Anti-ultraviolet polylactic acid fiber as well as preparation method and application thereof
By introducing carbazole groups and modifying zinc oxide into polylactic acid (PLA) fibers, the problem of poor UV resistance of PLA fibers has been solved, enabling their widespread application in outdoor textiles.
Patent Information
- Application Number
- CN202511908972.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-02-06
AI Technical Summary
Polylactic acid (PLA) fibers have low absorption and high transmittance under ultraviolet radiation, which limits their application in outdoor textiles.
By introducing carbazole groups and modifying zinc oxide into polylactic acid fibers, the carbazole groups absorb ultraviolet light and release it in the form of fluorescence, while the zinc oxide reflects ultraviolet light. Combined with plasticizers, the UV resistance is improved.
It significantly reduces UV transmittance, enhances the fiber's UV resistance, delays aging, and expands its application in outdoor textiles.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polylactic acid fiber technology, specifically relating to an anti-ultraviolet polylactic acid fiber, its preparation method, and its application. Background Technology
[0002] Polylactic acid (PLA) fiber is a biodegradable fiber widely used in the textile industry. Due to its high crystallinity and orientation, PLA fiber exhibits high heat resistance and strength. However, the molecular structure of PLA fiber contains numerous C-C and CH bonds and lacks aromatic rings. It generally does not absorb light with wavelengths greater than 290 nm. When exposed to sunlight, PLA fiber exhibits low UV absorption and high transmittance, which limits its application in textiles that require long-term outdoor exposure. Summary of the Invention
[0003] This invention provides an anti-ultraviolet polylactic acid fiber, its preparation method, and its application, which can solve the problem of poor anti-ultraviolet performance of polylactic acid fibers in the prior art.
[0004] The objective of this invention can be achieved through the following technical solutions: A UV-resistant polylactic acid fiber, wherein the polylactic acid fiber is prepared by melt spinning a mixture of modified polylactic acid chips and a plasticizer; The modified polylactic acid chips, by weight, comprise the following raw materials: 60-80 parts of polylactic acid, 15-25 parts of grafted polylactic acid, and 5-10 parts of modified zinc oxide; The grafted modified polylactic acid is a product obtained by introducing carbazole groups into the polylactic acid molecular chain through free radical graft polymerization of polylactic acid and vinyl carbazole. The modified zinc oxide is zinc oxide loaded with polydopamine and grafted with lipoic acid.
[0005] When exposed to sunlight, polylactic acid (PLA) fibers have low UV absorption, resulting in high UV transmittance. For PLA products used outdoors, UV light is harmful to human health; therefore, it is necessary to improve PLA's UV resistance. Carbazole groups, which absorb UV light, can endow PLA with excellent UV resistance and improve UV absorption. Utilizing the unsaturated double bonds on vinylcarbazole, carbazole groups are grafted onto the PLA molecular chain via free radical graft polymerization. The grafted PLA with introduced carbazole groups can be uniformly mixed in the PLA matrix and remains stable during PLA melt processing. The carbazole groups absorb UV light and then release it through fluorescence, thereby reducing UV transmittance. However, graft-modified polylactic acid (PLA) only improves UV resistance by absorbing ultraviolet light, which has a single effect and certain limitations. Zinc oxide is a commonly used inorganic UV shielding agent that can effectively reflect ultraviolet rays, reduce UV transmittance, and improve the UV resistance of PLA fiber products. Using zinc oxide as a carrier, polydopamine particles are formed on the surface of zinc oxide through dopamine self-polymerization. The phenolic hydroxyl groups on the surface of polydopamine react with the highly active disulfide bonds of lipoic acid to crosslink. Lipoic acid is covalently grafted onto the surface of polydopamine particles. The modified zinc oxide prepared has active groups introduced into the polydopamine on its surface, which can form hydrogen bonds with PLA groups, enhancing the dispersibility of modified zinc oxide in the matrix. Lipoic acid is a highly effective antioxidant that can scavenge free radicals generated during the UV irradiation of PLA and slow down the aging process.
[0006] Furthermore, the preparation method of the grafted modified polylactic acid includes the following steps: A1. Dissolve polylactic acid in tetrahydrofuran, add vinylcarbazole and initiator benzoyl peroxide under nitrogen atmosphere, and stir until homogeneous to obtain a reaction solution; A2. The polymerization reaction was carried out under nitrogen protection. After the reaction was completed, the product was added dropwise to deionized water under constant stirring to obtain a solid product. A3. After washing with deionized water and diethyl ether in sequence, the grafted polylactic acid is dried under vacuum to constant weight to obtain the grafted modified polylactic acid.
[0007] Benzoyl peroxide, as an initiator, produces free radicals under heating conditions. These free radicals extract hydrogen from the polylactic acid (PLA) molecular chain, forming carbon free radicals on the PLA molecular chain. These carbon free radicals then undergo free radical addition with the unsaturated olefin bonds on vinylcarbazole, introducing carbazole groups into the side chain.
[0008] Furthermore, the mass ratio of polylactic acid to vinylcarbazole is 1:0.16-0.20.
[0009] Furthermore, the concentration of the initiator benzoyl peroxide in the reaction solution is 3-5 mmol / L.
[0010] Furthermore, the heating polymerization reaction is carried out at a temperature of 60-80°C for a duration of 6-10 hours.
[0011] Furthermore, the preparation method of the modified zinc oxide includes the following steps: B1. Disperse zinc oxide in a Tris-HCl buffer solution with a pH of 8-9 to obtain a zinc oxide dispersion; B2. While stirring, add dopamine and lipoic acid to the zinc oxide dispersion, and mix well to obtain the reaction solution; B3. The reaction solution is stirred at 40-50℃ for 4-8 hours, centrifuged, washed with water, and then vacuum dried to obtain modified zinc oxide.
[0012] In the presence of zinc oxide, dopamine in alkaline solution undergoes oxidative polymerization on the surface of zinc oxide to form polydopamine. Simultaneously, the disulfide bonds in lipoic acid open and react with phenolic hydroxyl groups to crosslink, thereby grafting lipoic acid onto polydopamine.
[0013] Furthermore, the concentration of zinc oxide in the zinc oxide dispersion is 2-3 g / L.
[0014] Furthermore, the mass ratio of dopamine to zinc oxide is 1-7:10; The molar ratio of lipoic acid to dopamine is 0.1-0.6:1.
[0015] This invention also provides a method for preparing UV-resistant polylactic acid (PLA) fibers, which includes the following steps: Step 1: Prepare the raw materials for modified polylactic acid chips according to the proportion, put the raw materials into a screw extruder for melt extrusion, cooling, and granulation to obtain modified polylactic acid chips; Step 2: After drying the modified polylactic acid chips, add plasticizer and mix to form a mixture, then add it to a melt spinning device to spin and obtain nascent fibers; Step 3: After the nascent fibers are thermally stretched and thermally set, UV-resistant polylactic acid fibers are obtained.
[0016] Furthermore, the plasticizer is one of epoxidized soybean oil, tributyl citrate, and acetylated tributyl citrate, and the plasticizer is 1-3% of the mass of modified polylactic acid chips.
[0017] The present invention also provides an application of UV-resistant polylactic acid fiber, as described above, for the preparation of outdoor textile products.
[0018] The beneficial effects of this invention are: This invention uses modified polylactic acid (PLA) chips as the main material for preparing PLA fibers. The modified PLA chips are made by adding grafted modified PLA and modified zinc oxide to a PLA matrix. The grafted modified PLA and modified zinc oxide exhibit good compatibility within the PLA matrix. Utilizing the synergistic effect of organic UV absorbers and inorganic UV shielding agents, the lipoic acid grafted onto the modified zinc oxide simultaneously scavenge free radicals generated during degradation. Through multiple mechanisms, the UV resistance of PLA fibers is enhanced, delaying UV degradation and aging, reducing UV transmittance, and expanding the application of PLA fibers in outdoor textiles. Detailed Implementation
[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0020] Example 1
[0021] Preparation of grafted modified polylactic acid: A1. Weigh polylactic acid to a concentration of 50 g / L and dissolve it in tetrahydrofuran. Weigh vinylcarbazole according to a mass ratio of polylactic acid to vinylcarbazole of 1:0.18. Under a nitrogen atmosphere, add vinylcarbazole and initiator benzoyl peroxide to the solution and stir until homogeneous to obtain a reaction solution. The concentration of initiator benzoyl peroxide in the reaction solution is 4 mmol / L.
[0022] A2. Under nitrogen protection, the reaction solution was heated to 80°C and the polymerization reaction was carried out at a constant temperature for 8 hours. After the reaction was completed, the product was added dropwise to deionized water with constant stirring to obtain a solid product.
[0023] A3. The solid product was washed with deionized water and diethyl ether three times each. After washing, it was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain grafted modified polylactic acid.
[0024] Preparation of modified zinc oxide: B1. Prepare a Tris-HCl buffer solution with a pH of 8.5. Weigh zinc oxide and add it to the Tris-HCl buffer solution at a concentration of 2.5 g / L. Stir and mix to obtain a zinc oxide dispersion.
[0025] B2. Prepare dopamine at a mass ratio of 4:10 to zinc oxide, and prepare lipoic acid at a mass ratio of 0.3:1 to dopamine. Add the prepared dopamine and lipoic acid to the zinc oxide dispersion while stirring, and mix well to obtain the reaction solution.
[0026] B3. The reaction solution was heated to 45℃ and stirred for 8 hours. After centrifugation, the precipitate was collected and washed three times with deionized water. After washing, it was placed in a vacuum drying oven and dried at 70℃ for 12 hours to obtain modified zinc oxide.
[0027] Preparation of polylactic acid fibers: Step 1: Prepare the raw materials for modified polylactic acid chips according to the following mass proportions: 70 parts polylactic acid, 20 parts grafted modified polylactic acid, and 7.5 parts modified zinc oxide. Put the raw materials into a screw extruder and melt-extrude at 210°C. After cooling, granulate to obtain modified polylactic acid chips. Step 2: Dry the modified polylactic acid chips, add 2% by weight of acetylated tributyl citrate to the modified polylactic acid chips, mix to form a mixture, and then add it to a melt spinning device to spin nascent fibers. Step 3: After the nascent fibers are heat-stretched and heat-set, UV-resistant polylactic acid fibers are obtained. The heat-stretching temperature is 80℃, the stretching ratio is 4 times, and the heat-setting temperature is 120℃.
[0028] Example 2
[0029] The only difference from Example 1 is that the mass ratio of polylactic acid to vinylcarbazole is 1:0.16 when preparing grafted modified polylactic acid.
[0030] Preparation of grafted modified polylactic acid: A1. Weigh polylactic acid to a concentration of 50 g / L and dissolve it in tetrahydrofuran. Weigh vinylcarbazole according to a mass ratio of polylactic acid to vinylcarbazole of 1:0.16. Under a nitrogen atmosphere, add vinylcarbazole and initiator benzoyl peroxide to the solution and stir until homogeneous to obtain a reaction solution. The concentration of initiator benzoyl peroxide in the reaction solution is 4 mmol / L.
[0031] A2. Under nitrogen protection, the reaction solution was heated to 80°C and the polymerization reaction was carried out at a constant temperature for 8 hours. After the reaction was completed, the product was added dropwise to deionized water with constant stirring to obtain a solid product.
[0032] A3. The solid product was washed with deionized water and diethyl ether three times each. After washing, it was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain grafted modified polylactic acid.
[0033] The steps and conditions for preparing modified zinc oxide are the same as in Example 1. The grafted modified polylactic acid in the preparation of polylactic acid fiber is replaced with the grafted modified polylactic acid prepared in this example. Other steps and conditions are the same as in Example 1.
[0034] Example 3
[0035] The only difference from Example 1 is that the mass ratio of polylactic acid to vinylcarbazole is 1:0.20 when preparing grafted modified polylactic acid.
[0036] Preparation of grafted modified polylactic acid: A1. Weigh polylactic acid to a concentration of 50 g / L and dissolve it in tetrahydrofuran. Weigh vinylcarbazole according to a mass ratio of polylactic acid to vinylcarbazole of 1:0.20. Under a nitrogen atmosphere, add vinylcarbazole and initiator benzoyl peroxide to the solution and stir until homogeneous to obtain a reaction solution. The concentration of initiator benzoyl peroxide in the reaction solution is 4 mmol / L.
[0037] A2. Under nitrogen protection, the reaction solution was heated to 80°C and the polymerization reaction was carried out at a constant temperature for 8 hours. After the reaction was completed, the product was added dropwise to deionized water with constant stirring to obtain a solid product.
[0038] A3. The solid product was washed with deionized water and diethyl ether three times each. After washing, it was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain grafted modified polylactic acid.
[0039] The steps and conditions for preparing modified zinc oxide are the same as in Example 1. The grafted modified polylactic acid in the preparation of polylactic acid fiber is replaced with the grafted modified polylactic acid prepared in this example. Other steps and conditions are the same as in Example 1.
[0040] Example 4
[0041] The only difference from Example 1 is that, in preparing the modified zinc oxide, the mass ratio of lipoic acid to dopamine is 0.1:1.
[0042] The steps and conditions for preparing grafted modified polylactic acid are the same as in Example 1.
[0043] Preparation of modified zinc oxide: B1. Prepare a Tris-HCl buffer solution with a pH of 8.5. Weigh zinc oxide and add it to the Tris-HCl buffer solution at a concentration of 2.5 g / L. Stir and mix to obtain a zinc oxide dispersion.
[0044] B2. Prepare dopamine with a mass ratio of 4:10 to zinc oxide and prepare lipoic acid with a mass ratio of 0.1:1 to dopamine. Add the prepared dopamine and lipoic acid to the zinc oxide dispersion while stirring, and mix well to obtain the reaction solution.
[0045] B3. The reaction solution was heated to 45℃ and stirred for 8 hours. After centrifugation, the precipitate was collected and washed three times with deionized water. After washing, it was placed in a vacuum drying oven and dried at 70℃ for 12 hours to obtain modified zinc oxide.
[0046] The modified zinc oxide used in the preparation of polylactic acid fibers was replaced with the modified zinc oxide prepared in this embodiment, and the other steps and conditions were the same as in Example 1.
[0047] Example 5
[0048] The only difference from Example 1 is that the mass ratio of lipoic acid to dopamine is 0.6:1 when preparing the modified zinc oxide.
[0049] The steps and conditions for preparing grafted modified polylactic acid are the same as in Example 1.
[0050] Preparation of modified zinc oxide: B1. Prepare a Tris-HCl buffer solution with a pH of 8.5. Weigh zinc oxide and add it to the Tris-HCl buffer solution at a concentration of 2.5 g / L. Stir and mix to obtain a zinc oxide dispersion.
[0051] B2. Prepare dopamine at a mass ratio of 4:10 to zinc oxide, and prepare lipoic acid at a mass ratio of 0.6:1 to dopamine. Add the prepared dopamine and lipoic acid to the zinc oxide dispersion while stirring, and mix well to obtain the reaction solution.
[0052] B3. The reaction solution was heated to 45℃ and stirred for 8 hours. After centrifugation, the precipitate was collected and washed three times with deionized water. After washing, it was placed in a vacuum drying oven and dried at 70℃ for 12 hours to obtain modified zinc oxide.
[0053] The modified zinc oxide used in the preparation of polylactic acid fibers was replaced with the modified zinc oxide prepared in this embodiment, and the other steps and conditions were the same as in Example 1.
[0054] Examples 6-7
[0055] The only difference from Example 1 is that the raw material ratio of the modified polylactic acid chips is different, as shown in Table 1.
[0056] Table 1
[0057] Comparative Example 1
[0058] The only difference from Example 1 is that no grafted modified polylactic acid is added to the modified polylactic acid chips.
[0059] Preparation of modified zinc oxide: B1. Prepare a Tris-HCl buffer solution with a pH of 8.5. Weigh zinc oxide and add it to the Tris-HCl buffer solution at a concentration of 2.5 g / L. Stir and mix to obtain a zinc oxide dispersion.
[0060] B2. Prepare dopamine at a mass ratio of 4:10 to zinc oxide, and prepare lipoic acid at a mass ratio of 0.3:1 to dopamine. Add the prepared dopamine and lipoic acid to the zinc oxide dispersion while stirring, and mix well to obtain the reaction solution.
[0061] B3. The reaction solution was heated to 45℃ and stirred for 8 hours. After centrifugation, the precipitate was collected and washed three times with deionized water. After washing, it was placed in a vacuum drying oven and dried at 70℃ for 12 hours to obtain modified zinc oxide.
[0062] Preparation of polylactic acid fibers: Step 1: Prepare the raw materials for modified polylactic acid chips according to the following mass proportions: 70 parts polylactic acid and 7.5 parts modified zinc oxide. Put the raw materials into a screw extruder and melt-extrude at 210°C. After cooling, granulate to obtain modified polylactic acid chips. Step 2: Dry the modified polylactic acid chips, add 2% by weight of acetylated tributyl citrate to the modified polylactic acid chips, mix to form a mixture, and then add it to a melt spinning device to spin nascent fibers. Step 3: After the nascent fibers are heat-stretched and heat-set, UV-resistant polylactic acid fibers are obtained. The heat-stretching temperature is 80℃, the stretching ratio is 4 times, and the heat-setting temperature is 120℃.
[0063] Comparative Example 2
[0064] The only difference from Example 1 is that the modified zinc oxide in the modified polylactic acid chips is replaced by zinc oxide of equal mass.
[0065] Preparation of grafted modified polylactic acid: A1. Weigh polylactic acid to a concentration of 50 g / L and dissolve it in tetrahydrofuran. Weigh vinylcarbazole according to a mass ratio of polylactic acid to vinylcarbazole of 1:0.18. Under a nitrogen atmosphere, add vinylcarbazole and initiator benzoyl peroxide to the solution and stir until homogeneous to obtain a reaction solution. The concentration of initiator benzoyl peroxide in the reaction solution is 4 mmol / L.
[0066] A2. Under nitrogen protection, the reaction solution was heated to 80°C and the polymerization reaction was carried out at a constant temperature for 8 hours. After the reaction was completed, the product was added dropwise to deionized water with constant stirring to obtain a solid product.
[0067] A3. The solid product was washed with deionized water and diethyl ether three times each. After washing, it was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain grafted modified polylactic acid.
[0068] Preparation of polylactic acid fibers: Step 1: Prepare the raw materials for modified polylactic acid chips according to the following mass proportions: 70 parts polylactic acid, 20 parts grafted modified polylactic acid, and 7.5 parts zinc oxide. Put the raw materials into a screw extruder and melt-extrude at 210°C. After cooling, granulate to obtain modified polylactic acid chips. Step 2: Dry the modified polylactic acid chips, add 2% by weight of acetylated tributyl citrate to the modified polylactic acid chips, mix to form a mixture, and then add it to a melt spinning device to spin nascent fibers. Step 3: After the nascent fibers are heat-stretched and heat-set, UV-resistant polylactic acid fibers are obtained. The heat-stretching temperature is 80℃, the stretching ratio is 4 times, and the heat-setting temperature is 120℃.
[0069] Comparative Example 3
[0070] The only difference from Example 1 is that no modified zinc oxide is added to the modified polylactic acid chips.
[0071] Preparation of grafted modified polylactic acid: A1. Weigh polylactic acid to a concentration of 50 g / L and dissolve it in tetrahydrofuran. Weigh vinylcarbazole according to a mass ratio of polylactic acid to vinylcarbazole of 1:0.18. Under a nitrogen atmosphere, add vinylcarbazole and initiator benzoyl peroxide to the solution and stir until homogeneous to obtain a reaction solution. The concentration of initiator benzoyl peroxide in the reaction solution is 4 mmol / L.
[0072] A2. Under nitrogen protection, the reaction solution was heated to 80°C and the polymerization reaction was carried out at a constant temperature for 8 hours. After the reaction was completed, the product was added dropwise to deionized water with constant stirring to obtain a solid product.
[0073] A3. The solid product was washed with deionized water and diethyl ether three times each. After washing, it was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain grafted modified polylactic acid.
[0074] Preparation of polylactic acid fibers: Step 1: Prepare the raw materials for modified polylactic acid chips according to the mass ratio, including 70 parts of polylactic acid and 20 parts of grafted modified polylactic acid. Put the raw materials into a screw extruder and melt extrude at 210°C. After cooling, granulate to obtain modified polylactic acid chips. Step 2: Dry the modified polylactic acid chips, add 2% by weight of acetylated tributyl citrate to the modified polylactic acid chips, mix to form a mixture, and then add it to a melt spinning device to spin nascent fibers. Step 3: After the nascent fibers are heat-stretched and heat-set, UV-resistant polylactic acid fibers are obtained. The heat-stretching temperature is 80℃, the stretching ratio is 4 times, and the heat-setting temperature is 120℃.
[0075] Comparative Example 4
[0076] The only difference from Example 1 is that polylactic acid fibers are prepared directly from commercially available polylactic acid chips.
[0077] Preparation of polylactic acid fibers: Step 1: Dry the polylactic acid chips, add 2% (by weight) of acetylated tributyl citrate to the polylactic acid chips, mix to form a mixture, and then add it to a melt spinning device to spin nascent fibers. Step 3: After the nascent fibers are heat-stretched and heat-set, polylactic acid fibers are obtained. The heat-stretching temperature is 80℃, the stretching ratio is 4 times, and the heat-setting temperature is 120℃.
[0078] The polylactic acid fibers prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to performance tests, and the results are shown in Table 2.
[0079] The standard for UV protection performance is GB / T 18830-2009, "Evaluation of UV Protection Performance of Textiles".
[0080] Test for retention of tensile strength after UV aging: Referring to standard ISO4892-3, the fiber was placed in UVA-340 (0.76W / m²)... 2 Irradiation at a light source for 500 hours: Breaking strength retention rate = (Breaking strength of fiber before irradiation / Breaking strength of fiber after irradiation) × 100%
[0081] Table 2
[0082] As shown in Table 2, in Examples 1-3, the amount of vinylcarbazole grafted into the grafted polylactic acid (PLA) varied. Vinylcarbazole could increase the UV absorption rate and reduce the UV transmittance of PLA fibers. In Example 3, when the amount of vinylcarbazole was higher, homopolymerization occurred between the grafts, preventing covalent grafting to the PLA molecular chain, resulting in a lower final grafting rate. Therefore, the effect of grafted PLA on enhancing the UV resistance of the fibers was not as good as in Example 1. The lipoic acid on the modified zinc oxide was beneficial in inhibiting the UV aging of PLA. Among Examples 1, 4, and 5, Example 1 showed the highest breakage retention rate and the best UV aging resistance of the fibers. Compared to the examples, the comparative examples, where no grafted PLA or modified zinc oxide was added to the fiber raw material, exhibited poorer UV resistance.
[0083] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0084] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A UV-resistant polylactic acid fiber, characterized in that, The polylactic acid fiber is prepared by melt spinning a mixture of modified polylactic acid chips and a plasticizer; The modified polylactic acid chips, by weight, comprise the following raw materials: 60-80 parts of polylactic acid, 15-25 parts of grafted polylactic acid, and 5-10 parts of modified zinc oxide; The grafted modified polylactic acid is a product obtained by introducing carbazole groups into the polylactic acid molecular chain through free radical graft polymerization of polylactic acid and vinyl carbazole. The modified zinc oxide is zinc oxide loaded with polydopamine and grafted with lipoic acid.
2. The UV-resistant polylactic acid fiber according to claim 1, characterized in that, The preparation method of the grafted modified polylactic acid includes the following steps: A1. Dissolve polylactic acid in tetrahydrofuran, add vinylcarbazole and initiator benzoyl peroxide under nitrogen atmosphere, and stir until homogeneous to obtain a reaction solution; A2. The polymerization reaction was carried out under nitrogen protection. After the reaction was completed, the product was added dropwise to deionized water under constant stirring to obtain a solid product. A3. After washing with deionized water and diethyl ether in sequence, the grafted polylactic acid is dried under vacuum to constant weight to obtain the grafted modified polylactic acid.
3. The UV-resistant polylactic acid fiber according to claim 2, characterized in that, The mass ratio of polylactic acid to vinylcarbazole is 1:0.16-0.20; The concentration of the initiator benzoyl peroxide in the reaction solution is 3-5 mmol / L.
4. The UV-resistant polylactic acid fiber according to claim 2, characterized in that, The heating polymerization reaction is carried out at a temperature of 60-80℃ for a duration of 6-10 hours.
5. The UV-resistant polylactic acid fiber according to claim 1, characterized in that, The preparation method of the modified zinc oxide includes the following steps: B1. Disperse zinc oxide in a Tris-HCl buffer solution with a pH of 8-9 to obtain a zinc oxide dispersion; B2. While stirring, add dopamine and lipoic acid to the zinc oxide dispersion, and mix well to obtain the reaction solution; B3. The reaction solution is stirred at 40-50℃ for 4-8 hours, centrifuged, washed with water, and then vacuum dried to obtain modified zinc oxide.
6. The UV-resistant polylactic acid fiber according to claim 5, characterized in that, The concentration of zinc oxide in the zinc oxide dispersion is 2-3 g / L.
7. The UV-resistant polylactic acid fiber according to claim 5, characterized in that, The mass ratio of dopamine to zinc oxide is 1-7:10; The molar ratio of lipoic acid to dopamine is 0.1-0.6:
1.
8. The UV-resistant polylactic acid fiber according to claim 1, characterized in that, The plasticizer is one of epoxidized soybean oil, tributyl citrate, and acetylated tributyl citrate, and the plasticizer is 1-3% of the mass of modified polylactic acid chips.
9. A method for preparing UV-resistant polylactic acid fiber, characterized in that, The preparation of UV-resistant polylactic acid fibers as described in any one of claims 1-8 comprises the following steps: Step 1: Prepare the raw materials for modified polylactic acid chips according to the proportion, put the raw materials into a screw extruder for melt extrusion, cooling, and granulation to obtain modified polylactic acid chips; Step 2: After drying the modified polylactic acid chips, add plasticizer and mix to form a mixture, then add it to a melt spinning device to spin and obtain nascent fibers; Step 3: After the nascent fibers are thermally stretched and thermally set, UV-resistant polylactic acid fibers are obtained.
10. An application of UV-resistant polylactic acid fiber, characterized in that, The UV-resistant polylactic acid fiber as described in any one of claims 1-8 is used to prepare outdoor textile products.