A high-temperature-resistant nylon low-temperature continuous method preparation system and a control method thereof

Abstract

The application belongs to the technical field of high-temperature-resistant nylon preparation, and discloses a low-temperature continuous preparation system for high-temperature-resistant nylon and a control method thereof. The system comprises a salting kettle, a dilute salt solution metering pump, a salt solution buffer tank, a dilute salt solution buffer metering pump, a heat exchanger, a salt solution concentration tank, a high-temperature concentrated salt solution metering pump, a first-stage tubular reactor, a second-stage tubular reactor, a third-stage tubular reactor and a product collection tank, which are connected by pipelines in sequence. At least two second-stage buffer tanks are arranged in parallel between the second-stage tubular reactor and the third-stage tubular reactor. At least two third-stage buffer tanks are arranged in parallel between the third-stage tubular reactor and the product collection tank. First, second, second-stage and third-stage control modules are arranged to control the respective production processes, so that the materials produced in each process have uniform quality, the control is more convenient, the low-temperature continuous production can be realized, the product quality is high, the production efficiency is high, the production cost is low, and energy is saved.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature resistant nylon preparation technology, and particularly relates to a low-temperature continuous preparation system for high-temperature resistant nylon and its control method. Background Technology

[0002] High-temperature nylon, due to its numerous advantages such as heat resistance, hydrolysis resistance, chemical corrosion resistance, good flowability, and good molding stability, has seen its application areas continuously expand, and its market capacity continues to grow. High-temperature nylon is a key material in the manufacturing of new energy vehicles and modern electronic and electrical appliances. It can replace metals in the manufacture of key automotive components, meeting the requirements for weight reduction and energy consumption reduction. It can also adapt to the SMT (Surface Mount Technology) process in modern electronic and electrical manufacturing, meeting the requirements for miniaturization, compactness, and low cost of electronic and electrical components. Therefore, it is a specialty engineering plastic urgently needed in both domestic and international markets.

[0003] Currently, the main continuous preparation methods for high-temperature resistant nylon are melt continuous polymerization and direct solid-phase continuous polymerization. Patents CN 114316255 B and CN 115873236 A first use nylon salt solution as raw material to prepare nylon prepolymer using melt continuous polymerization, and then continuously feed the prepolymer into a twin-screw extruder for reactive extrusion and granulation to obtain granular high-temperature resistant nylon. However, this method has very high requirements for the extruder, and the reaction temperature during polymerization is above the product's melting point. The high reaction temperature makes the product prone to oxidation, resulting in yellowing and blackening.

[0004] Zhengzhou University's patent CN 112979941 B describes a continuous direct solid-state polymerization method using powdered nylon salt as raw material to prepare powdered nylon products, such as PA12T, PA6T / 66, and PA12T / 6T. This method produces nylon with low polymerization temperatures, fewer side reactions, and high product quality, solving the problem of oxidation and yellowing / blackening that occurs in traditional high-temperature resistant nylon preparation. Furthermore, the design of production equipment and systematic control of the process enable continuous production, shortening polymerization time and reducing production costs. However, this method separates the preparation of powdered nylon salt and the polymerization process of nylon salt into two steps, and has not yet achieved continuous production from diamines and diacids to high-temperature nylon.

[0005] Based on patent CN 112979941 B, patent CN 114699989 A focuses on describing the application of timing control devices in the production of polyamides through continuous solid-phase polycondensation reactions, and details the equipment and specific operating procedures for continuous solid-phase polymerization reactions.

[0006] However, at this ejection pressure, the prepolymer has a low degree of reaction and contains a certain amount of unreacted nylon salt. During primary negative pressure polymerization, the nylon salt and the low-reaction components are easily vaporized at this temperature, resulting in a difference between the composition of the final product and the feed ratio.

[0007] Whether it is batch polymerization, direct solid-state polymerization, or the current continuous polymerization method, each has its 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

[0008] The present invention aims to provide a low-temperature continuous preparation system and control method for high-temperature resistant nylon with good preparation effect.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a low-temperature continuous preparation system for high-temperature resistant nylon, comprising a salt-forming kettle, a dilute salt solution metering pump, a salt solution buffer tank, a dilute salt solution buffer metering pump, a heat exchanger, a high-temperature dilute salt solution metering pump, a salt solution concentration tank, a high-temperature concentrated salt solution metering pump, a first-stage tubular reactor, a second-stage tubular reactor, a third-stage tubular reactor, and a product collection tank connected in sequence by pipes;

[0010] At least two secondary buffer tanks are arranged side-by-side between the two-stage tubular reactor and the three-stage tubular reactor;

[0011] At least two tertiary buffer tanks are installed side by side between the tertiary tubular reactor and the product collection tank;

[0012] The salt-forming kettle, the first-stage tubular reactor, the second-stage buffer tank, and the third-stage buffer tank are all connected to vacuum pumps via vacuum tubes;

[0013] The brine concentration tank is connected to a first control module. The first control module collects the concentration signal and pH signal from the brine concentration tank, and outputs a signal to control whether the brine concentration tank is connected to the first-stage tubular reactor based on the collected concentration signal and pH signal.

[0014] A second control module is connected to the first-stage tubular reactor. The second control module collects the pressure signal of the first-stage tubular reactor and outputs a signal to control whether the first-stage tubular reactor and the second-stage tubular reactor are connected based on the pressure signal.

[0015] The secondary and tertiary buffer tanks are respectively connected to a secondary control module and a tertiary control module. The secondary / tertiary control module collects the pressure signals inside the secondary / tertiary buffer tanks and outputs signals based on the pressure signals to control whether the secondary tubular reactor and the tertiary tubular reactor / the tertiary tubular reactor and the product collection tank are connected.

[0016] In a preferred embodiment of the present invention, the first control module includes a first controller, a concentration transmitter, a pH transmitter, and a first regulating valve. The signal output terminals of the concentration transmitter and the pH transmitter are both connected to the signal input terminal of the first controller. The first controller outputs a signal to control the operation of the first regulating valve and the high-temperature dilute brine metering pump. The first regulating valve is connected between the brine concentration tank and the first-stage tubular reactor.

[0017] As a preferred embodiment of the present invention, the second control module includes a second controller, a back pressure valve, and a second regulating valve;

[0018] The second controller outputs a signal to control the operation of the back pressure valve, the second regulating valve, and the high-temperature concentrated brine metering pump.

[0019] The back pressure valve is connected between the primary tubular reactor and the secondary tubular reactor;

[0020] The second regulating valve is connected between the primary tubular reactor and the distillation column.

[0021] As a preferred embodiment of the present invention, the secondary control module includes a secondary controller, a secondary pressure transmitter, a secondary first regulating valve, a secondary second regulating valve, and a secondary third regulating valve;

[0022] The signal output terminal of the secondary pressure transmitter is connected to the secondary controller, and the secondary controller outputs signals to control the secondary first regulating valve, the secondary second regulating valve, and the secondary third regulating valve.

[0023] The first regulating valve of the second stage is connected between the second-stage tubular reactor and the second-stage buffer tank; the second regulating valve of the second stage is connected to the vacuum tube connected to the second-stage buffer tank.

[0024] The secondary third regulating valve is connected between the secondary buffer tank and the tertiary tubular reactor.

[0025] As a preferred embodiment of the present invention, the three-level control module includes a three-level controller, a three-level pressure transmitter, a three-level first regulating valve, a three-level second regulating valve, and a three-level third regulating valve;

[0026] The signal output terminal of the three-stage pressure transmitter is connected to the three-stage controller, and the three-stage controller outputs signals to control the three-stage first regulating valve, the three-stage second regulating valve and the three-stage third regulating valve.

[0027] The first regulating valve of the third stage is connected between the third-stage tubular reactor and the third-stage buffer tank; the second regulating valve of the third stage is connected between the third-stage buffer tank and the product collection tank.

[0028] The third regulating valve of the third stage is connected to the vacuum tube that is connected to the third-stage buffer tank;

[0029] In a preferred embodiment of the present invention, the exhaust port of the two-stage tubular reactor is provided with a cyclone separator, and the material outlet at the bottom of the cyclone separator is connected to the two-stage tubular reactor.

[0030] As a preferred embodiment of the present invention, it further includes a distillation column connected to the top vent of the first-stage tubular reactor. The distillation column includes a top vent, a bottom outlet, and a side inlet located in the middle of the column. The top vent of the distillation column is connected to a salt vessel via a pipe, and the bottom outlet of the distillation column is connected to the inlet located at the bottom of the first-stage tubular reactor.

[0031] As a preferred embodiment of the present invention, a condenser is provided between the distillation column and the salt-forming vessel, and between the brine concentration tank and the salt-forming vessel.

[0032] This invention further discloses a method for controlling the low-temperature continuous preparation of high-temperature resistant nylon using the above-mentioned system, comprising the following steps:

[0033] 1) In a nitrogen atmosphere, the raw materials are transported to the salt-forming kettle at a certain rate and remain there for a set time; the nylon salt solution is continuously fed into the salt concentration tank through a heat exchanger.

[0034] 2) Collect the concentration and pH signals in the brine concentration tank. When they are within the set range, the material in the brine concentration tank enters the first-stage tubular reactor; otherwise, adjust the flow rate of the high-temperature dilute brine metering pump until the concentration and pH of the material in the brine concentration tank reach the set range.

[0035] 3) The high-temperature brine solution reacts from bottom to top through a single-stage tubular reactor. This process involves the following three steps:

[0036] Step 1: After the second regulating valve and the back pressure valve are closed simultaneously for a set time, and the pressure inside the first-stage tubular reactor reaches the first set parameter of 1.8 MPa to 2.4 MPa, proceed to Step 2.

[0037] Step 2: Set the opening time of the second regulating valve and the closing time of the back pressure valve. After the pressure inside the first-stage tubular reactor reaches the second set parameter of 1.5 MPa to 1.8 MPa, start the third step.

[0038] Step 3: The second regulating valve is closed for a set time, the back pressure valve is opened for a set time, and the material is transported to the secondary tubular reactor by pressure; when the pressure in the primary tubular reactor is lower than the third set parameter of 1.5MPa, step 1 is repeated, and the material is continuously transported to the secondary tubular reactor in a dynamic cycle.

[0039] 4) The material stays in the two-stage tubular reactor for a set time, and the material is alternately transported from the two-stage tubular reactor to the three-stage tubular reactor through two secondary buffer tanks;

[0040] 5) The residence time of the material in the three-stage tubular reactor is set, and the material enters the product collection tank alternately through two three-stage buffer tanks from the three-stage tubular reactor.

[0041] As a preferred embodiment of the present invention, the method for conveying material from the secondary tubular reactor to the tertiary tubular reactor is as follows:

[0042] This step includes the material entering the secondary tubular reactor from the secondary tubular reactor into the secondary buffer tank and from the secondary buffer tank into the tertiary tubular reactor; wherein there are two secondary buffer tanks, namely the first secondary buffer tank and the second secondary buffer tank;

[0043] The method for material to enter the secondary buffer tank from the secondary tubular reactor is as follows: after the material has been in the secondary tubular reactor for a set time, it enters the second secondary buffer tank, while at the same time, the first secondary buffer tank is subjected to negative pressure treatment;

[0044] After the material enters the second and second stage buffer tanks, discharge begins; at the same time, the material exiting the two-stage tubular reactor begins to enter the first and second stage buffer tanks.

[0045] The material discharge method in the second and second stage buffer tanks is as follows: the discharge port of the second and second stage buffer tanks is opened, and at this time, the first and second stage buffer tanks are being fed; the material in the second and second stage buffer tanks is discharged into the tertiary tubular reactor; after the discharge of the second and second stage buffer tanks is completed, negative pressure treatment is carried out, and at the same time, the material in the first and second stage buffer tanks is discharged.

[0046] This process is repeated cyclically to achieve alternating feeding and discharging;

[0047] After a set time in the three-stage tubular reactor, the material enters the product collection tank. This step includes the material entering the three-stage buffer tank from the three-stage tubular reactor and entering the product collection tank from the three-stage buffer tank. There are two three-stage buffer tanks, namely the first three-stage buffer tank and the second three-stage buffer tank.

[0048] The method for material to enter the third-stage buffer tank from the third-stage tubular reactor is as follows: after the material enters the second and third-stage buffer tanks after a set time in the third-stage tubular reactor, the first and third-stage buffer tanks are subjected to negative pressure treatment at the same time.

[0049] After the material enters the second and third stage buffer tanks, discharge begins. At the same time, the material coming out of the tertiary tubular reactor enters the first and third stage buffer tanks.

[0050] The material discharge method in the second and third stage buffer tanks is as follows: the discharge port of the second and third stage buffer tanks is opened, and at this time, the first and third stage buffer tanks are being fed; the material in the second and third stage buffer tanks is discharged to the product collection tank; after the second and third stage buffer tanks have finished discharging, negative pressure treatment is carried out, and at the same time, the material in the first and third stage buffer tanks is discharged.

[0051] This process is repeated in a cycle to achieve alternating feeding and discharging.

[0052] Through the above technical solutions, the technical effects of the present invention are as follows: The beneficial effects of the present invention are: (1) The preparation system described in the present invention can realize the low-temperature continuous production of high-temperature resistant nylon, with high product quality and high production efficiency; (2) The first control module, the second control module, the second-level control module and the third-level control module set up realize the control of their respective production processes, so that the materials produced in each process have the same quality, making control more convenient, and realizing the continuous input and output of dicarboxylic acid and diamine; (3) The use of a single-stage tubular reactor can greatly increase the heat generation efficiency and improve the reaction rate; (4) The second-stage tubular reactor and the third-stage tubular reactor adopt a positive spiral propulsion design structure, which not only promotes the material conveying, but also plays the role of crushing the material and promoting the reaction; (5) The control method described in the present invention can realize the control of the high-temperature resistant nylon production process. By adjusting the control parameters, the optimal high-temperature resistant nylon can be produced, the reaction is rapid, and continuous production can be realized; (6) The optimal working parameters were found through experiments, which helps to obtain the best-performing high-temperature resistant nylon. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the system described in this invention;

[0054] Figure 2 This is a schematic diagram showing the connection from the two-stage tubular reactor to the product collection tank;

[0055] 1-Salt-forming kettle; 2-Dilute brine metering pump; 3-Brine buffer tank; 4-Dilute brine buffer metering pump; 5-Heat exchanger; 6-High-temperature dilute brine metering pump; 7-Brine concentration tank; 8-High-temperature concentrated brine metering pump; 9-First-stage tubular reactor; 10-Distillation column; 11-Condenser; 12-Second-stage tubular reactor; 13-Cyclone separator; 14-First and second-stage buffer tanks; 15-Second and second-stage buffer tanks; 16-Tertiary tubular reactor; 17-First and third-stage buffer tanks; 18-Second and third-stage buffer tanks; 19-Product collection tank; 20-Vacuum tank; 21-Vacuum pump; C101-Concentration transmitter; PH101-Acidity / alkalinity transmitter; 101-First regulating valve; 201-Second regulating valve; 202-Back pressure valve;

[0056] 301 - Secondary first regulating valve, 302 - Secondary second regulating valve, 303 - Secondary third regulating valve;

[0057] 501 - Third-stage first regulating valve; 502 - Third-stage second regulating valve; 503 - Third-stage third regulating valve;

[0058] K1 - First control module, K2 - Second control module, K3 - Secondary control module, K5 - Tertiary control module;

[0059] P301 - First pressure transmitter, P501 - Second pressure transmitter. Detailed Implementation

[0060] The following will combine Figure 1 and Figure 2 This invention has been clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of this invention.

[0061] It should be noted that:

[0062] The system and control method of this invention are applicable to the preparation of various high-temperature resistant nylons, including homopolymers and copolymers, such as semi-aromatic nylons, alicyclic nylons, and naphthalene-containing nylons, etc., and have a wide range of applications. The formulation and preparation of nylon salts are relatively mature, and existing technologies can be used to prepare nylon salts.

[0063] For example, when applying this invention, the selection of raw materials can be determined based on the high-temperature resistant nylon being prepared, including the dicarboxylic acid, diamine, and additives, and their amounts. The diamine can be one or a mixture of two or more aliphatic diamines, aromatic diamines, alicyclic diamines, and naphthyl ring diamines, preferably butanediamine, pentanediamine, hexanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diamino-dicyclohexylmethane, and 3,3'-dimethyl-4, The nylon salt solution comprises one or more of 4'-diamino-dicyclohexylmethane and 1,5-diaminonaphthalene; the dicarboxylic acid is one or more of aliphatic dicarboxylic acids, aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and naphthylcyclic dicarboxylic acids, preferably one or more of 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; the pH value of the nylon salt solution is 7.0 to 7.5.

[0064] Secondly, those skilled in the art, guided by the principles of this system, select auxiliary agents, such as catalysts and antioxidants. The catalyst can be selected from one or more of phosphorous acid, sodium hypophosphite, triphenyl phosphate, and H10. In this invention, the inventors suggest that the amount of catalyst is preferably 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. The amount of antioxidant is preferably 0.1% to 0.6% of the dry mass of the diacid and diamine.

[0065] It should also be noted that the set values ​​and "certain rate" in the "concentration and pH of the brine concentration tank 7 meet the set values" mentioned in the various embodiments or application examples of the present invention may vary slightly in specific high-temperature resistant nylon reaction systems. However, this is expected by those skilled in the art and can be clearly determined based on a limited number of experiments. The set values ​​for the concentration of the brine concentration tank 7 of the present invention are preferably 50% to 90% and the pH is preferably 7.0 to 7.5. The above parameter settings do not affect the working process of the entire system, therefore the present invention does not impose specific limitations.

[0066] To better illustrate the effects of the present invention, the present invention combines... Figure 1 and Figure 2 The present invention will be further described in conjunction with specific embodiments.

[0067] Example 1:

[0068] The high-temperature resistant nylon low-temperature continuous preparation system of this embodiment, such as... Figure 1 and Figure 2 As shown, the system includes a salt-forming reactor 1, a brine buffer tank 3, a heat exchanger 5, a high-temperature dilute brine metering pump 6, 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.

[0069] At least two secondary buffer tanks are arranged side by side between the secondary tubular reactor 12 and the tertiary tubular reactor 16. In this embodiment, there are two secondary buffer tanks, namely the first secondary buffer tank 14 and the second secondary buffer tank 15. At least two tertiary buffer tanks are arranged side by side between the tertiary tubular reactor 16 and the product collection tank 19, namely the first tertiary buffer tank 17 and the second tertiary buffer tank 18.

[0070] 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.

[0071] The system also includes a distillation column 10 connected to the top vent of the primary tubular reactor 9. The distillation column 10 includes a top vent, a bottom outlet, and a side inlet located in the middle of the column. The top vent of the distillation column 10 is connected to the salt-forming vessel 1, and the bottom outlet of the distillation column 10 is connected to the inlet at the bottom of the primary tubular reactor 9. A condenser 11 is installed between the distillation column 10 and the salt-forming vessel 1, and between the brine concentrate tank 7 and the salt-forming vessel 1. 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.

[0072] metering pumps, such as Figure 1 The pumps shown are, respectively, a dilute brine metering pump 2, a buffer solution metering pump 4, a high-temperature dilute brine metering pump 6, and a high-temperature concentrated brine metering pump 8. Their purpose is to control the material flow rate, thereby controlling the material's residence time in the device. The salt-forming kettle 1, the brine buffer tank 3, and the brine concentration tank 7 are all equipped with stirring devices. These stirring devices are standard features in this field and will not be described in detail here.

[0073] Vacuum pump 21 is connected to the salt-forming kettle 1, the primary tubular reactor 9, the secondary buffer tank, and the tertiary buffer tank via vacuum tubes, thereby creating a positive pressure system in the primary tubular reactor 9, for example, a pressure of 1.5MPa to 2.4MPa; a positive pressure system in the secondary tubular reactor 12, for example, a pressure of 0.2MPa to 1.0MPa; and a negative pressure system in the tertiary tubular reactor 16, for example, a pressure of 5Pa to 500Pa; thus ensuring the continuity of the system materials and the stability of the pressure.

[0074] To facilitate the reaction, ensure the consistency of material quality produced in each process, facilitate control, and improve the effectiveness, a first control module is connected to the brine concentration tank 7. This first control module collects concentration and pH signals from the brine concentration tank 7 and outputs signals to control whether the brine concentration tank 7 is connected to the primary tubular reactor 9 based on the collected signals. The first control module includes a first controller K1, a concentration transmitter C101, a pH transmitter PH101, a first regulating valve 101, and a high-temperature dilute brine metering pump 6.

[0075] The signal output terminals of the concentration transmitter C101 and the pH transmitter PH101 are both connected to the signal input terminal of the first controller K1. The first output signal of the controller controls the operation of the first regulating valve 101 and the high-temperature dilute brine metering pump 6. The first regulating valve 101 is connected between the brine concentration tank 7 and the first-stage tubular reactor 9.

[0076] Concentration transmitter C101 and pH transmitter PH101 collect concentration and pH information respectively and transmit the collected information to the first controller K1. According to the received signal, if the concentration and pH meet the set value, the first controller K1 opens the first regulating valve 101, so that the material in the brine concentration tank 7 enters the first-stage tubular reactor 9 through the high-temperature concentrated brine metering pump.

[0077] If the concentration and pH are higher than the set values, the first controller K1 outputs a signal to close the first regulating valve 101, adjusting the flow rate of the high-temperature dilute brine metering pump 6 to reduce the concentration and pH until the set values ​​are reached. Then, the first controller K1 outputs a signal to open the first regulating valve 101, allowing the material in the brine concentration tank 7 with the set concentration and pH to enter the primary tubular reactor 9 via the high-temperature concentrated brine metering pump 8. In this embodiment, although concentration and pH are two values, the pH of the material is generally also determined when the concentration is constant. By collecting both the concentration and pH values ​​of the system, accuracy can be improved.

[0078] A second control module is connected to the first-stage tubular reactor 9. The second control module collects the pressure signal of the first-stage tubular reactor 9 and outputs a signal to control whether the first-stage tubular reactor 9 and the second-stage tubular reactor 12 are connected.

[0079] The second control module includes a second controller K2, a first pressure transmitter, a back pressure valve 202, a second regulating valve 201, and a high-temperature concentrated brine metering pump 8.

[0080] The first pressure transmitter collects the pressure signal from the first-stage tubular reactor 9 and transmits the collected pressure signal to the second controller K2.

[0081] The second controller K2 outputs a signal to control the operation of the back pressure valve 202, the second regulating valve 201, and the high-temperature concentrated brine metering pump 8 based on the received pressure signal.

[0082] A high-temperature concentrated brine metering pump 8 is connected between the brine concentration tank 7 and the primary tubular reactor 9;

[0083] Back pressure valve 202 is connected between primary tubular reactor 9 and secondary tubular reactor 12;

[0084] The second regulating valve 201 is connected between the primary tubular reactor 9 and the distillation column 10.

[0085] Only when the pressure inside the primary tubular reactor 9 reaches the set value is the primary tubular reactor 9 and the secondary tubular reactor 12 connected. The material in the primary tubular reactor 9 enters the secondary tubular reactor 12 via the high-temperature concentrated brine metering pump 8. In this embodiment, the high-temperature brine reacts from bottom to top through the primary tubular reactor 9, increasing the system pressure. Within a set time, the second regulating valve 201 opens and the back pressure valve 202 closes. When the system pressure reaches the set pressure of the back pressure valve 202, the back pressure valve 202 opens, the second regulating valve 201 closes, and the high-temperature concentrated brine metering pump 8 starts, allowing the material to quickly enter the secondary tubular reactor 12. This alternating opening and closing ensures continuous material transport.

[0086] Each secondary buffer tank and each tertiary buffer tank are respectively connected to a secondary control module and a tertiary control module. The secondary / tertiary control module collects the pressure signal inside the secondary / tertiary buffer tank and outputs a signal based on the pressure signal to control whether the secondary tubular reactor 12 and the tertiary tubular reactor 16 are connected to the product collection tank 19.

[0087] The secondary control module includes a secondary controller K3, a secondary pressure transmitter P301, a secondary first regulating valve 301, a secondary second regulating valve 302, and a secondary third regulating valve 303;

[0088] The secondary pressure transmitter P301 is connected to the secondary buffer tank. The signal output terminal of the secondary pressure transmitter P301 is connected to the secondary controller K3. The secondary controller K3 outputs signals to control the opening and closing of the secondary first regulating valve 301, the secondary second regulating valve 302 and the secondary third regulating valve 303.

[0089] The second-stage first regulating valve 301 is connected between the second-stage tubular reactor 12 and the second-stage buffer tank; the second-stage second regulating valve 302 is connected to the vacuum tube connected to the second-stage buffer tank;

[0090] The secondary third regulating valve 303 is connected between the secondary buffer tank and the tertiary tubular reactor 16. After the secondary third regulating valve 303 is opened, the material enters the tertiary tubular reactor 16 from the secondary buffer tank to react.

[0091] The three-level control module includes a three-level controller K5, a three-level pressure transmitter P501, a three-level first regulating valve 501, a three-level second regulating valve 502, and a three-level third regulating valve 503.

[0092] The three-stage pressure transmitter P501 is connected to the three-stage buffer tank. The signal output terminal of the three-stage pressure transmitter P501 is connected to the three-stage controller K5. The three-stage controller K5 outputs signals to control the three-stage first regulating valve 501, the three-stage second regulating valve 502, and the three-stage third regulating valve 503.

[0093] The third-stage first regulating valve 501 is connected between the third-stage tubular reactor 16 and the third-stage buffer tank; the third-stage second regulating valve 502 is connected between the third-stage buffer tank and the product collection tank 19. When the third-stage third regulating valve is opened, the material enters the product collection tank 19 from the third-stage buffer tank.

[0094] The third-stage regulating valve 503 is connected to the vacuum tube that is connected to the third-stage buffer tank;

[0095] In this embodiment, the first controller K1, the second controller K2, the second-level controller K3, and the third-level controller K5 can all be microcontrollers. When implementing them, a microcontroller of model STM32F103C8T6 can be selected.

[0096] The first regulating valve 101, the second regulating valve 201, the back pressure valve 202, the second-stage first regulating valve 301, the second-stage second regulating valve 302, the second-stage third regulating valve 303, the third-stage first regulating valve 501, the third-stage second regulating valve 502, and the third-stage third regulating valve 503 can be pneumatic or electric regulating valves; the back pressure valve 202 is an electric back pressure valve 202.

[0097] Controlling the opening, closing, and adjustment of the opening degree of the electric regulating valve or electric back pressure valve 202 by the output signal of the microcontroller is a mature existing technology, and its implementation method will not be described in detail in this embodiment.

[0098] The concentration transmitter C101, pH transmitter PH101, and pressure transmitter are all commercially available products. They transmit the collected concentration, pH, and pressure information to the microcontroller. The microcontroller compares the received signal with the threshold. This is a mature existing technology, and its implementation will not be described in detail in this embodiment.

[0099] Controlling the metering pump with a microcontroller output signal is a mature existing technology, and this embodiment does not involve any improvement to this part, so it will not be described in detail.

[0100] The system described in this invention discloses a low-temperature continuous production system for high-temperature resistant nylon, which can realize low-temperature continuous production, resulting in high product quality, high production efficiency, low production cost, and energy saving.

[0101] This embodiment also discloses a method for controlling the low-temperature continuous preparation of high-temperature resistant nylon in the above system, the method comprising the following steps in sequence:

[0102] 1) In a nitrogen atmosphere, the raw materials are transported to the salt-forming kettle at a certain rate and remain for a set time; the nylon salt solution continuously enters the salt concentration tank 7 through the heat exchanger 5;

[0103] 2) Collect the concentration and pH signals in the brine concentration tank 5. If the concentration and pH meet the set values, the first regulating valve 101 is opened, so that the material in the brine concentration tank 7 enters the first-stage tubular reactor 9 through the high-temperature concentrated brine metering pump 8.

[0104] If the concentration and pH are higher than the set values, the first controller K1 outputs a signal to close the first regulating valve 101, adjusting the flow rate of the high-temperature dilute brine metering pump 6 to reduce the concentration and pH until the set values ​​are reached. Then, the first controller K1 outputs a signal to open the first regulating valve 101, allowing the material in the brine concentration tank 7 with the set concentration and pH to enter the primary tubular reactor 9 via the high-temperature concentrated brine metering pump 8. In this embodiment, although concentration and pH are two values, the pH of the material is generally also determined when the concentration is constant. In this embodiment, collecting both the concentration and pH values ​​of the system improves accuracy.

[0105] 3) The high-temperature brine solution reacts from bottom to top through the primary tubular reactor 9. The control of this process includes three steps:

[0106] Step 1: After the second regulating valve 201 and the back pressure valve 202 are closed simultaneously for a set time, and the pressure inside the first-stage tubular reactor 9 reaches the set parameter of 1.8 MPa to 2.4 MPa, proceed to step 2.

[0107] Step 2: The second regulating valve 201 is opened for a set time, the back pressure valve 202 is closed for a set time, and after the pressure inside the first-stage tubular reactor 9 reaches the set parameter of 1.5 MPa to 1.8 MPa, the third step is started.

[0108] Step 3: The second regulating valve 201 is closed for a set time, and the back pressure valve 202 is opened for a set time. The material is transported to the secondary tubular reactor 12 by pressure. When the pressure inside the primary tubular reactor 9 is lower than the third set parameter of 1.5MPa, step 1 is repeated, and the material is continuously transported to the secondary tubular reactor 12 in a dynamic cycle.

[0109] In the first-stage tubular reactor 9, the material was continuously transformed from a homogeneous fluid state to a porous particle / powder state.

[0110] 4) The material stays in the two-stage tubular reactor 12 for a set time, and the material is alternately transported from the two-stage tubular reactor 12 to the three-stage tubular reactor 16 through two secondary buffer tanks.

[0111] The method for conveying material from the secondary tubular reactor 12 to the tertiary tubular reactor 16 is as follows:

[0112] This step includes the material entering the secondary tubular reactor 12 into the secondary buffer tank and from the secondary buffer tank into the tertiary tubular reactor 16; wherein, the method for the material to enter the secondary buffer tank from the secondary tubular reactor 12 is as follows: the two secondary buffer tanks are the first secondary buffer tank 14 and the second secondary buffer tank, respectively;

[0113] After a set time in the two-stage tubular reactor 12, the material enters the second secondary buffer tank, while at the same time, the first secondary buffer tank 14 is subjected to negative pressure treatment.

[0114] After the material enters the second and secondary buffer tanks, discharge begins; at the same time, the material coming out of the secondary tubular reactor 12 begins to enter the first and secondary buffer tank 14.

[0115] The material discharge method in the second and second buffer tanks is as follows: the discharge port of the second and second buffer tanks is opened, and at this time, the first and second buffer tanks 14 are being fed; the material in the second and second buffer tanks is discharged into the tertiary tubular reactor 16. After the second and second buffer tanks are discharged, negative pressure treatment is carried out. At the same time, the material in the first and second buffer tanks 14 is discharged. This cycle is repeated to achieve alternating feeding and discharging.

[0116] 5) The material is in the three-stage tubular reactor 16, and after a set residence time, it enters the product collection tank 19 alternately through two three-stage buffer tanks.

[0117] After a set time in the three-stage tubular reactor 16, the material enters the product collection tank 19. This step includes the material entering the three-stage buffer tank from the three-stage tubular reactor 16 and entering the product collection tank 19 from the three-stage buffer tank. The material enters the three-stage buffer tank from the three-stage tubular reactor 16. The two three-stage buffer tanks are the first three-stage buffer tank 17 and the second three-stage buffer tank 18, respectively.

[0118] After a set time in the three-stage tubular reactor 16, the material enters the three-stage buffer tank. At the same time, the first three-stage buffer tank 17 is subjected to negative pressure treatment.

[0119] After the material enters the second and third stage buffer tanks 18, the material discharge begins. At the same time, the material coming out of the third stage tubular reactor 16 enters the first and third stage buffer tank 17.

[0120] The material discharge method in the second and third-stage buffer tanks 18 is as follows: the discharge port of the second and third-stage buffer tanks 18 is opened, and at this time, the first and third-stage buffer tanks 17 are feeding. The material in the second and third-stage buffer tanks 18 is discharged to the product collection tank 19. After the second and third-stage buffer tanks 18 finish discharging, negative pressure treatment is carried out. At the same time, the material in the first and third-stage buffer tanks 17 is discharged. This cycle is repeated to achieve alternating feeding and discharging.

[0121] Application Example 1

[0122] This embodiment takes the preparation of PA6T / 6 as an example to illustrate how to utilize the above system to achieve a low-temperature continuous process for preparing PA6T / 66 from high-temperature resistant nylon. The process includes the following steps: Under a nitrogen atmosphere, hexamethylenediamine, terephthalic acid, caprolactam (the molar ratio of terephthalic acid to caprolactam is 60:40), water, and additives are fed into a 60°C salt-forming reactor at rates of 208.8 g / min, 298.8 g / min, 135.6 g / min, 257.8 g / min, and 1 g / min, respectively, with a residence time of 1 h. In this embodiment, the additive is sodium hypophosphite. The nylon salt solution at the outlet of the salt-forming reactor is 40%.

[0123] The nylon salt solution from step 1) is uniformly pumped to the brine buffer tank 3 at a certain rate (901.48 g / min in this embodiment) by the dilute brine metering pump 2, and then uniformly pumped to the heat exchanger 5 at a certain rate (800 g / min in this embodiment) by the dilute brine buffer metering pump 4. At this time, the dilute brine temperature at the outlet of the heat exchanger 5 is 180℃. The nylon salt solution continuously enters the 180℃ brine concentration tank after passing through the heat exchanger. After the signal output of the concentration transmitter C101 and the pH transmitter PH101 reaches the set parameter value of the first controller K1 of the concentration tank, in this embodiment, the mass concentration is selected as 75% and the pH value is 7.2. The first regulating valve 101 is opened, and the material enters the first-stage tubular reactor 9. The reactor is controlled by the first control unit K2. Step 1: The second regulating valve 201 and the back pressure valve 202 are simultaneously closed for 15 seconds. After the pressure inside the primary tubular reactor 9 reaches the first set parameter of 2.1 MPa, the second step begins. Step 2: The second regulating valve 201 is opened for 7 seconds, and the back pressure valve 202 is closed for 7 seconds. After the pressure inside the primary tubular reactor 9 reaches the second set parameter of 1.6 MPa, the third step is initiated. Step 3: The second regulating valve 201 is closed for 5 seconds, and the back pressure valve 202 is opened for 5 seconds. The material is transported to the secondary tubular reactor 12 by pressure. When the pressure inside the primary tubular reactor 9 is lower than the third set parameter of 1.5 MPa, step 1 is repeated, and this dynamic cycle continuously transports the material to the secondary tubular reactor 12. The main purpose of setting the pressure parameters in this embodiment is to create a pressure difference between the primary and secondary tubular reactors, allowing for smooth and continuous material transport under the influence of this pressure difference.

[0124] The material residence time in the secondary tubular reactor 12 is 0.9 hours, controlled by two secondary control modules of the secondary tubular reactor 12. The material is then transported from the secondary tubular reactor 12 to the tertiary tubular reactor 16. During this process:

[0125] The second-stage regulating valve 302, connected to the first-stage buffer tank 14, closes for 3 seconds, and the third-stage regulating valve 303 opens for 3 seconds. At this time, the first-stage buffer tank 14 is evacuated again. Subsequently, the first-stage regulating valve 401, connected to the second-stage buffer tank 15, opens for 3 seconds, and the material in the second-stage tubular reactor 12 is transported to the second-stage buffer tank 15. Then, the first-stage regulating valve 401, connected to the second-stage buffer tank 15, closes for 3 seconds, and the second-stage regulating valve 402, connected to the second-stage buffer tank 14, opens for 3 seconds, and the material in the second-stage buffer tank 15 enters the tertiary tubular reactor 16.

[0126] The process is repeated in sequence, that is, when the first secondary buffer tank 14 is being fed, the second secondary buffer tank 15 is being evacuated; after the first secondary buffer tank 14 is finished being fed, it is being discharged, at which time the second secondary buffer tank 15 is being fed; this process is repeated in sequence, so that the first secondary buffer tank 14 and the second secondary buffer tank 15 are alternately fed and discharged.

[0127] The material resides in the three-stage tubular reactor 16 for 3.0 hours. Through two three-stage control modules, the second-stage regulating valve 502, connected to the first-stage buffer tank 17, closes for 3 seconds, and the third-stage regulating valve 503 opens for 3 seconds. At this time, the first-stage buffer tank 17 is then evacuated. Subsequently, the first-stage regulating valve 601, connected to the second-stage buffer tank 18, opens for 3 seconds, and the material in the three-stage tubular reactor 16 is discharged into the second-stage buffer tank 18.

[0128] Subsequently, the second- and third-stage regulating valve 602, connected to the second- and third-stage buffer tank 18, is opened for 3 seconds, and then the first- and third-stage regulating valve 601 is closed for 3 seconds. The material in the second- and third-stage buffer tank 18 enters the product collection tank 19, and the cycle repeats. That is, when the first- and third-stage buffer tank 17 is feeding material, the second- and third-stage buffer tank 18 is evacuating. After the first- and third-stage buffer tank 17 finishes feeding material, it discharges material, and at this time, the second- and third-stage buffer tank 18 is feeding material. This cycle repeats, realizing the alternating feeding and discharging of the first- and third-stage buffer tank 17 and the second- and third-stage buffer tank 18.

[0129] Finally, continuous discharge yields the final product, PA6T / 6 in granular / powder form.

[0130] Application Example 2

[0131] This application example uses the preparation of PA6T / 12T as an example to illustrate how to utilize the above system to achieve a low-temperature continuous process for preparing PA6T / 12T from high-temperature resistant nylon. The process includes the following steps: Under a nitrogen atmosphere, hexamethylenediamine, dodecanediamine (molar ratio of hexamethylenediamine to dodecanediamine is 65:35), terephthalic acid, water, and sodium hypophosphite are fed into an 80°C salt-forming reactor at rates of 150.8 g / min, 140.0 g / min, 232 g / min, 261.4 g / min, and 0.7 g / min, respectively, with a residence time of 1 h. In this example, the auxiliary agent is sodium hypophosphite. The nylon salt solution at the outlet of the salt-forming reactor is 50%.

[0132] The nylon salt solution from step 1) is uniformly pumped to the brine buffer tank 3 at a rate (784.9 g / min in this embodiment) by the dilute brine metering pump 2, and then uniformly pumped to the heat exchanger 5 at a certain rate (710 g / min in this embodiment) by the dilute brine buffer metering pump 4. At this time, the dilute brine temperature at the outlet of the heat exchanger 5 is 180℃. The nylon salt solution continuously enters the 180℃ brine concentration tank through the heat exchanger at a rate of 744 g / min. After the signal output of the concentration transmitter C101 and the pH transmitter PH101 reaches the set parameter value of the first controller K1 of the concentration tank, that is, the mass concentration is 75% and the pH value is 7.2, the first regulating valve 101 is opened, and the material enters the first-stage tubular reactor 9. Under the control of the first controller K2 of the first-stage reactor, the first step is: the second regulating valve 201 and the back pressure valve 202 are closed simultaneously for 15 seconds, and the pressure in the first-stage tubular reactor 9 reaches the first set parameter 2. After reaching 4MPa, proceed to the second step; Second step: The second regulating valve 201 is opened for 7s, the back pressure valve 202 is closed for 7s, and after the pressure inside the first-stage tubular reactor 9 reaches the second set parameter of 1.7MPa, start the third step; Third step: The second regulating valve 201 is closed for 5s, the back pressure valve 202 is opened for 5s, and the material is transported to the second-stage tubular reactor 12 by pressure; When the pressure inside the first-stage tubular reactor 9 is lower than the third set parameter of 1.5MPa, repeat step 1, and dynamically cycle to continuously transport the material to the second-stage tubular reactor 12.

[0133] The material residence time in the secondary tubular reactor 12 is 1.2 hours, controlled by two secondary control modules of the secondary tubular reactor 12. The material is then transported from the secondary tubular reactor 12 to the tertiary tubular reactor 16. During this process:

[0134] The second-stage regulating valve 302, connected to the first-stage buffer tank 14, closes for 5 seconds, and the third-stage regulating valve 303 opens for 5 seconds. During this time, the first-stage buffer tank 14 is evacuated. Subsequently, the first-stage regulating valve 401, connected to the second-stage buffer tank 15, opens for 5 seconds, and the material in the second-stage tubular reactor 12 is transported to the second-stage buffer tank 15. Then, the first-stage regulating valve 401, connected to the second-stage buffer tank 15, closes for 5 seconds, and the second-stage regulating valve 402, connected to the second-stage buffer tank 14, opens for 5 seconds, and the material in the second-stage buffer tank 15 enters the tertiary tubular reactor 16.

[0135] The process is repeated in sequence, that is, when the first secondary buffer tank 14 is being fed, the second secondary buffer tank 15 is being evacuated; after the first secondary buffer tank 14 is finished being fed, it is being discharged, at which time the second secondary buffer tank 15 is being fed; this process is repeated in sequence, so that the first secondary buffer tank 14 and the second secondary buffer tank 15 are alternately fed and discharged.

[0136] The material resides in the three-stage tubular reactor 16 for 2.0 hours. Through two three-stage control modules, the second-stage regulating valve 502, connected to the first-stage buffer tank 17, closes for 5 seconds, and the third-stage regulating valve 503 opens for 5 seconds. At this time, the first-stage buffer tank 17 is evacuated. Subsequently, the first-stage regulating valve 601, connected to the second-stage buffer tank 18, opens for 5 seconds, and the material in the three-stage tubular reactor 16 is discharged into the second-stage buffer tank 18.

[0137] Subsequently, the second- and third-stage regulating valve 602, connected to the second- and third-stage buffer tank 18, is opened for 5 seconds, and then the first- and third-stage regulating valve 601 is closed for 5 seconds. The material in the second- and third-stage buffer tank 18 enters the product collection tank 19, and the cycle repeats. That is, when the first- and third-stage buffer tank 17 is feeding material, the second- and third-stage buffer tank 18 is evacuating. After the first- and third-stage buffer tank 17 finishes feeding material, it discharges material, and at this time, the second- and third-stage buffer tank 18 is feeding material. This cycle repeats, realizing the alternating feeding and discharging of the first- and third-stage buffer tank 17 and the second- and third-stage buffer tank 18.

[0138] Finally, continuous discharge yields granular / powdered PA6T / 12T final products.

[0139] Comparative Example 1

[0140] This comparative example utilizes the low-temperature continuous preparation control method of high-temperature resistant nylon PA6T / 6 from the above system, similar to Application Example 1, except that: the material enters the primary tubular reactor 9 and is controlled by the second controller K2. First step: the second regulating valve 201 and back pressure valve 202 are simultaneously closed for 5 seconds. After the pressure inside the primary tubular reactor 9 reaches the first set parameter of 2.1 MPa, the second step proceeds. Second step: the second regulating valve 201 is opened for 1 second, and the back pressure valve 202 is closed for 1 second. After the pressure inside the primary tubular reactor 9 reaches the second set parameter of 1.7 MPa, the third step is initiated. Third step: the second regulating valve 201 is closed for 1 second, and the back pressure valve 202 is opened for 1 second, allowing the material to be transported to the secondary tubular reactor 12 by pressure. When the pressure inside the primary tubular reactor 9 is lower than the third set parameter of 1.5 MPa, step 1 is repeated, and the material is continuously transported to the secondary tubular reactor 12 in a dynamic cycle.

[0141] Comparative Example 2

[0142] This comparative example utilizes the low-temperature continuous preparation control method of high-temperature resistant nylon PA6T / 12T using the above system. Similar to Application Example 2, the only difference is that the material enters the primary tubular reactor 9 and is controlled by the primary reactor control module K2. The process is as follows: First step: The second regulating valve 201 and back pressure valve 202 are simultaneously closed for 5 seconds. After the pressure inside the primary tubular reactor 9 reaches the set parameter, the second step is initiated. Second step: The second regulating valve 201 is opened for 1 second, and the back pressure valve 202 is closed for 1 second. After the pressure inside the primary tubular reactor 9 reaches the set parameter, the third step is initiated. Third step: The second regulating valve 201 is closed for 1 second, and the back pressure valve 202 is opened for 1 second. The material is transported to the secondary tubular reactor 12 by pressure. Step 1 is repeated, and the material is continuously transported to the secondary tubular reactor 12 in a dynamic cycle.

[0143] In an application example of the present invention, the physical properties of the obtained product were characterized, and the test reactors and test standards used for each characterization are shown below.

[0144] Table 1 Test Items, Test Equipment and Standards

[0145]

[0146] The measured data of the high-temperature resistant nylon obtained from Application Example 1-2 are shown in Table 2.

[0147] As can be seen from the data in Table 2, both types of nylon prepared using Examples 1 and 2 exhibit good melting points and mechanical properties. This indicates that the high-temperature resistant nylon obtained using the low-temperature continuous production method and control method for high-temperature resistant nylon has excellent performance. Furthermore, the inventors have successfully applied this method to the preparation of high-temperature resistant nylons PA6T / 10T, PA6T / 66, PA10N, MXD6, and PA6C / 66, achieving continuous production and producing products with good performance.

[0148] Table 2 Test Data

[0149] Test Project Application Example 1 Application Example 2 relative viscosity 2.87 2.76 Melting point / °C 313.00 325.00 Tensile strength / MPa 105.60 96.00 Elongation at break / % 37.00 40.00

[0150] Meanwhile, the control system and method of the present invention can also be used to quickly adjust the optimal production process of high-temperature resistant nylon. For example, the present invention studied the effect of changing control parameters on the performance of high-temperature resistant nylon. Application Example 1, Comparative Example 1 and Comparative Example 2 reflect the effect of changing the control parameters of the second control module on the performance of different types of high-temperature resistant nylon. The measured data are shown in Table 3.

[0151] Table 3 shows the impact of changes in the control parameters of the second control module on the properties of nylon based on Application Example 1.

[0152] Test Project Comparative Example 1 Comparative Example 2 relative viscosity 2.09 2.00 Melting point / °C 313.00 325.00 Tensile strength / MPa 80.00 73.00 Elongation at break / % 28.00 27.00

[0153] As can be seen from the data in Table 3, changes in the K2 parameter of the primary tubular reactor control module in the production process have a significant impact on the performance of high-temperature resistant nylon.

[0154] The control method described in this invention can control the production process of high-temperature resistant nylon. By adjusting the control parameters, the optimal high-temperature resistant nylon can be produced. It has a rapid response and can achieve continuous production.

Claims

1. A low-temperature continuous preparation system for high-temperature resistant nylon, characterized in that, The system includes a salt-forming kettle (1), a dilute brine metering pump (2), a brine buffer tank (3), a dilute brine buffer metering pump (4), a heat exchanger (5), a high-temperature dilute brine metering pump (6), a brine concentration tank (7), a high-temperature concentrated brine metering pump (8), a primary tubular reactor (9), a secondary tubular reactor (12), a tertiary tubular reactor (16), and a product collection tank (19), all connected in sequence by pipes. At least two secondary buffer tanks (14 / 15) are arranged side by side between the two-stage tubular reactor (12) and the three-stage tubular reactor (16). At least two tertiary buffer tanks (17 / 18) are arranged side by side between the tertiary tubular reactor (16) and the product collection tank (19). The salt-forming kettle (1), the first-stage tubular reactor (9), the second-stage buffer tank, and the third-stage buffer tank are all connected to a vacuum pump (21) via vacuum tubes. A first control module is connected to the brine concentration tank (7). The first control module collects the concentration signal and pH signal of the brine concentration tank (7) and outputs a signal to control whether the brine concentration tank (7) is connected to the first-stage tubular reactor (9) based on the collected concentration signal and pH signal. A second control module is connected to the first-stage tubular reactor (9). The second control module collects the pressure signal of the first-stage tubular reactor (9) and outputs a signal to control whether the first-stage tubular reactor (9) and the second-stage tubular reactor (12) are connected according to the pressure signal. The secondary buffer tank and the tertiary buffer tank are respectively connected to a secondary control module and a tertiary control module. The secondary control module / tertiary control module collects the pressure signal inside the secondary buffer tank / tertiary buffer tank and outputs a signal based on the pressure signal to control whether the secondary tubular reactor (12) is connected to the tertiary tubular reactor (16) / the tertiary tubular reactor (16) is connected to the product collection tank (19).

2. The low-temperature continuous preparation system for high-temperature resistant nylon as described in claim 1, characterized in that, The first control module includes a first controller (K1), a concentration transmitter (C101), a pH transmitter (PH101), and a first regulating valve (101). The signal output terminals of the concentration transmitter (C101) and the pH transmitter (PH101) are connected to the signal input terminal of the first controller (K1). The first controller (K1) outputs a signal to control the operation of the first regulating valve (101) and the high-temperature dilute brine metering pump (6). The first regulating valve (101) is connected between the brine concentration tank (7) and the first-stage tubular reactor (9).

3. The low-temperature continuous preparation system for high-temperature resistant nylon as described in claim 2, characterized in that, The second control module includes a second controller (K2), a back pressure valve (202), and a second regulating valve (201). The second controller (K2) outputs a signal to control the operation of the back pressure valve (202), the second regulating valve (201), and the high-temperature concentrated brine metering pump (8); A back pressure valve (202) is connected between the primary tubular reactor (9) and the secondary tubular reactor (12); The second regulating valve (201) is connected between the primary tubular reactor (9) and the distillation column (10).

4. The low-temperature continuous preparation system for high-temperature resistant nylon as described in claim 3, characterized in that, The secondary control module includes a secondary controller (K3), a secondary pressure transmitter (P301), a secondary first regulating valve (301), a secondary second regulating valve (302), and a secondary third regulating valve (303). The signal output terminal of the secondary pressure transmitter (P301) is connected to the secondary controller (K3). The secondary controller (K3) outputs signals to control the secondary first regulating valve (301), the secondary second regulating valve (302), and the secondary third regulating valve (303). The second-stage first regulating valve (301) is connected between the second-stage tubular reactor (12) and the second-stage buffer tank; the second-stage second regulating valve (302) is connected to the vacuum tube connected to the second-stage buffer tank; The secondary third regulating valve (303) is connected between the secondary buffer tank and the tertiary tubular reactor (16).

5. The low-temperature continuous preparation system for high-temperature resistant nylon as described in claim 4, characterized in that, The three-level control module includes a three-level controller (K5), a three-level pressure transmitter (P501), a three-level first regulating valve (501), a three-level second regulating valve (502), and a three-level third regulating valve (503). The signal output terminal of the three-stage pressure transmitter (P501) is connected to the three-stage controller (K5). The three-stage controller (K5) outputs signals to control the three-stage first regulating valve (501), the three-stage second regulating valve (502), and the three-stage third regulating valve (503). The third-stage first regulating valve (501) is connected between the third-stage tubular reactor (16) and the third-stage buffer tank; the third-stage second regulating valve (502) is connected between the third-stage buffer tank and the product collection tank (19); The third regulating valve (503) of the third stage is connected to the vacuum line connected to the third-stage buffer tank.

6. The low-temperature continuous preparation system for high-temperature resistant nylon as described in claim 5, 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).

7. The low-temperature continuous preparation system for high-temperature resistant nylon as described in claim 6, characterized in that, It 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 the 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).

8. The low-temperature continuous preparation system for high-temperature resistant nylon as described in claim 7, 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).

9. The method for controlling the low-temperature continuous preparation of high-temperature resistant nylon as described in claim 8, characterized in that: Includes the following steps: 1) In a nitrogen atmosphere, the raw materials are transported to the salt-forming kettle (1) at a certain rate and stay for a set time; the nylon salt solution is continuously fed into the salt concentration tank (7) through the heat exchanger (5). 2) Collect the concentration and pH signals in the brine concentration tank (7). When the concentration and pH are within the set range, the material in the brine concentration tank (7) enters the primary tubular reactor (9); otherwise, adjust the flow rate of the high-temperature dilute brine metering pump (6) until the concentration and pH of the material in the brine concentration tank (7) reach the set range. 3) The high-temperature brine solution reacts from bottom to top through the primary tubular reactor (9). This step involves the following three steps: Step 1: The second regulating valve (201) and the back pressure valve (202) are closed simultaneously for a set time. After the pressure inside the first-stage tubular reactor (9) reaches the first set parameter of 1.8 MPa to 2.4 MPa, the second step is carried out. Step 2: The second regulating valve (201) is opened for a set time, the back pressure valve (202) is closed for a set time, and after the pressure inside the first-stage tubular reactor (9) reaches the second set parameter of 1.5Mpa~1.8Mpa, the third step is started; Step 3: The second regulating valve (201) is closed for a set time, and the back pressure valve (202) is opened for a set time. The material is transported to the secondary tubular reactor (12) by pressure. When the pressure inside the primary tubular reactor (9) is lower than the third set parameter of 1.5 MPa, step 1 is repeated, and the material is continuously transported to the secondary tubular reactor (12) in a dynamic cycle. 4) The material stays in the secondary tubular reactor (12) for a set time, and the material is alternately transported from the secondary tubular reactor (12) to the tertiary tubular reactor (16) through two secondary buffer tanks. 5) The material stays in the three-stage tubular reactor (16) for a set time, and then enters the product collection tank (19) alternately through two three-stage buffer tanks from the three-stage tubular reactor (16).

10. The method for controlling the low-temperature continuous preparation of high-temperature resistant nylon as described in claim 9, characterized in that: The method for transferring materials from the secondary tubular reactor (12) to the tertiary tubular reactor (16) is as follows: This step includes the material entering the secondary tubular reactor (12) into the secondary buffer tank and from the secondary buffer tank into the tertiary tubular reactor (16); wherein there are two secondary buffer tanks, namely the first secondary buffer tank (14) and the second secondary buffer tank (15). The method for material to enter the secondary buffer tank from the secondary tubular reactor (12) is as follows: after the material has been in the secondary tubular reactor (12) for a set time, it enters the second secondary buffer tank (15), while the first secondary buffer tank (14) is subjected to negative pressure treatment at the same time. After the material enters the second secondary buffer tank (15), it begins to be discharged; at the same time, the material coming out of the secondary tubular reactor (12) begins to enter the first secondary buffer tank (14). The material discharge method in the second secondary buffer tank (15) is as follows: the discharge port of the second secondary buffer tank (15) is opened, and at this time, the first secondary buffer tank (14) is feeding; the material in the second secondary buffer tank (15) is discharged into the tertiary tubular reactor (16). After the second secondary buffer tank (15) is discharged, it is subjected to negative pressure treatment. At the same time, the material in the first secondary buffer tank (14) is discharged. This process is repeated cyclically to achieve alternating feeding and discharging; After a set time in the three-stage tubular reactor (16), the material enters the product collection tank (19); this step includes the material entering the three-stage buffer tank from the three-stage tubular reactor (16) and entering the product collection tank (19) from the three-stage buffer tank; there are two three-stage buffer tanks, namely the first three-stage buffer tank (17) and the second three-stage buffer tank (18). The method for the material to enter the third-stage buffer tank from the third-stage tubular reactor (16) is as follows: after the material enters the second-stage buffer tank (18) after a set time in the third-stage tubular reactor (16), the first-stage buffer tank (17) is subjected to negative pressure treatment at the same time. After the material enters the second and third stage buffer tanks (18), it begins to discharge. At the same time, the material coming out of the third stage tubular reactor (16) enters the first and third stage buffer tanks (17). The material discharge method in the second and third level buffer tanks (18) is as follows: the discharge port of the second and third level buffer tanks (18) is opened, and at this time, the first and third level buffer tanks (17) are feeding; the material in the second and third level buffer tanks (18) is discharged to the product collection tank (19). After the second and third level buffer tanks (18) finish discharging, negative pressure treatment is carried out. At the same time, the material in the first and third level buffer tanks (17) is discharged. This process is repeated in a cycle to achieve alternating feeding and discharging.

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