One-step preparation of bio-based nylon 12 and its preparation method and application

Abstract

The present application discloses a one-step preparation of bio-based nylon 12 and its preparation method and application, belonging to the technical field of polyamide materials. The method comprises the following steps: (1) material preparation: mixing bio-based 12-aminododecanoic acid, water and reaction aids in a material preparation tank to form a suspension; (2) feeding: adding the suspension to a polymerization kettle by nitrogen pressurization; (3) polymerization: performing the following operations in sequence through a control system: temperature and pressure increase, constant temperature and pressure maintenance, temperature and pressure reduction, constant temperature and pressure, constant temperature and vacuum, nitrogen pressurization, water cooling and pelletizing to obtain bio-based nylon 12. The present application achieves a one-step process for polymerizing nylon 12 using bio-based 12-aminododecanoic acid as a monomer by comprehensive optimization of the process flow and precise control of key nodes, while matching specific reaction aids. This process not only enables continuous production, but also achieves precise control of the molecular weight distribution of the polymer, resulting in a narrow molecular weight distribution and uniform product viscosity.

Description

Technical Field

[0001] The present application relates to a one-step prepared bio-based nylon 12 and its preparation method and application, belonging to the technical field of polyamide materials. Background Art

[0002] Long-chain nylon 12 boasts excellent properties, including low density, low water absorption, excellent dimensional stability in workpieces, thermal stability, toughness, and flexibility. It also offers advantages such as oil resistance, low-temperature resistance, corrosion resistance, and resistance to friction loss. Traditionally produced nylon 12 from chemical processing is widely used in automotive, chemical and petroleum pipelines, hydraulic transmission systems, electronics, electrical appliances, plastic alloys, and aerospace and military equipment. Currently, four foreign companies—Arkema, EMS of Switzerland, UBE, and Evonik—are producing nylon 12 on a large scale in China. In recent years, only one domestic company, Shandong Wanhua Chemical, has broken the monopoly of foreign companies and joined the production ranks.

[0003] There are currently two process routes for synthesizing nylon 12:

[0004] One method uses ring-opening polymerization of laurolactam as a raw material to produce nylon 12, while the other uses 12-aminododecanoic acid (lauric acid) as a monomer raw material. Laurolactam uses butadiene as a raw material to produce cyclododecatriene as an intermediate. This chemical process has a lengthy, seven-step synthesis route, and approximately 10% of the primary product contains residual monomers that require extraction and purification, resulting in a lengthy production process and high costs. Wanhua Chemical, a domestic company, and Arkema, EMS Switzerland, UBE, and Evonik, four foreign companies, essentially use this process for large-scale production. Wanhua Chemical has a related patent, CN106866956B, for a multi-stage tandem polymerization method for polylaurolactam and its modified resins. While this method utilizes multiple reactors to achieve continuous production, the process is complex, the synthesis route is long, and energy consumption and costs are high.

[0005] Another process route uses 12-aminododecanoic acid as the monomer raw material to produce nylon 12. This synthetic route is shorter than that of laurolactam, with lower equipment and overall production costs. However, due to the high reactivity of 12-aminododecanoic acid, poor reaction control can lead to problems such as implosion, depolymerization, and yellowing of the polymer.

[0006] Chinese patent CN107312170B - A process for preparing nylon 12 using long-chain amino acids as monomers uses 12-aminododecanoic acid as a monomer and is prepared through a three-step process, specifically using a pre-polymerization kettle, a polymerization kettle and a melt metering pump for segmented and step-by-step polymerization, and finally using a twin-screw extruder to increase viscosity to obtain nylon 12. Its main advantage is that it can directly produce high-viscosity and high-molecular-weight chips.

[0007] However, this technical solution still has the following problems in practical application:

[0008] 1. This solution cannot be used for continuous production in actual production. The solution is a three-step process. After the first batch of production is completed, the temperature inside the batch and the jacket is still very high (about 240℃-270℃). Raw materials, auxiliary materials and room temperature water cannot be added immediately, making intermittent polymerization continuous production difficult to achieve.

[0009] 2. The examples in its specification state that the molecular weight distribution index (PDI) of the final nylon 12 product produced is between 2.3 and 2.6. This indicates that the three-step method has not yet solved the problem of controlling the polymerization rate and reaction process during the reaction. The molecular weight distribution in the final system is wide. The wider the molecular weight distribution, the greater the molecular weight difference in the polymer and the more uneven the distribution. In other words, its molecular weight normal distribution is still poor, and the product quality needs to be improved.

[0010] 3. The entire production cycle is long (about 8-12 hours), and there are many production equipments, the energy consumption required for heating and insulation is high, and the total production cost is high. Summary of the Invention

[0011] To address the above-mentioned issues, the present application provides a one-step preparation of bio-based nylon 12, its preparation method, and application. By comprehensively optimizing the process flow and precisely controlling key nodes, while matching specific reaction aids, a one-step process (i.e., in the same reactor) is ultimately achieved for polymerizing nylon 12 using bio-based 12-aminododecanoic acid as a monomer. This not only enables continuous production with a short production cycle, but also achieves precise control of the polymer molecular weight distribution. The resulting products have a molecular weight distribution index of less than 2, a narrow molecular weight distribution, uniform product viscosity, and stable quality. Furthermore, the bio-based nylon 12 ultimately prepared in this application has a high polymer system yield, low residual monomer residue, is non-toxic, and is environmentally friendly. It can be used in areas such as food, clothing, and daily necessities, and pharmaceutical packaging.

[0012] According to one aspect of the present application, a one-step method for preparing bio-based nylon 12 is provided, comprising the following steps:

[0013] (1) Preparation: Bio-based 12-aminododecanoic acid, water and reaction aids are mixed in a preparation tank to form a suspension;

[0014] (2) Feeding: adding the suspension into the polymerization kettle by nitrogen pressurization;

[0015] (3) Aggregation: The following operations are performed in sequence through the control system:

[0016] i. Increase temperature and pressure: Start stirring, increase temperature to 175-185℃, and increase pressure to 0.8-1.5 MPa;

[0017] ii. Constant temperature and pressure: Keep the temperature no higher than 185℃, the pressure stable, and gradually drain the water. The temperature of the material will automatically rise after the water is drained. The material temperature will not exceed 220℃. When the material temperature rises to a certain temperature, the pressure will be reduced in stages, but the pressure must always be maintained at no less than 0.6MPa;

[0018] iii. Temperature increase and pressure reduction: The material temperature is gradually increased and the pressure is reduced to normal pressure. The material temperature is controlled at 230℃-270℃;

[0019] iv. Constant temperature and pressure: Maintain constant temperature and nitrogen purge for 0.5-1h;

[0020] v. Constant temperature vacuum: Keep the temperature constant and evacuate to 0.06-0.09 MPa;

[0021] vi. Nitrogen pressurization: The polymer melt is discharged by nitrogen pressurization, and the water-cooled strands are pelletized to obtain bio-based nylon 12;

[0022] Among them, the reaction aids include catalysts, antioxidants and molecular weight regulators, and the added amounts are 0.005-0.04%, 0.01-0.5% and 0.02-0.5% of the total raw material mass respectively; the mass proportion of adipic acid in the molecular weight regulator is not less than 60%.

[0023] Optionally, in step (1), the mass ratio of bio-based 12-aminododecanoic acid to water is 1:(1-2), the temperature is raised to 70-120° C., and the mixture is stirred and mixed evenly.

[0024] Specifically, the polymerization kettle of the present application is equipped with a dedicated feed tank, which can immediately pressurize the mixed and temperature-appropriate raw material suspension into the polymerization kettle in the production state with nitrogen, thereby achieving seamless intermittent polymerization and continuous production. The control system used in step (3) is a DCS control system.

[0025] Optionally, in the constant temperature and pressure holding stage of step (3), the polymerization and dehydration time is 2-3.5 hours; the trigger temperature for the staged pressure reduction is 205-215°C, and the pressure reduction rate is 0.05-0.1 MPa / min. Preferably, the trigger temperature is 210°C.

[0026] Optionally, in the constant temperature and pressure stage of step (3), the nitrogen purge flow rate is 0.5-1.5 L / min, and the initial flow rate is higher than the final flow rate.

[0027] Specifically, in the constant temperature and normal pressure stage of step (3), the nitrogen purge includes three gradient stages in sequence: a. 0-20 min, flow rate 1.5 L / min; b. 20-40 min, flow rate 1.0 L / min; c. 40-60 min, flow rate 0.6 L / min.

[0028] Furthermore, during the development of a one-step method for preparing bio-based nylon 12 using 12-aminododecanoic acid as a monomer, the inventors of this application discovered that there are two core problems in the polymerization process of 12-aminododecanoic acid:

[0029] The first problem is that when the temperature rises to near the melting point, polymerization reaction will occur rapidly. At this time, if the pressure and temperature are not properly controlled, it will cause problems such as explosion or depolymerization, and the polymer will coke and yellow.

[0030] Therefore, in the second stage of polymerization, that is, the constant temperature and pressure holding stage, the present application first accurately controls the polymerization dehydration temperature to be no higher than 185°C, maintains the pressure stable and controls the drainage time, so that in this stage it is in a solid-liquid coexistence state, the lattice gap is expanded, and the water molecules are efficiently diffused. At the same time, the pressure is controlled to maintain the presence of liquid water to avoid premature vaporization and volume expansion that destroys the material structure. At the same time, due to the enthalpy change of the polycondensation reaction, heat is released during the water removal process, the material temperature automatically rises, and melt polymerization begins. In order to further remove moisture and other impurities to increase viscosity and avoid yellowing, the present application limits the temperature to the trigger temperature before gradually reducing the pressure, and also maintains the minimum pressure at above 0.6 MPa. At this time, the melt stability is maintained by high pressure, and the reverse reaction of polycondensation is suppressed, so that the material can be stably polymerized and the water molecules can be fully discharged. If the material temperature rises too high before reducing the pressure at this stage, the product will coke and yellow; if the pressure is lower than 0.6 MPa, the molecular chain will depolymerize and the water cannot be fully discharged.

[0031] The second problem, which is also the most significant feature that distinguishes it from other nylons, is that due to its extremely fast polymerization speed, many small molecules do not have time to be discharged from the polymer system. As the viscosity increases in the later stages of polymerization, the discharge becomes slower, which ultimately leads to uneven viscosity, too wide a molecular weight distribution, and even inability to properly draw strands and pelletize.

[0032] To this end, the present application first blows in an appropriate amount of nitrogen in the fourth stage of polymerization (constant temperature and normal pressure stage), and controls the initial flow rate of nitrogen to be higher than the final flow rate. The initial high flow rate causes the nitrogen to form turbulence on the surface of the melt, forming a vortex peeling boundary layer, accelerating the removal of free small molecules (water, oligomers, other organic matter, etc.), the mid-term transition flow continuously removes residual substances at the grain boundaries, and the late laminar flow maintains the stability of the material state.

[0033] Optionally, the molecular weight regulator includes at least adipic acid and further includes acetic acid and / or benzoic acid.

[0034] Preferably, the molecular weight regulator includes adipic acid and acetic acid in a mass ratio of 3:1; or, the molecular weight regulator includes adipic acid and benzoic acid in a mass ratio of 7:3; or, the molecular weight regulator includes adipic acid, acetic acid and benzoic acid in a mass ratio of 6:2:2.

[0035] Specifically, by using adipic acid and limiting it to the main regulator, the carboxylic acid group of adipic acid acts as a Bronsted acid, proton-activating the amino group and reducing the nucleophilic activation energy of the amino group. The protonated amino group is more likely to attack the carboxylic acid carbonyl oxygen to form an amide bond, which can assist in catalyzing and accelerating polycondensation in the early stage of the polymerization reaction. The reaction is stable in the middle stage, promoting the improvement of monomer conversion rate. In the later stage of polymerization, efficient chain termination can be achieved, end-capping is completed, and the molecular weight distribution is effectively controlled. Limiting its proportion can maintain linear control of molecular weight while promoting the effective removal of water molecules. In addition, if it is used in combination with acetic acid and benzoic acid, the synergistic effect between them can also inhibit the formation of oligomers to a certain extent, further optimizing the molecular weight distribution.

[0036] Optionally, the catalyst is one or more of phosphoric acid, sodium phosphite and sodium hypophosphite.

[0037] Optionally, the antioxidant is one or more of antioxidant 1010, antioxidant H10 and antioxidant 1098.

[0038] Optionally, in step (2), the nitrogen gas is pressurized to 0.2-0.5 MPa to press the suspension into the polymerization kettle.

[0039] Optionally, the stirring speed during the temperature and pressure increase stage in step (3) is 130-150 rpm, and the time is 1-2 h;

[0040] The temperature rise and pressure reduction stage lasts for 1-1.5 h, and the pressure is gradually reduced to normal pressure. The pressure reduction rate depends on the initial pressure and time of this stage. The constant temperature vacuum stage lasts for 30-60 min. The nitrogen pressurization stage lasts for 10-15 min, and the pressure is 0.2-0.5 MPa.

[0041] According to another aspect of the present application, a bio-based nylon 12 prepared by the above preparation method is also provided, wherein the molecular weight distribution index of the bio-based nylon 12 is 1.8-1.95 and the weight average molecular weight is 26000-30000.

[0042] According to another aspect of the present application, an application of the bio-based nylon 12 prepared by the above preparation method is also provided. The bio-based nylon 12 can be used for clothing, food packaging materials and medical packaging materials.

[0043] The beneficial effects of this application include but are not limited to:

[0044] 1. According to the one-step method for preparing bio-based nylon 12 disclosed herein, by using a feed tank coupled with a single-reactor six-stage full-process control, the entire polymerization process is integrated into a single polymerization reactor, achieving efficient, one-step continuous production. The production cycle is compressed from 12-15 hours to 6-8 hours, significantly shortening the production cycle and improving production efficiency.

[0045] 2. The one-step method for preparing bio-based nylon 12 disclosed herein utilizes controlled temperature and pressure during the critical polymerization stage (constant temperature and pressure holding stage) to achieve sufficient water removal while effectively controlling the polymerization rate. A nitrogen gradient purge effectively removes small molecule impurities. Furthermore, the method, in conjunction with a specific molecular weight regulator, allows for precise molecular weight control. The resulting product has a narrow molecular weight distribution (1.8-1.95), uniform and stable viscosity, and high yield.

[0046] 3. The one-step method for preparing bio-based nylon 12 according to this application utilizes bio-based raw material monomers and achieves improved monomer conversion through coordinated temperature-pressure control during the constant temperature and pressure holding phase of the polymerization stage. Furthermore, the combination of gradient nitrogen purge and vacuum devolatilization efficiently removes residual monomers, ultimately resulting in a product with minimal residual monomers. This environmentally friendly and harmless product is suitable for applications in areas such as clothing, food, and pharmaceutical packaging, promoting green upgrades in the industrial chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0048] Figure 1 This is a chromatogram of nylon 12 prepared using Example 1 of the present application;

[0049] Figure 2 The chromatogram is of nylon 12 prepared by Example 4 of the present application. DETAILED DESCRIPTION

[0050] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0051] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents and raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents and raw materials used in the present invention are used in accordance with conventional methods in the art or in accordance with the product instructions. In addition, any methods and materials similar to or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0052] Among them, the bio-based 12-aminododecanoic acid used in this application is a commercially available product derived from biological resources such as plant oils such as castor oil. The commercially available polymerization kettle equipped with an outer jacket + inner coil dual heating system used in this application is equipped with a reaction preparation tank. In the first two steps of the polymerization process of this application (temperature and pressure increase and constant temperature and pressure maintenance process), the materials undergo polymerization reactions in a nitrogen environment, but nitrogen, other gases, as well as moisture and other small molecules, will also be gradually discharged during the constant temperature and pressure maintenance process. The water used in the preparation method is high-purity water or desalted water, and normal pressure refers to standard atmospheric pressure; the amount of bio-based 12-aminododecanoic acid used in the embodiment is 5 kg.

[0053] Example 1 Bio-based nylon 12-1#

[0054] The preparation method of bio-based nylon 12-1# comprises the following steps:

[0055] (1) Preparation: Bio-based 12-aminododecanoic acid, water and reaction aids are mixed in a preparation tank to form a suspension;

[0056] (2) Feeding: adding the suspension into the polymerization reactor by nitrogen pressurization;

[0057] (3) Aggregation: The following operations are performed in sequence through the control system:

[0058] i. Increase temperature and pressure: Start stirring, increase temperature to 180°C and pressure to 1.2 MPa;

[0059] ii. Constant temperature and pressure: Keep the temperature no higher than 185℃, the pressure stable, and gradually drain the water. The temperature of the material will automatically rise after the water is drained. The material temperature will not exceed 220℃. When the material temperature rises to a certain temperature, the pressure will be reduced in stages, but the pressure must always be maintained at no less than 0.6MPa;

[0060] iii. Temperature increase and pressure reduction: The material temperature is gradually increased, the pressure is reduced to normal pressure, and the material temperature is controlled at 240°C;

[0061] iv. Constant temperature and pressure: Maintain temperature and balance with nitrogen purge for 1 hour;

[0062] v. Constant temperature vacuum: keep the temperature constant and evacuate to 0.06MPa;

[0063] Nitrogen pressurization: The polymer melt is discharged through nitrogen pressurization, and the bio-based nylon 12-1# is obtained by water-cooling and pelletizing.

[0064] In step (1), the mass ratio of bio-based 12-aminododecanoic acid to water is 1:1, the temperature is raised to 80°C, and the mixture is stirred and mixed uniformly at a stirring rate of 100 rpm; the reaction aids include a catalyst, an antioxidant, and a molecular weight regulator, and the addition amounts are 0.02%, 0.1%, and 0.2% of the total raw material mass, respectively; the molecular weight regulator is adipic acid; the catalyst is phosphoric acid; and the antioxidant is antioxidant 1010.

[0065] In step (2), nitrogen is pressurized to 0.3 MPa to press the suspension into the polymerization kettle.

[0066] In step (3), the stirring speed during the temperature and pressure increase stage is 140 rpm, and the duration is 1.5 h. During the constant temperature and pressure holding stage, the polymerization dehydration time is 2 h, the trigger temperature for the staged pressure reduction is 210°C, and the pressure reduction rate is 0.08 MPa / min. The temperature increase and pressure reduction stage lasts for 1.2 h. During the constant temperature and pressure stage, the nitrogen purge flow rate in the first half is 1.2 L / min, which is 0.5 L / min higher than the purge flow rate in the second half. The constant temperature vacuum stage lasts for 45 min. The nitrogen pressurization stage lasts for 12 min, and the pressure is 0.3 MPa.

[0067] Example 2 Bio-based nylon 12-2#

[0068] The preparation method of bio-based nylon 12-2# comprises the following steps:

[0069] (1) Preparation: Bio-based 12-aminododecanoic acid, water and reaction aids are mixed in a preparation tank to form a suspension;

[0070] (2) Feeding: adding the suspension into the polymerization reactor by nitrogen pressurization;

[0071] (3) Aggregation: The following operations are performed in sequence through the control system:

[0072] i. Increase temperature and pressure: Start stirring, increase temperature to 175°C and pressure to 0.8 MPa;

[0073] ii. Constant temperature and pressure: Keep the temperature no higher than 185℃, the pressure stable, and gradually drain the water. The temperature of the material will automatically rise after the water is drained. The material temperature will not exceed 220℃. When the material temperature rises to a certain temperature, the pressure will be reduced in stages, but the pressure must always be maintained at no less than 0.6MPa;

[0074] iii. Temperature increase and pressure reduction: The material temperature is gradually increased, the pressure is reduced to normal pressure, and the material temperature is controlled at 230°C;

[0075] iv. Constant temperature and pressure: Maintain temperature and balance with nitrogen purge for 1 hour;

[0076] v. Constant temperature vacuum: keep the temperature constant and evacuate to 0.09 MPa;

[0077] Nitrogen pressurization: The polymer melt is discharged through nitrogen pressurization, and the bio-based nylon 12-2# is obtained by water-cooling and pelletizing.

[0078] In step (1), the mass ratio of bio-based 12-aminododecanoic acid to water is 1:2, the temperature is raised to 120° C., and the mixture is stirred and mixed uniformly at a stirring rate of 100 rpm; the reaction aids include a catalyst, an antioxidant, and a molecular weight regulator, and the addition amounts are 0.005%, 0.01%, and 0.05% of the total raw material mass, respectively; the molecular weight regulator includes adipic acid and acetic acid, and the mass ratio is 3:1; the catalyst is sodium phosphite; and the antioxidant is antioxidant 1098.

[0079] In step (2), nitrogen is pressurized to 0.5 MPa to press the suspension into the polymerization kettle.

[0080] In step (3), the stirring speed during the temperature and pressure increase stage is 130 rpm, and the duration is 2 hours. During the constant temperature and pressure holding stage, the polymerization dehydration time is 3 hours, the trigger temperature for the staged pressure reduction is 215°C, and the pressure reduction rate is 0.1 MPa / min. The temperature increase and pressure reduction stage lasts for 1.5 hours. During the constant temperature and pressure stage, the nitrogen purge flow rate in the first half is 1.5 L / min, which is 0.5 L / min higher than the purge flow rate in the second half. The constant temperature vacuum stage lasts for 60 minutes. The nitrogen pressurization stage lasts for 10 minutes, and the pressure is 0.5 MPa.

[0081] Example 3 Bio-based nylon 12-3#

[0082] The preparation method of bio-based nylon 12-3# comprises the following steps:

[0083] (1) Preparation: Bio-based 12-aminododecanoic acid, water and reaction aids are mixed in a preparation tank to form a suspension;

[0084] (2) Feeding: adding the suspension into the polymerization reactor by nitrogen pressurization;

[0085] (3) Aggregation: The following operations are performed in sequence through the control system:

[0086] i. Increase temperature and pressure: Start stirring, increase temperature to 185°C and pressure to 1.5 MPa;

[0087] ii. Constant temperature and pressure: Keep the temperature no higher than 185℃, the pressure stable, and gradually drain the water. The temperature of the material will automatically rise after the water is drained. The material temperature will not exceed 220℃. When the material temperature rises to a certain temperature, the pressure will be reduced in stages, but the pressure must always be maintained at no less than 0.6MPa;

[0088] iii. Temperature increase and pressure reduction: The material temperature is gradually increased, the pressure is reduced to normal pressure, and the material temperature is controlled at 270°C;

[0089] iv. Constant temperature and pressure: Maintain temperature and balance with nitrogen purge for 0.75h;

[0090] v. Constant temperature vacuum: keep the temperature constant and evacuate to 0.08 MPa;

[0091] Nitrogen pressurization: The polymer melt is discharged through nitrogen pressurization, and then water-cooled strands are cut into pellets to obtain bio-based nylon 12-3#.

[0092] In step (1), the mass ratio of bio-based 12-aminododecanoic acid to water is 1:1.5, the temperature is raised to 100°C, and the mixture is stirred and mixed uniformly at a stirring rate of 100 rpm; the reaction aids include a catalyst, an antioxidant, and a molecular weight regulator, and the addition amounts are 0.04%, 0.5%, and 0.5% of the total raw material mass, respectively; the molecular weight regulator includes adipic acid and benzoic acid, and the mass ratio is 7:3; the catalyst is sodium hypophosphite; and the antioxidant is antioxidant H10.

[0093] In step (2), nitrogen is pressurized to 0.5 MPa to press the suspension into the polymerization kettle.

[0094] In step (3), the stirring speed during the temperature and pressure increase stage is 150 rpm, and the duration is 1 hour. During the constant temperature and pressure holding stage, the polymerization dehydration time is 2 hours, the trigger temperature for the staged pressure reduction is 205°C, and the pressure reduction rate is 0.05 MPa / min. The temperature increase and pressure reduction stage lasts for 1 hour. During the constant temperature and pressure stage, the nitrogen purge flow rate in the first half is 1.0 L / min, which is 0.5 L / min higher than the purge flow rate in the second half. The constant temperature vacuum stage lasts for 30 minutes. The nitrogen pressurization stage lasts for 15 minutes, and the pressure is 0.2 MPa.

[0095] Example 4 Bio-based nylon 12-4#

[0096] The preparation method of bio-based nylon 12-4# comprises the following steps:

[0097] (1) Preparation: Bio-based 12-aminododecanoic acid, water and reaction aids are mixed in a preparation tank to form a suspension;

[0098] (2) Feeding: adding the suspension into the polymerization reactor by nitrogen pressurization;

[0099] (3) Aggregation: The following operations are performed in sequence through the control system:

[0100] i. Temperature and pressure increase: Start stirring, raise the temperature to 180°C and the pressure to 1.0 MPa;

[0101] ii. Constant temperature and pressure: Keep the temperature no higher than 185℃, the pressure stable, and gradually drain the water. The temperature of the material will automatically rise after the water is drained. The material temperature will not exceed 220℃. When the material temperature rises to a certain temperature, the pressure will be reduced in stages, but the pressure must always be maintained at no less than 0.6MPa;

[0102] iii. Temperature increase and pressure reduction: The material temperature is gradually increased, the pressure is reduced to normal pressure, and the material temperature is controlled at 240°C;

[0103] iv. Constant temperature and pressure: Maintain temperature and balance with nitrogen purge for 0.8h;

[0104] v. Constant temperature vacuum: keep the temperature constant and evacuate to 0.06 MPa;

[0105] Nitrogen pressurization: The polymer melt is discharged through nitrogen pressurization, and then water-cooled strands are cut into pellets to obtain bio-based nylon 12-4#.

[0106] In step (1), the mass ratio of bio-based 12-aminododecanoic acid to water is 1:1.5, the temperature is raised to 80°C, and the mixture is stirred and mixed uniformly at a stirring rate of 100 rpm; the reaction aids include a catalyst, an antioxidant, and a molecular weight regulator, and the addition amounts are 0.01%, 0.2%, and 0.5% of the total raw material mass, respectively; the molecular weight regulator includes adipic acid, acetic acid, and benzoic acid, and the mass ratios are 6:2:2, respectively; the catalyst is phosphoric acid; and the antioxidant is antioxidant H10.

[0107] In step (2), nitrogen is pressurized to 0.5 MPa to press the suspension into the polymerization kettle.

[0108] In step (3), the stirring speed during the temperature and pressure increase stage is 140 rpm, and the duration is 1.5 h. During the constant temperature and pressure holding stage, the polymerization dehydration time is 2.5 h, the trigger temperature for the staged pressure reduction is 210°C, and the pressure reduction rate is 0.1 MPa / min. The temperature increase and pressure reduction stage lasts for 1.5 h. During the constant temperature and pressure stage, the nitrogen purge includes three gradient stages in sequence: a. 0-20 min, flow rate 1.5 L / min; b. 20-40 min, flow rate 1.0 L / min; c. 40-60 min, flow rate 0.6 L / min. The constant temperature vacuum stage lasts for 45 min. The nitrogen pressurization stage lasts for 13 min, and the pressure is 0.4 MPa.

[0109] Example 5 Bio-based nylon 12-5#

[0110] The preparation method of bio-based nylon 12-5# comprises the following steps:

[0111] (1) Preparation: Bio-based 12-aminododecanoic acid, water and reaction aids are mixed in a preparation tank to form a suspension;

[0112] (2) Feeding: adding the suspension into the polymerization reactor by nitrogen pressurization;

[0113] (3) Aggregation: The following operations are performed in sequence through the control system:

[0114] i. Increase temperature and pressure: Start stirring, increase temperature to 180°C, and increase pressure to 1.3 MPa;

[0115] ii. Constant temperature and pressure: Keep the temperature no higher than 185℃, the pressure stable, and gradually drain the water. The temperature of the material will automatically rise after the water is drained. The material temperature will not exceed 220℃. When the material temperature rises to a certain temperature, the pressure will be reduced in stages, but the pressure must always be maintained at no less than 0.6MPa;

[0116] iii. Temperature increase and pressure reduction: The material temperature is gradually increased, the pressure is reduced to normal pressure, and the material temperature is controlled at 250°C;

[0117] iv. Constant temperature and pressure: Maintain temperature and balance with nitrogen purge for 1 hour;

[0118] v. Constant temperature vacuum: keep the temperature constant and evacuate to 0.06MPa;

[0119] Nitrogen pressurization: The polymer melt is discharged through nitrogen pressurization, and then water-cooled strands are cut into pellets to obtain bio-based nylon 12-5#.

[0120] In step (1), the mass ratio of bio-based 12-aminododecanoic acid to water is 1:1, the temperature is raised to 80° C., and the mixture is stirred and mixed uniformly at a stirring rate of 100 rpm; the reaction aids include a catalyst, an antioxidant, and a molecular weight regulator, and the addition amounts are 0.02%, 0.1%, and 0.3% of the total raw material mass, respectively; the molecular weight regulator is adipic acid; the catalyst is phosphoric acid; and the antioxidant is antioxidant 1010.

[0121] In step (2), nitrogen is pressurized to 0.3 MPa to press the suspension into the polymerization kettle.

[0122] In step (3), the stirring speed during the temperature and pressure increase stage is 140 rpm, and the duration is 1.5 h. During the constant temperature and pressure holding stage, the polymerization dehydration time is 2 h, the trigger temperature for the staged pressure reduction is 210°C, and the pressure reduction rate is 0.08 MPa / min. The temperature increase and pressure reduction stage lasts for 1.2 h. During the constant temperature and pressure stage, the nitrogen purge flow rate is constant at 0.8 L / min. The constant temperature vacuum stage lasts for 45 min. The nitrogen pressurization stage lasts for 12 min, and the pressure is 0.3 MPa.

[0123] Comparative Example 1: Bio-based nylon 12-1#

[0124] The difference between Comparative Example 1 and Example 1 is that in the constant temperature and pressure holding stage of step (3) in Comparative Example 1, the pressure is reduced in stages when the material temperature reaches 240°C.

[0125] Comparative Example 2: Bio-based nylon 12-2#

[0126] The difference between Comparative Example 2 and Example 1 is that the pressure in the constant temperature and pressure holding stage of step (3) in Comparative Example 2 is finally reduced to 0.4 MPa.

[0127] Comparative Example 3: Bio-based nylon 12-3#

[0128] The difference between Comparative Example 3 and Example 1 is that nitrogen purging is not used in the constant temperature and normal pressure stage of step (3) in Comparative Example 3.

[0129] Comparative Example 4: Bio-based nylon 12-4#

[0130] The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, the mass proportion of adipic acid in the molecular weight regulator is 20%, and the rest is acetic acid.

[0131] Experimental example

[0132] The bio-based nylon 12 1#-5# prepared in Examples 1-5 and the comparative bio-based nylon 12 1#-4# prepared in Comparative Examples 1-4 were tested for mechanical properties, molecular weight and distribution, and yield. Yield was determined by weighing after vacuum drying. Table 1 lists the test items and methods, and Tables 2 and 3 provide the experimental data.

[0133] Table 1 Experimental test items and methods

[0134]

[0135] Table 2 Experimental data of molecular weight and its distribution, viscosity and yield

[0136]

[0137] Table 3 Mechanical properties and product status data

[0138]

[0139] As can be seen from the above table, the nylon 12 prepared using the raw materials and methods specified in this application not only has a narrow molecular weight distribution (PDI of 1.86-1.95), low residual monomer content, and high yield, but also has a weight-average molecular weight of 26,000-30,000 and a PDI of less than 2, indicating that it is high-quality nylon 12 with a uniform molecular weight distribution. It is also non-toxic and environmentally friendly, ultimately enabling it to meet the demand for high-quality nylon 12 in areas such as food, clothing, daily necessities, and pharmaceutical packaging. Furthermore, the preparation method of this application enables one-step continuous production, with a short production cycle and high efficiency, simple equipment, low cost investment, and significantly reduced energy consumption.

[0140] The foregoing is merely an embodiment of the present application, and the scope of protection of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the technical ideas and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A one-step method for preparing bio-based nylon 12, characterized in that: The following steps are involved: (1) Preparation: Bio-based 12-aminododecanoic acid, water and reaction aids are mixed in a preparation tank to form a suspension; (2) Feeding: adding the suspension into the polymerization kettle by nitrogen pressurization; (3) Aggregation: The following operations are performed in sequence through the control system: i. Increase temperature and pressure: Start stirring, increase temperature to 175-185℃, and increase pressure to 0.8-1.5 MPa; ii. Constant temperature and pressure: Keep the temperature below 185°C and the pressure stable, gradually drain the water, and the temperature of the material will automatically rise after the water is drained. The material temperature should not exceed 220°C. When the material temperature reaches a certain temperature, the pressure will be reduced in stages. The trigger temperature for the staged pressure reduction is 205-215°C, but the pressure must always be maintained at no less than 0.6MPa. iii. Temperature increase and pressure reduction: The material temperature is gradually increased and the pressure is reduced to normal pressure. The material temperature is controlled at 230℃-270℃; iv. Constant temperature and pressure: Maintain constant temperature and nitrogen purge for 0.5-1h; v. Constant temperature vacuum: Keep the temperature constant and evacuate to 0.06-0.09 MPa; vi. Nitrogen pressurization: The polymer melt is discharged by nitrogen pressurization, and the water-cooled strands are pelletized to obtain bio-based nylon 12; Among them, the reaction aids include catalysts, antioxidants and molecular weight regulators, and the added amounts are 0.005-0.04%, 0.01-0.5% and 0.02-0.5% of the total raw material mass respectively; the mass proportion of adipic acid in the molecular weight regulator is not less than 60%.

2. The preparation method according to claim 1, characterized in that In the constant temperature and pressure holding stage of step (3), the polymerization dehydration time is 2-3.5 h, and the pressure reduction rate is 0.05-0.1 MPa / min.

3. The preparation method according to claim 1, characterized in that In the constant temperature and pressure stage of step (3), the nitrogen purge flow rate is 0.5-1.5 L / min, and the initial flow rate is higher than the final flow rate.

4. The preparation method according to claim 1, characterized in that The molecular weight regulator includes at least adipic acid and also includes acetic acid and / or benzoic acid.

5. The preparation method according to claim 1, characterized in that The catalyst is one or more of phosphoric acid, sodium phosphite and sodium hypophosphite.

6. The preparation method according to claim 1, characterized in that The antioxidant is one or more of antioxidant 1010, antioxidant H10 and antioxidant 1098.

7. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of bio-based 12-aminododecanoic acid to water is 1:(1-2), the temperature is raised to 70-120°C, and the mixture is stirred and mixed evenly; In step (2), nitrogen is pressurized to 0.2-0.5 MPa to pressurize the suspension into the polymerization kettle.

8. The preparation method according to claim 1, characterized in that In step (3), the stirring speed during the temperature and pressure increase stage is 130-150 rpm, and the time is 1-2 hours; The temperature rise and pressure reduction stage lasts for 1-1.5 h; the constant temperature vacuum stage lasts for 30-60 min; the nitrogen pressurization stage lasts for 10-15 min, and the pressure is 0.2-0.5 MPa.

9. A bio-based nylon 12 prepared by the method according to any one of claims 1 to 8, characterized in that: The molecular weight distribution index of the bio-based nylon 12 is 1.8-1.95, and the weight average molecular weight is 26000-30000.

10. The use of the bio-based nylon 12 according to claim 9, characterized in that: The bio-based nylon 12 is used for clothing, food packaging materials and medical packaging materials.

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