Modified polylactic acid fiber and preparation method thereof

Abstract

The invention discloses a modified polylactic acid fiber and a preparation method thereof. The preparation method comprises the following steps: providing polybasic hydroxyl-terminated D-polylactic acid; the method comprises the following steps: respectively providing betaine-grafted D-polylactic acid and a poly (butylene adipate terephthalate)-epoxy-polyether co-modified organic silicon-D-polylactic acid copolymer by taking the multi-hydroxyl-terminated D-polylactic acid as a main raw material, wherein the poly (butylene adipate terephthalate)-epoxy-polyether co-modified organic silicon-D-polylactic acid copolymer; and carrying out Haake blending and melt spinning on the betaine-grafted D-polylactic acid, a poly (butylene adipate-co-modified organosilicon-D-polylactic acid) copolymer, L-polylactic acid, an antioxidant and an anti-hydrolysis agent, so as to obtain the modified polylactic acid fiber. The preparation method comprises the following steps: carrying out Haake blending and melt spinning on the betaine-grafted D-polylactic acid, poly (butylene adipate-co-modified organosilicon-D-polylactic acid copolymer, L-polylactic acid, the antioxidant and the anti-hydrolysis agent. The modified polylactic acid fiber prepared by the method has the characteristics of easy decontamination, hydrophilicity, high temperature resistance and high toughness, and can effectively avoid water washing shedding, and the comprehensive performance is obviously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polylactic acid fibers, and particularly relates to a modified polylactic acid fiber and a preparation method thereof. BACKGROUND

[0002] At present, fiber materials mainly include polyester, nylon and spandex, which are all petroleum-based non-degradable materials. After being discarded, these materials are difficult to degrade in the natural environment and will cause serious pollution to the environment if not properly treated. Polylactic acid (PLA) is a biobased degradable material, which is abundant in source, renewable, safe, biocompatible and has a wide application prospect. After being used, polylactic acid material can be completely degraded by microorganisms in the natural environment under certain conditions, and finally generates carbon dioxide and water, which will not pollute the environment, and is a recognized environmentally friendly material.

[0003] At present, the main method for preparing polylactic acid fibers is to directly melt and spin polylactic acid raw materials, and the polylactic acid obtained by this method often has defects such as poor high-temperature resistance, high hardness, poor toughness, difficult dyeing and easy pollution. At the same time, there are problems such as excessively high processing temperature and easy degradation of raw materials in the preparation process. Therefore, providing a high-temperature-resistant polylactic acid fiber with high flexibility and easy processing and a preparation method thereof is one of the main ways to solve the above problems. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a modified polylactic acid fiber and a preparation method thereof to solve the problems of the prior art. The modified polylactic acid fiber prepared by the method has significantly improved hydrophilicity and easy stain removal on the basis of maintaining high mechanical properties, and has the characteristics of better comprehensive performance and wider application scenarios.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] On the one hand, a preparation method of a modified polylactic acid fiber is provided, which comprises the following steps:

[0007] Providing a multi-element hydroxyl-terminated poly-L-lactic acid;

[0008] Providing betaine grafted poly-L-lactic acid and poly-terephthalate-hexanedioate butanediol-epoxy-polyether co-modified organosilicon-poly-L-lactic acid copolymer respectively, with the multi-element hydroxyl-terminated poly-L-lactic acid as the main raw material;

[0009] Blending the betaine grafted poly-L-lactic acid, the poly-terephthalate-hexanedioate butanediol-epoxy-polyether co-modified organosilicon-poly-L-lactic acid copolymer, the poly-L-lactic acid, the antioxidant and the hydrolysis-resistant agent by a Haake blender to obtain a polylactic acid fiber modification material;

[0010] The modified polylactic acid fiber is melt-spun to obtain a modified polylactic acid fiber.

[0011] In another aspect, the application provides a modified polylactic acid fiber prepared by the above method.

[0012] Compared with the prior art, the application has the following advantages:

[0013] 1. The modified polylactic acid fiber of the application has significantly improved hydrophilicity and easy decontamination, and has the characteristics of more comprehensive performance and more extensive application on the basis of maintaining high mechanical properties.

[0014] 2. The preparation method of the modified polylactic acid fiber prepared by the application includes providing a multi-hydroxyl-terminated PDLA, preparing betaine-grafted PDLA and PBAT-silicone-PDLA respectively using the multi-hydroxyl-terminated PDLA as a raw material, and blending the above betaine-grafted PDLA and PBAT-silicone-PDLA and PLLA to form a modified polylactic acid fiber. The PDLA segment forms SC crystallization with PLLA, which endows the fiber with high-temperature resistance. The modified polylactic acid fiber prepared by the above method can fully combine the performance characteristics of betaine, silicone and polyether segments, realize multi-party cooperation, and endow the polylactic acid fiber with higher hydrophilicity, flexibility, easy decontamination and high-temperature resistance.

[0015] 3. The preparation method of the modified polylactic acid fiber prepared by the application includes first preparing betaine-grafted PDLA and PBAT-silicone-PDLA, which has the characteristic of higher compatibility. Compared with directly connecting methacryloyl ethyl sulfobetaine and epoxy-polyether co-modified silicone to PDLA, the groups in the long chain of the fiber obtained by the method of the application are more densely connected to the main chain, which can fully combine the characteristics of PSBMA that can form a dense hydration layer to repel non-specific adsorption of bacteria, proteins and other biological molecules, and endow the fiber with stronger water washing and easy decontamination performance.

[0016] 4. The raw material for preparing the modified polylactic acid fiber prepared by the application has a wide adjustable range and a lower processing temperature, which is conducive to industrialization.

[0017] The technical solutions of the application will be further described in detail below in combination with the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The infrared spectrum of linear hydroxyl-terminated PDLA (HO-PDLA-OH) obtained in step 101 of Example 1;

[0019] Figure 2 The infrared spectrum of the product PDLA-g-PSBMA obtained in step 102 of Example 1;

[0020] Figure 3 A comparison chart of the water contact angle test results for Example 4 and Comparative Example 1. DETAILED DESCRIPTION

[0021] The technical solutions will be described clearly and completely below by combining with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0022] In the following description, the term "and / or" is used to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the cases of A alone, B alone and A and B existing at the same time. Wherein A and B can be singular or plural.

[0023] In the following description, the terms "include", "contain", "have" and "contain" and the like are all open terms, that is, they mean to include but not limited to.

[0024] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of the serial numbers does not mean the order of execution, and some or all steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0025] Those skilled in the art should understand that the numerical ranges in the embodiments of the present application should be understood as also specifically disclosing each intermediate value between the upper limit and the lower limit of the range. Each smaller range within any stated range or within any stated range of intermediate values and any other stated range or within the stated range of intermediate values is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0026] Unless otherwise specified, the technical / scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present application. All documents mentioned in the specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of conflict between any incorporated document and the content of the specification, the content of the specification shall prevail.

[0027] The technical principle adopted by the present application is as follows: based on the characteristics of high-temperature-resistant SC crystallization formed by left-handed PLLA and right-handed PDLA, PDLA-g-PSBMA is obtained by grafting betaine on the molecular chain of PDLA, PDLA-g-PBAT copolymer is obtained by reacting epoxy-polyether co-modified silicone softener with PBAT based on the molecular chain of PDLA, the modified SC crystalline material is formed by blending PDLA-g-PSBMA, PDLA-g-PBAT copolymer and PLLA, and the fiber is endowed with long-term consideration of high-temperature resistance, hydrophilicity, softness and easy decontamination.

[0028] In one aspect, a preparation method of modified polylactic acid fiber is provided, comprising:

[0029] Step one, providing betaine grafted right-handed polylactic acid (PDLA-g-PSBMA):

[0030] Step 101, providing multi-hydroxyl PDLA:

[0031] The multi-hydroxyl PDLA is obtained by ring-opening polymerization of right-handed lactide under the action of multi-alcohol as an initiator and stannous octoate as a catalyst under a nitrogen atmosphere at 140℃; the multi-hydroxyl PDLA is linear hydroxyl PDLA or star-shaped hydroxyl PDLA;

[0032] The linear hydroxyl PDLA or star-shaped hydroxyl PDLA is based on the structure of the initiator multi-alcohol and the morphology of lactide formed after the initiator multi-alcohol initiates ring-opening polymerization of right-handed lactide, for example, if the multi-alcohol is pentaerythritol, the four hydroxyl groups in the structure of the multi-alcohol all initiate ring-opening polymerization of cyclic lactide to form four-arm long-chain star-shaped polylactide with a hydroxyl end group, i.e., star-shaped hydroxyl PDLA, and if the multi-alcohol is 1,4-butanediol, the two end hydroxyl groups in the structure of the multi-alcohol both initiate ring-opening polymerization of cyclic lactide to form linear dihydroxyl PDLA, i.e., linear hydroxyl PDLA;

[0033] The reaction equation is as follows, wherein R(OH) x is a multi-alcohol, and x is 2, 3 or 4; the multi-alcohol is 1,4-butanediol, polyethylene glycol, trimethylolpropane, glycerol or pentaerythritol:

[0034] ;

[0035] The mass ratio of right-handed lactide, initiator and catalyst is 10:0.01-0.06:0.01-0.018;

[0036] Step 102, preparing betaine grafted right-handed polylactic acid (PDLA-g-PSBMA) by taking the multi-hydroxyl PDLA as a main raw material:

[0037] The multi-hydroxyl-terminated PDLA was vacuum dried at 50-60℃, dissolved in dichloromethane, and triethylamine was added. A dichloromethane solution of 2-bromoisobutyryl bromide was then slowly added dropwise, mixed thoroughly, and shaken in an ice-water bath at 0℃ for 3-12 hours to precipitate the product. The product was then washed, dried, and the product was obtained as the macromolecular initiator PDLA-Br. The molar ratio of the multi-hydroxyl-terminated PDLA to 2-bromoisobutyryl bromide was 1:(2-4), and the concentration of 2-bromoisobutyryl bromide in the dichloromethane solution was 2 mL / 10 mL. The multi-hydroxyl-terminated PDLA was first reacted with 2-bromoisobutyryl bromide... Butyryl bromide thermal initiator undergoes dehydrobromination reaction under 0℃ ice-water bath conditions to generate a macromolecular initiator for atom transfer radical polymerization. The amount of 2-bromoisobutyryl bromide depends on the number of hydroxyl groups in the polyhydroxyl-terminated PDLA. For example, 1 mol of polyhydroxyl-terminated PDLA initiated by butanediol contains 2 mol of hydroxyl groups, and the required amount of 2-bromoisobutyryl bromide is 2 mol. 1 mol of polyhydroxyl-terminated PDLA initiated by pentaerythritol contains 4 mol of hydroxyl groups, and the required amount of 2-bromoisobutyryl bromide is 4 mol.

[0038] Atom transfer radical polymerization (ATRP) was employed to dissolve PDLA-Br in dimethylformamide (DMF) and react it with CuBr, 2,2'-bipyridine (bpy), and methacryloylethyl sulfobetaine at 80°C for 24 hours with shaking. The precipitated product was washed, dried, and betaine-grafted dextrorotatory polylactic acid (PDLA-g-PSBMA) was obtained. The molar ratio of PDLA-Br, CuBr, 2,2'-bipyridine (bpy), and methacryloylethyl sulfobetaine (SBMA) was 1:2:4:(50~100). Based on atom transfer radical polymerization (ATRP), CuBr and 2,2'-bipyridine (bpy) formed ligands, which served as a composite catalyst to obtain betaine-grafted dextrorotatory polylactic acid.

[0039] Step 2: Provide polybutylene terephthalate-epoxy-polyether co-modified organosilicon-PDLA copolymer (PDLA-g-PBAT):

[0040] The multi-hydroxyl-terminated PDLA, polybutylene terephthalate (PBAT), and epoxy-polyether co-modified organosilicon were subjected to a Hacker blending reaction to obtain a polybutylene terephthalate-epoxy-polyether co-modified organosilicon-PDLA copolymer (PDLA-g-PBAT). The mass ratio of the multi-hydroxyl-terminated PDLA, polybutylene terephthalate-epoxy-polyether, and epoxy-polyether co-modified organosilicon was 30~50:50~70:3~5. The Hacker blending reaction was carried out at a temperature of 170~180℃. The molecular formula of the epoxy-polyether co-modified organosilicon was (CH3)3SiO[(CH3)2SiO].a [(R1)(CH3)SiO] b [(R2)(CH3)SiO] c Si(CH3)3; where a, b, and c are the number of chain segments, R1 is allyl glycidyl ether, and R2 is a polyoxyethylene segment;

[0041] This invention is based on the characteristic that the epoxy groups in epoxy-polyether co-modified organosilicon can react and copolymerize with the terminal hydroxyl groups in PDLA and the hydroxyl and carboxyl groups in PBAT. High-temperature Hacker shear blending is used to obtain poly(butylene terephthalate)-epoxy-polyether co-modified organosilicon-PDLA copolymer, realizing the compatibility polymerization of PDLA and PBAT. Compared with the fibers obtained by blending PDLA and PBAT, it has significantly improved toughness and easy stain removal.

[0042] Step 3: Provide polylactic acid fiber modified material:

[0043] The betaine-grafted dextrorotatory polylactic acid (PDLA-g-PSBMA), polybutylene terephthalate-epoxy-polyether co-modified organosilicon-PDLA copolymer (PDLA-g-PBAT), levorotatory polylactic acid (PLLA), antioxidants, and anti-hydrolysis agents are blended using a Hack blending method to obtain polylactic acid fiber modified material; the levorotatory polylactic acid (PLLA), betaine-grafted dextrorotatory polylactic acid (PDLA-g-PSBMA), polybutylene terephthalate-epoxy-polyether co-modified organosilicon-PDLA The mass ratio of the copolymer (PDLA-g-PBAT), antioxidant, and anti-hydrolysis agent is 50~60:10~30:10~30:0.1~0.3:0.2~0.3; the Hacker blending temperature is 200~240℃, preferably 220~230℃; the anti-hydrolysis agent is a monomeric carbodiimide or a polymeric carbodiimide; the antioxidant is one or more of antioxidant 1010, antioxidant 618, antioxidant 1076, antioxidant 1330, antioxidant 168, antioxidant B215, and antioxidant 225.

[0044] Based on the property that PLLA can form SC crystals with PDLA, PDLA-g-PSBMA, PDLA-g-PBAT and PLLA are blended and linked to obtain polylactic acid fiber (PLA) with high heat resistance, high mechanical properties and easy cleaning.

[0045] During their research, the inventors discovered that conventional blending of PLLA and PDLA to form PLA typically requires a processing temperature of 240-250°C to achieve SC crystallization. However, under these conditions, the raw materials are prone to thermal decomposition. This invention utilizes PDLA-g-PBAT as a raw material to effectively achieve intramolecular plasticization, resulting in PLA molecular chains with higher flexibility. PBAT has the characteristics of low melting point and softness. When combined with polyether and organosilicon segments, it further reduces the SC crystallization temperature, allowing for the acquisition of PLA fibers with tighter molecular chain connections at a lower processing temperature of 220-230°C.

[0046] Step 4: Perform melt spinning to obtain modified polylactic acid fibers:

[0047] The above-mentioned polylactic acid fiber modified material is dried to a moisture content of ≤100PPM and then melt-spun; the melt spinning temperature is 190~240℃, the winding rate is 100~200m / min, the hot stretching temperature is 100~160℃, and the stretching ratio is 1~5.

[0048] Prior to the application for this invention, a series of experiments were conducted. Some of the experimental results are listed below to provide a more detailed description of the invention. The following is a detailed description in conjunction with the embodiments. Detailed Implementation

[0049] Example 1

[0050] This embodiment provides a method for preparing modified polylactic acid fibers, including:

[0051] Step 1: Provide betaine-grafted polylactic acid (PDLA-g-PSBMA):

[0052] Step 101: Provide multi-terminal hydroxyl PDLA (HO-PDLA-OH):

[0053] 10 g of dextrorotatory lactide, 0.0626 g of 1,4-butanediol initiator, and 0.0169 g of stannous octoate were added to a single-necked flask. A three-way valve was connected, and a vacuum was applied. Nitrogen gas was circulated three times, and nitrogen was continuously introduced and maintained at 140°C for ring-opening polymerization for 5 hours. After the reaction was complete, the precipitate was dissolved in dichloromethane and precipitated by adding ice-cold methanol. The precipitate was dried in a vacuum oven at 50°C to obtain linear-chain terminal hydroxyl PDLA, labeled HO-PDLA-OH. The infrared spectrum of the linear-chain terminal hydroxyl PDLA is shown below. Figure 1 As shown; the molecular weight of the linear-chain terminal hydroxyl PDLA is 7290;

[0054] Step 102: Using the aforementioned multi-hydroxyl-terminated PDLA as the main raw material, betaine-grafted dextrorotatory polylactic acid (PDLA-g-PSBMA) was prepared.

[0055] Take 10g of the polyhydroxy-terminated PDLA (HO-PDLA-OH) into a round-bottom flask, add 30mL of dichloromethane solvent, then add 2mL of triethylamine and shake well. Slowly add 10mL of 2-bromoisobutyryl bromide dissolved in dichloromethane and shake well. The molar ratio of polyhydroxy-terminated PDLA to 2-bromoisobutyryl bromide is 1:2. Seal the round-bottom flask and place it in a constant temperature shaking ice-water bath at 0℃ for 3h. Precipitate the reaction product with ice-cold methanol and wash it twice. Then dry it in a vacuum drying oven at 60℃ for 4h. The product is labeled as PDLA-Br.

[0056] The above-mentioned PDLA-Br and magnetic rotor were added to a round-bottom flask. A three-way valve was connected, and the flask was evacuated and purged with nitrogen three times. Nitrogen purging was continued and maintained. Then, 30 mL of DMF was added to dissolve PDLA-Br. Under a nitrogen atmosphere, CuBr, 2,2'-bipyridine (bpy), and methacryloyl ethyl sulfobetaine (SBMA) were added sequentially. The flask was sealed and shaken well. The flask containing the above raw materials was placed in a water bath with constant temperature shaking and reacted at 80°C for 24 hours. The product was precipitated with ice-cold methanol and washed twice with methanol. Then, it was dried in a 50°C oven. The obtained product is dextral polylactic acid (PDLA) with methacryloyl ethyl sulfobetaine branched chain, labeled PDLA-g-PSBMA. The molar ratio of PDLA-Br, CuBr, 2,2'-bipyridine (bpy), and methacryloyl ethyl sulfobetaine (SBMA) was 1:2:4:50. The infrared spectrum of the product PDLA-g-PSBMA is shown below. Figure 2 As shown, it is a dextrorotatory polylactic acid (PDLA) with a methacryloylethyl sulfobetaine branch.

[0057] Step 2: Provide polybutylene terephthalate-epoxy-polyether co-modified organosilicon-PDLA copolymer (PDLA-g-PBAT): 50g of the aforementioned multi-hydroxyl-terminated PDLA (HO-PDLA-OH), 50g of polybutylene terephthalate (PBAT), and 3g of epoxy-polyether co-modified organosilicon were subjected to a Hacker blending reaction at a reaction temperature of 180℃, a rotation speed of 36 rpm, and a reaction time of 8 min to obtain a PDLA-epoxy-polyether co-modified organosilicon-PBAT copolymer (PDLA-g-PBAT). The PBAT was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., model number 801T. The molecular formula of the epoxy-polyether co-modified organosilicon is: (CH3)3SiO[(CH3)2SiO] a [(R1)(CH3)SiO] b [(R2)(CH3)SiO] cSi(CH3)3, where a, b, and c are the number of chain segments, R1 is allyl glycidyl ether, and R2 is a polyoxyethylene segment, was purchased from Shandong Dayi Chemical Co., Ltd., and the model is DY-ETE301 polyether epoxy co-modified silicone oil.

[0058] Step 3: Provide polylactic acid fiber modified material:

[0059] 60g of polylactic acid (PLLA), 30g of PDLA-g-PSBMA, 10g of PDLA-g-PBAT, 0.2g of antioxidant, and 0.2g of hydrolysis inhibitor were blended and modified by Hacker mixing at 230°C and 36 rpm to achieve blending of the materials, resulting in modified polylactic acid fiber material. The antioxidant was antioxidant 1010, and the hydrolysis inhibitor was polymeric carbodiimide. The polylactic acid was purchased from Total Cobian Polylactic Acid Company, brand name LX175. In this embodiment, the PLLA could also be polylactic acid of brand name L175.

[0060] Step 4: Perform melt spinning to obtain modified polylactic acid fibers:

[0061] The polylactic acid fiber modified material was dried in a vacuum oven at 80°C for 4 hours to control the moisture content to below 100 PPM, and then melt-spun at a spinning temperature of 240°C, a winding rate of 100 m / min, a hot stretching temperature of 100°C, and a stretch ratio of 2.

[0062] Example 2

[0063] This embodiment provides a method for preparing modified polylactic acid fibers, which is the same as in Example 1, except that:

[0064] In step one, in step 101, the initiator is pentaerythritol with a mass of 0.0473 g, and the mass of stannous octoate is 0.0141 g. The product obtained is polyhydroxyl-terminated PDLA with a molecular weight of 7336.

[0065] In step 102, the molar ratio of polyhydroxyl-terminated PDLA to 2-bromoisobutyryl bromide is 1:4;

[0066] In step two, the amount of multi-hydroxyl-terminated PDLA is 40g, PBAT is 60g, and epoxy-polyether co-modified organosilicon is 4g.

[0067] In step three, PDLA-g-PSBMA 10g, PDLA-g-PBAT 30g, and antioxidant 0.3g are added.

[0068] In step four, the spinning temperature is 230℃, the winding rate is 120m / min, the hot drawing temperature is 120℃, and the draw ratio is 3 times.

[0069] Example 3

[0070] This embodiment provides a method for preparing modified polylactic acid fibers, which is the same as in Example 1, except that:

[0071] In step one, in step 101, the initiator is glycerol with a mass of 0.0213 g, the mass of stannous octoate is 0.0094 g, and the molecular weight of the resulting polyhydroxyl-terminated PDLA is 14492.

[0072] In step 102, the molar ratio of polyhydroxyl-terminated PDLA to 2-bromoisobutyryl bromide is 1:3;

[0073] The shaking time in the 0℃ water bath was 12 hours.

[0074] In step two, HO-PDLA-OH is 30g and PBAT is 70g;

[0075] In step three, PLLA 50g, PDLA-g-PSBMA 25g, PDLA-g-PBAT 25g; antioxidant is antioxidant 168, hydrolysis inhibitor is monomeric carbodiimide, and the Hacker temperature is 220℃.

[0076] In step four, the spinning temperature is 220℃, the winding rate is 200m / min, the hot drawing temperature is 140℃, and the draw ratio is 3 times.

[0077] Example 4

[0078] This embodiment provides a method for preparing modified polylactic acid fibers, which is the same as in Example 1, except that:

[0079] In step one, in step 101, the initiator is polyethylene glycol 400 with a mass of 0.0556g, the mass of stannous octoate is 0.0141g, and the molecular weight of the resulting multi-terminated hydroxyl PDLA is 36400;

[0080] In step 102, the molar ratio of polyhydroxyl-terminated PDLA to 2-bromoisobutyryl bromide is 1:2;

[0081] The shaking time in the 0℃ water bath was 12 hours.

[0082] In step two, the amount of multi-hydroxyl-terminated PDLA is 40g, PBAT is 60g, and epoxy-polyether co-modified organosilicon is 5g.

[0083] In step three, PLLA 50g, PDLA-g-PSBMA 20g, PDLA-g-PBAT 30g, antioxidant 0.1g, anti-hydrolysis agent 0.3g, the anti-hydrolysis agent is monomeric carbodiimide; the Hacker temperature is 220℃;

[0084] In step four, the spinning temperature is 210℃, the winding rate is 150m / min, and the hot drawing temperature is 150℃.

[0085] Comparative Example 1

[0086] This comparative study investigated the effect of co-modification with betaine, PBAT, and epoxy-polyether co-modified organosilicon on the product properties. The preparation method was the same as in Example 1, except that in step three, 60g of polylactic acid (PLLA), 40g of PDLA, 0.2g of antioxidant, and 0.2g of anti-hydrolysis agent were blended and granulated using a Hacker mixing process to achieve the blending of the materials. The Hacker temperature was 230℃ and the rotor speed was 36rpm, resulting in polylactic acid fiber modified material. The antioxidant was antioxidant 1010, and the anti-hydrolysis agent was polymeric carbodiimide.

[0087] Comparative Example 2

[0088] This comparative study investigated the effect of betaine modification on the product properties. The preparation method was the same as in Example 1, except that step 102 was omitted and step 3 was performed by replacing PDLA-g-PSBMA with an equal amount of PDLA.

[0089] Comparative Example 3

[0090] This comparative example examines the effect of epoxy-polyether co-modification of organosilicon on product performance. The preparation method is the same as in Example 2, except that in step two, 40g of the multi-hydroxyl-terminated PDLA and 60g of PBAT are subjected to a Hacker blending reaction at a reaction temperature of 180°C for 8 minutes, and the resulting product is a blend labeled as PDLA / PBAT; in step three, an equal amount of PDLA / PBAT is used to replace PDLA-g-PBAT.

[0091] Performance Evaluation

[0092] Mechanical properties were tested for the above embodiments according to GB / T14344 "Test Method for Tensile Properties of Chemical Fiber Filaments"; stain-resistance was tested for the above embodiments according to FZ / T 01118-2012 "Detection and Evaluation of Stain Repellency of Textiles". Modified polylactic acid fibers were woven into fabrics and prepared into 300mm×300mm samples. Peanut oil was used as the stain, and a washing method was employed. The test results are shown in Table 1. Water contact angle tests were conducted on the modified polylactic acid fibers after hot pressing into films to evaluate the hydrophilicity of the material. The test method was based on GB / T30693-2014 "Measurement of Water Contact Angle of Plastic Films". The test results are shown in Table 2 and... Figure 3 .

[0093] Table 1. Properties of modified polylactic acid fibers in each example and comparative example.

[0094]

[0095] Compared to the comparative example, the modified polylactic acid (PLA) fiber of the embodiments exhibits higher stain-resistance. This demonstrates that the modified PLA fiber of the present invention maintains high tensile strength and elongation at break while possessing superior stain-resistance. Specifically, compared to Comparative Example 1, the modified PLA fiber of Example 1 shows significantly improved elongation at break and stain-resistance, indicating that the introduction of PDLA-g-PBAT and PDLA-g-PSBMA into the PLA fiber achieves synergy between PDLA-g-PBAT and PDLA-g-PSBMA, enhancing both toughness and stain-resistance. Compared to Comparative Example 2, the modified PLA fiber of Example 1 shows significantly improved stain-resistance, indicating that the introduction of PDLA-g-PSBMA effectively improves the stain-resistance of PLA fiber. Compared to Comparative Example 3, Example 2 showed improved breaking strength, elongation at break, and stain resistance. The improvement in elongation at break was particularly significant, indicating that the poly(butylene terephthalate-adipate-epoxy-polyether) copolymer (PDLA-g-PBAT) obtained by the present invention through Hacker blending reaction of poly(butylene terephthalate-adipate-epoxy-polyether) co-modified organosilicon with multi-terminated hydroxyl groups, poly(butylene terephthalate-adipate-polyether) (PBAT), and epoxy-polyether co-modified organosilicon has higher compatibility with polylactic acid (PLA), and the groups in the long fiber chain are more densely connected to the main chain.

[0096] The water contact angle test results of each embodiment and comparative example under the same conditions are shown in Table 2. It can be seen that the water contact angle of the modified polylactic acid fiber of the present invention is between 53 and 66°, which is significantly lower than that of the comparative example, indicating that the modified polylactic acid fiber of the present invention has higher hydrophilicity.

[0097] Table 2. Water contact angles of modified polylactic acid fibers in each example and comparative example.

[0098]

Claims

1. A method for producing a modified polylactic acid fiber, characterized by, include: Provides multi-hydroxyl-terminated dextrorotatory polylactic acid; Using the aforementioned multi-hydroxyl-terminated dextrorotatory polylactic acid as the main raw material, betaine-grafted dextrorotatory polylactic acid and poly(butylene terephthalate-adipate-epoxy-polyether) co-modified organosilicon-dextrorotatory polylactic acid copolymers are respectively provided. The betaine-grafted dextrorotatory polylactic acid, polybutylene terephthalate-epoxy-polyether co-modified organosilicon-dextrorotatory polylactic acid copolymer, levorotatory polylactic acid, antioxidant and anti-hydrolysis agent are blended by Hacker to obtain polylactic acid fiber modified material; The modified polylactic acid fiber material is melt-spun to obtain modified polylactic acid fiber.

2. The method of producing a modified polylactic acid fiber according to claim 1, characterized by, The melt spinning temperature is 190~240℃, the winding rate is 100~200m / min, the hot drawing temperature is 100~160℃, and the drawing ratio is 1~5.

3. The method of producing a modified polylactic acid fiber according to claim 1, characterized by, The provided polylactic acid with hydroxyl-terminated ends is a ring-opening polymerized with dextrorotatory lactide at 140°C using a polyol as an initiator and stannous octoate as a catalyst. The mass ratio of dextrorotatory lactide, initiator and catalyst is 10:0.01~0.06:0.01~0.

018.

4. The method of producing a modified polylactic acid fiber according to claim 1, characterized by, Using the aforementioned multi-hydroxyl-terminated dextrorotatory polylactic acid (PDLA) as the main raw material, the method for providing betaine-grafted PDLA comprises: vacuum drying the multi-hydroxyl-terminated PDLA, dissolving it in dichloromethane, adding triethylamine, adding dropwise a dichloromethane solution of 2-bromoisobutyryl bromide, mixing well, shaking in an ice-water bath at 0°C to precipitate the product, washing, and drying to obtain PDLA-Br; dissolving the PDLA-Br in dimethylformamide, reacting it with CuBr, 2,2'-bipyridine, and methacryloylethyl sulfobetaine at 80°C for 24 hours to precipitate the product, washing, and drying to obtain betaine-grafted PDLA.

5. The method of producing a modified polylactic acid fiber according to claim 4, characterized by, The drying temperature for vacuum drying of the multi-terminated hydroxyl-terminated dextrorotatory polylactic acid is 50~60℃; the shaking time in the 0℃ ice-water bath is 3~12h; the molar ratio of the multi-terminated hydroxyl-terminated PDLA to 2-bromoisobutyryl bromide is 1:(2~4); the concentration of 2-bromoisobutyryl bromide in the dichloromethane solution of 2-bromoisobutyryl bromide is 2mL / 10mL; and the molar ratio of PDLA-Br, CuBr, 2,2'-bipyridine and methacryloylethyl sulfobetaine is 1:2:4:(50~100).

6. The method of producing a modified polylactic acid fiber according to claim 1, characterized by, Using the aforementioned multi-hydroxyl-terminated dextrorotatory polylactic acid as the main raw material, a poly(butylene adipate)-epoxy-polyether co-modified organosilicon-dextrorotatory polylactic acid copolymer is provided, comprising: reacting the aforementioned multi-hydroxyl-terminated dextrorotatory polylactic acid, poly(butylene adipate) and epoxy-polyether co-modified organosilicon through a Hacker blending reaction to obtain the poly(butylene adipate)-epoxy-polyether co-modified organosilicon-dextrorotatory polylactic acid copolymer.

7. The method of producing a modified polylactic acid fiber according to claim 6, characterized by, The mass ratio of the multi-hydroxyl-terminated dextrorotatory polylactic acid, polybutylene terephthalate-adipate, and epoxy-polyether co-modified organosilicon is 30~50:50~70:3~5; the temperature of the Hacker blending reaction is 170~180℃.

8. The method of producing a modified polylactic acid fiber according to claim 1, characterized by, The betaine grafted poly-L-lactic acid, polybutylene adipate terephthalate-epoxy-polyether co-modified organosilicon-poly-L-lactic acid copolymer, poly-L-lactic acid, antioxidant and anti-hydrolysis agent are blended by a Haake blender to obtain a poly-lactic acid fiber modifying material, the blending temperature is 200-240 DEG C; the mass ratio of the poly-L-lactic acid, betaine grafted poly-L-lactic acid, polybutylene adipate terephthalate-epoxy-polyether co-modified organosilicon-poly-L-lactic acid copolymer, antioxidant and anti-hydrolysis agent is 50-60:10-30:10-30:0.1-0.3:0.2-0.3; the anti-hydrolysis agent is a monomeric or polymeric carbodiimide; the antioxidant is one or more of antioxidants 1010, 618, 1076, 1330, 168, B215 and 225.

9. The method of producing a modified polylactic acid fiber according to claim 8, characterized by, The blending temperature is 220-230 DEG C. 10.A modified poly-lactic acid fiber prepared by a preparation method of the modified poly-lactic acid fiber according to any one of claims 1-9.

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