Method and system for continuously preparing long carbon chain nylon and obtained long carbon chain nylon

Abstract

The invention provides a method and a system for continuously preparing long carbon chain nylon and the obtained long carbon chain nylon. The method comprises the following steps: mixing raw materials including long-carbon-chain nylon salt and water, heating and melting to obtain a nylon salt aqueous solution, stabilizing, heating, carrying out prepolymerization reaction to obtain a prepolymer, carrying out flash evaporation, gas-liquid separation and final polymerization to obtain a product, and treating to obtain the long-carbon-chain nylon. The system comprises a molten salt kettle, an intermediate tank, a preheater, a prepolymerization reactor, a flash evaporator, a gas-liquid separator and a final polymerization reactor, the molten salt kettle, the intermediate tank, the preheater, the prepolymerization reactor, the flash evaporator, the gas-liquid separator and the final polymerization reactor are connected in sequence. The method provided by the invention can realize continuous production of long carbon chain nylon, and has the advantages of higher production efficiency, more stable production, and more controllable molecular weight and distribution.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials. Further, it relates to a method and system for continuously preparing long-chain nylon and the obtained long-chain nylon. Background Art

[0002] Long-chain nylons, such as nylon 1212, etc., have characteristics such as low density, low water absorption rate, good dimensional stability, excellent chemical resistance, corrosion resistance, wear resistance, fatigue resistance, and good low-temperature impact resistance. They are mainly used in industries such as automobiles, electrical appliances, and machinery, such as coil skeletons, insulating layers of wires and cables, fuel oil pipelines, hydraulic system pipelines, conduits, etc.

[0003] Generally, the method of prepolymerization and solid-phase viscosity increase is often used to prepare long-chain nylons. It is a batch reaction process, which requires a long reaction time, large equipment size, complex operation, low production efficiency, and there are problems such as uneven molecular weight distribution, large rheological viscosity, and easy yellowing. Different from nylon 66 salt, the bulk density of long-chain nylon salt is relatively small (0.2 g / cm 3 ) and it is insoluble in water. When directly using nylon salt for batch polymerization, the utilization rate of the reactor is less than 20% and there is a problem of very poor heating and mass transfer effect.

[0004] At the same time, in the prior art when polymerizing with long-chain nylon salt, the long-chain nylon salt solid is directly heated. The melting point of the long-chain nylon salt solid is high and it needs to be melted at a relatively high temperature and pressure, and it is not easy to be stably stored. Therefore, only batch production can be adopted, with low output and continuous production cannot be carried out.

[0005] Therefore, it is necessary to study a method for continuously preparing long-chain nylon, which can improve the quality of long-chain nylon while increasing the output, and at the same time the process is more stable and controllable. Summary of the Invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a method and system for continuously preparing long-chain nylon and the obtained long-chain nylon.

[0007] In order to overcome the problems in the prior art that the reaction for preparing long-chain nylon requires a long time, large equipment size, complex operation, low production efficiency, and there are problems such as uneven molecular weight distribution and serious oxidation, the present invention proposes a method for continuously preparing long-chain nylon. It includes preheating long-chain nylon salt and water in a molten salt kettle to obtain a nylon salt solution, stabilizing it through an intermediate tank and then continuously adding it to a prepolymerization reactor for prepolymerization reaction to obtain a prepolymer, removing a large amount of water through a flash evaporator and then adding it to a final polycondensation reactor to remove the final moisture and increase the molecular weight, and obtaining excellent-performance long-chain nylon after pelletizing and drying.

[0008] The present invention utilizes the characteristic that long-chain nylon salt can be melted below its melting point in the presence of water. The nylon salt and water are pre-melted at a relatively low temperature (about 40 °C lower than the melting point) and stored stably under a relatively low pressure. Through stable treatment in an intermediate tank, the molten nylon salt solution can be continuously supplied to a prepolymerization reactor, thereby realizing the continuous production of long-chain nylon. Continuous production can not only improve production efficiency but also make production more stable, avoiding the disadvantages of the prior art, such as directly heating, polymerizing, and degassing in a reaction kettle, resulting in poor mass transfer and heat transfer effects after the viscosity increases later, and the molecular weight and distribution are more controllable.

[0009] One of the objectives of the present invention is to provide a method for continuously preparing long-chain nylon, including: mixing raw materials including long-chain nylon salt and water, heating and melting to obtain an aqueous nylon salt solution, followed by stable treatment, then raising the temperature for prepolymerization reaction to obtain a prepolymer, and finally obtaining the long-chain nylon through flash evaporation, gas-liquid separation, and final polymerization followed by post-treatment of the product.

[0010] In a preferred embodiment of the present invention,

[0011] The long-chain nylon salt is prepared from a diamine and a diacid; preferably,

[0012] The diamine is at least one of C5-C20 diamines, more preferably at least one of C6-C14 diamines; for example, diamines of C6, C7, C8, C9, C10, C11, C12, C13, C14;

[0013] The diacid is at least one of C5-C20 diacids; more preferably at least one of C10-C14 diacids; for example, diacids of C10, C11, C12, C13, C14;

[0014] The molar ratio of the diacid to the diamine is 1:(1-1.05), preferably 1:(1-1.01).

[0015] In a preferred embodiment of the present invention,

[0016] The heating and melting temperature is 120-160 °C;

[0017] The heating and melting pressure is 0.1-0.5 MPa;

[0018] The heating and melting time is 0.5-2.0 h;

[0019] The stable treatment temperature is 120-160 °C;

[0020] The stable treatment pressure is 0.1-0.5 MPa;

[0021] The stable treatment time is 0.5 to 3.0 h.

[0022] In a preferred embodiment of the present invention,

[0023] The long-chain nylon salt is prepared by the following method steps:

[0024] a) Mix the dibasic acid with solvent A and heat-treat to obtain solution A;

[0025] b) Mix the diamine with solvent B and heat-treat to obtain solution B;

[0026] c) Add solution B to solution A, carry out the reaction and adjust the pH;

[0027] d) Filter, wash and dry the mixed material to obtain nylon salt solid.

[0028] In a preferred embodiment of the present invention,

[0029] In step a),

[0030] The solvent A is at least one of methanol, ethanol and propanol;

[0031] The weight ratio of the dibasic acid to solvent A is 1:(2 - 10), preferably 1:(4 - 10); heat to 50 - 95 °C and keep for 10 - 50 min;

[0032] In step b),

[0033] The solvent B is at least one of methanol, ethanol and propanol;

[0034] The weight ratio of the diamine to solvent B is 1:(1 - 6);

[0035] Heat to 40 - 90 °C and keep for 10 - 50 min;

[0036] In step c),

[0037] Solution B is added to solution A by a feeding pump;

[0038] The feeding time is 0.2 - 2.0 h;

[0039] After feeding, continue the reaction for 0.2 - 4 h, and the reaction temperature is 50 - 100 °C;

[0040] The pH is adjusted to 6.5 - 7.5;

[0041] In step d), the solvent content of the nylon salt solid is less than 0.5%.

[0042] In a preferred embodiment of the present invention,

[0043] The raw materials including long-chain nylon salt and water are heated and melted in a molten salt kettle; and / or,

[0044] The stabilization treatment is carried out in an intermediate tank; and / or,

[0045] The temperature increase is carried out in a preheater; and / or,

[0046] The prepolymerization reaction is carried out in a prepolymerization reactor; and / or,

[0047] The flash evaporation is carried out in a flash evaporator; and / or,

[0048] The gas-liquid separation is carried out in a gas-liquid separator; and / or,

[0049] The final polycondensation is carried out in a final polycondensation reactor; and / or,

[0050] The post-treatment includes pelletizing and drying.

[0051] In a preferred embodiment of the present invention,

[0052] The method for continuously preparing long-chain nylon includes:

[0053] (1) Adding raw materials including long-chain nylon salt, water, catalyst, and molecular weight regulator into a molten salt kettle, mixing evenly, and then heating and melting to obtain a nylon salt solution; preferably, the raw materials further include an antioxidant;

[0054] (2) Putting the nylon salt solution obtained in step (1) into an intermediate tank for stabilization treatment;

[0055] (3) Heating and flashing the stabilized nylon salt solution obtained in step (2) in a preheater, then continuously adding it into a prepolymerization reactor for prepolymerization reaction to obtain a prepolymer, and discharging part of the water vapor to remove part of the water; the prepolymerization reactor keeps the pressure constant, and discharging part of the water vapor can achieve the removal of part of the water;

[0056] (4) Heating and flashing the prepolymer obtained in step (3) in a flash evaporator, reducing it to atmospheric pressure, discharging the water vapor to remove a large amount of water, and then carrying out gas-liquid separation in a gas-liquid separator to obtain nylon oligomers; the water content of the nylon oligomers after water removal is less;

[0057] (5) Carrying out final polycondensation reaction on the nylon oligomers obtained in step (4), dehydrating, pelletizing, and drying to obtain the long-chain nylon.

[0058] In a preferred embodiment of the present invention,

[0059] In step (1),

[0060] The catalyst is at least one of phosphoric acid, phosphorous acid, hypophosphorous acid, sodium phosphite, and sodium hypophosphite;

[0061] The molecular weight regulator is at least one of monocarboxylic acid, dicarboxylic acid, monoamine, and diamine; the dicarboxylic acid is preferably a C10-C14 dicarboxylic acid;

[0062] The antioxidant is at least one of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, antioxidant 1790, antioxidant 3114, antioxidant 1010, and antioxidant 1098;

[0063] The amount of water used is 20-100 wt% of the long-chain nylon salt;

[0064] The amount of the catalyst used is 0.05-0.5 wt% of the long-chain nylon salt;

[0065] The amount of the molecular weight regulator used is 0.05-1.0 wt% of the long-chain nylon salt;

[0066] The amount of the antioxidant used is 0.05-0.5 wt% of the long-chain nylon salt;

[0067] The heating temperature is 120-160 °C;

[0068] The pressure is 0.1-0.5 MPa;

[0069] The heating time is 0.5-2.0 h;

[0070] In step (2),

[0071] The stabilization treatment temperature of the intermediate tank is 120-160 °C;

[0072] The stabilization treatment pressure of the intermediate tank is 0.1-0.5 MPa;

[0073] The stabilization treatment time in the intermediate tank is 0.5-3.0 h;

[0074] In step (3),

[0075] The preheater raises the temperature of the material to 180-220 °C;

[0076] The prepolymerization reaction temperature gradually increases from 180-220 °C to 200-260 °C;

[0077] The prepolymerization reaction pressure is 1.0-2.0 MPa;

[0078] The prepolymerization reaction time is 0.5-3.0 h;

[0079] In step (4),

[0080] The pressure in the flash evaporator drops to atmospheric pressure;

[0081] The heating temperature rises from 200 - 260 °C to 220 - 260 °C;

[0082] The heating time is 3 - 60 s;

[0083] The temperature of the gas - liquid separator is 220 - 260 °C;

[0084] The residence time in the gas - liquid separator is 10 - 60 min;

[0085] In step (5),

[0086] The temperature of the final polymerization reaction is 220 - 260 °C;

[0087] The final polymerization pressure is from a vacuum of 0.08 MPa to atmospheric pressure;

[0088] The final polymerization reaction time is 0.1 - 2.0 h.

[0089] The second object of the present invention is to provide a system for continuously preparing long - chain nylon, including a molten salt kettle, an intermediate tank, a pre - heater, a pre - polymerization reactor, a flash evaporator, a gas - liquid separator and a final polymerization reactor; the molten salt kettle, the intermediate tank, the pre - heater, the pre - polymerization reactor, the flash evaporator, the gas - liquid separator and the final polymerization reactor are connected in sequence.

[0090] The pre - polymerization reactor can adopt reactors commonly used in the prior art, such as tubular reactors, etc., and the final polymerization reactor can adopt reactors commonly used in the prior art, such as self - cleaning reactors, etc.

[0091] The third object of the present invention is to provide a long - chain nylon prepared by the above - mentioned method for continuously preparing long - chain nylon or the above - mentioned system.

[0092] Compared with the prior art, the beneficial effects of the present invention:

[0093] The melting point of long - chain nylon salt is relatively high, and it is not easy to stably maintain its molten state. Long - chain nylon in the prior art is usually produced in batches, which requires a long time, large equipment size, complex operation, and low production efficiency. Since the processes of heating, polymerization, and gas release are directly carried out in the reaction kettle, the mass transfer and heat transfer effects are poor after the viscosity increases in the later stage, and there are problems such as uneven molecular weight distribution and serious oxidation.

[0094] The present invention utilizes the characteristic that long-chain nylon salt can be melted below its melting point in the presence of water. The nylon salt and water are pre-melted at a relatively low temperature (about 40°C lower than the melting point) and stored stably under a relatively low pressure. Through stable treatment in an intermediate tank, the molten nylon salt solution can be continuously supplied to a prepolymerization reactor, thereby realizing the continuous production of long-chain nylon. Continuous production can not only improve production efficiency, but also make the production more stable, and the molecular weight and its distribution are more controllable.

[0095] Compared with the batch method, the long-chain nylon prepared by the continuous method of the present invention has a narrower molecular weight distribution and better mechanical properties. Moreover, due to the continuity of the entire production process, the materials continuously enter and exit the device, with basically no residue, less crosslinking and oxidation, and more excellent fluidity and color. Brief Description of the Drawings

[0096] Figure 1 It is a schematic diagram of the system for continuously preparing long-chain nylon of the present invention;

[0097] Among them, 1 - molten salt kettle; 2 - intermediate tank; 3 - preheater; 4 - prepolymerization reactor; 5 - flash evaporator; 6 - gas-liquid separator; 7 - final polymerization reactor. Detailed Embodiments

[0098] The present invention will be specifically described below in conjunction with specific drawings and embodiments. It is necessary to point out here that the following embodiments are only used for further illustration of the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0099] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0100] The raw materials used in the examples and comparative examples, if not specifically defined, are those disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0101] Testing Methods:

[0102] When testing the strength performance, it is first necessary to injection-mold nylon particles into standard specimens. The injection molding equipment includes large injection molding machines and small precision injection molding machines. Since the amount of nylon 1212 prepared by the 2L polymerization kettle is small, a precision injection molding machine is selected, and the injection temperature is selected at 220°C. Two types of standard specimens are prepared. Dumbbell-shaped specimens are used to test the tensile performance, and long-strip standard specimens are used to test the impact and bending performance.

[0103] The tensile performance test adopts the standard GB / T 1040.1-2006 / ISO 527-1:1993, Determination of tensile properties of plastics - Part 1: General principles.

[0104] The test principle is to stretch the specimen at a constant speed along the longitudinal main axis until fracture or the stress (load) or strain (elongation) reaches a certain predetermined value, and measure the load and elongation borne by the specimen during this process.

[0105] The impact performance test adopts the standard GB / T 1043.1-2008 / ISO 179:2000, Determination of Charpy impact strength of plastics - Part 1: Non-instrumented impact test.

[0106] The test principle is that the pendulum is raised to a fixed height and impacts the specimen supported as a horizontal beam at a constant speed once, and the impact line is located at the midpoint between the two supports. When the notched specimen is impacted laterally, the impact line is directly opposite the single notch.

[0107] The molecular weight is tested by the GPC method, using Waters991. The solvent and mobile phase are hexafluoroisopropanol. The column temperature is 40°C, the injection volume is 200μm, the eluent flow rate is 1.0ml / min, and the RI2410 differential refractive index detector is used. The standard sample is nylon 6, and the data is processed by the Waters820 GPC workstation.

[0108] The chromaticity test is carried out in accordance with the standard GB / T 39822-2021, Determination of the yellowness index and its change value of plastics; The test instrument uses the HunterLab UItraScan VIS near-infrared and ultraviolet colorimeter. According to the spectral tristimulus values obtained from the test, the yellowness index is calculated, which can represent the oxidation degree of the nylon sample.

[0109] The rheological viscosity is tested by high-temperature rheological testing, using the Anton Paar advanced rotational rheometer MCR302 to test the variation law of the rheological viscosity with the rotational shear rate under high-temperature conditions.

[0110] Such as Figure 1As shown in the figure, the system for continuously preparing long-chain nylon includes a molten salt kettle (1), an intermediate tank (2), a preheater (3), a prepolymerization reactor (4), a flash evaporator (5), a gas-liquid separator (6) and a final polymerization reactor (7); the molten salt kettle, the intermediate tank, the preheater, the prepolymerization reactor, the flash evaporator, the gas-liquid separator and the final polymerization reactor are connected in sequence. The long-chain nylon salt and water are melted in the molten salt kettle (1), preferably including a catalyst, a molecular weight regulator and an antioxidant, to obtain a long-chain nylon salt solution, which is stabilized in the intermediate tank (2), continuously heated by the preheater (3) and then enters the prepolymerization reactor (4) for prepolymerization, and most of the water vapor is released. The prepolymer continuously enters the flash evaporator (5) for flashing to release part of the water vapor, and after gas-liquid separation by the gas-liquid separator (6), it continuously enters the final polymerization reactor (7) for final polymerization reaction to obtain long-chain nylon, while releasing water vapor.

[0111]

Example 1

[0112] 1. Nylon salt formation: (1) Add 274.2 kg (1.19 kmol) of dodecanedioic acid and 1100 kg of ethanol to the neutralization kettle, heat to 75 °C for dissolution, and keep for 30 minutes; (2) Add 240.4 kg (1.20 kmol) of dodecanediamine and 240 kg of ethanol to the dissolution kettle, heat to 60 °C for dissolution, and keep for 30 minutes; (3) Pump all the dodecanediamine ethanol solution into the neutralization kettle through a feeding pump, with a feeding time of 1.0 h, react while stirring, control the reaction temperature at 78 °C, continue to react for 1.0 hour after adding the material, adjust the pH of the reaction solution to 7.0 by adding dodecanedioic acid or dodecanediamine, cool the neutralization kettle to make the temperature drop below 30 °C, filter the nylon salt solution through a filter, and dry it in a drying oven to obtain nylon 1212 salt solid, and the solvent content of the nylon 1212 salt solid is less than 0.1%.

[0113] 2. Pre-melting of nylon salt: (1) Mix 500 kg of nylon 1212 salt, 250 kg of water, 500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator dodecanedioic acid, and 500 g of antioxidant 1010 evenly and then add them to a 3 m 3 pre-melting kettle; (2) Rapidly heat up to 140 °C, 0.2 MPa and stir to melt to obtain a nylon salt aqueous solution, heat and stabilize for a total of 1.0 h; (3) Quickly put the nylon salt solution into the intermediate tank for stabilization, with a temperature of 140 °C, a pressure of 0.2 MPa, and a stabilization time of 1.0 h.

[0114] 3. Prepolymerization of nylon 1212: Heat the nylon salt solution stabilized in the intermediate tank to 180 °C through a preheater, and then continuously add it to a tubular reactor for prepolymerization reaction and remove part of the water to obtain a prepolymer, where the reaction temperature gradually rises from 180 °C to 200 °C, the pressure remains unchanged at 1.4 MPa, and the residence time is 1.0 h.

[0115] 4. Flash evaporation: The nylon 1212 oligomer at the outlet of the tubular reactor is pumped into the flash evaporator by a melt pump for heating and flash evaporation, so that the temperature of the oligomer rises from 200 °C to 240 °C, the flash evaporation time is 10 s, the outlet of the flash evaporator is connected to a gas-liquid separator, the gas phase is discharged and collected at atmospheric pressure as water vapor, the liquid phase is the nylon 1212 oligomer, the temperature of the gas-liquid separator is 240 °C, and the residence time is 20 min;

[0116] 5. Continuous final polymerization of nylon 1212 in a self-cleaning reactor: (1) Continuously discharge the nylon 1212 oligomer at the outlet of the flash evaporator into a 200 L self-cleaning reactor through a melt pump; (2) The reaction temperature is 240 °C, the residence time of the oligomer melt in the reactor is 1.0 hour, final polymerization is carried out under atmospheric pressure to remove water, and after discharging and extruding by a screw, it is cooled, pelletized, and dried to obtain nylon 1212 products.

[0117]

Example 2

[0118] 1. The nylon salt formation step is the same as that in Example 1;

[0119] 2. Pre-melting of nylon salt: (1) Mix 500 kg of nylon 1212 salt with 250 kg of water, 500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator dodecanedioic acid, and 500 g of antioxidant 1010 evenly, and then add them to a 3 m 3 pre-melting kettle; (2) Rapidly heat up to 120 °C and 0.1 MPa and stir to melt to obtain an aqueous nylon salt solution, heat and stabilize for a total of 2.0 h; (3) Quickly put the nylon salt solution into an intermediate tank for stabilization, the temperature is 120 °C, the pressure is 0.1 MPa, and the stabilization time is 3.0 h.

[0120] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0121] 4. The flash evaporation step is the same as that in Example 1;

[0122] 5. The continuous final polymerization step of nylon 1212 in a self-cleaning reactor is the same as that in Example 1.

[0123]

Example 3

[0124] 1. The nylon salt formation step is the same as that in Example 1;

[0125] 2. Pre-melting of nylon salt: (1) Mix 500 kg of nylon 1212 salt with 250 kg of water, 500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator dodecanedioic acid, and 500 g of antioxidant 1010 evenly, and then add them to a 3 m 3Pre-melting kettle; (2) Rapidly heat up to 160°C and 0.5 MPa and stir to melt to obtain a nylon brine solution, heat and stabilize for a total of 0.5 h; (3) Rapidly place the nylon salt solution into an intermediate tank for stabilization, with a temperature of 160°C, a pressure of 0.5 MPa, and a stabilization time of 0.5 h.

[0126] 3. The pre-polymerization step of nylon 1212 is the same as that in Example 1;

[0127] 4. The flash evaporation step is the same as that in Example 1;

[0128] 5. The continuous final polymerization step of nylon 1212 in the self-cleaning reactor is the same as that in Example 1.

[0129]

Example 4

[0130] 1. Nylon salt formation: (1) Add 285.6 kg (1.24 kmol) of dodecanedioic acid and 1142 kg of ethanol to a neutralization kettle, heat to 75°C for dissolution, and hold for 30 minutes; (2) Add 215.4 kg (1.25 kmol) of decanediamine and 215 kg of ethanol to a dissolution kettle, heat to 60°C for dissolution, and hold for 30 minutes; (3) Pump all the decanediamine ethanol solution into the neutralization kettle through a feeding pump, with a feeding time of 1.0 h, react while stirring, control the reaction temperature at 78°C, continue to react for 1.0 hour after adding the material, adjust the pH of the reaction solution to 7.0 by adding dodecanedioic acid or decanediamine, cool the neutralization kettle to a temperature below 30°C, filter the nylon salt solution through a filter, and dry it in a drying oven to obtain nylon 1212 salt solid, and the solvent content of the nylon 1012 solid is less than 0.1%.

[0131] 2. Nylon salt pre-melting: (1) Mix 500 kg of nylon 1012 salt, 250 kg of water, 500 g of catalyst phosphorous acid, 500 g of molecular weight regulator dodecanedioic acid, and 500 g of antioxidant 1010 evenly and add them to a 3 m 3 Pre-melting kettle; (2) Rapidly heat up to 140°C and 0.2 MPa and stir to melt to obtain a nylon brine solution, heat and stabilize for a total of 1.0 h; (3) Rapidly place the nylon salt solution into an intermediate tank for stabilization, with a temperature of 140°C, a pressure of 0.2 MPa, and a stabilization time of 1.0 h.

[0132] 3. Nylon 1012 pre-polymerization: Heat the nylon salt solution stabilized in the intermediate tank to 180°C through a preheater, and then continuously add it to a tubular reactor for pre-polymerization reaction and remove part of the water to obtain a pre-polymer, where the reaction temperature gradually rises from 180°C to 200°C, the pressure remains unchanged at 1.4 MPa, and the residence time is 1.0 h.

[0133] 4. Flash evaporation: The nylon 1012 oligomer from the outlet of the tubular reactor is pumped into a flash evaporator by a melt pump for heating and flash evaporation, so that the temperature of the oligomer rises from 200 °C to 240 °C, the flash evaporation time is 20 s, the outlet of the flash evaporator is connected to a gas-liquid separator, the gas phase is discharged and collected at atmospheric pressure as water vapor, the liquid phase is nylon 1012 oligomer, the temperature of the gas-liquid separator is 240 °C, and the residence time is 20 min;

[0134] 5. Continuous final polymerization of nylon 1012 in a self-cleaning reactor: (1) The nylon 1012 oligomer from the outlet of the flash evaporator is continuously discharged into a 200 L self-cleaning reactor through a melt pump; (2) The reaction temperature is 240 °C, the residence time of the oligomer melt in the reactor is 0.1 h, vacuum is drawn to a vacuum degree of 0.05 MPa for final polymerization and water removal, and after discharging and extruding by a screw, it is cooled, pelletized, and dried to obtain nylon 1012 product.

[0135]

Example 5

[0136] 1. Nylon salification: (1) Add 317.5 kg (1.57 kmol) of sebacic acid and 1270 kg of ethanol to a neutralization kettle, heat to 75 °C for dissolution, and hold for 30 minutes; (2) Add 184.8 kg (1.59 kmol) of hexamethylenediamine and 370 kg of ethanol to a dissolution kettle, heat to 60 °C for dissolution, and hold for 30 minutes; (3) Pump all the hexamethylenediamine ethanol solution into the neutralization kettle through a feeding pump, the feeding time is 1.0 h, react while stirring, control the reaction temperature at 78 °C, continue to react for 1.0 h after adding the material, adjust the pH of the reaction solution to 7.0 by adding sebacic acid or hexamethylenediamine, cool the neutralization kettle to a temperature below 30 °C, filter the nylon salt solution through a filter, and dry it in a drying oven to obtain nylon 610 salt solid, and the solvent content of the nylon 610 salt solid is less than 0.1%.

[0137] 2. Pre-melting of nylon salt: (1) Mix 500 kg of nylon 610 salt, 250 kg of water, 500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator sebacic acid, and 500 g of antioxidant 1010 evenly and then add them to a 3 m 3 pre-melting kettle; (2) Rapidly heat up to 140 °C, 0.2 MPa and stir to melt to obtain a nylon salt aqueous solution, heat and stabilize for a total of 1.0 h; (3) Rapidly put the nylon salt solution into an intermediate tank for stabilization, the temperature is 140 °C, the pressure is 0.2 MPa, and the stabilization time is 1.0 h.

[0138] 3. Pre-polymerization of nylon 610: The nylon salt solution stabilized by the intermediate tank is heated to 200 °C by a preheater, and then continuously added to a tubular reactor for pre-polymerization reaction and partial water removal to obtain a pre-polymer, wherein the reaction temperature gradually rises from 200 °C to 240 °C, the pressure remains unchanged at 1.6 MPa, and the residence time is 1.0 h.

[0139] 4. Flash evaporation: The nylon 610 oligomer at the outlet of the tubular reactor is pumped into the flash evaporator by a melt pump for heating and flash evaporation, so that the temperature of the oligomer rises from 240 °C to 260 °C, the flash evaporation time is 3 s, the outlet of the flash evaporator is connected to a gas-liquid separator, the gas phase is discharged and collected at atmospheric pressure as water vapor, the liquid phase is the nylon 610 oligomer, the temperature of the gas-liquid separator is 260 °C, and the residence time is 10 min;

[0140] 5. Continuous final polymerization of nylon 610 in a self-cleaning reactor: (1) The nylon 610 oligomer at the outlet of the flash evaporator is continuously discharged into a 200 L self-cleaning reactor through a melt pump; (2) The reaction temperature is 260 °C, the residence time of the oligomer melt in the reactor is 1.0 hour, final polymerization is carried out under atmospheric pressure to remove moisture, and after being extruded by a discharging screw, it is cooled, pelletized, and dried to obtain nylon 610 products.

[0141]

Example 6

[0142] 1. Nylon salification: (1) Add 266.1 kg (1.03 kmol) of tetradecanedioic acid and 1330 kg of ethanol to the neutralization kettle, heat to 75 °C for dissolution, and hold for 30 minutes; (2) Add 237.6 kg (1.04 kmol) of tetradecanediamine and 240 kg of ethanol to the dissolution kettle, heat to 60 °C for dissolution, and hold for 30 minutes; (3) Pump all the tetradecanediamine ethanol solution into the neutralization kettle through a feeding pump, the feeding time is 1.0 h, react while stirring, control the reaction temperature at 78 °C, continue to react for 1.0 hour after adding the material, adjust the pH of the reaction solution to 7.0 by adding tetradecanedioic acid or tetradecanediamine, cool the neutralization kettle to make the temperature drop below 30 °C, filter the nylon salt solution through a filter, and dry it in a drying oven to obtain nylon 1414 salt solid, and the solvent content of the nylon 1414 salt solid is less than 0.1%.

[0143] 2. Pre-melting of nylon salt: (1) Mix 500 kg of nylon 1414 salt, 250 kg of water, 500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator tetradecanedioic acid, and 500 g of antioxidant 1098 evenly and then add them to a 3 m 3 pre-melting kettle; (2) Rapidly heat up to 140 °C, 0.2 MPa and stir to melt to obtain an aqueous nylon salt solution, heat and stabilize for a total of 1.0 h; (3) Quickly put the nylon salt solution into an intermediate tank for stabilization, the temperature is 140 °C, the pressure is 0.2 MPa, and the stabilization time is 1.0 h.

[0144] 3. Pre-polymerization of nylon 1414: The nylon salt solution stabilized by the intermediate tank is heated to 180 °C through a preheater, and then continuously added to a tubular reactor for pre-polymerization reaction to remove part of the moisture to obtain a prepolymer, wherein the reaction temperature gradually rises from 180 °C to 200 °C, the pressure remains unchanged at 1.4 MPa, and the residence time is 1.0 h.

[0145] 4. Flash evaporation: The nylon 1414 oligomer at the outlet of the tubular reactor is pumped into the flash evaporator by a melt pump for heating and flash evaporation, so that the temperature of the oligomer rises from 200 °C to 220 °C, the flash evaporation time is 60 s, the outlet of the flash evaporator is connected to a gas-liquid separator, the gas phase is discharged and collected at atmospheric pressure as water vapor, the liquid phase is the nylon 1414 oligomer, the temperature of the gas-liquid separator is 220 °C, and the residence time is 60 min;

[0146] 5. Continuous final polymerization of nylon 1414 in a self-cleaning reactor: (1) The nylon 1414 oligomer at the outlet of the flash evaporator is continuously discharged into a 200 L self-cleaning reactor through a melt pump; (2) The reaction temperature is 220 °C, the residence time of the oligomer melt in the reactor is 2.0 hours, final polymerization and water removal are carried out at atmospheric pressure, and after being extruded by a discharge screw, it is cooled, pelletized, and dried to obtain nylon 1414 products.

[0147]

Example 7

[0148] 1. Nylon salt formation: (1) 274.2 kg (1.19 kmol) of dodecanedioic acid and 2742 kg of methanol are added to the neutralization kettle, heated to 50 °C for dissolution, and kept for 50 minutes; (2) 240.4 kg (1.20 kmol) of dodecanediamine and 240 kg of methanol are added to the dissolution kettle, heated to 40 °C for dissolution, and kept for 50 minutes; (3) All the dodecanediamine methanol solution is pumped into the neutralization kettle by a feeding pump, the feeding time is 2.0 h, the reaction is carried out while stirring, the reaction temperature is controlled at 50 °C, and after the feeding is completed, the reaction continues for 4.0 hours. The pH of the reaction solution is adjusted to 6.5 by adding dodecanedioic acid or dodecanediamine. The neutralization kettle is cooled to a temperature below 30 °C, and the nylon salt solution is filtered through a filter and dried in an oven to obtain nylon 1212 salt solid, and the solvent content of the nylon 1212 salt solid is less than 0.5%.

[0149] 2. The nylon salt pre-melting step is the same as that in Example 1, and the nylon salt used is the nylon 1212 obtained in Example 7;

[0150] 3. The nylon 1212 pre-polymerization step is the same as that in Example 1;

[0151] 4. The flash evaporation step is the same as that in Example 1;

[0152] 5. The continuous final polymerization step of nylon 1212 in a self-cleaning reactor is the same as that in Example 1.

[0153]

Example 8

[0154] 1. Nylon salt formation: (1) Add 274.2 kg (1.19 kmol) of dodecanedioic acid and 1100 kg of ethanol to the neutralization kettle, heat to 95 °C for dissolution, and maintain for 10 minutes; (2) Add 240.4 kg (1.20 kmol) of dodecanediamine and 1442 kg of ethanol to the dissolution kettle, heat to 90 °C for dissolution, and maintain for 10 minutes; (3) Pump all the dodecanediamine ethanol solution into the neutralization kettle through a feeding pump, with a feeding time of 0.2 h, react while stirring, control the reaction temperature at 100 °C, continue to react for 0.2 h after feeding, adjust the pH of the reaction solution to 7.5 by adding dodecanedioic acid or dodecanediamine, cool the neutralization kettle to a temperature below 30 °C, filter the nylon salt solution through a filter, and dry it in a drying oven to obtain nylon 1212 salt solid, with the solvent content of the nylon 1212 solid being less than 0.2%.

[0155] 2. The nylon salt pre-melting step is the same as that in Example 1;

[0156] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0157] 4. The flash evaporation step is the same as that in Example 1;

[0158] 5. The continuous final polymerization step of nylon 1212 in the self-cleaning reactor is the same as that in Example 1.

[0159]

Example 9

[0160] 1. The nylon salt formation step is the same as that in Example 1;

[0161] 2. Nylon salt pre-melting: (1) Mix 500 kg of nylon 1212 salt, 100 kg of water, 500 g of catalyst sodium hypophosphite, 5000 g of molecular weight regulator dodecanedioic acid, and 500 g of antioxidant 1010 evenly, and then add them to a 3 m 3 pre-melting kettle; (2) Rapidly heat up to 140 °C and 0.2 MPa, stir and melt to obtain a nylon salt aqueous solution, heat and stabilize for a total of 1.0 h; (3) Quickly put the nylon salt solution into the intermediate tank for stabilization, with a temperature of 140 °C, a pressure of 0.2 MPa, and a stabilization time of 1.0 h.

[0162] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0163] 4. The flash evaporation step is the same as that in Example 1;

[0164] 5. The continuous final polymerization step of nylon 1212 in the self-cleaning reactor is the same as that in Example 1;

[0165]

Example 10

[0166] 1. The nylon salt formation step is the same as that in Example 1;

[0167] 2. Nylon Salt Premelting: (1) Mix 500 kg of nylon 1212 salt, 500 kg of water, 2500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator dodecanedioic acid, and 2500 g of antioxidant 1010 evenly, and then add them to a 3 m 3 premelting kettle; (2) Rapidly heat up to 140 °C and 0.2 MPa, and stir and melt to obtain an aqueous nylon salt solution, and heat and stabilize for a total of 1.0 h; (3) Rapidly put the nylon salt solution into an intermediate tank for stabilization, with a temperature of 140 °C, a pressure of 0.2 MPa, and a stabilization time of 1.0 h.

[0168] 3. The prepolymerization step of nylon 1212 is the same as that in Example 1;

[0169] 4. The flash evaporation step is the same as that in Example 1;

[0170] 5. The continuous final polymerization step of nylon 1212 in a self-cleaning reactor is the same as that in Example 1;

[0171]

Comparative Example 1

[0172] 1. The nylon salt formation step is the same as that in Example 1;

[0173] 2. Batch polymerization of nylon 1212: (1) Mix 500 kg of nylon 1212 salt, 250 kg of water, 500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator dodecanedioic acid, and 500 g of antioxidant 1010 evenly, and then add them to a 3 m 3 prepolymerization kettle; (2) Rapidly heat up to 200 °C and 1.4 MPa, stir and maintain the pressure, for a total of 2.0 h; (3) Maintain at 200 °C and 1.4 MPa, and continuously release water vapor, for a total of 1.0 h; (4) Continue to gradually heat up to 240 °C, and continuously release water vapor to reduce the pressure to atmospheric pressure, and the pressure reduction process takes a total of 2.0 h; (5) Carry out a final polycondensation reaction at 240 °C and atmospheric pressure for 2.0 hours, extrude after filling with nitrogen, cool and pelletize, and dry to obtain nylon 1212 products.

[0174]

Comparative Example 2

[0175] 1. The nylon salt formation step is the same as that in Example 1;

[0176] 2. Nylon Salt Premelting: (1) Mix 500 kg of nylon 1212 salt, 250 kg of water, 500 g of catalyst sodium hypophosphite, 500 g of molecular weight regulator dodecanedioic acid, and 500 g of antioxidant 1010 evenly, and then add them to a 3 m 3 premelting kettle; (2) Rapidly heat up to 180 °C and 1.4 MPa, stir and maintain the pressure, and heat for a total of 2.0 h;

[0177] 3. Prepolymerization of Nylon 1212: The nylon 1212 salt solution in the prepolymerization kettle is continuously added to a tubular reactor for prepolymerization reaction and partial water removal to obtain a prepolymer. The reaction temperature gradually increases from 180 °C to 200 °C, the pressure remains constant at 1.4 MPa, and the residence time is 1.0 h.

[0178] 4. The flash evaporation step is the same as in Example 1;

[0179] 5. The continuous final polymerization step of nylon 1212 in the self-cleaning reactor is the same as in Example 1.

[0180] The performances of Examples 1 - 10 and Comparative Examples 1 - 2 were tested, and the test results are listed in Table 1. In Examples 1 - 10, within the scope of the claims, by changing the melting temperature, stabilization temperature and time, changing the variety of long-chain nylon, changing the polymerization process, changing the salting process, changing the raw material ratio and additives, the continuous polymerization of long-chain nylon can be well implemented, and the prepared nylon has excellent properties.

[0181] Table 1 Performance test results of Examples 1 - 10 and Comparative Examples 1 - 2

[0182]

[0183] Compared with Example 1, in Comparative Example 1, batch operation is adopted, and the nylon 1212 brine solution is directly heated to 200 °C for reaction; compared with Example 1, in Comparative Example 2, the nylon 1212 brine solution is reacted after heating at 180 °C and 1.4 MPa for 2.0 h.

[0184] Compared with Comparative Examples 1 - 2, the molecular weight distribution of Example 1 is narrower, the mechanical properties are better, and the yellowness index is lower, which proves that the nylon obtained by using the continuous production method of long-chain nylon of the present invention has better properties than the batch method of Comparative Example 1 and lower oxidation degree. In Comparative Example 2, without stabilization treatment, it is not easy to achieve continuous operation, and the properties of the obtained nylon are also inferior to those of Example 1. The molecular weight distribution of the long-chain nylon obtained in Example 1 is more uniform and the oxidation degree is lower.

[0185] The long-chain nylon prepared in Examples 1 - 10 has a narrower molecular weight distribution and better mechanical properties; and because the whole production process is continuous, the materials continuously enter and exit the device, with basically no residue, less cross-linking and oxidation, and better fluidity and color.

Claims

1. A method for continuously preparing long-chain nylon, comprising: Mixing raw materials including long-chain nylon salt and water, heating and melting to obtain an aqueous nylon salt solution, then performing a stabilization treatment, and then raising the temperature to carry out a prepolymerization reaction to obtain a prepolymer, and then obtaining the product through flash evaporation, gas-liquid separation, and final polymerization, followed by post-treatment to obtain the long-chain nylon.

2. The method for continuously preparing long-chain nylon according to claim 1, wherein: The long-chain nylon salt is prepared from a diamine and a diacid; preferably, The diamine is at least one of diamines having 5 to 20 carbon atoms, more preferably at least one of diamines having 6 to 14 carbon atoms; and / or, The diacid is at least one of diacids having 5 to 20 carbon atoms, more preferably at least one of diacids having 10 to 14 carbon atoms; and / or, The molar ratio of the diacid to the diamine is 1:(1 to 1.05), preferably 1:(1 to 1.01).

3. The method for continuously preparing long-chain nylon according to claim 1, wherein: The heating and melting temperature is 120 to 160 °C; and / or, The heating and melting pressure is 0.1 to 0.5 MPa; and / or, The heating and melting time is 0.5 to 2.0 h; and / or, The stabilization treatment temperature is 120 to 160 °C; and / or, The stabilization treatment pressure is 0.1 to 0.5 MPa; and / or, The stabilization treatment time is 0.5 to 3.0 h.

4. The method for continuously preparing long-chain nylon according to claim 2, wherein: The long-chain nylon salt is prepared by the method of the following steps: a) Mixing the diacid with solvent A, heating and treating to obtain solution A; b) Mixing the diamine with solvent B, heating and treating to obtain solution B; c) Adding solution B to solution A, reacting and adjusting the pH; d) Filtering, washing, and drying the mixed material to obtain a nylon salt solid.

5. The method for continuously preparing long-chain nylon according to claim 4, wherein: In step a), Solvent A is at least one of methanol, ethanol, and propanol; and / or, The weight ratio of the diacid to solvent A is 1:(2 to 10), preferably 1:(4 to 10); and / or, heating to 50 to 95 °C and maintaining for 10 to 50 min; and / or, In step b), Solvent B is at least one of methanol, ethanol, and propanol; and / or, The weight ratio of the diamine to solvent B is 1:(1 to 6); and / or, Heating to 40 to 90 °C and maintaining for 10 to 50 min; and / or, In step c), Solution B is added to solution A using a metering pump; and / or, The feeding time is 0.2 to 2.0 h; and / or, After feeding, continue to react for 0.2 to 4 h, and the reaction temperature is 50 to 100 °C; and / or, Adjust the pH to 6.5 to 7.5; In step d), the solvent content of the nylon salt solid is less than 0.5%.

6. The method for continuously preparing long-chain nylon according to claim 1, wherein: The raw materials including long-chain nylon salt and water are heated and melted in a molten salt kettle; and / or, The stabilization treatment is carried out in an intermediate tank; and / or, The temperature increase is carried out in a preheater; and / or, The prepolymerization reaction is carried out in a prepolymerization reactor; and / or, The flash evaporation is carried out in a flash evaporator; and / or, The gas-liquid separation is carried out in a gas-liquid separator; and / or, The final polycondensation is carried out in a final polycondensation reactor; and / or, The post-treatment includes pelletizing and drying.

7. The method for continuously preparing long-chain nylon according to claim 6, characterized in that: (1) Raw materials including long-chain nylon salt, water, catalyst, and molecular weight regulator are added to a molten salt kettle, mixed evenly, and then heated and melted to obtain a nylon salt solution; preferably, the raw materials further include an antioxidant; (2) The nylon salt solution obtained in step (1) is put into an intermediate tank for stabilization treatment; (3) The stabilized nylon salt solution obtained in step (2) is heated and raised in temperature in a preheater and then continuously added to a prepolymerization reactor for prepolymerization reaction to obtain a prepolymer, and part of the water vapor is released; (4) The prepolymer obtained in step (3) is heated and flash-evaporated in a flash evaporator, and the pressure is reduced to atmospheric pressure to release water vapor to remove a large amount of water, and a nylon oligomer is obtained after gas-liquid separation in a gas-liquid separator; (5) The nylon oligomer obtained in step (4) is subjected to a final polymerization reaction in a final polymerization reactor, and after dehydration, pelletizing, and drying, the long-chain nylon is obtained.

8. The method for continuously preparing long-chain nylon according to claim 7, characterized in that: In step (1), the catalyst is at least one of phosphoric acid, phosphorous acid, hypophosphorous acid, sodium phosphite, and sodium hypophosphite; and / or, the molecular weight regulator is at least one of monocarboxylic acid, dicarboxylic acid, monoamine, and diamine; the dicarboxylic acid is preferably a dicarboxylic acid with 10 to 14 carbon atoms; and / or, the antioxidant is at least one of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, antioxidant 1790, antioxidant 3114, antioxidant 1010, and antioxidant 1098; and / or, the amount of water used is 20 to 100 wt% of the long-chain nylon salt; and / or, the amount of the catalyst used is 0.05 to 0.5 wt% of the long-chain nylon salt; and / or, the amount of the molecular weight regulator used is 0.05 to 1.0 wt% of the long-chain nylon salt; and / or, the amount of the antioxidant used is 0.05 to 0.5 wt% of the long-chain nylon salt; and / or, the heating temperature is 120 to 160 °C; and / or, the pressure is 0.1 to 0.5 MPa; and / or, the heating time is 0.5 to 2.0 h; and / or, In step (2), the stabilization treatment temperature of the intermediate tank is 120 to 160 °C; and / or, the stabilization treatment pressure of the intermediate tank is 0.1 to 0.5 MPa; and / or, the stabilization treatment time in the intermediate tank is 0.5 to 3.0 h; and / or, In step (3), the preheater raises the material temperature to 180 to 220 °C; and / or, the prepolymerization reaction temperature gradually rises from 180 to 220 °C to 200 to 260 °C; and / or, the prepolymerization reaction pressure is 1.0 to 2.0 MPa; and / or, the prepolymerization reaction time is 0.5 to 3.0 h; and / or, In step (4), the pressure in the flash evaporator is reduced to atmospheric pressure; and / or, The heating temperature is raised from 200 - 260°C to 220 - 260°C; and / or, The heating time is 3 - 60 s; and / or, The temperature of the gas-liquid separator is 220 - 260°C; and / or, The residence time in the gas-liquid separator is 10 - 60 min; and / or, In step (5), The temperature of the final polymerization reaction is 220 - 260°C; and / or, The final polymerization pressure is a vacuum of 0.08 MPa to atmospheric pressure; and / or, The final polymerization reaction time is 0.1 - 2.0 h.

9. A system for continuously preparing long-chain nylon by the method according to any one of claims 1 - 8, comprising a molten salt kettle, an intermediate tank, a preheater, a prepolymerization reactor, a flash evaporator, a gas-liquid separator, and a final polymerization reactor; the molten salt kettle, the intermediate tank, the preheater, the prepolymerization reactor, the flash evaporator, the gas-liquid separator, and the final polymerization reactor are connected in sequence.

10. A long-chain nylon prepared by the method according to any one of claims 1 - 8 or by using the system according to claim 9.

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