High-temperature-resistant nylon low-temperature continuous preparation system and control method thereof

Abstract

The invention belongs to the technical field of high-temperature-resistant nylon preparation, and discloses a high-temperature-resistant nylon low-temperature continuous preparation system and a control method thereof. The system comprises a salifying 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 collecting tank which are sequentially connected through pipelines, at least two second-stage buffer tanks are arranged between the second-stage tubular reactor and the third-stage tubular reactor in parallel; at least two third-stage buffer tanks are arranged between the third-stage tubular reactor and the product collecting tank in parallel, and a first control module, a second control module, a second-stage control module and a third-stage control module are arranged, so that respective production processes are controlled, materials produced in each process have quality uniformity, the control is more convenient, and the production efficiency is improved. And 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] The invention belongs to the technical field of high temperature resistant nylon preparation, and in particular relates to a low temperature continuous preparation system for high temperature resistant nylon and a control method thereof. Background Art

[0002] Due to its many advantages such as heat resistance, hydrolysis resistance, chemical corrosion resistance, good fluidity, and good molding stability, high-temperature nylon has been continuously developed in the application product field and the market capacity continues to expand. High-temperature nylon is a key material for new energy vehicle manufacturing and current electronic and electrical manufacturing. It can replace metal in the manufacture of key automotive components to meet the requirements of reducing weight and reducing energy consumption; it can adapt to the SMT process of current electronic and electrical manufacturing and meet the requirements of miniaturization, density, and low cost of electronic and electrical components. It is a special engineering plastic that is urgently needed to be developed in the domestic and foreign markets.

[0003] At present, the continuous preparation methods of high temperature resistant nylon mainly include melt continuous method and direct solid phase continuous polymerization method. Patents CN 114316255B and CN 115873236 A first use nylon salt solution as raw material and adopt melt continuous method to prepare nylon prepolymer, and then continuously transport the prepolymer to a twin-screw extruder for reaction 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 the polymerization process is above the melting point of the product. The reaction temperature is high, the product is prone to oxidation, and there are problems of yellowing and blackening.

[0004] Patent CN 112979941 B of Zhengzhou University uses powdered nylon salt as raw material, and adopts continuous direct solid phase polymerization method and supporting equipment to prepare powdered nylon products such as PA12T, PA6T / 66 and PA12T / 6T. The polymerization temperature of nylon prepared by this method is low, the side reaction is less, and the product quality is good. It solves the problem of oxidation yellowing and blackening in the preparation process of traditional high-temperature resistant nylon. At the same time, through the design of production equipment and systematic control of the process, continuous production is realized, the polymerization time is shortened, and the production cost is reduced; however, this method divides the preparation process of powdered nylon salt and the polymerization process of nylon salt into two steps, and has not yet realized the continuous production from diamine and dibasic acid to high-temperature nylon.

[0005] Based on patent CN 112979941 B, patent CN 114699989 A focuses on describing the application of timing control device in continuous solid phase polycondensation reaction to produce polyamide, and introduces the continuous solid phase polymerization reaction equipment and specific operation process in detail.

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

[0007] Whether it is intermittent polymerization, direct solid-phase polymerization or the current continuous polymerization method, they all have their shortcomings. Therefore, in order to efficiently prepare high-temperature resistant nylon products with stable performance, constant macromolecular chain composition and good quality, it is necessary to provide a low-temperature continuous preparation device and method for high-temperature resistant nylon. Summary of the invention

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

[0009] In order to solve the above 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 (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 salt solution concentration tank (7), a high-temperature concentrated salt solution metering pump (8), a first-stage tubular reactor (9), a second-stage tubular reactor (12), a third-stage tubular reactor (16) and a product collection tank (19) connected in sequence by pipelines;

[0010] At least two secondary buffer tanks (14 / 15) are arranged in parallel between the secondary tubular reactor (12) and the tertiary tubular reactor (16);

[0011] At least two tertiary buffer tanks (17 / 18) are arranged in parallel between the tertiary tubular reactor (16) and the product collecting tank (19);

[0012] 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 a vacuum pipe;

[0013] The salt solution concentration tank (3) is connected to a first control module, the first control module collects concentration signals and pH signals on the salt solution concentration tank (3), and outputs signals to control whether the salt solution concentration tank (3) is connected to the first-stage tubular reactor (9) according to the collected concentration signals and pH signals;

[0014] The first tubular reactor (9) is connected to a second control module, the second control module collects a pressure signal of the first tubular reactor (9), and outputs a signal to control whether the first tubular reactor (9) and the second tubular reactor (12) are connected according to the pressure signal;

[0015] 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 in the secondary buffer tank / tertiary buffer tank, and outputs a signal to control whether the secondary tubular reactor (12) and the tertiary tubular reactor (16) / the tertiary tubular reactor (16) and the product collection tank (19) are connected according to the pressure signal.

[0016] As a preferred embodiment of the present invention, 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 ends of the concentration transmitter (C101) and the pH transmitter (PH101) are connected to the signal input end of the first controller (K1), the first controller (K1) outputs a signal to control the operation of the first regulating valve (101) and the dilute salt solution metering pump (6), and the first regulating valve (101) is connected between the salt solution concentration tank (7) and the first-stage tubular reactor (9).

[0017] As a preferred embodiment of the present invention, the second control module includes a second controller (K2), a back pressure valve (202), and a second regulating valve (201);

[0018] The second controller outputs a signal to control the operation of the back pressure valve (202), the second regulating valve (201), and the high-temperature concentrated salt solution metering pump (8);

[0019] The back pressure valve (202) is connected between the first-stage tubular reactor (9) and the second-stage tubular reactor (12);

[0020] The second regulating valve (201) is connected between the first-stage tubular reactor (12) and the distillation tower (10).

[0021] As a preferred embodiment of the present invention, 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);

[0022] The signal output end of the secondary pressure transmitter (P301) is connected to the secondary controller (K3), and the secondary controller (K3) outputs a signal to control the secondary first regulating valve (301), the secondary second regulating valve (302) and the secondary third regulating valve (303);

[0023] The secondary first regulating valve (301) is connected between the secondary tubular reactor (12) and the secondary buffer tank; the secondary second regulating valve (302) is connected to the vacuum tube connected to the secondary buffer tank;

[0024] The secondary third regulating valve (302) is connected between the secondary buffer tank and the tertiary tubular reactor (16).

[0025] As a preferred embodiment of the present invention, 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);

[0026] The signal output end of the three-stage pressure transmitter (P501) is connected to the three-stage controller (K5), and the three-stage controller (K5) outputs a signal to control the three-stage first regulating valve (501), the three-stage second regulating valve (502) and the three-stage third regulating valve (503);

[0027] The third-level first regulating valve (501) is connected between the third-level tubular reactor (16) and the third-level buffer tank; the third-level second regulating valve (502) is connected between the third-level buffer tank (17) and the product collection tank (19).

[0028] The third-stage third regulating valve (503) is connected to the vacuum pipe connected to the third-stage buffer tank;

[0029] As a preferred embodiment of the present invention, the exhaust port of the secondary tubular reactor (12) is provided with a cyclone separator (13), and the material outlet at the bottom of the cyclone separator (13) is connected to the secondary tubular reactor (12).

[0030] As a preferred embodiment of the present invention, it also includes a distillation tower (10) connected to the top exhaust port of the first-stage tubular reactor (9), the distillation tower (10) includes a top exhaust port, a bottom discharge port and a side feed port located in the middle of the tower body, the top exhaust port of the distillation tower (10) is connected to the salt kettle (1) through a pipeline, and the bottom discharge port of the distillation tower (10) is connected to the feed port arranged at the bottom of the first-stage tubular reactor (9).

[0031] As a preferred embodiment of the present invention, a condensation tank (11) is provided between the distillation tower (10) and the salt-forming kettle (1), and between the salt solution concentration tank (7) and the salt-forming kettle (1).

[0032] The present invention further discloses a low-temperature continuous preparation control method of high-temperature resistant nylon in the above system, comprising the following steps:

[0033] 1) In a nitrogen atmosphere, the raw material is transported to a salt-forming kettle (1) at a certain rate and stays there for a set time; the nylon salt solution continuously enters a salt solution concentration tank (7) through a heat exchanger (5);

[0034] 2) collecting the concentration and pH signals in the salt solution concentration tank (7); when the concentration and pH signals are within the set range, the material in the salt solution concentration tank (7) enters the primary tubular reactor (9); otherwise, adjusting the flow rate of the high-temperature dilute salt solution metering pump (6) until the concentration and pH of the material in the salt solution concentration tank reach the set range;

[0035] 3) The high-temperature salt solution passes through the first-stage tubular reactor (9) from bottom to top to react. The control process of this step includes the following three steps:

[0036] The first step: the second regulating valve (201) and the back pressure valve (202) are closed simultaneously for a set time, and after the pressure in the first-stage tubular reactor (9) reaches the first set parameter of 1.8Mpa to 2.4Mpa, the second step is performed;

[0037] Step 2: The second regulating valve (201) is opened for a set time, and the back pressure valve (202) is closed for a set time. After the pressure in the first-stage tubular reactor (9) reaches a second set parameter of 1.5 MPa to 1.8 MPa, the third step is started;

[0038] Step 3: the second regulating valve (201) is closed for a set time, the back pressure valve (202) is opened for a set time, and the material is transported to the secondary tubular reactor (12) by pressure; when the pressure in the primary tubular reactor (9) is lower than the third set parameter 1.5 MPa, step 1 is repeated, and the material is continuously transported to the secondary tubular reactor (12) in a dynamic cycle in sequence;

[0039] 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) via two secondary buffer tanks;

[0040] 5) The material stays in the three-stage tubular reactor (16) for a set time, and then enters the product collection tank (19) from the three-stage tubular reactor (16) through two three-stage buffer tanks alternately.

[0041] As a preferred embodiment of the present invention, the method of transporting materials from the secondary tubular reactor (12) to the tertiary tubular reactor (16) is:

[0042] This step includes the material entering from 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);

[0043] The method for the material to enter the secondary buffer tank from the secondary tubular reactor (12) is as follows: after the material is in the secondary tubular reactor (12) for a set time, it enters the second secondary buffer tank (15), and at the same time, the first secondary buffer tank (14) is subjected to negative pressure treatment;

[0044] After the material enters the second secondary buffer tank (15), it starts to be discharged; at the same time, the material coming out of the secondary tubular reactor (12) starts to enter the first secondary buffer tank (14);

[0045] 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 three-stage tubular reactor (16); after the second secondary buffer tank (15) is discharged, negative pressure treatment is performed, and at the same time, the material in the first secondary buffer tank (15) is discharged;

[0046] Cycle in sequence to achieve alternating feeding and discharging;

[0047] After the material is in the three-stage tubular reactor (16) for a set time, it enters the product collection tank (19); this step includes the material entering from the three-stage tubular reactor (16) to the three-stage buffer tank and from the three-stage buffer tank to the product collection tank (19); wherein there are two three-stage buffer tanks, namely the first three-stage buffer tank (17) and the second three-stage buffer tank (18);

[0048] The method for the material to enter the three-stage buffer tank from the three-stage tubular reactor (16) is as follows: after the material enters the three-stage tubular reactor (16) for a set time, it enters the second three-stage buffer tank (18), and at the same time, the first three-stage buffer tank (17) is subjected to negative pressure treatment;

[0049] After the material enters the second tertiary buffer tank (18), the material discharge begins. At the same time, the material coming out of the tertiary tubular reactor (16) enters the first tertiary buffer tank (17);

[0050] The material discharge method in the second-third-level buffer tank (18) is as follows: the discharge port of the second-third-level buffer tank (18) is opened, and at this time, the first-third-level buffer tank (17) is feeding; the material in the second-third-level buffer tank (18) is discharged to the product collection tank (19), and after the second-third-level buffer tank 18 is discharged, negative pressure treatment is performed, and at the same time, the material in the second-third-level buffer tank (18) is discharged;

[0051] Cycle in sequence to achieve alternating feeding and discharging.

[0052] Through the above technical scheme, the technical effects of the present invention are as follows: The beneficial effects of the present invention are as follows: (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 secondary control module and the tertiary control module are set to realize the control of each production process, so that the materials produced in each process have uniform quality, the control is more convenient, and the continuous input and output of dibasic acid and diamine are realized; (3) The use of a first-stage tubular reactor can greatly increase the heat production efficiency and improve the reaction rate; (4) The secondary tubular reactor and the tertiary tubular reactor adopt a positive spiral propulsion design structure, which not only promotes the material transmission, but also plays a role in 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, and the optimized high-temperature resistant nylon can be produced by adjusting the control parameters, the reaction is rapid, and continuous production can be realized; (6) The optimal working parameters are found through experiments, which is helpful to obtain the best performance high-temperature resistant nylon. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the system of the present invention;

[0054] Figure 2 It is a schematic diagram of the connection from the secondary tubular reactor to the product collection tank;

[0055] 1-salting kettle, 2-dilute salt solution metering pump, 3-salt solution buffer tank, 4-dilute salt solution buffer metering pump, 5-heat exchanger, 6-high-temperature dilute salt solution metering pump, 7-salt solution concentration tank, 8-high-temperature concentrated salt solution metering pump, 9-first-stage tubular reactor, 10-rectifying tower, 11-condensing tank, 12-second-stage tubular reactor, 13-cyclone separator, 14-first-second-stage buffer tank, 15-second-second-stage buffer tank, 16-third-stage tubular reactor, 17-first-third-stage buffer tank, 18-second-third-stage buffer tank, 19-product collection tank; 20-vacuum tank, 21-vacuum pump; C101-concentration transmitter, PH101-acidity 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-three-stage first regulating valve, 502-three-stage second regulating valve, 503-three-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 DESCRIPTION

[0060] The following will be combined Figure 1 and Figure 2 The present invention is described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0061] It should be noted that:

[0062] The system and control method of the present invention are applicable to the preparation of various high temperature resistant nylons, including homopolymers and copolymers, such as semi-aromatic nylon, alicyclic nylon and naphthalene ring-containing nylon, etc., and have a wide range of applications. Among them, the nylon salt formula and its preparation are relatively mature, and the preparation of nylon salt can be achieved by using existing technology.

[0063] For example, when applying the present invention, the selection of raw materials can determine the dibasic acid, diamine and auxiliary agent and their dosage according to the prepared high-temperature resistant nylon. For example, the diamine can be a mixture of one or more of aliphatic diamine, aromatic diamine, alicyclic diamine and naphthalene ring-containing diamine, preferably butanediamine, pentanediamine, hexanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diamino-dicyclohexylmethane, 3,3'-dimethyl-4, The invention relates to a mixture of one or more of 4'-diamino-dicyclohexylmethane and 1,5-diaminonaphthalene; the dibasic acid is a mixture of one or more of an aliphatic dibasic acid, an aromatic dibasic acid, an alicyclic dibasic acid and a naphthalene ring-containing dibasic acid, preferably a mixture of one or more of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid, terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid and 1,4-cyclohexane dicarboxylic acid; the pH value of the nylon salt solution is 7.0 to 7.5.

[0064] Secondly, under the inspiration of this system, the technicians in this field select auxiliary agents, such as catalysts and antioxidants, wherein the catalyst can be selected from one or more of phosphorous acid, sodium hypophosphite, triphenyl phosphate, and H10. In the present invention, the inventors suggest that the amount of the catalyst is preferably 0.1% to 0.6% of the dry mass of the dibasic acid and the diamine, and the antioxidant is one or more of sodium hypophosphite, antioxidant 1010, antioxidant S9228, antioxidant SH120, and antioxidant B215. The amount of the antioxidant is preferably 0.1% to 0.6% of the dry mass of the dibasic acid and the diamine.

[0065] It should also be noted that the set value and the "certain rate" in the "concentration and pH on the salt solution concentration tank 7 meet the set value" described in the various embodiments or application examples of the present invention may vary slightly in a specific high-temperature resistant nylon reaction system, but this is predictable for those skilled in the art and can be clarified based on a limited number of experiments. The concentration set value on the salt solution concentration tank 7 of the present invention is 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, so the present invention does not make specific limitations.

[0066] In order to better illustrate the effect of the present invention, the present invention combines Figure 1 and Figure 2 The present invention is further described with reference to the accompanying drawings and specific embodiments.

[0067] Embodiment 1:

[0068] The low temperature continuous preparation system of high temperature resistant nylon in this embodiment is as follows: Figure 1 and Figure 2 As shown, it includes a salt-forming kettle 1, a salt solution buffer tank 3, a heat exchanger 5, a salt solution concentration tank 7, a primary tubular reactor 9, a secondary tubular reactor 12, a tertiary tubular reactor 16 and a product collecting tank 19 which are sequentially connected by pipelines; the primary tubular reactor 9 is a vertical tubular reactor; the secondary tubular reactor 12 and the tertiary tubular reactor 16 are both horizontal tubular reactors.

[0069] At least two secondary buffer tanks are arranged in parallel between the secondary tubular reactor 12 and the tertiary tubular reactor 16. In the present embodiment, the number of the secondary buffer tanks is two, and the two secondary buffer tanks are respectively the first secondary buffer tank 14 and the second secondary buffer tank 15; at least two tertiary buffer tanks are arranged in parallel between the tertiary tubular reactor 16 and the product collecting tank 19, and the two tertiary buffer tanks are respectively the first tertiary buffer tank 17 and the second tertiary buffer tank 18.

[0070] A cyclone separator 13 is provided at the exhaust port of the secondary tubular reactor 12 , and a material outlet at the bottom of the cyclone separator 13 is connected to the secondary tubular reactor 12 .

[0071] The system also includes a distillation tower 10 connected to the top exhaust port of the primary tubular reactor 9. The distillation tower 10 includes a top exhaust port, a bottom discharge port and a side feed port located in the middle of the tower body. The top exhaust port pipeline of the distillation tower 10 is connected to the salt kettle 1, and the bottom discharge port of the distillation tower 10 is connected to the feed port set at the bottom of the primary tubular reactor 9. A condenser tank 11 is set between the distillation tower 10 and the salt kettle 1, and between the salt liquid concentration tank 7 and the salt kettle 1. Metering pumps are set between the salt kettle 1 and the hydrochloric acid buffer tank 3, between the hydrochloric acid buffer tank 3 and the heat exchanger 5, between the heat exchanger 5 and the salt liquid concentration tank 7, and between the salt liquid concentration tank 7 and the primary tubular reactor 9.

[0072] Metering pumps such as Figure 1 As shown in the figure, there are respectively a dilute salt solution metering pump 2, a buffer solution metering pump 4, a high-temperature dilute salt solution metering pump 6 and a high-temperature concentrated salt solution metering pump 8, the purpose of which is to control the material flow rate, and then control the retention time of the material in the device. The salt forming kettle 1, the salt solution buffer tank 3, and the salt solution concentration tank 7 are all provided with a stirring device, and the stirring device and the like are all conventional settings in the field, and this device will not be described in detail.

[0073] 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 the vacuum pump 21 through a vacuum tube, so that a positive pressure system is formed in the first-stage tubular reactor 9, for example, the pressure is 1.5MPa~2.4MPa, the second-stage tubular reactor 12 forms a positive pressure system, for example, the pressure is 0.2MPa~1.0MPa, and the third-stage tubular reactor 16 forms a negative pressure system, for example, the pressure is 5Pa~500Pa; thereby ensuring that the system material is continuous and the pressure is stable.

[0074] In order to facilitate the reaction, ensure that the materials produced in each process have uniform quality, make the control more convenient, and improve the use effect, a first control module is connected to the salt solution concentration tank 7, and the first control module collects the concentration and pH signals on the salt solution concentration tank 7, and controls whether the salt solution concentration tank 7 is connected to the primary tubular reactor 9 according to the collected signal output signal. Among them, the first control module includes a first controller K1, a concentration transmitter C101, a pH transmitter PH101, a first regulating valve 101 and a dilute salt solution metering pump 6.

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

[0076] The concentration transmitter C101 and the pH transmitter PH101 respectively collect concentration and pH information, and transmit the collected information to the first controller K1. The first controller K1 opens the first regulating valve 101 based on the received signal if the concentration and pH meet the set values, 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 value are higher than the set value, the first controller K1 outputs a signal to close the first regulating valve 101, adjusts the flow rate of the dilute salt solution metering pump 6, and reduces the concentration and pH value until the set value is reached. Subsequently, the first controller K1 outputs a signal to open the first regulating valve 101, and the material in the salt solution concentration tank 7 whose concentration and pH value meet the set value enters the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8. In this embodiment, although the concentration and pH value are two values, when the concentration is constant, the pH value of the material is generally determined. By collecting the two values ​​of the concentration and pH value of the system, the accuracy can be improved.

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

[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 salt solution metering pump 8;

[0080] The first pressure transmitter collects the pressure signal in 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 salt solution metering pump 8 according to the received pressure signal.

[0082] The high-temperature concentrated salt solution metering pump 8 is connected between the salt solution concentration tank 7 and the first-stage tubular reactor 9;

[0083] The back pressure valve 202 is connected between the first-stage tubular reactor 9 and the second-stage tubular reactor 12;

[0084] The second regulating valve 201 is connected between the first-stage tubular reactor 9 and the distillation tower.

[0085] Only when the pressure in the primary tubular reactor 9 reaches the set value, the primary tubular reactor 9 and the secondary tubular reactor 12 are connected, and the material in the primary tubular reactor 9 enters the secondary tubular reactor 12 through the high-temperature concentrated salt solution metering pump 8. In this embodiment, the high-temperature salt solution reacts from bottom to top through the primary tubular reactor 9, and the system pressure increases. Within the set time, the second regulating valve 201 is opened and the back pressure valve 202 is closed. When the system pressure reaches the set pressure of the back pressure valve 202, the back pressure valve 202 is opened, the second regulating valve 201 is closed, and the high-temperature concentrated salt solution metering pump 8 is opened, and the material quickly enters the secondary tubular reactor 12. The opening and closing are alternately performed in sequence to realize the continuous transportation of the material.

[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 control module / tertiary control module collects the pressure signal in the secondary buffer tank / tertiary buffer tank, and controls whether the secondary tubular reactor 12 and the tertiary tubular reactor 16 / the tertiary tubular reactor 16 and the product collection tank 19 are connected according to the pressure signal output signal.

[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, and the signal output end 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 secondary first regulating valve 301 is connected between the secondary tubular reactor 12 and the secondary buffer tank; the secondary second regulating valve 302 is connected to the vacuum tube connected to the secondary buffer tank 14;

[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 for reaction.

[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, and the signal output end 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-level first regulating valve 501 is connected between the third-level tubular reactor 16 and the third-level buffer tank; the third-level second regulating valve 502 is connected between the third-level buffer tank and the product collecting tank 19. When the third-level third regulating valve is opened, the material enters the product collecting tank 19 from the third-level buffer tank.

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

[0095] In this embodiment, the first controller K1, the second controller K2, the secondary controller K3 and the tertiary controller K5 can all be single-chip microcomputers. When implemented, a single-chip microcomputer of the model STM32F103C8T6 can be selected.

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

[0097] The single chip microcomputer output signal controls the opening, closing and opening size adjustment of the electric regulating valve or the electric back pressure valve 202, which is a mature prior art, and this embodiment does not elaborate on its implementation method.

[0098] The concentration transmitter C101, pH transmitter PH101 and pressure transmitter are also directly selected from commercially available products. At the same time, they transmit the collected concentration, pH and pressure information to the single-chip microcomputer, which compares the received signal with the threshold. This is a mature existing technology, and this embodiment does not elaborate on its implementation method.

[0099] The single chip microcomputer output signal controls the work of the metering pump, which is a mature prior art. This embodiment does not involve the improvement of this part and will not be described in detail.

[0100] The system described in the present invention discloses a low-temperature continuous preparation system for high-temperature resistant nylon, which can realize low-temperature continuous production, has high product quality, high production efficiency, low production cost and saves energy.

[0101] This embodiment also discloses a low-temperature continuous preparation control method for high-temperature resistant nylon of 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 stay there for a set time; the nylon salt solution continuously enters the salt solution concentration tank 7 through the heat exchanger 5;

[0103] 2) Collect the concentration and pH signals in the salt solution 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 salt solution concentration tank 7 enters the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8.

[0104] If the concentration and pH value are higher than the set value, the first controller K1 outputs a signal to close the first regulating valve 101, adjusts the flow rate of the dilute salt solution metering pump 6, and reduces the concentration and pH value until the set value is reached. Subsequently, the first controller K1 outputs a signal to open the first regulating valve 101, and the material in the salt solution concentration tank 7 whose concentration and pH value meet the set value enters the primary tubular reactor 9 through the high-temperature concentrated salt solution metering pump 8. In this embodiment, although the concentration and pH value are two values, when the concentration is constant, the pH value of the material is generally determined. In this embodiment, the accuracy can be improved by collecting the concentration and pH value of the system.

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

[0106] Step 1: The second regulating valve 201 and the back pressure valve 202 are closed at the same time for a set time. After the pressure in the first-stage tubular reactor 9 reaches the set parameter of 1.8Mpa to 2.4Mpa, the second step is performed;

[0107] Step 2: The second regulating valve 201 is opened for a set time, and the back pressure valve 202 is closed for a set time. After the pressure in the first-stage tubular reactor 9 reaches the set parameter of 1.5Mpa to 1.8Mpa, 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, and the material is transported to the secondary tubular reactor 12 by pressure; when the pressure in the primary tubular reactor (9) is lower than the third set parameter 1.5 MPa, 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 is continuously transformed from a homogeneous fluid state to a porous particle / powder state.

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

[0111] The method of transporting materials from the secondary tubular reactor 12 to the tertiary tubular reactor 16 is as follows:

[0112] This step includes the material entering from the secondary tubular reactor 12 to the secondary buffer tank and from the secondary buffer tank to the tertiary tubular reactor 16; wherein the material enters from the secondary tubular reactor 12 to the secondary buffer tank in the following manner: the two secondary buffer tanks are respectively the first secondary buffer tank 14 and the second secondary buffer tank;

[0113] After the material has been in the secondary tubular reactor 12 for a set time, it enters the second secondary buffer tank, and at the same time, the first secondary buffer tank 14 is subjected to negative pressure treatment;

[0114] After the material enters the second secondary buffer tank, it starts to be discharged; at the same time, the material coming out of the secondary tubular reactor 12 starts to enter the first secondary buffer tank 14;

[0115] The material discharge method in the second-level buffer tank is as follows: the discharge port of the second-level buffer tank is opened, at this time, the first-level buffer tank 14 is feeding; the material in the second-level buffer tank is discharged into the tertiary tubular reactor 16, and after the second-level buffer tank is discharged, negative pressure treatment is performed, and at the same time, the material in the first-level buffer tank 14 is started to be discharged, and the cycle is carried out in sequence to achieve alternating feeding and discharging.

[0116] 5) The material stays in the three-stage tubular reactor 16 for a set time, and then alternately enters the product collection tank 19 from the three-stage tubular reactor 16 through two three-stage buffer tanks.

[0117] After the material is in the three-stage tubular reactor 16 for a set time, it 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; wherein the material enters the three-stage buffer tank from the three-stage tubular reactor 16, and the two three-stage buffer tanks are the first three-stage buffer tank 17 and the second three-stage buffer tank 18;

[0118] After the material has been in the three-stage tubular reactor 16 for a set time, it 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 tertiary buffer tank 18, it starts to be discharged. At the same time, the material coming out of the tertiary tubular reactor 16 enters the first tertiary buffer tank 17;

[0120] The material discharge method in the second-third-level buffer tank 18 is as follows: the discharge port of the second-third-level buffer tank 18 is opened, at this time, the first-third-level buffer tank 17 is feeding; the material in the second-third-level buffer tank 18 is discharged to the product collection tank 19, and after the second-third-level buffer tank 18 is discharged, negative pressure treatment is performed, and at the same time, the material in the second-third-level buffer tank 18 is started to be discharged, and the cycle is carried out in sequence to achieve alternating feeding and discharging.

[0121] Application Example 1

[0122] This embodiment takes the preparation of PA6T / 6 as an example to provide a control method for using the above system to realize the low-temperature continuous method for preparing PA6T / 66 from high-temperature resistant nylon, which includes the following steps in sequence: in a nitrogen atmosphere, hexamethylenediamine, terephthalic acid, caprolactam (the molar ratio of terephthalic acid to caprolactam is 60:40), water and auxiliary agent are respectively transported to a 60°C salting kettle at a rate of 208.8 g / min, 298.8 g / min, 135.6 g / min, 257.8 g / min and 1 g / min, and the residence time is 1 hour; in this embodiment, the auxiliary agent is sodium hypophosphite. The nylon salt solution at the outlet of the salting kettle is 40%.

[0123] The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a certain rate (901.48 g / min in this embodiment), and then uniformly transported to the heat exchanger 5 through the dilute salt solution buffer metering pump 4 at a certain rate (800 g / min in this embodiment). 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 continuously enters the 180°C salt solution concentration tank through the heat exchanger, and after the signal output of the concentration transmitter C101 and the pH transmitter PH101 reaches the parameter value set by 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 tubular reactor 9, and passes through the first The first control of the reactor is controlled by K2. The first step is: the second regulating valve 201 and the back pressure valve 202 are closed at the same time for 15 seconds. After the pressure in the first tubular reactor 9 reaches the first setting parameter of 2.1MPa, the second step is performed; the second step is: the second regulating valve 201 is opened for 7 seconds, the back pressure valve 202 is closed for 7 seconds, and the pressure in the first tubular reactor 9 reaches the second setting parameter of 1.6MPa, and the third step is started; the third step is: the second regulating valve 201 is closed for 5 seconds, the back pressure valve 202 is opened for 5 seconds, and the material is transported to the second tubular reactor 12 by pressure; when the pressure in the first tubular reactor 9 is lower than the third setting parameter of 1.5MPa, step 1 is repeated, and the material is continuously transported to the second tubular reactor 12 in a dynamic cycle. The main purpose of setting the pressure parameters in this embodiment is to realize the pressure difference between the first tubular reactor and the second tubular reactor, and the material is smoothly and continuously transported under the action of the pressure difference.

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

[0125] The second-level regulating valve 302 connected to the first-level buffer tank 14 is closed for 3 seconds, and the third-level regulating valve 303 is opened for 3 seconds. At this time, the first-level buffer tank 14 is evacuated again; then, the first-level regulating valve 401 connected to the second-level buffer tank 15 is opened for 3 seconds, and the material in the secondary tubular reactor 12 is transported to the second-level buffer tank 15; then, the first-level regulating valve 401 connected to the second-level buffer tank 15 is closed for 3 seconds, and the second-level regulating valve 402 connected to the second second-level buffer tank 14 is opened for 3 seconds, and the material in the second-level tubular reactor 15 enters the tertiary tubular reactor 16.

[0126] The process is circulated sequentially, that is, when the first and second buffer tanks 14 are feeding, the second and second buffer tanks 15 are evacuating the gas; after the first diode buffer tank 14 has finished feeding, it is discharged, and at this time, the second and second buffer tanks 15 are feeding; the process is circulated sequentially to realize alternating feeding and discharging of the first and second buffer tanks 14 and 15.

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

[0128] Subsequently, the second-third-stage regulating valve 602 connected to the second-third-stage buffer tank 18 is opened for 3 seconds, and then the first-third-stage regulating valve 601 is closed for 3 seconds, and the material in the second-third-stage buffer tank 18 enters the product collecting tank 19, and the cycle is alternating in sequence. That is, when the first-third-stage buffer tank 17 is feeding, the second-third-stage buffer tank 18 is in the vacuum treatment; after the first-third-stage buffer tank 17 completes the feeding, it is discharged. At this time, the second-third-stage buffer tank 18 is feeding, and the cycle is in sequence to realize the alternating feeding and discharging of the first-third-stage buffer tank 17 and the second-third-stage buffer tank 18.

[0129] Finally, the final PA6T / 6 product in granular / powder form is obtained by continuous discharging.

[0130] Application Example 2

[0131] This application example takes the preparation of PA6T / 12T as an example to provide a control method for using the above system to realize the low-temperature continuous preparation of PA6T / 12T by high-temperature resistant nylon, which includes the following steps in sequence: in a nitrogen atmosphere, hexamethylenediamine, dodecanediamine (the molar ratio of hexamethylenediamine to dodecanediamine is 65:35), terephthalic acid, water and sodium hypophosphite are respectively delivered to a salting kettle at 80°C at 150.8g / min, 140.0g / min, 232g / min, 261.4g / min, and 0.7g / min, and the residence time is 1h. In this embodiment, the auxiliary agent is sodium hypophosphite. The nylon salt solution at the outlet of the salting kettle is 50%.

[0132] The nylon salt solution of step 1) is uniformly transported to the salt solution buffer tank 3 through the dilute salt solution metering pump 2 at a rate (784.9 g / min in this embodiment), and then uniformly transported to the heat exchanger 5 at a certain rate (710 g / min in this embodiment) through the dilute salt solution buffer metering pump 4. 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 continuously enters the 180°C salt solution concentration tank through the heat exchanger at a rate of 744 g / min, and after the signal output of the concentration transmitter C101 and the pH transmitter PH101 reaches the parameter value set by 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 primary tubular reactor 9, and passes through the primary reaction The first control K2 of the reactor is controlled, the first step: the second regulating valve 201 and the back pressure valve 202 are closed at the same time for 15s. After the pressure in the first tubular reactor 9 reaches the first set parameter of 2.4MPa, the second step is carried out; the second step: the second regulating valve 201 is opened for 7s, the back pressure valve 202 is closed for 7s, and after the pressure in the first tubular reactor 9 reaches the second set parameter of 1.7MPa, the third step is started; the 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 tubular reactor 12 by pressure; when the pressure in the first 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 second tubular reactor 12 in a dynamic cycle.

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

[0134] The second-level regulating valve 302 connected to the first-level buffer tank 14 is closed for 5 seconds, and the third-level regulating valve 303 is opened for 5 seconds. At this time, the first-level buffer tank 14 is evacuated again; then, the first-level regulating valve 401 connected to the second-level buffer tank 15 is opened for 5 seconds, and the material in the second tubular reactor 12 is transported to the second-level buffer tank 15; then, the first-level regulating valve 401 connected to the second-level buffer tank 15 is closed for 5 seconds, and the second-level regulating valve 402 connected to the second second-level buffer tank 14 is opened for 5 seconds, and the material in the second-level buffer tank 15 enters the tertiary tubular reactor 16.

[0135] The process is circulated sequentially, that is, when the first and second buffer tanks 14 are feeding, the second and second buffer tanks 15 are evacuating the gas; after the first diode buffer tank 14 has finished feeding, it is discharged, and at this time, the second and second buffer tanks 15 are feeding; the process is circulated sequentially to realize alternating feeding and discharging of the first and second buffer tanks 14 and 15.

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

[0137] Subsequently, the second-third-stage regulating valve 602 connected to the second-third-stage buffer tank 18 is opened for 5 seconds, and then the first-third-stage regulating valve 601 is closed for 5 seconds, and the material in the second-third-stage buffer tank 18 enters the product collecting tank 19, and the cycle is alternating in sequence. That is, when the first-third-stage buffer tank 17 is feeding, the second-third-stage buffer tank 18 is in the vacuum treatment; after the first-third-stage buffer tank 17 completes the feeding, it is discharged. At this time, the second-third-stage buffer tank 18 is feeding, and the cycle is in sequence to realize the alternating feeding and discharging of the first-third-stage buffer tank 17 and the second-third-stage buffer tank 18.

[0138] Finally, the final PA6T / 12T product in granular / powder form is obtained by continuous discharging.

[0139] Comparative Example 1

[0140] This comparative example uses the low-temperature continuous preparation control method of high-temperature resistant nylon PA6T / 6 of the above-mentioned system, which is the same as Application Example 1, except that: the material enters the first-level tubular reactor 9 and is controlled by the second controller K2. The first step: the second regulating valve 201 and the back pressure valve 202 are closed at the same time for 5 seconds. After the pressure in the first-level tubular reactor 9 reaches the first set parameter of 2.1Mpa, the second step is carried out; the second step: the second regulating valve 201 is opened for 1S, the back pressure valve 202 is closed for 1S, and the pressure in the first-level tubular reactor 9 reaches the second set parameter of 1.7Mpa, and the third step is started; the third step: the second regulating valve 201 is closed for 1S, the back pressure valve 202 is opened for 1S, and the material is transported to the second-level tubular reactor 12 by pressure; when the pressure in the first-level 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 second-level tubular reactor 12 in a dynamic cycle.

[0141] Comparative Example 2

[0142] This comparative example uses the high-temperature resistant nylon PA6T / 12T low-temperature continuous preparation control method of the above-mentioned system, which is the same as Application Example 2. The only difference from Application Example 2 is that the material enters the first-level tubular reactor 9 and is controlled by the first-level reactor control module K2. The first step: the second regulating valve 201 and the back pressure valve 202 are closed at the same time for 5 seconds. After the pressure in the first-level tubular reactor 9 reaches the set parameters, the second step is carried out; the second step: the second regulating valve 201 is opened for 1S, and the back pressure valve 202 is closed for 1S. After the pressure in the first-level tubular reactor 9 reaches the set parameters, the set third step is started; the third step: the second regulating valve 201 is closed for 1S, and the back pressure valve 202 is opened for 1S, and the material is transported to the second-level tubular reactor 12 by pressure; repeat step 1, and dynamically cycle in sequence to realize continuous transportation of materials to the second-level tubular reactor 12.

[0143] In the application examples of the present invention, the physical properties of the obtained products were characterized, and the test reactors and test standards used in each characterization are shown below.

[0144] Table 1 Test items, test equipment and standards

[0145]

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

[0147] From the data in Table 2, it can be seen that the two types of nylon prepared in Application Examples 1 and 2 have good melting points and mechanical properties, which shows that the high-temperature resistant nylon prepared by the low-temperature continuous preparation system and control method of high-temperature resistant nylon has excellent performance. In addition, the inventors have successfully applied it to the preparation of high-temperature resistant nylon PA6T / 10T, PA6T / 66, PA10N, MXD6 and PA6C / 66, etc., and continuous production can be achieved and the obtained products have good performance.

[0148] Table 2 Test data

[0149] Test items Application Example 1 Application Example 2 Relative viscosity 2.87 2.76 Melting point / ℃ 313.00 325.00 Tensile strength / MPa 105.60 96.00 Elongation at break / % 37.00 40.00

[0150] At the same time, 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 studies 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 Effect of changes in the control parameters of the second control module on nylon properties based on Application Example 1

[0152] Test items Comparative Example 1 Comparative Example 2 Relative viscosity 2.09 2.00 Melting point / ℃ 313.00 325.00 Tensile strength / MPa 80.00 73.00 Elongation at break / % 28.00 27.00

[0153] It can be seen from the data in Table 3 that the change of the K2 parameter of the first-level tubular reactor control module in the production process has a greater impact on the performance of high-temperature resistant nylon.

[0154] The control method of the present invention can realize the control of the production process of high-temperature resistant nylon, and can produce the most optimized high-temperature resistant nylon by adjusting the control parameters, and has a rapid response and can realize continuous production.

Claims

1. A low temperature continuous preparation system for high temperature resistant nylon, characterized in that: The invention 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 salt solution concentration tank (7), a high-temperature concentrated salt solution metering pump (8), a first-stage tubular reactor (9), a second-stage tubular reactor (12), a third-stage tubular reactor (16) and a product collecting tank (19) which are sequentially connected by pipelines; At least two secondary buffer tanks (14 / 15) are arranged in parallel between the secondary tubular reactor (12) and the tertiary tubular reactor (16); at least two tertiary buffer tanks (17 / 18) are arranged in parallel between the tertiary tubular reactor (16) and the product collecting tank (19); the salt forming kettle (1), the primary tubular reactor (9), the secondary buffer tank, and the tertiary buffer tank are all connected to a vacuum pump (21) via a vacuum pipe; The salt solution concentration tank (3) is connected to a first control module, the first control module collects concentration signals and pH signals on the salt solution concentration tank (3), and outputs signals to control whether the salt solution concentration tank (3) is connected to the first-stage tubular reactor (9) according to the collected concentration signals and pH signals; The first tubular reactor (9) is connected to a second control module, the second control module collects a pressure signal of the first tubular reactor (9), and outputs a signal to control whether the first tubular reactor (9) and the second 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 in the secondary buffer tank / tertiary buffer tank, and outputs a signal to control whether the secondary tubular reactor (12) and the tertiary tubular reactor (16) / the tertiary tubular reactor (16) and the product collection tank (19) are connected according to the pressure signal.

2. The low-temperature continuous preparation system of high-temperature resistant nylon according to claim 1, characterized in that: The first control module comprises a first controller (K1), a concentration transmitter (C101), a pH transmitter (PH101) and a first regulating valve (101); the signal output ends of the concentration transmitter (C101) and the pH transmitter (PH101) are connected to the signal input end of the first controller (K1); the first controller (K1) outputs a signal to control the operation of the first regulating valve (101) and the dilute salt solution metering pump (6); and the first regulating valve (101) is connected between the salt solution concentration tank (7) and the first-stage tubular reactor (9).

3. The low temperature continuous preparation system of high temperature resistant nylon according to claim 2, characterized in that: The second control module comprises 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 salt solution metering pump (8); The back pressure valve (202) is connected between the first-stage tubular reactor (9) and the second-stage tubular reactor (12); The second regulating valve (201) is connected between the first-stage tubular reactor (12) and the distillation tower (10).

4. The low-temperature continuous preparation system of high-temperature resistant nylon according to claim 3, characterized in that: The secondary control module comprises 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 end of the secondary pressure transmitter (P301) is connected to the secondary controller (K3), and the secondary controller (K3) outputs a signal to control the secondary first regulating valve (301), the secondary second regulating valve (302) and the secondary third regulating valve (303); The secondary first regulating valve (301) is connected between the secondary tubular reactor (12) and the secondary buffer tank; the secondary second regulating valve (302) is connected to the vacuum tube connected to the secondary buffer tank; The secondary third regulating valve (303) is connected between the secondary buffer tank (14) and the tertiary tubular reactor (16).

5. The low temperature continuous preparation system of high temperature resistant nylon according to 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 end of the three-stage pressure transmitter (P501) is connected to the three-stage controller (K5), and the three-stage controller (K5) outputs a signal 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 (17); the third-stage second regulating valve (502) is connected between the third-stage buffer tank (17) and the product collection tank (19); The third-stage third regulating valve (503) is connected to the vacuum pipeline connected to the third-stage buffer tank.

6. The low-temperature continuous preparation system of high-temperature resistant nylon according to claim 5, characterized in that: The exhaust port of the two-stage tubular reactor (12) is provided with a cyclone separator (13), and the material outlet at the bottom of the cyclone separator (13) is connected to the two-stage tubular reactor (12).

7. The low-temperature continuous preparation system of high-temperature resistant nylon according to claim 6, characterized in that: It also comprises a distillation tower (10) connected to the top exhaust port of the first-stage tubular reactor (9), the distillation tower (10) comprising a top exhaust port, a bottom discharge port and a side feed port located in the middle of the tower body, the top exhaust port of the distillation tower (10) is connected to the salt kettle (1) through a pipeline, and the bottom discharge port of the distillation tower (10) is connected to the feed port arranged at the bottom of the first-stage tubular reactor (9).

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

9. The control method for low-temperature continuous preparation of high-temperature resistant nylon according to claim 8, characterized in that: The following steps are involved: 1) In a nitrogen atmosphere, the raw material is transported to a salt-forming kettle (1) at a certain rate and stays there for a set time; the nylon salt solution continuously enters a salt solution concentration tank (7) through a heat exchanger (5); 2) collecting the concentration and pH signals in the salt solution concentration tank (7); when the concentration and pH signals are within the set range, the material in the salt solution concentration tank (7) enters the primary tubular reactor (9); otherwise, adjusting the flow rate of the high-temperature dilute salt solution metering pump (6) until the concentration and pH of the material in the salt solution concentration tank (7) reach the set range; 3) The high-temperature salt solution passes through the first-stage tubular reactor (9) from bottom to top to react. The control process of this step includes the following three steps: The first step: the second regulating valve (201) and the back pressure valve (202) are closed simultaneously for a set time, and after the pressure in the first-stage tubular reactor (9) reaches the first set parameter of 1.8Mpa to 2.4Mpa, the second step is performed; Step 2: The second regulating valve (201) is opened for a set time, and the back pressure valve (202) is closed for a set time. After the pressure in the first-stage tubular reactor (9) reaches a second set parameter of 1.5 MPa to 1.8 MPa, the third step is started; Step 3: the second regulating valve (201) is closed for a set time, the back pressure valve (202) is opened for a set time, and the material is transported to the secondary tubular reactor (12) by pressure; when the pressure in the primary tubular reactor (9) is lower than the third set parameter 1.5 MPa, step 1 is repeated, and the material is continuously transported to the secondary tubular reactor (12) in a dynamic cycle in sequence; 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) via two secondary buffer tanks; 5) The material stays in the three-stage tubular reactor (16) for a set time, and then passes through two three-stage buffer tanks from the three-stage tubular reactor (16) and enters the product collection tank (19) alternately.

10. The low temperature continuous preparation control method of high temperature resistant nylon according to claim 9, characterized in that: The method for transporting materials from the secondary tubular reactor (12) to the tertiary tubular reactor (16) is as follows: This step includes the material entering from 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 the material to enter the secondary buffer tank from the secondary tubular reactor (12) is as follows: after the material is in the secondary tubular reactor (12) for a set time, it enters the second secondary buffer tank (15), and at the same time, the first secondary buffer tank (14) is subjected to negative pressure treatment; After the material enters the second secondary buffer tank (15), it starts to be discharged; at the same time, the material coming out of the secondary tubular reactor (12) starts 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 three-stage tubular reactor (16); after the second secondary buffer tank (15) is discharged, negative pressure treatment is performed, and at the same time, the material in the first secondary buffer tank (15) is discharged; Cycle in sequence to achieve alternating feeding and discharging; After the material is in the three-stage tubular reactor (16) for a set time, it enters the product collection tank (19); this step includes the material entering from the three-stage tubular reactor (16) to the three-stage buffer tank and from the three-stage buffer tank to the product collection tank (19); wherein 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 three-stage buffer tank from the three-stage tubular reactor (16) is as follows: after the material enters the three-stage tubular reactor (16) for a set time, it enters the second three-stage buffer tank (18), and at the same time, the first three-stage buffer tank (17) is subjected to negative pressure treatment; After the material enters the second tertiary buffer tank (18), the material discharge begins. At the same time, the material coming out of the tertiary tubular reactor (16) enters the first tertiary buffer tank (17); The material discharge method in the second-third-level buffer tank (18) is as follows: the discharge port of the second-third-level buffer tank (18) is opened, and at this time, the first-third-level buffer tank (17) is feeding; the material in the second-third-level buffer tank (18) is discharged to the product collection tank (19), and after the second-third-level buffer tank 18 is discharged, negative pressure treatment is performed, and at the same time, the material in the second-third-level buffer tank (18) is discharged; Cycle in sequence to achieve alternating feeding and discharging.

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