Preparation method and application of hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber

Abstract

This invention relates to the field of biomass textile fiber preparation technology, specifically disclosing a method for preparing and applying a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid (PLA) fiber. The PLA fiber preparation method includes the following steps: S1, preparation of ethylene glycol diglycidyl etherification of PLA with phytic acid; S2, preparation of an organic-inorganic composite auxiliary agent; S3, melt spinning the mixture of the two to prepare the composite modified PLA fiber. This method firmly integrates phytic acid structures into the PLA molecule, endowing the fiber with durable high flame retardancy, avoiding the problems of flame retardant precipitation and deterioration of fiber performance caused by blending conventional flame retardants with PLA. The hydrophilic phytic acid and cationic grafted monomer units reduce the hydrophobicity of PLA fibers and enhance their hydrophilicity, while the cationic grafted monomer units and titanium dioxide synergistically impart strong antibacterial properties to the PLA fibers. It is highly suitable for use as a textile fiber with multiple properties of hydrophilicity, antibacterial properties, and flame retardancy.

Description

Technical Field

[0001] This invention relates to the field of biomass textile fiber preparation technology, and in particular to a method for preparing and applying a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber. Background Technology

[0002] In recent years, polylactic acid (PLA) has been widely used in biomedicine, packaging, and automotive fields. As a biodegradable and environmentally friendly bio-based material, its application as fibers in the textile industry has received increasing attention. However, current PLA fibers still have some shortcomings in practical applications. For example, PLA fibers have strong hydrophobicity, resulting in unsatisfactory performance in moisture absorption and wicking, and wearing comfort. Furthermore, this strong hydrophobicity leads to serious static electricity problems, affecting the performance of PLA fibers as apparel materials. The limiting oxygen index (LOI) of pure PLA fibers is generally around 20%–26%, classifying them as flammable materials. Solving this problem is crucial for improving its performance as a textile fiber in applications requiring good flame retardant properties. Conventional methods for improving flame retardant performance involve mixing flame retardants with the base material. However, the physical bonding between the flame retardant and the base material can lead to precipitation due to poor compatibility, affecting the durability of the flame retardant. Excessive addition can also deteriorate the mechanical properties and processability of the material. In addition, polylactic acid fibers have limited antibacterial properties, which cannot meet the requirements of some applications with high hygiene and health requirements, such as medical dressings and functional clothing.

[0003] Therefore, if hydrophilic groups with flame-retardant effects can be introduced into the polylactic acid (PLA) molecular chain using technical methods, it is expected to endow PLA with long-lasting flame retardancy without issues such as precipitation. Furthermore, if hydrophilic and antibacterial organic polymers are branched onto inorganic nano-silica with photocatalytic antibacterial properties to form an organic-inorganic composite agent, the synergistic effect between the two is expected to impart excellent antibacterial properties to PLA fibers. Simultaneously, the hydroxyl groups on the hydrophilic polymer chains and the inorganic agent molecules will synergistically reduce the hydrophobicity of the PLA fibers. Therefore, further melt-spinning PLA fibers with composite agents and modified PLA is expected to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings. This invention proposes a method for preparing and applying a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber. This technology endows polylactic acid fiber with excellent hydrophilic, antibacterial, and flame-retardant properties. It is highly suitable for use as a textile fiber with multiple hydrophilic, antibacterial, and flame-retardant properties.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber, the method comprising the following steps: S1. Preparation of ethylene glycol diglycidyl etherified polylactic acid with phytic acid; Ethylene glycol diglycidyl ether is reacted with phytic acid to obtain ethylene glycol diglycidyl-phytic acid; then, it is added to a mixed solution of polylactic acid and dichloromethane for further reaction treatment to obtain ethylene glycol diglycidyl-phytic acid etherified polylactic acid. S2. Preparation of organic-inorganic composite additives Inorganic nano-silica was prepared into a dispersion with distilled water, organic methacryloyloxyethyltrimethylammonium chloride was added and reacted under acidic conditions. After the reaction, the organic-inorganic composite additive was obtained by centrifugation, washing and drying. S3, Spinning of composite modified polylactic acid fibers After mixing, grinding, and drying the ethylene glycol diglycidyl-phytate etherified polylactic acid with the organic-inorganic composite additive sample, the mixture is melt-extruded, cured, ground, and dried in a screw extruder. Then, it is added to a twin-screw extruder, and the melting temperature and screw speed are controlled for extrusion spinning, curing, and winding to obtain composite modified polylactic acid fiber.

[0006] Preferably, in step S1, the preparation process of the ethylene glycol diglycidyl-phytate etherified polylactic acid is as follows: S11. Place ethylene glycol diglycidyl ether into an Erlenmeyer flask containing phytic acid, seal and shake to react, and obtain ethylene glycol diglycidyl-phytic acid. S12. Polylactic acid is dissolved in dichloromethane to obtain a mixed solution, and the pH value of the mixed solution is adjusted to alkaline. Then, ethylene glycol diglycidyl-phytic acid is added to the mixed solution to react. After the reaction, the solvent is evaporated, the solution is washed multiple times with ethanol aqueous solution, filtered, and dried to obtain ethylene glycol diglycidyl-phytic acid etherified polylactic acid.

[0007] Preferably, in step S2, the mass concentration of the dispersion is 1-15%; the mass ratio of the silica to the methacryloyloxyethyltrimethylammonium chloride is 30:4-16; and the organic-inorganic composite additive is silica-grafted polymethacryloyloxyethyltrimethylammonium chloride.

[0008] Preferably, in step S2, the acidic conditions are: temperature 30-50℃, pH=3-4.5, and time 3-8h.

[0009] Preferably, in step S11, the mass ratio of ethylene glycol diglycidyl ether to phytic acid is 80:14-28; the reaction conditions for step S11 are: temperature 60-80℃, time 2.5-6.5h.

[0010] Preferably, in step S12, the mass ratio of polylactic acid to ethylene glycol diglycidyl ether-phytic acid is 150:7.5-30.

[0011] Preferably, in step S12, the pH value of the mixed solution is 8.5-10, and the reaction conditions for step S12 are: temperature 30-55℃, time 3-7.5h.

[0012] Preferably, in step S3, the mass percentage of the organic-inorganic composite p-ethylene glycol diglycidyl-phytate etherified polylactic acid is 0.5-2.5%.

[0013] Preferably, in step S3, the melt temperature of the twin-screw extruder is 180-230℃, the screw speed is 20-65 rpm, and the winding speed is 25-60 m / min.

[0014] Preferably, the application of the composite modified polylactic acid fiber prepared by the above method is characterized in that the composite modified polylactic acid fiber is used as a textile fiber.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (1) The method provided by the present invention prepares an organic (polymethylpropionyloxyethyltrimethylammonium chloride)-inorganic (silica) composite additive by performing hydrophilic cationic graft polymerization on nano silica. The hydrophobicity of polylactic acid fiber is reduced by utilizing the synergistic effect between the hydrophilic functional groups on the organic polymer chain and the hydrophilic hydroxyl groups on the inorganic silica. Polylactic acid is modified by incorporating ethylene glycol diglycidyl-phytic acid into its molecular chain. The hydrophilic phytic acid can also reduce the hydrophobicity of polylactic acid fiber and improve its hydrophilicity.

[0016] (2) The method provided by the present invention utilizes the synergistic effect between the quaternary ammonium cations with direct antibacterial and bactericidal effects on the hydrophilic functional groups of the organic polymer chain and titanium dioxide with photocatalytic antibacterial properties to endow polylactic acid fibers with strong antibacterial and bacteriostatic properties. At the same time, the hydrophilic quaternary ammonium cation functional groups can also eliminate and conduct the static negative charge generated during the use of polylactic acid fibers, thereby reducing the static electricity problem.

[0017] (3) The method provided by the present invention is based on the principle of “like dissolves like”. It introduces hydrophilic grafted side chains on the additives and hydrophilic phytic acid molecular structures on the polylactic acid molecular chains. This will improve the compatibility between the additives and polylactic acid molecules, as well as the dispersibility of the additives in polylactic acid. The environmentally friendly phytic acid gives polylactic acid long-lasting high flame retardancy, avoiding the problem of flame retardant precipitation and deterioration of polylactic acid performance when conventional flame retardants are blended with polylactic acid. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a process diagram of the preparation method of the present invention; Figure 2 The water contact angle diagrams for the original polylactic acid fiber and the composite modified polylactic acid fiber proposed in this invention are shown. Figure 3 The colony diagrams are of the original bacteria, original polylactic acid fiber, and composite modified polylactic acid fiber samples proposed in this invention. Figure 4 These are combustion characteristic diagrams of the original polylactic acid fiber and the composite modified polylactic acid fiber proposed in this invention. 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 a part of the embodiments of the present invention, and not all of the embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This invention proposes a method for preparing hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber, the method steps of which are as follows: S1: Preparation of ethylene glycol diglycidyl-phytate etherified polylactic acid Weigh 100 g of ethylene glycol diglycidyl ether (dry weight) into a 500 mL Erlenmeyer flask. Weigh 28 g of phytic acid and add it to the flask. Seal the flask with a glass stopper, shake gently by hand until well mixed, and then place it in a water bath shaker set at 75°C for 4.5 hours to obtain ethylene glycol diglycidyl-phytic acid. Dissolve 150 g of polylactic acid (dry weight) in dichloromethane, stir well, and transfer to a three-necked flask. Heat the flask to 45°C, add 30 g of ethylene glycol diglycidyl-phytic acid, adjust the pH of the system to 8.5-10, and react for 6.5 hours. After evaporating the solvent in a fume hood, pulverize the solid and wash it with an ethanol-water solution (70:30) three times by suction filtration. Dry the solid in an oven at 45°C, pulverize, and grind it to obtain ethylene glycol diglycidyl-phytic acid etherified polylactic acid.

[0021] S2: Preparation of organic-inorganic composite additives Weigh 30 grams of silica (dry weight) into a four-necked flask, add distilled water and stir thoroughly to form a 5% (w / w) dispersion. Adjust the pH to 3-4.5 using hydrochloric acid solution. Heat the mixture to 33°C in a water bath with stirring, and purge with nitrogen for half an hour. Simultaneously, slowly add a solution of 10 grams of methacryloyloxyethyltrimethylammonium chloride, a 0.5% (w / w) aqueous solution of ferrous ammonium sulfate, and a 1% (w / w) aqueous solution of hydrogen peroxide. After the addition is complete, continue the reaction for 7 hours. Wash the sample four times with ethanol by centrifugation, then twice with distilled water by centrifugation. Dry the sample in a 60°C oven for 24 hours to obtain an organic-inorganic composite additive: silica-grafted polymethacryloyloxyethyltrimethylammonium chloride.

[0022] S3: Spinning of composite modified polylactic acid fibers The samples obtained from S1 and S2 were mixed at a mass percentage of 0.5% (the latter to the former). After crushing, grinding, and drying, the mixture was added to a screw extruder, heated to 195℃ for melt extrusion and solidification. After further crushing, grinding, and drying, the mixture was added to a twin-screw extruder for melt extrusion spinning, solidification, and winding to obtain composite modified polylactic acid fiber sample I. The melt spinning temperature was 195℃, the screw speed was 35 rpm, and the winding speed was 45 m / min.

[0023] Example 2 This invention proposes a method for preparing hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber, the method steps of which are as follows: S1: Preparation of ethylene glycol diglycidyl-phytate etherified polylactic acid Weigh 100 g of ethylene glycol diglycidyl ether (dry weight) into a 500 mL Erlenmeyer flask. Weigh 28 g of phytic acid and add it to the flask. Seal the flask with a glass stopper, shake gently by hand until well mixed, and then place it in a water bath shaker set at 75°C for 4.5 hours to obtain ethylene glycol diglycidyl-phytic acid. Dissolve 150 g of polylactic acid (dry weight) in dichloromethane, stir well, and transfer to a three-necked flask. Heat the flask to 45°C, add 30 g of ethylene glycol diglycidyl-phytic acid, adjust the pH of the system to 8.5-10, and react for 6.5 hours. After evaporating the solvent in a fume hood, pulverize the solid and wash it with an ethanol-water solution (70:30) three times by suction filtration. Dry the solid in an oven at 45°C, pulverize, and grind it to obtain ethylene glycol diglycidyl-phytic acid etherified polylactic acid.

[0024] S2: Preparation of organic-inorganic composite additives Weigh 30 grams of silica (dry weight) into a four-necked flask, add distilled water and stir thoroughly to form a 5% (w / w) dispersion. Adjust the pH to 3-4.5 using hydrochloric acid solution. Heat the mixture to 33°C in a water bath with stirring, and purge with nitrogen for half an hour. Simultaneously, slowly add a solution of 10 grams of methacryloyloxyethyltrimethylammonium chloride, a 0.5% (w / w) aqueous solution of ferrous ammonium sulfate, and a 1% (w / w) aqueous solution of hydrogen peroxide. After the addition is complete, continue the reaction for 7 hours. Wash the sample four times with ethanol by centrifugation, then twice with distilled water by centrifugation. Dry the sample in a 60°C oven for 24 hours to obtain an organic-inorganic composite additive: silica-grafted polymethacryloyloxyethyltrimethylammonium chloride.

[0025] S3: Spinning of composite modified polylactic acid fibers The samples obtained from S1 and S2 were mixed at a mass percentage of 1.5% (the latter to the former). After crushing, grinding, and drying, the mixture was added to a screw extruder, heated to 195℃ for melt extrusion and solidification. After further crushing, grinding, and drying, the mixture was added to a twin-screw extruder, heated for melt extrusion spinning, solidification, and winding to obtain composite modified polylactic acid fiber sample II. The melt spinning temperature was 200℃, the screw speed was 40 rpm, and the winding speed was 45 m / min.

[0026] Example 3 This invention proposes a method for preparing hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber, the method steps of which are as follows: S1: Preparation of ethylene glycol diglycidyl-phytate etherified polylactic acid Weigh 100 g of ethylene glycol diglycidyl ether (dry weight) into a 500 mL Erlenmeyer flask. Weigh 28 g of phytic acid and add it to the flask. Seal the flask with a glass stopper, shake gently by hand until well mixed, and then place it in a water bath shaker set at 75°C for 4.5 hours to obtain ethylene glycol diglycidyl-phytic acid. Dissolve 150 g of polylactic acid (dry weight) in dichloromethane, stir well, and transfer to a three-necked flask. Heat the flask to 45°C, add 30 g of ethylene glycol diglycidyl-phytic acid, adjust the pH of the system to 8.5-10, and react for 6.5 hours. After evaporating the solvent in a fume hood, pulverize the solid and wash it with an ethanol-water solution (70:30) three times by suction filtration. Dry the solid in an oven at 45°C, pulverize, and grind it to obtain ethylene glycol diglycidyl-phytic acid etherified polylactic acid.

[0027] S2: Preparation of organic-inorganic composite additives Weigh 30 grams of silica (dry weight) into a four-necked flask, add distilled water and stir thoroughly to form a 5% (w / w) dispersion. Adjust the pH to 3-4.5 using hydrochloric acid solution. Heat the mixture to 33°C in a water bath with stirring, and purge with nitrogen for half an hour. Simultaneously, slowly add a solution of 10 grams of methacryloyloxyethyltrimethylammonium chloride, a 0.5% (w / w) aqueous solution of ferrous ammonium sulfate, and a 1% (w / w) aqueous solution of hydrogen peroxide. After the addition is complete, continue the reaction for 7 hours. Wash the sample four times with ethanol by centrifugation, then twice with distilled water by centrifugation. Dry the sample in a 60°C oven for 24 hours to obtain an organic-inorganic composite additive: silica-grafted polymethacryloyloxyethyltrimethylammonium chloride.

[0028] S3: Spinning of composite modified polylactic acid fibers Samples S1 and S2 were mixed at a mass percentage of 2.5% (supplement to former). After pulverizing, grinding, and drying, the mixture was added to a screw extruder, heated to 195℃ for melt extrusion and solidification. After further pulverizing, grinding, and drying, the mixture was added to a twin-screw extruder for melt extrusion spinning, solidification, and winding to obtain composite modified polylactic acid fiber sample III. The melt spinning temperature was 210℃, the screw speed was 38 rpm, and the winding speed was 40 m / min.

[0029] Comparative Example 4 The preparation method of virgin polylactic acid (PLA) fiber is as follows: virgin PLA is pulverized, ground, and dried, then melt-extruded and solidified in a screw extruder at 195°C. After further pulverization, grinding, and drying, it is melt-extruded, spun, solidified, and wound in a screw extruder to obtain virgin PLA fiber. The melt spinning temperature is 210°C, the screw speed is 38 rpm, and the winding speed is 40 m / min.

[0030] like Figure 1 As shown: An organic-inorganic composite additive was prepared by grafting methacryloyloxyethyltrimethylammonium chloride monomer onto silica via a redox reaction; polylactic acid masterbatch underwent an etherification reaction with ethylene glycol diglycidyl-phytic acid, successfully incorporating the latter into the polylactic acid molecular chain, thus obtaining ethylene glycol diglycidyl-phytic acid-grafted polylactic acid; finally, the ethylene glycol diglycidyl-phytic acid-etherified polylactic acid was mixed with the organic-inorganic composite additive sample, milled, and dried, then melt-extruded, cured, milled, and dried in a screw extruder, and then fed into a twin-screw extruder. The melt temperature and screw speed were controlled, and after extrusion spinning, curing, and winding, composite modified polylactic acid fibers were obtained.

[0031] Using deionized water, the contact angles of polylactic acid fibers before and after modification were tested using a contact angle meter. The water contact angle test results are as follows: Figure 2As shown in the contact angle diagram, the original polylactic acid (PLA) fiber has a contact angle of 102°, exhibiting significant hydrophobic properties. This hydrophobicity mainly stems from the large number of hydrophobic ester groups present in the PLA molecular chain. The contact angle of the composite modified PLA fiber sample is approximately 56°, exhibiting strong hydrophilic properties. These findings indicate that the hydrophilic polar hydroxyl groups and cationic functional groups on silica, as well as the hydrophilic phytic acid functional groups introduced into the PLA molecular chain, significantly reduce the strong hydrophobicity of PLA fibers, thus endowing them with strong hydrophilic characteristics.

[0032] Antibacterial activity was evaluated using a colony counting method: The fiber sample was ground into powder, and 0.1 g of the sample was evenly distributed in 10 mL of PBS. 0.1 mL of bacterial suspension was added, and the sample was vortexed for 10 seconds after 5 minutes to disperse the bacteria. The bacterial suspension was serially diluted 10-fold using conical centrifuge tubes and evenly added to the surface of solid culture dishes. The dishes were incubated at 37°C for 24 hours, and the colony count was measured to calculate the antibacterial rate.

[0033] like Figure 3 As shown, the number of bacterial colonies in both types of fibers was significantly lower than in the original polylactic acid (PLA) fiber. Calculations showed that the antibacterial rate of the original PLA fiber was 70.8%, while the colony count in the composite modified PLA fiber was almost zero, achieving an antibacterial rate of over 99.0%. The organic-inorganic composite additive (SiO2 grafted polymethacryloyloxyethyltrimethylammonium chloride) combined with PLA utilizes the synergistic effect of the cationic quaternary ammonium salt functional groups with antibacterial properties in the grafted side chains and the silica with antibacterial properties to endow the composite modified PLA fiber with excellent antibacterial properties. This PLA fiber with excellent antibacterial properties provides an important material basis for the development of high-performance antibacterial PLA fiber-based textiles and medical dressings.

[0034] like Figure 4 As shown: the melting tendency of composite modified polylactic acid (PLA) fibers is lower than that of original PLA fibers; the burning intensity of composite modified PLA fibers in a flame is weaker than that of original PLA fibers; original PLA fibers continue to burn after being removed from the flame, while composite modified PLA fibers extinguish immediately upon removal from the flame and do not continue burning. These results indicate that the introduction of phytic acid functional groups with flame-retardant properties endows composite modified PLA fibers with excellent flame retardancy.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber, characterized in that, The method includes the following steps: S1. Preparation of ethylene glycol diglycidyl etherified polylactic acid with phytic acid; Ethylene glycol diglycidyl ether is reacted with phytic acid to obtain ethylene glycol diglycidyl-phytic acid; then, it is added to a mixed solution of polylactic acid and dichloromethane for further reaction treatment to obtain ethylene glycol diglycidyl-phytic acid etherified polylactic acid. S2. Preparation of organic-inorganic composite additives Inorganic nano-silica was prepared into a dispersion with distilled water, organic methacryloyloxyethyltrimethylammonium chloride was added and reacted under acidic conditions. After the reaction, the organic-inorganic composite additive was obtained by centrifugation, washing and drying. S3, Spinning of composite modified polylactic acid fibers After mixing, grinding, and drying the ethylene glycol diglycidyl-phytate etherified polylactic acid with the organic-inorganic composite additive, the mixture is melt-extruded, cured, ground, and dried in a screw extruder. Then, it is added to a twin-screw extruder for extrusion spinning, curing, and winding to obtain composite modified polylactic acid fiber.

2. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 1, characterized in that, In step S1, the preparation process of the ethylene glycol diglycidyl-phytate etherified polylactic acid is as follows: S11. Place ethylene glycol diglycidyl ether into an Erlenmeyer flask containing phytic acid, seal and shake to react, and obtain ethylene glycol diglycidyl-phytic acid. S12. Polylactic acid is dissolved in dichloromethane to obtain a mixed solution, and the pH of the mixed solution is adjusted to alkaline. Then, ethylene glycol diglycidyl-phytic acid is added to the mixed solution to react. After the reaction, the solvent is evaporated, the solution is washed multiple times with ethanol aqueous solution, filtered, and dried to obtain ethylene glycol diglycidyl-phytic acid etherified polylactic acid.

3. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 1, characterized in that, In step S2, the mass concentration of the dispersion is 1-15%; the mass ratio of the silica to the methacryloyloxyethyltrimethylammonium chloride is 30:4-16; and the organic-inorganic composite additive is silica-grafted polymethacryloyloxyethyltrimethylammonium chloride.

4. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 1, characterized in that, In step S2, the acidic conditions are: temperature 30-50℃, pH=3-4.5, and time 3-8h.

5. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 2, characterized in that, In step S11, the mass ratio of ethylene glycol diglycidyl ether to phytic acid is 80:14-28; the reaction conditions for step S11 are: temperature 60-80℃, time 2.5-6.5h.

6. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 2, characterized in that, In step S12, the mass ratio of polylactic acid to ethylene glycol diglycidyl ether-phytic acid is 150:7.5-30.

7. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 2, characterized in that, In step S12, the pH value of the mixed solution is 8.5-10, and the reaction conditions for step S12 are: temperature 30-55℃, time 3-7.5h.

8. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 1, characterized in that, In step S3, the mass percentage of the organic-inorganic composite p-ethylene glycol diglycidyl-phytate etherified polylactic acid is 0.5-2.5%.

9. The method for preparing a hydrophilic-antibacterial-flame-retardant composite modified polylactic acid fiber according to claim 1, characterized in that, In step S3, the melt temperature of the twin-screw extruder is 180-230℃, the screw speed is 20-65 rpm, and the winding speed is 25-60 m / min.

10. An application of a composite modified polylactic acid fiber prepared by the method according to any one of claims 1-9, characterized in that, The composite modified polylactic acid fiber is used as a textile fiber.

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