Method for preparing polyesteramide through one-pot alcoholysis of PA6

Abstract

The invention relates to the cross technical field of polymer synthesis and plastic recycling. More specifically, the invention relates to a method for preparing polyesteramide through one-pot alcoholysis of PA6. The method comprises the following steps: uniformly mixing a PA6 raw material, dihydric alcohol and a catalyst, and carrying out alcoholysis reaction to obtain an alcoholysis product with the molecular weight of 1t; the preparation method comprises the following steps: adding a small molecule or oligomer intermediate with the molecular weight of 5000 g / mol, then supplementing a polymerizable monomer, and carrying out melt polycondensation to obtain polyesteramide PEA; wherein the polymerizable monomer is dibasic acid required for preparing polyesteramide or anhydride or ester corresponding to the dibasic acid. According to the method, direct synthesis from waste PA6 to high-performance degradable polyesteramide (PEA) can be efficiently realized, any complicated separation and purification steps are not needed in the whole process, the catalyst can also be used in the alcoholysis reaction and the repolymerization process at the same time, secondary addition is not needed, the steps are simpler and more convenient, the production cost is greatly reduced, and the production efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer synthesis and plastic recycling. More particularly, it relates to a method for preparing polyester amide by one-pot alcoholysis of PA6. BACKGROUND

[0002] The increasing global plastic consumption has led to serious environmental problems, especially the aggravation of "white pollution". Due to improper disposal and insufficient recycling, nearly 91% of plastics are incinerated or landfilled, not only increasing greenhouse gas emissions, but also leading to the leakage of microplastics into the environment. At present, the global annual plastic production reaches 450 million tons, and is expected to double by 2045. Under this background, as one of the five engineering plastics, the annual market size of polyamide (PA, commonly known as nylon) exceeds 8.5 million tons, and its sustainable recycling problem is particularly prominent.

[0003] Among various polyamides, nylon 6 (PA6) has been widely used in the fishing, automotive, packaging, carpet and textile industries since its invention by Schlack in 1938, due to its high tensile strength, rigidity, toughness, heat resistance and wear resistance. The commercial products of PA6 account for more than 50% of the global nylon market, and the revenue size is expected to exceed $21 billion in 2026. However, the production of PA6 consumes fossil fuels and nitrogen-containing chemicals, and also generates greenhouse gases, and its disposal speed after being discarded is far behind the global production pace. It is estimated that by 2050, the total weight of plastic waste in the ocean will exceed that of fish, and about 10% of marine plastic pollution comes from PA6 contained in discarded fishing nets, which is equivalent to more than 600,000 tons of fishing gear abandoned every year. More notably, the most commonly detected polymer in the stomach contents of marine animals is nylon, which highlights the persistent threat of this material to the global marine ecosystem. Therefore, it is urgent to develop innovative recycling solutions for such plastic waste.

[0004] As the most common plastic recycling method, the physical recycling method mainly obtains recycled chips by crushing, melting, filtering, cooling, granulating and drying of waste silk, waste blocks and leftover materials in the production process, and various specifications of recycled silk are prepared by melt spinning. However, unlike polyester, the characteristic functional groups of polyamide have higher reactivity, and thermal degradation is more serious when physical recycling is used, and the purity of the waste material is higher. In addition, mechanical recycling of nylon needs to be carried out at high temperature, which will cause significant deterioration of material performance and poor economic benefit, which greatly limits the application range of physical method. Chemical recycling is highly valued because it can realize closed-loop recycling, and the chemical recycling of polyamide is mainly based on alcoholysis, hydrolysis or ammonolysis under high temperature (≥250-300 ℃) conditions. Traditional methods such as hydrolysis need to be carried out under high temperature and high pressure, which limits its sustainable recycling. Ammonolysis has lower product selectivity, and needs to use noble metal catalysts and the like, which limits its large-scale application. Compared with hydrolysis or ammonolysis, alcoholysis can generally be carried out at a lower temperature (for example, 140 ℃-200 ℃) and under normal pressure or lower pressure. This significantly reduces energy consumption and equipment requirements, improves the safety and economy of the process. However, the alcoholysis product is generally complex, and in addition to the target product adipic acid diester or amino ester, it may also generate oligomers, dimers or other by-products, which affect the purity and yield of the final product and cause difficulties in subsequent separation and reuse. SUMMARY

[0005] Based on the above problems, one object of the present application is to provide a method for preparing polyester amide by one-pot alcoholysis of PA6.

[0006] Another object of the present application is to provide a polyester amide prepared by the method as described above.

[0007] To achieve the first object, the present application adopts the following technical solutions: The present application discloses a method for preparing polyester amide by one-pot alcoholysis of PA6, characterized in that it comprises the following steps: The PA6 raw material, dihydric alcohol and catalyst are uniformly mixed, and alcoholysis reaction is carried out to obtain alcoholysis product as small molecules or oligomer intermediates with a molecular weight <5000 g / mol, then polymerizable monomers are added, and then melt polycondensation is carried out to obtain polyester amide PEA; wherein the polymerizable monomers are dihydric acid or its corresponding anhydride or ester required for preparing polyester amide.

[0008] The application provides a disruptive waste PA6 upgrading recycling path, compared with a traditional technology which needs high temperature and high pressure and can only degrade and recycle monomers, the core advantage of the method is the efficient and high-value "one-step" in-situ upgrading and reconstruction capability. Specifically, the application initiatively performs precise alcoholysis on waste PA6 (such as fishing nets and textiles) under normal pressure conditions, using dihydric alcohol as a green reaction medium and ring-opening agent, and using a catalyst as a repolymerization catalyst and also as a depolymerization catalyst, and efficiently converts the waste PA6 into amide oligomers (such as amino alcohol and amide diol) containing active end groups. Most importantly, the oligomer intermediates generated in the process do not need any complex separation and purification steps, nor do they need the addition of a secondary catalyst, and the polymerizable monomers (such as diacids or their corresponding anhydrides or esters) required for preparing polyester amides can be directly added in the same reaction system, and through a precisely controlled esterification-polycondensation reaction, the direct synthesis of high-performance and degradable polyester amides (PEA) from waste PA6 is realized.

[0009] The PA6 raw material used in the application is mainly derived from nylon waste such as granules, fibers, films and powders, and is specifically derived from one or more of waste fishing nets, gears, ropes and nylon clothes. For example, it includes one of PA6 granules, PA6 offcuts, PA6 waste plastics and PA6 waste fibers.

[0010] Further, the dihydric alcohol is a straight-chain hydroxyl dihydric alcohol, including but not limited to one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol; preferably one of ethylene glycol, 1,4-butanediol and 1,6-hexanediol.

[0011] Further, the catalyst is selected from one of germanium-based catalysts, antimony-based catalysts and titanium-based catalysts; preferably one of germanium dioxide, diantimony trioxide, antimony acetate, antimony ethylene glycol, tetrabutyl titanate, tetraisopropyl titanate, titanium-silicon composite catalyst and titanium-alcohol complex catalyst; more preferably tetrabutyl titanate and titanium-alcohol complex catalyst. The catalyst selected in the application can catalyze PA6 alcoholysis and also be used in the subsequent repolymerization process, and the subsequent repolymerization does not need to add a catalyst again.

[0012] Furthermore, the polymerizable monomer is selected from one of succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, fumaric acid, maleic acid, terephthalic acid, phthalic acid, cyclohexanedicarboxylic acid, furandicarboxylic acid, succinic anhydride, glutaric anhydride, adipic anhydride, maleic anhydride, trimellitic anhydride, phthalic anhydride, pyromellitic dianhydride, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelic acid, dimethyl octanoate, dimethyl azelaic acid, dimethyl sebacate, dimethyl terephthalate, dimethyl phthalate, dimethyl cyclohexanedicarboxylic acid, and dimethyl furandicarboxylic acid; preferably succinic acid or adipic acid.

[0013] Furthermore, the amount of catalyst added is controlled at 0.05~1.5 wt% of PA6 raw material; for example, the amount of catalyst added is controlled at 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, 0.15 wt% of PA6 raw material, etc.

[0014] Furthermore, the mass ratio of the diol to PA6 raw material is 10:1 to 1:10; preferably 4:1 to 1:3. If the ratio of the diol to PA6 raw material is too low, the system viscosity will be too high; if the ratio of the diol to PA6 raw material is too high, the alcoholysis efficiency will be reduced.

[0015] Furthermore, the alcoholysis reaction temperature is 160~250℃, preferably 200~210℃. Excessively high alcoholysis temperatures can lead to side reactions such as diol cyclization and deoxygenation, affecting subsequent polymerization efficiency and the properties of the polymerized product. Insufficient alcoholysis temperatures result in incomplete alcoholysis of PA6, leading to excessively long and uneven oligomer segments, resulting in unstable properties of the subsequent polymerized product and excessively slow degradation of the polymerized polyesteramide. The alcoholysis reaction time is 2~10 h, preferably 4~6 h. Too short a time results in incomplete depolymerization, while too long a time leads to high energy consumption and increased byproducts.

[0016] Furthermore, the molar ratio of the diol to the polymerizable monomer is 1.2 to 2.5:1; exemplaryly, the molar ratio of the diol to the polymerizable monomer can be 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, etc.

[0017] Furthermore, the re-aggregation includes: First, the alcoholysis products and polymerizable monomers are subjected to an esterification reaction at a certain temperature until the amount of small molecules collected at the reactor overflow point reaches more than 80% of the theoretical value or the overflow area drops below 80 °C. Then, the temperature is raised, and a polycondensation reaction is carried out under vacuum conditions. The small molecules vary depending on the type of polymerizable monomer. When the polymerizable monomer is an acid, the small molecule is water, and the theoretical water overflow amount = 2 × the number of moles of the diacid. When the polymerizable monomer is an ester, the small molecule is methanol, and the theoretical methanol overflow amount = 2 × the number of moles of the ester. When the polymerizable monomer is an anhydride, no small molecules are produced, and the endpoint of the esterification reaction can be determined by the overflow area dropping below 80 °C.

[0018] Under the above-mentioned alcoholysis conditions, analysis of the PA6 alcoholysis products revealed a significant presence of a 3300 cm⁻¹ region in the infrared spectra of the oligomers. -1 (NH), 1635 cm -1 (C=O, amide I band) and 1050 cm -1 (CO, hydroxyl) absorption peak. 1 The 1H NMR (CF3COOD solvent) spectrum also showed chemical shifts attributed to -CH2OH (3.5 ppm) and -NH- (7.8 ppm). This indicates that during alcoholysis, the amide bond of PA6 breaks under the action of the diol and catalyst, generating linear or cyclic oligomers. The main structures include: N-(6-hydroxyhexyl)caprolactam, bi-hydroxy-terminated amide diols (such as HO-(CH2)m-NHCO-(CH2)n-OH), cyclic dimers, trimers, etc., and their molecular weight is M as determined by GPC. n =500~5000 g / mol, PDI<2.0, proving that it is an oligomer rather than a monomer.

[0019] Furthermore, the esterification reaction is carried out at a temperature of 200-220°C for 1-3 hours. The entire esterification process is conducted with mechanical stirring at 100-500 rpm to prevent localized overheating. Note that no vacuum is applied during the esterification process to prevent loss of the diol.

[0020] Furthermore, the polycondensation reaction includes a low-vacuum reaction stage and a high-vacuum reaction stage, and the entire polycondensation reaction takes 2 to 6 hours. The vacuum level of the low vacuum reaction stage is 2000-5000 Pa, and the temperature of the low vacuum reaction stage is 210-230℃. The vacuum level in the high-vacuum reaction stage is 50~200 Pa, and the temperature in the high-vacuum reaction stage is 230~250℃. As the polymerization time proceeds, a significant increase in product viscosity can be observed. Stirring is stopped when the stirrer torque reaches 30 N·m. For different application scenarios, further post-processing can be performed after the polymerization product reaches the target viscosity, for example: adding solid-phase thickener (SSP): 180 ℃, nitrogen, 10~20 h, to M... n Increase the concentration to >80000 g / mol for use in spinning; heat stabilizers and light stabilizers can also be added to improve the polymer's weather resistance.

[0021] The above describes a novel route for the one-pot conversion of waste PA6 into high-strength, biodegradable polyesteramide via alcoholysis-polymerization. After alcoholysis, PA6 requires no product separation or catalyst addition; it can directly polycondense with polymerizable monomer molecules to form a new polyesteramide material with controllable structure and properties. Specifically, the structure and properties of the new polyesteramide material can be controlled through the following three aspects: 1) Adjusting the polyamide / polyester ratio to regulate the properties of PEA materials. Increasing the amide bond content increases the material's melting point (T0). m As the glass transition temperature (T) increases, the glass transition temperature (T) increases. g 1) Increased tensile strength and crystallinity; 2) By controlling the length of the PA6 molecular chain, i.e. the degree of depolymerization, the properties of PEA materials can be controlled. The longer the PA6 depolymerization time, the more complete the depolymerization, the more uniform the molecular chain structure of the PEA material obtained by subsequent polymerization, the stronger the flexibility, the closer the properties are to polyester, and the better the degradation performance; 3) By controlling the ratio of diol to polymerizable monomer, the properties of the material can be controlled. When the ratio of diol to polymerizable monomer increases, the amount of hydroxyl end capping increases, the molecular weight of the product decreases, but the flexibility increases.

[0022] To achieve the second objective mentioned above, the present invention adopts the following technical solution: This invention discloses a polyesteramide prepared by the method described above.

[0023] The beneficial effects of this invention are as follows: This invention develops a novel one-pot alcoholysis-polymerization process for waste PA6 plastics that eliminates the need for product separation and purification. This method enables the efficient direct synthesis of high-performance, biodegradable polyesteramide (PEA) from waste PA6, significantly reducing production costs and improving efficiency.

[0024] The method provided by this invention mainly consists of two parts: alcoholysis and repolymerization. In the alcoholysis reaction, waste PA6 raw materials from different sources are reacted with diols and catalysts, realizing the recycling and reuse of waste PA6. Simultaneously, the selected catalyst can participate in both the alcoholysis reaction and the subsequent repolymerization reaction, eliminating the need for a secondary catalyst. By controlling the alcoholysis reaction conditions, the composition distribution of the alcoholysis products (i.e., oligomers) can be precisely controlled, providing conditions for the subsequent preparation of multifunctional polyesteramides. After the alcoholysis reaction is completed, a repolymerization process is carried out. By repolymerizing with different polymerizable monomers, novel polyesteramides can be prepared. Attached Figure Description

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0026] Figure 1 The change in molecular weight of the alcoholysis product with reaction time is shown in Example 1.

[0027] Figure 2 The stress-strain curve of the PEA prepared in Example 1 is shown.

[0028] Figure 3 The diagram shows the weight loss of PEA prepared in Example 1 after enzymatic hydrolysis. Detailed Implementation

[0029] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1 A novel method for preparing biodegradable PEA by alcoholysis of waste nylon 6. The specific process includes the following steps: 28.3g of waste nylon 6 plastic, 45g of 1,4-butanediol, and 0.25g of tetrabutyl titanate catalyst were added to a 500mL three-necked flask and heated to 200℃ with continuous mechanical stirring at 350 rpm for 5 hours of alcoholysis. After alcoholysis, 36.5g of 1,6-adipic acid was added and esterified at 200℃ for 3 hours. Calculations showed that the water yield reached more than 80% of the theoretical value. After esterification, the temperature was raised to 220℃, and a low vacuum (3000 Pa) was applied to remove unreacted 1,4-butanediol. After all the 1,4-butanediol was removed, the temperature was further raised to 240℃, and a high vacuum (50 Pa) was applied for polycondensation. As the polycondensation progressed, a significant increase in product viscosity was observed. Stirring was stopped when the stirrer torque reached 30 N·m, the vacuum was released, and the product was discharged, yielding polyesteramide, designated PEA-50.

[0031] Figure 1 The changes in molecular weight of the alcoholysis products with reaction time are shown under the experimental conditions of this embodiment. As the alcoholysis time increased from 1 hour to 10 hours, the molecular weight of the products gradually decreased from 12400 g / mol to 389 g / mol, while the molecular weight distribution (PDI) increased from 1.3 to 3.3. This result indicates that as the reaction proceeds, the PA6 molecular chains undergo depolymerization and breakage, generating short-chain oligomers of varying lengths, and the polydispersity of the products increases accordingly.

[0032] Example 2 A novel method for preparing biodegradable PEA by alcoholysis of waste nylon 6. The specific process includes the following steps: 42.3g of waste nylon 6 plastic, 67g of 1,4-butanediol, and 0.25g of tetrabutyl titanate catalyst were added to a 500mL three-necked flask and heated to 200℃ with continuous mechanical stirring at 350 rpm for 5 hours of alcoholysis. After alcoholysis, 36.5g of 1,6-adipic acid was added and esterified at 200℃ for 3 hours. Calculations showed that the water yield reached more than 80% of the theoretical value. After esterification, the temperature was raised to 220℃, and a low vacuum (3000 Pa) was applied to remove unreacted 1,4-butanediol. After all the 1,4-butanediol was removed, the temperature was further raised to 240℃, and a high vacuum (50 Pa) was applied for polycondensation. As the polycondensation progressed, a significant increase in product viscosity was observed. Stirring was stopped when the stirrer torque reached 30 N·m, the vacuum was released, and the product was discharged, yielding polyesteramide, designated PEA-60.

[0033] Example 3 A novel method for preparing biodegradable PEA by alcoholysis of waste nylon 6. The specific process includes the following steps: 65.9g of waste nylon 6 plastic, 105g of 1,4-butanediol, and 0.25g of tetrabutyl titanate catalyst were added to a 500mL three-necked flask and heated to 200℃ with continuous mechanical stirring at 350 rpm for 5 hours of alcoholysis. After alcoholysis, 36.5g of 1,6-adipic acid was added and esterified at 200℃ for 3 hours. Calculations showed that the water yield reached more than 80% of the theoretical value. After esterification, the temperature was raised to 220℃, and a low vacuum (3000 Pa) was applied to remove unreacted 1,4-butanediol. After all the 1,4-butanediol was removed, the temperature was further raised to 240℃, and a high vacuum (50 Pa) was applied for polycondensation. As the polycondensation progressed, a significant increase in product viscosity was observed. Stirring was stopped when the stirrer torque reached 30 N·m, the vacuum was released, and the product was discharged, yielding polyesteramide, designated PEA-70.

[0034] Example 4 A novel method for preparing biodegradable PEA by alcoholysis of waste nylon 6. The specific process includes the following steps: 113g of waste nylon 6 plastic, 180g of 1,4-butanediol, and 0.25g of tetrabutyl titanate catalyst were added to a 500mL three-necked flask and heated to 200℃ with continuous mechanical stirring at 350 rpm for 5 hours of alcoholysis. After alcoholysis, 36.5g of 1,6-adipic acid was added and esterified at 200℃ for 3 hours. Calculations showed that the water yield reached more than 80% of the theoretical value. After esterification, the temperature was raised to 220℃, and a low vacuum (3000 Pa) was applied to remove unreacted 1,4-butanediol. After all the 1,4-butanediol was removed, the temperature was further raised to 240℃, and a high vacuum (50 Pa) was applied for polycondensation. As the polycondensation progressed, a significant increase in product viscosity was observed. Stirring was stopped when the stirrer torque reached 30 N·m, the vacuum was released, and the product was discharged, yielding polyesteramide, designated PEA-80.

[0035] Example 5 A novel method for preparing biodegradable PEA by alcoholysis of waste nylon 6. The specific process includes the following steps: 254g of waste nylon 6 plastic, 405g of 1,4-butanediol, and 0.25g of tetrabutyl titanate catalyst were added to a 1000mL three-necked flask and heated to 200℃ with continuous mechanical stirring at 350 rpm for 5 hours of alcoholysis. After alcoholysis, 36.5g of 1,6-adipic acid was added and esterified at 200℃ for 3 hours. Calculations showed that the water yield reached more than 80% of the theoretical value. After esterification, the temperature was raised to 220℃, and a low vacuum (3000 Pa) was applied to remove unreacted 1,4-butanediol. After all the 1,4-butanediol was removed, the temperature was further raised to 240℃, and a high vacuum (50 Pa) was applied for polycondensation. As the polycondensation progressed, a significant increase in product viscosity was observed. Stirring was stopped when the stirrer torque reached 30 N·m, the vacuum was released, and the product was discharged, yielding polyesteramide, designated PEA-90.

[0036] PEA material property characterization results (1) Characterization of PEA mechanical properties PEA was used to prepare standard test strips using an injection molding machine. The effective dimensions of these strips were (25±1)×(4.0±0.4)×(2.0±0.2) mm. 3 The mass is 1.5-2.0 g. The injection temperature of PEA is set to 180-255℃, the mold temperature to 30-110℃, the injection time to 25 s, the injection pressure to 500-800 bar, and the holding time to 30 s.

[0037] Mechanical property testing (samples were standard tensile specimens stored at room temperature for seven days): The testing environment temperature was 25℃, and the tensile rate was 100 mm / min. To ensure the accuracy of the results, the average value ± standard deviation of three parallel samples was used as the measurement result. The tensile strength and elongation at break of PEA obtained through testing are as follows: Figure 2 As shown in Table 1, the tensile strength of PEA is 30-59 MPa, and the elongation at break is 322-722%. It exhibits excellent overall mechanical properties.

[0038] Table 1

[0039] (2) Optical properties of PEA The PEA-50 samples prepared in Example 1 were cast and then tested using a haze meter. The results showed that the light transmittance of the samples was all above 91%, and the haze was all below 16. They exhibited good transparency and excellent optical performance.

[0040] (3) PEA degradation performance test The samples prepared in Examples 1-5 were subjected to accelerated degradation tests in an enzymatic hydrolysis environment, and compared with biodegradable polyesters in PBS and PBAT. The enzymatic hydrolysis environment consisted of 5 mg / mL *Thermophyton floccosum* lipase (lipase TL), 1 mg / mL *Aspergillus niger* lipase, and 1 mg / mL *Aspergillus oryzae* lipase, at an ambient temperature of 50°C. The weight loss results are as follows: Figure 3 As shown, after 14 days of degradation, the highest weight loss rate of PEA-50 in Example 1 reached 54%, which exceeded that of PBAT and was close to the degradation level of PBS.

[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. Process for the preparation of polyester amides from PA6 alcoholysis in one pot, characterized in that, The method comprises the following steps: The PA6 raw material, dihydric alcohol and catalyst are mixed uniformly to carry out alcoholysis reaction, to obtain alcoholysis product as small molecule or oligomer intermediate with molecular weight <5000 g / mol, then polymerizable monomer is added, and then melt polycondensation is carried out to obtain polyester amide PEA; The polymerizable monomer is a diacid or its corresponding anhydride or ester required for preparing polyester amide.

2. The method of claim 1, wherein, The PA6 raw material comprises one of PA6 pure pellets, PA6 production offcuts and PA6 waste plastics; The dihydric alcohol is a linear terminal hydroxyl dihydric alcohol selected from one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol; The catalyst is selected from one of germanium catalyst, antimony catalyst and titanium catalyst; The polymerizable monomer is selected from one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, fumaric acid, maleic acid, terephthalic acid, phthalic acid, cyclohexane dicarboxylic acid, furan dicarboxylic acid, succinic anhydride, glutaric anhydride, adipic anhydride, maleic anhydride, trimellitic anhydride, phthalic anhydride, pyromellitic dianhydride, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate, dimethyl azelate, dimethyl sebacate, dimethyl terephthalate, dimethyl phthalate, dimethyl cyclohexane dicarboxylate and dimethyl furan dicarboxylate.

3. The method of claim 2, wherein, The dihydric alcohol is selected from one of ethylene glycol, 1,4-butanediol and 1,6-hexanediol; The catalyst is selected from one of germanium dioxide, diantimony trioxide, antimony acetate, ethylene glycol antimony, tetrabutyl titanate, tetraisopropyl titanate, titanium-silicon composite catalyst and titanium-alcohol complex catalyst; The polymerizable monomer is selected from succinic acid or adipic acid.

4. The method of claim 1, wherein, The amount of the catalyst is controlled to be 0.05-1.5wt% of the PA6 raw material; The mass ratio of the dihydric alcohol to the PA6 raw material is 10:1-1:10; Preferably, the mass ratio of the dihydric alcohol to the PA6 raw material is 4:1-1:

3.

5. The method of claim 1, wherein, The temperature of the alcoholysis reaction is 160-250℃, and the time of the alcoholysis reaction is 2-10 h; Preferably, the temperature of the alcoholysis reaction is 200-210℃, and the time of the alcoholysis reaction is 4-6 h.

6. The method of claim 1, wherein, The molar ratio of the dihydric alcohol to the polymerizable monomer is 1.2-2.5:

1.

7. The method of claim 1, wherein, The re-polymerization comprises: The alcoholysis product and the polymerizable monomer are first subjected to esterification reaction at a certain temperature until the overflow amount of small molecule substance collected at the overflow outlet of the reactor reaches more than 80% of the theoretical value or the overflow outlet area is reduced to below 80℃, then the temperature is immediately increased, and the polycondensation reaction is carried out under vacuum condition.

8. The method of claim 7, wherein, The temperature of the esterification reaction is 200-220℃, and the time of the esterification reaction is 1-3 h.

9. The method of claim 7, wherein, The polycondensation reaction comprises low vacuum reaction stage and high vacuum reaction stage in sequence, and the time of the whole polycondensation reaction is 2-6 h; The vacuum degree of the low vacuum reaction stage is 2000-5000 Pa, and the temperature of the low vacuum reaction stage is 210-230℃; The high vacuum reaction stage has a vacuum degree of 50-200 Pa, and a temperature of 230-250℃.

10. Polyester amide characterized in that, Prepared by the method of any one of claims 1-9.

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