A method for producing a polylactic acid fiber

Abstract

The application discloses a preparation method of polylactic acid fiber, and belongs to the technical field of textile materials. The polylactic acid fiber has the problems of hard and stiff hand feeling and poor dyeing performance. The polylactic acid resin is used as a base body, mesoporous silicon oxide, a compatilizer and an enzymatic pore-forming agent are mixed, an oxidizing agent is added during double-screw extrusion, and enzymatic treatment is carried out after melt blowing to realize modification. The mesoporous silicon oxide provides adsorption sites for biological enzymes, the oxidizing agent breaks the polylactic acid molecular chain to form notches, and the enzymatic pore-forming agent forms pores after degradation. The components jointly construct the porous network of the prepared polylactic acid fiber, the biodegradability and mechanical properties of the polylactic acid fiber are retained, the soft hand feeling of the polylactic acid fiber is effectively improved, and sufficient channels are provided for dye molecule penetration.

Description

Technical Field

[0001] This application belongs to the field of textile materials technology, specifically relating to a method for preparing polylactic acid fiber. Background Technology

[0002] Polylactic acid (PLA) fiber uses renewable plant resources such as corn as raw materials and is biodegradable, aligning with the low-carbon and environmentally friendly development trend of the textile industry. It has broad application prospects in clothing, home furnishings, and medical protective equipment. However, PLA molecules are semi-crystalline, with a dense molecular arrangement and a high proportion of crystalline regions, resulting in two major defects: firstly, the fiber has a stiff feel, leading to poor fabric comfort; secondly, the dense molecular structure hinders dye penetration, resulting in light color yield, low dye uptake, and color fastness that fails to meet the requirements of mid-to-high-end textiles.

[0003] In existing polylactic acid (PLA) fiber processing technologies, physical treatments (such as mechanical stretching and low-temperature heat treatment) can only slightly alter the fiber surface morphology and cannot expand the porosity at the molecular level, resulting in limited performance improvement. Chemical finishing (such as coating and grafting modification) requires the use of large amounts of chemicals, posing environmental pollution risks, and the modification effect has poor durability and is easily lost with washing. Single meltblown process modification relies solely on screw shearing to adjust the molecular structure, making it difficult to achieve precise porosity construction. Furthermore, although meltblown material technology for masks can improve the material structure through melt flow index control, it has not yet achieved simultaneous optimization of the molecular structure and dyeing properties of PLA fibers. The industry lacks efficient modification solutions that balance environmental friendliness, mechanical properties, and dyeing performance, hindering the industrial application of PLA fibers.

[0004] Therefore, it is of great significance to explore a preparation method that controls molecular chain scission and void construction to amplify intermolecular voids and improve the softness and feel of fibers while ensuring their mechanical strength. Summary of the Invention

[0005] This application aims to overcome the shortcomings of existing polylactic acid fiber modification technologies and provide a method for preparing polylactic acid fibers. By controlling the molecular chain breaking and void construction process, the method significantly amplifies the intermolecular voids while ensuring the mechanical strength of the fiber, improves the soft hand feel of the fiber, enhances the color depth and color fastness of dyeing, and retains the biodegradability of polylactic acid fibers.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] This application provides a method for preparing polylactic acid fibers, comprising the following steps:

[0008] S1. Disperse mesoporous silica in deionized water, stir, and then vacuum dry to obtain mesoporous silica powder;

[0009] S2. Add the enzymatic porogen, the above-mentioned mesoporous silica powder and compatibilizer to the polylactic acid resin matrix, and stir to obtain a mixed raw material;

[0010] S3. Add the above mixed raw materials to a twin-screw extruder, set a gradient temperature for melt blending, add an oxidant at a set position in the metering section of the twin-screw extruder through a side feeding device, and then transport the melt after twin-screw extrusion to a melt-blowing die for melt-blowing to obtain polylactic acid fiber;

[0011] S4. Prepare a biological enzyme solution using a buffer solution, place the meltblown polylactic acid fiber in the biological enzyme solution for enzymatic hydrolysis, wash with warm water after enzymatic hydrolysis, and then dry to obtain a polylactic acid fiber.

[0012] Furthermore, in S1, the pore size of the mesoporous silica is 2-50 nm, and the specific surface area is 500-600 m² / g; the stirring temperature is 25-35℃, the stirring time is 2-4 h, and the stirring speed is 200-300 rpm; the vacuum drying temperature is 60-80℃, the vacuum time is 2-4 h, and the vacuum degree is 0.06-0.09 MPa.

[0013] Furthermore, in S2, the melt index of polylactic acid resin is 80-100 g / 10 min;

[0014] Enzymatic hydrolytic porogens include any one of hydroxypropyl chitosan, hydroxypropyl starch, and carboxymethyl cellulose;

[0015] The compatibilizer includes either polyethylene glycol or sorbitan monolaurate;

[0016] The stirring temperature is 80-100℃, and the stirring time is 1-2 hours.

[0017] Furthermore, in S3, the oxidant is ammonium persulfate or potassium persulfate;

[0018] Furthermore, in S3, the gradient temperature is: 120-140℃ for the hopper section, 150-160℃ for the compression section, and 160-170℃ for the metering section; the screw speed of the twin-screw extruder is 500-600 rpm; the set position is 1 / 3 of the metering section.

[0019] Furthermore, in S3, the meltblown process conditions are: die head temperature 165-175℃, hot air temperature 170-180℃, hot air velocity 0.3-0.6m / s, receiving distance 8-15cm, and melt pump pressure 5-10MPa.

[0020] Furthermore, in S4, the enzyme in the enzyme solution is any one of chitosanase, α-amylase, and cellulase;

[0021] The buffer solution is an acetate-sodium acetate buffer solution or a citric acid-sodium citrate buffer solution, and the pH of the system is adjusted to 5.0-6.5.

[0022] The enzymatic hydrolysis temperature is 40-55℃, the time is 3-6h, and the process is continuously stirred at a stirring rate of 50-100rpm.

[0023] The temperature of the warm water for washing is 40-50℃, and the number of washes is 3-5 times, with each wash lasting 15-20 minutes.

[0024] The drying process is vacuum drying, with a drying temperature of 60-80℃, a drying time of 2-4 hours, and a vacuum degree of 0.06-0.09MPa.

[0025] Furthermore, in S4, the preparation method of the bio-enzyme solution is as follows: the buffer solution is preheated in a constant temperature water bath at 25-35℃, and the bio-enzyme is added to the buffer solution at a solid-liquid ratio of (0.5-1.5) mg: 1 mL. Then, the solution is stirred at a speed of 50-100 rpm for 15-30 min to obtain the bio-enzyme solution; the solid-liquid ratio of polylactic acid fiber to bio-enzyme solution is 1 g: (20-50) mL.

[0026] Furthermore, in the entire preparation process, the mass ratio of mesoporous silica, polylactic acid resin, compatibilizer, enzymatic hydrolytic porogen and oxidant is (20-30): (40-64): (5-8): (10-20): (1-2).

[0027] This application discloses a method for preparing polylactic acid (PLA) fibers. Using PLA resin as a matrix, mesoporous silica, a compatibilizer, an enzymatically hydrolyzed porogen, and an oxidant are mixed as a meltblown raw material. Before meltblowing, the mesoporous silica is uniformly mixed with the PLA matrix, the enzymatically hydrolyzed porogen, and the compatibilizer. After melt blending and meltblowing, it is dispersed within the PLA fibers, providing uniformly distributed adsorption sites for subsequent loading of bio-enzymes. Using PLA resin as a matrix, the enzymatically hydrolyzed porogen, mesoporous silica, and compatibilizer are added, and the mixture is stirred at a constant temperature to achieve uniform dispersion of each component. The mixed raw material is then fed into a twin-screw extruder. A gradient temperature is set to achieve complete melting of the PLA resin. At a specific location in the metering section of the twin-screw extruder, an oxidant is added separately via a side-feeding device. The temperature conditions at this location promote the rapid decomposition of the oxidant, generating active free radicals. For example, the oxidant ammonium persulfate decomposes upon heating in the metering section of the twin-screw extruder, generating… The reactive free radical, possessing high reactivity, can attack the hydrogen atoms at the tertiary carbon sites on the polylactic acid (PLA) molecular chain, causing the PLA molecular chain to form a carbon free radical. This carbon free radical can further break down, leading to the PLA molecular chain fracture and the formation of molecular chain gaps. This disrupts the original tight molecular arrangement and provides a structural basis for subsequent pore formation.

[0028] The melt, after being melt-blended by twin-screw extrusion, is pumped to the meltblown die and stretched into polylactic acid (PLA) fibers under set meltblown process conditions. After meltblowing, a buffer solution with a suitable pH is prepared to dissolve the enzymes and prepare a bio-enzyme solution. The PLA fibers are then immersed in the bio-enzyme solution. At this point, the enzymes enter the channels of the mesoporous silica through adsorption. The buffer solution provides a suitable catalytic environment for the enzymes. The activated enzymes, due to their substrate specificity (e.g., α-amylase catalyzes the degradation of hydroxypropyl starch, and chitosanase catalyzes the degradation of hydroxypropyl chitosan), undergo specific degradation reactions with the enzymatic porogens inside the fibers, converting the porogens into water-soluble small molecules such as glucose and glucosamine. These small molecules detach from the matrix through water washing, and the porogens that originally occupied space form pores. The formed pores combine with the gaps in the molecular chains to obtain a molecular-level porous network that runs through the fibers, expanding the intermolecular gaps. The molecular structure of polylactic acid fiber is regulated, and the gaps between molecules are significantly expanded, which not only improves the soft feel of the fiber, but also provides sufficient channels for the penetration of dye molecules, thereby improving the color depth and color fastness of dyeing.

[0029] Beneficial technical effects:

[0030] This application discloses a method for preparing polylactic acid (PLA) fibers. Using PLA resin as a matrix, mesoporous silica, a compatibilizer, an enzymatic pore-forming agent, and an oxidant are mixed as a meltblown raw material. The oxidant decomposes at specific positions on a twin-screw extruder to generate active free radicals. These free radicals attack the ester bonds in the PLA molecular chain, causing them to break and generate carboxyl (-COOH) and hydroxyl (-OH) end groups, thus disrupting the tightly packed structure of the fiber and creating gaps in the molecular chains. The meltblown PLA fibers are then subjected to enzymatic hydrolysis. The enzymatic pore-forming agent degrades the bio-enzyme molecules within the fiber, generating water-soluble small molecules that detach from the fiber after washing. The space occupied by the pore-forming agent forms pores. These pores, combined with the gaps in the molecular chains, give the fiber a porous network structure, thereby expanding the intermolecular gaps, improving the hand feel of the PLA fiber, and providing ample channels for dye penetration to enhance dyeing performance. Attached Figure Description

[0031] Figure 1 This invention provides a flowchart of a method for preparing polylactic acid fiber. Detailed Implementation

[0032] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application will be provided below.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment provides a method for preparing polylactic acid fibers, including the following steps:

[0036] S1. Mesoporous silica with a pore size of 2 nm and a specific surface area of ​​600 m² / g was dispersed in deionized water, stirred at 25 °C and 200 rpm for 2 h, and then dried under vacuum at 60 °C and 0.06 MPa for 2 h to obtain mesoporous silica powder.

[0037] S2. Using polylactic acid resin with a melt index of 80 g / 10 min as the matrix, add hydroxypropyl chitosan and polyethylene glycol, and stir at 80°C and 200 rpm for 1 h to obtain a mixed raw material;

[0038] S3. Add the mixed raw materials to a twin-screw extruder, set the gradient temperature to 120℃ for the hopper section, 150℃ for the compression section, and 160℃ for the metering section, and the screw speed to 500 rpm; add ammonium persulfate through a side feeding device at 1 / 3 of the metering section, and then convey the melt to the meltblown die head. Meltblown the melt under the conditions of die head temperature 165℃, hot air temperature 170℃, hot air velocity 0.3m / s, receiving distance 8cm, and melt pump pressure 5MPa to obtain polylactic acid fiber;

[0039] S4. Preheat an acetate-sodium acetate buffer solution with a pH of 5.0 in a constant temperature water bath at 25°C. Add chitosanase powder at a solid-liquid ratio of 0.5 mg: 1 mL and stir at 50 rpm for 15 min to obtain a bio-enzyme solution. Immerse the melt-blown polylactic acid fiber in the bio-enzyme solution at a solid-liquid ratio of 1 g: 20 mL and enzymatically hydrolyze it at 40°C and 50 rpm for 3 h. After enzymatic hydrolysis, wash it three times with 40°C warm water for 15 min each time, and then vacuum dry it at 60°C and 0.06 MPa for 2 h to obtain polylactic acid fiber.

[0040] Throughout the preparation process, the mass ratio of mesoporous silica, polylactic acid resin, compatibilizer, enzymatic porogen, and oxidant is 20:64:5:10:1.

[0041] Example 2

[0042] like Figure 1 As shown, this embodiment provides a method for preparing polylactic acid fibers, including the following steps:

[0043] S1. Mesoporous silica with a pore size of 50 nm and a specific surface area of ​​500 m² / g was dispersed in deionized water, stirred at 35 °C and 300 rpm for 4 h, and then dried under vacuum at 80 °C and 0.09 MPa for 4 h to obtain mesoporous silica powder.

[0044] S2. Using polylactic acid resin with a melt index of 100 g / 10 min as the matrix, hydroxypropyl starch and sorbitan monolaurate were added, and the mixture was stirred at 100 °C and 300 rpm for 2 h to obtain the mixed raw material.

[0045] S3. Add the mixed raw materials to a twin-screw extruder, set the gradient temperature to 140℃ for the hopper section, 160℃ for the compression section, and 170℃ for the metering section, and the screw speed to 600 rpm; add potassium persulfate at 1 / 3 of the metering section through a side feeding device, and then convey the melt to the meltblown die head. Meltblown under the conditions of die head temperature 175℃, hot air temperature 180℃, hot air velocity 0.6m / s, receiving distance 15cm, and melt pump pressure 10MPa to obtain polylactic acid fiber containing pore-forming agent and mesoporous silica.

[0046] S4. Preparation of bio-enzyme solution: Preheat a citric acid-sodium citrate buffer solution with a pH of 6.5 in a 35°C constant temperature water bath, add α-amylase powder at a solid-liquid ratio of 1.5 mg: 1 mL, and stir at 100 rpm for 30 min to obtain a bio-enzyme solution; immerse the melt-blown polylactic acid fiber in the bio-enzyme solution at a solid-liquid ratio of 1 g: 50 mL, and enzymatically hydrolyze it at 55°C and 100 rpm for 6 h; after enzymatic hydrolysis, wash it 5 times with 50°C warm water for 20 min each time, and then vacuum dry it at 80°C and 0.09 MPa for 4 h to obtain polylactic acid fiber.

[0047] Throughout the preparation process, the mass ratio of mesoporous silica, polylactic acid resin, compatibilizer, enzymatic porogen, and oxidant is 30:40:8:20:2.

[0048] Example 3

[0049] like Figure 1 As shown, this embodiment provides a method for preparing polylactic acid fibers, including the following steps:

[0050] S1. Mesoporous silica with a pore size of 26 nm and a specific surface area of ​​520 m² / g was dispersed in deionized water, stirred at 30 °C and 250 rpm for 3 h, and then dried under vacuum at 70 °C and 0.075 MPa for 3 h to obtain mesoporous silica powder.

[0051] S2. Using polylactic acid resin with a melt index of 90 g / 10 min as the matrix, carboxymethyl cellulose and polyethylene glycol were added, and the mixture was stirred at 90°C and 250 rpm for 1.5 h to obtain a mixed raw material.

[0052] S3. Add the mixed raw materials to a twin-screw extruder, set the gradient temperature to 130℃ for the hopper section, 155℃ for the compression section, and 165℃ for the metering section, and the screw speed to 550 rpm; add ammonium persulfate at 1 / 3 of the metering section through a side feeding device, and then convey the melt to the meltblown die head. Meltblown under the conditions of die head temperature 170℃, hot air temperature 175℃, hot air velocity 0.45m / s, receiving distance 11.5cm, and melt pump pressure 7.5MPa to obtain polylactic acid fiber containing pore-forming agent and mesoporous silica.

[0053] S4. A citric acid-sodium citrate buffer solution with a pH of 5.7 was preheated in a 30°C constant temperature water bath. Cellulase powder was added at a solid-liquid ratio of 1.0 mg: 1 mL, and the mixture was stirred at 75 rpm for 22.5 min to obtain a bio-enzyme solution. The melt-blown polylactic acid fiber was immersed in the bio-enzyme solution at a solid-liquid ratio of 1 g: 35 mL and enzymatically hydrolyzed at 47.5°C and 75 rpm for 4.5 h. After enzymatic hydrolysis, the fiber was washed four times with 45°C warm water for 17.5 min each time, and then vacuum dried at 70°C and 0.075 MPa for 3 h to obtain polylactic acid fiber.

[0054] Throughout the preparation process, the mass ratio of mesoporous silica, polylactic acid resin, compatibilizer, enzymatic porogen, and oxidant was 25:51:7.5:15:1.5.

[0055] Example 4

[0056] like Figure 1 As shown, this embodiment provides a method for preparing polylactic acid fibers, including the following steps:

[0057] S1. Mesoporous silica with a pore size of 10 nm and a specific surface area of ​​550 m² / g was dispersed in deionized water, stirred at 28 °C and 220 rpm for 2.5 h, and then dried under vacuum at 65 °C and 0.08 MPa for 2.5 h to obtain mesoporous silica powder.

[0058] S2. Using polylactic acid resin with a melt index of 85 g / 10 min as the matrix, hydroxypropyl chitosan and sorbitan monolaurate were added, and the mixture was stirred at 85°C and 230 rpm for 1.2 h to obtain the mixed raw material.

[0059] S3. Add the mixed raw materials to a twin-screw extruder, set the gradient temperature to 125℃ for the hopper section, 153℃ for the compression section, and 163℃ for the metering section, and the screw speed to 530 rpm; add potassium persulfate at 1 / 3 of the metering section through a side feeding device, and then convey the melt to the meltblown die head. Meltblown under the conditions of die head temperature 168℃, hot air temperature 173℃, hot air velocity 0.4 m / s, receiving distance 10 cm, and melt pump pressure 6 MPa to obtain polylactic acid fiber containing pore-forming agent and mesoporous silica.

[0060] S4. Preheat an acetate-sodium acetate buffer solution with a pH of 5.3 in a constant temperature water bath at 28°C. Add chitosanase powder at a solid-liquid ratio of 0.8 mg:1 mL and stir at 60 rpm for 20 min to obtain a bio-enzyme solution. Immerse the melt-blown polylactic acid fiber in the bio-enzyme solution at a solid-liquid ratio of 1 g:30 mL and enzymatically hydrolyze it at 45°C and 65 rpm for 4 h. After enzymatic hydrolysis, wash it three times with 42°C warm water for 18 min each time, and then vacuum dry it at 65°C and 0.07 MPa for 2.5 h to obtain polylactic acid fiber.

[0061] Throughout the preparation process, the mass ratio of mesoporous silica, polylactic acid resin, compatibilizer, enzymatic porogen, and oxidant was 23:58:7:10:2.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing polylactic acid fibers. The difference between this comparative example and Example 1 is that no biological enzymes are used in this comparative example, but the other process parameters and operating steps are exactly the same as in Example 1.

[0064] Comparative Example 2

[0065] This comparative example provides a method for preparing polylactic acid fibers. The difference between this comparative example and Example 1 is that no oxidant is used in this comparative example S3, while the other process parameters and operating steps are exactly the same as in Example 1.

[0066] The polylactic acid fibers prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Table 1.

[0067] Table 1. Performance test results of polylactic acid fibers prepared in Examples 1-4 and Comparative Examples 1-2

[0068]

[0069] Examples 1-4 utilize mesoporous silica loaded with bio-enzymes and cross-linked for fixation. This, combined with oxidant modification and enzymatic hydrolysis to induce pores, achieves molecular structure regulation of polylactic acid (PLA) fibers. The pretreated mesoporous silica is uniformly dispersed within the PLA matrix, providing adsorption sites for the bio-enzymes of the hydrolytic pore-forming agent that penetrate the fiber after meltblown molding. The oxidant decomposes under specific temperature conditions in a twin-screw extruder, generating active free radicals that break the ester bonds in the PLA molecular chain, creating structural gaps. The meltblown PLA fibers are then subjected to enzymatic hydrolysis. Under suitable pH and temperature conditions, the bio-enzymes specifically degrade the hydrolytic pore-forming agent, forming water-soluble small molecules. After washing away from the matrix, these molecules detach, creating pores. These pores, along with the molecular chain gaps, form a porous network that permeates the fiber. This approach expands the internal porosity of PLA fibers at the molecular level, improving the fiber's softness and providing ample channels for dye molecule penetration. This achieves simultaneous optimization of mechanical properties, softness, and dyeing performance, while preserving the biodegradability of PLA fibers.

[0070] Comparative Example 1 did not add any biological enzymes and relied solely on oxidant modification to form molecular chain gaps. It lacked the specific degradation and pore-forming effect of enzymatic hydrolysis pore-forming agents, and could not form pores. The improvement in fiber hand feel was limited, the penetration of dye molecules was hindered, and the improvement in dyeing depth and color fastness was not significant. It failed to solve the core defects of polylactic acid fiber.

[0071] Comparative Example 2 did not add an oxidant; it only formed pores through enzymatic hydrolysis of the pore-forming agent. Lacking the chain-breaking modification of polylactic acid molecular chains by active free radicals, the polylactic acid molecular chains remained in their original tightly packed state and did not form a porous network structure. The expansion of the internal voids of the fiber was limited, resulting in a slight improvement in softness and hand feel, poor pore dispersion, low dye molecule penetration efficiency, and the synergistic optimization effect of dyeing performance and mechanical properties did not meet expectations.

[0072] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.

Claims

1. A method for preparing polylactic acid fiber, characterized in that, Includes the following steps: S1. Disperse mesoporous silica in deionized water, stir, and then vacuum dry to obtain mesoporous silica powder; S2. Add the enzymatic porogen, the above-mentioned mesoporous silica powder and compatibilizer to the polylactic acid resin matrix, and stir to obtain a mixed raw material; S3. Add the above mixed raw materials to a twin-screw extruder, set a gradient temperature for melt blending, add an oxidant at a set position in the metering section of the twin-screw extruder through a side feeding device, and then transport the melt after twin-screw extrusion to a melt-blowing die for melt-blowing to obtain polylactic acid fiber; S4. Prepare a biological enzyme solution using a buffer solution, place the meltblown polylactic acid fiber in the biological enzyme solution for enzymatic hydrolysis, wash with warm water after enzymatic hydrolysis, and then dry to obtain a polylactic acid fiber.

2. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S1, the pore size of the mesoporous silica is 2-50 nm, and the specific surface area is 500-600 m² / g; the stirring temperature is 25-35℃, the stirring time is 2-4 h, and the stirring speed is 200-300 rpm.

3. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S2, the melt index of the polylactic acid resin is 80-100 g / 10 min; The enzymatic hydrolytic porogen includes any one of hydroxypropyl chitosan, hydroxypropyl starch, and carboxymethyl cellulose; The compatibilizer includes either polyethylene glycol or sorbitan monolaurate.

4. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S2, the stirring temperature is 80-100℃ and the stirring time is 1-2 hours.

5. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S3, the oxidant is ammonium persulfate or potassium persulfate.

6. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S3, the gradient temperature is: 120-140℃ for the hopper section, 150-160℃ for the compression section, and 160-170℃ for the metering section; the screw speed of the twin-screw extruder is 500-600 rpm; and the set position is 1 / 3 of the metering section.

7. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S3, the meltblown process conditions are: die head temperature 165-175℃, hot air temperature 170-180℃, hot air velocity 0.3-0.6m / s, receiving distance 8-15cm, and melt pump pressure 5-10MPa.

8. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S4, the bioenzyme in the bioenzyme solution is any one of chitosanase, α-amylase, and cellulase; The buffer solution is an acetate-sodium acetate buffer solution or a citric acid-sodium citrate buffer solution, and the pH of the system is adjusted to 5.0-6.

5. The enzymatic hydrolysis treatment is carried out at a temperature of 40-55℃ for 3-6 hours, with continuous stirring at a speed of 50-100 rpm during the process. The temperature of the warm water washing is 40-50℃, the number of washing cycles is 3-5, and the washing time for each cycle is 15-20 minutes. The drying process is vacuum drying, with a drying temperature of 60-80℃, a drying time of 2-4 hours, and a vacuum degree of 0.06-0.09MPa.

9. The method for preparing polylactic acid fiber according to claim 1, characterized in that, In S4, the preparation method of the bio-enzyme solution is as follows: the buffer solution is preheated in a constant temperature water bath at 25-35℃, the bio-enzyme is added to the buffer solution at a solid-liquid ratio of (0.5-1.5) mg: 1 mL, and then stirred at a speed of 50-100 rpm for 15-30 min to obtain the bio-enzyme solution; the solid-liquid ratio of the polylactic acid fiber and the bio-enzyme solution is 1 g: (20-50) mL.

10. The method for preparing polylactic acid fiber according to claim 1, characterized in that, Throughout the preparation process, the mass ratio of the mesoporous silica, polylactic acid resin, compatibilizer, enzymatic porogen and oxidant is (20-30): (40-64): (5-8): (10-20): (1-2).

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