Uvioresistant high-performance nylon fiber and preparation method thereof

Abstract

The application relates to the technical field of chemical fiber manufacturing, and discloses an ultraviolet-resistant and aging-resistant high-performance polyamide fiber and a preparation method thereof. The fiber is composed of a polyamide 6 matrix and an enzymatic hydrolysis lignin-oxidized graphene nanohybrid. The preparation method comprises the following steps: grafting modified enzymatic hydrolysis lignin and oxidized graphene to prepare a nanohybrid, and then in-situ polymerizing and melt spinning with caprolactam. The synergistic effect of the nanohybrid and the in-situ polymerization process are utilized, the problems of easy agglomeration and migration of the additive are solved, and the ultraviolet resistance, aging resistance and mechanical modulus of the fiber are improved.

Description

Technical Field

[0001] This invention relates to the field of chemical fiber manufacturing technology, and discloses a high-performance nylon fiber with UV resistance and aging resistance and its preparation method. Background Technology

[0002] Currently, UV-resistant modification of nylon fibers is mainly achieved by adding inorganic UV shielding agents or organic UV absorbers. Inorganic UV shielding agents, such as nano-titanium dioxide or zinc oxide, are usually directly mixed into the polymer matrix. Due to the high surface energy of inorganic particles, they are prone to agglomeration in the matrix. This agglomeration not only reduces shielding efficiency but also leads to clogging of the spinning components, and the hard particles become stress concentration points, thereby reducing the mechanical properties of the fiber. Another common method is to add organic UV absorbers or hindered amine light stabilizers. Although these small molecule auxiliaries have good initial absorption effects, their heat resistance is poor. In the high-temperature environment of nylon fiber melt spinning, small molecule auxiliaries are prone to decomposition or volatilization. In addition, their limited compatibility with the matrix leads to easy migration to the surface or leaching by solvents during use, making it impossible to maintain the UV resistance of the fiber for a long time.

[0003] The core technical problem faced by existing technologies is that, regardless of whether inorganic fillers or organic auxiliaries are used, it is difficult to simultaneously maintain the dispersion stability, heat resistance, and compatibility with the matrix of additives during the high-temperature processing and long-term use of nylon fibers. The agglomeration tendency of inorganic particles limits their addition amount and impairs fiber quality, while the thermal instability and migration of organic auxiliaries cause their UV resistance to decay rapidly over time, failing to meet the requirements of high-performance nylon fibers for long-term weather resistance and mechanical properties. Summary of the Invention

[0004] In view of the shortcomings of existing technologies, such as the tendency of inorganic ultraviolet shielding agents to agglomerate and reduce the mechanical properties of fibers, and the poor heat resistance and easy migration and precipitation of organic ultraviolet absorbers leading to weather resistance failure, this invention provides a high-performance nylon fiber with UV resistance and aging resistance and its preparation method.

[0005] To address the aforementioned technical problems, this invention provides a high-performance nylon fiber with UV resistance and aging resistance, comprising the following technical features: the nylon fiber is composed of the following components by weight percentage: 94.5%-99.7% nylon 6 matrix resin and 0.3%-5.5% enzymatically hydrolyzed lignin-graphene oxide nano-hybrid; the enzymatically hydrolyzed lignin-graphene oxide nano-hybrid is formed by esterified enzymatically hydrolyzed lignin and graphene oxide linked by amide bonds, and the enzymatically hydrolyzed lignin-graphene oxide nano-hybrid is uniformly dispersed in the nylon 6 matrix resin in the form of nanosheets, and the nano-hybrid forms a physical cross-linked network structure inside the matrix.

[0006] This invention utilizes the abundant phenolic hydroxyl structures in lignin molecules through enzymatic hydrolysis to capture ultraviolet free radicals and convert them into heat energy, while simultaneously leveraging the two-dimensional sheet structure of graphene oxide to physically block ultraviolet penetration. By grafting the two through amide bonds, the large specific surface area and surface functional groups of graphene oxide anchor the enzymatically hydrolyzed lignin, effectively preventing lignin aggregation. In nylon 6 matrix resin, uniformly dispersed nano-hybrids act as physical cross-linking points interspersed between polymer chains. This confined spatial structure not only fixes the UV-resistant components through steric hindrance, preventing their migration and loss, but also hinders the penetration of oxygen and ultraviolet light into the fiber interior through the labyrinth effect of the nanosheets, thereby synergistically improving the fiber's UV resistance and aging resistance at both the molecular and aggregated levels.

[0007] Furthermore, in the above technical solution, the esterified enzymatic hydrolysate is prepared by esterification reaction of enzymatic hydrolysate with an acid anhydride containing carbon-carbon double bonds in an organic solvent. The acid anhydride containing carbon-carbon double bonds is maleic anhydride or itaconic anhydride. The molar ratio of the enzymatic hydrolysate to the acid anhydride containing carbon-carbon double bonds is 1:2 to 1:6. The temperature of the esterification reaction is 80°C to 120°C.

[0008] In practice, enzymatically hydrolyzed lignin is modified by introducing anhydrides containing carbon-carbon double bonds, thereby introducing active functional groups such as carboxyl groups onto the lignin molecular chain. These active functional groups not only provide the necessary chemical bonding sites for subsequent amidation reactions with graphene oxide, but also change the polarity of the lignin molecule, improving its compatibility with the hydrophobic nylon 6 matrix and reducing microscopic defects caused by phase separation.

[0009] Furthermore, in the above technical solution, the carboxyl groups on the surface of the graphene oxide are connected to the active functional groups on the esterified enzymatically hydrolyzed lignin through a condensation reaction in the presence of a dehydrating condensing agent, wherein the dehydrating condensing agent is a mixture of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, and the condensation reaction is carried out at a temperature of 60°C to 80°C for a reaction time of 12 to 24 hours.

[0010] In practice, a dehydration condensation system composed of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is used to efficiently catalyze the dehydration condensation of carboxyl groups at the edge of graphene oxide with active functional groups on modified lignin, forming stable amide bonds. This covalent bond connection allows the enzymatically hydrolyzed lignin to grow firmly on the surface of graphene oxide sheets, preventing lignin molecules from detaching from the carrier during subsequent high-temperature melting processing and ensuring the structural stability of the nano-hybrid at high temperatures.

[0011] Furthermore, in the above technical solution, in the enzymatically hydrolyzed lignin-graphene oxide nanohybrid, the mass ratio of the esterified enzymatically hydrolyzed lignin to the graphene oxide is 2:1 to 8:1, the sheet diameter of the graphene oxide is 0.5 μm to 5 μm, the sheet thickness is 1 nm to 3 nm, and the average particle size of the nanohybrid is 50 nm to 200 nm.

[0012] In practice, controlling the mass ratio of lignin to graphene oxide and the sheet size of graphene oxide aims to optimize the steric hindrance and dispersion properties of the nano-hybrid. Specific ratios and sizes ensure that the graphene oxide sheets are fully intercalated or coated by enzymatically hydrolyzed lignin, avoiding recombination between graphene oxide sheets. Simultaneously, a suitable average particle size ensures good flowability and dispersibility of the hybrid in the polymer melt, reducing stress concentration points.

[0013] Furthermore, in the above technical solution, the nylon fiber further includes 0.1%-0.5% of a heat-resistant antioxidant, which is a compound of hindered phenolic antioxidant and phosphite antioxidant. The mass ratio of the hindered phenolic antioxidant to the phosphite antioxidant is 1:1 to 1:3. The heat-resistant antioxidant is uniformly coated on the surface of the enzymatically hydrolyzed lignin-graphene oxide nano-hybrid.

[0014] In practice, hindered phenolic antioxidants provide protons to capture free radicals generated by polymer degradation, while phosphite antioxidants decompose hydroperoxides; the combination of the two produces a synergistic antioxidant effect. By coating antioxidants onto the surface of nano-hybrids and using the hybrids as carriers, the volatilization of antioxidants during high-temperature spinning is reduced, and their distribution within the fiber matrix is ​​made more uniform, thus continuously protecting the polymer chains from breakage under thermo-oxidative conditions.

[0015] Furthermore, in the above technical solution, the intrinsic viscosity of the nylon 6 matrix resin is 2.4 dL / g to 3.2 dL / g, the fineness of the nylon fiber monofilament is 1.0 dtex to 5.0 dtex, the internal crystalline region size of the fiber is 3 nm to 6 nm, and the nano-hybrids are distributed at the interface between the amorphous region and the crystalline region of the nylon 6 matrix resin.

[0016] In practice, the matrix resin with a specific viscosity ensures that the polymer molecular chains have a suitable degree of entanglement, giving the fiber good spinnability. Nanoparticles distributed at the interface between the amorphous and crystalline regions act as heterogeneous nucleating agents, inducing nylon 6 to form a fine and uniform crystal structure. This interface distribution not only strengthens the grain boundary's resistance to crack propagation and improves the fiber's mechanical strength, but also prevents nanoparticles from disrupting the lattice integrity.

[0017] Furthermore, in the above technical solution, the present invention also provides a method for preparing high-performance nylon fiber with UV resistance and aging resistance, comprising the following steps: Step S1, esterifying enzymatically hydrolyzed lignin with acid anhydride under the action of a catalyst to obtain modified enzymatically hydrolyzed lignin; Step S2, mixing the modified enzymatically hydrolyzed lignin with graphene oxide dispersion, adding a dehydrating condensing agent to carry out a grafting reaction to prepare an enzymatically hydrolyzed lignin-graphene oxide nano-hybrid suspension; Step S3, mixing the nano-hybrid suspension with caprolactam monomer evenly, and carrying out an in-situ polymerization reaction under inert gas protection to obtain nylon 6 chips; Step S4, melt spinning the nylon 6 chips, and obtaining the nylon fiber after stretching and heat setting treatment.

[0018] In practice, the in-situ polymerization process organically combines the preparation of nano-hybrids with the polymerization process of nylon 6. In the early stage of caprolactam ring-opening polymerization, the nano-hybrids are uniformly dispersed in the monomer. As polymerization proceeds, the generated polymer molecular chains tightly encapsulate the nano-hybrids, achieving nanoscale uniform dispersion of nanoparticles in the matrix. This effectively overcomes the particle agglomeration problem that is difficult to solve in traditional melt blending methods, ensuring the full utilization of the functions of each component.

[0019] Furthermore, in the above technical solution, the catalyst in step S1 is p-toluenesulfonic acid, the anhydride is maleic anhydride, the reaction temperature is 90°C to 110°C, the reaction time is 4 hours to 8 hours, and after the reaction, the modified enzymatic hydrolyzed lignin is obtained by ethanol precipitation, centrifugation washing and vacuum drying, and the grafting rate of the modified enzymatic hydrolyzed lignin is 15% to 30%.

[0020] In practice, p-toluenesulfonic acid, as a potent protic acid catalyst, promotes the ring-opening of maleic anhydride and its esterification with lignin hydroxyl groups. Maintaining a reaction temperature between 90°C and 110°C ensures both a high reaction rate and grafting efficiency while avoiding high-temperature pyrolysis of lignin molecules. A grafting rate of 15% to 30% ensures sufficient active sites on the lignin molecular chain for subsequent reactions, while preserving a large number of benzene ring structures to maintain ultraviolet absorption capacity.

[0021] Furthermore, in the above technical solution, the solvent of the graphene oxide dispersion in step S2 is deionized water or N,N-dimethylformamide, the concentration of the graphene oxide dispersion is 1 mg / mL to 3 mg / mL, the mixing process is ultrasonic treatment with a power of 300W to 500W for 30 minutes to 60 minutes, and the grafting reaction is carried out in a constant temperature shaker with a rotation speed of 150 rpm to 200 rpm.

[0022] In practice, ultrasonic treatment utilizes the high shear force and microjets generated by cavitation to effectively exfoliate graphene oxide sheets, dispersing them uniformly in the solvent as single or few layers, thus increasing the reaction contact area. The oscillation of the constant-temperature shaker promotes the mass transfer of modified enzymatically hydrolyzed lignin molecules between the graphene oxide sheets, ensuring uniform grafting and preventing the re-aggregation of graphene oxide during the reaction process.

[0023] Furthermore, in the above technical solution, the in-situ polymerization reaction process in step S3 includes: first raising the temperature to 240°C to 250°C and holding the reaction under pressure for 2 to 3 hours, then raising the temperature to 250°C to 265°C and reducing the pressure to vacuum for 1 to 2 hours. In step S4, the temperature of each zone of the screw in the melt spinning process is 250°C to 270°C, the filtration accuracy of the spinning assembly is 20μm to 40μm, and the draw ratio is 3.0 to 3.5 times.

[0024] In practice, controlled segmented heating and vacuum processes ensured the full ring-opening polymerization of caprolactam monomers and the complete removal of water generated during the reaction, thereby obtaining high molecular weight polymers. The melt spinning parameters were matched to the rheological properties of the chips. A filtration precision of 20μm to 40μm effectively trapped any trace gel particles, protecting the spinneret from clogging. A draw ratio of 3.0 to 3.5 times promoted highly oriented crystallization of polymer macromolecules along the fiber axis, further enhancing the fiber's mechanical properties and dimensional stability.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. This invention prepares nano-hybrids by combining esterified enzymatically hydrolyzed lignin with graphene oxide, and introduces them into a nylon matrix using in-situ polymerization, thus solving the problems of additive dispersion and migration. The layered structure of graphene oxide prevents the aggregation of enzymatically hydrolyzed lignin, ensuring the uniform dispersion of the nano-hybrids in the matrix. The covalent bonds and physical network structure formed by in-situ polymerization fix the hybrids between polymer chains, preventing the loss of additives. This structure endows the fibers with a high UV protection factor and maintains a high tensile strength retention rate even after prolonged UV irradiation, achieving long-lasting UV resistance and aging resistance.

[0027] 2. The introduction of nano-hybrids in this invention enhances the mechanical properties of the fiber. Uniformly dispersed nanosheets form physical cross-linking points within the matrix, increasing the initial modulus of the fiber. Esterification modification improves the interfacial bonding between enzymatically hydrolyzed lignin and the nylon matrix, reducing the degree of yellowing caused by light exposure. The in-situ polymerization process ensures the stability of the heat-sensitive components during high-temperature processing, preventing decomposition and thus guaranteeing the quality of the finished fiber. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to embodiments. Those skilled in the art can reproduce the technical solution of the present invention and achieve its claimed technical effects based on the content disclosed in this specification. It should be noted that the following embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention. Any non-substantial improvements and adjustments made based on the core concept of the present invention should fall within the scope of protection of the present invention.

[0029] Example 1: This example provides a high-performance nylon fiber with UV resistance and aging resistance, which is composed of the following components by weight percentage: 96.5% nylon 6 matrix resin, 3.0% enzymatic hydrolyzed lignin-graphene oxide nano-hybrid, and 0.5% heat-resistant antioxidant.

[0030] In the enzymatically hydrolyzed lignin-graphene oxide nanohybrid, the mass ratio of esterified enzymatically hydrolyzed lignin to graphene oxide is 4:1. The heat-resistant antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of 1:1.

[0031] The preparation method of this nylon fiber is as follows:

[0032] Step S1: Mix enzymatically hydrolyzed lignin with maleic anhydride at a molar ratio of 1:4, add p-toluenesulfonic acid as a catalyst, and react at 100 degrees Celsius for 6 hours. After precipitation with ethanol, centrifugation, washing and vacuum drying, modified enzymatically hydrolyzed lignin with a grafting rate of 22% is obtained.

[0033] Step S2: The modified enzymatically hydrolyzed lignin was mixed with an aqueous dispersion of graphene oxide at a concentration of 2 mg / mL. A mixture of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine was added as a dehydrating condensing agent. The mixture was reacted in a constant temperature shaker at 70°C at a speed of 180 rpm for 18 hours to prepare an enzymatically hydrolyzed lignin-graphene oxide nanocomposite suspension.

[0034] Step S3: The above-mentioned nano-hybrid suspension is mixed evenly with caprolactam monomer, and an in-situ polymerization reaction is carried out under nitrogen protection. The temperature is first raised to 245 degrees Celsius and the reaction is carried out under pressure for 2.5 hours, and then the temperature is raised to 260 degrees Celsius and the reaction is carried out under reduced pressure and vacuum for 1.5 hours to obtain nylon 6 chips.

[0035] Step S4: The nylon 6 chips are melt-spun, the temperature of each zone of the screw is 260 degrees Celsius, the filtration accuracy of the spinning assembly is 30 micrometers, the draw ratio is 3.2 times, and the nylon fiber is obtained after heat setting treatment.

[0036] Example 2: The difference between this example and Example 1 is that the anhydride containing carbon-carbon double bonds is replaced with itaconic anhydride, the molar ratio of enzymatically hydrolyzed lignin to itaconic anhydride is 1:5, and the remaining components and preparation methods are the same as in Example 1.

[0037] Example 3: The difference between this example and Example 1 is that in the enzymatic hydrolyzed lignin-graphene oxide nanohybrid, the mass ratio of esterified enzymatic hydrolyzed lignin to graphene oxide is 2:1, and the remaining components and preparation methods are the same as in Example 1.

[0038] Example 4: The difference between this example and Example 1 is that in the enzymatic hydrolyzed lignin-graphene oxide nano-hybrid, the mass ratio of esterified enzymatic hydrolyzed lignin to graphene oxide is 8:1, and the remaining components and preparation methods are the same as in Example 1.

[0039] Example 5: The difference between this example and Example 1 is that the nylon fiber is composed of the following components by weight percentage: 96.7% nylon 6 matrix resin, 3.0% enzymatically hydrolyzed lignin-graphene oxide nano-hybrid, and 0.3% heat-resistant antioxidant. The heat-resistant antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of 1:3. The remaining preparation methods are the same as in Example 1.

[0040] Example 6: The difference between this example and Example 1 is that the nylon fiber is composed of the following components by weight percentage: 99.4% nylon 6 matrix resin, 0.5% enzymatically hydrolyzed lignin-graphene oxide nano-hybrid, and 0.1% heat-resistant antioxidant. The remaining preparation methods are the same as in Example 1.

[0041] Example 7: The difference between this example and Example 1 is that the nylon fiber is composed of the following components by weight percentage: 94.5% nylon 6 matrix resin, 5.5% enzymatically hydrolyzed lignin-graphene oxide nano-hybrid, and 0.5% heat-resistant antioxidant. The remaining preparation methods are the same as in Example 1.

[0042] Example 8: The difference between this example and Example 1 is that in step S2, the solvent for the graphene oxide dispersion is N,N-dimethylformamide, the ultrasonic treatment power is 500 watts, and the treatment time is 30 minutes. The remaining preparation methods are the same as in Example 1.

[0043] Example 9: The difference between this example and Example 1 is that the in-situ polymerization process in step S3 is as follows: first, the temperature is raised to 240 degrees Celsius and the reaction is carried out under pressure for 3 hours, then the temperature is raised to 250 degrees Celsius and the reaction is carried out under reduced pressure and vacuum for 2 hours. The remaining preparation methods are the same as in Example 1.

[0044] Example 10: The difference between this example and Example 1 is that the draw ratio in step S4 is 3.5 times. The rest of the preparation method is the same as in Example 1.

[0045] Comparative Example 1: The difference between this comparative example and Example 1 is that no enzymatic hydrolyzed lignin-graphene oxide nano-hybrid was added; only 3.0% of unmodified enzymatic hydrolyzed lignin was added. The remaining components and preparation methods are the same as in Example 1.

[0046] Comparative Example 2: This comparative example uses existing technology. The nylon fiber is composed of the following components by weight percentage: 97% nylon 6 matrix resin and 3% nano titanium dioxide. The preparation method is conventional melt blending spinning, and the other parameters are the same as in Example 1.

[0047] Comparative Example 3: The difference between this comparative example and Example 1 is that esterification modification was not performed in step S1; instead, enzymatically hydrolyzed lignin was directly mixed with graphene oxide without the addition of acid anhydrides and catalysts. The remaining preparation methods are the same as in Example 1.

[0048] Comparative Example 4: The difference between this comparative example and Example 1 is that: instead of in-situ polymerization, the enzymatic hydrolyzed lignin-graphene oxide nano-hybrid prepared in Example 1 was melt-blended with the finished nylon 6 chips through a twin-screw extruder and then spun. The remaining components and spinning parameters were the same as in Example 1.

[0049] Test method:

[0050] Ultraviolet Protection Factor (UPF) and Ultraviolet Transmittance: Tested according to the national standard "Evaluation of Ultraviolet Protection Performance of Textiles".

[0051] Aging resistance: The fiber was placed in a xenon lamp aging chamber and exposed to sunlight for 500 hours to test the retention rate of breaking strength.

[0052] Mechanical properties: The initial modulus of the fiber is tested, and the unit is centinewtons per deciter.

[0053] The test results are shown in Table 1.

[0054] Table 1 Performance test results of each embodiment and comparative example

[0055]

[0056] Results analysis:

[0057] The UPF values ​​of Examples 1 to 10 all exceeded 300, and the tensile strength retention rate was all above 85%, demonstrating excellent UV resistance and aging resistance. This is because enzymatically hydrolyzed lignin and graphene oxide formed a nano-hybrid through covalent bonds, which was uniformly dispersed in the nylon matrix. Lignin absorbs ultraviolet light and converts it into heat energy, while the graphene oxide sheets physically block ultraviolet light. The two work synergistically and form a physical cross-linked network inside the matrix, preventing the loss of additives.

[0058] In contrast, Comparative Example 1 used unmodified lignin. Due to the poor compatibility between lignin and the matrix, uneven dispersion, and easy migration, the UPF value was as low as 150, and the strength retention rate was only 65%.

[0059] Comparative Example 3 omitted the esterification modification step, which resulted in lignin not being able to be effectively grafted onto graphene oxide, destroying the hybrid structure and reducing dispersibility, thus leading to significantly lower UV resistance and aging resistance compared to Example 1.

[0060] Comparative Example 4 used melt blending instead of in-situ polymerization, which resulted in poor dispersion of the nano-hybrid in the matrix and weak interfacial bonding. Its UPF value and strength retention rate were lower than those of Example 1.

[0061] The initial modulus of Examples 1 to 10 is generally higher than 35 centine Newtons per decibel, with Example 10 reaching 40.5 centine Newtons per decibel. This is because the nano-hybrids act as physical crosslinking points and heterogeneous nucleating agents in the matrix, enhancing the intermolecular forces, restricting chain segment movement, and thus improving the rigidity of the fiber.

[0062] Although Comparative Example 2 used conventional inorganic nano-titanium dioxide, its initial modulus was only 32 centinewtons / dtex, and its fracture strength retention rate was low. This is because inorganic particles tend to agglomerate, forming stress concentration points in the matrix. This not only fails to effectively enhance mechanical properties but also easily leads to fiber structure damage under the influence of external environments.

[0063] Comparing Examples 3 and 4 with Example 1, the performance remained at a high level when the ratio of lignin to graphene oxide varied within the range of 2:1 to 8:1, indicating that this ratio range has good process adaptability. In Example 7, the hybrid content was increased to 5.5%, further optimizing the performance. In Example 6, the hybrid content was 0.5%, and although the performance decreased slightly, it was still better than the comparative example, demonstrating that the present invention can still play an effective role at low addition levels.

[0064] In summary, this invention, through specific nano-hybrid structure design and in-situ polymerization process, successfully solves the problems of poor dispersion, easy migration, poor heat resistance, and damage to fiber mechanical properties in the prior art of anti-UV additives, and achieves a unity of anti-UV, anti-aging, and high performance.

Claims

1. A high performance anti-UV ageing nylon fibre, characterised in that, The nylon fiber is composed of the following components by weight percentage: Nylon 6 matrix resin 94.5%-99.7%, enzymatically hydrolyzed lignin-graphene oxide nano-hybrids 0.3%-5.5%; The enzymatically hydrolyzed lignin-graphene oxide nanohybrid is formed by esterified enzymatically hydrolyzed lignin and graphene oxide linked by amide bonds, and the enzymatically hydrolyzed lignin-graphene oxide nanohybrid is uniformly dispersed in the nylon 6 matrix resin in the form of nanosheets, and the nanohybrid forms a physical cross-linked network structure inside the matrix.

2. The anti-UV and ageing resistant high performance nylon fibre as claimed in claim 1, wherein, The esterified enzymatic hydrolysate is prepared by esterification of enzymatic hydrolysate with an anhydride containing carbon-carbon double bonds in an organic solvent. The anhydride containing carbon-carbon double bonds is maleic anhydride or itaconic anhydride. The molar ratio of the enzymatic hydrolysate to the anhydride containing carbon-carbon double bonds is 1:2 to 1:

6. The temperature of the esterification reaction is 80°C to 120°C.

3. The UV-resistant and aging-resistant high-performance nylon fiber according to claim 1, characterized in that, The carboxyl groups on the surface of the graphene oxide are connected to the active functional groups on the esterified enzymatically hydrolyzed lignin via a condensation reaction in the presence of a dehydrating condensing agent, which is a mixture of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine. The condensation reaction is carried out at a temperature of 60°C to 80°C for 12 to 24 hours.

4. The UV-resistant and aging-resistant high-performance nylon fiber according to claim 1, characterized in that, In the enzymatically hydrolyzed lignin-graphene oxide nanohybrid, the mass ratio of the esterified enzymatically hydrolyzed lignin to the graphene oxide is 2:1 to 8:1, the sheet diameter of the graphene oxide is 0.5 μm to 5 μm, the sheet thickness is 1 nm to 3 nm, and the average particle size of the nanohybrid is 50 nm to 200 nm.

5. The UV-resistant and aging-resistant high-performance nylon fiber according to claim 1, characterized in that, The nylon fiber also includes 0.1%-0.5% of a heat-resistant antioxidant, which is a compound of hindered phenolic antioxidant and phosphite antioxidant. The mass ratio of the hindered phenolic antioxidant to the phosphite antioxidant is 1:1 to 1:

3. The heat-resistant antioxidant is uniformly coated on the surface of the enzymatically hydrolyzed lignin-graphene oxide nanocomposite.

6. The UV-resistant and aging-resistant high-performance nylon fiber according to claim 1, characterized in that, The intrinsic viscosity of the nylon 6 matrix resin is 2.4 dL / g to 3.2 dL / g, the fineness of the nylon fiber monofilament is 1.0 dtex to 5.0 dtex, the internal crystalline region size of the fiber is 3 nm to 6 nm, and the nano-hybrids are distributed at the interface between the amorphous region and the crystalline region of the nylon 6 matrix resin.

7. A method for preparing high-performance nylon fiber with UV resistance and aging resistance, characterized in that, Includes the following steps: Step S1: The enzymatically hydrolyzed lignin is esterified with acid anhydride under the action of a catalyst to obtain modified enzymatically hydrolyzed lignin. Step S2: Mix the modified enzymatic hydrolyzed lignin with the graphene oxide dispersion, add a dehydrating condensing agent to carry out a grafting reaction, and prepare an enzymatic hydrolyzed lignin-graphene oxide nano-hybrid suspension. Step S3: The nano-hybrid suspension is mixed evenly with caprolactam monomer and in-situ polymerization is carried out under inert gas protection to obtain nylon 6 chips. Step S4: The nylon 6 chips are melt-spun, and then drawn and heat-set to obtain the nylon fiber.

8. The preparation method according to claim 7, characterized in that, The catalyst in step S1 is p-toluenesulfonic acid, the anhydride is maleic anhydride, the reaction temperature is 90°C to 110°C, the reaction time is 4 hours to 8 hours, and after the reaction is completed, the modified enzymatic hydrolyzed lignin is obtained by ethanol precipitation, centrifugation washing and vacuum drying. The grafting rate of the modified enzymatic hydrolyzed lignin is 15% to 30%.

9. The preparation method according to claim 7, characterized in that, The solvent for the graphene oxide dispersion in step S2 is deionized water or N,N-dimethylformamide, the concentration of the graphene oxide dispersion is 1 mg / mL to 3 mg / mL, the mixing process is performed by ultrasonic treatment with a power of 300W to 500W for 30 to 60 minutes, and the grafting reaction is carried out in a constant temperature shaker at a speed of 150 rpm to 200 rpm.

10. The preparation method according to claim 7, characterized in that, The in-situ polymerization process in step S3 includes: First, raise the temperature to 240℃ to 250℃ and hold the pressure for 2 to 3 hours. Then, raise the temperature to 250℃ to 265℃ and reduce the pressure for 1 to 2 hours. In step S4, the temperature of each zone of the screw in the melt spinning process is 250℃ to 270℃. The filtration accuracy of the spinning assembly is 20μm to 40μm, and the draw ratio is 3.0 to 3.5 times.

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