Laurolactam segmented temperature-control ring-opening polymerization method, nylon 12 and application of nylon 12

Abstract

The invention relates to the technical field of high polymer material synthesis, and particularly discloses a laurolactam segmented temperature control ring-opening polymerization method, nylon 12 and application thereof.The laurolactam segmented temperature control ring-opening polymerization method comprises the following steps that a polymer material is put into a polymerization reactor, the temperature is increased to a first temperature under the protective atmosphere, heat preservation is conducted, and a second temperature is obtained; the polymer material comprises laurolactam, a molecular weight regulator, a catalyst, an antioxidant and water; raising the temperature to a second temperature and keeping the temperature and the pressure; raising the temperature to a third temperature and keeping the temperature and the pressure, wherein the third temperature is higher than the second temperature; the pressure is relieved to normal pressure, the temperature is adjusted to a fourth temperature during pressure relief, and the fourth temperature is not higher than the third temperature; reducing the pressure to preset pressure and maintaining the pressure; and recovering to the positive pressure, cooling, and pelletizing to obtain the nylon 12. According to the invention, ring-opening polymerization of laurolactam is carried out by adopting segmented temperature control, so that the polymerization reaction process is dynamically controllable, and oxidative degradation and chain fracture side reactions caused by high temperature are effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis technology, and in particular to a segmented temperature-controlled ring-opening polymerization method for dodecyl lactam and nylon 12 and its applications. Background Technology

[0002] Nylon 12, a typical representative of long-chain polyamides, is prepared through the ring-opening polymerization of dodecyl lactam monomers. Its unique molecular structure endows it with excellent flexibility, low water absorption, chemical corrosion resistance, and abrasion resistance, making it irreplaceable in applications such as automotive fuel lines, pneumatic brake hoses, hydrogen transportation pipelines, medical catheters, and 3D printing. However, the ring-opening polymerization conditions for dodecyl lactam are quite demanding, with a significantly higher activation energy than caprolactam. This presents significant technical bottlenecks in its industrial applications, primarily manifested in three aspects: defects in reaction kinetic control, limited product performance, and insufficient process economy.

[0003] To address the aforementioned issues, current research on the ring-opening polymerization of dodecyl lactam primarily focuses on reactor design, synergistic effects of additives, and copolymerization modification to further optimize the polymerization process and material properties. Therefore, there is an urgent need to develop an efficient and controllable polymerization process that optimizes the reaction pathway and byproduct formation through precise temperature control and synergistic effects of catalysts, thereby improving product performance and promoting the penetration of nylon 12 in downstream high-end applications. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a segmented temperature-controlled ring-opening polymerization method for dodecyl lactam and nylon 12 and its applications, solving the problems of wide molecular weight distribution and numerous side reactions in the polymerization reaction of dodecyl lactam in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a segmented temperature-controlled ring-opening polymerization method for dodecyl lactam, comprising the following steps: adding a polymer material to a polymerization reactor, heating it to a first temperature under a protective atmosphere and holding the temperature thereon, wherein the polymer material includes dodecyl lactam, a molecular weight regulator, a catalyst, an antioxidant, and water; then heating it to a second temperature and holding the temperature and pressure thereon; then heating it to a third temperature and holding the temperature and pressure thereon, wherein the third temperature is higher than the second temperature; depressurizing it to atmospheric pressure, adjusting the temperature to a fourth temperature during the depressurization period, wherein the fourth temperature is not higher than the third temperature; reducing the pressure to a predetermined pressure and holding the pressure thereon; restoring the pressure to positive pressure, cooling, and pelletizing to obtain nylon 12.

[0007] As a further improvement to the above-described scheme of the present invention, the first temperature is 150-170°C, and is maintained at the first temperature for 0.5-3 hours. Low-temperature (150-170°C) melting stage: Based on the melting point of the monomer (153°C), under the protection of an inert gas, the temperature is raised to 150-170°C to form an aqueous solution, ensuring that the monomer is fully melted and initially ring-opened, avoiding premature ring-opening caused by high temperature, and reducing the formation of oligomers.

[0008] As a further improvement to the above-described scheme of the present invention, the second temperature is 200–230°C, and the temperature is maintained for 1–3 hours; and / or, the third temperature is 230–270°C, and the temperature is maintained for 2–5 hours. Mid-to-high temperature ring-opening stage: Based on thermogravimetric analysis, monomer mass loss occurs near 230°C. Therefore, the temperature can be slowly increased to 200–270°C for further hydrolysis and ring-opening. By controlling the hydrolysis and ring-opening rate, chain initiation and chain growth are synchronized, promoting hydrolysis and ring-opening. At this time, pressure control affects the reaction rate, avoiding a violent reaction that would broaden the molecular weight distribution.

[0009] As a further improvement to the above-described scheme of the present invention, the fourth temperature is 220–270°C. High-temperature polycondensation stage: The polycondensation reaction is accelerated under high-temperature vacuum conditions (220–270°C) to carry out deep polymerization, which is conducive to chain growth. At the same time, the role of metal catalysts may be more significant in this stage, controlling the rate of polycondensation reaction, reducing branched structures, and thus reducing PDI.

[0010] As a further improvement to the above-mentioned solution of the present invention, the predetermined pressure is -0.08 to -0.02 MPa, and is maintained at the predetermined pressure for 1 to 3 hours.

[0011] As a further improvement to the above-described scheme of the present invention, the molecular weight regulator is a compound containing an amino group; the content of the molecular weight regulator in the polymer material is 0.1wt% to 1.0wt%.

[0012] As a further improvement to the above-described scheme of the present invention, the molecular weight regulator is at least one selected from ethylenediamine, hexamethylenediamine, dodecanediamine, decanediamine, p-phenylenediamine, and 3,5-dimethylaniline.

[0013] As a further improvement of the above-mentioned scheme of the present invention, the catalyst includes an acid catalyst and a metal catalyst, and the content of the catalyst in the polymer material is 0.001wt% to 2wt%. Combining the synergistic effect of the composite catalyst: the acid catalyst can promote the ring-opening reaction, while the metal carboxylate has a significant effect in the polycondensation stage. The synergistic effect of the two can balance the ring-opening rate and chain growth efficiency, and avoid the reaction being too fast in a certain stage, resulting in uneven molecular weight distribution.

[0014] And / or, the antioxidant includes hindered phenolic antioxidants and phosphite antioxidants; in the polymer material, the content of the antioxidant is 0.001wt% to 2wt%, and the amount of water added is 1wt% to 30wt% of the amount of dodecanoic acid added.

[0015] The present invention also provides a nylon 12, which is prepared by the dodecanoic acid segmented temperature-controlled ring-opening polymerization method described above.

[0016] The present invention also provides an application of nylon 12 as described above in pipe fittings and lithium battery separators.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention employs segmented temperature control for the ring-opening polymerization of dodecanoic acid, allowing the polymerization reaction to sequentially undergo three stages: "low-temperature melting - medium-high temperature ring-opening - high-temperature polycondensation." This precisely matches the activation energy requirements of the hydrolysis ring-opening and polycondensation reactions, making the polymerization kinetics controllable and effectively suppressing high-temperature-induced oxidative degradation and chain scission side reactions. Simultaneously, by optimizing pressure control and catalyst distribution during the reaction process, the molecular weight distribution index (PDI) of the prepared product can be controlled below 2.3, while reducing oligomer formation. Specifically:

[0019] Low-temperature melting stage: Based on the melting point of the monomer (153℃), under the protection of inert gas, the temperature is raised to 150-170℃ to form an aqueous solution, ensuring that the monomer is fully melted and initially ring-opened, avoiding premature ring-opening caused by high temperature, and reducing the formation of oligomers.

[0020] In the medium-to-high temperature ring-opening stage: Based on thermogravimetric analysis, monomer mass loss occurs around 230℃. Therefore, the temperature can be slowly increased to 200-270℃ for further hydrolysis and ring-opening. The 200-230℃ range focuses on monomer protection and mild initiation, with the core objective of accumulating initial active centers (i.e., chain initiation sites) to lay the foundation for subsequent chain growth. The 230-270℃ range focuses on synchronized chain growth and rate control. Heating to higher temperatures significantly accelerates the reaction rate, promoting chain growth and synchronizing it with chain initiation (new hydrolysis and ring-opening). The synergistic effect of these two processes is key to obtaining a narrow molecular weight distribution. If initiation is too rapid, resulting in a large number of short chains, or if growth is too rapid, leading to excessively long chains in some chains, the distribution will widen. Therefore, by controlling the hydrolysis and ring-opening rate, chain initiation and chain growth are synchronized, promoting hydrolysis and ring-opening. At this point, pressure control affects the reaction rate, preventing a violent reaction that would broaden the molecular weight distribution.

[0021] High-temperature polycondensation stage: The polycondensation reaction is accelerated under high temperature and normal pressure (220-270℃) to carry out deep polymerization, which helps chain growth. At the same time, the role of metal catalysts may be more significant in this stage, controlling the rate of polycondensation reaction, reducing branched structure, and thus reducing PDI.

[0022] This invention also combines the synergistic effect of composite catalysts: acid catalysts can promote ring-opening reactions, while metal carboxylates have a significant effect in the polycondensation stage. The synergistic effect of the two can balance the ring-opening rate and chain growth efficiency, avoiding uneven molecular weight distribution caused by excessively rapid reactions in a certain stage.

[0023] The polydispersity index (PDI) of the product prepared by this invention can be narrowed to below 2.3, and the melt flow can be controlled. This meets the stringent requirements of high-end nylon 12 materials for uniformity and processing stability in precision injection molding, extrusion molding and other scenarios. It can be widely used in automotive fuel lines, medical catheters and industrial wear-resistant parts. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0026] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0027] Dodecyl lactam monomer: produced by Wanhua Chemical Group Co., Ltd.;

[0028] Molecular weight regulator: purity higher than 99.9%, produced by Sinopharm Reagent.

[0029] Antioxidant: Antioxidant 1010 and Antioxidant 168 are compounded in a 1:1 mass ratio, analytical grade, produced by Sinopharm Reagent.

[0030] Catalyst: Analytical grade, produced by Sinopharm Reagent.

[0031] The above-mentioned raw materials are only for illustrating the source and composition of the reagents used in the experiments of this invention, so as to fully disclose them, and do not imply that the invention cannot be achieved by using other similar reagents or reagents provided by other suppliers.

[0032] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0033] Example 1

[0034] This embodiment proposes a segmented temperature-controlled ring-opening polymerization method for dodecyl lactam, which includes the following steps:

[0035] 100 kg of dodecyl lactam monomer, 1 kg of molecular weight regulator dodecyl diamine, 500 g of catalyst (including 250 g of benzenesulfonic acid catalyst and 250 g of stannous chloride catalyst), 500 g of antioxidant (including 250 g of antioxidant 1010 and 250 g of antioxidant 168), and 20 kg of water were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 160°C and maintained for 1 hour to allow for complete dissolution. After the temperature and pressure stabilized, the solution was injected at 10°C / 10m³. The temperature was slowly increased to 230℃, and then held at 230℃ for 1 hour. The temperature was then increased to 270℃ and held at 270℃ for 3 hours. After holding at 270℃, the pressure was slowly released to atmospheric pressure, with the reaction temperature adjusted to 250℃ during this period. The vacuum system was then adjusted to further reduce the pressure inside the reactor to -0.05 MPa, and the polymerization reaction proceeded under the action of the catalyst, with a residence time of approximately 1 hour. Inert gas was then introduced to restore positive pressure inside the reactor. After polymerization was complete, the product was traction-cooled and pelletized from the outlet to obtain the qualified polymerized product, Nylon 12.

[0036] The Nylon 12 polymer product obtained in this embodiment has a relative viscosity of 2.23, a polydispersity index of 2.09, and an active end group content of 22%.

[0037] Example 2

[0038] This embodiment proposes a segmented temperature-controlled ring-opening polymerization method for dodecyl lactam, which includes the following steps:

[0039] 100 kg of dodecanoic acid monomer, 1 kg of molecular weight regulator dodecanediamine, 500 g of catalyst (including 250 g of benzenesulfonic acid catalyst and 250 g of stannous chloride metal catalyst), 500 g of antioxidant (including 250 g of antioxidant 1010 and 250 g of antioxidant 168), and 20 kg of water were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 160°C and maintained for 1 hour to allow for complete dissolution. After the temperature and pressure stabilized, the mixture was pumped at 10°C / 1... The temperature was slowly increased to 230℃ at a rate of 0 min, and then held at 230℃ and pressure for 1 hour. The temperature was then increased to 270℃ and held at 230℃ and pressure for 3 hours. After the holding and pressure were completed, the pressure was slowly released to atmospheric pressure, while the reaction temperature remained constant. Then, the vacuum system was adjusted to further reduce the pressure inside the reactor to -0.05 MPa, and the polycondensation reaction was carried out under the action of the catalyst for about 1 hour. Inert gas was introduced to restore the positive pressure inside the reactor. After polymerization was completed, the product was traction cooled and pelletized from the outlet to obtain qualified Nylon 12 product.

[0040] The Nylon 12 polymer product obtained in this embodiment has a relative viscosity of 2.40, a polydispersity index (PDI) of 2.18, and an active end group content of 12%.

[0041] Example 3

[0042] This embodiment proposes a segmented temperature-controlled ring-opening polymerization method for dodecyl lactam, which includes the following steps:

[0043] 100 kg of dodecyl lactam monomer, 1 kg of molecular weight regulator dodecanediamine, 500 g of catalyst (including 250 g of p-toluenesulfonic acid catalyst and 250 g of zinc acetate metal catalyst), 500 g of antioxidant (including 250 g of antioxidant 1010 and 250 g of antioxidant 168), and 20 kg of water were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 160°C and maintained for 1 hour to allow for complete dissolution. After the temperature and pressure stabilized, the mixture was pumped at 10°C / 1... The temperature was slowly increased to 230℃ at a rate of 0 min, and then held at 230℃ and pressure for 1 hour. The temperature was then increased to 270℃ and held at 230℃ and pressure for 3 hours. After the holding and pressure were completed, the pressure was slowly released to atmospheric pressure, and the reaction temperature was adjusted to 250℃ during this period. Then, the vacuum system was adjusted to further reduce the pressure inside the reactor to -0.05 MPa, and the polycondensation reaction was carried out under the action of the catalyst for about 1 hour. Inert gas was introduced to restore the positive pressure inside the reactor. After the polymerization was completed, the product was traction cooled and pelletized from the outlet to obtain qualified Nylon 12 product.

[0044] The Nylon 12 polymer product obtained in this embodiment has a relative viscosity of 2.20, a polydispersity index (PDI) of 2.11, and an active end group content of 20%.

[0045] Example 4

[0046] This embodiment proposes a segmented temperature-controlled ring-opening polymerization method for dodecyl lactam, which includes the following steps:

[0047] 100 kg of dodecyl lactam monomer, 1 kg of molecular weight regulator decanediamine, 500 g of catalyst (including 250 g of p-toluenesulfonic acid catalyst and 250 g of zinc acetate metal catalyst), 500 g of antioxidant (including 250 g of antioxidant 1010 and 250 g of antioxidant 168), and 20 kg of water were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 160°C and maintained for 1 hour to allow for complete dissolution. After the temperature and pressure stabilized, the solution was added at a rate of 10°C / 10 min. The temperature of n is slowly increased to 230℃, and then held at 230℃ for 1 hour. The temperature is then increased to 270℃ and held at 230℃ for 3 hours. After holding at 270℃, the pressure is slowly released to atmospheric pressure, during which the reaction temperature is adjusted to 250℃. Then, the vacuum system is adjusted to further reduce the pressure inside the reactor to -0.05 MPa, and the polycondensation reaction takes place under the action of the catalyst for about 1 hour. Inert gas is introduced to restore positive pressure inside the reactor. After polymerization is complete, the product is traction cooled and pelletized from the outlet to obtain the qualified polymerized product, Nylon 12.

[0048] The Nylon 12 polymer product obtained in this embodiment has a relative viscosity of 2.19, a polydispersity index (PDI) of 2.10, and an active end group content of 21%.

[0049] Comparative Example 1

[0050] This comparative example presents a method for ring-opening polymerization of dodecyl lactam, comprising the following steps: adding 100 kg of dodecyl lactam monomer, 1 kg of molecular weight regulator dodecanediamine, 500 g of catalyst (including 250 g of benzenesulfonic acid catalyst and 250 g of stannous chloride metal catalyst), 500 g of antioxidant (including 250 g of antioxidant 1010 and 250 g of antioxidant 168), and 20 kg of water to a polymerization reactor; purging the reactor with nitrogen five times; controlling the internal temperature of the polymerization reactor to rise to 160°C and maintaining this temperature for 2 hours. The solution is allowed to fully dissolve; after the temperature and pressure stabilize, the temperature is slowly increased to 260℃ at a rate of 10℃ / 10min, and then maintained at 260℃ and pressure for 4 hours; then the pressure is slowly released to atmospheric pressure, during which the reaction temperature is adjusted to 270℃; then the vacuum system is adjusted to further reduce the pressure inside the reactor to -0.05Mpa, and the condensation reaction is carried out under the action of the catalyst, with a residence time of about 1 hour; inert gas is introduced to restore the positive pressure inside the reactor, and the polymerization is completed. The product is then traction cooled and pelletized from the outlet to obtain the qualified polymerized product, Nylon 12.

[0051] The Nylon 12 polymer product obtained in this comparative example has a relative viscosity of 2.38, a polydispersity index (PDI) of 2.23, and an active end group content of 18%.

[0052] Comparative Example 2

[0053] This comparative example presents a method for ring-opening polymerization of dodecanoic acid, which includes the following steps:

[0054] 100 kg of dodecanoic acid monomer, 1 kg of molecular weight regulator dodecanediamine, 500 g of catalyst (including 250 g of benzenesulfonic acid catalyst and 250 g of stannous chloride metal catalyst), 500 g of antioxidant (including 250 g of antioxidant 1010 and 250 g of antioxidant 168), and 20 kg of water were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 170°C and maintained for 2 hours to allow for complete dissolution. The temperature and pressure were then adjusted accordingly. After stabilization, the temperature is slowly increased to 270℃ at a rate of 10℃ / 10min, and then maintained at 270℃ and pressure for 4 hours. Afterward, the pressure is slowly released to atmospheric pressure, and the reaction temperature is adjusted to 250℃ during this period. Then, the vacuum system is adjusted to further reduce the pressure inside the reactor to -0.05Mpa, and the polycondensation reaction is carried out under the action of the catalyst, with a residence time of about 1 hour. Inert gas is introduced to restore positive pressure inside the reactor. After polymerization is completed, the product is traction cooled and pelletized from the outlet to obtain qualified nylon 12 product.

[0055] The Nylon 12 polymer product obtained in this comparative example has a relative viscosity of 2.20, a polydispersity index (PDI) of 2.18, and an active end group content of 25%.

[0056] Comparative Example 3

[0057] This comparative example presents a method for ring-opening polymerization of dodecanoic acid, which includes the following steps:

[0058] 100 kg of dodecyl lactam monomer, 1 kg of molecular weight regulator dodecyl diamine, 500 g of catalyst (including 250 g of benzenesulfonic acid catalyst and 250 g of stannous chloride metal catalyst), 500 g of antioxidant (including 250 g of antioxidant 1010 and 250 g of antioxidant 168), and 20 kg of water were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 270°C at a rate of 10°C / 10 min. After reaching 270°C, the reactor was held at the same temperature and pressure for 4 hours. The pressure was then slowly released to atmospheric pressure, during which the reaction temperature was adjusted to 250°C. The vacuum system was then adjusted to further reduce the pressure inside the reactor to -0.05 MPa. Polycondensation was carried out under the action of the catalyst for about 1 hour. Inert gas was introduced to restore positive pressure inside the reactor. After polymerization, the product was traction cooled and pelletized from the outlet to obtain qualified Nylon 12 product.

[0059] The Nylon 12 polymer obtained in this comparative example had a relative viscosity of 2.19, a polydispersity index (PDI) of 2.38, and an active end group content of 29%.

[0060] Comparative Example 4

[0061] This comparative example presents a method for ring-opening polymerization of dodecanoic acid, which includes the following steps:

[0062] 100 kg of dodecyl lactam monomer, 1 kg of molecular weight regulator dodecyl diamine, 500 g of sodium hypophosphite, and 20 kg of sodium hypophosphite were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 270°C at a rate of 10°C / 10 min. After reaching 270°C, the reactor was kept at this temperature and pressure for 4 hours. The pressure was then slowly released to atmospheric pressure, during which the reaction temperature was adjusted to 250°C. The vacuum system was then adjusted to further reduce the pressure inside the reactor to -0.05 MPa. Polycondensation was carried out under the action of a catalyst for about 1 hour. Inert gas was introduced to restore positive pressure inside the reactor. After polymerization was completed, the product was traction cooled and pelletized from the outlet to obtain qualified Nylon 12 product.

[0063] The Nylon 12 polymer product obtained in this comparative example has a relative viscosity of 2.16, a polydispersity index (PDI) of 2.50, and an active end group content of 33%.

[0064] Comparative Example 5

[0065] This comparative example presents a method for ring-opening polymerization of dodecanoic acid, which includes the following steps:

[0066] 100 kg of dodecyl lactam monomer, 1 kg of molecular weight regulator dodecyl diamine, 500 g of sodium hypophosphite, and 20 kg of solvent water were added to the polymerization reactor. The reactor was purged with nitrogen five times. The internal temperature of the polymerization reactor was raised to 160°C and held for 1 hour to allow for complete dissolution. After the temperature and pressure stabilized, the temperature was slowly increased to 230°C at a rate of 10°C / 10 min. After reaching the temperature, the temperature and pressure were maintained for 1 hour. The temperature was then increased to 270°C and maintained for 3 hours. After the temperature and pressure were maintained, the pressure was slowly released to atmospheric pressure, and the reaction temperature was adjusted to 250°C during this period. The vacuum system was then adjusted to further reduce the pressure inside the reactor to -0.05 MPa. Polycondensation reaction was carried out under the action of the catalyst, with a residence time of about 1 hour. Inert gas was introduced to restore positive pressure inside the reactor. After polymerization was completed, the product was traction cooled and pelletized from the discharge port to obtain qualified Nylon 12 product.

[0067] The Nylon 12 polymer product obtained in this comparative example has a relative viscosity of 2.18, a polydispersity index (PDI) of 2.32, and an active end group content of 30%.

[0068] Test case

[0069] The nylon 12 products obtained in Examples 1-4 and Comparative Examples 1-5 were subjected to the following tests:

[0070] Active end group test: Hexafluoroisopropanol was used as the solvent. An appropriate amount of sample was weighed and dissolved, and the results were obtained by automatic titration.

[0071] Molecular weight and its distribution were determined using hexafluoroisopropanol as the mobile phase and analyzed by a Shimadzu LC-40D gel permeation chromatography (GPC) system.

[0072] Relative viscosity test: concentrated sulfuric acid was used as the solvent, the sample concentration was 0.01 g / ml, and the test was conducted under preheating at 25℃.

[0073] The test results are shown in Table 1.

[0074] Table 1 Test Results

[0075]

[0076]

[0077] According to the results in Table 1:

[0078] Compared with Example 2, Example 1 shows that the atmospheric pressure reaction temperature can control the viscosity of the product and also affects the PDI of the product. When the atmospheric pressure reaction temperature is 250°C, the product viscosity can be controlled to be low, and the PDI can be reduced. Therefore, the atmospheric pressure reaction temperature of 250°C is determined to be optimal.

[0079] Compared with Example 1, Comparative Examples 1-2 show that: Comparative Examples 1-2 directly increased from the first temperature to the third temperature in the intermediate temperature ring-opening stage, which led to an intensified chain growth reaction and a disconnect between chain initiation and growth. In addition, the high-temperature condensation in Comparative Example 1 was expected to result in a wider molecular weight distribution of the product and reduced quality stability.

[0080] Compared with Example 1, Comparative Examples 3-4 show that: Comparative Examples 3 and 4 directly undergo high-temperature polycondensation, which causes chain initiation to lag significantly behind high-speed chain growth. At the same time, pressure runaway exacerbates side reactions, increases the risk of uncontrollable process, results in uneven molecular weight distribution of products, and increases the number of by-products.

[0081] Compared with Example 1, Comparative Example 5 did not use a composite catalyst, and the polydispersity index was significantly increased. This proves that the combination of acid catalyst and metal catalyst of the present invention can balance the rates of ring opening and polycondensation, and avoid uneven molecular weight distribution caused by excessively fast reaction in a certain stage.

[0082] This invention employs a segmented temperature-controlled method for ring-opening polymerization of dodecanoic acid, combined with a cooling-based polycondensation reaction. This effectively controls the relative viscosity and polydispersity index of the product, resulting in a more concentrated molecular weight distribution, making it suitable for high-end product applications. Furthermore, the synergistic effect of the composite catalyst effectively improves the catalytic efficiency of dodecanoic acid polymerization, further optimizing the reaction pathway.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for segmented temperature-controlled ring-opening polymerization of dodecyl lactam, characterized in that, It includes the following steps: The polymer material is fed into a polymerization reactor, heated to a first temperature under a protective atmosphere and held at that temperature. The polymer material includes dodecyl lactam, a molecular weight regulator, a catalyst, an antioxidant, and water. Then the temperature is raised to a second temperature and held at that temperature and pressure. The temperature is then raised to a third temperature and maintained at that temperature and pressure, with the third temperature being higher than the second temperature. The pressure is then released to normal pressure, and during the pressure release, the temperature is adjusted to a fourth temperature, which is not higher than the third temperature. The pressure is then reduced to a predetermined pressure and maintained. The pressure is then restored to positive pressure, cooled, and pelletized to obtain Nylon 12.

2. The segmented temperature-controlled ring-opening polymerization method for dodecyl lactam according to claim 1, characterized in that, The first temperature is 150–170°C, and the temperature is maintained at the first temperature for 0.5–3 hours.

3. The segmented temperature-controlled ring-opening polymerization method for dodecyl lactam according to claim 1, characterized in that, The second temperature is 200–230°C, and the temperature is maintained for 1–3 hours; and / or the third temperature is 230–270°C, and the temperature is maintained for 2–5 hours.

4. The segmented temperature-controlled ring-opening polymerization method for dodecyl lactam according to claim 1, characterized in that, The fourth temperature is 220–270°C.

5. The segmented temperature-controlled ring-opening polymerization method for dodecyl lactam according to claim 1, characterized in that, The predetermined pressure is -0.08 to -0.02 MPa, and is maintained at the predetermined pressure for 1 to 3 hours.

6. The segmented temperature-controlled ring-opening polymerization method for dodecyl lactam according to claim 1, characterized in that, The molecular weight regulator is a compound containing an amino group; the content of the molecular weight regulator in the polymer material is 0.1 wt% to 1.0 wt%.

7. The segmented temperature-controlled ring-opening polymerization method for dodecyl lactam according to claim 5, characterized in that, The molecular weight regulator is at least one of ethylenediamine, hexamethylenediamine, dodecanediamine, decanediamine, p-phenylenediamine, and 3,5-dimethylaniline.

8. The segmented temperature-controlled ring-opening polymerization method for dodecyl lactam according to claim 1, characterized in that, The catalyst includes an acid catalyst and a metal catalyst, and the content of the catalyst in the polymer material is 0.001 wt% to 2 wt%; and / or, the antioxidant includes hindered phenolic antioxidants and phosphite antioxidants; the content of the antioxidant in the polymer material is 0.001 wt% to 2 wt%, and the amount of water added is 1 wt% to 30 wt% of the amount of dodecyl lactam added.

9. A type of nylon 12, characterized in that, It is prepared by the segmented temperature-controlled ring-opening polymerization method of dodecyl lactam as described in any one of claims 1-8.

10. The application of nylon 12 as described in claim 9 in pipe fittings and lithium battery separators.

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