Ultrafine denier es fiber and method of making same

Abstract

The application relates to the field of spinning fibers, and particularly discloses a superfine denier ES fiber and a preparation method thereof. The superfine denier ES fiber has a skin-core structure and comprises a skin layer material and a core layer material. The skin layer material comprises the following raw materials in parts by weight: 20-40 parts of PE resin, 2-3 parts of tannic acid modified aluminum nitride, 1-4 parts of a toughening agent, 0.5-1 part of an antioxidant, 0.2-0.6 parts of a dispersing agent and 0.1-0.5 parts of an antistatic agent. The core layer material comprises the following raw materials in parts by weight: 30-65 parts of PET resin, 1.5-2 parts of maleic anhydride grafted polyethylene, 5-15 parts of an ethylene-butyl acrylate-glycidyl methacrylate terpolymer and 1-2 parts of a nucleating agent. The ES fiber has the advantages of good mechanical properties and antibacterial properties, strong moisture absorption and excellent anti-reverse osmosis effect.

Description

Technical Field

[0001] This application relates to the field of spinning fiber technology, and more specifically, to an ultrafine denier ES fiber and a method for preparing the same. Background Technology

[0002] With the advancement of the textile industry and the increasing demands of consumers for comfort in textiles, the high performance and functionalization of fiber materials have become important directions for industry development. Among these, the finer denier and ultrafine denier of fibers are effective ways and key technologies to upgrade fiber materials and enhance the quality of textiles. Ultrafine denier fibers (also known as microfibers or extra-fine fibers) have a lower monofilament linear density, resulting in fabrics and nonwovens that exhibit excellent softness, fluffiness, drape, and a delicate touch. They are widely used in high-end clothing, high-performance wiping materials, filter materials, and hygiene products.

[0003] Currently, there is no unified national standard for the definition of fine denier and microfiber. According to relevant regulations of the my country Textile Industry Chemical Fiber Industry Corporation, the linear density of microfiber monofilament is generally defined as 0.5-1.3 dtex. ES fiber is a composite fiber with a core-sheath structure, typically composed of two polymer materials. A typical structure uses low-melting-point polyethylene (PE) as the sheath and high-melting-point polyethylene terephthalate (PET) as the core. This structure gives ES fiber unique thermal bonding properties. Through heat treatment, the PE sheath melts and bonds, while the PET core retains its fiber shape, thus forming a nonwoven fabric that is both fluffy and soft, and possesses high strength.

[0004] Currently, the linear density of commonly used ES fiber monofilaments is typically in the range of 2-6 dtex. However, nonwoven fabrics made from this conventional fiber specification have room for improvement in achieving ultimate softness, high bulkiness, and a textile-like hand feel. By treating ES fibers to achieve an ultra-fine denier, reducing their monofilament linear density to below 1.3 dtex, the overall performance of the final product can be significantly improved, meeting the demands of more advanced applications.

[0005] However, the preparation of ultrafine denier ES fiber faces significant technical challenges. Since ES fiber is composed of two polymer materials, PE and PET, which have significantly different thermodynamic properties, the glass transition temperature, crystallization rate and orientation behavior of PE and PET differ significantly during the production process of ultrafine denier fiber. As a result, the deformation capacity of the two under tensile stress is different, which can easily lead to a decrease in the bonding force between the skin and core layers, resulting in skin-core separation, uneven stretching and even fiber breakage. This seriously affects the stability of production and the yield of finished fibers. Summary of the Invention

[0006] In order to improve the compatibility of PE and PET and enable them to be stably bonded during the spinning and forming process of ultrafine denier ES fiber, this application provides an ultrafine denier ES fiber and its preparation method.

[0007] In the first aspect, this application provides an ultrafine denier ES fiber, employing the following technical solution:

[0008] An ultrafine denier ES fiber has a core-sheath structure, comprising a sheath material and a core material. The sheath material comprises the following raw materials in parts by weight: 20-40 parts PE resin, 2-3 parts tannic acid-modified aluminum nitride, 1-4 parts toughening agent, 0.5-1 part antioxidant, 0.2-0.6 parts dispersant, and 0.1-0.5 parts antistatic agent.

[0009] The core material comprises the following raw materials in parts by weight: 30-65 parts PET resin, 1.5-2 parts maleic anhydride grafted polyethylene, 5-15 parts ethylene-butyl acrylate-glycidyl methacrylate terpolymer, and 1-2 parts nucleating agent.

[0010] By adopting the above technical solution, ethylene-butyl acrylate-glycidyl methacrylate terpolymer (PTW), maleic anhydride, and nucleating agent are used in the core layer. The active epoxy groups of glycidyl methacrylate contained in the PTW molecular chain react chemically with the terminal carboxyl and terminal hydroxyl groups of PET. During melt extrusion, graft copolymers can be formed at the interface of the blend, which reduces the interfacial tension between the PET and PE phases, improves the interfacial compatibility, and thus increases the interfacial thickness and interfacial adhesion between the two phases, thereby achieving toughening and reinforcement of ES fibers.

[0011] Maleic anhydride-grafted polyethylene (MPPE) contains highly polar maleic anhydride, which can chemically react with the hydroxyl or carboxyl groups at the ends of the PET molecular chains to generate copolymers containing both PET and PE segments. This copolymer preferentially accumulates at the interface between the sheath and the core, tightly connecting PET and PE. Meanwhile, the polyethylene segments in MPPE exhibit excellent compatibility with the non-polar PE sheath, allowing them to undergo physical entanglement or co-crystallization. Through both chemical and physical processes, MPPE significantly reduces the interfacial tension between the PET and PE phases, preventing sheath-core separation during the stretching of ultrafine denier fibers.

[0012] During the spinning process of ultrafine denier fibers, nucleating agents provide seed crystals for the crystal growth of PET macromolecules, increasing the crystallization rate and crystallinity of PET. The accelerated crystallization speed enables the fibers to form a stable crystalline structure more quickly, reducing internal stress caused by the difference in thermal shrinkage between the sheath and core layers, and resulting in better dimensional stability of the fibers.

[0013] Tannic acid in the skin layer modifies aluminum nitride. Tannic acid is deposited on the surface of aluminum nitride, and its phenolic hydroxyl groups form stable complexes or hydrogen bonds with the oxide layer on the aluminum nitride surface. Furthermore, these exposed hydroxyl groups and benzene ring structures endow the ions with unique amphiphilicity. The hydroxyl groups on the tannic acid can form strong hydrogen bonds with the carboxyl or ester groups at the ends of the PET molecular chains, thus anchoring the aluminum nitride particles at the PET / PE interface. Moreover, the aromatic rings and hydrophobic framework in the tannic acid molecule structure have certain van der Waals forces with the PET molecular chains in the skin layer. When the tannic acid-modified aluminum nitride is located near the skin-core interface, due to the wetting effect of the PE melt on the particle surface, the particles tend to cross the interface, forming physical pins and preventing interface slippage. In addition, the hydroxyl groups in the tannic acid can form strong chemical bonds with the active epoxy groups of glycidyl methacrylate in the ethylene-butyl acrylate-glycidyl methacrylate terpolymer in the core layer, thus further enhancing the interfacial tightness between the skin and core layers.

[0014] In addition, tannic acid-modified aluminum nitride, as a highly thermally conductive inorganic particle, plays a heterogeneous nucleation role in the PE skin layer, increasing the crystallization temperature and crystallinity of PE, compensating for the strength loss caused by ultrafine denier, enhancing the thermal stability of the fiber, reducing the difference in thermal shrinkage rate between the PE skin layer and the PET core layer, reducing internal stress, and preventing fiber curling or uneven shrinkage from affecting the dimensional stability of the fiber. Moreover, the phenolic hydroxyl groups in the tannic acid-modified aluminum nitride form a continuous hydration layer on the fiber surface, giving the fiber surface excellent hydrophilicity, thereby adsorbing and transferring water molecules. The highly thermally conductive aluminum nitride can form a thermally conductive pathway in the fiber, accelerating the evaporation and diffusion of water molecules, improving thermal and moisture comfort. Furthermore, under the chemical bonding of the tannic acid-modified aluminum nitride with the copolymer, it is not easy to fall off, the interfacial thermal resistance is reduced, and the improved moisture permeability is more durable.

[0015] Preferably, the mass ratio of tannic acid-modified aluminum nitride in the outer layer to ethylene-butyl acrylate-glycidyl methacrylate terpolymer in the core layer is 1:4-5.

[0016] By adopting the above technical solution, tannic acid contains a large number of pyrogallol / catechol groups. Its phenolic hydroxyl groups can undergo ring-opening reactions with the epoxy groups in glycidyl methacrylate to form stable ether bonds and secondary hydroxyl groups, thereby playing a bridging role at the interface between the skin and the core. When the two are used in an appropriate ratio, they not only increase the compatibility of the skin but also do not affect the softness.

[0017] Preferably, the method for preparing the tannic acid-modified aluminum nitride is as follows: tannic acid is added to a Tris buffer solution, zinc chloride and polyethyleneimine are added, and the mixture is stirred evenly to obtain a treatment solution;

[0018] Aluminum nitride is soaked in the treatment solution for 10-12 hours, filtered, washed with deionized water, and dried. The amount of tannic acid used in the tannic acid-modified aluminum nitride is 3-6% of the mass of aluminum nitride.

[0019] By adopting the above technical solution, tannic acid self-polymerization can form a coating on the surface of aluminum nitride. Moreover, under alkaline and aerobic conditions, it is oxidized to generate quinones, and the self-polymerization of quinones realizes the tannic acid coating. In addition, catechol groups can provide lone electrons to combine with metal ions to form a coating. After tannic acid is oxidized to generate quinones, it can undergo Michael addition or Schiff base reaction with the amino groups in PEI. PEI can also undergo coordination reaction with metal ions to form a stable three-dimensional cross-linked network. This increases the surface roughness of aluminum nitride, improves the stability of the tannic acid coating, enhances moisture permeability and durability, and avoids the decrease in transparency after multiple washes. It can also introduce a large number of hydroxyl groups, which can form hydrogen bonds with the carboxyl or ester groups at the end of PET molecules, or form strong chemical bonds with the active epoxy groups of glycidyl methacrylate contained in the ethylene-butyl acrylate-glycidyl methacrylate terpolymer. This improves the interfacial adhesion strength between aluminum nitride and PET or PE, and improves the structural stability of the skin and core layers. At the same time, PEI can increase the moisture permeability of the fiber, and zinc ions synergistically enhance the antibacterial effect with tannic acid.

[0020] The optimal ratio of tannic acid to aluminum nitride ensures the formation of a tannic acid coating on the aluminum nitride surface, preventing ion aggregation and providing sufficient phenolic hydroxyl groups to facilitate subsequent reactions with epoxy groups, thereby significantly improving interfacial adhesion and imparting thermal conductivity, antistatic properties, and antibacterial properties to the fiber.

[0021] Preferably, the core layer contains 1-3 parts by weight of moisture-barrier filler.

[0022] By adopting the above technical solution, a certain amount of moisture-barrier filler is added to the core layer, and ES fibers with a hydrophilic skin layer and a hydrophobic core layer are obtained without affecting the hot melt spinning. The hydrophilic skin layer can quickly capture liquid and conduct it to the core layer through hydrophilic channels. The hydrophobic core layer forms a barrier layer to prevent liquid from seeping back to the skin layer from the inside. Therefore, the moisture permeability decreases in a gradient from the skin layer to the core layer, which has the advantages of unidirectional moisture conduction and good thermal and moisture comfort. It is suitable for disposable hygiene products, medical protective materials and functional textiles with high requirements for dryness and hygiene.

[0023] Preferably, the moisture-barrier filler is tributylhexylphosphine bromide intercalated montmorillonite supported on silver oxide.

[0024] By adopting the above technical solution, tributylhexylphosphine bromide is embedded in the interlayer of montmorillonite. While expanding the layers, its hydrophobic long chains cover the inner and outer surfaces of montmorillonite. When water molecules enter the core layer through the skin layer, tributylhexylphosphine bromide can block the penetration of water molecules. The silver oxide loaded in the tributylhexylphosphine bromide intercalated montmorillonite not only has moisture barrier properties but also antibacterial properties. The silver oxide loaded in it has a broad-spectrum antibacterial effect, and the layered structure of montmorillonite can achieve the slow release of silver ions, thereby improving the antibacterial durability. Tributylhexylphosphine bromide is a quaternary phosphonium salt with good thermal stability. Its cations can adsorb negatively charged bacterial cell membranes, and the long alkyl chains insert into the membrane, causing leakage of contents and achieving antibacterial effect. The synergistic effect of the dual cations of quaternary phosphonium salt and silver ions broadens the antibacterial spectrum and strengthens the antibacterial effect. The intercalation of quaternary phosphonium salt expands the interlayer spacing of montmorillonite, providing space for silver oxide loading and preventing silver oxide particle aggregation. Moreover, montmorillonite itself has an adsorption effect on bacteria, increasing the probability of contact between bacteria and silver ions and improving antibacterial ability.

[0025] In addition, montmorillonite is a layered silicate that achieves farmer-scale dispersion in the PET matrix, improving the mechanical strength of ES fibers. Silver oxide acts as a nano-reinforcing agent, working synergistically with montmorillonite to form a dual reinforcing network. Therefore, it not only endows the fibers with long-lasting antibacterial and anti-reverse osmosis functions, but also improves the mechanical strength of the fibers and enhances their heat deformation capacity.

[0026] Preferably, the mass ratio of montmorillonite, tributylhexylphosphine bromide, and nanosilver in the tributylhexylphosphine-intercalated montmorillonite-loaded nanosilver is 1:0.5-0.6:0.1-0.15.

[0027] By adopting the above technical solution, the above-mentioned amount of tributylhexylphosphine bromide can be effectively inserted into the interlayer of montmorillonite, changing it from hydrophilic to hydrophobic, and preventing it from being excessive and free in the PET matrix, migrating and decomposing during high-temperature spinning to produce odors or bubbles, and affecting the core-sheath interface or fiber mechanical properties; the above-mentioned amount of silver oxide can ensure that the fiber has high antibacterial properties, and prevent the aggregation of silver oxide nanoparticles on the surface of montmorillonite or in the PET matrix. Excessive use of silver oxide will cause the particles to become larger, clogging the spinneret and affecting the continuity of spinning, and the color is too dark, which will affect the appearance of the fiber.

[0028] Preferably, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076;

[0029] The dispersant is succinimide;

[0030] The antistatic agent is a mixture of glyceryl trilaurate and ethoxylated alkyl acid;

[0031] The toughening agent is an acrylonitrile-butadiene-styrene copolymer.

[0032] Preferably, the nucleating agent is selected from at least one of hydrotalcite, montmorillonite, nano-magnesium oxide, and nano-silica.

[0033] Secondly, this application provides a method for preparing ultrafine denier ES fibers, employing the following technical solution:

[0034] A method for preparing ultrafine denier ES fiber involves mixing PE resin with tannic acid-modified aluminum nitride, toughening agent, antioxidant, dispersant and antistatic agent, and stirring at 63-67℃ for 40-50 min to obtain the skin material;

[0035] The core material is prepared by mixing PET resin with maleic anhydride-grafted polyethylene, ethylene-butyl acrylate-glycidyl methacrylate terpolymer and nucleating agent, and stirring at 80-90℃ for 40-50 min.

[0036] The sheath material and the core material are melted separately to obtain sheath melt and core melt, which are then processed by composite spinning, cooling, stretching, heat treatment and cutting to obtain ultrafine denier ES fiber.

[0037] In summary, this application has the following beneficial effects:

[0038] 1. Because this application uses tannic acid to modify aluminum nitride in the skin layer and adds ethylene-butyl acrylate-glycidyl methacrylate tripolymer, maleic anhydride-grafted polyethylene and nucleating agent in the core layer, the phenolic hydroxyl groups in tannic acid react with the epoxy groups in glycidyl methacrylate in the ethylene-butyl acrylate-glycidyl methacrylate tripolymer to form a chemically connected phase at the interface between the skin layer and the core layer, effectively solving the problem of skin-core separation during the ultra-fine denier process. Moreover, the introduction of tannic acid and aluminum nitride can endow ultra-fine denier ES fibers with multiple functions such as rapid heat dissipation, antistatic and antibacterial properties, giving them a broader application prospect in the fields of hygiene, medical and high-performance wiping materials.

[0039] 2. In this application, it is preferred to use a combination of polyethyleneimine and tannic acid to modify aluminum nitride, which improves the stability of the tannic acid coating, enhances the antibacterial and hydrophilic properties of ES fibers, and further improves the adhesion between the core and the skin.

[0040] 3. In this application, it is preferred to introduce montmorillonite modified by intercalation of tributylhexylphosphine bromide and loaded with silver oxide into the core layer to achieve synergistic optimization of antibacterial properties and unidirectional moisture wicking. The quaternary phosphonium salt cation intercalation expands the interlayer spacing of montmorillonite and endows it with hydrophobic properties, so that the modified montmorillonite forms a composite structure in the core layer with enhanced antibacterial properties and moisture barrier. The loaded silver oxide is dispersed and slowly released between the montmorillonite layers. Combined with the quaternary phosphonium salt, it achieves a dual cationic antibacterial effect, making ES fiber suitable for disposable hygiene products, medical protective materials and functional textiles with high requirements for dryness and hygiene. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the embodiments.

[0042] Preparation Examples of Tannic Acid Modified Aluminum Nitride 1-4

[0043] Preparation Example 1: (1) Add 8g of tannic acid to a Tris buffer solution with pH=8.5 to prepare a solution with a concentration of 8mg / ml. Add zinc chloride and polyethyleneimine until the concentrations of zinc chloride and polyethyleneimine are both 1g / l. Mix well to obtain a treatment solution with a molecular weight of 600 for polyethyleneimine.

[0044] (2) Soak aluminum nitride in the treatment solution for 12 hours, filter, wash with deionized water, and dry in an oven at 60°C. The amount of tannic acid used is 6% of the mass of aluminum nitride.

[0045] Preparation Example 2: (1) Add 8g of tannic acid to a Tris buffer solution with pH=8.5 to prepare a solution with a concentration of 8mg / ml. Add zinc chloride and polyethyleneimine until the concentrations of zinc chloride and polyethyleneimine are both 1g / l. Mix well to obtain a treatment solution with a molecular weight of 600 for polyethyleneimine.

[0046] (2) Soak aluminum nitride in the treatment solution for 10 hours, filter, wash with deionized water, and dry in an oven at 60°C. The amount of tannic acid used is 3% of the mass of aluminum nitride.

[0047] Preparation Example 3: The difference from Preparation Example 1 is that polyethyleneimine was not added.

[0048] Preparation Example 4: The difference from Preparation Example 1 is that the amount of tannic acid used is 1% of the mass of aluminum nitride.

[0049] Preparation Examples 5-6 of Tributylhexylphosphine bromide Intercalated Montmorillonite Supported Silver Oxide

[0050] Preparation Example 5: (1) 10g of sodium montmorillonite was dispersed in a mixture of ethanol / water (volume ratio of 9:1) with a solid content of 10% to obtain a suspension;

[0051] (2) Add 6g of n-tributylhexadecanylphosphine bromide to the suspension, stir at 60°C for 6h, filter, wash with ethanol and water until no bromide ions are present, and dry under vacuum at 60°C to obtain intercalated modified montmorillonite.

[0052] (3) Disperse 1.5g of silver oxide into 30g of water, sonicate for 30min, add intercalated modified montmorillonite, sonicate for 30min, and vacuum dry at 60℃.

[0053] Preparation Example 6: (1) 10g of sodium montmorillonite was dispersed in a mixture of ethanol / water (volume ratio of 9:1) with a solid content of 8% to obtain a suspension;

[0054] (2) Add 5g of n-tributylhexadecanylphosphine bromide to the suspension, stir at 60°C for 6h, filter, wash with ethanol and water until no bromide ions are present, and dry under vacuum at 60°C to obtain intercalated modified montmorillonite.

[0055] (3) Disperse 1g of silver oxide into 30g of water, sonicate for 30min, add intercalated modified montmorillonite, sonicate for 30min, and vacuum dry at 60℃.

[0056] Example

[0057] In the following examples, the sources of each raw material are as follows: PE resin is selected from Formosa Plastics 1040F; acrylonitrile-butadiene-styrene copolymer is selected from Chi Mei ABS, model PA-765; PET resin is selected from Far Eastern Plastics, model CB-602; maleic anhydride grafted polyethylene is selected from Dongguan Shenghao Plastics, model PE-12L; ethylene-butyl acrylate-glycidyl methacrylate terpolymer is selected from DuPont, model PTW-1.

[0058] Example 1: An ultrafine denier ES fiber with a core-sheath structure is produced by spinning a mixture of sheath material and core material. The raw material amounts of the sheath material and core material are shown in Table 1. It is prepared by tannic acid-modified aluminum nitride in Example 1. The toughening agent is acrylonitrile-butadiene-styrene copolymer, the antioxidant is antioxidant 1010, the dispersant is succinimide, and the antistatic agent is a mixture of glycerol trilaurate and ethoxylated alkyl acid in a mass ratio of 1:1. The nucleating agent in the core material is nano-magnesium oxide.

[0059] The preparation method of the above-mentioned ultrafine denier ES fiber includes the following steps:

[0060] PE resin was mixed with tannic acid-modified aluminum nitride, toughening agent, antioxidant, dispersant and antistatic agent, and stirred at 65°C for 45 min to obtain the skin material;

[0061] The core material was prepared by mixing PET resin with maleic anhydride-grafted polyethylene, ethylene-butyl acrylate-glycidyl methacrylate terpolymer and nucleating agent, and stirring at 85°C for 45 min.

[0062] The sheath material is hot-melted in an extruder at temperatures of 265℃, 275℃, 285℃, 285℃, and 280℃ in different zones to obtain a sheath melt. The core material is also hot-melted in an extruder at temperatures of 195℃, 210℃, 220℃, 220℃, and 215℃ in different zones to obtain a core melt. The sheath melt and core melt are then combined and spun at 285℃ in a 3:2 mass ratio. After cooling, drawing, heat treatment, and cutting, ultrafine denier ES fibers are obtained. Cooling is achieved using gradient air blowing, with the temperature of the first gradient cooling air... The temperature is 25℃, the wind speed is 0.8m / s, the cooling air temperature of the second gradient is 16℃, the wind speed is 0.5m / s, and a multi-stage stretching process is used for stretching. The first stretching mechanism is set between the first and second gradient air blowers, and the four-wire stretching ratio is 2.5 times. The second stretching process is set after the second gradient air blower, with a stretching groove temperature of 55℃, a II stretching machine temperature of 60℃, a II stretching machine temperature of 65℃, a wire stretching ratio of 5 times, a heat treatment temperature of 140℃, a treatment time of 30 minutes, and then combing and cutting.

[0063] Table 1. Raw material usage of ultrafine denier ES fibers in Examples 1-4

[0064] Example 2: An ultrafine denier ES fiber with a core-sheath structure, made by spinning a mixture of sheath material and core material. The raw material amounts of the sheath material and core material are shown in Table 1. It was prepared by tannic acid-modified aluminum nitride in Example 2. The toughening agent is acrylonitrile-butadiene-styrene copolymer, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a 1:1 ratio, the dispersant is succinimide, and the antistatic agent is a mixture of glycerol trilaurate and ethoxylated alkyl acid in a mass ratio of 1:0.5. The nucleating agent in the core material is nano-silica.

[0065] The preparation method of the above-mentioned ultrafine denier ES fiber includes the following steps:

[0066] PE resin was mixed with tannic acid-modified aluminum nitride, toughening agent, antioxidant, dispersant and antistatic agent, and stirred at 67°C for 40 min to obtain the skin material;

[0067] The core material was prepared by mixing PET resin with maleic anhydride-grafted polyethylene, ethylene-butyl acrylate-glycidyl methacrylate terpolymer and nucleating agent, and stirring at 90°C for 40 min.

[0068] The sheath material is hot-melted in an extruder at temperatures of 270℃, 280℃, 285℃, 285℃, and 280℃ in different zones to obtain a sheath melt. The core material is also hot-melted in an extruder at temperatures of 195℃, 210℃, 220℃, 220℃, and 215℃ in different zones to obtain a core melt. The sheath melt and core melt are then combined and spun at 285℃ in a 3:2 mass ratio. After cooling, drawing, heat treatment, and cutting, ultrafine denier ES fibers are obtained. Cooling is achieved using gradient air blowing, with the temperature of the first gradient cooling air... The temperature is 25℃, the wind speed is 0.8m / s, the cooling air temperature of the second gradient is 16℃, the wind speed is 0.5m / s, and a multi-stage stretching process is used for stretching. The first stretching mechanism is set between the first and second gradient air blowers, and the four-wire stretching ratio is 2.5 times. The second stretching process is set after the second gradient air blower, with a stretching groove temperature of 55℃, a II stretching machine temperature of 60℃, a II stretching machine temperature of 65℃, a wire stretching ratio of 5 times, a heat treatment temperature of 140℃, a treatment time of 30 minutes, and then combing and cutting.

[0069] Examples 3-4: An ultrafine denier ES fiber, which differs from Example 1 in that the raw material amounts of the core layer and the sheath layer are shown in Table 1.

[0070] Example 5: An ultrafine denier ES fiber, which differs from Example 1 in that the tannic acid-modified aluminum nitride was prepared as in Example 3.

[0071] Example 6: An ultrafine denier ES fiber, which differs from Example 1 in that the tannic acid-modified aluminum nitride was prepared as in Example 4.

[0072] Example 7: An ultrafine denier ES fiber, differing from Example 1 in that 3g of moisture-barrier filler is added to the core layer material. The moisture-barrier filler is calcium chloride. The core layer material is prepared as follows: PET resin is mixed with maleic anhydride-grafted polyethylene, ethylene-butyl acrylate-glycidyl methacrylate terpolymer, calcium chloride and nucleating agent, and stirred at 85°C for 45 minutes to obtain the core layer material; the remaining methods are the same as in Example 1.

[0073] Example 8: An ultrafine denier ES fiber, which differs from Example 7 in that the core layer material also contains 3g of moisture-barrier filler, which is tributylhexylphosphine bromide intercalated montmorillonite supported silver oxide, and is prepared by the method in Preparation Example 5.

[0074] Example 9: An ultrafine denier ES fiber, which differs from Example 7 in that the core layer material also contains 3g of moisture-barrier filler, which is tributylhexylphosphine bromide intercalated montmorillonite supported silver oxide, and is prepared by the method in Preparation Example 6.

[0075] Example 10: An ultrafine denier ES fiber, which differs from Example 8 in that the moisture-proof filler is tributylhexylphosphine bromide intercalated montmorillonite. The preparation method of tributylhexylphosphine bromide intercalated montmorillonite is as follows: (1) 10g of sodium montmorillonite is dispersed in a mixture of ethanol / water (volume ratio of 9:1) with a solid content of 10% to obtain a suspension.

[0076] (2) Add 6g of tributylhexylphosphine bromide to the suspension, stir at 60°C for 6h, filter, wash with ethanol and water until no bromide ions are present, and dry under vacuum at 60°C.

[0077] Example 11: An ultrafine denier ES fiber, which differs from Example 8 in that the moisture-barrier filler is montmorillonite-supported silver oxide. The specific preparation method is as follows: 1.5g of silver oxide is dispersed in 30g of water, sonicated for 30min, 10g of sodium montmorillonite is added, sonicated for 30min, and vacuum dried at 60℃.

[0078] Comparative Example

[0079] Comparative Example 1: An ultrafine denier ES fiber, which differs from Example 1 in that the tannic acid-modified aluminum nitride is not added to the hull material.

[0080] Comparative Example 2: An ultrafine denier ES fiber, which differs from Example 1 in that an equal amount of aluminum nitride is used to replace tannic acid in modifying the aluminum nitride.

[0081] Comparative Example 3: An ultrafine denier ES fiber, which differs from Example 1 in that the core material does not contain ethylene-butyl acrylate-glycidyl methacrylate terpolymer.

[0082] Performance testing

[0083] Ultrafine denier ES fibers were prepared according to the methods in the examples and comparative examples, and the fiber performance was tested according to the following methods. The test results are recorded in Table 2.

[0084] 1. Tensile properties: The breaking strength and elongation at break were tested according to GB / T14337-2008 using a universal tensile testing machine at room temperature. The tensile speed was 50 mm / min. Each sample was measured 5 times and the average value was taken.

[0085] 2. Shrinkage rate: Referring to the provisions of GB / T10003, take a sample of a certain size, place it in the middle of a 120℃ oven, blow air, heat for 120s, and then place it to cool at room temperature. Measure its length in the longitudinal direction and calculate the heat shrinkage rate.

[0086] 3. Antibacterial rate: Escherichia coli was selected as the representative of Gram-negative bacteria, and Staphylococcus aureus was selected as the representative of Gram-positive bacteria. According to the provisions of GB / T20944.3-2088 Evaluation of antibacterial properties of textiles, the antibacterial rate of ES fiber samples against Escherichia coli and Staphylococcus aureus was tested and expressed as a percentage.

[0087] 4. Water diffusion time: Refer to GB / T21655.1-2023 "Determination of moisture absorption and quick-drying properties of textiles - Part 1: Single-item combination test method". Place the same mass of ES fibers on a horizontal clamp, add 0.05 mL of distilled water with a micropipette, and record the time for complete diffusion of the water droplets. Test 5 groups of samples for each group, and test each group of samples 3 times. Take the average value.

[0088] 5. Reverse seepage amount: The test is conducted in accordance with GB / T24218.14-2020 "Textiles - Nonwovens - Test Methods - Part 14: Determination of the amount of moisture reabsorption of covering materials". The same mass of ES fiber is placed in deionized water to absorb water for 1 hour, and placed at 25℃ and 70% (relative humidity). A filter paper is placed on its surface and the mass is recorded as m1. It is pressed under a pressure of 1 kPa for 6 hours. After 6 hours, the mass of the filter paper is weighed as m2. The reverse seepage amount is calculated as m2-m1. The smaller the reverse seepage amount, the better the dryness under the use condition.

[0089] Table 2 Performance test results of ultrafine denier ES fibers

[0090] Based on the test data in Table 2 and the raw material dosages in Examples 1-4, it can be seen that the prepared ES fiber has strong breaking strength and elongation at break, low heat shrinkage, strong antibacterial properties, and fast surface wetting speed with water. This indicates that the tannic acid-modified aluminum nitride prepared by tannic acid, polyethyleneimine and zinc chloride, combined with ethylene-butyl acrylate-glycidyl methacrylate terpolymer, can effectively improve the interfacial adhesion between the core layer and the sheath of the ES fiber and enhance the mechanical strength of the fiber.

[0091] Compared with Example 1, Example 5 uses aluminum nitride modified with tannic acid prepared in Example 3, without the addition of polyethyleneimine. As a result, the surface water diffusion time of the ES fiber prepared by this method is prolonged, the hydrophilicity of the cortex is reduced, the antibacterial ability is slightly reduced, and the breaking strength and elongation at break are reduced. This indicates that the modification of aluminum nitride with polyethyleneimine in conjunction with tannic acid can improve the mechanical strength of ES fiber, enhance antibacterial properties, and improve the hydrophilicity of the cortex.

[0092] In Example 6, tannic acid-modified aluminum nitride prepared in Preparation Example 4 was used. Compared with Example 1, the ES fiber prepared in Example 6 had reduced antibacterial ability, weakened hydrophilicity of the cortex, and reduced mechanical strength.

[0093] Compared with Example 1, Example 7 also added calcium chloride, a moisture-barrier filler, to the core layer material. As a result, the reverse osmosis of the ES fiber was reduced, and it had a better ability to keep dry.

[0094] Compared with Example 7, the moisture-barrier fillers in Examples 8 and 9 are tributylhexylphosphine bromide intercalated montmorillonite loaded with silver oxide prepared in Preparation Example 5 and Preparation Example 6, respectively. As shown in Table 2, compared with Example 7, the ES fibers prepared in Examples 8 and 9 have increased breaking strength, improved antibacterial rate, and enhanced anti-reverse osmosis ability.

[0095] In Example 10, the moisture-barrier filler was tributylhexylphosphine bromide intercalated montmorillonite, without silver oxide loading on the montmorillonite. Compared with Example 8, the antibacterial ability of the ES fiber decreased and the breaking strength was slightly reduced, indicating that the loading of silver oxide can not only improve the antibacterial properties of the fiber, but also enhance its mechanical strength.

[0096] In Example 11, the moisture-barrier filler was montmorillonite loaded with silver oxide. No intercalation treatment of montmorillonite was used. Compared with Example 8, the breaking strength of ES fibers decreased and the anti-reverse osmosis ability decreased. This indicates that the intercalation treatment of montmorillonite with tributylhexylphosphide can improve the hydrophobicity of montmorillonite, enhance the mechanical strength of fibers, improve the anti-reverse osmosis ability of fibers, and maintain dryness during use.

[0097] Compared with Example 1, Comparative Example 1 did not add tannic acid to modify aluminum nitride. The data in Table 2 shows that the breaking strength of ES fiber decreased, the antibacterial rate decreased significantly, and the water diffusion time increased. This indicates that tannic acid modification of aluminum nitride can improve the hydrophilicity, heat resistance and antibacterial ability of the fiber.

[0098] Compared with Example 1, Comparative Example 2, without tannic acid modification, showed little change in the thermal shrinkage rate of ES fibers, but the antibacterial rate and mechanical strength decreased, indicating that tannic acid modification can improve the antibacterial properties, hydrophilicity and mechanical strength of fibers.

[0099] Compared with Example 1, Comparative Example 3 did not contain the ethylene-butyl acrylate-glycidyl methacrylate terpolymer. The data in Table 2 show that the breaking strength and elongation at break of the ES fiber prepared in Comparative Example 3 decreased, while the other properties remained largely unchanged.

[0100] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An ultrafine denier ES fiber, characterized in that, It has a core-skin structure, including a skin layer and a core layer. The skin layer comprises the following raw materials in parts by weight: 20-40 parts of PE resin, 2-3 parts of tannic acid-modified aluminum nitride, 1-4 parts of toughening agent, 0.5-1 part of antioxidant, 0.2-0.6 parts of dispersant, and 0.1-0.5 parts of antistatic agent. The core material comprises the following raw materials in parts by weight: 30-65 parts PET resin, 1.5-2 parts maleic anhydride grafted polyethylene, 5-15 parts ethylene-butyl acrylate-glycidyl methacrylate terpolymer, and 1-2 parts nucleating agent.

2. The ultrafine denier ES fiber according to claim 1, characterized in that: The mass ratio of tannic acid-modified aluminum nitride in the outer layer to ethylene-butyl acrylate-glycidyl methacrylate terpolymer in the core layer is 1:4-5.

3. The ultrafine denier ES fiber according to claim 1, characterized in that: The method for preparing tannic acid-modified aluminum nitride is as follows: Tannic acid is added to Tris buffer solution, zinc chloride and polyethyleneimine are added, and the mixture is stirred evenly to obtain the treatment solution; Aluminum nitride is soaked in the treatment solution for 10-12 hours, filtered, washed with deionized water, and dried. The amount of tannic acid used in the tannic acid-modified aluminum nitride is 3-6% of the mass of aluminum nitride.

4. The ultrafine denier ES fiber according to claim 1, characterized in that: The core layer contains 1-3 parts by weight of moisture-barrier filler.

5. The ultrafine denier ES fiber according to claim 4, characterized in that: The moisture-barrier filler is tributylhexylphosphine bromide intercalated montmorillonite supported on silver oxide.

6. The ultrafine denier ES fiber according to claim 5, characterized in that: In the tributylhexylphosphorus bromide intercalated montmorillonite-loaded nanosilver, the mass ratio of montmorillonite, tributylhexylphosphorus bromide, and nanosilver is 1:0.5-0.6:0.1-0.

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7. The ultrafine denier ES fiber according to claim 1, characterized in that: The antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076; The dispersant is succinimide; The antistatic agent is a mixture of glyceryl trilaurate and ethoxylated alkyl acid; The toughening agent is an acrylonitrile-butadiene-styrene copolymer.

8. The ultrafine denier ES fiber according to claim 1, characterized in that: The nucleating agent is selected from at least one of hydrotalcite, montmorillonite, nano-magnesium oxide, and nano-silica.

9. The method for preparing ultrafine denier ES fibers according to any one of claims 1-8, characterized in that, Includes the following steps: PE resin is mixed with tannic acid-modified aluminum nitride, toughening agent, antioxidant, dispersant and antistatic agent, and stirred at 63-67℃ for 40-50 min to obtain the skin material; PET resin is mixed with maleic anhydride-grafted polyethylene, ethylene-butyl acrylate-glycidyl methacrylate terpolymer and nucleating agent, and stirred at 80-90℃ for 40-50 min to obtain core material. The sheath material and the core material are melted separately to obtain sheath melt and core melt, which are then processed by composite spinning, cooling, stretching, heat treatment and cutting to obtain ultrafine denier ES fiber.

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