Low-temperature continuous preparation device and method for high-temperature-resistant nylon

Abstract

The invention belongs to the technical field of high polymer material synthesis, and particularly relates to a low-temperature continuous preparation device and method for high-temperature-resistant nylon, and the method mainly comprises the following steps: a neutralization salt forming stage, a first-stage tubular reactor stage, a second-stage tubular reactor stage and a third-stage tubular reactor stage, therefore, continuous feeding of raw materials such as binary acid and diamine and continuous output of high-temperature-resistant nylon products are realized. The device and the method are suitable for preparing homopolymerized and copolymerized high-temperature-resistant nylon, such as semi-aromatic nylon, alicyclic nylon and nylon containing naphthalene rings, are wide in application range, low in polymerization temperature, short in polymerization time, stable in composition, good in product quality, low in yellow index, high in whiteness and stable in performance, realize backflow of diamine and recovery of materials, and are suitable for industrial production. Generation and emission of three wastes are reduced, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material synthesis, and in particular relates to a low-temperature continuous preparation device and method for high-temperature resistant nylon. Background Art

[0002] Polyamide, commonly known as nylon, has good comprehensive properties, including mechanical properties, heat resistance, wear resistance, chemical resistance and self-lubrication, and has a low friction coefficient. It is widely used in automotive parts, electronic appliances and engineering parts.

[0003] At present, the preparation methods of high temperature resistant nylon mainly include intermittent polymerization, direct solid phase polymerization and melt continuous method. CN 112358611 B, CN 115850692 B, CN 113999388 B, CN 105061755 B, CN104327265B, CN101768266 B and CN 117986569A etc. adopt intermittent polymerization to prepare high temperature resistant nylon. The intermittent polymerization is carried out in two steps, namely prepolymerization and solid phase postpolymerization. The specific steps are as follows: firstly prepare high temperature resistant nylon prepolymer at 210℃~240℃, and then solid phase viscosity increase at 230℃~260℃; the reaction temperature of this method is high, the preparation cycle is long, the energy consumption is high, the efficiency is low, there are many side reactions, the product is easy to turn yellow and produce gel, which affects the product performance. The patent CN 112979941 B of our research group adopts direct solid phase polymerization to prepare high temperature resistant nylon. The initial powdered nylon salt is continuously fed, and after the reactor is assembled, the material is continuously discharged to obtain a powdered nylon product. The reaction temperature of this method is low, the side reaction is small, the yellow index of the obtained product is low, and the product quality is good. However, the powdered nylon salt needs to be prepared first. For homopolymerized high temperature resistant nylon, the production efficiency is high and the reaction time is short. However, for copolymerized high temperature resistant nylon, this method has a long polymerization time, low production efficiency, and each component is easy to be unbalanced. CN 114316255 A, CN115873236A and CN 110684190 B adopt continuous melt extrusion to prepare high temperature resistant nylon. The reaction temperature is above the melting point. Although the preparation efficiency is high and the performance is stable, there are problems such as high reaction temperature, many side reactions, high yellow index, high energy consumption, and poor product quality. CN 117264197A introduces a continuous production method and device for semi-aromatic nylon, which utilizes the flash evaporation principle to directly spray into a drying tower for drying. However, under the spray pressure, the prepolymer has a low reaction degree and contains a certain amount of unreacted nylon salt. During the first-stage negative pressure polymerization, the nylon salt and the components with a low reaction degree are easily vaporized at this temperature, resulting in a difference in the composition of the final product and the feed ratio.

[0004] Whether it is intermittent polymerization, direct solid-phase polymerization or the current continuous polymerization method, they all have their shortcomings. Therefore, in order to efficiently prepare high-temperature resistant nylon products with stable performance, constant macromolecular chain composition and good quality, it is necessary to provide a low-temperature continuous preparation device and method for high-temperature resistant nylon. Summary of the invention

[0005] The purpose of the present invention is to provide a low-temperature continuous preparation device for high-temperature resistant nylon, and the second purpose of the present invention is to provide a preparation method thereof. The device and process method of the present invention have a short material residence time and high preparation efficiency. From the continuous input of dibasic acid and diamine to the continuous output of high-temperature resistant nylon products, the overall residence time is within 7 hours, and the reaction temperature of the entire reaction system is between 190°C and 250°C, which is more than 50°C lower than the melting point of the product. The low reaction temperature effectively avoids the occurrence of side reactions, the product has a low yellow index, and the product quality is good.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical solutions:

[0007] A low-temperature continuous preparation device for high-temperature resistant nylon comprises a salt-forming kettle 1, a heat exchanger 5, a salt solution concentration tank 7, a primary tubular reactor 9, a secondary tubular reactor 12, a tertiary tubular reactor 16 and a product collection tank 19 which are sequentially connected by pipelines; the primary tubular reactor 9 is a vertical tubular reactor; the secondary tubular reactor 12 and the tertiary tubular reactor 16 are both horizontal tubular reactors.

[0008] As a preferred embodiment of the present invention, at least two buffer tanks are arranged in parallel between the secondary tubular reactor 12 and the tertiary tubular reactor 16, and between the tertiary tubular reactor 16 and the product collecting tank 19; and a salt solution buffer tank 3 is arranged between the salt forming kettle 1 and the heat exchanger 5.

[0009] As a further preferred embodiment of the present invention, the exhaust port of the two-stage tubular reactor 12 is provided with a cyclone separator 13 , and the material outlet at the bottom of the cyclone separator 13 is connected to the two-stage tubular reactor 12 .

[0010] As a further preferred embodiment of the present invention, the low-temperature continuous preparation device of high-temperature resistant nylon also includes a distillation tower 10 connected to the top exhaust port of the first-level tubular reactor 9, the distillation tower 10 includes a top exhaust port, a bottom discharge port and a side feed port located in the middle of the tower body, the top exhaust port pipeline of the distillation tower 10 is connected to the salt kettle 1, and the bottom discharge port of the distillation tower 10 is connected to the feed port set at the bottom of the first-level tubular reactor 9.

[0011] As a further preferred embodiment of the present invention, a condensation tank 11 is arranged between the distillation tower 10 and the salt-forming kettle 1 , and between the salt solution concentration tank 7 and the salt-forming kettle 1 .

[0012] As a further preferred embodiment of the present invention, metering pumps are provided between the salt forming kettle 1 and the hydrochloric acid buffer tank 3, between the hydrochloric acid buffer tank 3 and the heat exchanger 5, between the heat exchanger 5 and the brine concentration tank 7, and between the brine concentration tank 7 and the primary tubular reactor 9.

[0013] The second invention object of the present invention is to use the device to carry out a method for low-temperature continuous preparation of high-temperature resistant nylon, which includes a neutralization and salt formation stage, a first-stage tubular reactor reaction stage, a second-stage tubular reactor polymerization stage, and a third-stage tubular reactor polymerization stage;

[0014] 1) Neutralization and salt-forming stage: In an inert gas atmosphere, diamine at 100 g / min to 500 g / min, dibasic acid at 100 g / min to 500 g / min, water at 100 g / min to 500 g / min and auxiliary agent at 0.5 g / min to 3 g / min are uniformly introduced into the salt-forming reactor 1, and the residence time is 0.3 h to 1 h at 40° C. to 90° C. to obtain a nylon salt solution with a concentration of 25% to 50%;

[0015] 2) Primary tubular reactor stage: The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 530 g / min to 1100 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 450 g / min to 1000 g / min. At this time, the temperature of the dilute salt solution at the outlet of the heat exchanger 5 is 140°C to 180°C. The high-temperature dilute salt solution after heat exchange is uniformly transported to the salt solution concentration tank 7 through the high-temperature dilute salt solution metering pump 6 at a rate of 390 g / min to 1000 g / min, and concentrated to 50% to 90% at 140°C to 180°C. The concentrated salt solution is uniformly transported to the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8 at a rate of 370 g / min to 750 g / min. 90℃~230℃, residence time 0.2h~1.5h, pressure 1.5MPa~2.4MPa, the material reacts continuously from bottom to top in the primary tubular reactor 9, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 370g / min~750g / min. The pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous particle / powder state. Due to the gasification and expansion of water in the system, the material becomes a porous particle structure / powder state; due to the weak alkalinity of the salt solution, the gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10, and the small amount of diamine in the gas is returned to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and reflux to the salt-forming kettle 1;

[0016] 3) Secondary tubular reactor polymerization stage: The porous granular / powdered material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed by a screw propeller at a rate of 370 g / min to 750 g / min to react; the reaction temperature is 220° C. to 250° C., the reaction pressure is 0.2 MPa to 1.0 MPa, and the residence time is 0.6 h to 1.5 h;

[0017] 4) Three-stage tubular reactor polymerization stage: The porous granular / powdered material in step 3) passes through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, enters the negative pressure stage of the three-stage tubular reactor 16, and is further solid-phase polymerized to obtain the final product; the temperature of the solid-phase polymerization is 220°C to 250°C, the absolute pressure is 5Pa to 500Pa, and the residence time is 0.5h to 3h.

[0018] As a preferred embodiment of the present invention, in step 2), the primary tubular reactor 9 is equipped with a distillation tower 10 and a condenser 11, the exhaust gas from the top of the primary tubular reactor 9 is separated by the distillation tower 10, a small amount of diamine in the gas phase is returned to the primary tubular reactor 9, the material composition in the primary tubular reactor 9 is kept constant, and other fractions are returned to the salt-forming kettle 1 for recycling through the condenser 11; in step 3), the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling.

[0019] As a further preferred embodiment of the present invention, in step 3), the secondary tubular reactor 12 is a positive pressure system, and three heating sections are set along the material flow direction, wherein the temperature of the first heating section is 200°C to 220°C, the temperature of the second heating section is set to 210°C to 230°C, and the temperature of the third heating section is set to 220°C to 250°C, and the residence time of the material in each heating section is 0.2h to 0.5h. The three-section heating belt can be set to adjust the polymerization temperature more flexibly to meet the requirements of different polymerization conditions; in step 4), the discharge of the three-stage tubular reactor (16) after solid phase polymerization is rapidly alternated through the third buffer tank (17) and the fourth buffer tank (18) to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally collected in the product collection tank (19).

[0020] It is understood that in step 1), the diamine is a mixture of one or more of an aliphatic diamine, an aromatic diamine, an alicyclic diamine and a naphthalene ring-containing diamine, including but not limited to butanediamine, pentanediamine, hexanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, m-xylylenediamine, p-xylylenediamine, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino -dicyclohexylmethane, 1,5-diaminonaphthalene, one or a mixture of two or more thereof; the dibasic acid is a mixture of one or more of an aliphatic dibasic acid, an aromatic dibasic acid, an alicyclic dibasic acid and a naphthalene ring-containing dibasic acid, including but not limited to a mixture of one or more of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid, terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, and 1,4-cyclohexane dicarboxylic acid.

[0021] It can be understood that in the neutralization and salt-forming stage in step 1), the inert gas is nitrogen, carbon dioxide, argon, etc., and the pH value of the nylon salt solution is 7.0-7.5.

[0022] It is understood that in the salt-forming stage of step 1), the auxiliary agent includes a catalyst and an antioxidant. The catalyst is one or more of phosphorous acid, sodium hypophosphite, triphenyl phosphate, and H10, and the amount of the catalyst is 0.1% to 0.6% of the dry mass of the dibasic acid and the diamine. The antioxidant is one or more of sodium hypophosphite, antioxidant 1010, antioxidant S9228, antioxidant SH120, and antioxidant B215, and the amount of the antioxidant is 0.1% to 0.6% of the dry mass of the dibasic acid and the diamine.

[0023] The primary reactor used in the present invention is a vertical tubular reactor, which can ensure that the reactants flow uniformly from bottom to top in the tubular reactor and carry out polymerization reaction, with high heat transfer efficiency, fast material heating rate, large reaction rate and short residence time; the process pressure in the secondary tubular reactor is positive pressure, and the temperature control adopts step temperature control to ensure the stability of each component, high yield, high reaction efficiency and low production cost. The process pressure of the secondary tubular reactor is significantly lower than that of the primary tubular reactor, and the water vaporizes in the secondary tubular reactor, and the moisture content of the material decreases, resulting in an increase in the melting point of the material in the secondary tubular reactor, and realizing the continuous transformation of the material from a homogeneous fluid state to a porous particle / powder state. Its porous or powder state is the discharge of condensation water in the secondary tubular reactor stage and the tertiary tubular reactor stage, which provides favorable conditions for improving the polymerization efficiency; between the secondary tubular reactor and the tertiary tubular reactor and between the tertiary reactor and the product collection tank, 2 groups of buffer tanks are respectively set for dual-path rapid switching, realizing the stability of the system process pressure and the continuous transportation of materials.

[0024] Specifically, the present invention realizes the continuous transformation of materials from a homogeneous fluid state to a porous particle / powder state through the interaction between the pressure sensor and the regulating valve of the first-stage tubular reactor and the pressure difference between the second-stage tubular reactors. Its porous structure provides favorable conditions for the polymerization of the second-stage tubular reactor stage and the third-stage tubular reactor stage.

[0025] The primary tubular reactor of the present invention is equipped with a distillation tower and a condensate tank. Due to the weak alkalinity of the salt solution, the gas discharged in this stage contains a small amount of diamine. After separation in the distillation tower, the small amount of diamine in the gas phase returns to the vertical primary reactor to keep the composition of the vertical primary reactor constant, and other fractions are returned to the salting kettle through the condensate tank, thereby reducing resource consumption and sewage treatment pressure.

[0026] The two-stage tubular reactor of the present invention is a positive pressure stage, which promotes the further polymerization of unreacted nylon salt and low molecular weight materials into products with higher molecular weight, can effectively prevent the gasification of nylon salt, keep the composition constant, and further improve the conversion rate of the reaction.

[0027] The two-stage tubular reactor of the present invention is provided with a cyclone separator at the exhaust port, and the powdered material at the bottom of the cyclone separator is returned to the two-stage tubular reactor to prevent the powdered prepolymer from being discharged along with the air flow to cause dust pollution.

[0028] The first buffer tank and the second buffer tank of the present invention can realize the continuous conversion from the positive pressure system to the negative pressure system, and the third buffer tank and the fourth buffer tank can realize the continuous conversion from the negative pressure system to the normal pressure system, thereby ensuring that the reaction system always maintains a continuous reaction state, and truly realizing the requirements of continuous production. Among them, the positive pressure system of the two-stage tubular reactor is continuously converted to the negative pressure system of the three-stage tubular reactor by quickly alternating the first buffer tank and the second buffer tank, thereby realizing the continuous transportation of materials, and the three-stage tubular reactor and the product collection tank realize the continuous output of materials by alternating the fast opening and fast closing of the third buffer tank and the fourth buffer tank, thereby maintaining the pressure stability of each system, thereby reducing the influence of pressure fluctuations on the polymerization process.

[0029] In the present invention, a first-stage tubular reactor is used, and the reactants flow evenly from bottom to top in the tubular reactor to carry out polymerization reaction, with high heat transfer efficiency, fast material heating rate, high reaction rate, short residence time and narrow residence time distribution;

[0030] In the present invention, the two-stage tubular reactor stage is a positive pressure stage, which ensures the stability of each composition, high efficiency and yield, low production cost, promotes the further polymerization of unreacted nylon salt into a product with a higher molecular weight, can effectively prevent the gasification of nylon salt, keep the composition constant, and further improve the conversion rate of the reaction;

[0031] In the present invention, the polymerization temperature of the system is carried out below the melting point of the product by 50°C, which can effectively reduce the occurrence of side reactions and improve product quality;

[0032] In the present invention, the entire polymerization pipeline and the container are protected by inert gas, and the material is also transported by inert gas to avoid oxidation of the material at high temperature and ensure product quality;

[0033] Step 4) The continuous conversion of the discharge of the three-stage tubular reactor from the negative pressure stage to the normal pressure system is achieved by the rapid alternation of the third buffer tank and the fourth buffer tank. The product collection tank and the third buffer tank and the fourth buffer tank are connected through a vacuum pipeline to achieve rapid switching between normal pressure and negative pressure, which can ensure both rapid discharge of materials and normal pressure system of the product collection tank.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The device and method of the present invention are suitable for the preparation of homopolymer and copolymer high temperature resistant nylon, such as semi-aromatic nylon, alicyclic nylon and naphthalene ring-containing nylon, etc., with wide application, low polymerization temperature, short polymerization time, stable composition, good product quality, low yellow index, high whiteness and stable performance;

[0036] 2. The device and method of the present invention can realize the continuous input of dibasic acid and diamine and the continuous output of high-temperature resistant nylon products. By quickly opening and closing the buffer tank alternately, the continuous transfer of the device is realized, and the pressure of each system is guaranteed to be stable, reducing the influence of pressure fluctuation on the polymerization process, and realizing continuous production;

[0037] 3. The reaction temperature of the whole system of the present invention is 190°C to 250°C, which is more than 50°C lower than the melting point of the product. The low reaction temperature effectively avoids the occurrence of side reactions and has high production efficiency. At the same time, a distillation tower and a cyclone separator are set to achieve the reflux of diamine and the recovery of materials, reduce the generation and emission of three wastes, and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the device of the present invention.

[0039] Figure 2-5 They are FT-IR, 1 HNMR, DSC and TG test results.

[0040] Figure 1Middle: salt forming kettle 1, dilute brine metering pump 2, brine buffer tank 3, dilute brine buffer metering pump 4, heat exchanger 5, high-temperature dilute brine metering pump 6, brine concentration tank 7, high-temperature concentrated brine metering pump 8, primary tubular reactor 9, distillation tower 10, condenser 11, secondary tubular reactor 12, cyclone separator 13, first buffer tank 14, second buffer tank 15, tertiary tubular reactor 16, third buffer tank 17, fourth buffer tank 18, product collection tank 19. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below through specific embodiments.

[0042] A low temperature continuous preparation device for high temperature resistant nylon according to an embodiment of the present invention, such as Figure 1 As shown: it includes a salt forming kettle 1, a heat exchanger 5, a salt solution concentration tank 7, a primary tubular reactor 9, a secondary tubular reactor 12, a tertiary tubular reactor 16 and a product collecting tank 19 connected in sequence by pipelines; the primary tubular reactor 9 is a vertical tubular reactor; the secondary tubular reactor 12 and the tertiary tubular reactor 16 are both horizontal tubular reactors. At least two buffer tanks are arranged in parallel between the secondary tubular reactor 12 and the tertiary tubular reactor 16, and between the tertiary tubular reactor 16 and the product collecting tank 19; a salt solution buffer tank 3 is arranged between the salt forming kettle 1 and the heat exchanger 5. A cyclone separator 13 is arranged at the exhaust port of the secondary tubular reactor 12, and the material outlet at the bottom of the cyclone separator 13 is connected to the secondary tubular reactor 12. The low-temperature continuous preparation device of high-temperature resistant nylon also includes a distillation tower 10 connected to the top exhaust port of the first-stage tubular reactor 9. The distillation tower 10 includes a top exhaust port, a bottom discharge port and a side feed port located in the middle of the tower body. The top exhaust port pipeline of the distillation tower 10 is connected to the salt kettle 1, and the bottom discharge port of the distillation tower 10 is connected to the feed port set at the bottom of the first-stage tubular reactor 9. A condensation tank 11 is set between the distillation tower 10 and the salt kettle 1, and between the salt solution concentration tank 7 and the salt kettle 1. Metering pumps are set between the salt kettle 1 and the hydrochloric acid buffer tank 3, between the hydrochloric acid buffer tank 3 and the heat exchanger 5, between the heat exchanger 5 and the salt solution concentration tank 7, and between the salt solution concentration tank 7 and the first-stage tubular reactor 9. The metering pump is as follows Figure 1 As shown in the figure, there are respectively a dilute salt liquid metering pump 2, a buffer liquid metering pump 4, a high-temperature dilute salt liquid metering pump 6 and a high-temperature concentrated salt liquid metering pump 8, the purpose of which is to control the material flow rate, and then control the retention time of the material in the device. In the connecting pipeline of the device, a number of control valves are also arranged, and the salt forming kettle, the salt liquid buffer tank and the salt liquid concentration tank are all provided with stirring devices. The above-mentioned control valves, stirring devices, etc. are all conventional settings in this field, and the device will not be described in detail.

[0043] In other embodiments, three heating sections can be set along the material flow direction of the secondary tubular reactor (12), wherein the temperature of the first heating section is 200°C to 220°C, the temperature of the second heating section is set to 210°C to 230°C, and the temperature of the third heating section is set to 220°C to 250°C, and the residence time of the material in each heating section is 0.2h to 0.5h; the three-section heating belt can be set to adjust the polymerization temperature more flexibly, meet the requirements of different polymerization conditions, and ensure that the temperature control of the system is more accurate. It is particularly suitable for the preparation of copolymers. For the preparation of homopolymers, three-section heating is not required, and direct heating can achieve the effect of the present invention.

[0044] The working process of low-temperature continuous preparation of high-temperature resistant nylon using the above device is as follows:

[0045] 1) Neutralization and salt-forming stage: In an inert gas atmosphere, diamine at 100 g / min to 500 g / min, dibasic acid at 100 g / min to 500 g / min, water at 100 g / min to 500 g / min and auxiliary agent at 0.5 g / min to 3 g / min are uniformly introduced into the salt-forming reactor 1, and the residence time is 0.3 h to 1 h at 40° C. to 90° C. to obtain a nylon salt solution with a concentration of 25% to 50%;

[0046] 2) Primary tubular reactor stage: The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 530 g / min to 1100 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 450 g / min to 1000 g / min. At this time, the temperature of the dilute salt solution at the outlet of the heat exchanger 5 is 140°C to 180°C. The high-temperature dilute salt solution after heat exchange is uniformly transported to the salt solution concentration tank 7 through the high-temperature dilute salt solution metering pump 6 at a rate of 390 g / min to 1000 g / min, and concentrated to 50% to 90% at 140°C to 180°C. The concentrated salt solution is uniformly transported to the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8 at a rate of 370 g / min to 750 g / min. 90℃~230℃, residence time 0.2h~1.5h, pressure 1.5MPa~2.4MPa, the material reacts continuously from bottom to top in the primary tubular reactor 9, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 370g / min~750g / min. The pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous particle / powder state. Due to the gasification and expansion of water in the system, the material becomes a porous particle structure / powder state; due to the weak alkalinity of the salt solution, the gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10, and the small amount of diamine in the gas is returned to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and reflux to the salt-forming kettle 1;

[0047] 3) Two-stage tubular reactor polymerization stage: The porous granular / powdered material in step 2) enters the positive pressure stage of the two-stage tubular reactor 12, and the material is pushed forward at a rate of 370 g / min to 750 g / min by a screw propeller arranged in the two-stage tubular reactor 12 to react; the two-stage tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the gas-solid mixture discharged from the exhaust port is separated by the cyclone separator 13, and the powdered material is collected at the bottom and returned to the two-stage tubular reactor 12 for recycling; the two-stage tubular reactor 12 is a positive pressure system. In each embodiment of the present invention, the two-stage tubular reactor 12 is a positive pressure system. The reaction temperature of the reactor 12 is 220°C to 250°C, the reaction pressure is 0.2MPa to 1.0MPa, and the residence time is 0.6h to 1.5h; in other embodiments, the two-stage tubular reactor can also be provided with three heating sections along the material flow direction, wherein the temperature of the first heating section is 200°C to 220°C, the temperature of the second heating section is set to 210°C to 230°C, and the temperature of the third heating section is set to 220°C to 250°C, and the residence time of the material in each heating section is 0.2h to 0.5h; the three-section heating belt can be provided to adjust the polymerization temperature more flexibly to meet the requirements of different polymerization conditions;

[0048] 4) Three-stage tubular reactor polymerization stage: Step 3) The porous granular / powdered material passes through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, enters the negative pressure stage of the three-stage tubular reactor 16, and is further solid-phase polymerized to obtain the final product; the temperature of the solid-phase polymerization is 220°C to 250°C, the absolute pressure is 5Pa to 500Pa, and the residence time is 0.5h to 3h; the discharge after the solid-phase polymerization of the three-stage tubular reactor 16 passes through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and is finally collected in the product collection tank 19.

[0049] It can be understood that in step 1), the diamine is a mixture of one or more of an aliphatic diamine, an aromatic diamine, an alicyclic diamine and a naphthalene ring-containing diamine, and the diamine is preferably butanediamine, pentanediamine, hexanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, m-xylylenediamine, p-xylylenediamine, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, 1,5- The invention discloses a method for preparing a nylon salt solution comprising: preparing a nylon salt solution comprising: a mixture of one or more of diaminonaphthalene; the dibasic acid is a mixture of one or more of aliphatic dibasic acid, aromatic dibasic acid, alicyclic dibasic acid and naphthalene ring-containing dibasic acid, and the dibasic acid is preferably a mixture of one or more of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid, terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid and 1,4-cyclohexane dicarboxylic acid; and the pH value of the nylon salt solution is 7.0 to 7.5.

[0050] It is understood that in the salt-forming stage of step 1), the auxiliary agent includes a catalyst and an antioxidant. The catalyst is one or more of phosphorous acid, sodium hypophosphite, triphenyl phosphate, and H10, and the amount of the catalyst is 0.1% to 0.6% of the dry mass of the dibasic acid and the diamine. The antioxidant is one or more of sodium hypophosphite, antioxidant 1010, antioxidant S9228, antioxidant SH120, and antioxidant B215, and the amount of the antioxidant is 0.1% to 0.6% of the dry mass of the dibasic acid and the diamine.

[0051] Example 1

[0052] This embodiment utilizes Figure 1 The method for continuously producing semi-aromatic copolymer high temperature resistant nylon PA5T / 56 at low temperature by the device shown in the figure comprises the following steps:

[0053] 1) In a nitrogen atmosphere, pentamethylenediamine, terephthalic acid, adipic acid (the molar ratio of terephthalic acid to adipic acid is 60:40), water and sodium hypophosphite are transported to a 40° C. salt-forming reactor 1 at a rate of 206 g / min, 199.2 g / min, 116.8 g / min, 261 g / min and 0.5 g / min, respectively, with a residence time of 0.5 h. The nylon salt solution at the outlet of the salt-forming reactor is 50%; the pH value of the nylon salt solution is 7.0-7.5; in this embodiment, the inert gas is nitrogen, and in other embodiments, carbon dioxide gas and argon gas may also be selected;

[0054] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 783.5 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 680 g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C. The nylon salt solution passes through the heat exchanger 5 and the high-temperature dilute salt solution metering pump 6 at a rate of 680 g / min and uniformly and continuously enters the 180°C salt solution concentration tank 7. The nylon salt solution at the outlet of the salt solution concentration tank 7 is 90%; the nylon salt concentrate is then heated to 499 The high-temperature concentrated salt solution metering pump 8 enters the primary tubular reactor 9 at a rate of g / min. The temperature in the primary tubular reactor 9 is 210°C, the pressure is 1.7MPa, and the residence time is 1.0h. The material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 475g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0055] 3) The porous particles / powdered material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed forward by a screw propeller provided in the secondary tubular reactor 12 at a rate of 475 g / min while reacting. The secondary tubular reactor 12 adopts three-stage heating, the temperature of the first heating section is set to 210° C., the temperature of the second heating section is set to 230° C., the temperature of the third heating section is set to 240° C., the pressure is 0.5 MPa, the residence time of the first section is 0.2, the residence time of the second section is 0.3 h, and the residence time of the third section is 0.5 h; the pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous particles / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0056] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 240° C., the absolute pressure is 8 Pa, and the residence time is 2 h. The discharge after solid-phase polymerization in the tertiary tubular reactor 16 is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally the continuous discharge is realized to obtain the granular / powdered PA5T / 56 final product collected in the product collection tank.

[0057] Example 2

[0058] This embodiment uses Figure 1 The method for continuously preparing aliphatic high temperature resistant nylon PA46 at low temperature by the device shown in the figure comprises the following steps:

[0059] 1) In a nitrogen atmosphere, diaminobutane, adipic acid, water and sodium hypophosphite were transported to a 50°C salt-forming kettle at a rate of 176 g / min, 292 g / min, 117 g / min and 2.8 g / min, respectively. The residence time was 0.3 h, and the nylon salt solution at the outlet of the salt-forming kettle was 25%;

[0060] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 587.8 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 485 g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 140°C. The nylon salt solution passes through the heat exchanger 5 and continuously enters the 170°C salt solution concentration tank 7 through the high-temperature dilute salt solution metering pump 6 at a rate of 485 g / min. The nylon salt solution at the outlet of the salt solution concentration tank 7 is 50%; the nylon salt concentrate is then heated to 446.2 g / m in rate through the high-temperature concentrated salt solution metering pump 8 into the primary tubular reactor 9, the temperature in the primary tubular reactor 9 is 190°C, the pressure is 1.5MPa, and the residence time is 0.2h; the material reacts continuously from bottom to top in the primary tubular reactor 9, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 420g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10, and the small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0061] 3) The porous granular / powdered material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed forward by a screw propeller provided in the secondary tubular reactor 12 at a rate of 420 g / min while reacting. The temperature in the secondary tubular reactor 12 is 220° C., the pressure is 0.2 MPa, and the residence time is 0.6 h. The pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous granular / powder state. The secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling.

[0062] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 220° C., the absolute pressure is 5 Pa, and the residence time is 0.5 h. The discharge after solid-phase polymerization in the tertiary tubular reactor 16 is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered PA46 final product.

[0063] Example 3

[0064] This embodiment uses Figure 1 The method for preparing alicyclic copolymer high temperature resistant nylon PA6C / 66 at low temperature and continuously by the device shown in the figure comprises the following steps:

[0065] 1) In a nitrogen atmosphere, hexamethylenediamine, adipic acid, cyclohexanediacid (cyclohexanediacid and adipic acid molar ratio 60 / 40), water and sodium hypophosphite are transported to a 60° C. salt-forming reactor 1 at a rate of 232.32 g / min, 116.8 g / min, 105.6 g / min, 181.76 g / min and 1 g / min, respectively, with a residence time of 0.6 h. The nylon salt solution at the outlet of the salt-forming reactor 1 is 40%;

[0066] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 637.48 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 530 g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 160°C; the nylon salt solution passes through the heat exchanger 5 and continuously enters the 160°C salt solution concentration tank 7 through the high-temperature dilute salt solution metering pump 6 at a rate of 530 g / min, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrate is then heated to 39 7g / min rate through the high temperature concentrated salt solution metering pump 8 into the primary tubular reactor 9, the temperature in the reactor is 220°C, the pressure is 2.1MPa, and the residence time is 0.8h; the material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 375g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0067] 3) The porous particles / powdered material in step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed forward by a screw propeller provided in the secondary tubular reactor 12 at a rate of 375 g / min while reacting. The reactor 12 adopts three-stage heating, the temperature of the first heating section is set to 200° C., the temperature of the second heating section is set to 210° C., the temperature of the third heating section is set to 230° C., the pressure is 0.5 MPa, the residence time of the first section is 0.2, the residence time of the second section is 0.3 h, and the residence time of the third section is 0.2 h; the pressure difference between the first tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous particles / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0068] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 230° C., the absolute pressure is 30 Pa, and the residence time is 1 h. The discharge after the solid-phase polymerization of the tertiary tubular reactor 16 is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered PA6C / 66 final product.

[0069] Example 4

[0070] This embodiment uses Figure 1 The method for continuously preparing semi-aromatic high temperature resistant nylon PA10T at low temperature by the device shown in the figure comprises the following steps:

[0071] 1) In a nitrogen atmosphere, decanediamine, terephthalic acid, water and sodium hypophosphite are transported to a 90°C salt-forming reactor 1 at a rate of 344 g / min, 332 g / min, 270.4 g / min and 1.5 g / min, respectively. The residence time is 1 hour. The nylon salt solution at the outlet of the salt-forming reactor 1 is 40%;

[0072] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 947.9 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 840 g / min, at which time the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180° C.; the nylon salt solution passes through the heat exchanger 5 and continuously enters the 180° C. salt solution concentration tank 7 through the high-temperature dilute salt solution metering pump 6 at a rate of 840 g / min, and the nylon salt solution at the outlet of the concentration tank 7 is 75%; the nylon salt concentrate is then heated to 63 0g / min rate through the high temperature concentrated salt solution metering pump 8 into the primary tubular reactor 9, the temperature in the reactor is 230℃, the pressure is 2.4MPa, and the residence time is 1.5h; the material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 600g / min. The gas discharged in this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0073] 3) The porous granular / powdered material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed forward by a screw propeller provided in the secondary tubular reactor 12 at a rate of 600 g / min while reacting, the temperature in the reactor is 250° C., the pressure is 0.2 MPa, and the residence time is 1.5 h; the pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous granular / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0074] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 250° C., the absolute pressure is 50 Pa, and the residence time is 3.0 h. The discharge after solid-phase polymerization in the tertiary tubular reactor 16 is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered PA10T final product.

[0075] Example 5

[0076] This embodiment uses Figure 1 The method for continuously preparing semi-aromatic copolymer high temperature resistant nylon PA6T / 66 at low temperature by the device shown in the figure comprises the following steps:

[0077] 1) In a nitrogen atmosphere, hexamethylenediamine, terephthalic acid, adipic acid (the molar ratio of terephthalic acid to adipic acid is 60:40), water and sodium hypophosphite are transported to a 60°C salt-forming kettle at a rate of 234.32 g / min, 199.2 g / min, 116.8 g / min, 220.13 g / min and 1 g / min, respectively. The residence time is 1 hour, and the nylon salt solution at the outlet of the salt-forming kettle is 40%;

[0078] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 771.45 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 665 g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution passes through the heat exchanger and continuously enters the 180°C salt solution concentration tank at a rate of 665 g / min through the high-temperature dilute salt solution metering pump 6, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrate is then heated to 498.7 5g / min rate through the high temperature concentrated salt solution metering pump 8 into the primary tubular reactor 9, the temperature in the reactor is 220℃, the pressure is 2.1MPa, and the residence time is 1.0h; the material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 473g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0079] 3) The porous granular / powdered material in step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed forward by a screw propeller arranged in the secondary tubular reactor 12 at a rate of 473 g / min while reacting. The reactor 12 adopts three-stage heating, the temperature of the first heating section is 220° C., the temperature of the second heating section is set to 230° C., the temperature of the third heating section is set to 240° C., the pressure is 1.0 MPa, the residence time of the first section is 0.2, the residence time of the second section is 0.3h, and the residence time of the third section is 0.4h; the pressure difference between the first tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous granular / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0080] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 240° C., the absolute pressure is 100 Pa, and the residence time is 3.0 h. The discharge after solid-phase polymerization in the tertiary tubular reactor 16 is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered PA6T / 66 final product.

[0081] Example 6

[0082] This embodiment uses Figure 1The device shown is a method for continuously preparing semi-aromatic copolymer high-temperature resistant nylon PA6T / 66 at low temperature, which is the same as Example 5. The difference from Example 5 is that the amount of each raw material is different. The flow rate of each raw material in this embodiment is: hexamethylenediamine, terephthalic acid, adipic acid (the molar ratio of terephthalic acid to adipic acid is 50:50), water and additives are continuously added to the salt-forming kettle at a rate of 234.32 g / min, 166 g / min, 146 g / min, 218.53 g / min and 1 g / min, respectively.

[0083] Example 7

[0084] This embodiment uses Figure 1 The method for preparing semi-aromatic copolymer high-temperature resistant nylon PA6T / 66 at low temperature continuously by the device shown is the same as Example 5. The difference from Example 5 is that the flow rate of each raw material in this embodiment is as follows: hexamethylenediamine, terephthalic acid, adipic acid (the molar ratio of terephthalic acid to adipic acid is 55:45), water and additives are continuously added to the salt-forming kettle at a rate of 234.32 g / min, 182.6 g / min, 131.4 g / min, 219.33 g / min and 1 g / min, respectively.

[0085] Example 8

[0086] This embodiment uses Figure 1 The method for preparing semi-aromatic copolymer high-temperature resistant nylon PA6T / 66 at low temperature continuously by the device shown is the same as Example 5. The difference from Example 5 is that the flow rate of each raw material in this embodiment is as follows: hexamethylenediamine, terephthalic acid, adipic acid (the molar ratio of terephthalic acid to adipic acid is 65:35), water and additives are continuously added to the salt-forming kettle at a rate of 234.32 g / min, 215.8 g / min, 102.2 g / min, 220.93 g / min and 1 g / min, respectively.

[0087] Example 9

[0088] This embodiment uses Figure 1 The method for continuously preparing high temperature resistant nylon PA10N containing naphthalene rings at low temperature by the device shown in the figure comprises the following steps:

[0089] 1) In a nitrogen atmosphere, decanediamine, 2,6-dinaphthoic acid, water and phosphorous acid are transported to a salt-forming kettle at 80°C at a rate of 344 g / min, 432 g / min, 310.4 g / min and 1.2 g / min, respectively. The residence time is 1 h. The nylon salt solution at the outlet of the salt-forming kettle is 40%;

[0090] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 1087.6 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 986 g / min, at which time the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180° C.; the nylon salt solution passes through the heat exchanger and continuously enters the 180° C. salt solution concentration tank through the high-temperature dilute salt solution metering pump 6 at a rate of 986 g / min, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrate is then heated to 739 The material enters the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8 at a rate of 230°C, the pressure 2.4MPa, and the residence time 1.0h at a rate of 712g / min. The material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 712g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1.

[0091] 3) The porous granular / powdered material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed forward by a screw propeller provided in the secondary tubular reactor 12 at a rate of 712 g / min while reacting, the temperature in the reactor is 250° C., the pressure is 0.8 MPa, and the residence time is 1.2 h; the pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous granular / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0092] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 250° C., the absolute pressure is 5 Pa, and the residence time is 3.0 h. The discharge after solid-phase polymerization in the tertiary tubular reactor 16 is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered PA10N final product.

[0093] Example 10

[0094] This embodiment uses Figure 1 The method for continuously preparing semi-aromatic copolymer high temperature resistant nylon PA6T / 10T at low temperature by the device shown in the figure comprises the following steps:

[0095] 1) In a nitrogen atmosphere, hexamethylenediamine, decanediamine (the molar ratio of hexamethylenediamine to decanediamine is 65:35), terephthalic acid, water and sodium hypophosphite are transported to a salt-forming kettle at 80° C. at a rate of 150.8 g / min, 120.4 g / min, 332 g / min, 241.28 g / min and 0.7 g / min, respectively. The residence time is 1 hour. The nylon salt solution at the outlet of the salt-forming kettle is 40%;

[0096] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 845.18 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 744 g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution passes through the heat exchanger and continuously enters the 180°C salt solution concentration tank at a rate of 744 g / min through the high-temperature dilute salt solution metering pump 6, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrate is then heated to 558 The material enters the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8 at a rate of g / min. The temperature in the reactor is 220°C, the pressure is 2.1MPa, and the residence time is 1.0h. The material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 533g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1.

[0097] 3) The porous particles / powdered material in step 2) enters the positive pressure stage of the secondary tubular reactor 12, and the material is pushed forward at a rate of 533 g / min by a screw propeller arranged in the secondary tubular reactor 12 to react. The temperature of the first heating section in the reactor is 220° C., the temperature of the second heating section is set to 230° C., the temperature of the third heating section is set to 250° C., the pressure is 0.7 MPa, and the residence time of the material in each heating section is 0.4 h; the pressure difference between the first tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous particles / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0098] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 250° C., the absolute pressure is 500 Pa, and the residence time is 2 h. The discharge of the tertiary tubular reactor 16 after solid-phase polymerization is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realize continuous discharge to obtain the granular / powdered PA6T / 10T final product.

[0099] Embodiment 11

[0100] This embodiment uses Figure 1 The method for preparing semi-aromatic copolymer high temperature resistant nylon MXD6 at low temperature and continuously by the device shown in the figure comprises the following steps:

[0101] 1) In a nitrogen atmosphere, adipic acid, m-phenylenediamine, water and sodium hypophosphite are transported to a salt-forming kettle at 90°C at a rate of 292 g / min, 216 g / min, 203.2 g / min and 1.2 g / min, respectively. The residence time is 1 hour. The nylon salt solution at the outlet of the salt-forming kettle is 40%;

[0102] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 712.4 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 612 g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 170°C; the nylon salt solution passes through the heat exchanger and continuously enters the 170°C salt solution concentration tank at a rate of 612 g / min through the high-temperature dilute salt solution metering pump 6, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrate is then 459 g / min rate through the high-temperature concentrated salt solution metering pump 8 into the primary tubular reactor 9, the temperature in the reactor is 210°C, the pressure is 1.7MPa, and the residence time is 1.0h; the material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 433g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0103] 3) The porous granular / powdered material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is pushed forward by a screw propeller provided in the secondary tubular reactor 12 at a rate of 433 g / min while reacting, the temperature in the reactor is 240° C., the pressure is 0.4 MPa, and the residence time is 1.0 h; the pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous granular / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0104] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 240° C., the absolute pressure is 200 Pa, and the residence time is 3 hours. The discharge of the tertiary tubular reactor 16 after solid-phase polymerization is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered MXD6 final product.

[0105] Example 12

[0106] This embodiment uses Figure 1 The low-temperature continuous preparation method of semi-aromatic copolymer high-temperature resistant nylon PA6T / 6I / 6 is prepared by the device at low temperature, and the steps are as follows:

[0107] 1) In a nitrogen atmosphere, hexamethylenediamine, terephthalic acid, isophthalic acid, caprolactam, water and sodium hypophosphite are continuously transported to a salt-forming kettle at 80°C through a silo or pipeline at a rate of 234.32 g / min, 166 g / min, 166 g / min, 113 g / min, 339.66 g / min and 3 g / min, respectively. The residence time is 1 hour, and the nylon salt solution at the outlet of the salt-forming kettle is 50%;

[0108] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 1021.98 g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 910 g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution passes through the heat exchanger and continuously enters the 180°C salt solution concentration tank at a rate of 910 g / min through the high-temperature dilute salt solution metering pump 6, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrate is then heated to 682. 5g / min rate through the high temperature concentrated salt solution metering pump 8 into the primary tubular reactor 9, the temperature in the reactor is 230°C, the pressure is 2.4MPa, and the residence time is 1.5h; the material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 650g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0109] 3) The porous particles / powdered material in step 2) enters the positive pressure stage of the secondary tubular reactor 12, and the material is pushed forward at a rate of 650 g / min by a screw propeller arranged in the secondary tubular reactor 12 to react. The temperature of the first heating section in the reactor is 220° C., the temperature of the second heating section is set to 230° C., the temperature of the third heating section is set to 250° C., the pressure is 1.0 MPa, and the residence time of the material in each heating section is 0.5 h; the pressure difference between the first tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the material from the homogeneous fluid state to the porous particles / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling;

[0110] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 250° C., the absolute pressure is 300 Pa, and the residence time is 2 h. The discharge of the tertiary tubular reactor 16 after solid-phase polymerization is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered PA6T / 6I / 6 final product.

[0111] Embodiment 13

[0112] This embodiment uses Figure 1 The method for continuously preparing semi-aromatic copolymer high temperature resistant nylon PA6T / 6I / 66 at low temperature by the device shown in the figure comprises the following steps:

[0113] 1) In a nitrogen atmosphere, hexamethylenediamine, terephthalic acid, isophthalic acid, adipic acid, water and antioxidant 1010 are continuously transported to a salting kettle at 80° C. through a silo or pipeline at a rate of 234.32 g / min, 116.2 g / min, 116.2 g / min, 116.8 g / min, 233.41 g / min and 1.12 g / min, respectively. The residence time is 1 hour. The nylon salt solution at the outlet of the salting kettle is 40%;

[0114] 2) The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate of 818.05g / min, and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a rate of 710g / min. At this time, the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution passes through the heat exchanger and continuously enters the 180°C salt solution concentration tank at a rate of 710g / min through the high-temperature dilute salt solution metering pump 6, and the nylon salt solution at the outlet of the concentration tank is 70%; the nylon salt concentrate is then heated to 532. 5g / min rate through the high temperature concentrated salt solution metering pump 8 into the primary tubular reactor 9, the temperature in the reactor is 230°C, the pressure is 2.4MPa, and the residence time is 1.0h; the material reacts continuously from bottom to top in the tubular reactor, and is uniformly and continuously transported to the secondary tubular reactor 12 at a rate of 508g / min. The gas discharged at this stage contains a small amount of diamine, which is separated by the distillation tower 10. The small amount of diamine in the gas returns to the bottom of the vertical primary tubular reactor 9, and the steam enters the condenser 11 for condensation and refluxes to the salt-forming kettle 1;

[0115] 3) The porous particles / powdered materials in step 2) enter the positive pressure stage of the secondary tubular reactor 12, and the materials are pushed forward at a rate of 508 g / min by the screw propeller provided in the secondary tubular reactor 12 to react. The reactor 12 adopts three-stage heating, the temperature of the first heating section is 220° C., the temperature of the second heating section is set to 230° C., the temperature of the third heating section is set to 250° C., the pressure is 0.5 MPa, and the residence time of the materials in each heating section is 0.3 h; the pressure difference between the primary tubular reactor 9 and the secondary tubular reactor 12 is used to realize the continuous transformation of the materials from the homogeneous fluid state to the porous particles / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powdered materials at the bottom of the cyclone separator 13 are returned to the secondary tubular reactor 12 for recycling;

[0116] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. Step 3) The porous granular / powdered material enters the negative pressure stage of the tertiary tubular reactor 16 through the continuous transfer of the first buffer tank 14 and the second buffer tank 15, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 250° C., the absolute pressure is 8 Pa, and the residence time is 2 h. The discharge after the solid-phase polymerization of the tertiary tubular reactor 16 is rapidly alternated through the third buffer tank 17 and the fourth buffer tank 18 to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realizes continuous discharge to obtain the granular / powdered PA6T / 6I / 6 final product.

[0117] Comparative Example 1

[0118] The synthesis method of high temperature resistant nylon PA6T / 66 in this comparative example 1 is different from that in Example 5 only in that the residence time in the three-stage tubular reactor is different, and the other process parameters are the same as those in Example 5. In this comparative example, the residence time in the three-stage tubular reactor is 0.3h.

[0119] Comparative Example 2

[0120] The synthesis method of high temperature resistant nylon PA6T / 66 in this comparative example is different from that in Example 5 only in that the polymerization temperature in the three-stage tubular reactor is different, and the other process parameters are the same as in Example 5. In this comparative example, the polymerization temperature in the three-stage tubular reactor is 210°C.

[0121] Comparative Example 3

[0122] The synthesis method of the high temperature resistant nylon PA6T / 66 in this comparative example is different from that in Example 5 only in that the feed amounts of terephthalic acid and adipic acid are different, and the other process parameters are the same as those in Example 1. In this comparative example, the molar ratio of the feed amounts of terephthalic acid and adipic acid is 40 / 60.

[0123] Performance Test Example 1

[0124] The performance tests were carried out on the products of the above embodiments and comparative examples, and the test equipment and test standards used are shown in Table 1:

[0125] Table 1 Test equipment and test standards used in the present invention

[0126]

[0127] The characterization results are shown in Table 2.

[0128] Table 2 Characterization results

[0129]

[0130]

[0131] It can be seen from the test results of Examples 1-5 in Table 2 that no matter it is semi-aromatic high temperature nylon, aliphatic high temperature resistant nylon, cyclic aliphatic copolymer high temperature resistant nylon, homopolymer high temperature resistant semi-aromatic nylon, homopolymer high temperature resistant semi-aromatic nylon, homopolymer high temperature resistant semi-aromatic nylon, homopolymer high temperature resistant naphthalene ring-containing nylon, or two-component high temperature resistant semi-aromatic nylon, the device and method of the present invention can achieve continuous preparation of high temperature resistant nylon products with excellent performance, indicating that the device and method of the present invention have a wide range of applications, the obtained product has a low yellow index, and the product quality is good.

[0132] Secondly, the present invention finds that the amount ratio of the raw materials has a certain influence on the performance of the product. To illustrate the influence of different molar ratios of dibasic acid and diamine on the performance of the product, the present invention takes copolymerized nylon PA6T / 66 as an example, and prepares copolymerized nylon PA6T / 66 with different molar ratios of dibasic acid and diamine respectively. The test results are shown in Examples 5-8 in Table 2. It can be seen from the test results that the different molar ratios of dibasic acid and diamine have a great influence on the physical properties of copolymerized nylon PA6T / 66, especially on its melting point. It also proves that as the terephthalic acid component decreases (Comparative Example 3), the melting point of the product gradually decreases.

[0133] In addition, the polymerization time and polymerization temperature will also have a certain impact on the performance of the product. For example, in Comparative Examples 1 and 2, by shortening the polymerization time of the three-stage reactor, the relative viscosity and mechanical properties of the final polymer are reduced; by lowering the polymerization temperature of the three-stage reactor, the relative viscosity and mechanical properties of the final polymer are reduced;

[0134] Performance Test Example 2

[0135] To further illustrate the effect of the present invention, the high temperature resistant PA6T / 66 obtained in Example 5 was taken as an example to conduct FT-IR, 1 HNMR, DSC and TG tests, the results are as follows Figure 2 , Figure 3 , Figure 4 and Figure 5 shown.

[0136] Figure 2 Medium, 3308cm -1 is the stretching vibration peak of NH, 2931cm -1 and 2857cm -1 They are CH 2 The antisymmetric stretching vibration peak and symmetric stretching vibration peak, 1634cm -1 It is the stretching vibration peak of C=O (amide I band), 1538cm -1 It is the NH in-plane bending vibration peak (amide II band), 3081cm -1 It is the doublet peak of the combination of NH and CN vibration peaks, 863cm -1It is the in-plane bending vibration peak of CH on the benzene ring. Figure 3 The chemical shift of each H is shown. Figure 4 PA6T / 66 (60 / 40) is shown, and its melting point is 312°C. Figure 5 For PA6T / 66 (60 / 40), the initial thermal decomposition temperature is 423°C and the fastest thermal decomposition temperature is 456°C.

[0137] The above embodiments are only used to illustrate the detailed apparatus and method of the present invention, but the present invention is not limited to the above detailed apparatus and method, that is, it does not mean that the present invention must rely on the above detailed apparatus and method to be implemented. Those skilled in the art should understand that any improvement to the apparatus and method of the present invention, equivalent replacement of raw materials of the apparatus and product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A low-temperature continuous preparation device for high-temperature resistant nylon, characterized in that: The invention comprises a salt forming kettle (1), a heat exchanger (5), a salt solution concentration tank (7), a primary tubular reactor (9), a secondary tubular reactor (12), a tertiary tubular reactor (16) and a product collecting tank (19) which are sequentially connected by pipelines; the primary tubular reactor (9) is a vertical tubular reactor; the secondary tubular reactor (12) and the tertiary tubular reactor (16) are both horizontal tubular reactors.

2. The low-temperature continuous preparation device for high-temperature resistant nylon according to claim 1, characterized in that: At least two buffer tanks are arranged in parallel between the secondary tubular reactor (12) and the tertiary tubular reactor (16), and between the tertiary tubular reactor (16) and the product collecting tank (19); and a salt solution buffer tank (3) is arranged between the salt forming kettle (1) and the heat exchanger (5).

3. The low-temperature continuous preparation device for high-temperature resistant nylon according to any one of claims 1-2, characterized in that: The exhaust port of the two-stage tubular reactor (12) is provided with a cyclone separator (13), and the material outlet at the bottom of the cyclone separator (13) is connected to the two-stage tubular reactor (12).

4. The low-temperature continuous preparation device for high-temperature resistant nylon according to any one of claims 1 to 3, characterized in that: The low-temperature continuous preparation device for high-temperature resistant nylon further comprises a distillation tower (10) connected to the top exhaust port of the first-stage tubular reactor (9), the distillation tower (10) comprising a top exhaust port, a bottom discharge port and a side feed port located in the middle of the tower body, the top exhaust port of the distillation tower (10) being connected to a salt kettle (1) via a pipeline, and the bottom discharge port of the distillation tower (10) being connected to a feed port provided at the bottom of the first-stage tubular reactor (9).

5. The low-temperature continuous preparation device for high-temperature resistant nylon according to claim 4, characterized in that: A condensation tank (11) is arranged between the distillation tower (10) and the salt-forming kettle (1), and between the salt solution concentration tank (7) and the salt-forming kettle (1).

6. The low-temperature continuous preparation device for high-temperature resistant nylon according to claim 5, characterized in that: Metering pumps are provided between the salt forming kettle (1) and the hydrochloric acid buffer tank (3), between the hydrochloric acid buffer tank (3) and the heat exchanger (5), between the heat exchanger (5) and the salt solution concentration tank (7), and between the salt solution concentration tank (7) and the first-stage tubular reactor (9).

7. A method for low temperature continuous preparation of high temperature resistant nylon, characterized in that: It includes a neutralization and salt-forming stage, a first-stage tubular reactor reaction stage, a second-stage tubular reactor polymerization stage, and a third-stage tubular reactor polymerization stage; 1) Neutralization and salt-forming stage: In an inert gas atmosphere, diamine at a rate of 100 g / min to 500 g / min, dibasic acid at a rate of 100 g / min to 500 g / min, water at a rate of 100 g / min to 500 g / min and auxiliary agent at a rate of 0.5 g / min to 3 g / min are uniformly introduced into the salt-forming reactor (1), and the residence time is 0.3 h to 1 h at 40°C to 90°C, to obtain a nylon salt solution with a concentration of 25% to 50%; 2) Primary tubular reactor stage: The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank (3) through the dilute salt solution metering pump (2) at a rate of 530 g / min to 1100 g / min, and then uniformly transported to the heat exchanger (5) through the dilute salt solution buffer metering pump (4) at a rate of 450 g / min to 1000 g / min. At this time, the dilute salt solution at the outlet of the heat exchanger (5) is 140°C to 180°C. The high-temperature dilute salt solution after heat exchange is uniformly transported to the salt solution concentration tank (7) through the high-temperature dilute salt solution metering pump (6) at a rate of 390 g / min to 1000 g / min, and concentrated to 50% to 90% at 140°C to 180°C. The concentrated salt solution is heated at a rate of 370 g / min to 750 g / min. The material is uniformly transported to the primary tubular reactor (9) at a rate of g / min through a high-temperature concentrated salt solution metering pump (8), and the retention time is 0.2h to 1.5h at 190°C to 230°C, and the pressure is 1.5MPa to 2.4MPa. The material reacts continuously from bottom to top in the primary tubular reactor (9), and is uniformly and continuously transported to the secondary tubular reactor (12) at a rate of 370 g / min to 750 g / min. 3) Secondary tubular reactor polymerization stage: The porous granular / powdered material in step 2) enters the secondary tubular reactor (12) in the positive pressure stage, and is pushed forward by a screw propeller provided in the secondary tubular reactor (12) at a rate of 370 g / min to 750 g / min to react while moving forward; the polymerization reaction temperature of the secondary tubular reactor (12) is 220° C. to 250° C., the reaction pressure is 0.2 MPa to 1.0 MPa, and the residence time is 0.6 h to 1.5 h; 4) Three-stage tubular reactor polymerization stage: Step 3) The porous granular / powdered material passes through the continuous transfer of the first buffer tank (14) and the second buffer tank (15) and enters the negative pressure stage of the three-stage tubular reactor (16), and further solid phase polymerization is performed to obtain the final product; the temperature of the solid phase polymerization is 220° C. to 250° C., the absolute pressure is 5 Pa to 500 Pa, and the residence time is 0.5 h to 3 h.

8. The low-temperature continuous preparation method of high-temperature resistant nylon according to claim 7, characterized in that: In the step 1), the diamine is a mixture of one or more of an aliphatic diamine, an aromatic diamine, an alicyclic diamine and a naphthalene ring-containing diamine, and the diamine is preferably butanediamine, pentanediamine, hexanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, m-xylylenediamine, p-xylylenediamine, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, 1,5-diamino The dibasic acid is a mixture of one or more of aliphatic dibasic acid, aromatic dibasic acid, alicyclic dibasic acid and naphthalene ring dibasic acid, and the dibasic acid is preferably a mixture of one or more of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid, terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid and 1,4-cyclohexane dicarboxylic acid; the pH value of the nylon salt solution is 7.0-7.

5.

9. The low-temperature continuous preparation method of high-temperature resistant nylon according to claim 7, characterized in that: In step 2), the primary tubular reactor (9) is equipped with a distillation tower (10) and a condenser (11). The exhaust gas from the top of the primary tubular reactor (9) is separated by passing through the distillation tower (10). A small amount of diamine in the gas phase is returned to the primary tubular reactor (9) to keep the material composition in the primary tubular reactor (9) constant. The other fractions are returned to the salt-forming kettle (1) through the condenser (11) for recycling. In step 3), the secondary tubular reactor (12) is equipped with a cyclone separator (13) at the exhaust port. The powdered material at the bottom of the cyclone separator (13) is returned to the secondary tubular reactor (12) for recycling.

10. The low-temperature continuous preparation method of high-temperature resistant nylon according to claim 7, characterized in that: In step 3), the secondary tubular reactor (12) is a positive pressure system, and three heating sections are arranged along the material flow direction, wherein the temperature of the first heating section is 200°C to 220°C, the temperature of the second heating section is set to 210°C to 230°C, and the temperature of the third heating section is set to 220°C to 250°C, and the residence time of the material in each heating section is 0.2h to 0.5h; in step 4), the discharge of the tertiary tubular reactor (16) after solid phase polymerization is rapidly alternated through the third buffer tank (17) and the fourth buffer tank (18) to realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally collected in the product collection tank (19).

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