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

Abstract

The invention provides a method and a system for semi-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, heating and carrying out prepolymerization reaction to obtain a nylon oligomer, stabilizing the nylon oligomer, carrying out final polymerization to obtain a product, and carrying out post-treatment to obtain the long-carbon-chain nylon. The system comprises a molten salt kettle, a prepolymerization reaction kettle, an intermediate tank and a final polymerization reactor, the molten salt kettle, the pre-polymerization reaction kettle, the intermediate tank and the final polymerization reactor are connected in sequence. The method provided by the invention can realize semi-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 semi-continuously preparing long-chain nylon and the obtained long-chain nylon. Background Art

[0002] Long-chain nylons, such as nylon 1212, nylon 1012, etc., have characteristics such as low density, low water absorption, good dimensional stability, excellent solvent resistance, corrosion resistance, wear resistance, good fatigue resistance and low-temperature impact resistance, and good processing performance. They are mainly used in industries such as automobiles, electrical appliances, and machinery, such as coil skeletons, insulation layers of wires and cables, automobile fuel pipes, oil pressure system pipes, etc.

[0003] In the prior art, the method of producing long-chain nylon often uses an intermittent reaction kettle. The required reaction time is long, the equipment size is large, the production efficiency is low, and there are problems such as unstable batches and easy formation of black spots. Chinese invention patents CN102010506A and CN101880458A both use the intermittent method to produce nylon 1212, and all processes are carried out in the same polymerization kettle, and the time required before and after is relatively long. For long-chain nylon salts such as nylon 1212, the bulk density is small (0.2 g / cm 3 ) and insoluble in water. Directly using nylon salt for intermittent polymerization, the reactor utilization rate is less than 20% and there is very poor heating and mass transfer effect. And the melting point of the solid long-chain nylon salt is high. Directly heating it requires melting at a higher temperature and higher pressure, and it is difficult to carry out semi-continuous production.

[0004] Therefore, it is necessary to study a method for semi-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

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a method and system for semi-continuously preparing long-chain nylon and the obtained long-chain nylon.

[0006] The present invention proposes a method for semi-continuously preparing long-chain nylon, which overcomes the deficiencies of the prior art in preparing long-chain nylon, such as long reaction time, large equipment size, complex operation, low production efficiency, and uneven molecular weight distribution. This technology uses a pre-melting kettle to pre-melt nylon salt and water at a lower temperature, and then add them to a high-pressure reaction kettle for prepolymerization. After mixing and stabilizing in an intermediate tank, they are added to a continuous final polymerization reactor, and long-chain nylon products with excellent performance can be efficiently prepared.

[0007] The present invention adopts a semi - continuous preparation method, with a more stable and controllable process, and it is more convenient to adjust the production process according to the actual output. By adding a pre - melting kettle, the volume of the prepolymerization reactor can be significantly reduced. By adding an intermediate tank, the nylon prepolymer can be stabilized, which can maintain a fluid state and can be fed continuously or intermittently. The continuous discharge can supply the subsequent continuous final polymerization reactor. Through the final continuous final polymerization reactor, long - chain nylon products with more excellent performance can be prepared.

[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 lower temperature (about 40°C lower than the melting point), and after prepolymerization reaction, nylon oligomers are obtained. The nylon oligomers are low - viscosity melts, which are stabilized in the intermediate tank and then continuously supplied to the final polymerization reactor for continuous final polymerization reaction to obtain long - chain nylon.

[0009] One of the purposes of the present invention is to provide a semi - continuous method for 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, raising the temperature for prepolymerization reaction to obtain nylon oligomers, stabilizing the nylon oligomers, and then obtaining the long - chain nylon after post - treatment of the product through final polymerization.

[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 such as 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 such as 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 stabilization treatment temperature is 180 to 220 °C;

[0020] The stabilization treatment pressure is 0.1 to 0.5 MPa;

[0021] The stabilization treatment time is 0.5 to 2.0 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 perform heat treatment to obtain solution A;

[0025] b) Mix the diamine with solvent B and perform heat treatment 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 the 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 hold 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 hold for 10 - 50 min;

[0036] In step c),

[0037] Solution B is added to solution A using a metering pump;

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

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

[0040] Adjust the pH to 6.5 - 7.5;

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

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

[0043] Raw materials including long-chain nylon salt and water are heated and melted in a molten salt kettle;

[0044] The heating and prepolymerization reaction are carried out in a prepolymerization reactor;

[0045] The stabilization treatment is carried out in an intermediate tank;

[0046] The final polycondensation is carried out in a final polycondensation reactor;

[0047] The post-treatment includes pelletizing and drying.

[0048] In a preferred embodiment of the present invention,

[0049] (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;

[0050] (2) The nylon salt solution obtained in step (1) is heated in a prepolymerization reactor and then undergoes a prepolymerization reaction, and then the pressure is reduced and kept at a positive pressure to obtain a nylon oligomer, while discharging water vapor;

[0051] (3) The nylon oligomer obtained in step (2) is put into an intermediate tank for stabilization treatment;

[0052] (4) The stabilized nylon oligomer obtained in step (3) undergoes a final polymerization reaction in a final polymerization reactor, and after dehydration, pelletizing, and drying, the long-chain nylon is obtained.

[0053] In a preferred embodiment of the present invention,

[0054] In step (1),

[0055] The catalyst is at least one of phosphoric acid, phosphorous acid, hypophosphorous acid, sodium phosphite, and sodium hypophosphite;

[0056] 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;

[0057] The antioxidant is at least one of bis(2,4-dicumylphenyl)pentaerythritol diphosphite, antioxidant 1790, antioxidant 3114, antioxidant 1010, and antioxidant 1098;

[0058] The dosage of the water is 10-100 wt% of the long carbon chain nylon salt;

[0059] The dosage of the catalyst is 0.05-0.5 wt% of the long carbon chain nylon salt;

[0060] The dosage of the molecular weight regulator is 0.05-1.0 wt% of the long carbon chain nylon salt;

[0061] The dosage of the antioxidant is 0.05-0.5 wt% of the long carbon chain nylon salt;

[0062] The heating temperature is 120-160 °C;

[0063] The pressure is 0.1-0.5 MPa;

[0064] The heating time is 0.5-2.0 h;

[0065] In step (2),

[0066] The prepolymerization reaction temperature is 180-220 °C;

[0067] The prepolymerization reaction pressure is 0.8-2.0 MPa;

[0068] Finally, the positive pressure is maintained at 0.1-0.5 MPa;

[0069] The prepolymerization reaction time is 0.5-8 h;

[0070] In step (3),

[0071] The stabilization treatment temperature of the intermediate tank is 180-220 °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 0.5-2 h;

[0074] In step (4),

[0075] The final polymerization reaction temperature is 220-260 °C;

[0076] The final polymerization pressure is 0.08 MPa vacuum to atmospheric pressure;

[0077] The final polymerization reaction time is 0.1-2.0 h.

[0078] The second object of the present invention is to provide a semi-continuous system for preparing long carbon chain nylon, including a molten salt kettle, a prepolymerization reactor, an intermediate tank and a final polymerization reactor; the molten salt kettle, the prepolymerization reactor, the intermediate tank and the final polymerization reactor are connected in sequence.

[0079] A third object of the present invention is to provide a long-chain nylon prepared by the method or system for semi-continuously preparing long-chain nylon as described above.

[0080] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0081] The long-chain nylon in the prior art is usually produced in batches. The continuous production has low efficiency and uneven product molecular weight distribution; it takes a long time, the equipment size is large, and the operation is complex. Since the processes of heating, polymerization, and degassing 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.

[0082] 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 lower temperature (about 40 °C lower than the melting point). After pre-polymerizing the nylon salt and water in a prepolymerization reactor to obtain a nylon oligomer, the nylon oligomer is stably treated in an intermediate tank to make it in a fluid state, and can be continuously supplied to the final polymerization reactor to realize the semi-continuous production of long-chain nylon. The semi-continuous production can not only improve the production efficiency, but also make the production more stable, and the molecular weight and its distribution are more controllable.

[0083] 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; and because the whole production process is semi-continuous, there is basically no residue of materials, less cross-linking and oxidation, and better fluidity and color. Description of the Drawings

[0084] Figure 1 It is a schematic diagram of the system for semi-continuously preparing long-chain nylon of the present invention;

[0085] 1 - molten salt kettle; 2 - prepolymerization reactor; 3 - intermediate tank; 4 - final polymerization reactor. Detailed Embodiments

[0086] The present invention will be specifically described below with reference to specific drawings and embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot 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.

[0087] In the ranges disclosed herein, the endpoints and any values are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values and individual point values of each range, and between individual point values, they 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.

[0088] For the raw materials used in the examples and comparative examples, if not specifically defined, they are all disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0089] Testing method:

[0090] 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 standard specimens are prepared, the dumbbell-shaped specimen is used to test the tensile performance, and the long-strip standard specimen is used to test the impact and bending performance.

[0091] The tensile performance test is carried out according to the standard GB / T 1040.1-2006 / ISO 527-1:1993, Plastics - Determination of tensile properties - Part 1: General principles.

[0092] 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.

[0093] The impact performance test is carried out according to the standard GB / T 1043.1-2008 / ISO 179:2000, Plastics - Determination of Charpy impact strength - Part 1: Non-instrumented impact test.

[0094] 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.

[0095] The molecular weight is tested by the GPC method, using Waters991, with the solvent and mobile phase being hexafluoroisopropanol. The column temperature is 40 °C, the injection volume is 200 μm, the eluent flow rate is 1.0 ml / 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.

[0096] The chromaticity test is carried out according to the standard GB / T 2409-1980, Test method for yellow index 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 yellow index is calculated, which can represent the oxidation degree of the nylon sample.

[0097] 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.

[0098] Such as Figure 1As shown in the figure, the system for continuously preparing long-chain nylon includes a molten salt kettle (1), a prepolymerization reactor (2), an intermediate tank (3), and a final polymerization reactor (4); the molten salt kettle, the prepolymerization reactor, the intermediate tank, 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 also including a catalyst, a molecular weight regulator, and an antioxidant, to obtain a long-chain nylon salt solution, which enters the prepolymerization reactor (2) for prepolymerization and releases part of the water vapor. The obtained nylon oligomer enters the intermediate tank (3) for stabilization treatment and continuously enters the final polymerization reactor (4) for final polymerization reaction to obtain long-chain nylon, while releasing water vapor.

[0099]

Example 1

[0100] 1. Nylon salt formation: (1) Add 9000.5 g (39.1 mol) of dodecanedioic acid and 45000 g of ethanol to the neutralization kettle, heat to 75 °C for dissolution, and keep for 30 minutes; (2) Add 7914 g (39.5 mol) of dodecanediamine and 10000 g 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 a temperature below 30 °C, filter the nylon salt solution through a filter, and dry it in a drying oven to obtain solid nylon 1212 salt, and the solvent content of the solid nylon salt 1212 is less than 0.1%.

[0101] 2. Pre-melting of nylon salt: (1) Mix 12000 g of nylon 1212 salt, 6000 g of water, 12 g of catalyst sodium hypophosphite, 12 g of molecular weight regulator dodecanedioic acid, and 12 g of antioxidant 1010 evenly and add them to a 60 L molten salt kettle; (2) Rapidly heat up to 140 °C, 0.2 MPa and stir to melt to obtain an aqueous nylon salt solution, and the heating and melting time is 1.0 h;

[0102] 3. Prepolymerization of nylon 1212: (1) Rapidly add the nylon salt solution to a 30 L prepolymerization reactor; (2) Continue to heat up to 200 °C, the pressure in the kettle rises to 1.4 MPa, and keep this temperature and pressure for reaction for 1.0 hour; (3) Continuously release steam to keep the reaction temperature and pressure for reaction for 1.0 hour; (4) Keep the reaction temperature unchanged, reduce to 0.3 MPa, and keep for 2.0 hours to obtain nylon 1212 oligomer;

[0103] 4. Stabilization of nylon 1212 oligomer in the intermediate tank: Pump the nylon 1212 oligomer in the prepolymerization kettle into a 30 L intermediate tank with a melt pump, keep the temperature of the intermediate tank at 200 °C, the pressure at 0.3 MPa, and the time at 1.0 h;

[0104] 5. Continuous final polymerization of nylon 1212 in a self-cleaning reactor: (1) Continuously discharge the nylon 1212 oligomer in the intermediate tank into an 8L self-cleaning reactor through a melt pump, and maintain the liquid level at 50%; (2) The reaction temperature is 240°C, the residence time of the oligomer melt in the reactor is 1.0 hour, and water is removed under normal pressure for final polymerization. After discharging and extruding by a screw, it is cooled and pelletized to obtain nylon 1212 products.

[0105]

Example 2

[0106] 1. The nylon salt formation step is the same as that in Example 1;

[0107] 2. Pre-melting of nylon salt: (1) Mix 12000g of nylon 1212 salt, 6000g of water, 12g of catalyst sodium hypophosphite, 12g of molecular weight regulator dodecanedioic acid, and 12g of antioxidant 1010 evenly and then add them to a 60L molten salt kettle; (2) Rapidly heat up to 120°C, 0.1MPa and stir to melt to obtain a nylon salt aqueous solution, and the heating and melting time is 2.0h;

[0108] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0109] 4. Stabilization of the nylon 1212 oligomer intermediate tank: Pump the nylon 1212 oligomer in the prepolymerization kettle into a 30L intermediate tank through a melt pump, and maintain the temperature of the intermediate tank at 180°C, the pressure at 0.1MPa, and the time at 1.0h;

[0110] 5. The continuous final polymerization step of nylon 1212 in a self-cleaning reactor is the same as that in Example 1.

[0111]

Example 3

[0112] 1. The nylon salt formation step is the same as that in Example 1;

[0113] 2. Pre-melting of nylon salt: (1) Mix 12000g of nylon 1212 salt, 6000g of water, 12g of catalyst sodium hypophosphite, 12g of molecular weight regulator dodecanedioic acid, and 12g of antioxidant 1010 evenly and then add them to a 60L molten salt kettle; (2) Rapidly heat up to 160°C, 0.5MPa and stir to melt to obtain a nylon salt aqueous solution, and the heating and melting time is 0.5h;

[0114] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0115] 4. Stabilization of the nylon 1212 oligomer intermediate tank: Pump the nylon 1212 oligomer in the prepolymerization kettle into a 30L intermediate tank through a melt pump, and maintain the temperature of the intermediate tank at 220°C, the pressure at 0.5MPa, and the time at 0.5h;

[0116] 5. The continuous final polymerization step of nylon 1212 in a self-cleaning reactor is the same as that in Example 1.

[0117]

Example 4

[0118] 1. Nylon salt formation: (1) Add 9000.5 g (39.1 mol) of dodecanedioic acid and 45000 g of ethanol to a neutralization kettle, heat to 75 °C for dissolution, and maintain for 30 minutes; (2) Add 6806 g (39.5 mol) of decanediamine and 13000 g of ethanol to a dissolution kettle, heat to 60 °C for dissolution, and maintain 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 1012 salt solid, with the solvent content of nylon 1012 solid being less than 0.1%.

[0119] 2. Nylon salt pre-melting: (1) Mix 12000 g of nylon 1012 salt, 6000 g of water, 12 g of catalyst phosphorous acid, 12 g of molecular weight regulator dodecanedioic acid, and 12 g of antioxidant 1010 evenly and add them to a 60 L molten salt kettle; (2) Rapidly heat up to 140 °C and 0.2 MPa and stir to melt to obtain a nylon salt aqueous solution, with a heating and melting time of 1.0 h;

[0120] 3. Nylon 1012 prepolymerization: (1) Rapidly add the nylon salt solution to a 30 L prepolymerization reactor; (2) Continue to heat up to 200 °C, the pressure in the kettle rises to 1.4 MPa, maintain this temperature and pressure for reaction for 1.0 hour; (3) Continuously release steam to maintain the reaction temperature and pressure for reaction for 1.0 hour; (4) Keep the reaction temperature unchanged, reduce to 0.3 MPa for 2.0 hours to obtain nylon 1012 oligomer;

[0121] 4. Nylon 1012 oligomer intermediate tank stabilization: Pump the nylon 1012 oligomer in the prepolymerization kettle into a 30 L intermediate tank with a melt pump, maintain the temperature of the intermediate tank at 200 °C, the pressure at 0.3 MPa, and the time at 1.0 h;

[0122] 5. Nylon 1012 self-cleaning reactor continuous final polymerization: (1) Continuously discharge the nylon 1012 oligomer in the intermediate tank into an 8 L self-cleaning reactor through a melt pump, and maintain the liquid level at 50%; (2) The reaction temperature is 240 °C, the residence time of the oligomer melt in the reactor is 0.1 hour, and water is removed and finally polymerized at 0.05 MPa, and it is cooled and pelletized after being extruded by a discharging screw to obtain nylon 1012 product.

[0123]

Example 5

[0124] 1. Nylon salt formation: (1) Add 7908 g (39.1 mol) of sebacic acid and 45000 g of ethanol to the neutralization kettle, heat to 75 °C for dissolution, and maintain for 30 minutes; (2) Add 4590 g (39.5 mol) of hexamethylenediamine and 4600 g of ethanol to the dissolution kettle, heat to 60 °C for dissolution, and maintain for 30 minutes; (3) Pump all the hexamethylenediamine 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 feeding, 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. The solvent content of the nylon 610 salt solid is less than 0.1%.

[0125] 2. Nylon salt pre-melting: (1) Mix 12000 g of nylon 610 salt, 6000 g of water, 12 g of catalyst sodium hypophosphite, 12 g of molecular weight regulator sebacic acid, and 12 g of antioxidant 1010 evenly and add them to a 60 L molten salt kettle; (2) Rapidly heat up to 140 °C and 0.2 MPa and stir to melt to obtain an aqueous nylon salt solution, with a heating and melting time of 1.0 h.

[0126] 3. Nylon 610 prepolymerization: (1) Rapidly add the nylon salt solution to a 30 L prepolymerization reactor; (2) Continue to heat up to 200 °C, the pressure in the kettle rises to 1.4 MPa, and maintain this temperature and pressure for reaction for 1.0 hour; (3) Continuously release steam to maintain the reaction temperature and pressure for reaction for 1.0 hour; (4) Keep the reaction temperature unchanged, reduce to 0.3 MPa for 2.0 hours to obtain nylon 610 oligomer.

[0127] 4. Stabilization of nylon 610 oligomer in the intermediate tank: Pump the nylon 610 oligomer in the prepolymerization kettle into a 30 L intermediate tank with a melt pump, maintain the temperature of the intermediate tank at 200 °C, the pressure at 0.3 MPa, and the time at 1.0 h.

[0128] 5. Continuous final polymerization of nylon 610 in a self-cleaning reactor: (1) Continuously discharge the nylon 610 oligomer in the intermediate tank into an 8 L self-cleaning reactor through a melt pump, and maintain the liquid level at 50%; (2) The reaction temperature is 240 °C, and the residence time of the oligomer melt in the reactor is 1.0 hour. Remove water under normal pressure for final polymerization, extrude with a discharging screw and then cool and pelletize to obtain nylon 610 product.

[0129]

Example 6

[0130] 1. Nylon salt formation: (1) Add 10205 g (39.1 mol) of tetradecanedioic acid and 45000 g of ethanol to the neutralization kettle, heat to 75 °C for dissolution, and maintain for 30 minutes; (2) Add 8931 g (39.5 mol) of tetradecane diamine and 10000 g of ethanol to the dissolution kettle, heat to 60 °C for dissolution, and maintain for 30 minutes; (3) Pump all the tetradecane diamine ethanol solution into the neutralization kettle through a feeding pump. The feeding time is 1.0 h. React with stirring, control the reaction temperature at 78 °C. After feeding, continue to react for 1.0 hour. Adjust the pH of the reaction solution to 7.0 by adding tetradecanedioic acid or tetradecane diamine. Cool the neutralization kettle to below 30 °C. Filter the nylon salt solution through a filter, and dry it in a drying oven to obtain nylon 1414 salt solid. The solvent content of the nylon 1414 salt solid is less than 0.1%.

[0131] 2. Nylon salt pre-melting: (1) Mix 12000 g of nylon 1414 salt, 6000 g of water, 12 g of catalyst sodium hypophosphite, 12 g of molecular weight regulator tetradecanedioic acid, and 12 g of antioxidant 1098 evenly, and then add them to a 60 L molten salt kettle; (2) Quickly heat up to 140 °C and 0.2 MPa with stirring to obtain a nylon salt aqueous solution. The heating and melting time is 1.0 h.

[0132] 3. Nylon 1414 prepolymerization: (1) Quickly add the nylon salt solution to a 30 L prepolymerization reactor; (2) Continue to heat up to 180 °C, and the pressure in the kettle rises to 1.8 MPa. Maintain this temperature and pressure for reaction for 1.0 hour; (3) Continuously vent to maintain the reaction temperature and pressure for reaction for 1.0 hour; (4) Keep the reaction temperature unchanged, reduce to 0.3 MPa for 2.0 hours to obtain nylon 1414 oligomer.

[0133] 4. Nylon 1414 oligomer intermediate tank stabilization: Pump the nylon 1414 oligomer in the prepolymerization kettle into a 30 L intermediate tank with a melt pump, keep the temperature of the intermediate tank at 200 °C, the pressure at 0.3 MPa, and the time at 1.0 h.

[0134] 5. Nylon 1414 self-cleaning reactor continuous final polymerization: (1) Continuously discharge the nylon 1414 oligomer in the intermediate tank into an 8 L self-cleaning reactor through a melt pump, and keep the liquid level at 50%; (2) The reaction temperature is 220 °C, and the residence time of the oligomer melt in the reactor is 1.0 hour. Remove water under normal pressure for final polymerization. After discharging and extruding with a screw, cool and pelletize to obtain nylon 1414 product.

[0135]

Example 7

[0136] 1. Nylon salt formation: (1) Add 9000.5 g (39.1 mol) of dodecanedioic acid and 90005 g of methanol to a neutralization kettle, heat to 50 °C for dissolution, and maintain for 50 minutes; (2) Add 7914 g (39.5 mol) of dodecanediamine and 10000 g of methanol to a dissolution kettle, heat to 40 °C for dissolution, and maintain for 50 minutes; (3) Pump all the dodecanediamine methanol solution into the neutralization kettle through a feeding pump. The feeding time is 2.0 h. React while stirring, control the reaction temperature at 50 °C. After feeding, continue to react for 4.0 hours. Adjust the pH of the reaction solution to 6.5 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. The solvent content of the nylon 1212 salt solid is less than 0.5%;

[0137] 2. The nylon salt pre-melting step is the same as that in Example 1;

[0138] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0139] 4. The nylon 1212 oligomer intermediate tank stabilization step is the same as that in Example 1;

[0140] 5. The nylon 1212 self-cleaning reactor continuous final polymerization step is the same as that in Example 1;

[0141]

Example 8

[0142] 1. Nylon salt formation: (1) Add 9000.5 g (39.1 mol) of dodecanedioic acid and 45000 g of propanol to a neutralization kettle, heat to 95 °C for dissolution, and maintain for 10 minutes; (2) Add 7914 g (39.5 mol) of dodecanediamine and 47500 g of propanol to a dissolution kettle, heat to 90 °C for dissolution, and maintain for 10 minutes; (3) Pump all the dodecanediamine propanol solution into the neutralization kettle through a feeding pump. The feeding time is 0.2 h. React while stirring, control the reaction temperature at 100 °C. After feeding, continue to react for 0.2 hours. 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. The solvent content of the nylon 1212 salt solid is less than 0.2%;

[0143] 2. The nylon salt pre-melting step is the same as that in Example 1;

[0144] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0145] 4. The nylon 1212 oligomer intermediate tank stabilization step is the same as that in Example 1;

[0146] 5. The continuous final polymerization step of nylon 1212 in the self-cleaning reactor is the same as that in Example 1.

[0147]

Example 9

[0148] 1. The nylon salt formation step is the same as that in Example 1;

[0149] 2. Nylon salt premelting: (1) Mix 12000 g of nylon 1212 salt with 2000 g of water, 12 g of catalyst sodium hypophosphite, 120 g of molecular weight regulator dodecanedioic acid, and 12 g of antioxidant 1010 evenly, and then add them to a 60 L molten salt kettle; (2) Rapidly heat up to 140 °C and 0.2 MPa and stir to melt to obtain an aqueous nylon salt solution. The heating and melting time is 1.0 h;

[0150] 3. The prepolymerization step of nylon 1212 is the same as that in Example 1;

[0151] 4. The stabilization step of the nylon 1212 oligomer intermediate tank is the same as that in Example 1;

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

[0153]

Example 10

[0154] 1. The nylon salt formation step is the same as that in Example 1;

[0155] 2. Nylon salt premelting: (1) Mix 12000 g of nylon 1212 salt with 12000 g of water, 60 g of catalyst sodium hypophosphite, 12 g of molecular weight regulator dodecanedioic acid, and 60 g of antioxidant 1010 evenly, and then add them to a 60 L molten salt kettle; (2) Rapidly heat up to 140 °C and 0.2 MPa and stir to melt to obtain an aqueous nylon salt solution. The heating and melting time is 1.0 h;

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

[0157] 4. The stabilization step of the nylon 1212 oligomer intermediate tank 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]

Comparative Example 1

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

[0161] 2. Intermittent polymerization of nylon 1212: (1) Mix 12000 g of nylon 1212 salt with 6000 g of water, 12 g of catalyst sodium hypophosphite, 12 g of molecular weight regulator dodecanedioic acid, and 12 g of antioxidant 1010 evenly, and then add them to a 60 L 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) Keep at 200 °C and 1.4 MPa, and continuously discharge water vapor for a total of 1.0 h; (4) Continue to gradually heat up to 240 °C, and continuously discharge water vapor to reduce the pressure to atmospheric pressure. The pressure reduction process takes a total of 2.0 h; (5) Carry out the final polycondensation reaction at 240 °C and atmospheric pressure for 2.0 hours, extrude with nitrogen, cool and pelletize, and dry to obtain nylon 1212 products.

[0162]

Comparative Example 2

[0163] 1. The nylon salt formation step is the same as that in Example 1;

[0164] 2. The nylon salt pre-melting step is the same as that in Example 1;

[0165] 3. The nylon 1212 prepolymerization step is the same as that in Example 1;

[0166] 4. The prepolymer after the nylon 1212 prepolymerization is directly added to a self-cleaning reactor for final polymerization, and the final polymerization step is the same as that in Example 1.

[0167] The performances of Examples 1 to 10 and Comparative Examples 1 to 2 were tested, and the test results are listed in Table 1. In Examples 1 to 10, within the scope of the claims, by changing the melting temperature, stabilizing temperature and time, changing the variety of long-chain nylon, changing the polymerization process, changing the salt formation 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.

[0168] Table 1 Performance test results of Examples 1 to 10 and Comparative Examples 1 to 2

[0169]

[0170] Compared with Example 1, in Comparative Example 1, an intermittent operation was adopted, and the nylon 1212 aqueous solution was directly heated to 200 °C for reaction; compared with Example 1, in Comparative Example 2, the nylon 1212 prepolymer was directly added to a self-cleaning reactor for final polymerization without stabilization.

[0171] Compared with Comparative Examples 1 to 2, the molecular weight distribution of Example 1 is narrower, the mechanical properties are better, and the yellowness index is lower. It is proved that by using the method for semi-continuous production of long-chain nylon of the present invention, the properties of the obtained nylon are better than those of the intermittent method of Comparative Example 1, and the degree of oxidation is lower. 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 degree of oxidation is lower.

[0172] The long-chain nylon prepared in Examples 1 to 10 has a narrower molecular weight distribution and better mechanical properties; and because the whole production process is semi-continuous, there is basically no residue of the material, less cross-linking and oxidation, and better fluidity and color.

Claims

1. A method for semi - continuously preparing long - carbon - chain nylon, comprising: Mixing raw materials including long - carbon - chain nylon salt and water, heating and melting them to obtain an aqueous nylon salt solution, raising the temperature for prepolymerization reaction to obtain nylon oligomers, subjecting the nylon oligomers to stabilization treatment, and then performing post - treatment after final polymerization to obtain the long - carbon - chain nylon.

2. The method for semi - continuously preparing long - carbon - chain nylon according to claim 1, characterized in that: The long - carbon - chain nylon salt is prepared from a diamine and a diacid; preferably, The diamine is at least one of diamines with C5 - C20 carbon atoms, more preferably at least one of diamines with C6 - C14 carbon atoms; and / or, The diacid is at least one of diacids with C5 - C20 carbon atoms, more preferably at least one of diacids with C10 - C14 carbon atoms; and / or, The molar ratio of the diacid to the diamine is 1:(1 - 1.05), preferably 1:(1 - 1.01).

3. The method for semi - continuously preparing long - carbon - chain nylon according to claim 2, characterized in that: The heating and melting temperature is 120 - 160 °C; and / or, The heating and melting pressure is 0.1 - 0.5 MPa; and / or, The heating and melting time is 0.5 - 2.0 h; and / or, The stabilization treatment temperature is 180 - 220 °C; and / or, The stabilization treatment pressure is 0.1 - 0.5 MPa; and / or, The stabilization treatment time is 0.5 - 2.0 h.

4. The method for semi - continuously preparing long - carbon - chain nylon according to claim 2, characterized in that: The long - carbon - 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 materials to obtain nylon salt solid.

5. The method for semi - continuously preparing long - carbon - chain nylon according to claim 4, characterized in that: In step a), The 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 - 10), preferably 1:(4 - 10); and / or, Heating to 50 - 95 °C and maintaining for 10 - 50 min; and / or, In step b), The 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 - 6); and / or, Heating to 40 - 90 °C and maintaining for 10 - 50 min; and / or, In step c), Solution B is added to solution A using a feeding pump; and / or, The feeding time is 0.2 - 2.0 h; and / or, Continuing to react for 0.2 - 4 h after feeding, and the reaction temperature is 50 - 100 °C; and / or, Adjusting the pH to 6.5 - 7.5; In step d), the liquid content of the nylon salt solid is less than 0.5%.

6. The method for semi - continuously preparing long - carbon - chain nylon according to claim 1, characterized in that: The raw materials including long - carbon - chain nylon salt and water are heated and melted in a molten salt kettle; and / or, The heating and prepolymerization reactions are carried out in a prepolymerization reactor; and / or, The stabilization treatment is carried out in an intermediate tank; 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 semi-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 heated in a prepolymerization reactor and then undergoes a prepolymerization reaction, and then the pressure is reduced and maintained at a positive pressure to obtain a nylon oligomer, while discharging water vapor; (3) The nylon oligomer obtained in step (2) is put into an intermediate tank for stabilization treatment; (4) The stabilized nylon oligomer obtained in step (3) undergoes a final polycondensation reaction in a final polymerization reactor, and after dehydration, pelletizing, and drying, the long-chain nylon is obtained.

8. The method for semi-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 C10-C14 dicarboxylic acid; 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 10-100 wt% of the long-chain nylon salt; and / or, the amount of the catalyst used is 0.05-0.5 wt% of the long-chain nylon salt; and / or, the amount of the molecular weight regulator used is 0.05-1.0 wt% of the long-chain nylon salt; and / or, the amount of the antioxidant used is 0.05-0.5 wt% of the long-chain nylon salt; and / or, the heating temperature is 120-160 °C; and / or, the pressure is 0.1-0.5 MPa; and / or, the heating time is 0.5-2.0 h; and / or, In step (2), the prepolymerization reaction temperature is 180-220 °C; and / or, the prepolymerization reaction pressure is 0.8-2.0 MPa; and / or, the final positive pressure maintained is 0.1-0.5 MPa; and / or, the prepolymerization reaction time is 0.5-8 h; and / or, In step (3), the stabilization treatment temperature of the intermediate tank is 180-220 °C; and / or, the stabilization treatment pressure of the intermediate tank is 0.1-0.5 MPa; and / or, the stabilization treatment time in the intermediate tank is 0.5-2 h; and / or, In step (4), the final polycondensation reaction temperature is 220-260 °C; and / or, the final polycondensation pressure is 0.08 MPa vacuum to atmospheric pressure; and / or, the final polycondensation reaction time is 0.1-2.0 h.

9. A semi - continuous system for preparing long - chain nylon for the method according to any one of claims 1 to 8, comprising a molten salt kettle, a prepolymerization reactor, an intermediate tank and a final polymerization reactor; the molten salt kettle, the prepolymerization reactor, the intermediate tank 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 to 8 or the system according to claim 9.

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