High-strength polylactic acid composite fiber and method for preparing the same

Abstract

The application discloses a high-strength polylactic acid composite fiber and a preparation method thereof, and relates to the technical field of polylactic acid composite material preparation. The composite fiber comprises a chinlon fiber core and a modified polylactic acid skin layer, wherein the modified polylactic acid comprises methyl methacrylate grafting and a benzene ring, and a methoxycarbonyl group is converted into a carboxyl group; the preparation method comprises the following steps: polylactic acid is stirred and dissolved in a diluent, an initiator and a stabilizer are added and reacted, methyl methacrylate and styrene and a chain transfer agent are added and reacted, a crosslinking agent and a catalyst are added and reacted, grafted polylactic acid is separated and dissolved in a solvent, tetrabutylammonium bromide and dilute hydrochloric acid solution are added and reacted, modified polylactic acid is separated, and the obtained modified polylactic acid is spun on the surface of the chinlon fiber. The application improves the adhesion and other parameters of polylactic acid and the chinlon fiber core by preparing modified polylactic acid and spinning the modified polylactic acid skin-core on the surface of the chinlon fiber under specific parameters, and finally greatly improves the overall strength of the composite fiber.

Description

Technical Field

[0001] This invention proposes a high-strength polylactic acid composite fiber and its preparation method, which relates to the field of polylactic acid composite material preparation technology. Background Technology

[0002] Polylactic acid (PLA) is an important biodegradable material composed of lactic acid molecules. It possesses excellent biocompatibility, biodegradability, and mechanical properties, thus showing broad application prospects in numerous fields. The preparation of PLA mainly relies on the fermentation and polymerization processes of lactic acid, and its raw materials are widely available, extracted from renewable resources such as corn starch.

[0003] Polylactic acid (PLA) fiber, as an important application of PLA, has received widespread attention since its introduction. This fiber possesses excellent biodegradability, environmental friendliness, biocompatibility, and physical properties, thus finding wide application in textiles, medical devices, and packaging. PLA fiber is mainly prepared through methods such as melt spinning and solution spinning, and its product forms include filaments and staple fibers.

[0004] In the textile industry, polylactic acid (PLA) fiber is highly favored due to its unique properties and environmental advantages. It can be used to make various garments and home textiles, as well as non-woven fabrics and hygiene products. Furthermore, PLA fiber possesses excellent antibacterial and UV-resistant properties, giving it irreplaceable advantages in certain specialized fields.

[0005] With continuous technological advancements, polylactic acid (PLA) composite fibers have emerged. These fibers are produced by combining PLA with other materials such as polyester and polyamide through a specific spinning process to improve their mechanical properties and functionality. PLA composite fibers not only inherit the excellent properties of PLA but also enhance their strength, abrasion resistance, and other characteristics through the composite process.

[0006] However, despite the improved performance of polylactic acid (PLA) composite fibers, certain shortcomings remain in their mechanical properties. Particularly in terms of strength, the structural characteristics of PLA itself and issues with process control during the composite process make it difficult for PLA composite fibers to achieve ideal levels in terms of tensile strength and elongation.

[0007] Core-sheath spinning, an important method for preparing polylactic acid (PLA) composite fibers, offers advantages such as simple processing and high production efficiency. However, its strength performance is less than satisfactory. This is mainly due to the uneven bonding (adhesion, etc.) of PLA with other materials during the spinning process, leading to defects and stress concentration within the fiber, thus affecting its mechanical properties.

[0008] To overcome these shortcomings, researchers are actively exploring new spinning processes and modification methods to improve the strength and other mechanical properties of polylactic acid (PLA) composite fibers. Meanwhile, with increasing environmental awareness and the expanding market for biodegradable materials, the application prospects of PLA composite fibers will be even broader.

[0009] In conclusion, polylactic acid (PLA) fiber, as a novel biodegradable material, has broad application prospects in textiles, medical devices, and packaging. Although PLA composite fibers currently have certain shortcomings in terms of mechanical properties, it is believed that these problems will gradually be solved with continuous technological advancements and innovations, laying a solid foundation for the further application and development of PLA fibers. Summary of the Invention

[0010] To address the numerous problems existing in current polylactic acid (PLA) composite fibers, particularly regarding strength, this invention proposes a technique for preparing novel PLA composite fibers using graft-modified PLA and nylon composite spinning. The specific method is as follows:

[0011] A high-strength polylactic acid composite fiber includes a nylon fiber core and a modified polylactic acid skin, wherein the modified polylactic acid includes methyl methacrylate grafts and benzene rings, and wherein the methoxy carbonyl group is converted into a carboxyl group.

[0012] Preferably, the nylon fiber has a single filament fineness of 1.0-1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0013] A method for preparing the above-mentioned high-strength polylactic acid composite fiber includes the following steps:

[0014] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0015] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0016] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0017] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0018] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0019] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0020] S7. The modified polylactic acid obtained is used as the sheath layer and nylon as the core layer through the core spinning process. After stretching and post-treatment, high-strength polylactic acid composite fiber is obtained.

[0021] Preferably, the solvent in S5 includes N,N-dimethylformamide.

[0022] Preferably, the mass ratio of the grafted polylactic acid, solvent, and tetrabutylammonium bromide in S5 is 10:(50-100):(0.1-0.5).

[0023] Preferably, the concentration of the dilute hydrochloric acid solution in S5 is 1-2 mol / L; the amount used is 10-20% of the solvent volume.

[0024] Preferably, the heating and stirring reaction described in S5 is carried out at a temperature of 60-80°C for a time of 4-8 hours.

[0025] Preferably, the diluent in S1 includes ethyl acetate.

[0026] Preferably, the initiator in S1 comprises AIBN, and the stabilizer comprises hydroquinone.

[0027] Preferably, the stirring and dissolving process described in S1 is carried out at 75-80°C.

[0028] Preferably, the chain transfer agent in S2 comprises dodecathiol.

[0029] Preferably, the reaction temperature in S2 is 75-85°C.

[0030] Preferably, the total reaction time for the reaction described in S2 is 1-3 hours.

[0031] Preferably, the crosslinking agent in S3 includes EGDMA, and the catalyst includes boron trifluoride ethyl ether.

[0032] Preferably, the concentration of polylactic acid in the diluent in S1 is 0.4-0.6 g / mL.

[0033] Preferably, the mass ratio of polylactic acid, initiator and stabilizer in S1 is (8-12):(0.05-0.12):(0.05-0.08).

[0034] Preferably, in S2, the ratio of methyl methacrylate to polylactic acid is 0.2-0.4 mL of methyl methacrylate per 1 g of polylactic acid; and the ratio of styrene to polylactic acid is 0.08-0.1 mL of styrene per 1 g of polylactic acid.

[0035] Preferably, the mass ratio of the chain transfer agent to polylactic acid in S2 is (0.001-0.002):1.

[0036] Preferably, the crosslinking agent to polylactic acid in S3 is 0.03-0.05 mL of crosslinking agent per 1 g of polylactic acid; the mass ratio of the catalyst to polylactic acid is (0.003-0.005):1.

[0037] Preferably, the separation in step S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0038] Preferably, the nylon fiber in S7 has a single filament fineness of 1.0-1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0039] Preferably, in the core-sheath spinning described in S7, 40-50 parts of the above-mentioned molten modified polylactic acid are spun onto 50-60 parts of nylon fiber, wherein the polylactic acid melting temperature is controlled at 230-240°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0040] The beneficial effects of this invention are as follows:

[0041] This invention improves parameters such as the adhesion between polylactic acid and the nylon fiber core by preparing modified polylactic acid and spinning the modified polylactic acid core-sheath onto the surface of nylon fibers with specific parameters, thereby significantly enhancing the overall strength of the composite fiber. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0044] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used in the following examples are all purchased from commercial channels.

[0045] The reagents used in the following examples are as follows: Diluent: Ethyl acetate; Initiator: AIBN; Stabilizer: Hydroquinone; Chain Transfer Agent: Dodecyl mercaptan; Crosslinking Agent: EGDMA; Catalyst: Boron trifluoride diethyl ether; Solvent: N,N-Dimethylformamide.

[0046] Example 1: Preparation method of high-strength polylactic acid composite fiber:

[0047] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0048] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0049] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0050] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0051] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0052] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0053] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0054] The heating and stirring reaction described in S5 is carried out at a temperature of 60°C for 8 hours.

[0055] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0056] The nylon fiber described in S7 has a single filament fineness of 1.0-1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0057] S7 describes a core-sheath spinning process where 40 parts of the aforementioned molten modified polylactic acid are spun onto 50 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0058] The amounts of each reagent used in the above reactions are as follows:

[0059] Polylactic acid (PLA): 10g

[0060] Methyl methacrylate (MMA): 4 mL

[0061] Styrene (St): 1 mL

[0062] Initiator (AIBN): 0.12g

[0063] Stabilizer (hydroquinone): 0.08g

[0064] Diluent (ethyl acetate): 25 mL

[0065] Chain transfer agent (dodecyl mercaptan): 0.02g

[0066] Crosslinking agent (EGDMA): 0.5 mL

[0067] Catalyst (boron trifluoride diethyl ether): 0.05g

[0068] Solvent (N,N-dimethylformamide): 100g

[0069] Tetrabutylammonium bromide: 0.5g

[0070] The concentration of the dilute hydrochloric acid solution is 1 mol / L; the amount used is 10% of the solvent volume.

[0071] Example 2: Preparation method of high-strength polylactic acid composite fiber:

[0072] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0073] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0074] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0075] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0076] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0077] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0078] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0079] The heating and stirring reaction described in S5 is carried out at a temperature of 80°C for 4 hours.

[0080] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0081] The nylon fiber described in S7 has a single filament fineness of 1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0082] S7 describes a core-sheath spinning process where 50 parts of the aforementioned molten modified polylactic acid are spun onto 60 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0083] The amounts of each reagent used in the above reactions are as follows:

[0084] Polylactic acid (PLA): 10g

[0085] Methyl methacrylate (MMA): 2 mL

[0086] Styrene (St): 0.8 mL

[0087] Initiator (AIBN): 0.05g

[0088] Stabilizer (hydroquinone): 0.05g

[0089] Diluent (ethyl acetate): 17 mL

[0090] Chain transfer agent (dodecyl mercaptan): 0.01g

[0091] Crosslinking agent (EGDMA): 0.3 mL

[0092] Catalyst (boron trifluoride diethyl ether): 0.03g

[0093] Solvent (N,N-dimethylformamide): 50g

[0094] Tetrabutylammonium bromide: 0.1g

[0095] The concentration of the dilute hydrochloric acid solution is 2 mol / L; the amount used is 20% of the solvent volume.

[0096] Example 3: Preparation method of high-strength polylactic acid composite fiber:

[0097] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0098] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0099] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0100] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0101] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0102] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0103] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0104] The heating and stirring reaction described in S5 is carried out at a temperature of 70°C for 6 hours.

[0105] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0106] The nylon fiber described in S7 has a single filament fineness of 1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0107] S7 describes a core-sheath spinning process where 40 parts of the aforementioned molten modified polylactic acid are spun onto 50 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0108] The amounts of each reagent used in the above reactions are as follows:

[0109] Polylactic acid (PLA): 10g

[0110] Methyl methacrylate (MMA): 4 mL

[0111] Styrene (St): 1 mL 0

[0112] Initiator (AIBN): 0.1g

[0113] Stabilizer (hydroquinone): 0.05g

[0114] Diluent (ethyl acetate): 20 mL

[0115] Chain transfer agent (dodecyl mercaptan): 0.02g

[0116] Crosslinking agent (EGDMA): 0.5 mL

[0117] Catalyst (boron trifluoride diethyl ether): 0.05g

[0118] Solvent (N,N-dimethylformamide): 80g

[0119] Tetrabutylammonium bromide: 0.3g

[0120] The concentration of the dilute hydrochloric acid solution is 1 mol / L; the amount used is 20% of the solvent volume.

[0121] Comparative Example 1: Preparation method of polylactic acid composite fiber (without hydrolysis reaction):

[0122] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0123] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0124] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0125] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0126] S5. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0127] The nylon fiber described in S5 has a single filament fineness of 1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0128] S5 describes core spinning, in which 40 parts of the above-mentioned molten modified polylactic acid are spun onto 50 parts of nylon fiber, wherein the polylactic acid melting temperature is controlled at 160°C, and the fiber is cooled and solidified in a side wind at room temperature and humidity of 50-60%, then placed in 100°C water for 35 minutes, and then taken out and dried.

[0129] The amounts of each reagent used in the above reactions are as follows:

[0130] Polylactic acid (PLA): 10g

[0131] Methyl methacrylate (MMA): 4 mL

[0132] Styrene (St): 1 mL 0

[0133] Initiator (AIBN): 0.1g

[0134] Stabilizer (hydroquinone): 0.05g

[0135] Diluent (ethyl acetate): 20 mL

[0136] Chain transfer agent (dodecyl mercaptan): 0.02g

[0137] Crosslinking agent (EGDMA): 0.5 mL

[0138] Catalyst (boron trifluoride diethyl ether): 0.05g

[0139] Comparative Example 2: Preparation method of high-strength polylactic acid composite fiber (without introducing benzene rings):

[0140] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0141] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and gradually add chain transfer agent to continue the reaction.

[0142] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0143] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0144] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0145] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0146] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0147] The heating and stirring reaction described in S5 is carried out at a temperature of 70°C for 6 hours.

[0148] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0149] The nylon fiber described in S7 has a single filament fineness of 1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0150] S7 describes a core-sheath spinning process where 40 parts of the aforementioned molten modified polylactic acid are spun onto 50 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0151] The amounts of each reagent used in the above reactions are as follows:

[0152] Polylactic acid (PLA): 10g

[0153] Methyl methacrylate (MMA): 4 mL

[0154] Initiator (AIBN): 0.1g

[0155] Stabilizer (hydroquinone): 0.05g

[0156] Diluent (ethyl acetate): 20 mL

[0157] Chain transfer agent (dodecyl mercaptan): 0.02g

[0158] Crosslinking agent (EGDMA): 0.5 mL

[0159] Catalyst (boron trifluoride diethyl ether): 0.05g

[0160] Solvent (N,N-dimethylformamide): 80g

[0161] Tetrabutylammonium bromide: 0.3g

[0162] The concentration of the dilute hydrochloric acid solution is 1 mol / L; the amount used is 20% of the solvent volume.

[0163] Comparative Example 3: Preparation method of high-strength polylactic acid composite fiber (without methyl methacrylate grafting):

[0164] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0165] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add styrene and gradually add chain transfer agent to continue the reaction.

[0166] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0167] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0168] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0169] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0170] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0171] The heating and stirring reaction described in S5 is carried out at a temperature of 70°C for 6 hours.

[0172] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0173] The nylon fiber described in S7 has a single filament fineness of 1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0174] S7 describes a core-sheath spinning process where 40 parts of the aforementioned molten modified polylactic acid are spun onto 50 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0175] The amounts of each reagent used in the above reactions are as follows:

[0176] Polylactic acid (PLA): 10g

[0177] Styrene (St): 1 mL 0

[0178] Initiator (AIBN): 0.1g

[0179] Stabilizer (hydroquinone): 0.05g

[0180] Diluent (ethyl acetate): 20 mL

[0181] Chain transfer agent (dodecyl mercaptan): 0.02g

[0182] Crosslinking agent (EGDMA): 0.5 mL

[0183] Catalyst (boron trifluoride diethyl ether): 0.05g

[0184] Solvent (N,N-dimethylformamide): 80g

[0185] Tetrabutylammonium bromide: 0.3g

[0186] The concentration of the dilute hydrochloric acid solution is 1 mol / L; the amount used is 20% of the solvent volume.

[0187] Comparative Example 4: Preparation method of high-strength polylactic acid composite fiber (with different nylon parameters):

[0188] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0189] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0190] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0191] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0192] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0193] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0194] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0195] The heating and stirring reaction described in S5 is carried out at a temperature of 70°C for 6 hours.

[0196] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0197] The nylon fiber described in S7 has a single filament fineness of 0.5 dtex, a breaking strength of 5-10 cN / dtex, and an elongation of 75%-100%.

[0198] S7 describes a core-sheath spinning process where 40 parts of the aforementioned molten modified polylactic acid are spun onto 50 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0199] The amounts of each reagent used in the above reactions are as follows:

[0200] Polylactic acid (PLA): 10g

[0201] Methyl methacrylate (MMA): 4 mL

[0202] Styrene (St): 1 mL 0

[0203] Initiator (AIBN): 0.1g

[0204] Stabilizer (hydroquinone): 0.05g

[0205] Diluent (ethyl acetate): 20 mL

[0206] Chain transfer agent (dodecyl mercaptan): 0.02g

[0207] Crosslinking agent (EGDMA): 0.5 mL

[0208] Catalyst (boron trifluoride diethyl ether): 0.05g

[0209] Solvent (N,N-dimethylformamide): 80g

[0210] Tetrabutylammonium bromide: 0.3g

[0211] The concentration of the dilute hydrochloric acid solution is 1 mol / L; the amount used is 20% of the solvent volume.

[0212] Comparative Example 5: Preparation method of high-strength polylactic acid composite fiber (different sheath-core spinning ratios):

[0213] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0214] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0215] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0216] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0217] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0218] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0219] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0220] The heating and stirring reaction described in S5 is carried out at a temperature of 70°C for 6 hours.

[0221] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0222] The nylon fiber described in S7 has a single filament fineness of 1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0223] S7 describes a core-sheath spinning process where 30 parts of the aforementioned molten modified polylactic acid are spun onto 50 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0224] The amounts of each reagent used in the above reactions are as follows:

[0225] Polylactic acid (PLA): 10g

[0226] Methyl methacrylate (MMA): 4 mL

[0227] Styrene (St): 1 mL 0

[0228] Initiator (AIBN): 0.1g

[0229] Stabilizer (hydroquinone): 0.05g

[0230] Diluent (ethyl acetate): 20 mL

[0231] Chain transfer agent (dodecyl mercaptan): 0.02g

[0232] Crosslinking agent (EGDMA): 0.5 mL

[0233] Catalyst (boron trifluoride diethyl ether): 0.05g

[0234] Solvent (N,N-dimethylformamide): 80g

[0235] Tetrabutylammonium bromide: 0.3g

[0236] The concentration of the dilute hydrochloric acid solution is 1 mol / L; the amount used is 20% of the solvent volume.

[0237] Comparative Example 6: Preparation method of high-strength polylactic acid composite fiber (different sheath-core spinning ratios):

[0238] S1. Dissolve polylactic acid in diluent by stirring, then add initiator and stabilizer and mix well.

[0239] S2. Maintain the reaction temperature and continue stirring. Under nitrogen protection, slowly add methyl methacrylate and styrene, and gradually add chain transfer agent to continue the reaction.

[0240] S3. After adding the crosslinking agent, add the catalyst and continue the reaction;

[0241] S4. After the reaction is complete, grafted polylactic acid is obtained by separation.

[0242] S5. The obtained grafted polylactic acid was stirred and dissolved in a solvent, tetrabutylammonium bromide was added to dissolve it, dilute hydrochloric acid solution was slowly added dropwise, and the reaction was heated and stirred.

[0243] S6. After the reaction is complete, cool and separate to obtain modified polylactic acid;

[0244] S7. The modified polylactic acid is spun onto the surface of nylon fiber by core-sheath spinning, and then post-treated to obtain high-strength polylactic acid composite fiber.

[0245] The heating and stirring reaction described in S5 is carried out at a temperature of 70°C for 6 hours.

[0246] The separation described in S6 includes: transferring the solution to a separation funnel and allowing it to stand to separate into layers; separating the lower organic phase and washing it several times with deionized water until the washing solution is neutral; and placing the organic phase in a vacuum drying oven to remove residual solvent.

[0247] The nylon fiber described in S7 has a single filament fineness of 1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%.

[0248] S7 describes a core-sheath spinning process where 60 parts of the aforementioned molten modified polylactic acid are spun onto 50 parts of nylon fiber. The polylactic acid melt temperature is controlled at 230°C, and cooling and solidification are carried out under a side airflow at room temperature and humidity of 50-60%. Finally, after drawing under hot rollers at 100°C, the roll is removed.

[0249] The amounts of each reagent used in the above reactions are as follows:

[0250] Polylactic acid (PLA): 10g

[0251] Methyl methacrylate (MMA): 4 mL

[0252] Styrene (St): 1 mL 0

[0253] Initiator (AIBN): 0.1g

[0254] Stabilizer (hydroquinone): 0.05g

[0255] Diluent (ethyl acetate): 20 mL

[0256] Chain transfer agent (dodecyl mercaptan): 0.02g

[0257] Crosslinking agent (EGDMA): 0.5 mL

[0258] Catalyst (boron trifluoride diethyl ether): 0.05g

[0259] Solvent (N,N-dimethylformamide): 80g

[0260] Tetrabutylammonium bromide: 0.3g

[0261] The concentration of the dilute hydrochloric acid solution is 1 mol / L; the amount used is 20% of the solvent volume.

[0262] The single filament fineness of the fibers obtained in the above embodiments and comparative examples is 2.0-4.0 dtex. The breaking strength and elongation of the fibers obtained in the above embodiments and comparative examples were tested, and the results are shown in Table 1.

[0263] Table 1 Sample strength test results

[0264] sample Fracture strength cN / dtex Elongation at break % Example 1 5.88 73 Example 2 5.93 77 Example 3 5.96 76 Comparative Example 1 4.14 54 Comparative Example 2 4.01 59 Comparative Example 3 4.22 52 Comparative Example 4 3.86 47 Comparative Example 5 4.12 52 Comparative Example 6 4.25 55

[0265] As can be seen from the above results, the modified polylactic acid provided by this invention can effectively improve the strength of composite fibers. However, this modified polylactic acid requires the use of nylon fibers with specific parameters to achieve the above effect. Furthermore, we found that the two groups introduced into polylactic acid, along with the hydrolyzed carboxyl group, do not contribute to fiber strength independently, but rather work synergistically, and none can be omitted. We know that in existing literature, the introduction of benzene rings and carboxyl groups into polylactic acid often affects aspects such as solubility, significantly influencing the polarity of the material, but having little impact on the mechanical parameters of the fiber. However, in this application, the synergistic effect of these groups greatly increases the strength of the composite fiber. Given that this requires the use of nylon fibers with specific parameters, we speculate that the introduction of these groups creates a complex mechanical interaction with the nylon fiber, significantly improving the adhesion between the polylactic acid fiber and the nylon fiber. This improvement is controlled within a precise range, and through core-sheath spinning, the overall strength parameters of the nylon fiber are optimized, ultimately achieving the effect of this invention.

[0266] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0267] The present invention and its embodiments have been described above. This description is not restrictive, and what is shown is only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A high-strength polylactic acid composite fiber, characterized by: The high-strength polylactic acid composite fiber comprises a polyamide fiber core and a modified polylactic acid layer, wherein the modified polylactic acid comprises methyl methacrylate grafting and a benzene ring, and a methoxycarbonyl group is converted into a carboxyl group; the polyamide fiber has a single-fiber fineness of 1.0-1.5 dtex, a breaking strength of 2-5 cN / dtex, and an elongation of 35%-48%; and the preparation method of the high-strength polylactic acid composite fiber comprises the following steps: S1, stirring and dissolving polylactic acid in a diluent, adding an initiator and a stabilizer, and mixing uniformly; S2, maintaining the reaction temperature and continuously stirring, slowly adding methyl methacrylate and styrene under nitrogen protection, gradually adding a chain transfer agent, and continuing the reaction; S3, after adding a crosslinking agent, adding a catalyst, and continuing the reaction; S4, after the reaction is completed, separating to obtain grafted polylactic acid; S5, stirring and dissolving the obtained grafted polylactic acid in a solvent, adding tetrabutylammonium bromide, slowly adding a dilute hydrochloric acid solution, and heating and stirring to react; S6, after the reaction is completed, cooling and separating to obtain modified polylactic acid; S7, through a skin-core spinning process, the obtained modified polylactic acid is used as a skin layer to be compounded with a core layer of polyamide to spin, and after drawing and post-treatment, a high-strength polylactic acid composite fiber is obtained.

2. A method for preparing the high-strength polylactic acid composite fiber according to claim 1, characterized by: The preparation method comprises the following steps: S1, stirring and dissolving polylactic acid in a diluent, adding an initiator and a stabilizer, and mixing uniformly; S2, maintaining the reaction temperature and continuously stirring, slowly adding methyl methacrylate and styrene under nitrogen protection, gradually adding a chain transfer agent, and continuing the reaction; S3, after adding a crosslinking agent, adding a catalyst, and continuing the reaction; S4, after the reaction is completed, separating to obtain grafted polylactic acid; S5, stirring and dissolving the obtained grafted polylactic acid in a solvent, adding tetrabutylammonium bromide, slowly adding a dilute hydrochloric acid solution, and heating and stirring to react; S6, after the reaction is completed, cooling and separating to obtain modified polylactic acid; S7, through a skin-core spinning process, the obtained modified polylactic acid is used as a skin layer to be compounded with a core layer of polyamide to spin, and after drawing and post-treatment, a high-strength polylactic acid composite fiber is obtained.

3. The method for preparing high-strength polylactic acid composite fiber according to claim 2, characterized in that: The solvent in S5 comprises N,N-dimethylformamide; the mass ratio of the grafted polylactic acid, the solvent and tetrabutylammonium bromide in S5 is 10:(50-100):(0.1-0.5); the concentration of the dilute hydrochloric acid solution in S5 is 1-2 mol / L; the amount of the dilute hydrochloric acid solution is 10%-20% of the volume of the solvent; the heating and stirring reaction in S5 is carried out at a temperature of 60-80 °C for 4-8 h.

4. The method for preparing high-strength polylactic acid composite fiber according to claim 2, characterized in that: The diluent in S1 comprises ethyl acetate; the initiator in S1 comprises AIBN, and the stabilizer comprises hydroquinone; the stirring and dissolving in S1 is carried out at 75-80 °C.

5. The method for preparing high-strength polylactic acid composite fiber according to claim 2, characterized in that: The chain transfer agent in S2 comprises dodecanethiol; the reaction temperature in S2 is 75-85 °C; and the total reaction time in S2 is 1-3 h.

6. The method for preparing high-strength polylactic acid composite fiber according to claim 2, characterized in that: The crosslinking agent in S3 comprises EGDMA, and the catalyst comprises boron trifluoride etherate; the amount ratio of the crosslinking agent to polylactic acid in S3 is 0.03-0.05 mL of the crosslinking agent per 1 g of polylactic acid; and the amount mass ratio of the catalyst to polylactic acid is (0.003-0.005):

1.

7. The method for preparing high-strength polylactic acid composite fiber according to claim 2, characterized in that: The concentration of the polylactic acid in the diluent is 0.4-0.6 g / mL; the mass ratio of the polylactic acid, the initiator and the stabilizer is (8-12):(0.05-0.12):(0.05-0.08).

8. The method for preparing high-strength polylactic acid composite fiber according to claim 2, characterized in that: The use amount ratio of the methyl methacrylate to the polylactic acid is that 0.2-0.4 mL of methyl methacrylate is added to 1 g of polylactic acid; the use amount ratio of the styrene to the polylactic acid is that 0.08-0.1 mL of styrene is added to 1 g of polylactic acid; the use amount mass ratio of the chain transfer agent to the polylactic acid is (0.001-0.002):

1.

9. The method for preparing high-strength polylactic acid composite fiber according to claim 2, characterized in that: The nylon fiber has a single-fiber fineness of 1.0-1.5 dtex, a breaking strength of 2-5 cN / dtex and an elongation of 35%-48%.