A low-temperature continuous preparation device and method of high-temperature-resistant nylon

Abstract

The application belongs to the technical field of polymer material synthesis, and particularly relates to a low-temperature continuous preparation device and method of high-temperature-resistant nylon, which mainly comprises the following steps: a neutralization and salting stage, a first-stage tubular reactor stage, a second-stage tubular reactor stage and a third-stage tubular reactor stage, so as to realize continuous input of raw materials such as binary acid and binary amine and continuous output of high-temperature-resistant nylon products. The device and method are suitable for preparation of homopolymerization and copolymerization high-temperature-resistant nylon, such as semi-aromatic nylon, alicyclic nylon and naphthalene ring-containing nylon, have wide application, low polymerization temperature, short polymerization time, stable composition, good product quality, low yellow index, high whiteness, stable performance, realize reflux of diamine and recovery of materials, reduce generation and emission of three wastes and reduce production cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer material synthesis, and particularly relates to a low-temperature continuous preparation device and method of high-temperature-resistant nylon. BACKGROUND

[0002] Polyamide, commonly known as nylon, has good comprehensive performance, including mechanical properties, heat resistance, wear resistance, chemical resistance, self-lubricity, and low friction coefficient, and is widely used in the fields of automobile parts, electronic appliances, and engineering parts.

[0003] At present, the preparation methods of high-temperature-resistant nylon mainly include batch polymerization, direct solid-phase polymerization, and melt continuous method. CN 112358611 B, CN 115850692 B, CN 113999388 B, CN 105061755 B, CN 104327265 B, CN 101768266 B, and CN 117986569 A, etc. prepared high-temperature-resistant nylon by using the batch polymerization method, which is carried out in two steps, i.e., prepolymerization and solid-phase post-polymerization, and the specific steps are as follows: first, a high-temperature-resistant nylon prepolymer is prepared at 210℃-240℃, and then the viscosity is increased at 230℃-260℃; this method has high reaction temperature, long preparation period, high energy consumption, low efficiency, many side reactions, and the product is prone to yellowing and gelation, which affects the performance of the product. The patent CN 112979941 B of the research group prepared high-temperature-resistant nylon by using the direct solid-phase polymerization method, which continuously fed the initial powdery nylon salt, and after the reactor combination, the powder nylon product was obtained by continuous discharge; this method has low reaction temperature, few side reactions, low yellow index of the obtained product, and good product quality, but it needs to prepare the powdery nylon salt first. For homopolymer high-temperature-resistant nylon, the production efficiency is high and the reaction time is short, but for copolymer high-temperature-resistant nylon, the polymerization time is long, the production efficiency is low, and the composition is easy to be unbalanced. CN 114316255 A, CN 115873236 A, and CN 110684190 B, etc. prepared high-temperature-resistant nylon by using the continuous melt extrusion method, and the reaction temperature was above the melting point; although the preparation efficiency was high and the performance was stable, there were problems such as high reaction temperature, many side reactions, high yellow index, high energy consumption, and poor product quality. CN 117264197 A introduced a continuous production method and device of semi-aromatic nylon, which directly sprayed into the drying tower by using the flash evaporation principle, but under the spray pressure, the prepolymer had low reaction degree and contained a certain amount of unreacted nylon salt, which was easy to be gasified at this temperature when the first-stage negative pressure polymerization was carried out, resulting in the difference between the composition of the final product and the feeding ratio.

[0004] No matter intermittent polymerization method, direct solid-phase polymerization method or current continuous polymerization method has its shortcomings, therefore, in order to efficiently prepare high-temperature resistant nylon product with stable performance, constant macromolecular chain composition and good quality, it is necessary to provide a low-temperature continuous preparation device and method of high-temperature resistant nylon. SUMMARY

[0005] The present application aims to provide a low-temperature continuous preparation device of high-temperature resistant nylon, and its preparation method is the second application purpose of the present application. The material residence time is short, and the preparation efficiency is high by using the device and process method of the present application. From the continuous input of diacid and diamine to the continuous output of high-temperature resistant nylon product, the overall residence time is within 7h, the reaction temperature of the whole reaction system is between 190℃ and 250℃, the reaction temperature is more than 50℃ lower than the melting point of the product, the reaction temperature is low, the occurrence of side reactions is effectively avoided, the yellow index of the product is low, and the product quality is good.

[0006] In order to achieve the above application purpose, the present application adopts the following technical scheme:

[0007] A low-temperature continuous preparation device of high-temperature resistant nylon comprises a salting kettle 1, a heat exchanger 5, a salt liquid concentration tank 7, a first-stage tubular reactor 9, a second-stage tubular reactor 12, a third-stage tubular reactor 16 and a product collection tank 19 which are connected by pipelines in sequence; the first-stage tubular reactor 9 is a vertical tubular reactor; the second-stage tubular reactor 12 and the third-stage tubular reactor 16 are both horizontal tubular reactors.

[0008] As a preferred embodiment of the present application, at least two buffer tanks are arranged in parallel between the second-stage tubular reactor 12 and the third-stage tubular reactor 16 and between the third-stage tubular reactor 16 and the product collection tank 19; a salt liquid buffer tank 3 is arranged between the salting kettle 1 and the heat exchanger 5.

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

[0010] As a further preferred embodiment of the present application, the low-temperature continuous preparation device of high-temperature resistant nylon further comprises a rectifying tower 10 which is connected with the top exhaust port of the first-stage tubular reactor 9, the rectifying tower 10 comprises 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 rectifying tower 10 is connected with the salting kettle 1 by a pipeline, and the bottom discharge port of the rectifying tower 10 is connected with the feed port arranged at the bottom of the first-stage tubular reactor 9.

[0011] As a further preferred embodiment of the present application, a condensation tank 11 is arranged between the rectifying tower 10 and the salting kettle 1 and between the salt liquid concentration tank 7 and the salting kettle 1.

[0012] As further preferred of the application, a metering pump is arranged between the salt formation 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] A second inventive purpose of the application is a method for low-temperature continuous preparation of high-temperature-resistant nylon using the device, including a neutralization and salt formation stage, a primary tubular reactor reaction stage, a secondary tubular reactor polymerization stage, and a tertiary tubular reactor polymerization stage.

[0014] 1) Neutralization and salt formation stage: under an inert gas atmosphere, the diamine enters the salt formation kettle 1 at a rate of 100 g / min to 500 g / min, the diacid enters at a rate of 100 g / min to 500 g / min, water enters at a rate of 100 g / min to 500 g / min, and the auxiliary agent enters at a rate of 0.5 g / min to 3 g / min, and stays for 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 delivered to the brine buffer tank 3 by the dilute brine metering pump 2 at a rate of 530 g / min to 1100 g / min, and then uniformly delivered to the heat exchanger 5 by the dilute brine buffer metering pump 4 at a rate of 450 g / min to 1000 g / min, at which time the dilute brine temperature at the outlet of the heat exchanger 5 is 140°C to 180°C, the high-temperature dilute brine after heat exchange is uniformly delivered to the brine concentration tank 7 by the high-temperature dilute brine metering pump 6 at a rate of 390 g / min to 1000 g / min, concentrated to 50% to 90% at 140°C to 180°C, and the concentrated brine is uniformly delivered to the primary tubular reactor 9 by the high-temperature concentrated brine metering pump 8 at a rate of 370 g / min to 750 g / min, stays for 0.2 h to 1.5 h at 190°C to 230°C, and the pressure is 1.5 MPa to 2.4 MPa, the material continuously reacts from bottom to top in the primary tubular reactor 9, while being continuously delivered to the secondary tubular reactor 12 at a rate of 370 g / min to 750 g / min, and 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 a homogeneous fluid state to a porous particle / powder state, and due to the gasification expansion of water in the system, the material becomes a porous particle structure / powder state; due to the weak alkalinity of the brine, the gas discharged in this stage contains a small amount of diamine, which is separated by the rectification column 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 condensate tank 11 to be condensed and returned to the salt formation kettle 1;

[0016] 3) Secondary tubular reactor polymerization stage: the porous granular / powder material of step 2) enters the secondary tubular reactor 12 positive pressure stage, and the material is propelled by a screw propeller at a rate of 370 g / min to 750 g / min to carry out the reaction; 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) Tertiary tubular reactor polymerization stage: the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15 into the tertiary tubular reactor 16 negative pressure stage, 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 5 Pa to 500 Pa, and the residence time is 0.5 h to 3 h.

[0018] As preferred in the present application, the primary tubular reactor 9 in step 2) is equipped with a rectifying tower 10 and a condenser tank 11, and the gas discharged from the top of the primary tubular reactor 9 is separated through the rectifying tower 10, a small amount of binary amine in the gas phase is returned to the primary tubular reactor 9 to maintain the constant composition of the material in the primary tubular reactor 9, and other fractions are returned to the salt formation kettle 1 through the condenser tank 11 for recycling; the secondary tubular reactor 12 in step 3) is provided with a cyclone separator 13 at the exhaust port, and the powder material at the bottom of the cyclone separator 13 is returned to the secondary tubular reactor 12 for recycling.

[0019] As further preferred in the present application, the secondary tubular reactor 12 in step 3) is a positive pressure system, and three heating sections are provided 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 210°C to 230°C, and the temperature of the third heating section is 220°C to 250°C, and the residence time of the material in each heating section is 0.2 h to 0.5 h. The provision of the three heating sections can more flexibly adjust the polymerization temperature to meet different polymerization conditions; the discharge of the tertiary tubular reactor (16) after the solid-phase polymerization in step 4) is quickly and alternately transferred 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 the product is finally collected in the product collection tank (19).

[0020] It can be understood that in step 1), the diamine is one or more than two kinds of mixture of aliphatic diamine, aromatic diamine, alicyclic diamine and naphthalene ring-containing diamine, including but not limited to one or more than two kinds of mixture of 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; the diacid is one or more than two kinds of mixture of aliphatic diacid, aromatic diacid, alicyclic diacid and naphthalene ring-containing diacid, including but not limited to one or more than two kinds of mixture of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid, terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid.

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

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

[0023] The primary reactor adopted in the application is a vertical tube reactor, which can ensure that the reactants flow uniformly from bottom to top in the tube and carry out polymerization reaction, has high heat transfer efficiency, fast material heating rate, large reaction rate, short residence time; the process pressure in the secondary tubular reactor is positive pressure, the temperature control adopts step temperature control, which ensures stable composition, high yield, high reaction efficiency and low production cost. The process pressure of the secondary tubular reactor is significantly smaller than that of the primary tube reactor, the water in the secondary tubular reactor is gasified, the water content of the material is reduced, which leads to the increase of the melting point of the material in the secondary tubular reactor, and realizes the continuous transformation of the material from homogeneous fluid state to porous particle / powder state. The porous or powder state is conducive to the discharge of condensed water in the secondary tubular reactor stage and the tertiary tubular reactor stage, and provides favorable conditions for the improvement of polymerization efficiency; two groups of buffer tanks are respectively arranged between the secondary tubular reactor and the tertiary tubular reactor and between the tertiary reactor and the product collecting tank for double-way rapid switching, which realizes the stability of the system process pressure and the continuous conveying of the material.

[0024] Specifically, the application realizes the continuous transformation of the material from a homogeneous fluid state to a porous particle / powder state through the interaction of the primary tube reactor pressure sensor and the regulating valve and the pressure difference between the secondary tube reactor, and the porous structure of the material provides favorable conditions for the polymerization of the secondary tube reactor stage and the tertiary tube reactor stage.

[0025] The primary tube reactor of the application is equipped with a rectifying tower and a condensate tank, and due to the weak alkalinity of the salt solution, the gas discharged from this stage contains a small amount of binary amine, which is separated by the rectifying tower, and the small amount of binary amine in the gas phase returns to the vertical primary reactor, keeping the composition of the vertical primary reactor constant, and the other fractions return to the salting kettle through the condensate tank, reducing resource consumption and sewage treatment pressure.

[0026] The secondary tube reactor of the application is a positive pressure stage, which promotes the further polymerization of unreacted nylon salt and low molecular material into higher molecular weight products, effectively prevents the gasification of nylon salt and keeps the composition constant, and further improves the conversion rate of the reaction.

[0027] The secondary tube reactor of the application is provided with a cyclone separator at the exhaust port, and the powdery material at the bottom of the cyclone separator returns to the secondary tube reactor, preventing the powdery prepolymer from being discharged with the gas flow and causing dust pollution.

[0028] The first and second buffer tanks of the application can realize the continuous transformation of the positive pressure system to the negative pressure system, and the third and fourth buffer tanks can realize the continuous transformation of the negative pressure system to the normal pressure system, thereby ensuring that the reaction system always maintains a continuous reaction state and truly realizes the requirements of continuous production. Among them, the positive pressure system of the secondary tube reactor realizes the continuous transformation to the negative pressure system of the tertiary tube reactor through the rapid alternation of the first and second buffer tanks, realizes the continuous transportation of the material, and the tertiary tube reactor and the product collection tank realize the continuous output of the material through the rapid opening and closing of the third and fourth buffer tanks, thereby maintaining the stability of the pressure of each system and reducing the influence of pressure fluctuation on the polymerization process.

[0029] In the application, the reactants flow uniformly from bottom to top in the tube and undergo polymerization reaction, the heat transfer efficiency is high, the material heating rate is fast, the reaction rate is large, the residence time is short, and the residence time distribution is narrow.

[0030] In the application, the secondary tube reactor stage is a positive pressure stage, which ensures the stability of each component, high efficiency and yield, low production cost, promotes the further polymerization of unreacted nylon salt into higher molecular weight products, effectively prevents the gasification of nylon salt and keeps the composition constant, and further improves the conversion rate of the reaction.

[0031] In the present application, the polymerization temperature of the system is below 50 DEG C of the melting point of the product, which can effectively reduce the occurrence of side reactions and improve the product quality.

[0032] In the present application, the whole polymerization pipeline and container are protected by inert gas, and the material is also transported by inert gas, which avoids the oxidation of the material at high temperature and ensures the product quality.

[0033] The continuous conversion of the third buffer tank and the fourth buffer tank is realized by rapid alternation, and the product collection tank, the third buffer tank and the fourth buffer tank are connected through a vacuum pipeline to realize the rapid switching of normal pressure and negative pressure, which can ensure the rapid discharge of the material and the normal pressure system of the product collection tank.

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

[0035] 1. The device and method of the present application are suitable for the preparation of homopolymerization and copolymerization high-temperature-resistant nylon, such as semi-aromatic nylon, alicyclic nylon and naphthalene ring-containing nylon, and have 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 application can realize the continuous input of diacid and diamine and the continuous output of high-temperature-resistant nylon product, realize the continuous switching of the device through the rapid alternation of the buffer tank, and ensure the stable pressure of each system, reduce the influence of pressure fluctuation on the polymerization process, and realize the continuous production.

[0037] 3. The reaction temperature of the whole system of the present application is 190 DEG C to 250 DEG C, which is more than 50 DEG C lower than the melting point of the product, and the reaction temperature is low, which effectively avoids the occurrence of side reactions, and the production efficiency is high, and the rectifying tower and the cyclone separator are arranged to realize the reflux of diamine and the recovery of material, reduce the generation and discharge of three wastes, and reduce the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a schematic diagram of the device of the present application.

[0039] Figures 2-5 It is the FT-IR, HNMR, DSC and TG test results of the copolymer nylon PA6T / 66 obtained in Example 5. 1 HNMR, DSC and TG test results of the copolymer nylon PA6T / 66 obtained in Example 5.

[0040] Figure 1The device for preparing high-temperature-resistant nylon in low temperature and in continuous mode comprises a salt forming kettle 1, a dilute salt solution metering pump 2, a salt solution buffer tank 3, a dilute salt solution buffer metering pump 4, a heat exchanger 5, a high-temperature dilute salt solution metering pump 6, a salt solution concentration tank 7, a high-temperature concentrated salt solution metering pump 8, a first-stage tubular reactor 9, a rectifying tower 10, a condensation tank 11, a second-stage tubular reactor 12, a cyclone separator 13, a first buffer tank 14, a second buffer tank 15, a third-stage tubular reactor 16, a third buffer tank 17, a fourth buffer tank 18, and a product collection tank 19. DETAILED DESCRIPTION

[0041] The technical scheme of the present application is further described below by means of specific examples.

[0042] The device for preparing high-temperature-resistant nylon in low temperature and in continuous mode comprises a salt forming kettle 1, a dilute salt solution metering pump 2, a salt solution buffer tank 3, a dilute salt solution buffer metering pump 4, a heat exchanger 5, a high-temperature dilute salt solution metering pump 6, a salt solution concentration tank 7, a high-temperature concentrated salt solution metering pump 8, a first-stage tubular reactor 9, a rectifying tower 10, a condensation tank 11, a second-stage tubular reactor 12, a cyclone separator 13, a first buffer tank 14, a second buffer tank 15, a third-stage tubular reactor 16, a third buffer tank 17, a fourth buffer tank 18, and a product collection tank 19. Figure 1 The device for preparing high-temperature-resistant nylon in low temperature and in continuous mode comprises a salt forming kettle 1, a dilute salt solution metering pump 2, a salt solution buffer tank 3, a dilute salt solution buffer metering pump 4, a heat exchanger 5, a high-temperature dilute salt solution metering pump 6, a salt solution concentration tank 7, a high-temperature concentrated salt solution metering pump 8, a first-stage tubular reactor 9, a rectifying tower 10, a condensation tank 11, a second-stage tubular reactor 12, a cyclone separator 13, a first buffer tank 14, a second buffer tank 15, a third-stage tubular reactor 16, a third buffer tank 17, a fourth buffer tank 18, and a product collection tank 19. Figure 1 The device for preparing high-temperature-resistant nylon in low temperature and in continuous mode comprises a salt forming kettle 1, a dilute salt solution metering pump 2, a salt solution buffer tank 3, a dilute salt solution buffer metering pump 4, a heat exchanger 5, a high-temperature dilute salt solution metering pump 6, a salt solution concentration tank 7, a high-temperature concentrated salt solution metering pump 8, a first-stage tubular reactor 9, a rectifying tower 10, a condensation tank 11, a second-stage tubular reactor 12, a cyclone separator 13, a first buffer tank 14, a second buffer tank 15, a third-stage tubular reactor 16, a third buffer tank 17, a fourth buffer tank 18, and a product collection tank 19.

[0043] In other embodiments, three heating sections can be provided along the material flow direction of the secondary tube reactor (12), wherein the temperature of the first heating section is 200-220 DEG C, the temperature of the second heating section is 210-230 DEG C, and the temperature of the third heating section is 220-250 DEG C, and the residence time of the material in each heating section is 0.2-0.5 h; the three-section heating can more flexibly adjust the polymerization temperature, meet different polymerization conditions, and ensure more accurate temperature control. It is especially suitable for the preparation of copolymer, and for the preparation of homopolymer, three-section heating is not required, and direct heating can achieve the effect of the present application.

[0044] The working process of the device for preparing high-temperature-resistant nylon at low temperature in a continuous manner is as follows:

[0045] 1) Neutralization and salting stage: under an inert gas atmosphere, the binary amine, the binary acid, water and the additive are fed into the salting kettle 1 at a rate of 100-500 g / min, 100-500 g / min, 100-500 g / min and 0.5-3 g / min respectively, and the residence time is 0.3-1 h at 40-90 DEG C, to obtain a nylon salt solution with a concentration of 25-50%;

[0046] 2) Primary tube reactor stage: the nylon salt solution of step 1) is uniformly delivered to the salt solution buffer tank 3 by the dilute salt solution metering pump 2 at a rate of 530-1100 g / min, and then uniformly delivered to the heat exchanger 5 by the dilute salt solution buffer metering pump 4 at a rate of 450-1000 g / min, at this time the temperature of the dilute salt solution at the outlet of the heat exchanger 5 is 140-180 DEG C, the high-temperature dilute salt solution after heat exchange is uniformly delivered to the salt solution concentration tank 7 by the high-temperature dilute salt solution metering pump 6 at a rate of 390-1000 g / min, concentrated to 50-90% at 140-180 DEG C, and the concentrated salt solution is uniformly delivered to the primary tube reactor 9 by the high-temperature concentrated salt solution metering pump 8 at a rate of 370-750 g / min, the residence time is 0.2-1.5 h at 190-230 DEG C, and the pressure is 1.5-2.4 MPa; the material continuously reacts from bottom to top in the primary tube reactor 9, and is continuously delivered to the secondary tube reactor 12 at a rate of 370-750 g / min; the pressure difference between the primary tube reactor 9 and the secondary tube reactor 12 is utilized to realize the continuous transformation of the material from a homogeneous fluid state to a porous particle / powder state, and the gasification expansion of water in the system causes the material to become a porous particle structure / powder state; due to the weak alkalinity of the salt solution, the gas discharged in this stage contains a small amount of binary amine, which is separated by the rectification tower 10, and the small amount of binary amine in the gas returns to the bottom of the vertical primary tube reactor 9, and the steam enters the condensation tank 11 to be condensed and returned to the salting kettle 1;

[0047] 3) Secondary tube reactor polymerization stage: the porous granular / powder material of step 2) enters the secondary tube reactor 12 positive pressure stage, and the material is propelled at a rate of 370 g / min to 750 g / min by a spiral propeller arranged in the secondary tube reactor 12 to carry out the reaction while moving forward; the secondary tube 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, the powder material is collected at the bottom and returned to the secondary tube reactor 12 for recycling; the secondary tube reactor 12 is a positive pressure system, in various embodiments of the present application, the reaction temperature of the secondary tube 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; in other embodiments, the secondary tube reactor can also be provided with three heating sections along the material flow direction, wherein the temperature of one heating section is 200°C to 220°C, the temperature of the second heating section is 210°C to 230°C, and the temperature of the third heating section is 220°C to 250°C, and the residence time of the material in each heating section is 0.2 h to 0.5 h; the setting of three heating sections can more flexibly adjust the polymerization temperature to meet different polymerization conditions;

[0048] 4) Tertiary tube reactor polymerization stage: the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15 into the tertiary tube reactor 16 negative pressure stage, and is further solid-phase polymerized to obtain the final product; the solid-phase polymerization temperature 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; the material discharged after the solid-phase polymerization of the tertiary tube reactor 16 is quickly and alternately transferred 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 the product is finally collected in the product collection tank 19.

[0049] It can be understood that in step 1), the diamine is one or more than two kinds of mixture of aliphatic diamine, aromatic diamine, alicyclic diamine and naphthalene ring-containing diamine, and the diamine is preferably one or more than two kinds of mixture of butanediamine, pentanediamine, hexanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, m-xylylenediamine, p-xylylenediamine, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, and 1,5-diaminonaphthalene; the diacid is one or more than two kinds of mixture of aliphatic diacid, aromatic diacid, alicyclic diacid and naphthalene ring-containing diacid, and the diacid is preferably one or more than two kinds of mixture 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 to 7.5.

[0050] It can be understood that the salt formation stage in step 1) includes catalyst and antioxidant. The catalyst is one or more of sodium hypophosphite, sodium hypophosphite, triphenyl phosphate, H10, and the amount of catalyst is 0.1% to 0.6% of the dry mass of the diacid and diamine. The antioxidant is one or more of sodium hypophosphite, antioxidant 1010, antioxidant S9228, antioxidant SH120, and antioxidant B215, and the amount of antioxidant is 0.1% to 0.6% of the dry mass of the diacid and diamine.

[0051] Example 1

[0052] This example uses Figure 1 The device shown in the method for continuous production of semi-aromatic copolymer high-temperature-resistant nylon PA5T / 56 at low temperature, the steps are:

[0053] 1) In a nitrogen atmosphere, pentanediamine, terephthalic acid, adipic acid (molar ratio of terephthalic acid to adipic acid is 60:40), water and sodium hypophosphite are transported into a 40℃ salt formation kettle 1 at a rate of 206g / min, 199.2g / min, 116.8g / min, 261g / min and 0.5g / min respectively, the residence time is 0.5h, the nylon salt solution at the outlet of the salt formation kettle is 50%; the pH value of the nylon salt solution is 7.0-7.5; the inert gas in this example is nitrogen, in other examples, carbon dioxide gas and argon gas can also be selected;

[0054] 2) The nylon salt solution of step 1) is uniformly transported into the salt solution buffer tank 3 by the dilute salt solution metering pump 2 at a rate of 783.5g / min, and then uniformly transported into the heat exchanger 5 by the dilute salt solution buffer metering pump 4 at a rate of 680g / min, at this time the temperature of the dilute salt solution at the outlet of the heat exchanger 5 is 180℃, the nylon salt solution passes through the heat exchanger 5 and is uniformly and continuously transported into the 180℃ salt solution concentration tank 7 by the high-temperature dilute salt solution metering pump 6 at a rate of 680g / min, the nylon salt solution at the outlet of the salt solution concentration tank 7 is 90%; the nylon salt concentrate is immediately transported into the first-stage tubular reactor 9 by the high-temperature concentrated salt solution metering pump 8 at a rate of 499g / min, the temperature in the first-stage tubular reactor 9 is 210℃, the pressure is 1.7MPa, and the residence time is 1.0h, the material continuously reacts in the tubular reactor from bottom to top, while being uniformly and continuously transported into the second-stage tubular reactor 12 at a rate of 475g / min, the gas discharged in this stage contains a small amount of diamine, which is separated by the rectifying column 10, the small amount of diamine in the gas returns to the bottom of the first-stage vertical tubular reactor 9, and the steam enters the condenser 11 to condense and return to the salt formation kettle 1;

[0055] 3) The porous particles / powder material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is propelled by the spiral propeller arranged in the secondary tubular reactor 12 at a rate of 475 g / min while reacting, the secondary tubular reactor 12 is heated in three stages, the temperature of the first heating stage is set to 210℃, the temperature of the second heating stage is set to 230℃, and the temperature of the third heating stage is set to 240℃, the pressure is 0.5 MPa, the first stage residence time is 0.2 h, the second stage residence time is 0.3 h, and the third stage residence time 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 a homogeneous fluid state to a porous particle / 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, and the porous particles / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15, enters the negative pressure stage of the tertiary tubular reactor 16, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 240℃, the absolute pressure is 8 Pa, and the residence time is 2 h; the discharged material after solid-phase polymerization in the tertiary tubular reactor 16 is quickly 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 the continuous discharge to obtain the granular / powder PA5T / 56 final product which is collected in the product collection tank.

[0057] Example 2

[0058] This example uses the device as shown in Figure 1 to continuously prepare aliphatic high-temperature-resistant nylon PA46 at low temperature, the steps are as follows:

[0059] 1) In a nitrogen atmosphere, butanediamine, adipic acid, water and sodium hypophosphite are respectively transported into a 50℃ salt formation kettle at a rate of 176 g / min, 292 g / min, 117 g / min and 2.8 g / min, the residence time is 0.3 h, and the nylon salt solution at the outlet of the salt formation kettle is 25%;

[0060] 2) The nylon salt solution of step 1) is uniformly delivered by the dilute salt solution metering pump 2 at a rate of 587.8 g / min to the salt solution buffer tank 3, and then uniformly delivered by the dilute salt solution buffer metering pump 4 at a rate of 485 g / min to the heat exchanger 5, at which time the dilute salt solution temperature at the outlet of the heat exchanger 5 is 140°C, and the nylon salt solution is continuously delivered through the heat exchanger 5 by the high-temperature dilute salt solution metering pump 6 at a rate of 485 g / min to the salt solution concentration tank 7 at 170°C, and the nylon salt solution at the outlet of the salt solution concentration tank 7 is 50%; the nylon salt solution concentrate is then delivered by the high-temperature concentrated salt solution metering pump 8 at a rate of 446.2 g / min to the first-stage tubular reactor 9, the temperature in the first-stage tubular reactor 9 is 190°C, the pressure is 1.5 MPa, and the residence time is 0.2 h; the material continuously reacts from bottom to top in the first-stage tubular reactor 9, and is uniformly and continuously delivered at a rate of 420 g / min to the second-stage tubular reactor 12, the gas discharged at this stage contains a small amount of diamine, which is separated by the rectification column 10, and the small amount of diamine in the gas is returned to the bottom of the vertical first-stage tubular reactor 9, and the steam is condensed in the condensation tank 11 and returned to the salt formation kettle 1;

[0061] 3) The porous granular / powder material of step 2) enters the positive pressure stage of the second-stage tubular reactor 12, and the material is propelled by the spiral propeller provided in the second-stage tubular reactor 12 at a rate of 420 g / min to continuously react as it is propelled forward, the temperature in the second-stage 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 first-stage tubular reactor 9 and the second-stage tubular reactor 12 is utilized to continuously transform the material from a homogeneous fluid state to a porous granular / powder state; the second-stage tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powder material at the bottom of the cyclone separator 13 is returned to the second-stage tubular reactor 12 for recycling;

[0062] 4) The material is delivered from the second-stage tubular reactor to the third-stage tubular reactor 16, the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15, and enters the negative pressure stage of the third-stage tubular reactor 16 to further solid-phase polymerize to obtain the final product; the temperature in the third-stage tubular reactor 16 is 220°C, the absolute pressure is 5 Pa, and the residence time is 0.5 h; the material after solid-phase polymerization in the third-stage tubular reactor 16 is delivered through the third buffer tank 17 and the fourth buffer tank 18 to rapidly and alternately realize the continuous transformation of the system from the negative pressure stage to the normal pressure system, and finally realize continuous delivery to obtain the granular / powder PA46 final product.

[0063] Example 3

[0064] This example utilizes the device shown in Figure 1 to continuously prepare an alicyclic copolymer high-temperature resistant nylon PA6C / 66 at low temperature, and the steps are as follows:

[0065] 1) Hexanediamine, adipic acid, cyclohexanedicarboxylic acid (molar ratio of cyclohexanedicarboxylic acid to adipic acid 60 / 40), water and sodium hypophosphite were fed into a 60 °C salt formation tank 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 under a nitrogen atmosphere, the residence time was 0.6 h, and the nylon salt solution at the outlet of the salt formation tank 1 was 40%;

[0066] 2) The nylon salt solution of step 1) was uniformly fed into a salt solution buffer tank 3 by a dilute salt solution metering pump 2 at a rate of 637.48 g / min, and then uniformly fed into a heat exchanger 5 by a dilute salt solution buffer metering pump 4 at a rate of 530 g / min, at which time the temperature of the dilute salt solution at the outlet of the heat exchanger 5 was 160 °C; the nylon salt solution passed through the heat exchanger 5 and continuously entered a 160 °C salt solution concentration tank 7 by a 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 was 75%; the nylon salt concentrate was immediately fed into a first-stage tubular reactor 9 by a high-temperature concentrated salt solution metering pump 8 at a rate of 397 g / min, the temperature in the reactor was 220 °C, the pressure was 2.1 MPa, and the residence time was 0.8 h; the material continuously reacted in the tubular reactor from bottom to top, while being uniformly and continuously fed into a second-stage tubular reactor 12 at a rate of 375 g / min, the gas discharged in this stage contained a small amount of diamine, which was separated by a rectifying column 10, and the small amount of diamine in the gas returned to the bottom of the first-stage vertical tubular reactor 9, and the steam entered a condensation tank 11 to be condensed and returned to the salt formation tank 1;

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

[0068] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. The porous granular / powdered material is continuously transferred through the first buffer tank 14 and the second buffer tank 15 to enter the negative pressure stage of the tertiary tubular reactor 16, and further solid-phase polymerization 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 material after solid-phase polymerization in the tertiary tubular reactor 16 is continuously converted from the negative pressure stage to the normal pressure system by rapid alternation of the third buffer tank 17 and the fourth buffer tank 18, and finally realizes continuous discharge to obtain the granular / powdered PA6C / 66 final product.

[0069] Example 4

[0070] This example uses the device as shown in Figure 1 to continuously prepare semi-aromatic high-temperature-resistant nylon PA10T at low temperature. The steps are as follows:

[0071] 1) In a nitrogen atmosphere, decanediamine, terephthalic acid, water, and sodium hypophosphite are transported into the 90°C salt formation kettle 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 h, and the nylon salt solution at the outlet of the salt formation kettle 1 is 40%;

[0072] 2) The nylon salt solution of step 1) is uniformly transported through the dilute salt solution metering pump 2 at a rate of 947.9 g / min into the salt solution buffer tank 3, and then uniformly transported through the dilute salt solution buffer metering pump 4 at a rate of 840 g / min into the heat exchanger 5. At this time, the temperature of the dilute salt solution at the outlet of the heat exchanger 5 is 180°C. The nylon salt solution passes through the heat exchanger 5 and is continuously transported into 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. The nylon salt solution at the outlet of the concentration tank 7 is 75%. The nylon salt concentrate is immediately transported into the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8 at a rate of 630 g / min. The temperature in the reactor is 230°C, the pressure is 2.4 MPa, and the residence time is 1.5 h. The material continuously reacts from bottom to top in the tubular reactor, and is uniformly and continuously transported into the secondary tubular reactor 12 at a rate of 600 g / min. The gas discharged at this stage contains a small amount of diamine, which is separated through the rectification column 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 condensation tank 11 to be condensed and returned to the salt formation kettle 1.

[0073] 3) The porous granular / powder material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is propelled by the spiral propeller arranged in the secondary tubular reactor 12 at a rate of 600 g / min while being subjected to a reaction, 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 utilized to realize the continuous transformation of the material from a homogeneous fluid state to a porous granular / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powder 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, and the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15 to enter the negative pressure stage of the tertiary tubular reactor 16, and is further subjected to solid-phase polymerization 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 material after solid-phase polymerization in the tertiary tubular reactor 16 is quickly and alternately transferred 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 the continuous discharge to obtain the granular / powder PA10T final product.

[0075] Example 5

[0076] This example utilizes the device as shown in Figure 1 to continuously prepare semi-aromatic copolymerized high-temperature-resistant nylon PA6T / 66 at low temperature, and the steps are as follows:

[0077] 1) In a nitrogen atmosphere, hexamethylene diamine, terephthalic acid, adipic acid (the molar ratio of terephthalic acid to adipic acid is 60:40), water, and sodium hypophosphite are respectively transported to a 60°C salting 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, and the residence time is 1 h, and the nylon salt solution at the outlet of the salting kettle is 40%;

[0078] 2) The nylon salt solution of step 1) is uniformly delivered by the dilute salt solution metering pump 2 at a rate of 771.45 g / min to the salt solution buffer tank 3, and then uniformly delivered by the dilute salt solution buffer metering pump 4 at a rate of 665 g / min to the heat exchanger 5, at which time the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution is continuously delivered through the heat exchanger by the high-temperature dilute salt solution metering pump 6 at a rate of 665 g / min to the 180°C salt solution concentration tank, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt solution concentrate is then delivered by the high-temperature concentrated salt solution metering pump 8 at a rate of 498.75 g / min to the first-stage shell-and-tube reactor 9, the temperature in the reactor is 220°C, the pressure is 2.1 MPa, and the residence time is 1.0 h; the material continuously reacts in the shell from bottom to top, and is uniformly and continuously delivered at a rate of 473 g / min to the second-stage tubular reactor 12, and the gas discharged in this stage contains a small amount of diamine, which is separated by the rectification column 10, and the small amount of diamine in the gas is returned to the bottom of the first-stage vertical shell-and-tube reactor 9, and the steam is condensed in the condensation tank 11 and returned to the salt formation kettle 1;

[0079] 3) The porous granular / powder material of step 2) enters the second-stage tubular reactor 12 in the positive pressure stage, and the material is propelled by the spiral propeller provided in the second-stage tubular reactor 12 at a rate of 473 g / min to continuously react as it is propelled forward; the reactor 12 is heated in three stages, the temperature of the first heating stage is 220°C, the temperature of the second heating stage is set to 230°C, and the temperature of the third heating stage is set to 240°C, the pressure is 1.0 MPa, the first-stage residence time is 0.2 h, the second-stage residence time is 0.3 h, and the third-stage residence time is 0.4 h; the pressure difference between the first-stage shell-and-tube reactor 9 and the second-stage tubular reactor 12 is used to continuously convert the material from a homogeneous fluid state to a porous granular / powder state; the second-stage tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powder material at the bottom of the cyclone separator 13 is returned to the second-stage tubular reactor 12 for recycling;

[0080] 4) The material is delivered from the second-stage tubular reactor to the third-stage tubular reactor 16, the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15, and enters the third-stage tubular reactor 16 in the negative pressure stage to further solid-phase polymerize to obtain the final product; the temperature in the third-stage tubular reactor 16 is 240°C, the absolute pressure is 100 Pa, and the residence time is 3.0 h; the material after solid-phase polymerization in the third-stage tubular reactor 16 is quickly and alternately transferred through the third buffer tank 17 and the fourth buffer tank 18 to continuously convert the system from the negative pressure stage to the normal pressure system, and finally continuously discharge to obtain the granular / powder PA6T / 66 final product.

[0081] Example 6

[0082] This example utilizes the process as described in Figure 1The method for the low-temperature continuous preparation of semi-aromatic copolymer high-temperature resistant nylon PA6T / 66 using the apparatus shown is the same as in Example 5, except that the amounts of each raw material are different. In this example, the flow rates of each raw material are as follows: 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 reactor at rates 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 utilizes, as Figure 1 The method for the low-temperature continuous preparation of semi-aromatic copolymer high-temperature resistant nylon PA6T / 66 using the apparatus shown is the same as in Example 5, except that the flow rates of each raw material in this example are as follows: hexamethylenediamine, terephthalic acid, adipic acid (molar ratio of terephthalic acid to adipic acid is 55:45), water, and additives are continuously added to the salt-forming reactor at rates 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 utilizes, as Figure 1 The method for the low-temperature continuous preparation of semi-aromatic copolymer high-temperature resistant nylon PA6T / 66 using the apparatus shown is the same as in Example 5, except that the flow rates of each raw material in this example are as follows: hexamethylenediamine, terephthalic acid, adipic acid (molar ratio of terephthalic acid to adipic acid is 65:35), water, and additives are continuously fed into the salt-forming reactor at rates 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 utilizes, as Figure 1 The method for low-temperature continuous preparation of naphthalene-containing high-temperature resistant nylon PA10N using the apparatus shown includes the following steps:

[0089] 1) In a nitrogen atmosphere, decanediamine, 2,6-dinaphthoic acid, water and phosphorous acid were fed into an 80°C salt-forming reactor at rates of 344 g / min, 432 g / min, 310.4 g / min and 1.2 g / min, respectively, with a residence time of 1 h. The nylon salt solution at the outlet of the salt-forming reactor was 40%.

[0090] 2) The nylon salt solution of step 1) is uniformly delivered by the dilute salt solution metering pump 2 at a rate of 1087.6 g / min to the salt solution buffer tank 3, and then uniformly delivered by the dilute salt solution buffer metering pump 4 at a rate of 986 g / min to the heat exchanger 5, at which time the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution continuously enters the 180°C salt solution concentration tank through the heat exchanger at a rate of 986 g / min by 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 concentrated solution immediately enters the first-stage shell-and-tube reactor 9 at a rate of 739 g / min by the high-temperature concentrated salt solution metering pump 8, the temperature in the reactor is 230°C, the pressure is 2.4 MPa, and the residence time is 1.0 h; the material continuously reacts in the shell from bottom to top, and is uniformly and continuously delivered to the second-stage tube reactor 12 at a rate of 712 g / min, the gas discharged in this stage contains a small amount of diamine, which is separated by the rectification tower 10, the small amount of diamine in the gas returns to the bottom of the first-stage vertical shell-and-tube reactor 9, and the steam enters the condensation tank 11 to be condensed and returned to the salt formation kettle 1;

[0091] 3) The porous granular / powder material of step 2) enters the second-stage tube reactor 12 in the positive pressure stage, and the material is propelled forward by the spiral propeller arranged in the second-stage tube reactor 12 at a rate of 712 g / min to react, 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 first-stage shell-and-tube reactor 9 and the second-stage tube reactor 12 is utilized to realize the continuous transformation of the material from the homogeneous fluid state to the porous granular / powder state; the second-stage tube reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powder material at the bottom of the cyclone separator 13 returns to the second-stage tube reactor 12 for recycling;

[0092] 4) The material is delivered from the second-stage tube reactor to the third-stage tube reactor 16, the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15, enters the third-stage tube reactor 16 in the negative pressure stage, and is further solid-phase polymerized to obtain the final product; the temperature in the third-stage tube reactor 16 is 250°C, the absolute pressure is 5 Pa, and the residence time is 3.0 h; the material after the solid-phase polymerization of the third-stage tube reactor 16 is quickly and alternately transferred 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 the continuous delivery to obtain the granular / powder PA10N final product.

[0093] Example 10

[0094] This example utilizes the device as shown in Figure 1 to continuously prepare the semi-aromatic copolymer high-temperature resistant nylon PA6T / 10T at low temperature, and the steps are as follows:

[0095] 1) In a nitrogen atmosphere, hexamethylene diamine, decamethylene diamine (molar ratio of hexamethylene diamine and decamethylene diamine is 65:35), terephthalic acid, water and sodium hypophosphite are fed into a 80°C salt making tank 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, with a residence time of 1 h, and the nylon salt solution at the outlet of the salt making tank is 40%;

[0096] 2) The nylon salt solution of step 1) is uniformly fed into a salt solution buffer tank 3 by a dilute salt solution metering pump 2 at a rate of 845.18 g / min, and then uniformly fed into a heat exchanger 5 by a dilute salt solution buffer metering pump 4 at a rate of 744 g / min, at which time the temperature of the dilute salt solution at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution is continuously fed into a 180°C salt solution concentration tank by a high temperature dilute salt solution metering pump 6 at a rate of 744 g / min after passing through the heat exchanger, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrate is immediately fed into a first-stage shell-and-tube reactor 9 by a high temperature concentrated salt solution metering pump 8 at a rate of 558 g / min, the temperature in the reactor is 220°C, the pressure is 2.1 MPa, and the residence time is 1.0 h; the material continuously reacts in the shell-and-tube from bottom to top, while being uniformly and continuously fed into a second-stage tubular reactor 12 at a rate of 533 g / min, and the gas discharged in this stage contains a small amount of diamine, which is separated by a rectifying column 10, and the small amount of diamine in the gas is returned to the bottom of the first-stage vertical shell-and-tube reactor 9, and the steam is condensed in a condensation tank 11 and returned to the salt making tank 1;

[0097] 3) The porous granular / powder material of step 2) enters the positive pressure stage of the second-stage tubular reactor 12, and the material is pushed forward by a screw propeller arranged in the second-stage tubular reactor 12 at a rate of 533 g / min to carry out the reaction, 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, and 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-stage shell-and-tube reactor 9 and the second-stage tubular reactor 12 is utilized to realize the continuous transformation of the material from a homogeneous fluid state to a porous granular / powder state; a cyclone separator 13 is arranged at the exhaust port of the second-stage tubular reactor 12, and the powder material at the bottom of the cyclone separator 13 is returned to the second-stage tubular reactor 12 for recycling;

[0098] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16. The porous granular / powdered material is continuously transferred through the first buffer tank 14 and the second buffer tank 15 to enter the negative pressure stage of the tertiary tubular reactor 16, and further solid-phase polymerization 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 material after the solid-phase polymerization in the tertiary tubular reactor 16 is continuously converted from the negative pressure stage to the normal pressure system through the rapid alternation of the third buffer tank 17 and the fourth buffer tank 18, and finally realizes continuous discharge to obtain the granular / powdered PA6T / 10T final product.

[0099] Example 11

[0100] This example uses the device shown in Figure 1 to continuously prepare semi-aromatic copolymer high-temperature-resistant nylon MXD6 at low temperature. The steps are as follows:

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

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

[0103] 3) The porous granular / powder material of step 2) enters the positive pressure stage of the secondary tubular reactor 12, and is propelled by the spiral propeller arranged in the secondary tubular reactor 12 at a rate of 433 g / min while reacting, the temperature in the reactor is 240℃, 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 utilized to realize the continuous transformation of the material from a homogeneous fluid state to a porous granular / powder state; the secondary tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powder 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, and the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15, and enters the negative pressure stage of the tertiary tubular reactor 16, and is further solid-phase polymerized to obtain the final product; the temperature in the tertiary tubular reactor 16 is 240℃, the absolute pressure is 200 Pa, and the residence time is 3 h; the material after solid-phase polymerization in the tertiary tubular reactor 16 is continuously transferred 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 the continuous discharge to obtain the granular / powder MXD6 final product.

[0105] Example 12

[0106] This example utilizes the device as shown in Figure 1 to continuously prepare semi-aromatic copolymer high-temperature-resistant nylon PA6T / 6I / 6 at low temperature, and the steps are as follows:

[0107] 1) In a nitrogen atmosphere, hexamethylene diamine, terephthalic acid, isophthalic acid, caprolactam, water, and sodium hypophosphite are continuously conveyed through the silo or pipeline to the 80℃ salt formation kettle 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, and the residence time is 1 h, and the nylon salt solution at the outlet of the salt formation kettle is 50%;

[0108] 2) The nylon salt solution of step 1) is uniformly delivered by the dilute salt solution metering pump 2 at a rate of 1021.98 g / min to the salt solution buffer tank 3, and then uniformly delivered by the dilute salt solution buffer metering pump 4 at a rate of 910 g / min to the heat exchanger 5, at which time the dilute salt solution temperature at the outlet of the heat exchanger 5 is 180°C; the nylon salt solution is continuously delivered through the heat exchanger by the high-temperature dilute salt solution metering pump 6 at a rate of 910 g / min to the 180°C salt solution concentration tank, and the nylon salt solution at the outlet of the concentration tank is 75%; the nylon salt concentrated solution is then delivered by the high-temperature concentrated salt solution metering pump 8 at a rate of 682.5 g / min to the first-stage shell-and-tube reactor 9, the temperature in the reactor is 230°C, the pressure is 2.4 MPa, and the residence time is 1.5 h; the material continuously reacts in the shell from bottom to top, and is uniformly and continuously delivered at a rate of 650 g / min to the second-stage tubular reactor 12, and the gas discharged in this stage contains a small amount of diamine, which is separated by the rectification tower 10, and the small amount of diamine in the gas is returned to the bottom of the first-stage vertical shell-and-tube reactor 9, and the steam is condensed in the condensation tank 11 and returned to the salt formation kettle 1;

[0109] 3) The porous granular / powder material of step 2) enters the second-stage tubular reactor 12 in the positive pressure stage, and the material is pushed forward by the spiral propeller arranged in the second-stage tubular reactor 12 at a rate of 650 g / min to perform the reaction, 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, and 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-stage shell-and-tube reactor 9 and the second-stage tubular reactor 12 is utilized to realize the continuous transformation of the material from the homogeneous fluid state to the porous granular / powder state; the second-stage tubular reactor 12 is provided with a cyclone separator 13 at the exhaust port, and the powder material at the bottom of the cyclone separator 13 is returned to the second-stage tubular reactor 12 for recycling;

[0110] 4) The material is delivered from the second-stage tubular reactor to the third-stage tubular reactor 16, the porous granular / powder material of step 3) is continuously transferred through the first buffer tank 14 and the second buffer tank 15, enters the third-stage tubular reactor 16 in the negative pressure stage, and is further solid-phase polymerized to obtain the final product; the temperature in the third-stage tubular reactor 16 is 250°C, the absolute pressure is 300 Pa, and the residence time is 2 h; the material after the solid-phase polymerization of the third-stage tubular reactor 16 is delivered 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 the continuous delivery to obtain the granular / powder PA6T / 6I / 6 final product.

[0111] Example 13

[0112] This example utilizes the device shown in Figure 1 to continuously prepare the semi-aromatic copolymer high-temperature resistant nylon PA6T / 6I / 66 at low temperature, and the steps are as follows:

[0113] 1) Hexanediamine, terephthalic acid, isophthalic acid, adipic acid, water and antioxidant 1010 were continuously fed through a hopper or a pipe 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 into a 80℃ salt formation tank under a nitrogen atmosphere, with a residence time of 1 h, and the nylon salt solution at the outlet of the salt formation tank was 40%;

[0114] 2) The nylon salt solution of step 1) was uniformly fed through a dilute salt solution metering pump 2 at a rate of 818.05 g / min into a salt solution buffer tank 3, and then uniformly fed through a dilute salt solution buffer metering pump 4 at a rate of 710 g / min into a heat exchanger 5, at which time the temperature of the dilute salt solution at the outlet of the heat exchanger 5 was 180℃; the nylon salt solution was continuously fed through the heat exchanger into a 180℃ salt solution concentration tank through a high-temperature dilute salt solution metering pump 6 at a rate of 710 g / min, and the nylon salt solution at the outlet of the concentration tank was 70%; the nylon salt concentrate was immediately fed through a high-temperature concentrated salt solution metering pump 8 into a first-stage tubular reactor 9 at a rate of 532.5 g / min, the temperature in the reactor was 230℃, the pressure was 2.4 MPa, and the residence time was 1.0 h; the material was continuously reacted in the tubular reactor from bottom to top, while being uniformly and continuously fed into a second-stage tubular reactor 12 at a rate of 508 g / min, and the gas discharged in this stage contained a small amount of diamine, which was separated through a rectification column 10, and the small amount of diamine in the gas was returned to the bottom of the first-stage vertical tubular reactor 9, and the steam was condensed in a condensation tank 11 and returned to the salt formation tank 1;

[0115] 3) The porous granular / powder material of step 2) entered the positive pressure stage of the second-stage tubular reactor 12, and the material was pushed forward by a screw propeller arranged in the second-stage tubular reactor 12 at a rate of 508 g / min while being reacted, the reactor 12 used three-stage heating, the temperature of the first heating stage was 220℃, the temperature of the second heating stage was set to 230℃, and the temperature of the third heating stage was set to 250℃, the pressure was 0.5 MPa, and the residence time of the material in each heating stage was 0.3 h; the pressure difference between the first-stage tubular reactor 9 and the second-stage tubular reactor 12 was utilized to realize the continuous transformation of the material from a homogeneous fluid state to a porous granular / powder state; a cyclone separator 13 was arranged at the exhaust port of the second-stage tubular reactor 12, and the powder material at the bottom of the cyclone separator 13 was returned to the second-stage tubular reactor 12 for recycling;

[0116] 4) The material is transported from the secondary tubular reactor to the tertiary tubular reactor 16, the porous granular / powdered material is continuously switched through the first buffer tank 14 and the second buffer tank 15 into the negative pressure stage of the tertiary tubular reactor 16, and further solid-phase polymerization is carried out 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 material after the solid-phase polymerization in the tertiary tubular reactor 16 is continuously converted from the negative pressure stage to the normal pressure system through the rapid alternation of the third buffer tank 17 and the fourth buffer tank 18, and finally, the continuous discharge of the granular / powdered PA6T / 6I / 6 final product is realized.

[0117] Comparative Example 1

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

[0119] Comparative Example 2

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

[0121] Comparative Example 3

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

[0123] Performance Test Example 1

[0124] The products of the above examples and comparative examples are tested for performance, 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 application

[0126]

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

[0128] Table 2 Characterization results

[0129]

[0130]

[0131] As can be seen from the test results of Examples 1-5 in Table 2, regardless of whether 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 naphthalene-containing nylon, or bicomponent high-temperature resistant semi-aromatic nylon, the apparatus and method of the present invention can continuously prepare high-performance high-temperature resistant nylon products. This indicates that the apparatus and method of the present invention have a wide range of applications, and the obtained products have a low yellow index and good product quality.

[0132] Secondly, this invention discovered that the ratio of raw materials used has a certain impact on the performance of the product. To illustrate the effect of different molar ratios of diacid and diamine on product performance, this invention uses copolynylon PA6T / 66 as an example, and prepares copolynylon PA6T / 66 with different molar ratios of diacid and diamine. The test results are shown in Examples 5-8 in Table 2. The test results show that different molar ratios of diacid and diamine have a significant impact on the physical properties of copolynylon PA6T / 66, especially on its melting point. It also proves that as the terephthalic acid content decreases (Comparative Example 3), the melting point of the product gradually decreases.

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

[0134] Performance Test Example 2

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

[0136] Figure 2 Middle, 3308cm -1 It is the stretching vibration peak of NH, 2931 cm⁻¹ -1 and 2857cm -1 These are the antisymmetric stretching vibration peak and the symmetric stretching vibration peak of CH2, respectively, at 1634 cm⁻¹. -1 It is the stretching vibration peak of C=O (amide I band), 1538 cm⁻¹ -1 It is the in-plane bending vibration peak of NH (amide II band), 3081 cm⁻¹ -1 The peak is an overtone of the combination of NH and CN vibration peaks, at 863 cm⁻¹. -1 It is the in-plane bending vibration peak of CH on the benzene ring.Figure 3 Chemical shifts are shown for each H. Figure 4 PA6T / 66 (60 / 40) is shown, which has a melting point of 312°C. Figure 5 PA6T / 66 (60 / 40) is shown, which has an initial thermal decomposition temperature of 423°C and a fastest thermal decomposition temperature of 456°C.

[0137] The above examples are only used to illustrate the detailed devices and methods of the present application, but the present application is not limited to the above detailed devices and methods, i.e. it does not mean that the present application must rely on the above detailed devices and methods to be implemented. It should be understood by those skilled in the art that any improvement on the devices and methods of the present application, equivalent replacement of each raw material of the devices and products of the present application, addition of auxiliary ingredients, selection of specific modes, etc. all fall within the protection scope and disclosure scope of the present application.

Claims

1. A low-temperature continuous preparation apparatus for high-temperature resistant nylon, characterized in that, The system includes a salt-forming kettle (1), a heat exchanger (5), a brine concentration tank (7), a primary tubular reactor (9), a secondary tubular reactor (12), a tertiary tubular reactor (16), and a product collection tank (19), all connected by pipes in sequence. 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 side-by-side between the secondary tubular reactor (12) and the tertiary tubular reactor (16), and between the tertiary tubular reactor (16) and the product collection tank (19). The salt-forming kettle (1) and... Change A brine buffer tank (3) is installed between the heaters (5).

2. The low-temperature continuous preparation apparatus for high-temperature resistant nylon according to claim 1, characterized in that, The exhaust port of the two-stage tubular reactor (12) is equipped 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).

3. The low-temperature continuous preparation apparatus for high-temperature resistant nylon according to any one of claims 1-2, characterized in that, The low-temperature continuous preparation device for high-temperature resistant nylon also includes a distillation column (10) connected to the top exhaust port of the first-stage tubular reactor (9). The distillation column (10) includes a top exhaust port, a bottom discharge port and a side feed port located in the middle of the column. The top exhaust port of the distillation column (10) is connected to a salt vessel (1) through a pipe. The bottom discharge port of the distillation column (10) is connected to the feed port provided at the bottom of the first-stage tubular reactor (9).

4. The low-temperature continuous preparation apparatus for high-temperature resistant nylon according to claim 3, characterized in that, A condenser (11) is provided between the distillation column (10) and the salt-forming vessel (1), and between the brine concentration tank (7) and the salt-forming vessel (1).

5. The low-temperature continuous preparation apparatus for high-temperature resistant nylon according to claim 4, characterized in that, Metering pumps are installed between the salt-forming vessel (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 concentrate tank (7), and between the brine concentrate tank (7) and the primary tubular reactor (9).

6. A method for the low-temperature continuous preparation of high-temperature resistant nylon, characterized in that, It includes the neutralization and salt formation stage, the primary tubular reactor reaction stage, the secondary tubular reactor polymerization stage, and the tertiary tubular reactor polymerization stage; 1) Neutralization and salt formation stage: In an inert gas atmosphere, diamine, dicarboxylic acid, water, and additives are uniformly introduced into the salt formation vessel (1) at a rate of 100 g / min to 500 g / min, diacid, water, and additives at a rate of 100 g / min to 500 g / min, 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) First-stage tubular reactor stage: The nylon salt solution from step 1) is uniformly pumped to the brine buffer tank (3) at a rate of 530 g / min to 1100 g / min via a dilute brine metering pump (2), and then uniformly pumped to the heat exchanger (5) at a rate of 450 g / min to 1000 g / min via a dilute brine buffer metering pump (4). At this time, the dilute brine temperature at the outlet of the heat exchanger (5) is 140℃ to 180℃. After heat exchange, the high-temperature dilute brine is uniformly pumped to the brine concentration tank (7) at a rate of 390 g / min to 1000 g / min via a high-temperature dilute brine metering pump (6), and concentrated to 50% to 90% at 140℃ to 180℃. The concentrated brine is pumped at a rate of 370 g / min to 750 g / min. The material is uniformly delivered to the first-stage tubular reactor (9) at a rate of g / min through a high-temperature concentrated brine metering pump (8). The residence time is 0.2h to 1.5h at 190℃ to 230℃, and the pressure is 1.5MPa to 2.4MPa. The material reacts continuously from bottom to top in the first-stage tubular reactor (9) and is uniformly and continuously delivered to the second-stage tubular reactor (12) at a rate of 370 g / min to 750 g / min. 3) Polymerization stage in a two-stage tubular reactor: The porous granular / powdered material from step 2) enters the positive pressure stage of the two-stage tubular reactor (12). The material is propelled forward at a rate of 370 g / min to 750 g / min by a screw propeller installed inside the two-stage tubular reactor (12) while reacting. The polymerization reaction temperature in the two-stage tubular reactor (12) is 220℃ to 250℃, the reaction pressure is 0.2MPa to 1.0MPa, and the residence time is 0.6h to 1.5h. 4) Three-stage tubular reactor polymerization stage: In step 3), the porous granular / powdered material is continuously transferred through the first buffer tank (14) and the second buffer tank (15) and enters the negative pressure stage of the three-stage tubular reactor (16) for further solid-phase polymerization to obtain the final product; the solid-phase polymerization temperature is 220℃~250℃, the absolute pressure is 5Pa~500Pa, and the residence time is 0.5h~3h.

7. The low-temperature continuous preparation method of high-temperature resistant nylon according to claim 6, characterized in that, In step 1), the diamine is one or a mixture of two or more aliphatic diamines, aromatic diamines, alicyclic diamines, and diamines containing naphthyl rings; the dicarboxylic acid is one or a mixture of two or more aliphatic dicarboxylic acids, aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and dicarboxylic acids containing naphthyl rings; and the pH value of the nylon salt solution is 7.0 to 7.

5.

8. The low-temperature continuous preparation method of high-temperature resistant nylon according to claim 6, characterized in that, The diamine is one or a mixture of two or more of the following: butanediamine, pentanediamine, hexanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, and 1,5-diaminonaphthalene; the dicarboxylic acid is one or a mixture of two or more of the following: succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, tridecanoic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid.

9. The low-temperature continuous preparation method of high-temperature resistant nylon according to claim 6, characterized in that, In step 2), the primary tubular reactor (9) is equipped with a distillation column (10) and a condenser (11). The gas discharged from the top of the primary tubular reactor (9) is separated by the distillation column (10). A small amount of diamine in the gas phase is returned to the primary tubular reactor (9) to maintain the constant composition of the material in the primary tubular reactor (9). 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 equipped with a cyclone separator (13) at the exhaust port. The powdery 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 6, characterized in that, In step 3), the two-stage tubular reactor (12) is a positive pressure system and three heating sections are set along the material flow direction. The temperature of the first heating section is 200℃~220℃, the temperature of the second heating section is 210℃~230℃, and the temperature of the third heating section is 220℃~250℃. The residence time of the material in each heating section is 0.2h~0.5h. In step 4), the discharge of the solid-phase polymerized material from the three-stage tubular reactor (16) is rapidly and alternately transferred from the negative pressure stage to the normal pressure stage through the third buffer tank (17) and the fourth buffer tank (18), and finally collected in the product collection tank (19).

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