Antibacterial core-sheath composite fiber and method for producing the same

Abstract

This application relates to the field of polymer material preparation technology, specifically to an antibacterial flexible core-sheath composite fiber and its preparation method. An antibacterial flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 20-40 parts PE resin, 3-7 parts toughening agent, and 1-3 parts antioxidant. The core layer raw material comprises the following components in parts by weight: 8-12 parts composite antibacterial agent and 25-30 parts PET resin. The composite antibacterial agent includes gallic acid-grafted chitosan, zirconium-based metal-organic framework, and ε-polylysine-grafted sodium alginate. The antibacterial flexible core-sheath composite fiber of this application addresses the problem that existing core-sheath composite fibers cannot simultaneously achieve excellent mechanical properties such as flexibility and antibacterial properties, thus enabling the core-sheath composite fiber to possess both flexibility and long-lasting antibacterial properties.

Description

Technical Field

[0001] This application relates to the field of polymer material preparation technology, specifically to an antibacterial flexible core-sheath composite fiber and its preparation method. Background Technology

[0002] As people's living standards improve, textiles have evolved from a single function of covering the body to a multifunctional one, placing higher demands on fiber materials in terms of antibacterial properties, flexibility, mechanical properties, and interfacial compatibility. Single-component fibers, due to their performance limitations, cannot meet diverse needs. Core-sheath composite fibers, by using two or more materials with complementary properties as the sheath and core layers respectively, can synergistically leverage the advantages of each component, becoming an important direction for solving this problem.

[0003] However, existing core-sheath composite fibers still face numerous technical bottlenecks. In terms of functionality, the synergy between antibacterial properties and flexibility is a prominent challenge: conventional antibacterial composite fibers often rely on single antibacterial agents (such as quaternary ammonium salts and nano-silver), resulting in a narrow antibacterial spectrum and performance degradation due to the migration of antibacterial components. Furthermore, the compatibility between antibacterial components and the matrix is ​​poor. While existing core-sheath composite short fibers have improved mechanical properties to some extent, the improvement is limited, and their antibacterial performance is often subpar, failing to meet the requirements of certain applications. Regarding interfacial bonding, the structural differences between the core and sheath materials lead to weak interfacial adhesion, making separation likely and affecting mechanical properties and functional transfer; it can also cause excessive erosion of the sheath, reducing fiber strength retention. Therefore, developing a core-sheath composite fiber that simultaneously possesses both flexibility and antibacterial properties is particularly urgent. Summary of the Invention

[0004] To address the issue that existing core-sheath composite fibers cannot simultaneously achieve excellent mechanical properties such as flexibility and antibacterial properties, this application provides an antibacterial and flexible core-sheath composite fiber, employing the following technical solution:

[0005] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material includes the following components in parts by weight: 20-40 parts of PE resin, 3-7 parts of toughening agent, and 1-3 parts of antioxidant. The core layer raw material includes the following components in parts by weight: 8-12 parts of composite antibacterial agent and 25-30 parts of PET resin. The composite antibacterial agent includes gallic acid-grafted chitosan, zirconium-based metal-organic framework, and ε-polylysine-grafted sodium alginate.

[0006] By adopting the above technical solution, a core-sheath structure achieves a synergistic effect between mechanical and antibacterial properties. The sheath layer uses PE resin as the matrix, combined with toughening agents and antioxidants to construct a flexible main body. PE resin itself has a low glass transition temperature and flexible molecular chains. The toughening agent can insert between PE molecular chains to reduce crystallinity and weaken intermolecular forces, making the chain segments easier to move. The antioxidant can prevent the internal structure of PE from being oxidized and damaged, thus maintaining its flexible characteristics. The combined effect of these three factors gives the sheath layer excellent softness. When the fiber is bent under stress, the flexible chain segments of the sheath layer can absorb stress through deformation, thereby reducing the overall bending stiffness of the fiber. The core layer, with PET resin as the supporting skeleton, ensures the basic strength of the fiber. The modification effect of gallic acid grafted with chitosan and ε-polylysine grafted with sodium alginate in the composite antibacterial agent of the core layer improves the thermal stability of the antibacterial agent. The combined effect of gallic acid grafted with chitosan, zirconium-based metal-organic framework, and ε-polylysine grafted with sodium alginate achieves a long-lasting antibacterial effect in the core-sheath composite fiber. Firstly, gallic acid grafted onto chitosan enhances bacterial adsorption through the cationic groups of chitosan. Furthermore, the polyphenolic oxidation of gallic acid damages the bacterial cell membrane, further enhancing the antibacterial effect. The phenolic hydroxyl groups of gallic acid bind to the sugar chains of E. coli's lipopolysaccharide via hydrogen bonds, preferentially attacking the lipid bilayer of the outer membrane and disrupting its structure. This bonded modification strengthens the synergistic antibacterial effect. Next, sodium alginate, with its strong hydrophilicity and good biocompatibility, is grafted onto ε-polylysine. Its polypeptide chains possess natural antibacterial properties and inhibit protein synthesis. Combined with gallic acid grafted onto chitosan, this achieves a synergistic effect of rapid sterilization and long-lasting antibacterial action. Furthermore, the porous structure of a zirconium-based metal-organic framework provides active sites for these two antibacterial components. The abundant interaction sites on its surface stabilize and immobilize these components, allowing the core layer to slowly release the antibacterial components, prolonging the antibacterial action time. The loading of the zirconium-based metal-organic framework also promotes the dispersion of these two antibacterial components, improving the antibacterial effect. Furthermore, the two antibacterial components in the composite antibacterial agent are modified through grafting to form amide bonds. These amide bonds impart a certain degree of flexibility to the copolymer molecular chain and greatly improve the compatibility and interfacial compatibility between the antibacterial components and PET resin, effectively optimizing the core layer's flexibility. The hydroxyl groups and other components retained in the antibacterial components, based on weak hydrogen bonds, interact with the ester groups of PET, further enhancing interfacial bonding. Therefore, the composite antibacterial components of this application enable the core-sheath composite fiber to maintain both flexibility and long-lasting antibacterial properties.

[0007] In one specific implementation, the method for preparing ε-polylysine-grafted sodium alginate includes: dissolving ε-polylysine in water and stirring, adding it to water containing sodium alginate, mixing evenly, adding EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide), stirring at 35-45℃ for 4-5 hours; dialyzing with water for 72-78 hours, and freeze-drying for 36-48 hours to obtain ε-polylysine-grafted sodium alginate.

[0008] The mass ratio of ε-polylysine to sodium alginate is 1:(1.5-1.8).

[0009] By adopting the above technical solution, the inventors discovered that combining ε-polylysine with sodium alginate through the formation of amide bonds can greatly improve the antibacterial stability and efficiency of ε-polylysine. The grafted product can enhance the adsorption of bacteria through hydrogen bonds via the hydroxyl and carboxyl groups of sodium alginate, thereby promoting the linear polypeptide linked by the ε-amide bonds of ε-polylysine, which disrupts the bacterial cell membrane, especially the negatively charged teichoic acid in the cell wall of Staphylococcus aureus, thus achieving antibacterial properties. At the same time, it can also enhance the interaction between ε-polylysine-grafted sodium alginate and other antibacterial components. Experiments showed that the ratio of ε-polylysine to sodium alginate affects the synergistic antibacterial effect of the two. A decrease in sodium alginate content reduces the adsorption performance of hydroxyl and carboxyl groups on bacteria, resulting in a decrease in the antibacterial efficiency of ε-polylysine-grafted sodium alginate. Too low a polylysine content also reduces antibacterial activity, which in turn reduces its binding affinity with other components and reduces its flexibility.

[0010] In one specific implementation, the PE resin is a polyether-modified PE resin, which is prepared by mixing polyethylene, polyethylene glycol monomethyl ether acrylate, glycidyl methacrylate and dicumyl peroxide, stirring at 1800-2000 r / min for 10-15 min, melt extruding with a twin-screw extruder, and water-cooling pelletizing to obtain the polyether-modified PE resin.

[0011] The mass ratio of gallic acid-grafted chitosan, zirconium-based metal-organic framework, and ε-polylysine-grafted sodium alginate is 1:(2-5):(0.8-1.2).

[0012] Preferably, the method for preparing the zirconium-based metal-organic framework includes: adding ZrCl4 to DMF, stirring to dissolve, adding terphenyl dicarboxylic acid, slowly adding concentrated hydrochloric acid while stirring, adjusting the pH of the system to 1-2, transferring to a reaction vessel, reacting at 120-125℃ for 36-48 h; cooling to room temperature, centrifuging and washing, then redispersing in methanol, replacing the solvent, redispersing in ethanol, adding 2-5 wt% KH550, stirring at 50-60℃ for 4-5 h, centrifuging and drying, and activating at 60℃ for 12 h to obtain the zirconium-based metal-organic framework.

[0013] By adopting the above technical solution, the inventors introduced flexible segments containing ether bonds into polyether-modified PE resin, reducing intermolecular forces, improving the flexibility of the skin layer, and thus enhancing the soft touch of the composite fiber. After melt extrusion to form fibers, the weak bonding between the ether bonds and the hydrogen bonds of hydroxyl and amino groups in the antibacterial components of the core layer is strengthened, enhancing the adhesion between the skin and the core.

[0014] Zirconium-based metal-organic frameworks (MOFs) with porous structures and large specific surface areas, constructed using long-chain ligands, not only physically adsorb bacteria, but also allow zirconium ions to chelate with phosphate groups on the bacterial cell membrane surface, disrupting cell membrane stability and inhibiting the activity of bacterial enzymes. Therefore, the adsorption capacity of the porous structure and the effect of zirconium ions endow the MOFs with broad-spectrum antibacterial properties. Modification by introducing amino groups not only enhances the adsorption and inhibition effects on bacteria and fungi, but also increases the adsorption loading of gallic acid-grafted chitosan and ε-polylysine-grafted sodium alginate. This allows the porous structure to be partially loaded with gallic acid-grafted chitosan and ε-polylysine-grafted sodium alginate. The interaction of their active functional groups improves loading stability, enabling sustained release of the antibacterial agent. This avoids the problems of narrow antibacterial spectrum and performance degradation due to migration of antibacterial components found in conventional antibacterial agents. The zirconium-based MOFs also improve biocompatibility and enhance overall mechanical properties and stability, achieving both immediate bactericidal and long-lasting antibacterial interactions, avoiding the problems of easy loss and short-term effectiveness of antibacterial agents. Therefore, a decrease in zirconium-based metal-organic framework (MOF) content leads to a reduction in antibacterial efficiency and a weakening of long-lasting antibacterial properties. However, after amino modification, the Zrconium-based MOF achieves chemical bonding with the epoxy groups in the polyether-modified PE resin during preparation, further enhancing the core-sheath bonding and thus improving mechanical properties. This promotes the migration of the other two components in the composite antibacterial agent to the core-sheath bonding site, improving the antibacterial effect. Simultaneously, the flexible long chains and amide bonds in gallic acid-grafted chitosan and ε-polylysine-grafted sodium alginate compensate for the loss of flexibility in the Zrconium-based MOF, thereby maintaining both antibacterial properties and flexibility in the prepared fiber as a whole.

[0015] The toughening agent is an ethylene-vinyl acetate copolymer.

[0016] Ethylene-vinyl acetate copolymer, used as a toughening agent, has vinyl acetate segments in its molecular structure that reduce the crystallinity of PE molecular chains, making the chains more mobile and enhancing the deformability of the skin layer. Simultaneously, the polar groups of vinyl acetate can form weak interactions with the hydroxyl and amino groups in the core layer antibacterial agent, further strengthening the skin-core interface bonding. This toughening agent works synergistically with polyether-modified PE resin; the former enhances chain segment mobility by reducing crystallinity, while the latter reduces intermolecular forces by introducing flexible segments, together giving the skin layer excellent flexibility. This allows the fibers to quickly recover when bent or folded, improving the tactile comfort of the textile.

[0017] Preferably, the antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0018] Secondly, this application provides a method for preparing antibacterial and flexible core-sheath composite fibers, using the following technical solution:

[0019] A method for preparing an antibacterial flexible core-sheath composite fiber includes the following steps: adding core material and sheath material into an extruder and melting them into a core-layer mixed melt and a sheath-layer mixed melt, respectively; then entering a composite spinning machine, and being ejected from a composite spinneret through melt distribution to form a core-sheath structure fiber; cooling, stretching, drying, and cutting to obtain the antibacterial flexible core-sheath composite fiber.

[0020] The skin layer melts at a temperature of 170-220℃ for 70-80 minutes; the core layer melts at a temperature of 200-260℃ for 55-70 minutes. More preferably, the skin layer melts at a temperature of 190-210℃ for 70-80 minutes; and the core layer melts at a temperature of 220-240℃ for 55-70 minutes.

[0021] In summary, this application has the following beneficial effects:

[0022] 1. The core-sheath structure achieves a synergistic effect of mechanical and antibacterial properties. The sheath layer uses PE resin as the matrix, combined with toughening agents and antioxidants to construct a flexible main body. The antioxidants prevent the internal structure of PE from being oxidized and damaged, thus maintaining its flexibility. When the fiber is bent under stress, the flexible segments of the sheath layer can absorb stress through deformation, thereby reducing the overall bending stiffness of the fiber. The core layer uses PET resin as a supporting skeleton. At the same time, the composite antibacterial agent in the core layer, consisting of gallic acid grafted with chitosan, zirconium-based metal-organic framework, and ε-polylysine grafted with sodium alginate, works together to achieve a long-lasting antibacterial effect in the core-sheath composite fiber. This allows the core layer to slowly release antibacterial components, prolonging the antibacterial action time. The composite antibacterial agent further optimizes the fiber's flexibility based on the bonding of the core-sheath bond and the introduction of modified groups, thus enabling the core-sheath composite fiber to maintain both flexibility and long-lasting antibacterial properties.

[0023] 2. By forming amide bonds with sodium alginate, the antibacterial stability and efficiency of ε-polylysine can be greatly improved. This allows the grafted product to enhance its adsorption to bacteria through hydrogen bonds via the hydroxyl and carboxyl groups of sodium alginate, thereby leveraging the ability of ε-polylysine to disrupt bacterial cell membranes and interfere with protein synthesis. This makes it easier for the antibacterial components to contact and exert their effects on bacteria. It also enhances the interaction between ε-polylysine grafted sodium alginate and other antibacterial components, while also improving the flexibility of the fiber. Detailed Implementation

[0024] The present application will be further described in detail below with reference to the embodiments.

[0025] Some of the raw materials used in the preparation examples and embodiments: PET resin grade: 4410G3; ε-polylysine purchased from Hubei Langbowan Biomedical LBW-567; sodium alginate purchased from Maclean S875336; terphenyl dicarboxylic acid purchased from Beijing Huawiruike Chemical Technology Co., Ltd.; PE resin grade: M2750; chitosan (degree of deacetylation 95%), product number: C105799, purchased from Aladdin; polyethylene glycol monomethyl ether acrylate mPEG-MAc purchased from Xi'an Kaixin Biotechnology, molecular weight 2k; toughening agent is ethylene-vinyl acetate copolymer, DuPont E418.

[0026] Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available products.

[0027] Preparation Example 1

[0028] Preparation of ε-polylysine-grafted sodium alginate: Dissolve 2g of ε-polylysine in 50ml of water and stir. Then add 100ml of water containing 3g of sodium alginate and stir magnetically for 30min to mix evenly. Add 0.2g of EDC and adjust the pH to 5.5. Continue stirring in a 35℃ constant temperature water bath for 5h. After the reaction is complete, dialyze with water for 72h, changing the water every 6h. After the reaction is complete, freeze dry for 48h to obtain ε-polylysine-grafted sodium alginate.

[0029] Preparation Example 2

[0030] Preparation of ε-polylysine-grafted sodium alginate: Dissolve 2g of ε-polylysine in 50ml of water and stir. Then add 100ml of water containing 2g of sodium alginate and stir magnetically for 30min to mix evenly. Add 0.2g of EDC and adjust the pH to 5.5. Continue stirring in a 35℃ constant temperature water bath for 5h. After the reaction is complete, dialyze with water for 72h, changing the water every 6h. After the reaction is complete, freeze dry for 48h to obtain ε-polylysine-grafted sodium alginate.

[0031] Preparation Example 3

[0032] Preparation of ε-polylysine-grafted sodium alginate: Dissolve 2g of ε-polylysine in 50ml of water and stir. Then add 100ml of water containing 4g of sodium alginate and stir magnetically for 30min to mix evenly. Add 0.2g of EDC and stir continuously in a 35℃ constant temperature water bath for 5h. After the reaction is complete, dialyze with water for 72h, changing the water every 6h. After the reaction is complete, freeze dry for 48h to obtain ε-polylysine-grafted sodium alginate.

[0033] Preparation Example 4

[0034] Preparation of gallic acid-grafted chitosan: Dissolve 5g of chitosan in 50ml of 1% acetic acid solution, add 5g of gallic acid and 0.15g of EDC, react at 50℃ for 4h, dialyze with water for 72h, changing the water every 6h, and freeze-dry for 48h after the reaction to obtain gallic acid-grafted chitosan.

[0035] Preparation Example 5

[0036] Preparation of PE resin: Weigh 5.0g polyethylene glycol monomethyl ether acrylate, 2.0g glycidyl methacrylate and 0.2g dicumyl peroxide, mix them and sonicate for 10min to obtain a mixture; weigh 95g PE resin and add it to the above mixture in a high-speed mixer, stir at 2000r / min for 10min to mix thoroughly; add it to a twin-screw extruder, set the extrusion temperature to: zone 1 150℃, zone 2 170℃, zone 3 180℃, zone 4 175℃, screw speed 150r / min, the material is melt-extruded in the extruder, cooled by water and pelletized to obtain polyether modified PE resin.

[0037] Preparation Example 6

[0038] Preparation of zirconium-based metal-organic frameworks: 1 g ZrCl4 was added to 20 ml DMF and stirred until dissolved. Then, 1.5 g terphenyl dicarboxylic acid was added and 37% concentrated hydrochloric acid was slowly added dropwise while stirring. The pH of the system was adjusted to 2, and then transferred to a reaction vessel. The vessel was sealed and placed in an oven. The temperature was increased at a rate of 5 °C / min and the reaction was carried out at 120 °C for 48 h. After cooling to room temperature, the vessel was centrifuged at 8000 r / min for 10 min. The vessel was washed 3 times with DMF and 2 times with methanol. The vessel was then re-dispersed in methanol and subjected to solvent replacement for 3 days, with fresh methanol added each day. After filtration, the vessel was re-dispersed in ethanol. 5 wt% KH550 was added and the vessel was stirred at 60 °C for 5 h. The vessel was then centrifuged and dried, and then activated at 60 °C for 12 h to obtain the zirconium-based metal-organic framework.

[0039] Preparation Example 7

[0040] Preparation of zirconium-based metal-organic frameworks: 1 g ZrCl4 was added to 20 ml DMF and stirred to dissolve. Then, 1.5 g terphenyl dicarboxylic acid was added and 37% concentrated hydrochloric acid was slowly added dropwise while stirring. The pH of the system was adjusted to 2, and then transferred to a reaction vessel. The vessel was sealed and placed in an oven. The temperature was increased at a rate of 5 °C / min and the reaction was carried out at 120 °C for 48 h. After cooling to room temperature, the vessel was centrifuged at 8000 r / min for 10 min. The vessel was washed 3 times with DMF and 2 times with methanol. The vessel was then dispersed in methanol and subjected to solvent replacement for 3 days, with fresh methanol added each day. After filtration, the vessel was dried at 60 °C and then activated at 60 °C for 12 h to obtain the zirconium-based metal-organic framework. Example 1

[0041] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4, zirconium-based metal-organic framework obtained in Preparation Example 6, and ε-polylysine-grafted sodium alginate obtained in Preparation Example 1, with a mass ratio of 1:2.5:0.8. The antioxidant is antioxidant 1010 and antioxidant 168 with a mass ratio of 2:1.

[0042] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained. Example 2

[0043] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4, zirconium-based metal-organic framework obtained in Preparation Example 6, and ε-polylysine-grafted sodium alginate obtained in Preparation Example 1, with a mass ratio of 1:3:0.3. The antioxidant is antioxidant 1010 and antioxidant 168 with a mass ratio of 2:1.

[0044] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained. Example 3

[0045] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4, zirconium-based metal-organic framework obtained in Preparation Example 6, and ε-polylysine-grafted sodium alginate obtained in Preparation Example 1, with a mass ratio of 0.5:2:1.8. The antioxidant is antioxidant 1010 and antioxidant 168 with a mass ratio of 2:1.

[0046] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained. Example 4

[0047] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4, zirconium-based metal-organic framework obtained in Preparation Example 6, and ε-polylysine-grafted sodium alginate obtained in Preparation Example 2, with a mass ratio of 1:2.5:0.8. The antioxidant is antioxidant 1010 and antioxidant 168 with a mass ratio of 2:1.

[0048] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained. Example 5

[0049] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4, zirconium-based metal-organic framework obtained in Preparation Example 6, and ε-polylysine-grafted sodium alginate obtained in Preparation Example 3, with a mass ratio of 1:2.5:0.8. The antioxidant is antioxidant 1010 and antioxidant 168 with a mass ratio of 2:1.

[0050] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained. Example 6

[0051] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4, zirconium-based metal-organic framework obtained in Preparation Example 7, and ε-polylysine-grafted sodium alginate obtained in Preparation Example 1, with a mass ratio of 1:2.5:0.8. The antioxidant is antioxidant 1010 and antioxidant 168 with a mass ratio of 2:1.

[0052] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained. Example 7

[0053] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material includes the following components in parts by weight: 3 kg of PE resin, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material includes the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4, zirconium-based metal-organic framework obtained in Preparation Example 6, and ε-polylysine-grafted sodium alginate obtained in Preparation Example 1, all in a mass ratio of 1:2.5:0.8. The antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0054] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0055] Comparative Example 1

[0056] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4 and zirconium-based metal-organic framework obtained in Preparation Example 6, with a mass ratio of 1:3.3. The antioxidant is antioxidant 1010 and antioxidant 168, with a mass ratio of 2:1.

[0057] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0058] Comparative Example 2

[0059] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is zirconium-based metal-organic framework obtained in Preparation Example 6 and ε-polylysine-grafted sodium alginate obtained in Preparation Example 1, with a mass ratio of 3.5:0.8. The antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0060] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0061] Comparative Example 3

[0062] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4 and ε-polylysine-grafted sodium alginate obtained in Preparation Example 1, with a mass ratio of 3.5:0.8. The antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0063] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0064] Comparative Example 4

[0065] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is gallic acid-grafted chitosan obtained in Preparation Example 4; the antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0066] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0067] Comparative Example 5

[0068] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is a zirconium-based metal-organic framework obtained in Preparation Example 6. The antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0069] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0070] Comparative Example 6

[0071] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is ε-polylysine-grafted sodium alginate obtained in Preparation Example 1; the antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0072] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0073] Comparative Example 7

[0074] An antibacterial and flexible core-sheath composite fiber includes a sheath layer and a core layer. The sheath layer raw material comprises the following components in parts by weight: 3 kg of PE resin obtained in Preparation Example 5, 0.5 kg of toughening agent, and 0.2 kg of antioxidant. The core layer raw material comprises the following components in parts by weight: 0.8 kg of composite antibacterial agent and 2.8 kg of PET resin. The composite antibacterial agent is a mixture of gallic acid and chitosan in a mass ratio of 1:2.5:0.8, a zirconium-based metal-organic framework obtained in Preparation Example 6, a mixture of sodium alginate and ε-polylysine. The antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1. The mass ratio of gallic acid to chitosan is 1:1; the mass ratio of ε-polylysine to sodium alginate is 1:1.5.

[0075] The core layer raw material and the sheath layer raw material are added to the extruder in proportion and melted into core layer mixed melt and sheath layer mixed melt respectively. The sheath layer melt temperature is 195℃ and the melting time is 75min. The core layer melt temperature is 240℃ and the melting time is 70min. Then, the melt enters the composite spinning machine and is sprayed out from the composite spinneret after melt distribution to form fibers with a core-sheath structure. After blowing and cooling, stretching, drying and cutting, antibacterial and flexible core-sheath composite fibers are obtained.

[0076] The performance testing of the antibacterial and flexible core-sheath composite fiber prepared in the examples and comparative examples was conducted using the following methods:

[0077] a. Breaking strength and elongation at break: GB / T 14344-2008 Test method for tensile properties of chemical fiber filaments; average strength was tested on the composite fibers of each example and comparative example;

[0078] b. According to the provisions of GB / T20944.3-2008 Evaluation of antibacterial properties of textiles, the antibacterial rate of fiber samples prepared in the example and comparison was tested against Escherichia coli and Staphylococcus aureus.

[0079] The comparison results are shown in Table 1 below:

[0080] Table 1 Performance Test Results

[0081] Elongation at break / % Fracture strength / CN / dtex E. coli / % Staphylococcus aureus / % Example 1 78.9 2.5 99.8 99.7 Example 2 77.5 2.6 99.7 99.5 Example 3 79.1 2.4 99.2 99.8 Example 4 75.9 2.3 99.3 99.4 Example 5 76.8 2.4 99.1 99.3 Example 6 74.7 2.2 99.5 99.6 Example 7 72.6 2.0 99.6 99.7 Comparative Example 1 69.8 3.4 98.2 98.1 Comparative Example 2 68.7 3.2 97.9 97.1 Comparative Example 3 79.8 1.8 95.0 95.2 Comparative Example 4 78.2 1.5 92.7 89.5 Comparative Example 5 56.7 2.1 87.2 86.5 Comparative Example 6 78.4 1.9 85.1 85.6 Comparative Example 7 58.2 1.6 82.4 81.6

[0082] As shown in Table 1, the antibacterial flexible core-sheath composite fiber obtained in the above embodiments has excellent flexibility and enhances the soft touch of the composite fiber. Compared with Comparative Examples 1-6 and Examples 1-3, the antibacterial flexible core-sheath composite fiber prepared in Example 1 can obtain the same breaking strength, breaking elongation and antibacterial properties. After analysis, it is believed that the combination of gallic acid grafted chitosan, zirconium-based metal-organic framework and ε-polylysine grafted sodium alginate in a certain proportion as a composite antibacterial agent can not only improve the overall bonding force of the composite fiber and improve its flexibility, but also achieve a synergistic effect of rapid sterilization and long-term antibacterial effect through their respective antibacterial modification.

[0083] Comparing Examples 1 and 4-7, and Comparative Example 7, it can be seen that the antibacterial flexible core-sheath composite fiber prepared in Example 1 exhibits superior breaking strength, elongation at break, and antibacterial properties. The proportions of ε-polylysine and sodium alginate within the scope of this application, through the formation of amide bonds, can significantly improve the antibacterial stability and efficiency of ε-polylysine, enhance system compatibility, and improve fiber flexibility. The ether bonds and epoxy groups in the polyether-modified PE resin can also form various bonds with the hydroxyl and amino groups in the core layer, strengthening the core-sheath interface bonding. The zirconium-based metal-organic framework, with its modified amino groups, not only enhances the adsorption and inhibition effects on bacteria and fungi but also strengthens the interaction between the hydroxyl groups of gallic acid-grafted chitosan and the carboxyl groups of ε-polylysine-grafted sodium alginate, as well as the bonding effect with the sheath groups, thereby improving antibacterial properties and flexibility.

[0084] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An antibacterial sheath-core composite fiber having flexibility, characterized by: The product comprises a skin layer and a core layer. The skin layer raw material includes the following components by weight: 20-40 parts PE resin, 3-7 parts toughening agent, and 1-3 parts antioxidant. The core layer raw material includes the following components by weight: 8-12 parts composite antibacterial agent and 25-30 parts PET resin. The composite antibacterial agent includes gallic acid-grafted chitosan, zirconium-based metal-organic framework, and ε-polylysine-grafted sodium alginate. The zirconium-based metal-organic framework is prepared by adding ZrCl4 to DMF, stirring and dissolving it, then adding terphenyl dicarboxylic acid, and slowly adding concentrated hydrochloric acid while stirring. After adjusting the pH of the system to 1-2, the mixture is transferred to a reaction vessel and reacted at 120-125℃ for 36-48 hours. After cooling to room temperature, the mixture is centrifuged and washed, then redispersed in methanol. After solvent replacement, it is redispersed in ethanol, and 2-5 wt% KH550 is added. The mixture is stirred at 50-60℃ for 4-5 hours, centrifuged and dried, and activated at 60℃ for 12 hours to obtain the zirconium-based metal-organic framework.

2. The antibacterial and flexible core-sheath composite fiber according to claim 1, characterized in that: The preparation method of the ε-polylysine-grafted sodium alginate includes: dissolving ε-polylysine in water and stirring, adding it to water containing sodium alginate, mixing evenly, adding EDC, stirring at 35-45℃ for 4-5 hours; dialysis with water for 72-78 hours, and freeze-drying for 36-48 hours to obtain ε-polylysine-grafted sodium alginate.

3. The antibacterial and flexible core-sheath composite fiber according to claim 2, characterized in that: The mass ratio of ε-polylysine to sodium alginate is 1:(1.5-1.8).

4. The antibacterial and flexible core-sheath composite fiber according to claim 1, characterized in that: The PE resin is a polyether-modified PE resin, and its preparation method includes mixing polyethylene, polyethylene glycol monomethyl ether acrylate, glycidyl methacrylate and dicumyl peroxide, stirring at 1800-2000 r / min for 10-15 min, melt extruding with a twin-screw extruder, and water-cooling pelletizing to obtain the polyether-modified PE resin.

5. The antibacterial and flexible core-sheath composite fiber according to claim 1, characterized in that: The mass ratio of gallic acid-grafted chitosan, zirconium-based metal-organic framework, and ε-polylysine-grafted sodium alginate is 1:(2-5):(0.8-1.2).

6. The antibacterial and flexible core-sheath composite fiber according to claim 1, characterized in that, The toughening agent is an ethylene-vinyl acetate copolymer.

7. A method for preparing an antibacterial and flexible core-sheath composite fiber according to any one of claims 1-6, characterized in that: The process includes the following steps: adding core material and sheath material into an extruder and melting them into core-layer mixed melt and sheath-layer mixed melt, respectively; then entering a composite spinning machine, where the melt is distributed and ejected from a composite spinneret to form a core-sheath structure fiber; cooling, stretching, drying, and cutting to obtain antibacterial and flexible core-sheath composite fiber.

8. The method for preparing an antibacterial and flexible core-sheath composite fiber according to claim 7, characterized in that, The skin layer melts at a temperature of 170-220℃ for 70-80 minutes; the core layer melts at a temperature of 200-260℃ for 55-70 minutes.