A modified polylactic acid fiber, its preparation method and application

Abstract

This invention discloses a modified polylactic acid (PLA) fiber, its preparation method, and its applications. The raw materials for preparing the modified PLA fiber include the following components by weight: 70-98 parts of polylactic acid, 1-15 parts of modified tackifying resin, and 1-15 parts of tackifying resin. The modified tackifying resin is obtained by grafting tackifying resin with methacrylic acid to form a grafted tackifying resin, which is then reacted with poly(methyl methacrylate-co-glycidyl methacrylate) and lactic acid oligomers. The modified PLA fiber provided by this invention exhibits resistance to physical aging, overcoming the common problem of conventional PLA fibers easily undergoing physical aging and resulting in strength reduction. This fully meets usage requirements and greatly expands its application areas.

Description

Technical Field

[0001] This invention belongs to the field of fiber preparation technology, specifically relating to a modified polylactic acid fiber, its preparation method, and its application. Background Technology

[0002] Currently, most synthetic fibers used on a large scale are derived from petrochemical resources, such as polyolefins and polyesters. However, petroleum-based resins are themselves limited resources; moreover, their non-degradability easily causes serious "white pollution" to the environment, drastically increasing CO2 emissions and contributing to global warming. Therefore, developing biodegradable polymer fibers that can be applied in the fiber industry is particularly necessary.

[0003] Among them, polylactic acid (PLA) is a typical biodegradable plastic. PLA has good biocompatibility and biodegradability. During composting, it is decomposed by microorganisms and can eventually generate carbon dioxide and water. It is one of the earliest biodegradable plastics certified by the U.S. Food and Drug Administration (FDA). With the maturity of PLA's large-scale production technology and the reduction of its production cost, PLA fibers with various excellent properties have been prepared in recent years. Their application in the fields of medicine and textiles has attracted widespread attention. PLA fibers are made from raw materials such as corn, wheat, and starch, which are fermented to produce lactic acid and then polymerized and melt-spun. However, PLA fibers have the problem of low strength, especially below the glass transition temperature, they are prone to physical aging, which leads to a further decrease in the strength of PLA (Fiber and polymers, 2021, 22(9): 2602-2611; ACS Appl.Polm.materials, 2021, 3, 1406-1414).

[0004] Numerous public reports describe the preparation of PLA fibers. Patent CN1 17626481A discloses a method for producing high-strength-retention polylactic acid (PLA) monofilaments. This method utilizes a tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer layer to completely coat the outside of the PLA monofilament, isolating it from direct contact with air and slowing its decomposition, thereby improving the strength retention of the PLA fiber. However, this method increases the processing difficulty of PLA fibers and requires specialized equipment, hindering large-scale application. Patent CN116463785A discloses a method for preparing aging-resistant fibers. Using specifically cross-linked silicone rubber as the fiber reinforcement material and through the synergistic effect of polyvinyl alcohol, PLA fibers with a strength of 3.5-7.0 cN / dtex and a strength retention rate of 91.4-95.7% can be prepared. Due to the water-absorbing properties of polyvinyl alcohol, water molecules can enter the polylactic acid matrix during storage in certain environments, such as high humidity environments, which can cause polylactic acid to undergo hydrolysis and potentially reduce the strength of polylactic acid fibers.

[0005] Although the above-mentioned known technologies can all produce PLA fibers, they still have the following limitations: (1) Special equipment and processes are required to produce high strength retention polylactic acid fibers, which cannot be promoted on a large scale; (2) Due to their water absorption characteristics, the strength retention rate of some high strength retention polylactic acid fiber reinforced materials cannot be guaranteed under high temperature and high humidity conditions; (3) Existing strength retention rate tests only changes in a short period of time, and the strength retention rate over a long period of time cannot be guaranteed. Summary of the Invention

[0006] The main objective of this invention is to provide a modified polylactic acid fiber, its preparation method, and its application, so as to overcome the problems of severe strength attenuation and poor strength retention in the prior art.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] This invention provides a modified polylactic acid fiber. The raw materials for preparing the modified polylactic acid fiber include the following components by weight: 70-98 parts of polylactic acid, 1-15 parts of modified tackifying resin, and 1-15 parts of tackifying resin.

[0009] The modified tackifying resin is prepared by grafting a tackifying resin with methacrylic acid to form a grafted tackifying resin, and then reacting it with poly(methyl methacrylate-co-glycidyl methacrylate) and lactic acid oligomers.

[0010] This invention also provides a method for preparing the aforementioned modified polylactic acid fiber, comprising:

[0011] Modified polylactic acid fibers are prepared by blending polylactic acid, modified tackifying resin and tackifying resin, granulating, melt spinning and hot stretching.

[0012] The present invention also provides the application of the aforementioned modified polylactic acid fiber in the preparation of textile materials.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] (1) The present invention improves the stretchability of polylactic acid fiber by combining polylactic acid, modified tackifying resin and tackifying resin with specific component contents. While ensuring strength, it can also obtain modified polylactic acid fiber with high strength retention rate after 180 days of physical aging.

[0015] (2) The formulation system designed in this invention is relatively simple, but it can still achieve a high strength retention rate of polylactic acid fiber;

[0016] (3) In this invention, the low molecular weight tackifying resin will migrate to the surface of polylactic acid during the processing to form an adhesive layer, which can make the fibers stick together, improve the energy release capacity during the tensile test, and indirectly improve the strength retention rate of polylactic acid fibers.

[0017] (4) The addition of modified tackifying resin in this invention significantly enhances the compatibility between polylactic acid and tackifying resin (the surface of tackifying resin is coated with modified tackifying resin, which greatly reduces the size of the dispersed phase and makes the network structure more compact), forming a very strong bonding force; even under the process of hot stretching and tensile testing, there will be no desorption, breakage or other phenomena.

[0018] (5) The modified tackifying resin and the tackifying resin in the polylactic acid fiber of the present invention work together to form a viscoelastic three-dimensional network structure, which improves the stability of the microstructure in the fiber and significantly improves the strength retention rate of polylactic acid fiber.

[0019] (6) The present invention selects polylactic acid with a higher molecular weight, which can improve the melt strength of the blend system and improve the mechanical properties of polylactic acid fiber; the selected polylactic acid has a higher molar content of L optical isomer, which can improve the crystallization ability of the blend system, thereby improving the crystallinity and mechanical properties of modified polylactic acid fiber; the selected modified tackifying resin with a medium weight average molecular weight significantly improves the compatibility between the tackifying resin and polylactic acid, which can improve the adhesion and stretchability of the blend system, and give the modified polylactic acid fiber high mutual adhesion; so that the modified polylactic acid fiber maintains high strength after physical aging and has the characteristics of physical aging resistance, breaking through the conventional polylactic acid fiber is prone to physical aging and strength reduction, thus fully meeting the use requirements and greatly expanding its application field. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is the 1H NMR spectrum of the modified tackifying resin prepared in Example 1 of this invention;

[0022] Figure 2 These are mechanical property diagrams of the modified polylactic acid fiber prepared in Example 1 of this invention before and after aging;

[0023] Figure 3 This is a scanning electron microscope image of the residue of the modified polylactic acid fiber prepared in Example 1 of the present invention after Soxhlet extraction. Detailed Implementation

[0024] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] In this invention, unless otherwise stated, "PLA" refers to polylactic acid; "MA" refers to methacrylic acid; "MMA" refers to methyl methacrylate; and "GMA" refers to glycidyl methacrylate.

[0026] Specifically, as one aspect of the technical solution of the present invention, it relates to a modified polylactic acid fiber, wherein the raw materials for preparing the modified polylactic acid fiber include the following components calculated by weight: 70-98 parts of polylactic acid, 1-15 parts of modified tackifying resin and 1-15 parts of tackifying resin.

[0027] The modified tackifying resin is prepared by grafting a tackifying resin with methacrylic acid to form a grafted tackifying resin, and then reacting it with poly(methyl methacrylate-co-glycidyl methacrylate) and lactic acid oligomers.

[0028] Furthermore, the total weight of the raw materials used to prepare the modified polylactic acid fiber is 100 parts.

[0029] In some preferred embodiments, the poly(methyl methacrylate-co-glycidyl methacrylate) is designated as P(MMA-co-GMA).

[0030] In some preferred embodiments, the raw materials for preparing the modified polylactic acid fiber include the following components in parts by weight: 80-90 parts of polylactic acid, 5-10 parts of modified tackifying resin, and 5-10 parts of tackifying resin.

[0031] Furthermore, the raw materials for preparing the modified polylactic acid fiber include the following components calculated by weight: 80-86 parts of polylactic acid, 8-10 parts of modified tackifying resin, and 8-10 parts of tackifying resin.

[0032] In some preferred embodiments, the polylactic acid has a weight-average molecular weight of 80,000 to 500,000, and the molar content of the L-optical isomer in the polylactic acid is 85% to 99%.

[0033] Furthermore, the polylactic acid has a weight-average molecular weight of 150,000-350,000, and the molar content of the L-optical isomer in the polylactic acid is 94-98%.

[0034] In some preferred embodiments, the weight-average molecular weight of the modified tackifying resin is 20,000 to 120,000.

[0035] Furthermore, the modified tackifying resin has a weight-average molecular weight of 40,000 to 80,000.

[0036] In some preferred embodiments, the tackifying resin includes any one or more combinations of C5 tackifying resin, C5 hydrogenated tackifying resin, C9 hydrogenated tackifying resin, C9 cold-polymerized tackifying resin, C9 hot-polymerized tackifying resin, C5 / C9 copolymerized tackifying resin, terpene resin, and rosin ester, and is not limited thereto.

[0037] In some preferred embodiments, the weight-average molecular weight of the tackifying resin is 300-10000.

[0038] Furthermore, the weight-average molecular weight of the tackifying resin is 800-5000.

[0039] In some preferred embodiments, the molar grafting ratio of the grafted tackifying resin is 20-70%.

[0040] Furthermore, the molar grafting ratio of the grafted tackifying resin is 30-55%.

[0041] In some preferred embodiments, the modified polylactic acid fiber, after being treated at 40°C and 50% RH for 180 days, exhibits a strength decrease of less than 10%.

[0042] In some preferred embodiments, the modified polylactic acid fiber has a tensile strength of 3.2-5.6 cN / dtex and an elongation at break of 18%-30%.

[0043] In some preferred embodiments, the method for preparing the modified tackifying resin includes:

[0044] A first mixed reaction system containing at least a tackifying resin and methacrylic acid is subjected to a first reaction at 100-150°C for 4-12 minutes to obtain a grafted tackifying resin; wherein the grafted tackifying resin refers to a tackifying resin modified by grafting methacrylic acid, the purpose of which is to give the tackifying resin a carboxyl group that can react with P(MMA-co-GMA).

[0045] Under reaction pressure of 0.5-101 kPa and temperature of 60-80 °C, a second mixed reaction system containing methyl methacrylate, glycidyl methacrylate and solvent is subjected to a second reaction for 6-12 h to obtain poly(methyl methacrylate-co-glycidyl methacrylate).

[0046] Furthermore, the grafted tackifying resin is subjected to a third reaction with poly(methyl methacrylate-co-glycidyl methacrylate) and lactic acid oligomers at a reaction pressure of 0.5-101 kPa and a temperature of 155-195°C for 1-4 hours to obtain the modified tackifying resin.

[0047] Furthermore, the mass ratio of the tackifying resin to methacrylic acid is 80-98:2-20.

[0048] Furthermore, the mass ratio of methyl methacrylate, glycidyl methacrylate and solvent is 25-50:25-35:15-50.

[0049] Furthermore, the mass ratio of the grafted tackifying resin, poly(methyl methacrylate-co-glycidyl methacrylate) to lactic acid oligomer is 15-30:40-70:15-30.

[0050] Furthermore, the weight-average molecular weight of the lactic acid oligomer is 1000-10000.

[0051] Furthermore, the molecular weight of the poly(methyl methacrylate-co-glycidyl methacrylate) is 20,000 to 120,000.

[0052] Furthermore, the solvent includes, but is not limited to, any one or more combinations of N,N-dimethylformamide, toluene, and water.

[0053] Furthermore, the preparation method of the modified tackifying resin specifically includes: subjecting a first mixed reaction system containing a tackifying resin, methacrylic acid, and an initiator in a mass ratio of 80-98:2-20:0.1-1.2 to a first reaction at 100-150°C for 4-12 minutes to obtain a grafted tackifying resin; wherein the initiator includes, but is not limited to, dicumyl peroxide and / or benzoyl peroxide.

[0054] Further, the preparation method of the modified tackifying resin specifically includes: under the conditions of reaction pressure of 0.5-101 kPa and temperature of 60-80°C, a second mixed reaction system containing methyl methacrylate, glycidyl methacrylate, solvent and initiator in a mass ratio of 25-40:25-30:30-50:0.2-0.5 is subjected to a second reaction for 7-10 h to obtain poly(methyl methacrylate-co-glycidyl methacrylate); wherein, the initiator includes any one or more combinations of azobisisobutyronitrile, azodicyanovalerate and azobisisoheptanenitrile, and is not limited thereto.

[0055] In some preferred embodiments, the method for preparing the modified tackifying resin includes the following steps:

[0056] Step (1): React 82-96 parts by weight of tackifying resin (Cx) with 4-18 parts by weight of methacrylic acid (MA) to form grafted tackifying resin (Cx-g-MA). The reaction temperature is 110-140℃ and the reaction time is 5-10 minutes.

[0057] Step (2): Mix 25-40 parts by weight of methyl methacrylate (MMA) with 25-30 parts by weight of glycidyl methacrylate (GMA) and 30-50 parts by weight of N,N-dimethylformamide (DMF) to obtain polymethyl methacrylate-glycidyl methacrylate (P(MMA-co-GMA)). The reaction temperature is 65-75℃, the reaction pressure is 0.5-101kPa, and the reaction time is 7-10 hours.

[0058] Step (3): 15-25 parts by weight of the grafted tackifying resin (Cx-g-MA) obtained in step (1) are further blended with 50-70 parts by weight of P (MMA-co-GMA) obtained in step (2) and 15-25 parts by weight of lactic acid oligomer to obtain the modified tackifying resin. The reaction temperature is 160-190℃, the reaction pressure is 0.5-101kPa, and the reaction time is 1-3 hours.

[0059] In some more specific embodiments, the method for preparing the modified tackifying resin includes the following steps:

[0060] Step (1): 83-95 parts by weight of tackifying resin Cx, 5-17 parts by weight of methacrylic acid MA, and 0.1-1.2 parts by weight of dicumyl peroxide are melt-blended to form grafted tackifying resin Cx-g-MA. The reaction temperature is 110-135℃ and the reaction time is 6-9 minutes.

[0061] Step (2): Mix 25-30 parts by weight of methyl methacrylate (MMA), 25-30 parts by weight of glycidyl methacrylate (GMA), 40-50 parts by weight of N,N-dimethylformamide (DMF), and 0.2-0.5 parts by weight of azobisisobutyronitrile (AIBN) as initiators to carry out polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature is 68-75℃, the reaction pressure is 0.5-101kPa, and the reaction time is 7.5-10 hours.

[0062] Step (3): 18-23 parts by weight of the grafted tackifying resin Cx-g-MA obtained in step (1) are further reacted with 54-64 parts by weight of P(MMA-co-GMA) obtained in step (2) and 18-23 parts by weight of lactic acid oligomer to obtain the modified tackifying resin. The reaction temperature is 165-185℃ and the reaction time is 1.5-3.5 hours.

[0063] The modified polylactic acid fiber in this invention is in T g After sufficient storage (40°C, 50% RH), the change rate of tensile strength before and after storage is generally less than 10%; wherein, the storage time is not limited; however, generally, the time is ≥180 days.

[0064] Another aspect of the present invention provides a method for preparing the aforementioned modified polylactic acid fiber, comprising:

[0065] Modified polylactic acid fibers are prepared by blending polylactic acid, modified tackifying resin and tackifying resin, granulating, melt spinning and hot stretching.

[0066] In some preferred embodiments, the extrusion temperature for the blending granulation is 160-220°C and the screw speed is 20-70 rpm.

[0067] Furthermore, the extrusion temperature for the blending granulation is 180-200℃, and the screw speed is 30-50rpm.

[0068] In some preferred embodiments, the melt spinning is performed at a spinning temperature of 200-250°C and a spinning rate of 1000-3000 m / min.

[0069] Furthermore, the melt spinning process uses a spinning temperature of 210-230℃ and a spinning rate of 1500-2500m / min.

[0070] In some preferred embodiments, the melt spinning further includes spinning the raw materials through the spinneret holes of a melt spinning spinneret.

[0071] Furthermore, the spinneret of the melt spinning spinneret has a circular cross-section, wherein the diameter of the circular cross-section is not specifically limited and can be selected as needed.

[0072] In some preferred embodiments, the hot stretching treatment uses a stretching temperature of 75-145°C and a stretching ratio of 2.8-5.7 times.

[0073] Furthermore, the hot stretching treatment uses a stretching temperature of 90-130℃ and a stretching ratio of 3.2-4.9 times.

[0074] In some preferred embodiments, before blending and granulation, the polylactic acid, modified tackifying resin, and tackifying resin of each raw material are dried at a temperature of 90-98°C for 5-10 hours.

[0075] Another aspect of the present invention provides the application of the aforementioned modified polylactic acid fibers in textile materials.

[0076] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples:

[0077] (1) The glass transition temperature was measured by differential scanning calorimetry (DSC);

[0078] (2) Mechanical properties (including tensile strength, elongation at break, and modulus) were measured by a universal tensile testing machine (refer to national standard GB / T 14344);

[0079] (3) Polylactic acid, tackifying resin, methacrylic acid, and methyl methacrylate are all commercially available. The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented based on the technical solution of the invention, and provides detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0080] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0081] Example 1

[0082] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0083] (1) 85 parts by weight of C5 tackifying resin, 15 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide were melt-blended to form a tackifying resin with carboxylic acid groups. The reaction temperature was 120°C and the reaction time was 7 min to obtain a grafted tackifying resin with a grafting ratio of 34%.

[0084] (2) 30 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 40 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts and polymerized to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 70°C, the reaction pressure was 2 kPa, and the reaction time was 8 hours.

[0085] (3) 20 parts by weight of the grafted tackifying resin were further blended with 20 parts by weight of lactic acid oligomer and 60 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain a modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2h. The modified tackifying resin was obtained, and its NMR spectrum is shown below. Figure 1 This indicates that the preparation was successful;

[0086] (4) Take polylactic acid (PLA) with a weight average molecular weight of 200,000, and PLA with a molar content of 98% of L optical isomer; C5 tackifying resin with a weight average molecular weight of 1200; and modified tackifying resin with a weight average molecular weight of 80,000. The weight parts of each component in a blend of 100 parts by weight are: 84 parts of polylactic acid, 8 parts of tackifying resin, and 8 parts of modified tackifying resin. The blend is mechanically mixed according to this ratio, and the blended particles are dried by hot air at a temperature of 95±2℃ for 8 hours, with a moisture content of 42ppm.

[0087] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret holes. The spinning temperature was 230℃ and the spinning speed was 2000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were stretched and heat-set at a temperature of 95℃ and a stretch ratio of 3.6 times to obtain modified polylactic acid fibers. The fibers were then placed in a constant temperature and humidity chamber at 40℃ and 50% RH for 180 days for stabilization. The performance of the modified polylactic acid fibers before and after 180 days of stabilization was tested, and the test results are shown in Table 1. Figure 2 These are graphs showing the mechanical properties of the modified polylactic acid fibers before and after aging. Figure 3The image shows a scanning electron microscope (SEM) image of the insoluble residue obtained after Soxhlet extraction of modified polylactic acid (PLA) fibers using chloroform solvent. PLA is soluble in chloroform, while the modified tackifying resin is insoluble. Therefore, the microfiber structure within the SEM image is likely undissolved modified tackifying resin. This suggests that a three-dimensional network structure composed of PLA, modified tackifying resin, and tackifying resin has formed within the modified PLA fibers.

[0088] Example 2

[0089] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0090] (1) 95 parts by weight of C5 tackifying resin were melt-blended with 5 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide to form a tackifying resin with carboxylic acid groups. The reaction temperature was 120°C and the reaction time was 10 min. The molar grafting ratio of the grafted tackifying resin was 43%.

[0091] (2) 30 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 60 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 70°C, the reaction pressure was 2 kPa, and the reaction time was 8 hours.

[0092] (3) 20 parts by weight of grafted tackifying resin were further blended with 20 parts by weight of lactic acid oligomer and 60 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2h.

[0093] (4) Take polylactic acid (PLA) with a weight average molecular weight of 250,000 and a molar content of L optical isomer in PLA of 97%; C5 tackifying resin with a weight average molecular weight of 2,000; and modified tackifying resin with a weight average molecular weight of 80,000. The weight parts of each component in a blend of 100 parts by weight are: 82 parts of polylactic acid, 10 parts of tackifying resin, and 8 parts of modified tackifying resin. The blend obtained by melt extrusion of the composition is dried by hot air at a temperature of 94±2℃ for 7 hours and a moisture content of 48ppm.

[0094] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret holes. The spinning temperature was 240℃, and the spinning speed was 2000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were stretched and heat-set at a temperature of 95℃ and a stretch ratio of 3.9 times to obtain modified polylactic acid fibers. The fibers were then placed in a constant temperature and humidity chamber at 40℃ and 50% RH for 180 days for stabilization. The performance of the modified polylactic acid fibers before and after 180 days of stabilization was tested, and the test results are shown in Table 1.

[0095] Example 3

[0096] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0097] (1) 95 parts by weight of C5 tackifying resin were melt-blended with 5 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide to form a tackifying resin with carboxylic acid groups. The reaction temperature was 120°C and the reaction time was 10 min. The molar grafting ratio of the grafted tackifying resin was 43%.

[0098] (2) 25 parts by weight of methyl methacrylate (MMA), 25 parts by weight of glycidyl methacrylate (GMA), 50 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 70°C, the reaction pressure was 2 kPa, and the reaction time was 9 hours.

[0099] (3) 18 parts by weight of grafted tackifying resin were further blended with 18 parts by weight of lactic acid oligomer and 64 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2.5h.

[0100] (4) Take polylactic acid (PLA) with a weight average molecular weight of 230,000 and a molar content of L optical isomer in PLA of 96%; C5 tackifying resin with a weight average molecular weight of 1,600; and modified tackifying resin with a weight average molecular weight of 100,000, wherein the molar grafting ratio of the grafted tackifying resin is 40%; wherein, the weight parts of each component in a blend of 100 parts by weight are: 80 parts of polylactic acid, 10 parts of tackifying resin, and 10 parts of modified tackifying resin; the blend obtained by melt extrusion of the composition is hot-air dried at a drying temperature of 94±2℃ for 8 hours, and the moisture content is 50ppm.

[0101] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 235℃, and the spinning speed was 2000 m / min. The resulting blended long fibers were then wound up. Finally, the blended long fibers were subjected to stretching and heat setting at a stretching temperature of 95℃ and a stretch ratio of 4.3 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the results are shown in Table 1.

[0102] Example 4

[0103] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0104] (1) 85 parts by weight of C5 tackifying resin, 15 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide are melt-blended to form a tackifying resin with carboxylic acid groups. The reaction temperature is 110℃ and the reaction time is 6min. The molar grafting ratio of the grafted tackifying resin is 25%.

[0105] (2) 25 parts by weight of methyl methacrylate (MMA), 25 parts by weight of glycidyl methacrylate (GMA), 50 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 70°C, the reaction pressure was 2 kPa, and the reaction time was 9 hours.

[0106] (3) 18 parts by weight of grafted tackifying resin were further blended with 18 parts by weight of lactic acid oligomer and 64 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2.5h.

[0107] (4) Take polylactic acid (PLA) with a weight average molecular weight of 250,000 and a molar content of L optical isomer in PLA of 99%; C5 tackifying resin with a weight average molecular weight of 600; and modified tackifying resin with a weight average molecular weight of 100,000. The weight parts of each component in a blend of 100 parts by weight are: 75 parts of polylactic acid, 15 parts of tackifying resin, and 10 parts of modified tackifying resin. The blend obtained by melt extrusion of the composition is dried by hot air at a temperature of 94±2℃ for 7 hours and a moisture content of 40ppm.

[0108] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 210℃, and the spinning speed was 3000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were stretched and heat-set at a temperature of 95℃ and a stretch ratio of 3.5 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the results are shown in Table 1.

[0109] Example 5

[0110] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0111] (1) 96 parts by weight of C5 tackifying resin were melt-blended with 4 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide to form a tackifying resin with carboxylic acid groups. The reaction temperature was 140℃ and the reaction time was 12min. The molar grafting ratio of the grafted tackifying resin was 70%.

[0112] (2) 30 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 40 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts and polymerized to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 70°C, the reaction pressure was 2 kPa, and the reaction time was 8 hours.

[0113] (3) 25 parts by weight of grafted tackifying resin were further blended with 25 parts by weight of lactic acid oligomer and 50 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2h.

[0114] (4) Take polylactic acid (PLA) with a weight average molecular weight of 250,000 and a molar content of L optical isomer in PLA of 95%; C5 tackifying resin with a weight average molecular weight of 8,000; and modified tackifying resin with a weight average molecular weight of 60,000. The weight parts of each component in a blend of 100 parts by weight are: 85 parts of polylactic acid, 5 parts of tackifying resin, and 10 parts of modified tackifying resin. The blend obtained by melt extrusion of the composition is dried by hot air at a temperature of 94±2℃ for 10 hours, and the water content is 38ppm.

[0115] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 245℃, and the spinning speed was 3000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were subjected to stretching and heat setting at a stretching temperature of 95℃ and a stretch ratio of 3.2 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the test results are shown in Table 1.

[0116] Example 6

[0117] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0118] (1) 85 parts by weight of C5 tackifying resin, 15 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide are melt-blended to form a tackifying resin with carboxylic acid groups. The reaction temperature is 110℃ and the reaction time is 7min. The molar grafting ratio of the grafted tackifying resin is 30%.

[0119] (2) 30 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 40 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 70°C, the reaction pressure was 2 kPa, and the reaction time was 8 hours.

[0120] (3) 18 parts by weight of grafted tackifying resin were further blended with 18 parts by weight of lactic acid oligomer and 64 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2h.

[0121] (4) Take polylactic acid (PLA) with a weight average molecular weight of 80,000, and PLA with a molar content of 99% of L optical isomer; C5 tackifying resin with a weight average molecular weight of 1,000; and modified tackifying resin with a weight average molecular weight of 100,000. The weight parts of each component in a blend of 100 parts by weight are: 95 parts of polylactic acid, 2 parts of tackifying resin, and 3 parts of modified tackifying resin. The blend obtained by melt extrusion of the composition is dried by hot air at a temperature of 94±2℃ for 10 hours, and the water content is 38ppm.

[0122] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 225℃, and the spinning speed was 2000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were subjected to stretching and heat setting at a stretching temperature of 95℃ and a stretch ratio of 4.9 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the test results are shown in Table 1.

[0123] Example 7

[0124] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0125] (1) 92 parts by weight of C5 tackifying resin were melt-blended with 8 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide to form a tackifying resin with carboxylic acid groups. The reaction temperature was 130℃ and the reaction time was 10 min. The molar grafting ratio of the grafted tackifying resin was 50%.

[0126] (2) 40 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 30 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 65°C, the reaction pressure was 2 kPa, and the reaction time was 7 hours.

[0127] (3) 20 parts by weight of grafted tackifying resin were further blended with 20 parts by weight of lactic acid oligomer and 60 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2h.

[0128] (4) Take polylactic acid (PLA) with a weight average molecular weight of 80,000 and a molar content of L optical isomer in PLA of 99%; a tackifying resin with a weight average molecular weight of 4,000; and a modified tackifying resin with a weight average molecular weight of 80,000; wherein, the weight parts of each component in a blend of 100 parts by weight are: 98 parts of polylactic acid, 1 part of tackifying resin, and 1 part of modified tackifying resin; the blend obtained by melt extrusion of the composition is hot-air dried at a drying temperature of 94±2℃ for 8 hours, and the water content is 52ppm.

[0129] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 240℃, and the spinning speed was 1200 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were subjected to stretching and heat setting at a stretching temperature of 95℃ and a stretching ratio of 4.5 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the test results are shown in Table 1.

[0130] Example 8

[0131] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0132] (1) 95 parts by weight of C5 tackifying resin were melt-blended with 5 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide to form a tackifying resin with carboxylic acid groups. The reaction temperature was 120°C and the reaction time was 10 min. The molar grafting ratio of the grafted tackifying resin was 43%.

[0133] (2) 35 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 45 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 75°C, the reaction pressure was 2 kPa, and the reaction time was 8 hours.

[0134] (3) 18 parts by weight of grafted tackifying resin were further blended with 18 parts by weight of lactic acid oligomer and 64 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2h.

[0135] (4) Take polylactic acid (PLA) with a weight average molecular weight of 500,000 and a molar content of L optical isomer in PLA of 85%; C9 cold-polymerized tackifying resin with a weight average molecular weight of 2,000; and modified tackifying resin with a weight average molecular weight of 100,000. The weight parts of each component in a blend of 100 parts by weight are: 90 parts of polylactic acid, 5 parts of tackifying resin, and 5 parts of modified tackifying resin. The blend obtained by melt extrusion of the composition is dried by hot air at a temperature of 94±2℃ for 9 hours and a moisture content of 58ppm.

[0136] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 250℃, and the spinning speed was 1000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were subjected to stretching and heat setting at a stretching temperature of 95℃ and a stretch ratio of 4.2 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the test results are shown in Table 1.

[0137] Example 9

[0138] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0139] (1) 96 parts by weight of C5 tackifying resin were melt-blended with 4 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide to form a tackifying resin with carboxylic acid groups. The reaction temperature was 140℃ and the reaction time was 10 min. The molar grafting ratio of the grafted tackifying resin was 64%.

[0140] (2) 30 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 40 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 65°C, the reaction pressure was 2 kPa, and the reaction time was 12 hours.

[0141] (3) 15 parts by weight of grafted tackifying resin were further blended with 15 parts by weight of lactic acid oligomer and 70 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 2h.

[0142] (4) Take polylactic acid (PLA) with a weight average molecular weight of 500,000 and a molar content of L optical isomer in PLA of 90%; terpene resin with a weight average molecular weight of 5,000; and modified tackifying resin with a weight average molecular weight of 120,000; wherein, the weight parts of each component in a blend of 100 parts by weight are: 80 parts of polylactic acid, 10 parts of terpene resin, and 10 parts of modified tackifying resin; the blend obtained by melt extrusion of the composition is subjected to hot air drying at a drying temperature of 94±2℃ for 10 hours, and the water content is 53ppm.

[0143] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 240℃, and the spinning speed was 1000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were subjected to stretching and heat setting at a stretching temperature of 95℃ and a stretch ratio of 5.5 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the test results are shown in Table 1.

[0144] Example 10

[0145] This embodiment illustrates the preparation of modified polylactic acid fibers using the compositions and methods of the present invention.

[0146] (1) 82 parts by weight of C5 tackifying resin, 18 parts by weight of methacrylic acid (MA) and 0.8 parts by weight of dicumyl peroxide are melt-blended to form a tackifying resin with carboxylic acid groups. The reaction temperature is 110℃ and the reaction time is 5min. The molar grafting ratio of the grafted tackifying resin is 21%.

[0147] (2) 33 parts by weight of methyl methacrylate (MMA), 30 parts by weight of glycidyl methacrylate (GMA), 37 parts by weight of N,N-dimethylformamide (DMF), and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were mixed as catalysts to carry out a polymerization reaction to form poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA). The reaction temperature was 75°C, the reaction pressure was 2 kPa, and the reaction time was 10 hours.

[0148] (3) 30 parts by weight of grafted tackifying resin were further blended with 30 parts by weight of lactic acid oligomer and 40 parts by weight of poly(methyl methacrylate-co-glycidyl methacrylate) to obtain modified tackifying resin. The reaction temperature was 160℃, the reaction pressure was 2kPa, and the reaction time was 1.5h.

[0149] (4) Take polylactic acid (PLA) with a weight average molecular weight of 80,000 and a molar content of L optical isomer in PLA of 95%; C5 / C9 copolymer tackifying resin with a weight average molecular weight of 2,000; and modified tackifying resin with a weight average molecular weight of 20,000. The weight parts of each component in a blend of 100 parts by weight are: 85 parts of polylactic acid, 10 parts of tackifying resin, and 5 parts of modified tackifying resin. The blend obtained by melt extrusion of the composition is dried by hot air at a temperature of 94±2℃ for 8 hours and a moisture content of 48ppm.

[0150] (5) The dried blend was extruded and spun using a conventional melt spinning machine with circular spinneret orifices. The spinning temperature was 220℃, and the spinning speed was 3000 m / min. The blended long fibers were then wound up. Finally, the blended long fibers were stretched and heat-set at a temperature of 95℃ and a stretch ratio of 3.2 times to obtain modified bio-based polymer fibers. The properties of the modified bio-based polymer fibers were tested, and the results are shown in Table 1.

[0151] Comparative Example 1

[0152] The method of Example 2 was followed, except that "82 parts of polylactic acid" was replaced with "32 parts" and "8 parts of modified tackifying resin" was replaced with "50 parts". The test results are shown in Table 1.

[0153] Comparative Example 2

[0154] The method of Example 2 was followed, except that no modified tackifying resin was added. The test results are shown in Table 1.

[0155] Comparative Example 3

[0156] The method of Example 7 was followed, except that no modified tackifying resin or tackifying resin was added. The test results are shown in Table 1.

[0157] Comparative Example 4

[0158] The method is the same as in Example 2, except that "grafted tackifying resin" is used instead of "modified tackifying resin". The test results are shown in Table 1.

[0159] Comparative Example 5

[0160] The method is the same as in Example 2, except that "grafted tackifying resin, P(MMA-co-GMA), and lactic acid oligomer" (added directly without reacting first) replace "modified tackifying resin". The test results are shown in Table 1.

[0161] Comparative Example 6

[0162] The method was the same as in Example 2, except that the molecular weight of polylactic acid was 50,000. The test results are shown in Table 1.

[0163] Comparative Example 7

[0164] The method was the same as in Example 2, except that the spinning temperature was 280℃. The test results are shown in Table 1.

[0165] Comparative Example 8

[0166] The method was the same as in Example 2, except that the spinning rate was 5000 m / min. The test results are shown in Table 1.

[0167] Comparative Example 9

[0168] The method is the same as in Example 2, except that the drawing temperature is 150℃. The test results are shown in Table 1.

[0169] Comparative Example 10

[0170] The method is the same as in Example 2, except that the draw ratio is 7. The test results are shown in Table 1.

[0171] Table 1. Performance test results of products from Examples 1-10 and Comparative Examples 1-10

[0172]

[0173] As shown in Table 1, the modified polylactic acid fiber of the present invention has good comprehensive performance, and breaks through the performance bottleneck of conventional polylactic acid fiber which is prone to physical aging and thus reduces strength. Therefore, it fully meets the application requirements and can be applied to textile materials and other fields.

[0174] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0175] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A modified polylactic acid fiber, characterized in that, The raw materials for preparing the modified polylactic acid fiber include the following components by weight: 70-98 parts of polylactic acid, 1-15 parts of modified tackifying resin, and 1-15 parts of tackifying resin; the weight-average molecular weight of the polylactic acid is 80,000-500,000. The method for preparing the modified tackifying resin includes: A first mixed reaction system containing at least a tackifying resin and methacrylic acid is subjected to a first reaction at 100-150°C for 4-12 minutes to obtain a grafted tackifying resin; the tackifying resin includes any one or more combinations of C5 tackifying resin, C9 cold-polymerized tackifying resin, C5 / C9 copolymerized tackifying resin, and terpene resin. Under reaction pressure of 0.5-101 kPa and temperature of 60-80°C, a second mixed reaction system containing methyl methacrylate, glycidyl methacrylate and solvent is subjected to a second reaction for 6-12 h to obtain poly(methyl methacrylate-co-glycidyl methacrylate). Furthermore, the grafted tackifying resin is subjected to a third reaction with poly(methyl methacrylate-co-glycidyl methacrylate) and lactic acid oligomers at a reaction pressure of 0.5-101 kPa and a temperature of 155-195°C for 1-4 hours to obtain the modified tackifying resin. The method for preparing the modified polylactic acid fiber includes: blending polylactic acid, modified tackifying resin and tackifying resin into granules, melt spinning and hot stretching treatment to obtain modified polylactic acid fiber; wherein, the melt spinning temperature is 200-250℃ and the spinning rate is 1000-3000m / min; the hot stretching treatment uses a stretching temperature of 75-145℃ and a stretching ratio of 2.8-5.7 times.

2. The modified polylactic acid fiber according to claim 1, characterized in that, The raw materials for preparing the modified polylactic acid fiber include the following components in parts by weight: 80-90 parts of polylactic acid, 5-10 parts of modified tackifying resin and 5-10 parts of tackifying resin. The polylactic acid contains 85-99% molar content of the L-optical isomer; the modified tackifying resin has a weight-average molecular weight of 20,000-120,000. The weight-average molecular weight of the tackifying resin is 300-10000; And / or, the molar grafting ratio of the grafted tackifying resin is 20-70%.

3. The modified polylactic acid fiber according to claim 2, characterized in that, The raw materials for preparing the modified polylactic acid fiber include the following components in parts by weight: 80-86 parts of polylactic acid, 8-10 parts of modified tackifying resin and 8-10 parts of tackifying resin. The polylactic acid has a weight-average molecular weight of 150,000-350,000, and the molar content of the L-optical isomer in the polylactic acid is 94-98%. The weight-average molecular weight of the modified tackifying resin is 40,000-80,000. The weight-average molecular weight of the grafted tackifying resin is 1000-3000, and the molar grafting ratio is 30-55%.

4. The modified polylactic acid fiber according to claim 1, characterized in that: The modified polylactic acid fiber, after being treated at 40℃ and 50%RH for 180 days, showed a strength decrease of less than 10%. The modified polylactic acid fiber has a tensile strength of 3.2-5.6 cN / dtex and an elongation at break of 18%-30%.

5. The modified polylactic acid fiber according to claim 1, characterized in that: In the first mixed reaction system, the mass ratio of tackifying resin to methacrylic acid is 80-98:2-20; In the second mixed reaction system, the mass ratio of methyl methacrylate, glycidyl methacrylate and solvent is 25-50:25-35:15-50; When the third reaction is carried out, the mass ratio of the grafted tackifying resin, poly(methyl methacrylate-co-glycidyl methacrylate) to the lactic acid oligomer is 15-30:40-70:15-30. The weight-average molecular weight of the lactic acid oligomer is 1000-10000; The molecular weight of the poly(methyl methacrylate-co-glycidyl methacrylate) is 20,000 to 120,000. The solvent includes any one of N,N-dimethylformamide and toluene.

6. The modified polylactic acid fiber according to claim 1, characterized in that, The preparation method of the modified tackifying resin specifically includes: subjecting a first mixed reaction system containing a tackifying resin, methacrylic acid, and an initiator in a mass ratio of 80-98:2-20:0.1-1.2 to a first reaction at 100-150°C for 4-12 minutes to obtain a grafted tackifying resin; wherein the initiator includes dicumyl peroxide and / or benzoyl peroxide.

7. The modified polylactic acid fiber according to claim 1, characterized in that, The preparation method of the modified tackifying resin specifically includes: under the conditions of reaction pressure of 0.5-101 kPa and temperature of 60-80°C, a second mixed reaction system containing methyl methacrylate, glycidyl methacrylate, solvent and initiator in a mass ratio of 25-40:25-30:30-50:0.2-0.5 is subjected to a second reaction for 7-10 h to obtain poly(methyl methacrylate-co-glycidyl methacrylate); wherein the initiator includes any one or a combination of azobisisobutyronitrile, azodicyanovalerate and azobisisoheptanenitrile.

8. The modified polylactic acid fiber according to claim 1, characterized in that: The extrusion temperature for the blending and granulation is 160-220℃, and the screw speed is 20-70rpm.

9. The modified polylactic acid fiber according to claim 8, characterized in that: The extrusion temperature for the blending granulation is 180-200℃, and the screw speed is 30-50rpm. The melt spinning process uses a spinning temperature of 210-230℃ and a spinning rate of 1500-2500 m / min. The hot stretching treatment uses a stretching temperature of 90-130℃ and a stretching ratio of 3.2-4.9 times.

10. The use of the modified polylactic acid fiber according to any one of claims 1-9 in the preparation of textile materials.

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