A method for preparing a cotton-like bio-based fiber

Abstract

The application relates to a preparation method of a cotton-imitating bio-based fiber, and belongs to the technical field of bio-based fibers.The fiber is prepared from 60-85 parts of a polylactic acid matrix material, 5-15 parts of ultraviolet absorption-extinction composite particles, 3-10 parts of a compatilizer and 2-8 parts of a pore-forming fiber-forming agent; the composite particles are treated by a bio-based surface modifier and are prepared from anatase titanium dioxide as a core and nano kaolin as a shell; the fiber cross section is clover-shaped or cross-shaped special-shaped cross section.In preparation, the components are first melt-blended, granulated, spun through a special-shaped spinneret, drawn and shaped, then subjected to pore-forming treatment in an alkaline aqueous solution, and then impregnated and finished by a bio-based ultraviolet absorption enhancer.The application realizes super-extinction and high-efficiency sun protection synergy through the core-shell composite particles, builds a high-wetting network through the special-shaped cross section and the pore-forming micropore, and also has the characteristics of soft cotton-imitating hand feeling.

Description

Technical Field

[0001] This invention belongs to the field of bio-based fiber technology and relates to a method for preparing cotton-like bio-based fibers. Background Technology

[0002] With increasing environmental awareness and the dwindling supply of petroleum resources, bio-based fiber materials, represented by polylactic acid (PLA), have received widespread attention. PLA fibers, derived from plant starches such as corn and cassava, possess advantages such as biodegradability and good biocompatibility, making them an ideal alternative to petroleum-based polyester fibers. However, PLA fibers still have significant shortcomings in functional applications. First, the lack of UV-absorbing groups in the PLA molecular chain results in poor UV protection performance, limiting its application in outdoor clothing. Second, PLA fibers have a stiff feel and lack the soft touch of natural cotton fibers. Third, achieving efficient moisture wicking and perspiration wicking in PLA fibers remains a technical challenge.

[0003] To improve the performance of PLA fibers, existing technologies mainly employ the following solutions: First, by blending and adding inorganic matting agents to achieve a matting effect and partially improve UV resistance. However, conventional TiO2 has poor dispersion in the PLA matrix, and its photocatalytic activity can lead to fiber degradation. Second, by using profiled cross-section spinning technology to improve moisture wicking performance. However, the grooves of a single profiled cross-section in the ultra-matting system are easily blocked by the matting agent, affecting the moisture wicking effect. Third, by using finishing methods to impart UV resistance to PLA fibers. However, this method suffers from drawbacks such as insufficient affinity between finishing agents and PLA, and limited processing temperature. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing cotton-like bio-based fibers.

[0005] The objective of this invention can be achieved through the following technical solutions: A cotton-like bio-based fiber, said cotton-like bio-based fiber is prepared from the following raw materials in parts by weight: 60-85 parts of polylactic acid matrix, 5-15 parts of UV absorption-extinction composite particles 3-10 parts compatibilizer 2-8 parts of pore-opening fiber-forming agent, The ultraviolet absorption-extinction composite particles have anatase titanium dioxide as the core and nano-kaolin as the shell, and are treated with a bio-based surface modifier.

[0006] Furthermore, the bio-based surface modifier is a polylactic acid-g-dopamine copolymer.

[0007] Furthermore, the anatase titanium dioxide has a particle size of 0.1~0.4μm; the nano-kaolin has a particle size of <0.2μm and a thickness of 10~30nm.

[0008] Furthermore, the preparation method of the ultraviolet absorption-extinction composite particles includes the following steps: S4-1: Disperse anatase titanium dioxide and polyvinyl alcohol in water for 30-60 min to obtain slurry A; S4-2: Add nano-kaolin to slurry A and perform high-speed shear dispersion treatment for 30~60 min to obtain slurry B; S4-3: Polylactic acid-g-dopamine copolymer is added to slurry B, and surface modification is carried out under pH conditions of 7.0~8.5 to obtain the ultraviolet absorption-extinction composite particles.

[0009] Furthermore, the pore-forming agent is one of polybutylene terephthalate or polybutylene succinate.

[0010] Furthermore, the compatibilizer is a polyethylene glycol-polylactic acid block copolymer.

[0011] Furthermore, the cross-section of the fiber is a clover-shaped or cross-shaped irregular cross-section, and the ratio of the groove depth to the width of the irregular cross-section is 2:1 to 4:1.

[0012] A method for preparing a cotton-like bio-based fiber includes the following steps: S8-1: Polylactic acid matrix, ultraviolet absorption-dulling composite particles, compatibilizer and open-cell fiber forming agent are mixed and melt-blended and granulated by twin-screw extruder to obtain spinning masterbatch; S8-2: The spinning masterbatch is melt-spun and spun using a shaped spinneret. The spinning temperature is 185~215℃ and the spinning speed is 2500~4000m / min. S8-3: The nascent fibers obtained in step S8-2 are subjected to stretching and heat setting treatment, with a stretching ratio of 2.5 to 4.0 times and a heat setting temperature of 80 to 110°C; S8-4: The fibers obtained in step S8-3 are subjected to pore-opening treatment in an alkaline aqueous solution at 50~70℃ for 10~30 min. S8-5: The fibers obtained in step S8-4 are impregnated and treated in a finishing solution containing a bio-based ultraviolet absorption enhancer, wherein the bio-based ultraviolet absorption enhancer is baicalin, the finishing temperature is 80~100℃, and the finishing time is 30~90min.

[0013] Furthermore, the alkaline aqueous solution mentioned in step S8-4 is a sodium carbonate aqueous solution with a pH value of 9.0~10.5.

[0014] Furthermore, the total concentration of the bio-based UV absorption enhancer in the finishing solution described in step S8-5 is 5~15 g / L.

[0015] This invention employs composite particles with anatase TiO2 as the core and nano-kaolin as the shell. TiO2 itself exhibits refraction and scattering effects on visible light, while the nano-kaolin flakes, with their high aspect ratio and sheet-like structure, produce an additional diffuse reflection effect on visible light. The combination of these two mechanisms allows this invention to achieve an ultra-extinction effect with only a small amount of TiO2 added. The nano-kaolin flakes are sheared onto the TiO2 surface at high speed, forming a physical isolation layer that effectively prevents the aggregation of TiO2 nanoparticles. A polylactic acid-g-dopamine modifier further imparts good interfacial compatibility between the composite particle surface and the PLA matrix, resulting in uniform nanoscale dispersion of the composite particles within the PLA. Simultaneously, anatase TiO2 exhibits photocatalytic activity under ultraviolet light irradiation, generating free radicals that lead to the breakage and degradation of PLA molecular chains. In this invention, the nano-kaolin shell acts as a physical barrier, preventing direct contact between TiO2 and the PLA matrix. Furthermore, the layered structure of kaolin can capture some photogenerated free radicals, significantly inhibiting the photocatalytic activity of TiO2. In addition, TiO2 is a recognized highly efficient UV shielding agent with good absorption and scattering capabilities for both UVA and UVB; nano-kaolin, as a silicate mineral, also has a certain reflective effect on ultraviolet rays due to its layered structure; the composite particles after the two are combined have a significantly enhanced UV shielding effect.

[0016] Following the pore-opening process, this invention further impregnates and finishes the fibers with baicalin. Baicalin is a flavonoid compound extracted from Scutellaria baicalensis, containing multiple phenolic hydroxyl groups and a conjugated system in its molecular structure, exhibiting strong ultraviolet absorption in the 280-380 nm wavelength range. The composite particles and the bio-based finishing agent have a synergistic anti-ultraviolet effect, with the composite particles providing ultraviolet shielding and the bio-based finishing agent providing ultraviolet absorption.

[0017] The interconnected micropores formed by the alkali-dissolving treatment of the open-pore fiber-forming agent increase the specific surface area of ​​the fiber, providing more adsorption sites for subsequent bio-based ultraviolet absorption finishing agents, thereby improving the fixation amount and wash resistance of the finishing agent.

[0018] Clover-shaped or cross-shaped irregular cross sections form longitudinally penetrating grooves on the fiber surface. These grooves, through capillary effect, rapidly wick sweat from the skin to the fiber surface and diffuse along the fiber axis. This invention controls the groove depth to width ratio to be between 2:1 and 4:1, ensuring sufficient capillary cross-sectional area and wicking driving force while avoiding excessively deep grooves that could degrade the fiber's mechanical properties.

[0019] This invention utilizes PBAT or PBS as a pore-opening fiber-forming agent, which selectively dissolves in a weakly alkaline aqueous solution after spinning, forming interconnected micropores with a diameter of approximately 0.1~1μm on the fiber surface and inside. These micropores have the following functions: they are interconnected with surface grooves, forming multi-level capillary channels to accelerate moisture transport; they increase the fiber's moisture absorption and evaporation rates; and the microporous structure makes the fiber softer and fluffier, improving its hand feel.

[0020] The beneficial effects of this invention are: This invention constructs anatase titanium dioxide-nanokaolin core-shell composite particles, achieving uniform ultra-dulling at low addition levels and effectively inhibiting PLA degradation caused by TiO2 photocatalysis. Simultaneously, the composite particles' own UV shielding and the subsequent molecular-level UV absorption of the baicalin bio-based finishing agent create a dual synergy. Furthermore, it integrates surface capillary moisture wicking of irregular cross-sections, interconnected microporous capillary channels formed by alkaline dissolution of open-pore fiber-forming agents, and the hydrophilic segment chemical adsorption mechanism introduced by compatibilizers into a single fiber, achieving rapid moisture wicking. Moreover, the entire process utilizes biomass and natural minerals as raw materials, employs an aqueous system with no VOC emissions, and the irregular cross-sections and microporous structure impart a soft, fluffy, cotton-like feel to the fiber, overcoming the technical challenges of poor delustering agent dispersibility, insufficient UV protection, and difficulty in simultaneously achieving moisture wicking performance in existing technologies. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0022] It should be noted that, unless otherwise specified, the present invention does not specifically limit the source of the raw materials used in the following embodiments. Commercially available products or products prepared by conventional preparation methods that are well known to those skilled in the art can be used. Experimental methods that do not specify specific conditions are all conventional methods and conventional conditions well known in the art.

[0023] Example 1

[0024] This embodiment provides a cotton-like bio-based fiber, which is prepared from the following raw materials in parts by weight: 70 parts of polylactic acid matrix, 10 parts of ultraviolet absorption-dulling composite particles, 6 parts of compatibilizer (polyethylene glycol-polylactic acid block copolymer), and 5 parts of cell-opening fiber forming agent (polybutylene terephthalate-adipate). The UV absorption-extinction composite particles used in this embodiment have anatase titanium dioxide as the core and nano-kaolin as the shell, and are treated with a bio-based surface modifier (polylactic acid-g-dopamine copolymer). The anatase titanium dioxide has a particle size of 0.2 μm, the nano-kaolin has a particle size of <0.2 μm, and a thickness of 20 nm.

[0025] The method for preparing the ultraviolet absorption-extinction composite particles is as follows: S4-1: Anatase titanium dioxide and polyvinyl alcohol, with the amount of polyvinyl alcohol added being 3% of the mass of anatase titanium dioxide, are dispersed in water for 45 minutes to obtain slurry A; S4-2: Add nano-kaolin to slurry A, with anatase titanium dioxide to nano-kaolin in a mass ratio of 2:1, and perform high-speed shear dispersion treatment for 45 min to obtain slurry B; S4-3: Polylactic acid-g-dopamine copolymer is added to slurry B. The amount of polylactic acid-g-dopamine copolymer added is 5% of the mass of anatase titanium dioxide. Surface grafting modification is carried out under pH 8.0 conditions to obtain the ultraviolet absorption-extinction composite particles.

[0026] The fiber has a clover-shaped cross section, and the ratio of the groove depth to the width of the cross section is 3:1.

[0027] The fiber preparation method in this embodiment is as follows: S8-1: Polylactic acid matrix, UV-absorbing-dulling composite particles, compatibilizer and open-cell fiber-forming agent are mixed and melt-blended and granulated by twin-screw extruder at a melting temperature of 190℃ and a screw speed of 300rpm to obtain spinning masterbatch; S8-2: The spinning masterbatch is melt-spun using a clover-shaped spinneret at a spinning temperature of 200℃ and a spinning speed of 3000m / min. S8-3: The nascent fibers obtained in step S8-2 are subjected to stretching and heat setting treatment, with a stretching ratio of 3.2 times and a heat setting temperature of 95℃; S8-4: The fibers obtained in step S8-3 are subjected to pore-opening treatment in a sodium carbonate aqueous solution with a pH of 10.0 at 60°C for 20 minutes. S8-5: The fibers obtained in step S8-4 are impregnated and treated in a finishing solution containing a bio-based ultraviolet absorption enhancer, wherein the bio-based ultraviolet absorption enhancer is baicalin, the concentration of baicalin in the finishing solution is 10 g / L, the finishing temperature is 90℃, and the finishing time is 60 min.

[0028] Example 2

[0029] This embodiment provides a cotton-like bio-based fiber, which is prepared from the following raw materials in parts by weight: 60 parts of polylactic acid matrix, 5 parts of ultraviolet absorption-dulling composite particles, 3 parts of compatibilizer (polyethylene glycol-polylactic acid block copolymer), and 2 parts of cell-opening fiber-forming agent (polybutylene succinate).

[0030] The anatase titanium dioxide particles used in the UV absorption-extinction composite particles have a particle size of 0.1 μm, and the nano-kaolin particles have a particle size of <0.2 μm and a thickness of 10 nm. In the preparation method of the composite particles, the mass ratio of anatase titanium dioxide to nano-kaolin is 1.5:1, and surface grafting modification is carried out under pH 7.0 conditions. The fiber cross-section is a cross-shaped irregular cross-section, and the ratio of groove depth to width is 2:1.

[0031] In the preparation method, the spinning temperature is 185℃, the spinning speed is 2500m / min, the draw ratio is 2.5 times, the heat setting temperature is 80℃, the pore opening treatment is carried out in a sodium carbonate aqueous solution at 50℃ and pH 9.0 for 10min, the concentration of baicalin in the finishing solution is 5g / L, the finishing temperature is 80℃, and the finishing time is 30min.

[0032] The remaining steps and parameters are the same as in Example 1.

[0033] Example 3

[0034] This embodiment provides a cotton-like bio-based fiber, which is prepared from the following raw materials in parts by weight: 85 parts of polylactic acid matrix, 15 parts of ultraviolet absorption-dulling composite particles, 10 parts of compatibilizer (polyethylene glycol-polylactic acid block copolymer), and 8 parts of cell-opening fiber forming agent (polybutylene terephthalate-adipate).

[0035] The anatase titanium dioxide particles used in the UV absorption-extinction composite particles had a particle size of 0.4 μm, and the nano-kaolin particles had a particle size of <0.2 μm and a thickness of 30 nm. In the preparation method of the composite particles, the mass ratio of anatase titanium dioxide to nano-kaolin was 2.5:1, and surface grafting modification was carried out under pH 8.5 conditions. The fiber cross-section was a cloverleaf-shaped irregular cross-section, with a groove depth to width ratio of 4:1.

[0036] In the preparation method, the spinning temperature was 215℃, the spinning speed was 4000m / min, the draw ratio was 4.0, the heat setting temperature was 110℃, the pore-opening treatment was carried out in a sodium carbonate aqueous solution at 70℃ and pH 10.5 for 30 min, the baicalin concentration in the finishing solution was 15g / L, the finishing temperature was 100℃, and the finishing time was 90 min. The remaining steps and parameters were the same as in Example 1.

[0037] Example 4

[0038] This embodiment uses the same raw material ratio, composite particles, and preparation method as Example 1. The only difference is that the pore-forming agent is a mixture of polybutylene terephthalate (PBAT) and polybutylene succinate (PBS) in a 1:1 mass ratio, with a total addition amount of 5 parts by weight. All other conditions are the same as in Example 1.

[0039] Example 5

[0040] This embodiment uses the same raw material ratio, composite particles, and preparation method as Example 1. The only difference is that the compatibilizer is a mixture of polyethylene glycol-polylactic acid block copolymer (PEG-PLLA) and polyethylene glycol (PEG) in a mass ratio of 2:1, with a total addition amount of 6 parts by weight. All other conditions are the same as in Example 1.

[0041] Example 6

[0042] This embodiment uses the same raw material ratio, composite particles, and preparation method as Example 1. The only difference is that in step S8-2, a cross-shaped spinneret is used for spinning, the fiber cross-section is a cross-shaped cross-section, and the ratio of groove depth to width is 3:1. All other conditions are the same as in Example 1.

[0043] Example 7

[0044] This embodiment uses the same raw material ratio, composite particles, and preparation method as Example 1. The only difference is that in step S8-2, a clover-shaped spinneret is used, and the ratio of groove depth to width is 2.5:1. All other conditions are the same as in Example 1.

[0045] Example 8

[0046] This embodiment uses the same raw material ratio, composite particle and fiber cross-section design as Example 1. The only difference is in the preparation process parameters: the spinning temperature in step S8-2 is 195℃ and the spinning speed is 2800m / min. All other conditions are the same as in Example 1.

[0047] Example 9

[0048] This embodiment uses the same raw material ratio, composite particle and fiber cross-section design as Example 1. The only difference is in the preparation process parameters: the draw ratio in step S8-3 is 3.5 times and the heat setting temperature is 100℃. All other conditions are the same as in Example 1.

[0049] Example 10

[0050] This embodiment uses the same raw material ratio, composite particle and fiber cross-section design as Example 1. The only difference is in the preparation process parameters: the pore opening treatment in step S8-4 is carried out in a sodium carbonate aqueous solution at 55°C and pH 9.5 for 15 minutes. All other conditions are the same as in Example 1.

[0051] Comparative Example 1 This comparative example uses the same raw material ratio and preparation method as Example 1, except that: no ultraviolet absorption-extinction composite particles are added, and the 10 parts that are reduced are made up by polylactic acid matrix. All other conditions are the same as in Example 1.

[0052] Comparative Example 2 This comparative example uses the same raw material ratio and preparation method as Example 1, with the only difference being that the ultraviolet absorption-extinction composite particles are a simple physical mixture of anatase titanium dioxide without core-shell structure design and nano-kaolin (the mass ratio of anatase titanium dioxide to nano-kaolin is 2:1, without surface modification treatment), and the addition amount is still 10 parts. All other conditions are the same as in Example 1.

[0053] Comparative Example 3 This comparative example uses the same raw material ratios and preparation methods as Example 1, except that no compatibilizer is added, and the reduced 6 parts are made up by the polylactic acid matrix. All other conditions remain the same as in Example 1.

[0054] Comparative Example 4 This comparative example uses the same raw material ratio and preparation method as Example 1, with the only differences being: no cell-opening fiber-forming agent is added, the reduced 5 parts are made up by the polylactic acid matrix, and the cell-opening treatment in step S8-4 is omitted. All other conditions remain the same as in Example 1.

[0055] Comparative Example 5 This comparative example uses the same raw material ratio and preparation method as Example 1, except that a circular spinneret is used for spinning in step S8-2, and the fiber cross-section is circular. All other conditions are the same as in Example 1.

[0056] Comparative Example 6 This comparative example uses the same raw material ratio, composite particles, and preparation method as Example 1, except that the impregnation and finishing process in step S8-5 is omitted. All other conditions remain the same as in Example 1.

[0057] Performance testing methods Moisture regain test: The moisture regain of the fiber was tested using the oven drying method according to GB / T 6505-2017 standard. Test conditions: Oven temperature 105±2℃, drying time 4h, sample mass 5g.

[0058] UV resistance test: The UV protection factor (UPF) and UVA transmittance of the fiber were tested using a UV-Vis spectrophotometer in accordance with GB / T 18830-2009 standard. The test wavelength range was 290~400nm.

[0059] Softness test: The bending stiffness of the fibers was tested using a fabric softness tester in accordance with ASTM D1388-14 standard. The fibers were woven into standard fabric samples (warp and weft density of 40 threads / cm), with sample size of 25.4mm × 152.4mm. The test platform was tilted at an angle of 41.5°. The length of the sample slipped out was recorded and the bending stiffness was calculated.

[0060] The specific experimental results are summarized in the table below.

[0061]

[0062] Based on the test data above, we can draw the following conclusions: (1) As can be seen from the comparison between Comparative Example 1 and Example 1, the UPF value of the fiber without the addition of UV absorption-extinction composite particles is only 10.5, and the moisture regain is also significantly reduced. This indicates that the present invention not only endows the fiber with excellent UV shielding function through core-shell structure composite particles, but also improves the moisture absorption of polylactic acid fiber through the hydrophilic shell of nano-kaolin.

[0063] (2) As can be seen from the comparison between Comparative Example 2 and Example 1, although the physical mixed particles without core-shell structure design and surface modification have a certain UV shielding effect, it is far lower than that of Example 1, and the UVA transmittance is as high as 12.3%. This shows that the anatase titanium dioxide-nanokaolin core-shell structure and its bio-based surface modification treatment used in this invention have a synergistic effect on particle dispersibility and UV absorption efficiency.

[0064] (3) As can be seen from the comparison between Comparative Example 3 and Example 1, the addition of compatibilizer also improves the moisture absorption and softness of the fiber. The moisture regain increased from 2.10% to 2.85%, and the bending stiffness decreased from 1.45mN·cm to 0.85mN·cm. This may be because the polyethylene glycol-polylactic acid block copolymer effectively improves the interfacial compatibility between the polylactic acid matrix and the composite particles, and reduces stress concentration points.

[0065] (4) As can be seen from the comparison between Comparative Example 4 and Example 1, after omitting the opening-pore fiber-forming agent and the opening-pore treatment step, the fiber moisture regain decreased from 2.85% to 1.95%. This indicates that the opening-pore fiber-forming agent undergoes selective hydrolysis in alkaline aqueous solution, forming a microporous structure on the fiber surface and inside. These micropores not only provide channels and sites for the adsorption of water molecules, but also play an important role in improving the hygroscopicity and softness of the fiber.

[0066] (5) As can be seen from the comparison between Comparative Example 5 and Example 1, the bending stiffness of the circular cross-section fiber is as high as 1.82 mN·cm, and the moisture regain is only 2.05%, while the bending stiffness of the clover-shaped cross-section fiber is only 0.85 mN·cm, and the moisture regain is increased to 2.85%. This shows that the irregular cross-section design significantly improves the moisture absorption and wicking properties and soft hand feel of the fiber by increasing the specific surface area and surface groove structure, and is the key structural design to achieve cotton-like characteristics.

[0067] (6) As can be seen from the comparison between Comparative Example 6 and Example 1, the initial UPF value of the fiber decreased and the UVA transmittance increased after omitting the baicalin impregnation finishing process. This indicates that baicalin and the UV absorption-extinction composite particles produced a synergistic UV absorption effect: the composite particles are embedded in the fiber matrix during the fiber forming process to form a basic UV shielding layer, while baicalin is adsorbed on the fiber surface and the inner wall of the micropores through post-finishing, and the two together construct a global UV protection network.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the scope of the present invention.

Claims

1. A cotton-like bio-based fiber, characterized in that, The cotton-like bio-based fiber is prepared from the following raw materials in parts by weight: 60-85 parts of polylactic acid matrix, 5-15 parts of UV absorption-extinction composite particles 3-10 parts compatibilizer 2-8 parts of pore-opening fiber-forming agent, The ultraviolet absorption-extinction composite particles have anatase titanium dioxide as the core and nano-kaolin as the shell, and are treated with a bio-based surface modifier.

2. The cotton-like bio-based fiber according to claim 1, characterized in that, The bio-based surface modifier is a polylactic acid-g-dopamine copolymer.

3. The cotton-like bio-based fiber according to claim 1, characterized in that, The anatase titanium dioxide has a particle size of 0.1~0.4μm; the nano-kaolin has a particle size of <0.2μm and a thickness of 10~30nm.

4. The cotton-like bio-based fiber according to claim 1, characterized in that, The preparation method of the ultraviolet absorption-extinction composite particles includes the following steps: S4-1: Disperse anatase titanium dioxide and polyvinyl alcohol in water for 30-60 min to obtain slurry A; S4-2: Add nano-kaolin to slurry A and perform high-speed shear dispersion treatment for 30~60 min to obtain slurry B; S4-3: Polylactic acid-g-dopamine copolymer is added to slurry B, and surface modification is carried out under pH conditions of 7.0~8.5 to obtain the ultraviolet absorption-extinction composite particles.

5. The cotton-like bio-based fiber according to claim 1, characterized in that, The open-cell fiber-forming agent is one of polybutylene terephthalate-adipate or polybutylene succinate.

6. The cotton-like bio-based fiber according to claim 1, characterized in that, The compatibilizer is a polyethylene glycol-polylactic acid block copolymer.

7. The cotton-like bio-based fiber according to claim 1, characterized in that, The fiber has a clover-shaped or cross-shaped cross section, and the ratio of the groove depth to the width of the cross section is 2:1 to 4:

1.

8. A method for preparing cotton-like bio-based fibers as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S8-1: Polylactic acid matrix, ultraviolet absorption-dulling composite particles, compatibilizer and open-cell fiber forming agent are mixed and melt-blended and granulated by twin-screw extruder to obtain spinning masterbatch; S8-2: The spinning masterbatch is melt-spun and spun using a shaped spinneret. The spinning temperature is 185~215℃ and the spinning speed is 2500~4000m / min. S8-3: The nascent fibers obtained in step S8-2 are subjected to stretching and heat setting treatment, with a stretching ratio of 2.5 to 4.0 times and a heat setting temperature of 80 to 110°C; S8-4: The fibers obtained in step S8-3 are subjected to pore-opening treatment in an alkaline aqueous solution at 50~70℃ for 10~30 min. S8-5: The fibers obtained in step S8-4 are impregnated and treated in a finishing solution containing a bio-based ultraviolet absorption enhancer, wherein the bio-based ultraviolet absorption enhancer is baicalin, the finishing temperature is 80~100℃, and the finishing time is 30~90min.

9. The method for preparing a cotton-like bio-based fiber according to claim 8, characterized in that, The alkaline aqueous solution mentioned in step S8-4 is a sodium carbonate aqueous solution with a pH value of 9.0~10.

5.

10. The method for preparing a cotton-like bio-based fiber according to claim 8, characterized in that, The total concentration of the bio-based UV absorption enhancer in the finishing solution described in step S8-5 is 5~15 g / L.

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