Continuous polymerization reaction method and system for aliphatic nylon and product thereof

Abstract

The invention provides a continuous polymerization reaction method and system for aliphatic nylon and application, and mainly solves the problems of small process scale, long retention time, low intermittent production efficiency and incapability of reaching commercial production scale in the prior art. By adopting the technical steps of raw material preparation, continuous salification, separation and drying, continuous polymerization, pelletizing, drying and packaging, solvent recovery, tail gas absorption and the like, commercial continuous industrial production with the nominal scale of hundreds of tons to hundreds of thousands of tons is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nylon materials, and particularly relates to a continuous polymerization reaction method and system of aliphatic nylon and aliphatic nylon obtained by the method. BACKGROUND

[0002] PA612 belongs to a kind of high-end aliphatic nylon, has good flexibility and transparency, low water absorption, small density, dimensional stability, high impact resistance, good flowability, and can be widely applied to the fields of automobile, electronic and electrical product parts injection molding, etc. Due to the complex production process route, multiple synthesis steps and harsh reaction conditions of aliphatic nylon, the industrial production technology of aliphatic nylon has been monopolized by multinational suppliers for a long time. The existing domestic technology has small scale and adopts intermittent process production, and the product performance is obviously different from that of imported products.

[0003] The industrial production of nylon mainly includes two core sections of salt formation reaction and polymerization reaction. The salt formation technology is generally divided into water phase salt formation and solvent salt formation method, and the water phase salt formation uses water as the solvent, and its characteristic is that no organic solvent is used. The short-chain nylon is mainly produced by water phase salt formation in industry. For example, the application CN117000163A discloses a nylon production device and production method, and nylon 66 salt is obtained by reacting hexanediamine aqueous solution with adipic acid. The application CN112778517B discloses a continuous production method of long-chain nylon 1018 salt, and nylon 1018 salt is obtained by reacting octadecanedioic acid, decanediamine and water. The water phase salt formation method is convenient and easy to operate, safe and reliable, simple in process and low in cost, but the quality of raw materials intermediates is required to be high. With the increase of carbon number, the solubility of diacid, diamine and nylon salt in water gradually decreases. And the purity of common biological method diacid raw material on the market is not high enough, and the impurities in the water phase salt formation method cannot be separated in the system all the time, and the impurities will affect the polymerization process.

[0004] In industry, there are intermittent and continuous polycondensation methods for preparing nylon. The intermittent polymerization process has the advantages of simple operation, flexible control and easy product modification, but the production efficiency is low and the batch stability is poor. The domestic existing long-chain nylon industrialization device mainly adopts the intermittent polymerization method, while international scale enterprises, such as DuPont and EMS, adopt the continuous polymerization method, and the quality of domestic long-chain nylon products is quite different from that of imported products. The continuous polymerization process has the advantages of high production efficiency and high uniformity, but the equipment selection and process technology threshold are high. The development of the continuous polymerization process is of great significance for industrial scale-up, reduction of production investment cost, provision of product stability and competitiveness. SUMMARY

[0005] The present application relates to a kind of long carbon chain polyamide continuous polymerization reaction method, mainly solve the process scale small, long residence time, intermittent production efficiency low, cannot reach the problem of commercial production scale in prior art.Using the system and method of the application, by raw material preparation, continuous salting, separation and drying, continuous polymerization, granulation drying packaging, solvent recovery, tail gas absorption and other technical steps, it realizes the nominal scale hundred tons-ten million tons commercialization continuous industrial production.

[0006] One of the purposes of the present application is to provide a kind of aliphatic nylon continuous polymerization reaction method, including the step of reacting the components including long carbon chain diacid and diamine (I) into salt, separation and drying, polymerization, wherein, after reaction into salt, still need to add diamine (II) for secondary reaction.

[0007] According to the present application, the aliphatic nylon continuous polymerization reaction method specifically includes the following steps:

[0008] (a) adding diamine (I) to long carbon chain diacid solution for salting reaction, to obtain nylon salt slurry A;

[0009] (b) adding diamine (II) to the nylon salt slurry A obtained in step (a), to obtain nylon salt slurry B after secondary reaction;

[0010] (c) solid-liquid separation and drying of nylon salt slurry B to obtain nylon salt, then adding water to obtain nylon salt slurry C;

[0011] (d) adding additive to nylon salt slurry C for polymerization reaction, dehydration to obtain the aliphatic nylon;Preferably, the polymerization reaction includes pre-polymerization, pre-polymerization and final polymerization in turn.

[0012] According to the embodiments of the present application, in the aliphatic nylon continuous polymerization reaction method:

[0013] The general formula of the long carbon chain diacid is HOOC-R-COOH, R is C8-C18 straight chain or branched alkylene, preferably, R is straight chain or branched alkylene with 8-16 carbon atoms in the main chain;For example, the long carbon chain diacid is selected from at least one of decanoic diacid (sebacic acid), undecanoic diacid, dodecanoic diacid, tridecanoic diacid, tetradecanoic diacid;

[0014] The diamine (I) and diamine (II) are the same or different, and are independently selected from at least one of C4-C14 aliphatic diamine, preferably at least one of C6-C12 aliphatic diamine;For example, the diamine (I) or diamine (II) is selected from at least one of hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine;

[0015] The additive includes a molecular weight regulator, optionally includes an antioxidant and / or a chain extender; preferably, the molecular weight regulator is selected from at least one of benzoic acid, acetic acid, aliphatic thiol compounds, polyphenol, amine compounds, more preferably at least one of benzoic acid, acetic acid, hexanediamine; the antioxidant and the chain extender can be the antioxidant and the chain extender commonly used in the prior art, specifically, the antioxidant is selected from at least one of hindered phenolic antioxidant, phosphite antioxidant (for example, antioxidant 1098, antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 264, etc.); the chain extender is selected from at least one of epoxy functional chain extender, imidazolyl chain extender, carbonate functional chain extender, for example, ECO-1120, PBO, isophthaloyl bis-caprolactam (IBC), etc.

[0016] According to the embodiment of the present application, in the continuous polymerization reaction method of the aliphatic nylon, step (a) is as follows:

[0017] The solvent in the long carbon chain dibasic acid solution is selected from at least one of ethanol, water;

[0018] The concentration of the long carbon chain dibasic acid in the long carbon chain dibasic acid solution is 10-80wt%, preferably 10-30wt%;

[0019] The molar ratio of the long carbon chain dibasic acid to the dibasic amine (I) in the long carbon chain dibasic acid solution is 1:1-1:1.1, preferably 1:1-1:1.05;

[0020] The dibasic amine (I) can be directly added or a dibasic amine (I) solution can be added; adding the dibasic amine (I) in the form of a solution can reduce the reactant concentration to slow down the reaction rate and control the reaction uniformity; the solvent in the dibasic amine (I) solution is selected from at least one of ethanol, water, and the addition amount of the solvent is not particularly limited; preferably, the concentration of the dibasic amine (I) in the dibasic amine (I) solution is 20-95wt%, further preferably 50-80wt%;

[0021] The conditions of the salt formation reaction are as follows: the reaction pressure is 0-0.1MPaG, the temperature is 65-80℃, and the reaction residence time is 2-4 hours.

[0022] According to the embodiment of the present application, in the continuous polymerization reaction method of the aliphatic nylon, step (b) is as follows:

[0023] Diamine (II) is added to adjust the pH of the slurry to 7.0-7.2; the diamine (II) can be added directly or in a diamine (II) solution; the solvent in the diamine (II) solution is selected from at least one of ethanol and water, and the amount of solvent added is not particularly limited. Preferably, the concentration of diamine (II) in the diamine (II) solution is 20-95 wt%, more preferably 50-80 wt%.

[0024] The reaction conditions are: reaction temperature of 70-80℃ and reaction residence time of 1-2 hours.

[0025] During the salt-forming reaction, the concentrations of long-chain diacids and diamines (Ⅰ) are relatively high. This may result in unreacted raw materials being trapped in the resulting nylon salt slurry A (coarse salt slurry). This invention incorporates a secondary reaction (refining salt reaction) step, using the addition of diamine (Ⅱ) to precisely control the reaction endpoint and adjust the slurry pH to 7.0–7.2. This allows for more precise control of the complete reaction of the long-chain diacids and diamines, resulting in more accurate control of the raw material ratios. It also avoids excess monomer affecting subsequent continuous polymerization processes, thus improving the quality of the nylon product. Without the secondary reaction step, the resulting nylon salt may contain an excess of a certain component, affecting the molecular weight of the polymer during polymerization. Furthermore, for continuously operating equipment, this invention employs a two-step reaction process of salt formation and secondary reaction. Adding diamine after the salt formation reaction allows for more effective and stable pH adjustment of the solution, better control of continuous reactions and equipment operation, and offers the advantages of convenient and flexible salt formation and high-quality products.

[0026] According to an embodiment of the present invention, in step (c) of the continuous polymerization method for aliphatic nylon:

[0027] The separation can be achieved using common solid-liquid separation methods in the prior art, such as centrifugation, filtration, membrane separation, and extraction. The appropriate method can be selected based on the particle size of the nylon salt obtained.

[0028] The drying process can employ commonly used drying methods in the prior art, such as at least one of fluidized bed drying, spray drying, vacuum drying, drum drying, and infrared drying. Specifically, the drying conditions are: a drying temperature of 70–120°C, preferably 80–100°C; and a moisture content of less than 1000 ppm for the nylon salt after drying.

[0029] In the nylon salt slurry C, it is preferable to use demineralized water to fully dissolve the nylon salt. The amount of demineralized water is not particularly limited, as long as it is sufficient to fully dissolve the nylon salt. For example, in the nylon salt slurry C, the content of nylon salt is 30-90 wt%, preferably 50-90 wt%.

[0030] According to an embodiment of the present invention, in step (d) of the continuous polymerization method for aliphatic nylon:

[0031] Based on 100 wt% of the nylon salt slurry C, the amount of the additive is 0.1-1.0 wt%, preferably 0.1-0.5 wt%. The additive includes a molecular weight regulator and optionally includes an antioxidant and / or a chain extender. The molecular weight regulator is selected from at least one of benzoic acid, acetic acid, aliphatic thiols, polyphenols, and amines, preferably from at least one of benzoic acid, acetic acid, and hexamethylenediamine. The antioxidant is selected from at least one of hindered phenolic antioxidants and phosphite antioxidants (e.g., antioxidant 1098, antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 264, etc.). The chain extender is selected from at least one of epoxy-functionalized chain extenders, oximidazolium chain extenders, and carbonate-functionalized chain extenders, for example, ECO-1120, PBO, and isophthaloyl biscaprolactam (IBC).

[0032] According to an embodiment of the present invention, in step (d) of the continuous polymerization method for aliphatic nylon:

[0033] The conditions for the prepolymerization reaction are: reaction pressure of 1.5-1.8 MPaG, temperature of 180-210℃, and reaction residence time of 2-5 hours;

[0034] The conditions for the prepolymerization reaction are: reaction pressure of 0-0.1 MPaG, temperature of 180-220℃, and reaction residence time of 1-4 hours;

[0035] The conditions for the final polymerization reaction are: reaction pressure of 20-60 kPaA, temperature of 220-280℃, and reaction residence time of 0.5-3 hours;

[0036] In step (d), after adding the additive to the nylon salt slurry C, flash concentration is optionally performed. To avoid the influence of the moisture content of the polymerization raw materials on the polymerization reaction, flash concentration can be performed beforehand to reduce excessive water entering the polymerization reaction. After flash concentration, the nylon salt content in the slurry can be controlled at 70–95 wt%. The flash-concentrated nylon salt slurry is then preheated to 180–210°C, and then prepolymerization, prepolymerization, and final polymerization are carried out sequentially.

[0037] A second objective of this invention is to provide a continuous polymerization reaction system for aliphatic nylon, used to continuously prepare aliphatic nylon by implementing the above-mentioned continuous polymerization reaction method for aliphatic nylon.

[0038] According to the present invention, the continuous polymerization reaction system for aliphatic nylon includes a salt formation reaction unit, a secondary reaction unit, a separation unit, a drying unit, and a polymerization reaction unit connected sequentially by pipelines. The polymerization reaction unit includes a prepolymerization reactor, a prepolymerization reactor, and a final polymerization reactor; the system may also optionally include a solvent recovery unit and a tail gas absorption unit.

[0039] A third objective of this invention is to provide aliphatic nylon prepared by the above-mentioned continuous polymerization reaction method or continuous polymerization reaction system for aliphatic nylon.

[0040] Compared with the prior art, the present invention has the following technical effects:

[0041] (1) The batching of dicarboxylic acid and diamine was optimized to continuous feeding, which shortened the residence time, reduced the number of equipment, and reduced the size of the equipment by 10 times;

[0042] (2) The continuous solvent salt formation + separation and drying process is adopted, which results in higher product purity and fewer impurities compared with the existing aqueous phase salt formation technology;

[0043] (3) A continuous polymerization process is adopted, in which the salt solution passes through prepolymerization, prepolymerization and final polymerization in sequence to obtain aliphatic nylon; compared with the existing batch polymerization process, the equipment investment is small, the product stability is high, and it is conducive to industrial scale-up.

[0044] (4) Set up a solvent recovery system to recover and reuse solvents, thereby reducing unit consumption;

[0045] (5) An exhaust gas absorption system is installed, and the exhaust gas is treated to meet emission standards, which is environmentally friendly;

[0046] (6) It can continuously and industrially produce high-quality aliphatic nylon products with high production efficiency, low equipment investment, and guaranteed product performance. It is conducive to further industrial scale-up and can achieve commercial continuous industrial production of nominal scale of hundreds of tons to hundreds of thousands of tons.

[0047] (7) The system and method provided by the present invention can be applied to the production of the same type of solvent-based nylon products. Attached Figure Description

[0048] Figure 1 This is a flowchart of the continuous polymerization reaction of aliphatic nylon used in an embodiment of the present invention. The crude salt reaction is the salt-forming reaction, and the refined salt reaction is the secondary reaction. Detailed Implementation

[0049] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection 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 are still within the scope of protection of the present invention.

[0050] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0051] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0052] To better understand the present invention, the present invention will be further described below with reference to the embodiments. The following embodiments are only for illustration and not for limiting the present invention.

[0053] According to a preferred embodiment of the present invention, the continuous polymerization reaction method for aliphatic nylon provided by the present invention includes the following steps:

[0054] (1) Raw material preparation: The long-chain dicarboxylic acid is dissolved in the solvent according to the set solvent ratio by a solid continuous feeding method, and the mixture is uniform to obtain a long-chain dicarboxylic acid solution; the diamine (I) is optionally mixed with the solvent to obtain a diamine (I) solution;

[0055] (2) Continuous salt formation: Under the action of a stirrer, the obtained long-chain dicarboxylic acid solution and diamine (I) or diamine (I) solution are continuously added to the salt formation reactor to obtain nylon salt slurry A;

[0056] (3) The crude nylon salt slurry and diamine (II) solution are sent to a secondary reactor to further control the reaction precision. The reaction endpoint is adjusted by adjusting the amount of diamine (II) added to obtain nylon salt slurry B.

[0057] (4) Separation and drying: Nylon salt slurry B is separated into solid and liquid and dried to obtain nylon salt powder;

[0058] (5) Continuous polymerization: Nylon salt powder is dissolved in water (preferably demineralized water) to form nylon salt slurry C, which is mixed with additives, concentrated by flash evaporation and preheated under pressure, and then subjected to prepolymerization reaction, prepolymerization reaction and final polymerization reaction in sequence to obtain the aliphatic nylon.

[0059] (6) Pelletizing, drying and packaging: Aliphatic nylon is pelletized, dried and packaged to obtain nylon products;

[0060] (7) Solvent recovery: The solvent separated from nylon salt slurry B enters the solvent recovery system, and after purification, it is returned to the raw material preparation unit for recycling.

[0061] (8) Tail gas absorption: Waste gas from each section of the unit is sent to the tail gas absorption system and discharged after treatment to meet the standards.

[0062] According to a preferred embodiment of the present invention, the continuous polymerization reaction system for aliphatic nylon provided by the present invention includes a salt formation reaction unit, a secondary reaction unit, a separation unit, a drying unit, and a polymerization reaction unit connected sequentially by pipelines. The polymerization reaction unit includes a prepolymerization reactor, a prepolymerization reactor, and a final polymerization reactor; the system may also optionally include a solvent recovery unit and a tail gas absorption unit, for solvent recovery and reuse and tail gas treatment, respectively.

[0063] The testing instruments used in this embodiment are as follows:

[0064] Table 1

[0065]

[0066] Examples and comparative examples:

[0067] This embodiment illustrates the continuous polymerization reaction method for aliphatic nylon of the present invention.

[0068] Example 1

[0069] The following is combined with Figure 1 This describes the continuous polymerization production process of aliphatic nylon PA612 provided in Example 1.

[0070] include:

[0071] (1) Raw material preparation: Ethanol was used as the solvent, and dodecanoic acid and hexamethylenediamine were used as raw materials. The concentration of dodecanoic acid in the dodecanoic acid solution was 20 wt%, and the concentration of hexamethylenediamine in the hexamethylenediamine solution was 50 wt%.

[0072] (2) Continuous salt formation: The obtained dodecanoic acid solution and hexamethylenediamine solution are continuously added to the salt formation reactor under the action of a stirrer (reaction temperature is 70℃, residence time is 2 hours) (molar ratio of dodecanoic acid and hexamethylenediamine is 1:1) to obtain crude nylon salt slurry;

[0073] (3) Secondary reaction: The crude nylon salt slurry and hexamethylenediamine solution are sent to a secondary reactor (reaction temperature is 70℃, residence time is 1.5 hours) to further control the reaction precision. The reaction endpoint is adjusted to pH=7.0 by adjusting the amount of hexamethylenediamine solution added to obtain refined nylon salt slurry;

[0074] (4) Separation and drying: Nylon salt slurry is separated by pressure filtration and vacuum dried (80℃) to obtain nylon salt powder. The nylon salt yield is 98%.

[0075] (5) Continuous polymerization: Nylon salt powder is dissolved in water at 60°C to form a nylon salt solution with a nylon salt concentration of 50 wt%. The amount of benzoic acid additive added is 0.35 wt% of the nylon salt. The nylon salt solution and the additive are mixed and concentrated by flash evaporation (the concentration of the nylon salt solution is 85 wt%) and preheated to 180°C under pressure. Then, the prepolymerization reaction (reaction pressure is 1.8 MPaG, temperature is 180°C, residence time is 3 hours), the prepolymerization reaction (reaction pressure is 0.05 MPaG, temperature is 200°C, residence time is 2 hours), and the final polymerization reaction (reaction pressure is 60 kPaA, temperature is 240°C, residence time is 1 hour) are carried out sequentially to obtain an aliphatic nylon slurry.

[0076] (6) Pelletizing, drying and packaging: The aliphatic nylon slurry was pelletized, dried and packaged to obtain nylon products. The obtained nylon had a relative viscosity of 2.40, a number-average molecular weight of 16293 and a molecular weight distribution index of 2.09. The nylon properties were tested and met the product specifications. The test results are shown in Table 2.

[0077] (7) Solvent recovery: The solvent separated from the nylon salt enters the solvent recovery system, and after purification, it is returned to the raw material preparation unit for recycling.

[0078] (8) Tail gas absorption: Waste gas from each section of the unit is sent to the tail gas absorption system and discharged after treatment to meet the standards.

[0079] Example 2

[0080] The continuous salt-forming steps (1) to (4) of Example 1 were used. The difference was that the concentration of dodecanoic acid in the dodecanoic acid solution in step (1) was 10 wt%, and the yield of nylon salt obtained was 92.5%.

[0081] Example 3

[0082] The continuous polymerization steps of Example 1 were used, except that the final polymerization temperature in step (5) was changed to 250°C, and the relative viscosity of the nylon product obtained was 2.43.

[0083] Example 4

[0084] The continuous polymerization steps of Example 1 were adopted, except that the concentration of nylon salt in the nylon salt solution in step (5) was changed to 75%, the nylon salt was in slurry form, the heat load of the flash evaporator was reduced by 20%, the product performance met the requirements, and the relative viscosity of the obtained nylon product was 2.43.

[0085] Example 5

[0086] The continuous polymerization steps of Example 1 were used, except that the amount of benzoic acid added in step (5) was changed to 0.28% of the mass of nylon salt, and the relative viscosity of the nylon product obtained was 2.44.

[0087] Example 6

[0088] The continuous polymerization steps of Example 1 were used, except that the additive benzoic acid in step (5) was replaced with hexamethylenediamine. The resulting nylon product had a relative viscosity of 2.40, a number-average molecular weight of 11753, and a molecular weight distribution index of 1.78.

[0089] Comparative Example 1

[0090] The difference from Example 1 is that the secondary reaction step (3) is omitted, resulting in a PA612 product with discoloration and a tensile strength of 28 MPa, which is unqualified (the requirement is ≥55 MPa). Furthermore, the solvent obtained in the separation section has a high impurity content, leading to a heavy load on the separation system.

[0091] Comparative Example 2

[0092] The difference from Example 1 is that step (5) adopts an intermittent polymerization method. Nylon salt slurry is intermittently added to the reactor, and the pressure is increased, depressurized and vacuumed in a reactor in sequence. The resulting nylon product has a water content of 5% and a relative viscosity of 2.2, which is unqualified (PA612 product specifications require a relative viscosity of 2.4+0.05 and a water content of ≤0.06%).

[0093] Comparative Example 3

[0094] The difference from Example 1 is that no additives are added in step (5). The resulting nylon product has a relative viscosity of 2.3 and a molecular weight distribution index of 2.48, which is unqualified (PA612 product specifications require a relative viscosity of 2.4 + 0.05).

[0095] Performance testing

[0096] Tables 2 and 3 list the performance test results of the nylon products obtained from the above embodiments and comparative examples.

[0097] Table 2

[0098]

[0099] Table 3

[0100]

[0101] As can be seen from the performance test results of the nylon products in Tables 2-3, in the continuous polymerization preparation process of aliphatic nylon, the present invention can prepare nylon products with excellent performance by adopting a two-stage reaction step and adding a molecular weight regulator.

Claims

1. A continuous polymerization method for aliphatic nylon, comprising the steps of reacting components including a long-chain diacid and a diamine (Ⅰ) to form a salt, separating and drying, and polymerization, wherein, After the reaction of salt formation, a secondary reaction is carried out by adding a diamine (II).

2. The method of claim 1, wherein, Specifically comprising the following steps: (a) adding a diamine (I) to a long carbon chain dibasic acid solution to carry out a salt formation reaction, to obtain a nylon salt slurry A; (b) adding a diamine (II) to the nylon salt slurry A obtained in step (a) to carry out a secondary reaction to obtain a nylon salt slurry B; (c) carrying out a solid-liquid separation and drying on the nylon salt slurry B to obtain a nylon salt, and then adding water to obtain a nylon salt slurry C; (d) adding an additive to the nylon salt slurry C to carry out a polymerization reaction and dehydration to obtain the aliphatic nylon; preferably, the polymerization reaction comprises a prepolymerization reaction, a pre-polymerization reaction and a final polymerization reaction in sequence.

3. The method according to claim 2, wherein, the long carbon chain dibasic acid has a general formula of HOOC-R-COOH, R is a linear or branched alkylene group with 8-18 carbon atoms, preferably, R is a linear or branched alkylene group with 8-16 carbon atoms in the main chain; and / or, the diamine (I) and the diamine (II) are the same or different, and are independently selected from at least one of C4-C14 aliphatic diamines, preferably at least one of C6-C12 aliphatic diamines; and / or, the additive comprises a molecular weight regulator, and optionally comprises an antioxidant and / or a chain extender; preferably, the molecular weight regulator is selected from at least one of benzoic acid, acetic acid, aliphatic thiol compounds, polyphenol compounds and amine compounds, more preferably at least one of benzoic acid, acetic acid and hexanediamine; and / or, the antioxidant is selected from at least one of hindered phenolic antioxidants and phosphite antioxidants; and / or, the chain extender is selected from at least one of epoxy functional chain extenders, imidazolyl chain extenders and carbonate functional chain extenders.

4. The method of claim 2, wherein, in the step (a), the solvent in the long carbon chain dibasic acid solution is selected from at least one of ethanol and water; and / or, the concentration of the long carbon chain dibasic acid in the long carbon chain dibasic acid solution is 10-80 wt%, preferably 10-30 wt%; and / or, the molar ratio of the long carbon chain dibasic acid to the diamine (I) in the long carbon chain dibasic acid solution is 1:1-1:1.1, preferably 1:1-1:1.05; and / or, the salt formation reaction is carried out under the conditions of a reaction pressure of 0-0.1 MPaG, a reaction temperature of 65-80℃ and a reaction residence time of 2-4 hours.

5. The method of claim 2, wherein, in the step (b), the diamine (II) is added to adjust the pH of the slurry to 7.0-7.2; and / or, the reaction is carried out under the conditions of a reaction temperature of 70-80℃ and a reaction residence time of 1-2 hours.

6. The method of claim 2, wherein, in the step (c), the drying is carried out under the conditions of a drying temperature of 70-120℃, preferably 80-100℃; and / or, the content of the nylon salt in the nylon salt slurry B is 30-90 wt%, preferably 50-90 wt%.

7. The method of claim 2, wherein, in the step (d), the amount of the additive is 0.1-1.0 wt% based on 100 wt% of the nylon salt slurry C, preferably 0.1-0.5 wt%; and / or, the pre-polymerization is carried out at a reaction pressure of 1.5-1.8 MPaG, a temperature of 180-210°C, and a reaction residence time of 2-5 hours; and / or the pre-polymerization is carried out at a reaction pressure of 0-0.1 MPaG, a temperature of 180-220°C, and a reaction residence time of 1-4 hours; and / or the final polymerization is carried out at a reaction pressure of 20-60 kPaA, a temperature of 220-280°C, and a reaction residence time of 0.5-3 hours.

8. A continuous polymerization system for aliphatic nylon, which is used to continuously produce aliphatic nylon by implementing the method of continuous polymerization of aliphatic nylon according to any one of claims 1-7.

9. The system of claim 8, wherein, The continuous polymerization system for aliphatic nylon comprises, in sequence, a salt formation unit, a secondary reaction unit, a separation unit, a drying unit, and a polymerization unit, which are connected by pipelines; preferably, the polymerization unit comprises a pre-polymerization reactor, a pre-polymerization reactor, and a final polymerization reactor; and / or, the system optionally further comprises a solvent recovery unit and a tail gas absorption unit.

10. Aliphatic nylon produced by the method of continuous polymerization of aliphatic nylon according to any one of claims 1-7 or the continuous polymerization system for aliphatic nylon according to any one of claims 8-9.

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