuously raised to 260°C, and reaction is performed for 2 h, to obtain a PA6T / 66 prepolymer;

[0058] (2) The prepolymer under high pressure obtained in step (1) is sent into a pressure spray dryer, and slowly depressurized to 0.6 MPa within 45 min, after the depressurization is completed, spray drying is started, the drying temperature is 150°C, and the gas medium is nitrogen, to obtain a powdery prepolymer;

[0059] (3) The powdery prepolymer obtained in step (2) is transported to a continuous fluidized bed, the gas of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 260°C, and the residence time is 3 h, to obtain a high-temperature-resistant nylon powder;

[0060] (4) The high-temperature-resistant nylon powder obtained in step (3) is sent into a double screw extruder, the temperature of continuous melt extrusion of the double screw extruder is 330°C, the vacuum pressure is -0.08 MPa, the screw rotation speed is 280 rpm, and the residence time is 80 s, to obtain PA6T / 66 chips.

[0061] Example 3,

[0062] The high-temperature-resistant nylon is prepared by the following steps in this example:

[0063] (1) After 43 parts of PA6T salt, 40 parts of PA6I salt, 0.5 parts of sodium pyrophosphate and desalted water are added into a polymerization kettle, the air in the polymerization kettle is replaced by inert gas N2, the polymerization kettle is pressurized to 0.8 MPa, heating and stirring are performed, the temperature is raised to 182°C, and reaction is performed for 1.5 h, water is drained to keep the pressure stable; the temperature is continuously raised to 232°C, the pressure is kept at 2.8 MPa, and reaction is performed for 3 h; the temperature is continuously raised to 262°C, and reaction is performed for 2.2 h, to obtain a PA6T / 6I prepolymer;

[0064] (2) The prepolymer obtained in step (1) under high pressure is fed into a pressure spray dryer and the pressure is slowly released to 0.5 MPa within 80 min. After the pressure is released, spray drying is started at a temperature of 130°C and the gas medium is nitrogen. Powdered prepolymer is obtained.

[0065] (3) The powdered prepolymer obtained in step (2) is conveyed to a continuous fluidized bed. The gas in the continuous fluidized bed is hot nitrogen gas flow, the temperature is 272℃, and the residence time of the powdered prepolymer is 2.5h to obtain high temperature resistant nylon powder.

[0066] (4) The high-temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The continuous melt extrusion temperature of the twin-screw extruder is 325℃, the vacuum pressure is -0.08MPa, the screw speed is 300rpm, and the residence time is 70s to obtain PA6T / 6I chips.

[0067] Example 4

[0068] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0069] (1) In a polymerization reactor, 60 parts of PA6T salt, 20 parts of PA6I salt, 16 parts of PA66 salt, 0.5 parts of triphenyl hypophosphite and demineralized water were added. The air in the polymerization reactor was replaced with inert gas N2. The pressure was increased to 0.8 MPa, heated and stirred, and the temperature was raised to 180℃ for 1.5 h. The pressure was kept stable by draining water. The temperature was raised to 231℃ and the pressure was kept at 2.2 MPa for 3 h. The temperature was raised to 263℃ and the reaction was carried out for 1.5 h to obtain PA6T / 6I / 66 prepolymer.

[0070] (2) The prepolymer obtained in step (1) under high pressure is fed into a pressure spray dryer and slowly depressurized to 0.8MPa within 105min. After depressurization, spray drying is started at 180℃ and the gas medium is nitrogen to obtain powdered prepolymer.

[0071] (3) The powdered prepolymer obtained in step (2) is transported to a continuous fluidized bed. The gas in the continuous fluidized bed is hot nitrogen gas, the temperature is 255℃, and the residence time is 4h to obtain high temperature resistant nylon powder.

[0072] (4) The high-temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The continuous melt extrusion temperature of the twin-screw extruder is 340℃, the vacuum pressure is -0.08MPa, the screw speed is 245rpm, and the residence time is 90s to obtain PA6T / 6I / 66 chips.

[0073] Example 5

[0074] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0075] (1) In a polymerization reactor, add 60 parts of PA6F salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and demineralized water, then replace the air in the polymerization reactor with inert gas N2, pressurize to 0.8 MPa, heat and stir, raise the temperature to 180℃ and react for 1.5 h, drain water to keep the pressure stable; continue to raise the temperature to 231℃, keep the pressure at 2.6 MPa and react for 3 h; continue to raise the temperature to 263℃ and react for 2 h to obtain PA6F / 66 prepolymer;

[0076] (2) The prepolymer obtained in step (1) under high pressure is fed into a pressure spray dryer and slowly depressurized to 0.8MPa within 100min. After depressurization, spray drying is started at 120℃ and the gas medium is nitrogen to obtain powdered prepolymer.

[0077] (3) The powdered prepolymer obtained in step (2) is conveyed to a continuous fluidized bed. The gas in the continuous fluidized bed is hot nitrogen gas with a temperature of 280°C. The residence time of the powdered prepolymer is 2.2h to obtain high-temperature resistant nylon powder.

[0078] (4) The high-temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The continuous melt extrusion temperature of the twin-screw extruder is 335℃, the vacuum pressure is -0.09MPa, the screw speed is 320rpm, and the residence time is 45s to obtain PA6F / 66 chips.

[0079] Example 6

[0080] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0081] (1) In the polymerization reactor, 57 parts of PA6F salt, 39 parts of PA6I salt, 0.25 parts of phosphoric acid and demineralized water were added. The air in the polymerization reactor was replaced by inert gas N2. The pressure was increased to 0.8 MPa, heated and stirred, and the temperature was raised to 180℃ for 1.5 h. The pressure was kept stable by draining water. The temperature was raised to 231℃ and the pressure was kept at 1.9 MPa for 3 h. The temperature was raised to 273℃ and the reaction was carried out for 1.2 h to obtain PA6F / 6I prepolymer.

[0082] (2) The prepolymer obtained in step (1) under high pressure is fed into a pressure spray dryer and slowly depressurized to 0.8 MPa in 65 min. After depressurization, spray drying is started at 190°C and the gas medium is nitrogen to obtain powdered prepolymer.

[0083] (3) The powdered prepolymer obtained in step (2) is conveyed to a continuous fluidized bed. The gas in the continuous fluidized bed is hot nitrogen gas flow, the temperature is 256℃, and the residence time of the powdered prepolymer is 3h to obtain high temperature resistant nylon powder.

[0084] (4) The high-temperature-resistant nylon powder obtained in step (3) is sent into a double screw extruder, the temperature of continuous melt extrusion of the double screw extruder is 310°C, the vacuum pressure is -0.1 MPa, the screw rotation speed is 340 rpm, and the residence time is 65 s, to obtain PA6F / 6I chip.

[0085] Example 7,

[0086] The high-temperature-resistant nylon is prepared by the following steps in this example:

[0087] (1) After 59 parts of PA6I salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water are added into a polymerization kettle, the air in the polymerization kettle is replaced by inert gas N2, the polymerization kettle is pressurized to 0.8 MPa, heating and stirring are performed, the temperature is raised to 186°C, and reaction is performed for 1.5 h, water is drained to keep the pressure stable; the temperature is continuously raised to 231°C, the pressure is kept at 2.6 MPa, and reaction is performed for 3 h; the temperature is continuously raised to 262°C, and reaction is performed for 2 h, to obtain PA6I / 66 prepolymer;

[0088] (2) The prepolymer under high pressure obtained in step (1) is sent into a pressure spray dryer, and is slowly depressurized to 0.8 MPa within 55 min, after the depressurization is completed, spray drying is started, the drying temperature is 195°C, and the gaseous medium is nitrogen, to obtain powdery prepolymer;

[0089] (3) The powdery prepolymer obtained in step (2) is transported to a continuous fluidized bed, the gaseous medium of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 240°C, and the residence time is 3 h, to obtain high-temperature-resistant nylon powder;

[0090] (4) The high-temperature-resistant nylon powder obtained in step (3) is sent into a double screw extruder, the temperature of continuous melt extrusion of the double screw extruder is 310°C, the vacuum pressure is -0.1 MPa, the screw rotation speed is 340 rpm, and the residence time is 65 s, to obtain PA6I / 66 chip.

[0091] Example 8,

[0092] The high-temperature-resistant nylon is prepared by the following steps in this example:

[0093] (1) After 60 parts of PA6F salt, 19 parts of PA6I salt, 17 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water are added into a polymerization kettle, the air in the polymerization kettle is replaced by inert gas N2, the polymerization kettle is pressurized to 0.8 MPa, heating and stirring are performed, the temperature is raised to 182°C, and reaction is performed for 1.5 h, water is drained to keep the pressure stable; the temperature is continuously raised to 230°C, the pressure is kept at 2.4 MPa, and reaction is performed for 3 h; the temperature is continuously raised to 264°C, and reaction is performed for 2 h, to obtain PA6F / 6I / 66 prepolymer;

[0094] (2) The prepolymer in high pressure state obtained in step (1) is sent into a pressure spray dryer, and slowly depressurized to 0.8 MPa in 90 min, and after the depressurization is completed, spray drying is started, the drying temperature is 110°C, and the gaseous medium is nitrogen, to obtain a powdered prepolymer;

[0095] (3) The powdered prepolymer obtained in step (2) is transported into a continuous fluidized bed, the gaseous medium of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 235°C, and the residence time is 5 h, to obtain a high-temperature-resistant nylon powder;

[0096] (4) The high-temperature-resistant nylon powder obtained in step (3) is sent into a double-screw extruder, the temperature of continuous melt extrusion of the double-screw extruder is 330°C, the vacuum pressure is -0.08 MPa, the screw rotation speed is 280 rpm, and the residence time is 80 s, to obtain PA6F / 6I / 66 chips.

[0097] Example 9,

[0098] In this embodiment, a high-temperature-resistant nylon is prepared by the following steps:

[0099] (1) In a polymerization kettle, 60 parts of PA10T salt, 39 parts of PA66 salt, 0.5 parts of sodium hypophosphite, and desalted water are added, the polymerization kettle is replaced with inert gas N2 to replace the air in the polymerization kettle, and the air is replaced with N2 to pressurize the polymerization kettle to 0.8 MPa. After heating and stirring, the temperature is raised to 183°C and reacted for 1.5 h, the water is drained and the pressure is kept stable; continue to heat to 228°C, and keep the pressure at 2.8 MPa for 3 h; continue to heat to 258°C and react for 3 h, to obtain a PA6T / 66 prepolymer;

[0100] (2) The prepolymer in high pressure state obtained in step (1) is sent into a pressure spray dryer, and slowly depressurized to 0.8 MPa in 105 min, and after the depressurization is completed, spray drying is started, the drying temperature is 210°C, and the gaseous medium is nitrogen, to obtain a powdered prepolymer;

[0101] (3) The powdered prepolymer obtained in step (2) is transported into a continuous fluidized bed, the gaseous medium of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 270°C, and the residence time of the powdered prepolymer is 3 h, to obtain a high-temperature-resistant nylon powder;

[0102] (4) The high-temperature-resistant nylon powder obtained in step (3) is sent into a double-screw extruder, the temperature of continuous melt extrusion of the double-screw extruder is 330°C, the vacuum pressure is -0.08 MPa, the screw rotation speed is 300 rpm, and the residence time is 75 s, to obtain PA6T / 66 chips.

[0103] Example 10,

[0104] In this embodiment, a high-temperature-resistant nylon is prepared by the following steps:

[0105] (1) In the polymerization reactor, 57 parts of PA10I salt, 48 parts of PA66 salt, 0.5 parts of sodium hypophosphite and demineralized water were added. The air in the polymerization reactor was replaced by inert gas N2. The pressure was increased to 0.8 MPa, heated and stirred, and the temperature was raised to 187℃ for 1.5 h. The pressure was kept stable by draining water. The temperature was raised to 229℃ and the pressure was kept at 1.8 MPa for 3 h. The temperature was raised to 255℃ and the reaction was carried out for 2.5 h to obtain PA10I / 66 prepolymer.

[0106] (2) The prepolymer obtained in step (1) under high pressure is fed into a pressure spray dryer and slowly depressurized to 0.8MPa in 50min. After depressurization, spray drying is started at 140℃ and the gas medium is nitrogen to obtain powdered prepolymer.

[0107] (3) The powdered prepolymer obtained in step (2) is conveyed to a continuous fluidized bed. The gas in the continuous fluidized bed is hot nitrogen gas flow, the temperature is 260℃, and the residence time of the powdered prepolymer is 4.5h to obtain high temperature resistant nylon powder.

[0108] (4) The high-temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The continuous melt extrusion temperature of the twin-screw extruder is 340℃, the vacuum pressure is -0.08MPa, the screw speed is 350rpm, and the residence time is 90s to obtain PA10I / 66 chips.

[0109] Example 11

[0110] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0111] (1) In the polymerization reactor, 57 parts of PA12T salt, 47 parts of PA66 salt, 0.5 parts of sodium hypophosphite and demineralized water were added. The air in the polymerization reactor was replaced by inert gas N2. The pressure was increased to 0.8 MPa, heated and stirred, and the temperature was raised to 180℃ for 1.5 h. The pressure was kept stable by draining water. The temperature was raised to 226℃ and the pressure was kept at 2.2 MPa for 3 h. The temperature was raised to 275℃ and the reaction was carried out for 1.5 h to obtain PA12T / 66 prepolymer.

[0112] (2) The prepolymer obtained in step (1) under high pressure is fed into a pressure spray dryer and the pressure is slowly released to 0.8 MPa in 60 min. After the pressure is released, spray drying is started at 165°C and the gas medium is nitrogen to obtain powdered prepolymer.

[0113] (3) The powdered prepolymer obtained in step (2) is conveyed to a continuous fluidized bed. The gas in the continuous fluidized bed is hot nitrogen gas flow, the temperature is 255℃, and the residence time of the powdered prepolymer is 5.5h to obtain high temperature resistant nylon powder.

[0114] (4) The high-temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder. The continuous melt extrusion temperature of the twin-screw extruder is 315℃, the vacuum pressure is -0.08MPa, the screw speed is 315rpm, and the residence time is 80s to obtain PA12T / 66 chips.

[0115] Example 12

[0116] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0117] (1) In the polymerization reactor, add 60 parts of PA10T salt, 40 parts of PA10I salt, 0.5 parts of sodium hypophosphite and demineralized water, then replace the air in the polymerization reactor with inert gas N2, pressurize to 0.8 MPa, heat and stir, raise the temperature to 186℃ and react for 1.5 h, drain water to keep the pressure stable; continue to raise the temperature to 230℃, keep the pressure at 2.6 MPa and react for 3 h; continue to raise the temperature to 280℃ and react for 1 h to obtain PA10T / 10I prepolymer;

[0118] (2) The prepolymer obtained in step (1) under high pressure is fed into a pressure spray dryer and slowly depressurized to 0.8MPa in 70min. After depressurization, spray drying is started at 187℃ and the gas medium is nitrogen to obtain powdered prepolymer.

[0119] (3) The powdered prepolymer obtained in step (2) is conveyed to a continuous fluidized bed. The gas in the continuous fluidized bed is hot nitrogen gas flow, the temperature is 270℃, and the residence time of the powdered prepolymer is 2.5h to obtain high temperature resistant nylon powder.

[0120] (4) The high-temperature resistant nylon powder obtained in step (3) is fed into a twin-screw extruder, wherein the continuous melt extrusion temperature is 340℃, the vacuum pressure is -0.08MPa, the screw speed is 260rpm, and the residence time is 90s to obtain PA10T / 10I chips.

[0121] Example 13

[0122] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0123] (1) In a polymerization reactor, add 60 parts of PA9T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and demineralized water, then replace the air in the polymerization reactor with inert gas N2, pressurize to 0.8 MPa, heat and stir, raise the temperature to 184℃ and react for 1.5 h, drain water to maintain stable pressure; continue to raise the temperature to 229℃, maintain the pressure at 3 MPa, and react for 3 h; continue to raise the temperature to 259℃ and react for 2 h; obtain PA9T / 66 prepolymer;

[0124] (2) The prepolymer in high pressure state obtained in step (1) is sent into a pressure spray dryer, and slowly depressurized to 0.8 MPa in 120 min, and after the depressurization is completed, spray drying is started, the drying temperature is 180℃, and the gaseous medium is nitrogen, to obtain a powdery prepolymer;

[0125] (3) The powdery prepolymer obtained in step (2) is transported into a continuous fluidized bed, the gaseous medium of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 260℃, and the residence time of the powdery prepolymer is 4.5 h, to obtain a high-temperature-resistant nylon powder;

[0126] (4) The high-temperature-resistant nylon powder obtained in step (3) is sent into a double-screw extruder, the temperature of continuous melt extrusion of the double-screw extruder is 320℃, the vacuum pressure is -0.08 MPa, the screw rotation speed is 315 rpm, and the residence time is 55 s, to obtain PA9T / 66 chips.

[0127] Example 14,

[0128] The difference between this example and Example 1 is only that step (4) is not performed, and the high-temperature-resistant nylon powder is directly prepared according to steps (1) to (3).

[0129] Example 15,

[0130] The difference between this example and Example 1 is only that the “preparation method of the prepolymer” is different from step (1) of Example 1; specifically, in step (1) of this comparative example, after the raw materials are added into the polymerization kettle, the temperature is directly increased to 275℃, and the reaction is performed for 6.5 h.

[0131] Example 16,

[0132] This example prepares a high-temperature-resistant nylon by using the following steps:

[0133] (1) In a polymerization kettle, 60 parts of PA6T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite, and desalted water are added, the polymerization kettle is replaced with inert gas N2 to replace the air in the polymerization kettle, and the air is replaced with N2 to pressurize the polymerization kettle to 0.5 MPa, heated and stirred, the temperature is increased to 170℃, and the reaction is performed for 2 h, the water is drained to keep the pressure stable; the temperature is continuously increased to 200℃, the pressure is kept at 1.8 MPa, and the reaction is performed for 4 h; the temperature is continuously increased to 250℃, and the reaction is performed for 3 h, to obtain a PA6T / 66 prepolymer;

[0134] (2) The prepolymer in high pressure state obtained in step (1) is sent into a pressure spray dryer, and slowly depressurized to 0.8 MPa in 60 min, and after the depressurization is completed, spray drying is started, the drying temperature is 100℃, and the gaseous medium is nitrogen, to obtain a powdery prepolymer;

[0135] (3) The powdered prepolymer obtained in step (2) is transported into a continuous fluidized bed, the gas of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 230℃, the residence time of the powdered prepolymer is 5h, and high-temperature-resistant nylon powder is obtained;

[0136] (4) The high-temperature-resistant nylon powder obtained in step (3) is fed into a double-screw extruder, the temperature of continuous melt extrusion of the double-screw extruder is 300℃, the vacuum pressure is -0.09MPa, the screw rotation speed is 200rpm, the residence time is 90s, and PA6T / 66 chips are obtained.

[0137] Example 17,

[0138] The high-temperature-resistant nylon is prepared by the following steps in this example:

[0139] (1) In a polymerization kettle, 60 parts of PA6T salt, 40 parts of PA66 salt, 0.5 parts of sodium hypophosphite and desalted water are added, the polymerization kettle is replaced with inert gas N2 to replace the air in the polymerization kettle, the gas is pressurized to 1MPa, heated and stirred, the temperature is raised to 195℃, and reacted for 0.5h, then the water is drained and the pressure is kept stable; continue to heat to 240℃, keep the pressure at 3.0MPa, react for 1h; continue to heat to 280℃, react for 1h, and obtain PA6T / 66 prepolymer;

[0140] (2) The prepolymer under high pressure obtained in step (1) is fed into a pressure spray dryer, and slowly released to 0.8MPa within 60min, and after the pressure release is completed, the spray drying is started, the drying temperature is 220℃, and the gas medium is nitrogen, and a powdered prepolymer is obtained;

[0141] (3) The powdered prepolymer obtained in step (2) is transported into a continuous fluidized bed, the gas of the continuous fluidized bed is hot nitrogen gas flow, the temperature is 280℃, the residence time of the powdered prepolymer is 2h, and high-temperature-resistant nylon powder is obtained;

[0142] (4) The high-temperature-resistant nylon powder obtained in step (3) is fed into a double-screw extruder, the temperature of continuous melt extrusion of the double-screw extruder is 340℃, the vacuum pressure is -0.10MPa, the screw rotation speed is 350rpm, the residence time is 40s, and PA6T / 66 chips are obtained.

[0143] Comparative Example 1,

[0144] The difference between this comparative example and Example 1 is only that the "drying method" in step (2) of Example 1 is different; specifically, the prepolymer obtained in step (1) is subjected to air blowing drying at 80℃, after the surface moisture drying is completed, the prepolymer is crushed, the crushed prepolymer is further fed into a vacuum oven, dried at 110℃ 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.

[0145] Comparative Example 2,

[0146] The difference between the present comparative example and Example 1 is only in the way of solid phase polycondensation and viscosity increase, which is different from step (3) of Example 1. Specifically, the present comparative example uses a vacuum drum to carry out the solid phase polycondensation reaction, the reaction temperature is 260℃, and the residence time is 8h.

[0147] Comparative Example 3,

[0148] The difference between the present comparative example and Example 1 is only in the pressure release speed, which is released to 0.8MPa within 5min in the present comparative example.

[0149] The main role of the pressure release process is to reduce the moisture content in the system, and to balance the molecular weight growth rate of the polymer by controlling the pressure drop speed. In Example 1, the pressure release process is relatively slow (60min), which allows the viscosity of the prepolymer to 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 rapid increase of the viscosity due to the rapid removal of moisture, which affects the flowability and delivery performance. During the slow pressure release process of Example 1, the prepolymer still maintains a certain flowability, which enables it to be smoothly delivered to the spray dryer. Appropriate flowability is crucial for subsequent delivery, drying and solid phase viscosity increase processes. If the viscosity of the prepolymer is too high, pipeline blockage or material retention will occur during the delivery process, affecting continuous production.

[0150] In contrast, Comparative Example 3 uses a rapid pressure release to 0.8MPa within 5min, which will cause the moisture in the system to rapidly evaporate in a short time. Due to the rapid removal of moisture, the polycondensation reaction in the system is instantly pushed towards high molecular weight, resulting in rapid growth of the molecular chain and rapid increase of the viscosity; the rapid increase of the viscosity makes it difficult for the prepolymer to maintain good flowability, ultimately failing to perform normal delivery, and thus failing to complete the subsequent processes of spray drying, solid phase viscosity increase and double screw extrusion, etc.

[0151] The properties of the high-temperature resistant nylon obtained from Example 1 to Example 15, Comparative Example 1 and Comparative Example 2 were detected, and the results are shown in Table 1 below:

[0152] Table 1:

[0153]

[0154] Comparative Example 1 and Example 14, in Example 1, the material is continuously melt-extruded through a twin-screw extruder, which not only helps to mix the material uniformly and plasticize it sufficiently, but also promotes the amide exchange reaction in the melt through high temperature and high shear force. The occurrence of the amide exchange reaction allows the molecular weight to grow further during polymerization, and optimizes 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 not only ensures sufficient mixing, but also promotes the stability of the polymer system, so that the resulting material has further improved mechanical properties.

[0155] Although Example 14 did not undergo melt-extrusion treatment, its yellow index was 8.5, which showed relatively low color change and good color stability compared with Comparative Example 1 and Comparative Example 2. It can be seen that, although the melt-extrusion step is missing, the effective removal of moisture and volatile substances during spray drying and solid-phase tackification plays a key role in reducing oxidation reactions. During spray drying, the moisture in the material is effectively removed, and residual moisture can cause the polymer to hydrolyze during heating, further triggering oxidation reactions or color changes. By spray drying, the material is quickly dried, reducing the chemical reactions caused by moisture, thereby effectively controlling oxidation and maintaining good color stability. In addition, the conditions of the continuous fluidized bed solid-phase tackification are relatively mild and short in time, which can avoid excessive oxidation and make the product maintain a low yellow index.

[0156] In Example 1, due to the high temperature and vacuum environment of the twin-screw extruder, the volatile substances, bubbles and moisture in the material are effectively removed, the oxidation reaction and pigment formation are minimized, and the product maintains a low yellow index. In contrast, although Example 14 did not undergo melt-extrusion, the temperature and reaction conditions during solid-phase tackification may not be sufficient to completely avoid color changes, although the color change is not significant, there is still a certain gap compared with Example 1.

[0157] Comparative Example 1 and Comparative Example 1 differ only in the "drying method" from Example 1; Example 1 uses two efficient process treatment methods, spray drying and continuous fluidized bed solid-phase tackification, which not only removes moisture in a short period of time, but also effectively reduces the exposure time of the polymer under high temperature conditions, thereby effectively preventing the occurrence of oxidation reactions and maintaining a low yellow index.

[0158] In contrast, Comparative Example 1 employed a more traditional and time-consuming drying process. In Comparative Example 1, the pre-polymer was first treated at 80 °C under air drying, and after the surface moisture was evaporated, vacuum oven drying at 110 °C was performed, and finally small particle powder was obtained by crushing. Although this process also has some effect on moisture removal, the drying process is relatively slow, especially when air drying is performed at a lower temperature, which can result in incomplete removal of moisture during the long drying process. Even if the moisture content is further reduced by subsequent vacuum oven drying, due to the long drying exposure, oxidation reactions can still occur on the surface and inside of the polymer, especially when drying is performed at a higher temperature, the presence of oxygen leads to the formation of pigments and discoloration of the polymer, resulting in a significant increase in the yellow index.

[0159] In Example 1, due to the use of spray drying and fluidized bed solid phase tackification processes completed in a short time, the removal of moisture and the removal of volatile matter are more efficient, avoiding long exposure of the material at high temperature, thereby effectively reducing the occurrence of oxidation reactions. In contrast, the drying process in Comparative Example 1 is relatively slow and has a long exposure time, especially during the vacuum oven drying stage, the high temperature and long exposure time make it difficult to completely remove moisture and volatile matter, to some extent, accelerate the oxidation reaction, resulting in a significant increase in the yellow index.

[0160] Comparing Example 1 and Comparative Example 2, the only difference between Comparative Example 2 and Example 1 is the different "solid phase polycondensation tackification" method; Comparative Example 2 employs a vacuum drum process, the temperature of the solid phase polycondensation reaction is 260 °C, but the residence time is as long as 8 hours. The long reaction time will result in the polymer being exposed to high temperature for a long time, and the oxidation reaction will be intensified, and the oxidation reaction will cause the polymer to turn yellow.

[0161] In contrast, the continuous fluidized bed process employed in Example 1 has a shorter residence time (3 hours), so the material is exposed to high temperature for a shorter time, thereby reducing the occurrence of oxidation reactions and effectively maintaining a lower yellow index. Short reaction time and efficient gas-solid contact ensure rapid removal of moisture and volatile matter, avoiding color changes caused by oxidation.

[0162] The excessive reaction time of the vacuum drum process of Comparative Example 2 leads to uneven molecular weight distribution, as previously described, long time high temperature treatment can easily cause uneven expansion or degradation of molecular chains, resulting in a more loose molecular structure of the polymer, and the viscosity control becomes more difficult. While the continuous fluidized bed process of Example 1, although the time is shorter, but its more uniform gas-solid contact and milder reaction conditions can better control the molecular weight distribution and ensure the stability of the viscosity.

[0163] 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, with a small difference between the two, but the mechanical properties of Example 1 are more superior. Although the relative viscosity of Comparative Example 2 is slightly higher, indicating a slightly larger molecular weight, but a longer reaction time can lead to non-uniformity of viscosity, affecting the overall performance of the polymer.

[0164] Comparing Comparative Example 1 and Example 15, the stepwise heating method of Example 1 can better control the structure of the polymer, making the molecular chain grow uniformly, thereby improving the mechanical properties. In contrast, Example 15 uses direct heating to 275℃, resulting in non-uniform molecular structure and decreased mechanical properties, especially 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 decrease, indicating that the staged heating process is crucial for improving the mechanical properties and overall stability of the polymer, while direct heating to high temperature can accelerate the degradation of the polymer, causing damage to its mechanical properties.

[0165] The above description is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application, and any skilled person in the art can make some changes or modifications to the above-mentioned technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification of the above-mentioned technical content, which does not depart from the technical solution of the present application, shall still belong to the scope of the present application.

Claims

1. A continuous melt polymerization process for high temperature resistant nylon characterized by: The 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 to perform a prepolymerization reaction, and obtaining a prepolymer; During the prepolymerization reaction, the temperature is first increased to 170-195 DEG C and reacted for 0.5-2 h, water is drained to keep the pressure stable at 0.5-1.0 MPa, the temperature is continuously increased to 200-240 DEG C, the pressure is increased to 1.8-3.0 MPa, and reacted for 1-4 h, and then the temperature is continuously increased to 250-280 DEG C and reacted for 1-3 h; (2) the prepolymer under high pressure is introduced into a pressure spray dryer, first depressurized, and depressurized to 0.5-0.8 MPa in 45-120 min, and then spray dried, the drying temperature of the spray drying is 100-220 DEG C, and the gaseous medium is an inert gas, and a powdery prepolymer is obtained; (3) the powdery prepolymer is transported to a continuous fluidized bed to perform a solid-phase polycondensation and viscosity-increasing reaction, and a high-temperature-resistant nylon powder is obtained; (4) the high-temperature-resistant nylon powder is input into a double-screw extruder to continuously melt and extrude, and a high-temperature-resistant nylon is obtained; The temperature of the continuous melt extrusion is 300-340 DEG C, the vacuum pressure is -0.08 to -0.10 MPa, the screw rotation speed is 200-350 rpm, and the residence time is 40-90 s.

2. The continuous melt polymerization process for high temperature resistant nylon according to claim 1, characterized in that: The inert gas comprises nitrogen, helium and argon.

3. The continuous melt polymerization process for high temperature resistant nylon according to claim 1, characterized in that: The continuous fluidized bed is a hot inert gas flow, the temperature is 230-280 DEG C, and the residence time is 2-5 h.

4. A high temperature resistant nylon characterized by: The high-temperature-resistant nylon prepared by the polymerization method of any one of claims 1-3 has a yellow index of 7.2-8.5, a relative viscosity of 1.9-2.6, a tensile strength of 85-113 MPa, and a bending strength of 132-164 MPa.

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