Flame-retardant antibacterial skin-friendly functional lyocell fiber and preparation method thereof

Abstract

The invention provides a flame-retardant antibacterial skin-friendly functional lyocell fiber and a preparation method thereof, and belongs to the field of fiber materials.The flame-retardant antibacterial skin-friendly functional lyocell fiber is prepared by preparing microencapsulated melamine phosphate powder and an amino acid cross-linked phytic acid solution, infiltrating the microencapsulated melamine phosphate powder into the amino acid cross-linked phytic acid solution, curing, washing and drying, and the flame-retardant antibacterial skin-friendly functional lyocell fiber is obtained. Modified flame retardant powder is obtained; dissolving pulp in an NMMO aqueous solution, adding a stabilizer, a cross-linking agent and the modified flame retardant powder, and mixing and reacting to obtain a spinning solution; and performing ultrasonic treatment and oil bath on the spinning solution, and spinning to obtain the flame-retardant antibacterial skin-friendly functional lyocell fiber. The phytic acid and the microencapsulated melamine phosphate are utilized to modify the lyocell fibers through crosslinking and curing, efficient, durable, flame-retardant and antibacterial effects are achieved, the preparation process is simple, and the lyocell fibers can be widely applied to the fields of close-fitting household textile articles, medical textile articles and the like.

Description

Technical Field

[0001] This invention relates to the field of fiber materials technology, specifically to a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber and its preparation method. Background Technology

[0002] With the deepening of environmental protection and green development concepts, the textile industry is continuously raising its requirements for the functionality and sustainability of fiber materials. Antibacterial properties, flame retardancy, and skin-friendliness, as important safety properties of textiles, have become a key focus of the modern textile industry. Lyocell fiber, as a new type of green and environmentally friendly fiber, has gradually become a key research subject in the textile industry due to its good biodegradability, moisture absorption and breathability, and comfort. However, lyocell fiber itself has poor flame retardancy and antibacterial properties, and these properties significantly decrease after repeated washing, failing to meet the safety requirements for daily use. Therefore, developing textiles with durable, flame-retardant, antibacterial, and skin-friendly functional lyocell fibers is of great significance to the health and safety of infants and young children and the high-quality development of people's living standards.

[0003] Currently available antibacterial yarn fabrics are generally treated with chemical antibacterial agents, but long-term contact with the skin may pose potential health risks, and they are especially unsuitable for infants and pregnant women. In addition, yarns treated with chemical antibacterial agents are not skin-friendly and cannot meet the comfort requirements of clothing or home textiles.

[0004] In view of this, it is necessary to design a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber and its preparation method to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber and its preparation method, aiming to solve the technical problems that lyocell fiber itself lacks flame-retardant and antibacterial functions, that existing chemical modification methods have health risks and poor comfort, and that the functional durability is insufficient.

[0006] In a first aspect, this application provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers, comprising the following steps: S1. Preparation of microencapsulated melamine phosphate powder; S2. Prepare an amino acid cross-linked phytic acid solution; S3. The microencapsulated melamine phosphate powder obtained in step S1 is immersed in the amino acid crosslinked phytic acid solution obtained in step S2 for a predetermined time, and then cured, washed and dried to obtain modified flame retardant powder. S4. Dissolve the pulp in an aqueous solution of N-methylmorpholine-N-oxide, add a stabilizer, a crosslinking agent and the modified flame retardant powder obtained in step S3, and mix and react to obtain a spinning solution; S5. The spinning solution obtained in step S4 is subjected to ultrasonic treatment and oil bath, and then spun to obtain flame-retardant, antibacterial and skin-friendly functional lyocell fiber.

[0007] As a further improvement to this application, in step S1, the method for preparing the microencapsulated melamine phosphate powder includes: S11. Grind melamine phosphate to a particle size of 200~500nm and disperse it in water to obtain a suspension; S12. Add melamine-formaldehyde prepolymer to the suspension, adjust the pH to 3-4, react at 50-70℃ for 1-3 hours, then heat to 75-85℃ to solidify, and after cooling, filtering, washing and drying, obtain microencapsulated melamine phosphate powder.

[0008] As a further improvement of this application, the melamine phosphate to the melamine-formaldehyde prepolymer has a mass ratio of 1:(1~4).

[0009] As a further improvement of this application, in step S2, the preparation method of the amino acid crosslinked phytic acid solution includes: adding 1-5% by mass of amino acids to the phytic acid aqueous solution, stirring evenly at room temperature to obtain the amino acid crosslinked phytic acid solution.

[0010] As a further improvement of this application, the amino acid is one or more of cysteine, glycine, arginine, and glutamic acid; and the mass concentration of the phytic acid aqueous solution is 30-50%.

[0011] As a further improvement of this application, in step S3, the immersion temperature is 55~65℃ and the immersion time is 1~3h; The curing temperature is 75~85℃.

[0012] As a further improvement of this application, in step S4, the stabilizer is propyl gallate, and the amount used is 0.03~0.05% of the pulp mass; the crosslinking agent is cysteine, and the amount used is 0.3~1% of the pulp mass. The amount of the modified flame retardant powder used is 5-30% of the mass of the pulp; The mass concentration of the N-methylmorpholine-N-oxide aqueous solution is 45-65%; The reaction is carried out at a temperature of 45-75°C for 30-60 minutes.

[0013] As a further improvement of this application, in step S5, the ultrasonic treatment time is 30~45 min and the ultrasonic frequency is 50~60 kHz. The oil bath temperature is 85~105℃, and the time is 1~3h; The spinning temperature is 90~100℃, the spinning speed is 35~50m / min, the coagulation bath is a 20~50wt% N-methylmorpholine-N-oxide aqueous solution, and the coagulation bath temperature is 35~65℃.

[0014] As a further improvement of this application, step S5 further includes immersing the spun fibers in an amino acid crosslinking phytic acid solution at 45-60°C for 15-25 minutes.

[0015] Secondly, this application provides a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber, which is prepared by the method described in the first aspect.

[0016] The beneficial effects of this application are as follows: This application provides a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber and its preparation method. The method involves preparing microencapsulated melamine phosphate powder and an amino acid crosslinked phytic acid solution. The microencapsulated melamine phosphate powder is impregnated in the amino acid crosslinked phytic acid solution, followed by curing, washing, and drying to obtain a modified flame retardant powder. Pulp is dissolved in an N-methylmorpholine-N-oxide aqueous solution, and a stabilizer, crosslinking agent, and modified flame retardant powder are added and mixed to obtain a spinning solution. The spinning solution is then subjected to ultrasonic treatment and an oil bath before spinning to obtain the flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. This application fully utilizes the antibacterial and flame-retardant components of phytic acid, organically combining phytic acid with lyocell fiber. Furthermore, it employs pulp and amino acid cross-linking agents to fix the effective antibacterial and flame-retardant components within the lyocell fiber. The fiber is then immersed in a low-concentration antibacterial agent for cross-linking and adsorption during the initial spinning and unsettled stage. Simultaneously, addressing the difficulty of uniformly combining microencapsulated melamine phosphate with lyocell fiber, a reasonable dispersion method was developed, ensuring better and more uniform distribution of both components in the spinning solution. This achieves uniform distribution within the lyocell fiber. The combination of microencapsulated melamine phosphate and phytic acid enhances its high flame-retardant efficiency and durability, resulting in a phytic acid-microencapsulated modified flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. This fiber exhibits excellent flame-retardant and antibacterial properties, good washability, and moisture-wicking and breathable properties after being woven into fabric.

[0017] This application makes full use of the natural components of phytic acid. By utilizing the antioxidant properties of phytic acid, the fibers can be protected from damage caused by external environmental factors (such as ultraviolet rays and air pollution) during daily use. In addition, the antibacterial, anti-radiation and skin care functions of phytic acid endow lyocell fiber blended products with additional health benefits, making them a high-value-added functional textile suitable for use in fields that require high comfort and hygiene safety, such as underwear, bedding, baby clothes and medical care products.

[0018] This application uses N-methylmorpholine-N-oxide solution to dissolve cellulose to prepare a spinning solution. After ultrasonic dispersion, the spinning solution is uniform, without agglomeration, and has a suitable viscosity, which is conducive to spinning. Subsequent processes will not cause loss of the fibrous properties of the raw material. The resulting fiber has excellent mechanical properties, which is conducive to large-scale spinning.

[0019] The preparation process of this application is simple and low-cost, suitable for industrial production, and can be widely used in fields such as intimate home textile materials and medical textile materials, with broad market application prospects.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0022] Figure 1 A flowchart illustrating the preparation method of flame-retardant, antibacterial, and skin-friendly functional lyocell fiber provided in this application embodiment; Figure 2 This is a comparison image of melamine phosphate before and after microencapsulation in Example 1 of this application; Figure 3 These are microscopic morphology images of the lyocell fibers obtained in Examples 1-2 and Comparative Examples 1-4 of this application. Figure 4 This is a diagram illustrating the antibacterial effect of the lyocell fiber obtained in Example 1 of this application. Figure 5 Cytotoxicity tests of the Lyocell fibers obtained in Examples 1-2 and Comparative Example 1 of this application; Figure 6 Cell proliferation assays of Lyocell fibers obtained in Examples 1-2 and Comparative Example 1 of this application. Detailed Implementation

[0023] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0025] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0028] Lyocell fiber itself has poor flame retardancy and antibacterial properties, and these properties significantly decrease after repeated washing, failing to meet safety requirements for daily use. Currently, flame retardant modification of lyocell fiber faces unique challenges such as fibrillation tendency, solvent compatibility, and cross-linking control. Furthermore, due to the inherent high fibrillation tendency of lyocell fiber, the introduction of chemicals during flame retardant treatment may exacerbate this phenomenon, leading to decreased fiber strength and surface fuzzing.

[0029] To address the technical problems of poor flame retardant and antibacterial properties of lyocell fiber itself and the health risks and performance degradation associated with existing chemical modifications, this application provides a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber and its preparation method. This method utilizes a compound of phytic acid and microencapsulated melamine phosphate, and optimizes the fiber production process to achieve cross-linking adsorption and uniform dispersion of functional components during spinning. This results in highly efficient and long-lasting flame retardant and antibacterial properties, natural skin-friendliness and safety, washability, and protection of the fiber from environmental damage.

[0030] Please refer to Figure 1 In a first aspect, embodiments of this application provide a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers, comprising the following steps: S1. Preparation of microencapsulated melamine phosphate powder; S2. Prepare an amino acid cross-linked phytic acid solution; S3. The microencapsulated melamine phosphate powder obtained in step S1 is immersed in the amino acid crosslinked phytic acid solution obtained in step S2 for a predetermined time, and then cured, washed and dried to obtain the modified flame retardant powder. S4. Dissolve the pulp in an aqueous solution of N-methylmorpholine-N-oxide, add a stabilizer, a crosslinking agent and the modified flame retardant powder obtained in step S3, and mix and react to obtain a spinning solution; S5. The spinning solution obtained in step S4 is subjected to ultrasonic treatment and oil bath before spinning to obtain flame-retardant, antibacterial and skin-friendly functional lyocell fiber.

[0031] In the technical solution of this application embodiment, microencapsulated melamine phosphate is prepared by a specific method and impregnated with amino acid crosslinked phytic acid solution to construct an intumescent flame retardant system, while introducing antibacterial groups; through the crosslinking agent and ultrasonic dispersion, the modified flame retardant is uniformly dispersed in the N-methylmorpholine-N-oxide (NMMO) solvent system and chemically bonded to cellulose macromolecules, and finally spun and shaped to obtain functional lyocell fiber with excellent flame retardant, antibacterial and skin-friendly properties.

[0032] Furthermore, in some embodiments, the method for preparing microencapsulated melamine phosphate powder in step S1 includes: S11. Grind melamine phosphate to a particle size of 200~500nm and disperse it in water to obtain a suspension; S12. Add melamine-formaldehyde prepolymer to the suspension, adjust the pH to 3-4, react at 50-70℃ for 1-3 hours, then heat to 75-85℃ to solidify, and after cooling, filtering, washing and drying, obtain microencapsulated melamine phosphate powder.

[0033] In the technical solution of this application embodiment, melamine phosphate is first ground using a ball mill to achieve a suitable particle size range, and then microencapsulated melamine phosphate is prepared, which helps to achieve better coating rate and spinnability. Specifically, the grinding speed is 500~2000 r / min, and the grinding time is 15~90 min. The drying temperature is 35~45℃.

[0034] Furthermore, in some embodiments, the mass ratio of melamine phosphate to melamine-formaldehyde prepolymer is 1:(1~4).

[0035] In the technical solution of this application embodiment, an alkali-resistant wall material (such as melamine resin) is selected to avoid damage to the spinning solution, and the core-to-wall ratio is controlled within a suitable range, which helps to improve its coating rate and spinning flowability. Specifically, the preparation method of melamine-formaldehyde prepolymer is as follows: melamine and formaldehyde are mixed at a molar ratio of 1:4 (7g of melamine and 18mL of 37% formaldehyde aqueous solution), 60mL of deionized water is added, the pH value of the system is adjusted to 8.5~9 with 10% sodium carbonate solution, the temperature is raised to 70~75℃, and the reaction is stirred for 30~60min until the solution is clear and transparent.

[0036] Further, in some embodiments, in step S2, the method for preparing the amino acid cross-linked phytic acid solution includes: adding 1-5% by mass of amino acids to an aqueous phytic acid solution, stirring evenly at room temperature to obtain the amino acid cross-linked phytic acid solution. The amino acids are one or more selected from cysteine, glycine, arginine, and glutamic acid; the mass concentration of the aqueous phytic acid solution is 30-50%.

[0037] In the technical solution of this application embodiment, an amino acid-phytic acid composite system is constructed by utilizing the abundant phosphate groups in the phytic acid molecular structure to conduct intermolecular interactions or pre-reactions with the active groups such as amino and carboxyl groups in amino acids. The introduction of phytic acid provides the core active ingredient for the subsequent realization of flame retardant and antibacterial functions. At the same time, the amphoteric properties and reducing properties of amino acids improve the reactivity and stability of the solution system, enhance the affinity between functional molecules and cellulose matrix, and endow the system with potential antioxidant and skin-friendly properties, laying the foundation for subsequent cross-linking curing and fiber modification.

[0038] Furthermore, in some embodiments, in step S3, the impregnation temperature is 55~65°C, the impregnation time is 1~3h, and the curing temperature is 75~85°C.

[0039] In the technical solution of this application embodiment, a suitable wetting temperature promotes the penetration and diffusion of amino acid crosslinked phytic acid solution into the surface of melamine phosphate microcapsules, and the physical adsorption and chemical interaction between phytic acid molecules and microcapsule wall material achieves initial bonding; at a suitable curing temperature, the crosslinking condensation reaction of amino acids with microcapsule surface groups and phytic acid molecules is accelerated, and a stable modified layer is constructed on the surface of the microcapsules, thereby effectively fixing the flame retardant and antibacterial components, and significantly improving the stability and durability of the modified flame retardant powder in the subsequent spinning process.

[0040] Furthermore, in some embodiments, in step S4, the stabilizer is propyl gallate, and the amount used is 0.03~0.05% of the pulp mass; the crosslinking agent is cysteine, and the amount used is 0.3~1% of the pulp mass; the amount of modified flame retardant powder is 5~30% of the pulp mass; the mass concentration of the N-methylmorpholine-N-oxide aqueous solution is 45~65%; the reaction temperature is 45~75℃, and the time is 30~60min.

[0041] In the technical solution of this application embodiment, the addition of a stabilizer effectively inhibits the oxidative degradation of the NMMO system during high-temperature dissolution, ensuring the rheological stability of the spinning solution. By utilizing the chemical interaction between the cysteine ​​crosslinking agent, cellulose hydroxyl groups, and the modified flame retardant, chemical bonding sites are constructed, solving the problem of easy aggregation and uneven dispersion of microcapsule particles in viscous systems, and achieving uniform fusion of the functional phase and the matrix phase. Suitable reaction temperature and time help the active substances to fully crosslink in the spinning solution, preventing precipitation. Specifically, the cellulose pulp is one of hemp pulp, straw pulp, cotton pulp, wood pulp, or bamboo pulp.

[0042] Furthermore, in some embodiments, in step S5, the ultrasonic treatment time is 30-45 min, the ultrasonic frequency is 50-60 kHz; the oil bath temperature is 85-105°C, and the time is 1-3 h; the spinning temperature is 90-100°C, the spinning speed is 35-50 m / min, the coagulation bath is a 20-50 wt% N-methylmorpholine-N-oxide aqueous solution, and the coagulation bath temperature is 35-65°C.

[0043] In the technical solution of this application embodiment, the ultrasonic cavitation effect is used to further disperse the flame retardant agglomerates, ensuring that they are uniformly dispersed in the spinning solution; excess water is removed by oil bath heating to regulate the rheological properties and spinnability of the spinning solution; under suitable spinning temperature and speed, the cellulose macromolecular chains and the modified flame retardant they encapsulate are oriented axially; subsequently, in a coagulation bath with a specific concentration and temperature, the fiber is rapidly solidified and formed by the dual diffusion mechanism of solvent and coagulant, effectively anchoring the flame retardant and antibacterial components inside the fiber matrix, ensuring the structural integrity and functional uniformity of the nascent fiber.

[0044] Specifically, the spinning solution is added to a screw extruder and further dissolved at 90-110℃. After filtration and defoaming for 10-30 minutes, it enters the spinning system for spinning. The filaments are vertically stretched in the air and enter the coagulation bath. The air gap length of the spinning system is 2-3 cm, the spinning speed is 35-50 m / min, the spinneret orifice diameter is 15-115 µm, the capillary length is 300-400 µm, and the coagulation bath contains 20-50 wt% NMMO aqueous solution at a temperature of 35-65℃. The nascent fibers are obtained after a water bath at 45-55℃.

[0045] Furthermore, in some embodiments, step S5 further includes immersing the spun fibers in an amino acid crosslinked phytic acid solution at 45-60°C for 15-25 minutes.

[0046] In the technical solution of this application embodiment, thermodynamic driving force is used to promote the amino acid crosslinking phytic acid solution to penetrate into the internal pores of the nascent fiber and adsorb onto the surface. Subsequently, the temperature is raised to 80~100℃ for curing, and then dried at 120~160℃ for 5~10 minutes. After alcohol washing, water washing, oiling, and drying, flame-retardant, antibacterial, and skin-friendly functional lyocell fiber is obtained. During the temperature curing process, amino acids undergo dehydration condensation or crosslinking reactions with the hydroxyl groups on the fiber molecular chain to build a stable network structure, effectively anchoring phytic acid to the fiber, significantly improving the wash resistance and durability of the flame-retardant and antibacterial function. The alcohol washing, water washing, oiling, and drying processes remove unreacted impurities and shape the fiber, further optimizing the microstructure of the fiber and giving it excellent skin-friendliness and final performance.

[0047] Secondly, embodiments of this application provide a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber, which is prepared by the above method.

[0048] Through the synergistic effect of microencapsulated melamine phosphate and phytic acid, a durable and stable flame-retardant and antibacterial system is formed within the fiber. The microcapsule structure effectively prevents the migration and loss of flame retardants, and the cross-linking and fixation of phytic acid and amino acids ensures that the fiber maintains excellent flame-retardant and antibacterial properties even after multiple washes. Simultaneously, the introduction of amino acids and phytic acid endows the fiber with good skin-friendliness, antioxidant properties, and biocompatibility, solving the problems of poor comfort and potential health risks associated with traditional functional textiles.

[0049] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0050] I. Preparation Method Example 1 This embodiment provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers, including the following steps: S1. Grind 50g of melamine phosphate using a ball mill at a speed of 1000r / min until the particle size range is 200~500nm. Mix it with 100mL of water containing 1% SDS emulsifier and ultrasonically disperse for 30min to obtain a stable suspension. Melamine and formaldehyde were mixed at a molar ratio of 1:4 (7g melamine and 18mL of 37% formaldehyde aqueous solution), and 60mL of deionized water was added. The pH of the system was adjusted to 8.5 with 10% sodium carbonate solution, and the temperature was raised to 70℃. The mixture was stirred for 45min to obtain a melamine-formaldehyde prepolymer. The melamine-formaldehyde prepolymer was added to the suspension at a mass ratio of melamine phosphate to melamine-formaldehyde prepolymer of 1:3. The pH was adjusted to 4 with 10% citric acid, and the mixture was reacted in a 60℃ water bath for 2h. Afterward, the temperature was raised to 80℃ for curing. The mixture was cooled, filtered, washed with water until neutral, and then vacuum dried at 40℃ for 8h to obtain microencapsulated melamine phosphate powder (MC-MP powder). Figure 2 As shown, the microencapsulated melamine phosphate has a complete core-shell structure and its particle size distribution is between 1 and 5 μm. S2. Add cysteine ​​(1 wt% of the phytic acid aqueous solution) to a 35 wt% phytic acid aqueous solution and stir the mixture at room temperature for 30 min to obtain a cysteine-crosslinked phytic acid solution. S3. The MC-MP powder was immersed in a cysteine-crosslinked phytic acid solution and immersed at 60°C for 2 hours. Then the temperature was raised to 80°C for curing. After cooling, filtration, and washing with water until neutral, the powder was vacuum dried at 40°C to obtain the modified flame retardant powder. S4. Dissolve cotton pulp in a 50wt% NMMO aqueous solution at a mass ratio of 1:10, add 25% of the modified flame retardant powder by mass of cotton pulp, then add 0.04% of propyl gallate stabilizer and 0.6% of cysteine ​​crosslinking agent by mass of cotton pulp, and crosslink the mixture in a reactor at 60℃ for 45 min to obtain a spinning solution. S5. The spinning solution is ultrasonically treated for 45 minutes at a frequency of 60 kHz; then, the oil bath is heated to 95 ℃ and vacuum stirred for 3 hours at a stirring speed of 200 r / min to obtain a composite spinning solution; the composite spinning solution is added to a screw extruder and further dissolved at 100 ℃, then filtered and defoamed for 30 minutes, and then fed into the spinning system for spinning at a spinning temperature of 100 ℃ and a spinning speed of 40 m / min. The extruded filaments are vertically stretched in the air and enter a coagulation bath of 20 wt% NMMO aqueous solution at 45 ℃. After the first drafting, the filaments continue to enter a water bath of deionized water at 55 ℃. The first drafting ratio is 1:5, and the second take-up drafting ratio is 1:20. After alcohol washing, water washing, oiling, and drying, the finished fiber is obtained.

[0051] Example 2 This embodiment provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers. Compared with Example 1, the only difference is that in step S5, the spun fibers are immersed in a cysteine ​​crosslinked phytic acid solution at 50°C for 15 minutes, then heated to 80°C for 10 minutes to cure, placed in an oven and dried at 120°C for 5 minutes, and finally washed with alcohol, washed with water, oiled, and dried to obtain the finished fibers. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0052] Example 3 This embodiment provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. Compared with Example 1, the only difference is that in step S4, the amount of modified flame retardant powder is 5% of the mass of cotton pulp. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0053] Example 4 This embodiment provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. Compared with Example 1, the only difference is that in step S4, the amount of modified flame retardant powder is 30% of the mass of cotton pulp. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0054] Example 5 This embodiment provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. Compared with Example 1, the only difference is that in step S1, the mass ratio of melamine phosphate to melamine-formaldehyde prepolymer is 1:1. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0055] Example 6 This embodiment provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. Compared with Example 1, the only difference is that in step S1, the mass ratio of melamine phosphate to melamine-formaldehyde prepolymer is 1:4. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0056] Comparative Example 1 This comparative example provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers, including the following steps: S1. Dissolve cotton pulp in 50wt% NMMO aqueous solution at a mass ratio of 1:10, add 0.04% propyl gallate stabilizer, and crosslink in a reactor at 60℃ for 45 min to obtain spinning solution; S2. The spinning solution was ultrasonically treated for 45 minutes at a frequency of 60 kHz; then, the oil bath temperature was raised to 95 ℃ and vacuum stirred for 3 hours at a stirring speed of 200 r / min to obtain a composite spinning solution with a concentration of 93%; the spinning solution was added to a screw extruder and further dissolved at 100 ℃, then filtered to remove bubbles for 30 minutes, and then entered the spinning system for spinning at a spinning temperature of 100 ℃ and a spinning speed of 40 m / min. The extruded filaments were vertically stretched in the air and entered a coagulation bath of 20 wt% NMMO aqueous solution at 45 ℃. After the first drafting, the filaments continued to enter a water bath of deionized water at 55 ℃. The first drafting ratio was 1:5 m / min, and the second take-up drafting ratio was 1:20 m / min. After alcohol washing, water washing, oiling, and drying, lyocell fibers were obtained.

[0057] Comparative Example 2 This comparative example provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers. The only difference from Example 1 is that melamine phosphate was not microencapsulated or impregnated with cysteine-crosslinked phytic acid solution. Instead, cotton pulp and melamine phosphate were directly dissolved in NMMO aqueous solution at a mass ratio of 4:1. Other experimental parameters and conditions were basically the same as in Example 1 and will not be repeated here.

[0058] Comparative Example 3 This comparative example provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers. The only difference from Example 1 is that melamine phosphate was not microencapsulated or impregnated with cysteine-crosslinked phytic acid solution. Instead, cotton pulp and melamine phosphate were directly dissolved in NMMO aqueous solution at a mass ratio of 2:1. Other experimental parameters and conditions are basically the same as in Example 1 and will not be repeated here.

[0059] Comparative Example 4 This comparative example provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fibers. The only difference from Example 1 is that the MC-MP powder was not impregnated in a cysteine ​​crosslinked phytic acid solution. Instead, cotton pulp and MC-MP powder were directly dissolved in an NMMO aqueous solution at a mass ratio of 4:1. Other experimental parameters and conditions are basically the same as in Example 1 and will not be repeated here.

[0060] Comparative Example 5 This comparative example provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. Compared with Example 1, the only difference is that in step S4, the amount of modified flame retardant powder is 3% of the mass of cotton pulp. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0061] Comparative Example 6 This comparative example provides a method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber. The only difference from Example 1 is that in step S4, the amount of modified flame retardant powder is 40% of the mass of cotton pulp. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0062] like Figure 3 As shown, a~f are the microstructure images of Lyocell fibers obtained by Comparative Examples 1-4 and Examples 1-2, respectively. It can be seen that after adding melamine phosphate, the fiber samples show long-range ordered stripes, while when 25% microencapsulated melamine phosphate is added, the samples show micron-level protrusion structures, and the surface structure is more regular after post-treatment.

[0063] like Figure 4 As shown, ab represents the comparison of the antibacterial effect of Example 1 on Staphylococcus aureus, a is the control group without fiber, and b is the experimental group; de represents the comparison of the antibacterial effect of Example 1 on Escherichia coli, d is the control group without fiber, and e is the experimental group; it can be seen that the fiber prepared in this application has excellent antibacterial properties.

[0064] like Figure 5 As shown, the cell compatibility of the fibers was assessed through cell testing and MTT assay. In the Live / Dead cell experiment, the negative control group received no fiber sample and was cultured normally, serving as the baseline; the negative control group received only solvent, serving as a parallel blank; and the positive control group served as the quality control sample. In both the control and experimental groups, only a few cells appeared red (dead cells), while the vast majority of cells appeared green (live cells) and maintained normal spindle morphology. This indicates that phytic acid-microencapsulated melamine phosphate-modified lyocell fibers do not cause cell death and exhibit good cell compatibility. Figure 6As shown, in the cell proliferation assay, no fiber sample was added to the control group, and the cytotoxicity rating of the experimental group was Grade I (≥75%), indicating that the fiber does not release toxic compounds that inhibit cell proliferation.

[0065] II. Testing Methods 1. Elongation at break test The breaking elongation of the fiber was tested using an XQ-1AN fiber tensile tester. Thirty fibers from different locations were taken from different samples, and the average breaking elongation was recorded. 2. Strength test The strength of the fibers was tested using an XQ-1AN fiber tensile tester. Thirty fibers from different locations were taken from different samples, and the average strength was recorded. 3. Flame retardancy test The flame retardant properties of the lyocell fibers obtained in the above examples and comparative examples were tested in accordance with the standard GB / T 5454-1997 "Textiles - Test for Burning Performance - Oxygen Index Method". 4. Antibacterial test Antibacterial tests were conducted on the lyocell fibers obtained in the above examples and comparative examples, according to the standard GB / T20944.2-2007 "Evaluation of antibacterial properties of textiles - Part 2: Absorption method", with Staphylococcus aureus and Escherichia coli as the bacterial strains. 5. Cytotoxicity test The lyocell fibers obtained in the above examples and comparative examples were subjected to cytotoxicity tests in accordance with the standard GB / T 16886 "Biological Evaluation of Medical Devices".

[0066] III. Analysis of Test Results for Each Embodiment and Comparative Example The test results of each embodiment and comparative example are shown in Table 1.

[0067] Table 1. Test results for each embodiment and comparative example. "—" indicates no antibacterial effect.

[0068] As shown in Table 1, the lyocell fibers prepared in the embodiments of this application all exhibit excellent flame retardancy and antibacterial properties. The LOI of Example 2 is >60%, significantly higher than other samples, indicating that the post-treatment step of adding amino acid crosslinking phytic acid solution after spinning further crosslinks and fixes the flame retardant components on the fiber surface and inside, forming a denser flame retardant layer. Although the mechanical properties of Examples 1-6 are slightly different from pure lyocell fibers due to functional modification, their strength and elongation at break are within the reasonable range for functional fibers, meeting the basic requirements for mechanical properties in subsequent textile processing and end applications. Comparative Examples 1-4, without the addition of antibacterial components, showed no antibacterial effect, indicating that phytic acid and its crosslinking system are extremely efficient in antibacterial properties and are not affected by microencapsulation, post-treatment, or other processes. In Comparative Example 5, the amount of modified flame retardant powder was too small, resulting in insufficient flame retardant performance. In Comparative Example 6, the amount of flame retardant added was too large, exceeding its load limit, leading to problems such as intermittent spinning and needle blockage during spinning, resulting in spinning failure.

[0069] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a flame-retardant, antibacterial, and skin-friendly functional lyocell fiber, characterized in that, Includes the following steps: S1. Preparation of microencapsulated melamine phosphate powder; S2. Prepare an amino acid cross-linked phytic acid solution; S3. The microencapsulated melamine phosphate powder obtained in step S1 is immersed in the amino acid crosslinked phytic acid solution obtained in step S2 for a predetermined time, and then cured, washed and dried to obtain modified flame retardant powder. S4. Dissolve the pulp in an aqueous solution of N-methylmorpholine-N-oxide, add a stabilizer, a crosslinking agent and the modified flame retardant powder obtained in step S3, and mix and react to obtain a spinning solution; S5. The spinning solution obtained in step S4 is subjected to ultrasonic treatment and oil bath, and then spun to obtain flame-retardant, antibacterial and skin-friendly functional lyocell fiber.

2. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 1, characterized in that, In step S1, the method for preparing the microencapsulated melamine phosphate powder includes: S11. Grind melamine phosphate to a particle size of 200~500nm and disperse it in water to obtain a suspension; S12. Add melamine-formaldehyde prepolymer to the suspension, adjust the pH to 3-4, react at 50-70℃ for 1-3 hours, then heat to 75-85℃ to solidify, and after cooling, filtering, washing and drying, obtain microencapsulated melamine phosphate powder.

3. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 2, characterized in that, The mass ratio of melamine phosphate to the melamine-formaldehyde prepolymer is 1:(1~4).

4. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 1, characterized in that, In step S2, the preparation method of the amino acid cross-linked phytic acid solution includes: adding 1-5% by mass of amino acids to an aqueous phytic acid solution, stirring evenly at room temperature to obtain the amino acid cross-linked phytic acid solution.

5. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 4, characterized in that, The amino acid is one or more of cysteine, glycine, arginine, and glutamic acid; the phytic acid aqueous solution has a mass concentration of 30-50%.

6. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 1, characterized in that, In step S3, the immersion temperature is 55~65℃, and the immersion time is 1~3h; The curing temperature is 75~85℃.

7. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 1, characterized in that, In step S4, the stabilizer is propyl gallate, and the amount used is 0.03~0.05% of the pulp mass; the crosslinking agent is cysteine, and the amount used is 0.3~1% of the pulp mass. The amount of the modified flame retardant powder used is 5-30% of the mass of the pulp; The mass concentration of the N-methylmorpholine-N-oxide aqueous solution is 45-65%; The reaction is carried out at a temperature of 45-75°C for 30-60 minutes.

8. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 1, characterized in that, In step S5, the ultrasonic treatment time is 30-45 minutes and the ultrasonic frequency is 50-60 kHz. The oil bath temperature is 85~105℃, and the time is 1~3h; The spinning temperature is 90~100℃, the spinning speed is 35~50m / min, the coagulation bath is a 20~50wt% N-methylmorpholine-N-oxide aqueous solution, and the coagulation bath temperature is 35~65℃.

9. The method for preparing flame-retardant, antibacterial, and skin-friendly functional lyocell fiber according to claim 1, characterized in that, Step S5 further includes immersing the spun fibers in an amino acid crosslinked phytic acid solution at 45-60°C for 15-25 minutes.

10. A flame-retardant, antibacterial, and skin-friendly functional lyocell fiber, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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