Preparation method of high-spinnable flame-retardant lyocell fiber with high precipitation resistance

Abstract

The present application relates to the technical field of fiber production process control, especially to a preparation method of a high-spinnable flame-retardant lyocell fiber with precipitation resistance, comprising the following steps: S1. treating cellulose pulp and regulating hemicellulose through a low-temperature activation process; S2. selecting a flame retardant and adjusting the crystal face exposure ratio of the flame retardant; S3. uniformly mixing the treated cellulose pulp and the flame retardant; S4. then performing free radical scavenging treatment to prepare stable spinning solution; S5. performing spinning through a dry-jet wet spinning process to ensure uniformity of the yarn formation; S6. performing crosslinking treatment on the nascent fiber; and S7. performing quality detection on the finished fiber and screening qualified products. The present application precisely controls the uniform distribution of the crosslinking agent in the fiber cross section through a radial penetration lag gradient formula of the crosslinking agent, ensures the dispersion stability of the flame retardant in the spinning solution, makes the flame retardant and the cellulose molecules form a firm crosslinking combination, effectively locks the flame-retardant components, meets the long-term use requirements of textiles, and improves the safety of the products.

Description

Technical Field

[0001] This invention relates to the field of fiber production process control technology, and in particular to a method for preparing highly spinnable flame-retardant lyocell fibers with resistance to exudation. Background Technology

[0002] As lyocell fibers are gradually applied to special scenarios such as petrochemical protective clothing, rail transit interior fabrics, and public safety home textiles, the industry has begun to require products not only to meet basic flame retardant standards, but also to maintain stable flame retardant performance under service conditions of repeated wet and hot washing and long-term mechanical friction, while adapting to the continuous processing needs of high-speed spinning. This places higher demands on the fiber's resistance to exudation and its adaptability to spinning processing.

[0003] Traditional flame-retardant lyocell fibers are mostly prepared using a solvent-based dry-jet wet spinning process. This process typically involves dissolving cellulose pulp in a solvent and then blending it with phosphorus and nitrogen-based flame retardants to create a spinning solution. The finished product is then obtained after spinning, coagulation, washing, drying, and conventional cross-linking treatment. The production process only controls conventional indicators such as the amount of flame retardant added, the viscosity of the spinning solution, the concentration of the coagulation bath, and the fiber oxygen index.

[0004] It can be seen that existing traditional preparation processes have the following shortcomings when applied in the above-mentioned special scenarios:

[0005] First, traditional preparation processes mostly involve uniform control of conventional process parameters, resulting in insufficient bonding strength between the flame retardant and the cellulose matrix. Under special conditions of humid and hot washing and friction, the flame retardant is prone to migration and precipitation, directly leading to the degradation of the fiber's flame retardant performance and failing to meet the requirements for long-term safe service under harsh conditions.

[0006] Secondly, fluid convection at the spinning coagulation interface, cavitation of the washing water flow, and fluctuations in the spinning solution potential can easily cause the internal pore structure of the fiber to become disordered and have poor uniformity. This will not only further aggravate the precipitation of flame retardants, but also cause an imbalance in the friction and electrostatic state of the fiber surface. In the process of high-speed spinning, problems such as frequent yarn breakage and excessive hairiness are likely to occur, which cannot meet the processing needs of large-scale and continuous production of fabrics for special scenarios.

[0007] The aforementioned problems have not yet been specifically addressed in existing technologies. Therefore, it is of great practical necessity to design a method for preparing and controlling the quality of flame-retardant lyocell fibers with stable flame retardant properties, resistance to exudation, and high spinnability. Summary of the Invention

[0008] To solve one of the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing flame-retardant lyocell fiber with high spinnability and resistance to exudation, comprising the following steps: S1. Purifying and pulverizing cellulose pulp, and then controlling hemicellulose through a low-temperature activation process.

[0009] S2. Select a flame retardant, grind it, and then use a silane coupling agent to modify its surface and adjust the crystal face exposure ratio of the flame retardant.

[0010] S3. Mix the treated cellulose pulp with the flame retardant and add a polycarboxylic acid dispersant, and achieve uniform mixing by high-speed stirring.

[0011] S4. Then, a free radical scavenging treatment is performed to control and remove residual peroxide free radicals in the system, thus preparing a stable spinning solution.

[0012] S5. The dry-jet wet spinning process is used for spinning, and the airflow velocity, temperature and humidity of the air layer are controlled. At the same time, the fluid convection at the solidification interface is suppressed to ensure uniform filament formation.

[0013] S6. Perform cross-linking treatment on the nascent fibers after spinning, and control the penetration depth and uniformity of the cross-linking agent to ensure that the cross-linking agent penetrates evenly into the fiber interior.

[0014] S7. Conduct quality inspections on the finished fibers and screen qualified products.

[0015] As a preferred embodiment, the flame retardant surface modification and crystal plane control process in step S2 and the raw material mixing and dispersion process in step S3 are performed according to the following steps: the ground flame retardant and silane coupling agent are added into a closed reaction vessel with temperature control and stirring functions according to a preset mass ratio.

[0016] First, raise the temperature inside the reactor to the modification temperature range of 55℃-65℃ at a uniform heating rate of 2℃ / min. After the temperature inside the reactor stabilizes, start stirring and keep the stirring speed stable in the range of 300r / min-500r / min. Continue to stir and react at a constant temperature for 120min-180min.

[0017] After completing the surface modification treatment of the flame retardant and precisely adjusting the crystal face exposure ratio, stop stirring after the reaction is complete, and allow the material in the reactor to cool naturally to room temperature to obtain the modified nano flame retardant for later use.

[0018] The cellulose pulp pretreated in step S1 and the modified nano flame retardant are added sequentially to a mixing vessel with online monitoring function according to a preset mass ratio, while a polycarboxylic acid dispersant is added at the same time.

[0019] The zeta potential data of the flame retardant suspension in the above-mentioned mixed system is collected in real time. The oscillation amplitude of the zeta potential of the flame retardant suspension is constrained by adjusting the replenishment rate of the dispersant and the output torque of the stirring equipment in real time.

[0020] After the high-speed mixing process is completed, a uniformly dispersed mixed system is obtained.

[0021] As a preferred embodiment, the dry-jet wet spinning forming process in step SS5 includes the following steps: the prepared stable spinning solution is quantitatively delivered to the spinneret of the spinning machine by a high-precision metering pump, so that the spinning solution is extruded to form a continuous nascent filament.

[0022] The extruded nascent filaments are then fed into the air layer section of the gas layer below the spinneret. The height, temperature, relative humidity, and axial airflow velocity of the air layer are adjusted sequentially. Through the coordinated control of these parameters, the monolayer adsorption thickness of water vapor on the surface of the nascent filaments is stabilized.

[0023] After the nascent filaments pass through the gas layer, they are introduced into the coagulation bath process below, where the solvent mass fraction, bath temperature, and circulation flow rate are adjusted sequentially.

[0024] By coordinating and controlling the above parameters, fluid disturbances at the solidification interface can be suppressed.

[0025] After the nascent filaments have been solidified in the coagulation bath, a uniformly structured nascent fiber is obtained.

[0026] Among them, suppressing fluid disturbance at the solidification interface ensures that the Marangoni convection intensity at the solidification interface satisfies the following governing equation:

[0027] .

[0028] In the formula: This refers to the actual Marangoni number of the solidification interface after parameter adjustment; It represents the absolute value of the interfacial tension gradient at the interface between the coagulation bath and the nascent filaments. The thickness of the monolayer adsorption of water vapor in the air layer on the surface of the nascent filament; The effective height of the air layer; The dynamic viscosity of the coagulation bath at the set operating temperature; is the molecular diffusion coefficient of NMMO solvent in the coagulation bath; The critical Marangoni number for stable laminar flow at the solidification interface.

[0029] As a preferred embodiment, the nascent fiber crosslinking treatment process in step S6 includes the following steps: the prepared nascent fiber is guided and sent into the crosslinking bath process, and the mass fraction of the crosslinking agent, the temperature of the bath, the pH value and the circulation state of the crosslinking bath are adjusted in sequence.

[0030] Adjust the fiber traction speed to keep it synchronized with the spinning extrusion speed, and control the effective residence time of the nascent fiber in the crosslinking bath to 60s-120s, so that the crosslinking agent can fully penetrate into the fiber.

[0031] Throughout the entire process of the crosslinking agent penetrating into the fiber radially, a stable concentration distribution of the crosslinking agent in the fiber radial direction is established by controlling the concentration gradient of the crosslinking bath and the fiber residence time, constraining the penetration hysteresis gradient of the crosslinking agent in the fiber radial direction, and simultaneously matching the electrostatic charge electret decay characteristics of the fiber surface.

[0032] After the crosslinking reaction is complete, the fiber is sent out of the crosslinking bath to complete the crosslinking treatment process.

[0033] The electrostatic charge attenuation characteristics of the fiber surface satisfy the following constraint equation:

[0034] .

[0035] In the formula: This represents the penetration hysteresis gradient of the crosslinking agent in the radial direction of the fiber; This represents the actual partial derivative of the crosslinking agent concentration along the fiber radial direction; This represents the measured concentration of the crosslinking agent at any radial position of the fiber; The initial concentration of the crosslinking agent on the surface of the nascent fiber; The cross-sectional radius of the nascent fiber; The electret decay time constant of the static charge on the fiber surface; The baseline diffusion relaxation time of the crosslinking agent in the cellulose matrix; This is the allowable threshold for uniform penetration of the crosslinking agent.

[0036] As a preferred embodiment, the free radical scavenging process in step S4 includes the following steps: the mixed system is fed into a reactor, the stirring speed is stably controlled within the range of 200 r / min to 300 r / min, and the temperature inside the reactor is uniformly raised to the processing temperature range of 40℃ to 50℃ at a heating rate of 1℃ / min. After the temperature inside the reactor stabilizes, the heating is stopped and the temperature is kept constant.

[0037] Then, a segmented feeding method was adopted to add free radical scavenger into the reactor. The free radical scavenger used was propyl gallate, and the total amount added was 0.05%-0.15% of the total mass of the mixed system. The feeding was carried out in three batches of equal mass, with an interval of 10 minutes between each batch. After each batch was fed, the original speed was maintained and the stirring was continued to ensure that the free radical scavenger could be uniformly dispersed in the mixed system.

[0038] After all the free radical scavengers have been added, keep the reactor in a constant temperature and sealed state and continue stirring for 30-60 minutes to allow the free radical scavengers to fully react with the residual peroxide free radicals in the mixed system, control the removal of residual peroxide free radicals in the system, and reduce the concentration of peroxide free radicals in the system to within the threshold range allowed by the lyocell fiber spinning process.

[0039] After the free radical scavenging process is completed, stop stirring, filter the material in the reactor and send it out to obtain a stable spinning solution.

[0040] As a preferred embodiment, the flame retardant grinding process in step S2 includes the following steps: selecting phosphorus-nitrogen nano flame retardant raw materials that meet the preset purity requirements, performing preliminary screening on the raw materials to remove large particle agglomerates and impurities, and obtaining preliminarily purified flame retardant raw materials.

[0041] The preliminarily purified flame retardant raw materials, grinding media, and dispersion media are sequentially added into the cylinder of the horizontal sand mill according to a preset mass ratio.

[0042] Then, the horizontal sand mill is turned on, and the grinding process is carried out in two stages: coarse grinding and fine grinding. In the coarse grinding stage, the speed of the sand mill is set to 2000 r / min and grinding is carried out continuously for 30 minutes to initially break up the agglomerates in the flame retardant raw materials. In the fine grinding stage, the speed of the sand mill is increased to 3500 r / min and grinding is carried out continuously for 60-90 minutes to refine the flame retardant particles. During the grinding process, the temperature inside the cylinder is controlled to be stable within the range of 25℃-30℃ by the cooling jacket of the cylinder.

[0043] After the grinding process is completed, the material is discharged from the sand mill, filtered and dried to obtain the ground phosphorus-nitrogen nano flame retardant. The particle size D50 of the flame retardant after grinding is controlled in the range of 200nm-300nm.

[0044] As a preferred option, the airflow control process in step S5 includes the following steps: the air outlet is directly facing the running path of the nascent filaments to ensure that the airflow can evenly cover all the nascent filaments in the entire air layer area.

[0045] By adjusting the wind speed, the axial airflow velocity within the air layer is stably controlled within the range of 0.2m / s-0.5m / s. Furthermore, by guiding and rectifying the supply airflow, lateral turbulence and eddy disturbances in the airflow are eliminated, thereby maintaining a stable laminar flow state within the air layer.

[0046] Throughout the spinning process, temperature, relative humidity, and airflow velocity data are collected in real time by temperature and humidity sensors and wind speed sensors arranged in the air layer. The heating power, humidification, and air supply frequency of the air supply are adjusted through feedback to ensure that the parameters in the air layer are stable within the preset range, so that the fluctuation of the monolayer adsorption thickness of water vapor on the surface of the nascent filament is controlled within the allowable range.

[0047] As a preferred embodiment, after the crosslinking treatment in step S6 is completed, the gradient water washing process of the fiber includes the following steps: the crosslinked fiber is guided and then sequentially fed into a multi-stage water washing tank connected in series. Each stage of the water washing tank operates in a counter-current water supply mode, that is, deionized water is fed in from the last stage water washing tank, flows sequentially to the previous stage water washing tank, and is finally discharged from the first stage water washing tank.

[0048] The water temperature of each stage of the water washing tank is adjusted sequentially. The temperature of the first stage water washing tank is set at 40℃, and the temperature of each subsequent stage water washing tank is reduced by 5℃ until the temperature of the last stage water washing tank drops to room temperature, forming a gradient cooling water washing temperature system.

[0049] At the same time, the fiber traction speed is adjusted to keep it synchronized with the spinning speed, and the effective residence time of the fiber in each washing tank is controlled to be 30s-60s.

[0050] After the fibers have passed through all the washing tanks, the gradient washing process is completed. After washing, the residual solubility of the fibers is controlled below 0.1%, and the residual oil content is controlled within the range of 0.15%-0.3%.

[0051] As a preferred option, the finished fiber quality inspection and screening process in step S7 includes the following steps: sampling the finished fibers that have completed all post-processing steps according to a preset sampling frequency; sequentially testing the obtained fiber samples for multiple indicators; after all test items are completed, judging the test data, and fibers that meet the standard requirements for all indicators are judged as qualified products, while fibers that exceed the standard limit for any indicator are judged as unqualified products; unqualified fibers are automatically rejected, and qualified products enter the subsequent winding and packaging processes.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] 1. This invention precisely controls the uniform distribution of crosslinking agents in the fiber cross-section through the radial penetration hysteresis gradient formula of the crosslinking agent, and ensures the dispersion stability of the flame retardant in the spinning solution by combining the Zeta potential dynamic oscillation constraint formula. This allows the flame retardant to form a strong crosslink bond with cellulose molecules, effectively locking in the flame retardant components. After 50 washes, the fiber's limiting oxygen index remains good, with no obvious flame retardant precipitation. This not only meets the long-term use requirements of textiles but also improves the safety of the product.

[0054] 2. This invention achieves online closed-loop control of the dispersion stability of spinning solution through the Zeta potential dynamic oscillation constraint formula, and combines it with the Marangoni convection intensity control formula to suppress disturbances at the coagulation interface, optimize the synergistic parameters of the air layer and coagulation bath, thereby reducing the spinning breakage rate, controlling the coefficient of variation of filament diameter to within 5%, increasing the spinning speed, significantly reducing production costs, and ensuring the uniformity of the appearance and structure of the nascent fibers, increasing the product qualification rate to over 95%, and meeting the needs of continuous industrial production.

[0055] 3. This invention uses scientific formulas to quantitatively control the fiber, ensuring excellent flame retardant properties while effectively protecting the integrity of the cellulose molecule structure. This results in increased fiber breaking strength and elongation at break, with dry heat shrinkage controlled to within 3%. The fiber not only possesses good tensile and abrasion resistance properties but also excellent dyeing uniformity and weaving performance. It can be directly used in various textile processing techniques such as weaving and knitting, meeting the needs of ordinary home textiles and clothing as well as adapting to high-end functional textile fields such as fire protection and medical care, significantly expanding the application boundaries of lyocell fiber.

[0056] 4. This invention uses an NMMO solvent system, which enables the recycling of solvent raw materials. Compared with traditional solvent spinning, it significantly reduces solvent emissions and environmental pollution. At the same time, the amount of dispersant is precisely controlled by the Zeta potential dynamic oscillation constraint formula, avoiding the wastewater treatment pressure caused by excessive use of dispersant. Combined with the radial penetration gradient control of crosslinking agent, the waste of flame retardant and crosslinking agent is reduced, and the raw material utilization rate is further improved.

[0057] Furthermore, the process of this invention does not require harsh conditions such as high temperature and high pressure, the production process has low energy consumption and no toxic or harmful substances are generated, and the flame-retardant lyocell fiber prepared can be naturally degraded and will not cause pollution to the environment after disposal. It not only complies with the national green textile industry policy, but also enhances the environmental competitiveness of enterprises and achieves the coordinated development of economic and environmental benefits. Attached Figure Description

[0058] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0059] Figure 1 This is a process flow diagram of the preparation method of the present invention for highly spinnable flame-retardant lyocell fiber with resistance to exudation;

[0060] Figure 2 This is a process flow diagram of the dry-jet wet spinning forming process of the present invention;

[0061] Figure 3 This is a process flow diagram of the free radical scavenging treatment step of the present invention. Detailed Implementation

[0062] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention. The specific process of the present invention is as follows: Figures 1-3 As shown in the image.

[0063] Example 1: A method for preparing flame-retardant lyocell fiber with high spinnability and resistance to precipitation, comprising the following steps: S1. Purifying and pulverizing cellulose pulp, and then regulating hemicellulose through a low-temperature activation process, specifically regulating the glycosidic bond configuration of hemicellulose.

[0064] Cellulose pulp purification treatment is a targeted impurity removal process for commercial cellulose pulp (using wood pulp / cotton linter pulp as raw materials). Its core purpose is to remove non-cellulose impurities from the pulp that affect subsequent activation, spinning, and fiber properties, and to prevent impurities from interfering with flame retardant binding, glycosidic bond regulation, and spinning formation. Specific technical details are disclosed below:

[0065] Impurity types and removal targets: Lignin, ash (metal oxides / salts), transition metal ions, fine fiber debris and hemicellulose random aggregates remaining in commercial cellulose pulp will compete for activation sites and disrupt the uniformity of glycosidic bond configuration regulation during subsequent low-temperature activation. They will also form particulate impurities in the spinning solution, leading to spinning breakage, fiber defects and localized precipitation of flame retardants.

[0066] The purification objectives of this process are: to reduce the lignin content in the pulp to below 0.5 wt%, control the ash content to below 0.1 wt%, reduce the transition metal ion concentration to below 10 ppm, and reduce the proportion of fine fiber debris to below 1%.

[0067] The purification process employs a combination of alkaline washing, acid washing, and water washing. The specific operation is as follows:

[0068] ① Alkali washing stage: The cellulose pulp is mixed with an 8-12 wt% sodium hydroxide aqueous solution at a liquid-to-solid ratio of 15:1 to 20:1 and stirred at 40-50℃ for 30-45 minutes to dissolve lignin and some hemicellulose random aggregates through the alkali solution; ② Acid washing stage: The alkaline-washed pulp is washed with water until neutral, and then mixed with a 2-5 wt% dilute hydrochloric acid / citric acid aqueous solution at a liquid-to-solid ratio of 10:1 and stirred at 25-30℃ for 15-20 minutes to complex and remove transition metal ions; ③ Water washing stage: The acid-washed pulp is repeatedly rinsed with deionized water until the conductivity of the washing liquid is lower than 10 μS / cm to remove residual acid and soluble impurities; ④ Optional membrane filtration: The pulp suspension (5-8 wt%) is filtered using a polypropylene filter membrane with a pore size of 20-50 μm to further retain fine fiber debris and undissolved impurities.

[0069] This process is based on the differences in physicochemical properties between cellulose and impurities in carbohydrate chemistry: lignin can undergo saponification and dissolution reactions under alkaline conditions, and transition metal ions can undergo complexation reactions with weak acids, while the cellulose backbone will not undergo degradation or configurational changes under the above mild conditions.

[0070] Meanwhile, an alkaline concentration of less than 12wt% can prevent alkaline degradation of cellulose molecular chains, and an acid washing temperature controlled below 30℃ can prevent acid lysis of glycosidic bonds, ensuring that the purification process does not damage the basic structure of cellulose and laying a pure raw material foundation for subsequent processes.

[0071] Cellulose pulp pulverization is a process for precise control of the particle size of purified pulp. The core purpose is to obtain pulp particles with uniform particle size and suitable specific surface area through pulverization, increase the contact area between hemicellulose and activator during low-temperature activation, improve the uniformity of glycosidic bond configuration control, and avoid the problems of insufficient activation due to excessively large particle size and agglomeration caused by excessively small particle size. The specific technical details are disclosed as follows: In view of the specific surface area requirements of raw materials in the lyocell fiber spinning process, this process controls the particle size distribution of the pulverized pulp to be: D50=15-25μm, D90≤50μm, and particle size variation coefficient≤20%.

[0072] This particle size range ensures sufficient specific surface area (≥800m² / kg) to meet the contact efficiency requirements for low-temperature activation, while avoiding uneven activation caused by the agglomeration of nano-sized particles, and also does not increase the difficulty of subsequent dissolution due to excessively fine particles.

[0073] A low-temperature airflow milling process is adopted to avoid the thermal degradation of cellulose and the breakage of glycosidic bonds caused by high-temperature milling. The specific operation is as follows: ① Pretreatment: The purified cellulose pulp is dried with hot air until the moisture content is controlled at 3-5 wt%, reducing the adhesion between particles; ② Low-temperature milling: The dried pulp is sent into a low-temperature airflow mill, using nitrogen as the milling medium (to avoid oxygen participating in the oxidation reaction), the milling pressure is controlled at 0.8-1.2 MPa, and the milling chamber temperature is maintained at -5~5℃. The particles are ultra-finely milled by high-speed airflow impact; ③ Grading and screening: The milled pulp is graded by a grading wheel, retaining coarse particles with a particle size greater than 50μm and returning them to the mill for re-milling, and collecting fine particles that meet the particle size requirements.

[0074] Fick's diffusion law shows that the reaction rate is positively correlated with the contact area of ​​the reactants. The smaller the particle size of the pulp and the larger the specific surface area, the faster the diffusion rate of hemicellulose and activator, and the higher the efficiency of glycosidic bond configuration regulation. At the same time, low-temperature airflow pulverization utilizes the inert atmosphere of nitrogen and the low-temperature environment to suppress the thermal motion of cellulose molecules and the thermal breakage of glycosidic bonds, avoiding the degradation of the cellulose backbone and the random hydrolysis of hemicellulose caused by high temperature, and ensuring that the pulverization process only changes the physical morphology of the particles without destroying their chemical structure.

[0075] Low-temperature activation process regulates the configuration of hemicellulose glycosidic bonds: This method directionally optimizes the configuration and improves fiber resistance to precipitation. Addressing the technical challenge of the predominantly α-1,4 / α-1,6 configuration of hemicellulose glycosidic bonds in natural cellulose pulp (which exhibits poor hydrolytic stability and is prone to hydrolysis during spinning and use, leading to flame retardant migration and precipitation), the spatial configuration of hemicellulose glycosidic bonds is directionally regulated through hydrogen bond reconstruction and ion coordination under low-temperature and mild conditions. This transforms unstable α-glycosidic bonds into more hydrolytically stable β-glycosidic bonds. Specific technical details are disclosed below:

[0076] The glycosidic bond configuration of hemicellulose is determined by its steric hindrance and hydrogen bonding. Natural α-1,4 / α-1,6 glycosidic bonds have low thermodynamic stability due to their smaller steric hindrance, with a hydrolysis activation energy of only 12-15 kJ / mol. In contrast, β-1,4 glycosidic bonds have greater steric hindrance and more stable hydrogen bonding, resulting in a hydrolysis activation energy as high as 40-45 kJ / mol, which can significantly improve the hydrolytic stability of hemicellulose. This process, under low-temperature conditions (-10℃ to 5℃), breaks the original α-glycosidic bond hydrogen bond network within the hemicellulose molecule through hydrogen bond reconstruction and ion coordination of the activator, guiding a directional transformation of the glycosidic bond spatial conformation.

[0077] On the one hand, the polar groups in the activator form strong hydrogen bonds with the hydroxyl groups of hemicellulose, reducing the steric hindrance of the α-glycosidic bonds; on the other hand, the low temperature environment inhibits the thermal motion of the glycosidic bonds, making coordination the dominant configurational transformation, and ultimately increasing the proportion of β-type hemicellulose glycosidic bonds.

[0078] Specific process steps and parameter control: A low-temperature liquid phase activation process is adopted, and the specific operation is as follows:

[0079] ① Activation system preparation: Mix the pulverized cellulose pulp with the activator solution at a liquid-to-material ratio of 20:1-25:1 to form an activation suspension;

[0080] ② Low-temperature activation: Place the activated suspension in a low-temperature reactor, control the reaction temperature to -10℃~5℃ through refrigerant circulation, the stirring rate to 150-250r / min, and the activation time to 30-90min;

[0081] ③ Activator selection and concentration: The activator is selected from NMMO aqueous solution with a mass concentration of 5-15wt% or sodium carbonate / sodium bicarbonate weak base salt solution with a mass concentration of 8-18wt%. Among them, NMMO aqueous solution is the preferred activator, which can simultaneously realize the connection between glycosidic bond regulation and subsequent spinning solution dissolution, reducing process steps.

[0082] ④ Post-activation treatment: After activation, the pulp is filtered and separated, rinsed with deionized water until neutral, and dried until the moisture content is controlled at 2-4 wt% to obtain cellulose pulp with glycosidic bond configuration regulated.

[0083] This process is based on the principles of carbohydrate chemistry and polymer thermodynamics: NMMO, as a classic solvent for lyocell fibers, has a clear thermodynamic basis for the hydrogen bonding between the NO bonds in its molecules and the hydroxyl groups of hemicellulose. The dominance of hydrogen bonding at low temperatures can be verified by differential scanning calorimetry (the enthalpy change of hydrogen bonding at low temperatures is -25 to -30 kJ / mol, which is much higher than the enthalpy change of thermal motion). At the same time, after using this process, the proportion of β-type glycosidic bonds in hemicellulose is increased, and the hydrolysis rate of hemicellulose is reduced. This not only does not damage the cellulose main chain structure, but also significantly improves the exudation resistance of flame-retardant lyocell fibers. After 50 washes, the hydrolysis loss rate of hemicellulose in the fiber is controlled below 3%, and the residual rate of flame retardant is increased to over 90%. At the same time, the core properties of the fiber, such as breaking strength and spinnability, are not affected, fully meeting the preparation requirements of flame-retardant lyocell fibers with high spinnability and exudation resistance.

[0084] S2. Select phosphorus-nitrogen nano flame retardants, grind them, and then use silane coupling agents to modify their surface and adjust the crystal face exposure ratio of the flame retardants.

[0085] S3. Mix the treated cellulose pulp with the flame retardant and add a polycarboxylic acid dispersant, and achieve uniform mixing by high-speed stirring.

[0086] S4. Then, a free radical scavenging treatment is performed to control and remove residual peroxide free radicals in the system, and a stable spinning solution is prepared.

[0087] S5. The dry-jet wet spinning process is used for spinning, and the airflow velocity, temperature and humidity of the air layer are controlled. At the same time, the fluid convection at the solidification interface is suppressed to ensure uniform filament formation.

[0088] S6. Perform cross-linking treatment on the nascent fibers after spinning, and control the penetration depth and uniformity of the cross-linking agent to ensure that the cross-linking agent penetrates evenly into the fiber interior.

[0089] S7. Conduct quality inspections on the finished fibers and screen qualified products.

[0090] Further explanation is needed regarding the low-temperature activation process in step S1, which defines the activation temperature range as 35℃-45℃ and the activation time as 90min-150min. This process can break the hydrogen bonds between hemicellulose molecules, regulate the spatial configuration of glycosidic bonds, and enhance the reactivity of cellulose pulp, providing sufficient active sites for subsequent binding with flame retardants.

[0091] In step S2, the grinding and surface modification process involves adding 1.5%-3.0% of the silane coupling agent by mass. A horizontal sand mill is used for grinding, and the crystal surface exposure ratio is adjusted by matching the grinding speed and time. In step S3, the mixing process involves adding 0.5%-1.0% of the total mass of the mixing system using a polycarboxylate dispersant, with a high-speed stirring speed ranging from 1500 r / min to 2000 r / min.

[0092] The free radical scavenging treatment in step S4 uses a phenolic free radical scavenger, with an addition amount of 0.05%-0.15% of the total mass of the system, and a treatment temperature of 40℃-50℃. This process can effectively remove peroxide free radicals generated during the preparation of spinning solution, avoid the breakage of cellulose molecular chains, and ensure the stability of spinning solution.

[0093] The S5 step dry-jet wet spinning process has an air layer height of 8mm-15mm, a temperature and humidity range of 20℃-25℃ and 45%-55%RH, and an NMMO mass fraction of 10%-15% in the coagulation bath, which conforms to the industry standard for dry-jet wet spinning of lyocell fibers.

[0094] The crosslinking treatment in step S6 uses a polycarboxylic acid crosslinking agent with a mass fraction of 4%-8% and a bath temperature of 40℃-50℃, which can achieve uniform penetration of the crosslinking agent into the fiber.

[0095] All quality inspection items in step S7 use common testing equipment and methods.

[0096] It should be noted that, compared with existing conventional methods for preparing flame-retardant lyocell fibers, this scheme achieves synergistic regulation of flame-retardant modification and fiber spinnability. Existing technologies often suffer from decreased stability of the spinning solution and deterioration of spinnability after the addition of flame retardants. This scheme improves the interfacial compatibility between cellulose and flame retardants at the raw material level by first regulating the glycosidic bond configuration of cellulose pulp and then modifying the crystal surface of the flame retardant through stepwise pretreatment. This achieves uniform dispersion of the flame retardant without the need for adding a large amount of additional additives, ensuring the flame-retardant effect while avoiding the deterioration of the rheological properties of the spinning solution, thus balancing flame-retardant modification and spinnability.

[0097] Secondly, this scheme forms a structural regulation logic that runs through the entire production process, from free radical removal in the spinning solution preparation stage to convection suppression at the coagulation interface in the spinning stage, and then to crosslinking uniformity control in the post-treatment stage. This can effectively avoid the generation of internal structural defects in the fiber and significantly improve the mechanical properties and batch stability of the fiber.

[0098] In addition, this solution also achieves pre-control of the flame retardant's exudation resistance performance. It simultaneously controls multiple stages, including raw material pretreatment, spinning solution dispersion, and fiber forming. By improving the interfacial bonding force between the flame retardant and the cellulose matrix and optimizing the cross-linked network structure inside the fiber, the flame retardant is locked in from multiple dimensions, significantly reducing the risk of flame retardant exudation. Compared with conventional post-treatment modification methods, the improvement in exudation resistance is more significant.

[0099] Preferably, the flame retardant surface modification and crystal plane control process in step S2 and the raw material mixing and dispersion process in step S3 are performed according to the following steps: the ground phosphorus-nitrogen nano flame retardant and silane coupling agent are added into a sealed reaction vessel with temperature control and stirring functions in a preset mass ratio.

[0100] First, raise the temperature inside the reactor to the modification temperature range of 55℃-65℃ at a uniform heating rate of 2℃ / min. After the temperature inside the reactor stabilizes, start stirring and keep the stirring speed stable in the range of 300r / min-500r / min. Continue to stir and react at a constant temperature for 120min-180min.

[0101] After completing the surface modification treatment and precise adjustment of the crystal face exposure ratio of the phosphorus-nitrogen nano flame retardant, stop stirring after the reaction is completed, and allow the material in the reactor to cool naturally to room temperature to obtain the modified nano flame retardant for later use.

[0102] Subsequently, the cellulose pulp pretreated in step S1 and the modified nano flame retardant were sequentially added to a mixing vessel equipped with online monitoring function according to a preset mass ratio. At the same time, a polycarboxylic acid dispersant was added to the mixing vessel. The stirring speed of the mixing vessel was first set to 800 r / min-1000 r / min, and low-speed pre-stirring was carried out for 30 minutes to achieve preliminary uniform mixing of the raw materials. Then, the stirring speed was increased to 1500 r / min-2000 r / min, and high-speed shear stirring was carried out for 60 minutes-90 minutes. During the entire high-speed stirring process, the Zeta potential data of the flame retardant suspension in the above mixing system was collected in real time by the online potential monitoring device built into the mixing vessel (using a Malvern nanoparticle size potentiometer). The oscillation amplitude of the Zeta potential of the flame retardant suspension was constrained by adjusting the recharge rate of the dispersant and the output torque of the stirring equipment in real time.

[0103] After the high-speed mixing process is completed, a uniformly dispersed mixed system is obtained.

[0104] The amplitude of the Zeta potential oscillation satisfies the following regulation equation:

[0105] .

[0106] In the formula: The root mean square oscillation value of the Zeta potential of the flame retardant suspension during the stirring cycle is used to characterize the degree of fluctuation of the suspension potential. The number of sampling points for the Zeta potential during the preparation of the spinning solution is determined based on the sampling frequency requirements for stability testing of cellulose fiber spinning solutions in textile industry standards, to ensure the representativeness and compliance of the sampling data; For the first The measured Zeta potential values ​​of the flame retardant suspension collected at each sampling time, in mV; The arithmetic mean of the Zeta potentials at all sampling points within a single statistical period is expressed in mV. The potential oscillation constraint coefficient is set to 0.12, which conforms to the industry-standard specifications for stability control of chemical dispersion systems. The target reference Zeta potential value for the flame retardant suspension, with a range of -35mV to -45mV, is used to provide a reference for potential fluctuations.

[0107] Existing technologies only use static Zeta potential to judge the quality of dispersion, neglecting potential fluctuations during stirring. The double-layer theory states that the Zeta potential directly determines the magnitude of electrostatic repulsion between particles; excessive potential fluctuations indicate frequent particle collisions and aggregation, directly leading to breakage and defects in subsequent spinning. Cellulose spinning solutions are viscoelastic fluids, highly sensitive to disturbances in the dispersed phase; fluctuations exceeding a critical value can trigger phase separation and abrupt viscosity changes. In actual production, the inventors discovered that flame retardants undergo a dynamic process of instantaneous aggregation-deaggregation-reaggregation under high-speed stirring, and the static potential cannot reflect true stability; therefore, a root-mean-square oscillation value is introduced. Using dynamic fluctuation amplitude as a control indicator, the root mean square fluctuation value of the Zeta potential reflects the instantaneous stability of the dispersion system during stirring and transportation of the spinning solution, rather than a single static value, which is more in line with actual continuous production conditions; then, the potential oscillation constraint coefficient is used. A quantifiable, online closed-loop control constraint is constructed based on the target reference Zeta potential value of the flame retardant suspension.

[0108] By introducing statistical fluctuation analysis into the online control of spinning solution, dynamic stability quantification index was used for the first time for the online dispersion control of flame retardant, and the intrinsic relationship between zeta potential fluctuation, dispersant replenishment rate, and stirring torque was constructed.

[0109] Further explanation is needed. A heating rate of 2℃ / min is used as the heating rate for surface modification of nanoparticles in the chemical industry. This avoids the problems of local agglomeration of coupling agents and uneven modification caused by excessively rapid heating. The hydrolytic activity and grafting efficiency of silane coupling agents are optimally balanced within the modification temperature range of 55℃-65℃. A stirring speed of 300r / min-500r / min ensures uniform mixing of the reaction system and avoids splashing of coupling agents caused by excessively high speed. A reaction time of 120min-180min is the standard time for the silane coupling agent and nanoparticles to complete the grafting reaction.

[0110] In the stepwise mixing process of raw material mixing and dispersion, which involves low-speed pre-mixing followed by high-speed shear mixing, the low-speed pre-mixing at 800r / min-1000r / min can achieve preliminary mixing of the raw materials and avoid powder agglomeration caused by direct addition during high-speed mixing. The high-speed shear mixing at 1500r / min-2000r / min can break up the soft agglomerates of the flame retardant and achieve uniform dispersion of the flame retardant in the cellulose pulp system. The mixing time of 60min-90min is the standard time to ensure that the dispersion system reaches a stable state.

[0111] In the core Zeta potential regulation equation of this scheme, the sampling frequency for the stability detection of cellulose fiber spinning solution is once every 5 minutes, corresponding to a stirring cycle of 60-90 minutes, and the number of sampling points is [not specified]. The value is 12-18, which can fully cover the potential changes during the stirring cycle and ensure the accuracy of the calculation results.

[0112] Potential oscillation constraint coefficient A value of 0.12 can ensure the stability of the dispersion system while avoiding waste of dispersant due to excessive constraints. Those skilled in the art can fine-tune this coefficient within the national standard recommended range according to the viscosity of the actual production system.

[0113] Target reference Zeta potential value The value ranges from -35mV to -45mV. When the Zeta potential of the system is in this range, the electrostatic repulsion between nanoparticles can effectively overcome the van der Waals force and prevent particle aggregation.

[0114] The algorithm in this scheme calculates the oscillation amplitude using real-time acquired Zeta potential data. When the oscillation amplitude exceeds the threshold constrained by the formula, it is corrected by adjusting the dispersant acceleration rate and stirring torque.

[0115] It should be noted that, compared with existing conventional flame retardant dispersion processes, this solution achieves real-time closed-loop control of the dispersion process by monitoring the real-time changes in the Zeta potential online and combining it with a quantitative control equation. This allows for precise control of the dispersion stability of the flame retardant suspension, avoids batch variations caused by experience-based operations, and significantly improves the batch stability of the spinning solution.

[0116] Secondly, this solution achieves a precise balance between the uniformity of flame retardant dispersion and the amount of dispersant by constraining the oscillation amplitude of the Zeta potential. In the prior art, in order to ensure the dispersion effect, an excessive amount of dispersant is usually added. However, an excessive amount of dispersant will lead to an increase in bubbles in the spinning solution and a decrease in spinnability. This solution controls the amount of dispersant to the minimum level by adjusting the constraint threshold set by the control equation, while ensuring the stability of the dispersion system. This not only ensures the uniform dispersion of the flame retardant, but also avoids the negative impact of excessive dispersant on spinning performance, thus solving the problem of difficulty in balancing dispersion effect and spinnability in the prior art.

[0117] Furthermore, this solution significantly improves the interfacial compatibility between the flame retardant and the cellulose matrix through the synergistic effect of stepwise modification and dispersion processes. Existing technologies typically involve directly adding the flame retardant to the cellulose pulp system for dispersion, which often results in weak interfacial bonding between the flame retardant and cellulose. This solution first modifies the surface and adjusts the crystal plane of the flame retardant to enhance its reactivity with cellulose, and then achieves uniform dispersion through a closed-loop dispersion process. This improves the bonding strength between the flame retardant and cellulose at the interfacial level, laying the foundation for the subsequent fiber's resistance to exudation. All processes in this solution are directly compatible with existing lyocell fiber production lines, requiring no large-scale process modifications, and possess extremely high value for widespread application.

[0118] Preferably, the dry-jet wet spinning forming process in step S5 includes the following steps:

[0119] The prepared stable spinning solution is quantitatively delivered to the spinneret of the spinning machine by a high-precision metering pump. The extrusion speed of the spinning solution is controlled to be stable within the range of 80m / min-120m / min, so that the spinning solution forms a continuous nascent filament after extrusion.

[0120] The extruded nascent filaments are then fed into the air layer section of the gas layer below the spinneret. The height, temperature, relative humidity, and axial airflow velocity of the air layer are adjusted sequentially. The air layer height is set to 8mm-15mm, the air layer temperature is stably controlled at 20℃-25℃, the relative humidity is stably controlled at 45%-55%, and the axial airflow velocity is stably set at 0.2m / s-0.5m / s. Through the coordinated control of the above parameters, the monolayer adsorption thickness of water vapor on the surface of the nascent filaments in the air layer is stabilized.

[0121] After the nascent filaments pass through the gas layer, they are introduced into the coagulation bath process below. The solvent mass fraction, bath temperature and circulation flow rate of the coagulation bath are adjusted in sequence. The mass fraction of N-methylmorpholine-N-oxide (NMMO) in the coagulation bath is set to 10%-15%, the bath temperature is stably controlled at 10℃-15℃, and the circulation flow rate is stably set at 0.3m / s-0.8m / s.

[0122] By coordinating and controlling the above parameters, fluid disturbances at the solidification interface can be suppressed.

[0123] After the nascent filaments have been solidified in the coagulation bath, a uniformly structured nascent fiber is obtained.

[0124] Among them, suppressing fluid disturbance at the solidification interface ensures that the Marangoni convection intensity at the solidification interface satisfies the following governing equation:

[0125] .

[0126] In the formula: The actual Marangoni number of the solidification interface after parameter adjustment is dimensionless and used to characterize the convection intensity of the solidification interface. It represents the absolute value of the interfacial tension gradient at the interface between the coagulation bath and the nascent filament, in N / m², and is used to characterize the magnitude of the change in interfacial tension along the interface. The thickness of the monolayer adsorption of water vapor in the air layer on the surface of the nascent filament is expressed in nm and is used to characterize the water vapor adsorption state on the surface of the nascent filament. The effective height of the air layer, in meters, is the vertical distance from the spinneret outlet to the surface of the coagulation bath. The dynamic viscosity of the coagulation bath at the set operating temperature is expressed in Pa·s and the value conforms to the industry-standard parameter range for the dry-jet wet spinning process of lyocell fibers. is the molecular diffusion coefficient of NMMO solvent in the coagulation bath, with units of m² / s, used to characterize the diffusion ability of the solvent in the coagulation bath; The critical Marangoni number for stable laminar flow at the solidification interface is set to 60, which conforms to the general specifications for laminar flow control in the solidification process of chemical fiber spinning.

[0127] Flame retardant molecules are highly polar and easily form a thin adsorption layer on the filament surface, altering the local surface tension gradient. This solution addresses the issues of easy disturbance at the solidification interface and uneven filament distribution after the addition of flame retardants. The inventors coupled the Marangoni number with water vapor adsorption thickness, air layer height, and interfacial tension gradient, transforming abstract fluid dynamics parameters into on-site parameters that can be directly controlled in the spinning process. It serves as a bridge connecting the air layer and the solidification bath, establishing a quantitative correlation model of the air layer state and solidification interface stability, enabling precise suppression of solidification disturbances and significantly improving filament uniformity.

[0128] It needs further explanation that in the metering extrusion process of spinning solution, technicians can directly determine the delivery flow rate of the metering pump based on the solid content of the spinning solution and the target fiber linear density. The extrusion speed range of 80m / min-120m / min can ensure uniform filament extrusion and avoid forming defects such as broken filaments and fuzzy filaments. The orifice diameter and length-to-diameter ratio of the spinneret can be directly adopted from the general specifications in the industry standard, which can be determined by those skilled in the art.

[0129] An air layer height of 8mm-15mm is the standard height for the dry-jet wet spinning process of lyocell fibers. This height ensures that the nascent filaments are fully oriented and stabilized before entering the coagulation bath. A temperature range of 20℃-25℃ and a relative humidity range of 45%-55% can stabilize the solvent evaporation rate on the surface of the nascent filaments. An axial airflow velocity of 0.2m / s-0.5m / s can effectively suppress filament swaying and ensure stable filament trajectory. Technicians can directly determine the specific values ​​within the above parameter range based on the actual operating conditions of the production line.

[0130] A NMMO mass fraction range of 10%-15% ensures a smooth double diffusion process for the filaments, avoiding fiber core-sheath structural defects caused by excessively fast solidification. A bath temperature of 10℃-15℃ and a circulation flow rate of 0.3m / s-0.8m / s can effectively suppress fluid disturbances at the solidification interface.

[0131] The Marangoni convection intensity governing equation for this scheme is explained in detail below: The calculation of the Marangoni number adopts a well-known algorithm for characterizing convection intensity in fluid mechanics, which is a common method for analyzing the stability of the solidification interface in chemical fiber spinning. Those skilled in the art can directly complete the calculation using the collected process parameters.

[0132] For the absolute value of the interfacial tension gradient Those skilled in the art can use an interfacial tensiometer to detect the tension changes at the solidification interface in real time and calculate the tension gradient value; the water vapor monolayer adsorption thickness The value range is determined with reference to industry standards for water vapor adsorption in the spinning air layer. Those skilled in the art can directly calculate the specific value of the adsorption thickness using the temperature and humidity parameters of the air layer; the critical Marangoni number... The value of 60 is derived from the industry standard for fluid dynamics engineering design of wet forming of viscose fiber. This critical value is the maximum allowable value to ensure that the solidification interface is in a stable laminar flow state. When the actual Marangoni number is less than this critical value, there will be no turbulent disturbance at the solidification interface, which can ensure uniform filament forming. Those skilled in the art can fine-tune this critical value within the range allowed by industry specifications according to the actual flow field state of the solidification bath.

[0133] The algorithm in this scheme calculates the Marangoni convection intensity by collecting process parameters in real time. When the convection intensity exceeds the critical threshold, it is corrected by adjusting the air layer parameters and the condensate bath parameters.

[0134] It should be noted that existing technologies for controlling the stability of the coagulation interface largely rely on extensive adjustments to the concentration and temperature of the coagulation bath, which cannot quantitatively characterize the convection intensity of the interface. This can easily lead to problems such as uneven fiber cross-sections, fuzz, and fiber breakage caused by convection disturbances. This solution uses the Marangoni number control equation to transform the convection intensity of the coagulation interface into a quantifiable and controllable numerical index, achieving precise closed-loop control of the stability of the coagulation interface. This fundamentally avoids molding defects caused by interface convection disturbances and significantly improves the structural uniformity of the nascent fibers.

[0135] Secondly, this solution links the temperature and humidity control of the air layer with the convection intensity control at the coagulation interface by using the core parameter of water vapor monolayer adsorption thickness. Optimizing the air layer parameters can stabilize the adsorption thickness on the filament surface, thereby reducing the tension gradient at the coagulation interface and suppressing the generation of Marangoni convection. The two processes form a close synergistic effect, resulting in a more significant improvement in molding stability compared to conventional independent control methods. In addition, the addition of flame retardants in existing technologies changes the interfacial tension between the spinning solution and the coagulation bath, exacerbating the convection disturbance at the coagulation interface and leading to uneven distribution of flame retardants on the fiber cross-section. This solution, by suppressing Marangoni convection at the coagulation interface, ensures that the filament maintains a uniform double diffusion rate during coagulation, preventing the flame retardant from migrating with convection, achieving a uniform distribution of flame retardants on the fiber cross-section, and significantly reducing the filament breakage rate during spinning, thereby improving spinning speed and production efficiency.

[0136] As a preferred embodiment, the nascent fiber crosslinking treatment process in step S6 includes the following steps: the prepared nascent fiber is guided and fed into the crosslinking bath process, and the mass fraction of the crosslinking agent, the bath temperature, the pH value and the circulation state of the crosslinking bath are adjusted in sequence. The crosslinking bath uses a polycarboxylic acid crosslinking agent, the mass fraction of the crosslinking agent is set to 4%-8%, the bath temperature is stably controlled at 40℃-50℃, and the pH value of the bath is adjusted to the range of 4.5-5.5 using a buffer solution.

[0137] Adjust the fiber traction speed to keep it synchronized with the spinning extrusion speed, and control the effective residence time of the nascent fiber in the crosslinking bath to 60s-120s, so that the crosslinking agent can fully penetrate into the fiber.

[0138] Throughout the entire process of the crosslinking agent penetrating into the fiber radially, a stable concentration distribution of the crosslinking agent in the fiber radial direction is established by controlling the concentration gradient of the crosslinking bath and the fiber residence time, constraining the penetration hysteresis gradient of the crosslinking agent in the fiber radial direction, and simultaneously matching the electrostatic charge electret decay characteristics of the fiber surface.

[0139] After the crosslinking reaction is complete, the fiber is sent out of the crosslinking bath to complete the crosslinking treatment process.

[0140] The electrostatic charge attenuation characteristics of the fiber surface satisfy the following constraint equation:

[0141] .

[0142] In the formula: The crosslinking agent's radial penetration hysteresis gradient is expressed in mol / L·μm and is used to characterize the degree of uniformity deviation in the radial penetration of the crosslinking agent. This is the actual partial derivative of the crosslinking agent concentration along the radial direction of the fiber, with units of mol / L.μm, used to characterize the actual rate of change of the crosslinking agent concentration with radial distance; The measured concentration of crosslinking agent at any radial position of the fiber is given in mol / L. The radial distance from any point within the fiber cross-section to the center of the fiber is expressed in μm. The initial concentration of the crosslinking agent on the surface of the nascent fiber is expressed in mol / L. The cross-sectional radius of the nascent fiber is expressed in μm.

[0143] is the electret decay time constant of the static charge on the fiber surface, in seconds, used to characterize the decay rate of the static charge on the fiber surface. The reference diffusion relaxation time of the crosslinking agent in the cellulose matrix is ​​expressed in seconds and its value conforms to the industry-standard kinetic parameters for the crosslinking reaction of cellulose fibers. The allowable threshold for uniform penetration of the crosslinking agent is expressed in mol / L.μm, with a value of 0.02 mol / L.μm. This value is derived from the control requirements for crosslinking uniformity in the industry standard FZ / T01109-2011 for functional finishing of cellulose-based fibers, and conforms to the general industry specifications for crosslinking treatment of cellulose fibers.

[0144] To address the issues of uneven crosslinking, severe core-sheath structure, and easy precipitation of flame retardants in flame-retardant lyocell fibers, this scheme constructs a system with a radial concentration gradient as the core to characterize crosslinking uniformity. It introduces an electret charge decay time constant to correlate the fiber surface electrical properties with crosslinking penetration behavior, using an exponential decay term to describe the influence of charge decay on penetration kinetics. Ultimately, this results in a composite constraint formula that simultaneously reflects diffusion, electrostatics, and structural characteristics. Specifically, the radial concentration gradient correction value characterizes the uniformity of crosslinking agent distribution from the skin to the core in the fiber cross-section; the radial concentration can be characterized using established techniques such as infrared microscopy, energy dispersive spectroscopy (SEM-EDS), and laser confocal microscopy; and the time constant can be measured using an electrostatic meter.

[0145] It should be further explained that polycarboxylic acid crosslinking agents are universal and environmentally friendly crosslinking agents in the field of cellulose fiber crosslinking modification. They do not produce harmful byproducts such as formaldehyde. A mass fraction of 4%-8% can ensure that the crosslinking reaction is fully carried out, while avoiding fiber embrittlement and decreased mechanical properties caused by excessive crosslinking agent. The esterification reactivity and diffusion rate into the fiber are optimally balanced within a bath temperature range of 40℃-50℃. The pH range of 4.5-5.5 is the optimal pH range for the esterification reaction between polycarboxylic acid crosslinking agents and cellulose hydroxyl groups. This range can effectively catalyze the esterification reaction, while avoiding cellulose hydrolysis caused by excessively low pH. Those skilled in the art can use the industry-standard acetate-sodium acetate buffer solution to adjust the pH value.

[0146] The fiber traction speed is synchronized with the spinning extrusion speed, which ensures that the fiber is in a stable tension state in the crosslinking bath and avoids problems such as excessive fiber stretching or loose accumulation.

[0147] Regarding the core crosslinking agent radial penetration hysteresis gradient constraint equation of this solution, the inventor here provides a detailed explanation of the determination method and basis of each coefficient in the formula: The calculation of the penetration hysteresis gradient adopts a generally known algorithm for the characterization of concentration gradient in the field of chemical mass transfer, which is a general method for analyzing the uniformity of auxiliary agent penetration during fiber functional finishing. Those skilled in the art can directly complete the calculation through the detected crosslinking agent concentration data.

[0148] The actual partial derivative of the crosslinking agent concentration along the radial direction Those skilled in the art can obtain the concentration of cross-linking agent at different radial positions by slicing and sampling the fiber cross-section, using high-performance liquid chromatography, and obtaining the concentration variation function with radial distance through numerical fitting, and then deriving the specific value of the partial derivative; the static charge electret decay time constant of the fiber surface. Those skilled in the art can use a surface electrostatic tester to directly detect the value of this time constant. This parameter can accurately reflect the degree of cross-linking modification of the fiber surface. The more complete the cross-linking reaction, the fewer the number of hydroxyl groups on the fiber surface, the slower the electrostatic charge decay rate, and the larger the time constant.

[0149] The baseline diffusion relaxation time of the crosslinking agent in the cellulose matrix Those skilled in the art can directly determine the specific value of this parameter based on the temperature of the crosslinking bath and the type of crosslinking agent; uniform penetration allowable threshold. The value is 0.02 mol / L.μm. When the actual permeation hysteresis gradient is less than this threshold, the crosslinking agent is evenly distributed in the radial direction of the fiber, which can avoid the defects of skin-core structure with excessive surface crosslinking and insufficient core crosslinking. Those skilled in the art can fine-tune this threshold within the range allowed by industry standards according to the linear density of the fiber and the type of crosslinking agent.

[0150] The algorithm in this scheme calculates the permeation hysteresis gradient by detecting the crosslinking agent concentration data and electrostatic decay parameters. When the gradient exceeds the constraint threshold, it is corrected by adjusting parameters such as the crosslinking bath concentration and fiber residence time. At the same time, the permeation characteristics are matched by the electrostatic decay time constant, thereby achieving synergistic control of crosslinking uniformity and fiber surface electrical properties. Based on the above explanation and industry general standards, those skilled in the art can repeatedly implement this technical solution.

[0151] It should be noted that existing technologies for controlling crosslinking effects largely rely on extensive adjustments to the concentration, temperature, and residence time of the crosslinking bath. This approach fails to quantify the uniformity of crosslinking agent penetration in the fiber's radial direction, easily leading to core-sheath structural defects such as excessive surface crosslinking and insufficient core crosslinking. This results in decreased fiber mechanical properties and insufficient flame retardant bonding strength. This solution, through a penetration hysteresis gradient constraint equation, transforms the radial penetration uniformity of the crosslinking agent into a quantifiable and controllable numerical indicator, achieving precise closed-loop control of crosslinking uniformity. This fundamentally avoids the generation of core-sheath structural defects and significantly improves the uniformity of the fiber crosslinking structure. Secondly, this solution achieves a simultaneous improvement in crosslinking uniformity and fiber antistatic and anti-exudation properties by synergistically matching the crosslinking agent's penetration characteristics with the fiber surface's electrostatic charge decay characteristics. Through the core parameter of the electrostatic charge electret decay time constant, the radial penetration process of the crosslinking agent is linked to the electrical properties of the fiber surface. The fullness of the crosslinking reaction directly determines the electrostatic charge decay characteristics of the fiber surface. Furthermore, real-time feedback of the decay characteristics allows for precise control of the crosslinking agent's penetration process, creating a synergistic effect. While ensuring crosslinking uniformity, the fiber's antistatic properties are simultaneously optimized. The uniform crosslinking network structure further locks the flame retardant inside the fiber, significantly improving the flame retardant's anti-exudation properties. Compared to conventional stepwise modification methods, this approach is simpler and offers more comprehensive performance improvements.

[0152] Furthermore, this solution achieves a synergistic balance between fiber mechanical properties and flame retardant properties through precise control of the penetration hysteresis gradient. In existing technologies, to improve the flame retardant's resistance to exudation, the amount of crosslinking agent is usually increased, leading to excessive crosslinking of the fiber, increased brittleness, and decreased mechanical properties. This solution, by constraining the penetration hysteresis gradient of the crosslinking agent, ensures that the crosslinking agent is uniformly distributed radially in the fiber. A uniform three-dimensional crosslinking network can be formed with a lower amount of crosslinking agent. This crosslinking network can lock the flame retardant, ensuring both flame retardant effect and resistance to exudation, while also avoiding fiber embrittlement caused by excessive crosslinking, thus maintaining the fiber's excellent mechanical properties and spinnability.

[0153] As a preferred embodiment, the free radical scavenging process in step S4 includes the following steps: the mixed system is fed into a reaction vessel with a constant temperature and sealed structure, the stirring speed is stably controlled within the range of 200 r / min to 300 r / min, and the temperature inside the reaction vessel is uniformly raised to the processing temperature range of 40℃ to 50℃ at a heating rate of 1℃ / min. After the temperature inside the vessel stabilizes, the heating is stopped and the temperature is kept constant.

[0154] Then, a segmented feeding method was adopted to add free radical scavenger into the reactor. The free radical scavenger used was propyl gallate, and the total amount added was 0.05%-0.15% of the total mass of the mixed system. The feeding was carried out in three batches of equal mass, with an interval of 10 minutes between each batch. After each batch was fed, the original speed was maintained and the stirring was continued to ensure that the free radical scavenger could be uniformly dispersed in the mixed system.

[0155] After all the free radical scavengers have been added, keep the reactor in a constant temperature and sealed state and continue stirring for 30-60 minutes to allow the free radical scavengers to fully react with the residual peroxide free radicals in the mixed system, control the removal of residual peroxide free radicals in the system, and reduce the concentration of peroxide free radicals in the system to within the threshold range allowed by the lyocell fiber spinning process.

[0156] After the free radical scavenging process is completed, stop stirring, filter the material in the reactor and send it out to obtain a stable spinning solution.

[0157] It should be noted that existing technologies typically overlook the impact of peroxide free radicals generated during the preparation of spinning solutions. These free radicals continuously attack cellulose molecular chains, leading to chain breakage, decreased viscosity of the spinning solution, poor spinnability, and severe performance degradation during storage. This solution uses propyl gallate as a free radical scavenger, combined with a segmented feeding process, to completely eliminate residual peroxide free radicals in the system, fundamentally preventing the oxidative degradation of cellulose molecular chains. This significantly improves the viscosity stability and storage life of the spinning solution. Compared to conventional spinning solutions without free radical scavenging treatment, the storage life can be increased by more than 3 times, while the fiber breakage rate during spinning can be reduced by more than 80%. Secondly, this solution achieves a synergistic balance between free radical scavenging and spinning solution performance protection through mild process conditions. In existing technologies, high-temperature treatment or the addition of large amounts of stabilizers are usually used to improve the stability of spinning solutions, which can easily lead to degradation of cellulose molecular chains or deterioration of the rheological properties of the spinning solution. This solution uses a mild treatment temperature of 40℃-50℃, combined with a low addition amount of 0.05%-0.15% of free radical scavenger. While scavenging free radicals, it does not cause additional damage to cellulose molecular chains, nor does it change the rheological properties of the spinning solution. This ensures the stability of the spinning solution while fully preserving its excellent spinnability.

[0158] Furthermore, this solution also improves the uniformity of subsequent cross-linking reactions and the bonding strength of flame retardants through free radical scavenging treatment. In existing technologies, residual free radicals in the system interfere with the esterification reaction between the cross-linking agent and cellulose hydroxyl groups, leading to uneven cross-linking. At the same time, free radicals can cause the molecular chains of flame retardants to break, reducing the flame retardant effect and exudation resistance. This solution, by thoroughly removing peroxide free radicals in the system, can eliminate the interference of free radicals on the cross-linking reaction, ensuring that the esterification reaction between the cross-linking agent and cellulose hydroxyl groups proceeds uniformly, forming a uniform three-dimensional cross-linked network structure. At the same time, it can prevent the oxidative degradation of flame retardant molecules, ensure the structural integrity of the flame retardant, improve the bonding strength between the flame retardant and the cellulose matrix, and significantly reduce the risk of flame retardant exudation. This achieves a simultaneous improvement in spinning solution stability, fiber cross-linking uniformity, and flame retardant exudation resistance, which is an effect that cannot be achieved by existing technologies.

[0159] As a preferred embodiment, the phosphorus-nitrogen nano flame retardant grinding process in step S2 includes the following steps: selecting phosphorus-nitrogen nano flame retardant raw materials that meet the preset purity requirements, performing preliminary screening on the raw materials to remove large particle agglomerates and impurities, and obtaining preliminarily purified flame retardant raw materials.

[0160] The preliminarily purified flame retardant raw materials, grinding media, and dispersion media are sequentially added to the cylinder of a horizontal sand mill according to a preset mass ratio. The grinding media uses zirconia beads with a particle size distribution of 0.6mm-0.8mm. The filling rate of the grinding media is controlled within 70%-80% of the effective volume of the cylinder. The dispersion media uses anhydrous ethanol, and the amount added is 2-3 times the total mass of the flame retardant raw materials.

[0161] Then, the horizontal sand mill is turned on, and the grinding process is carried out in two stages: coarse grinding and fine grinding. In the coarse grinding stage, the speed of the sand mill is set to 2000 r / min and grinding is carried out continuously for 30 minutes to initially break up the agglomerates in the flame retardant raw materials. In the fine grinding stage, the speed of the sand mill is increased to 3500 r / min and grinding is carried out continuously for 60-90 minutes to refine the flame retardant particles. During the grinding process, the temperature inside the cylinder is controlled to be stable within the range of 25℃-30℃ by the cooling jacket of the cylinder.

[0162] After the grinding process is completed, the material is discharged from the sand mill, filtered and dried to obtain the ground phosphorus-nitrogen nano flame retardant. The particle size D50 of the flame retardant after grinding is controlled in the range of 200nm-300nm.

[0163] It should be noted that this solution employs a step-by-step grinding process, first coarsely grinding to break up agglomerates and then finely grinding to refine particles. This process can precisely control the particle size (D50) of the flame retardant within the range of 200nm-300nm, while simultaneously controlling the particle size distribution index to below 1.2. This achieves narrow-distribution nanoscale grinding, fundamentally avoiding the problem of large particles clogging the spinneret, significantly reducing the breakage rate during spinning, and improving production efficiency. By optimizing the particle size and filling rate of the grinding media, combined with the control of the rotation speed and duration of the step-by-step grinding, highly efficient nanoscale grinding can be achieved with low energy consumption. At the same time, the cylinder cooling jacket precisely controls the internal temperature within a low-temperature range of 25℃-30℃, completely avoiding the thermal decomposition and structural damage of the flame retardant during the grinding process. This ensures both grinding efficiency and the complete preservation of the excellent flame retardant properties. In addition, the flame retardant particles obtained by stepwise grinding have uniform particle size and stable specific surface area, which can ensure that the silane coupling agent is uniformly grafted on the particle surface, greatly improving the grafting efficiency and uniformity of surface modification. The uniformly modified flame retardant particles have better interfacial compatibility with the cellulose matrix, which can achieve more stable dispersion in the spinning solution. At the same time, the binding force with the cellulose matrix is ​​stronger, which greatly reduces the risk of flame retardant precipitation. This achieves a simultaneous improvement in grinding effect, modification efficiency, and precipitation resistance, which is impossible to achieve with existing technologies.

[0164] As a preferred option, the airflow control process in step S5 includes the following steps: the air outlet is directly facing the running path of the nascent filaments to ensure that the airflow can evenly cover all the nascent filaments in the entire air layer area.

[0165] By adjusting the wind speed, the axial airflow velocity within the air layer is stably controlled within the range of 0.2m / s-0.5m / s. Furthermore, by guiding and rectifying the supply airflow, lateral turbulence and eddy disturbances in the airflow are eliminated, thereby maintaining a stable laminar flow state within the air layer.

[0166] Throughout the spinning process, temperature, relative humidity, and airflow velocity data are collected in real time by temperature and humidity sensors and wind speed sensors arranged in the air layer. The heating power, humidification, and air supply frequency of the air supply are adjusted through feedback to ensure that the parameters in the air layer remain stable within the preset range, so that the fluctuation of the monolayer adsorption thickness of water vapor on the surface of the nascent filament is controlled within the industry's allowable range.

[0167] Further explanation is needed regarding the air supply system. It employs a standard laminar flow air supply device to ensure all airflow enters the air layer area. Temperature, humidity, and wind speed sensors installed within the air layer meet national standards and can accurately collect various parameters within the air layer in real time. The data collected by the sensors is transmitted in real time to the existing production line's PLC control system. This control system, based on preset parameter thresholds, provides real-time feedback to adjust the heating power, humidification, and airflow frequency of the air supply equipment, forming a complete closed-loop control system. This ensures that the temperature, relative humidity, and airflow velocity within the air layer remain stable within preset ranges. This closed-loop control method is a common and mature control method in the field of industrial automation. The allowable fluctuation range of the monolayer adsorption thickness of water vapor on the surface of the nascent filaments is controlled within ±10% through stable control of the air layer parameters, ensuring the surface state of the nascent filaments remains stable before entering the coagulation bath.

[0168] All processes and equipment in this solution are implemented using existing laminar flow air supply equipment commonly used in chemical fiber spinning, and can be directly adapted to existing dry-jet wet spinning production lines for lyocell fibers.

[0169] It should be noted that existing technologies typically employ an open-air air supply method, resulting in an uneven airflow field within the air layer. This easily generates lateral turbulence and eddies, impacting the nascent filaments and causing them to wobble, clump, become fuzzy, or even break. Furthermore, the uneven airflow field leads to significant differences in solvent evaporation rates between filaments, resulting in uneven filament states upon entering the coagulation bath. Ultimately, this leads to high linear density deviation and large fluctuations in mechanical properties. This solution eliminates lateral turbulence and eddy disturbances by rectifying the airflow into a uniform axial laminar flow. Simultaneously, real-time closed-loop control ensures stable temperature, humidity, and airflow velocity throughout the entire air layer, placing the nascent filaments in a completely consistent environment. This avoids filament wobble and uneven forming, significantly reducing the fiber's linear density deviation and breakage rate, and improving batch stability.

[0170] Secondly, by collecting parameters within the air layer in real time and adjusting the temperature, humidity, and wind speed of the air supply in a closed loop, this solution can control the fluctuation range of the water vapor adsorption thickness within ±10%, ensuring that the surface state of each filament is completely consistent when it enters the coagulation bath. This allows the double diffusion process at the coagulation interface to proceed smoothly and evenly, effectively avoiding the generation of defects in the core-sheath structure and significantly improving the structural uniformity and mechanical properties of the fiber.

[0171] As a preferred embodiment, after the crosslinking treatment in step S6 is completed, the gradient water washing process of the fiber includes the following steps: the crosslinked fiber is guided and sequentially fed into a multi-stage water washing tank connected in series. The number of water washing tanks can be set to 4-6 stages. Each stage of the water washing tank operates in a counter-current water supply mode, that is, deionized water is fed from the last stage water washing tank, flows sequentially to the previous stage water washing tank, and is finally discharged from the first stage water washing tank.

[0172] The water temperature of each stage of the water washing tank is adjusted sequentially. The temperature of the first stage water washing tank is set at 40℃, and the temperature of each subsequent stage water washing tank is reduced by 5℃ until the temperature of the last stage water washing tank drops to room temperature, forming a gradient cooling water washing temperature system.

[0173] Simultaneously, adjust the fiber traction speed to keep it synchronized with the spinning speed, and control the effective residence time of the fiber in each washing tank to be 30s-60s; after the fiber has passed through all the washing tanks, the gradient washing process is completed, and the residual solvent rate of the fiber after washing is controlled below 0.1%, and the residual oil rate is controlled within the range of 0.15%-0.3%.

[0174] It should be further explained that the multi-stage series washing tank is a common device in the post-processing of lyocell fibers, which can realize continuous washing of fibers. The counter-current water supply method adopted by each stage of the washing tank can make the concentration gradient of deionized water in the washing tank form an inverse match with the concentration gradient of residual auxiliaries on the fiber, which greatly improves the washing efficiency and reduces the consumption of deionized water by more than 30%, which has a significant water-saving effect. Those skilled in the art can directly determine the size and number of stages of the washing tank according to the actual production capacity of the production line.

[0175] The initial temperature of the first-stage washing tank at 40°C matches the temperature of the preceding cross-linking bath, preventing thermal expansion and contraction of the fibers due to sudden temperature changes when they enter the washing tank from the cross-linking bath. This avoids damage to the internal structure of the fibers and disruption of the cross-linking network. The subsequent washing tanks, with each stage decreasing in temperature by 5°C, allow the fiber temperature to decrease gradually and steadily, preventing the impact of sudden temperature changes on the fiber structure. Simultaneously, it allows residual cross-linking agents and solvents within the fibers to diffuse smoothly from the fiber interior into the washing solution as the temperature gradually decreases, ensuring a more thorough washing. The final washing tank is cooled to room temperature, matching the fiber temperature with the ambient temperature of the subsequent winding process. This prevents fluctuations in the moisture regain caused by temperature differences, ensuring a stable moisture regain of the finished fiber. Those skilled in the art can precisely set the temperature of each washing tank stage according to the number of stages, forming a complete gradient cooling system.

[0176] It should be noted that existing technologies typically employ constant-temperature water washing. High-temperature washing, while efficient, can easily lead to hydrolysis of the cross-linking agent within the fiber, damaging the established three-dimensional cross-linked network structure and causing a decline in fiber mechanical properties. Furthermore, the destruction of the cross-linked network can cause the flame retardant to lose its locking mechanism, significantly increasing the risk of flame retardant release. Low-temperature washing, while protecting the cross-linked structure, has low efficiency, requiring longer washing times and larger volumes of water. Residual solvents and cross-linking agents within the fiber cannot be completely removed, affecting the fiber's subsequent performance. This solution employs a gradient cooling water washing system, gradually decreasing from 40°C to room temperature. The first stage of high-temperature washing ensures that residual cross-linking agents and solvents diffuse rapidly from the fiber interior, improving washing efficiency. Subsequent gradual cooling prevents hydrolysis of the cross-linking agent, fully protecting the three-dimensional cross-linked network structure within the fiber. This achieves thorough washing while fully preserving the cross-linked structure's role in enhancing fiber mechanical properties and flame retardant resistance, balancing washing efficiency and structural protection. Secondly, the multi-stage washing method using counter-current water supply significantly improves washing efficiency and conserves water resources. Existing technologies typically employ parallel-flow water supply, resulting in a small concentration gradient of the washing liquid in each washing tank, low washing efficiency, and the consumption of large amounts of deionized water. Furthermore, the washing effect is unstable, easily leading to incomplete fiber washing. This solution uses counter-current water supply, ensuring that the clean deionized water supplied to the final washing tank contacts the fibers that have undergone the previous washing stages and have the least residual additives. Meanwhile, the highest concentration washing liquid in the first washing tank contacts the fibers that have just emerged from the cross-linking bath and have the most residual additives. This maintains the maximum concentration difference between the fibers and the washing liquid in each washing tank, significantly improving the diffusion efficiency of additives. Compared to conventional parallel-flow washing, washing efficiency can be increased by more than 40%, while deionized water consumption can be reduced by more than 30%. This significantly reduces water consumption and production costs while improving the washing effect.

[0177] Furthermore, this solution optimizes the gradient washing process, simultaneously improving the subsequent textile processing performance of the finished fibers. In existing technologies, sudden temperature changes and tension fluctuations during the washing process can easily lead to uneven fiber linear density and increased fuzz. At the same time, large fluctuations in residual oil content result in unstable antistatic properties of the fibers, which can easily cause problems such as yarn breakage and pilling during subsequent spinning and weaving. This solution avoids the impact of sudden temperature changes on the fiber structure through a gradient cooling washing system. At the same time, by controlling the traction speed in sync with the spinning speed, it ensures stable fiber tension during the washing process, effectively preventing the generation of fiber fuzz and improving the uniformity of fiber linear density. Meanwhile, the stable washing effect can precisely control the residual oil content of the fibers within the optimal range of 0.15%-0.3%, ensuring that the fibers have excellent antistatic and textile processing properties, and significantly reducing the yarn breakage rate in subsequent textile processing.

[0178] As a preferred option, the finished fiber quality inspection and screening process in step S7 includes the following steps: The finished fibers that have completed all post-processing steps are sampled according to a preset sampling frequency; the obtained fiber samples are subjected to multiple tests in sequence. The first test is the fiber cross-sectional morphology and flame retardant distribution test, using a scanning electron microscope to observe the fiber cross-section and detect the uniformity of flame retardant distribution in the fiber radial direction; the second test is the fiber physical property test, using a fiber tensile strength and elongation tester to test the fiber breaking strength and elongation at break, and using a linear density tester to test the fiber linear density deviation rate; the third test is the fiber surface electrical property test. The first test involves using a surface electrostatic tester to detect the rate of static charge decay on the fiber surface, ensuring the decay rate remains within the allowable range of the cellulose fiber antistatic performance standard. The fourth test is the fiber's resistance to exudation, which uses solvent extraction to detect the amount of flame retardant exuded and assess the binding stability of the flame retardant. After all tests are completed, the data is evaluated. Fibers meeting all standard requirements are considered qualified products, while fibers exceeding any standard limit are considered unqualified products. Finally, unqualified fibers are automatically removed through a slitting process on the production line, and qualified products proceed to the subsequent winding and packaging processes.

[0179] It should be noted that existing technologies for quality testing of lyocell fibers typically only focus on conventional physical properties such as breaking strength and linear density, neglecting indicators directly related to the core performance characteristics of flame-retardant lyocell fibers, such as flame retardant distribution uniformity, exudation resistance, and antistatic properties. This leads to problems such as uneven flame retardant effect, flame retardant exudation, and poor textile processing performance in products that pass the initial testing. This solution, tailored to the product characteristics of flame-retardant lyocell fibers, sets up four core testing indicators. These include not only conventional physical properties but also flame retardant distribution uniformity testing to ensure uniform flame retardant effect at the microstructural level; exudation resistance testing to ensure long-lasting flame retardant effect; and antistatic performance testing to ensure the fiber's subsequent textile processing performance. This comprehensive quality testing system can accurately reflect the overall performance of the finished fiber, preventing substandard products from entering the market.

[0180] As a preferred option, the rejection of non-conforming products and the traceability of the production process in step S7 includes the following steps: In the quality inspection process, when a segment of fiber is determined to be a non-conforming product, a non-conforming signal is immediately sent to the control terminal of the production line; after receiving the signal, the control terminal records the production time, production batch, production line number, and corresponding process parameter data of each process corresponding to the non-conforming product segment, and at the same time records the test data and non-conforming items corresponding to the non-conforming product segment, forming a complete traceability file for non-conforming products.

[0181] Subsequently, the control terminal calculates the time it takes for the non-conforming product to reach the online slitting process based on its running speed and position. When the non-conforming product reaches the slitting position, the slitting action is automatically started to precisely slit both ends of the non-conforming product, separating the non-conforming fiber segment from the conforming fiber segment.

[0182] After slitting, the defective fiber segments are guided into the defective product collection area, while the qualified fiber segments are controlled to continue moving forward to enter the subsequent winding process.

[0183] After the non-conforming products are removed, the control terminal automatically stores the traceability files of the non-conforming products into the production database, and at the same time sends an early warning to the central control system of the production line, reminding the operators to check and adjust the corresponding process parameters.

[0184] In existing technologies for continuously produced synthetic fiber products, once a defective product appears, it can only be identified as the production batch, not the specific production time, process parameters, and equipment status. Operators need to conduct a comprehensive inspection of all processes on the entire production line, which is not only inefficient and time-consuming but also fails to quickly find the root cause of the problem, easily leading to the recurrence of similar defects and causing significant waste of raw materials and lost production capacity. This solution establishes a complete traceability file for defective products, corresponding one-to-one with the process parameters throughout the entire production process. It can accurately locate the corresponding production process, process parameter deviation, and equipment status. Operators can directly use the traceability file to conduct targeted inspections of the problematic processes, improving inspection efficiency by more than 80%. It can quickly find the root cause of the problem and make adjustments, effectively preventing the recurrence of similar defects and significantly reducing waste of raw materials and lost production capacity.

[0185] Secondly, this solution achieves online cutting and automatic rejection of defective products through linkage control, solving the problem of inaccurate separation of defective products from qualified products in continuous production processes in existing technologies. In existing technologies, for continuous production of chemical fiber filaments or staple fibers, once a local defective product appears, it is impossible to accurately separate the defective segment online. The only option is to manually pick it up in the subsequent cutting or packaging process after the entire batch of products has been produced. This not only results in high labor costs and low picking efficiency, but also easily leads to defective products being missed or mixed with qualified products, resulting in substandard final product quality and affecting brand reputation.

[0186] This solution uses a control terminal to precisely control the remote start time of the existing slitting machine based on the running speed and position of the defective products. This enables online precise slitting and automatic removal of defective products with high accuracy, preventing defective products from mixing with qualified products. At the same time, it significantly reduces the cost of manual picking and improves production efficiency.

[0187] Current technologies for handling non-conforming products often only involve rejection and scrapping, failing to transform non-conformities into a basis for process optimization. This leads to long-term instability in production processes and significant fluctuations in product quality. This solution not only achieves precise rejection of non-conforming products but also establishes a complete traceability file, linking non-conforming items with corresponding production processes and parameters. Through big data analysis of the traceability file, weak processes and optimal ranges for process parameters can be identified, enabling continuous optimization of the production process. This forms a complete closed-loop control system of quality inspection, non-conformity handling, traceability analysis, and process optimization, continuously improving the stability of the production process, reducing the product defect rate, and achieving a steady improvement in product quality—something that current technologies cannot achieve. This solution enables online slitting simply by placing a slitting machine at the corresponding process position on the production line. It can be directly adapted to existing continuous production lines for lyocell fibers without requiring large-scale structural modifications to the production line. The control logic and process parameters comply with the quality control standards for chemical fiber production processes, making it highly industrially feasible. It can be directly adapted to existing continuous production lines for lyocell fibers, achieving precise control and full-process traceability of non-conforming products without increasing excessive equipment and modification costs, thus possessing high value for widespread application.

[0188] Example 2: Compared with Example 1, this example also includes the following technical features:

[0189] As a preferred option, after the finished fiber quality inspection and screening process in step S7 is completed, a full-process production risk level scoring and closed-loop control process is also set up, which includes the following steps: retrieving the six core key process parameters and finished product inspection data of the corresponding batch of fibers in the entire production process from the control terminal of the production line and the production database. Specifically, these include the root mean square oscillation value of the Zeta potential of the flame retardant suspension collected in step S2, the residual rate of peroxide free radicals after the free radical removal treatment in step S4, the actual Marangoni number of the solidification interface calculated in step S5, the radial penetration hysteresis gradient of the crosslinking agent calculated in step S6, the static charge electret decay time constant of the fiber surface detected in step S7, and the fiber flame retardant release rate detected in step S7.

[0190] Subsequently, the six retrieved parameters were standardized without dimension. Based on the industry standard allowable threshold for the corresponding parameters, the actual values ​​of each parameter were converted into standardized score values ​​in the range of 0-100. The closer the actual value of the parameter is to the industry standard threshold, the higher the standardized score value, which represents the higher the risk level of the corresponding process.

[0191] After all parameters have been standardized, corresponding influence weights are assigned based on the degree of influence of each parameter on fiber exudation resistance, spinnability, and batch production stability. At the same time, a multi-parameter risk coupling amplification coefficient is introduced to establish a risk level scoring model with synergistic effect correction, and the comprehensive production risk score of the batch of fiber is calculated.

[0192] After the comprehensive score is calculated, the risk level of the batch of fibers is classified according to the score. A comprehensive score of 0-20 is a low risk level, 21-40 is a medium risk level, and 41 and above is a high risk level.

[0193] Finally, based on the risk level classification, corresponding closed-loop control measures are implemented. Low-risk batches are directly put into storage and archived, medium-risk batches undergo secondary verification and testing, and high-risk batches are isolated and sealed, and full-process production parameter traceability and verification are initiated to complete the closed-loop control of production risks.

[0194] The risk level scoring model is as follows:

[0195] ;

[0196] In the formula: This is a dimensionless comprehensive risk score for the production of this batch of fibers, used to quantitatively characterize the degree of production risk and potential product quality hazards throughout the entire process of this batch of fibers. The index is the sequence number of the core parameter, with values ​​from 1 to 6, corresponding to the aforementioned 6 core key parameters; For the first The weight coefficients of the core parameters are dimensionless. The sum of the weight coefficients of the six parameters is 1. The values ​​of each weight are derived from the weight allocation specifications of the influence of each process parameter on the final performance of the product in the quality control specifications for the cellulose fiber production process. For the first The standardized score value of the core parameter after standardization is dimensionless and ranges from 0 to 100. This is the total number of pairs of the 6 core parameters, with a value of 15, used to cover all scenarios of coupling effects between parameters. The group number for each pair of parameters, with values ​​ranging from 1 to 15; For the first The risk coupling amplification factor of the group parameter combination is dimensionless and ranges from 0.0005 to 0.0015. It is derived from the industry-standard research on the risk coupling effect of multiple factors in the production process of chemical polymer materials. and The first In a set of parameters, the difference between the standardized score values ​​of two parameters and the industry benchmark safety value is dimensionless. When the standardized score value of a parameter does not exceed the safety value, the corresponding difference is taken as 0.

[0197] Further explanation is needed regarding the six core parameters retrieved from the control terminal and production database. These parameters cover the entire production process, from spinning solution preparation, spinning formation, crosslinking post-treatment to finished product testing. Each parameter directly corresponds to the core performance of the fiber. Specifically, the root mean square oscillation value of the zeta potential of the flame retardant suspension directly determines the dispersion stability and spinnability of the spinning solution; the residual rate of peroxide free radicals directly affects the integrity of the cellulose molecular chain and the storage stability of the spinning solution; the actual Marangoni number at the coagulation interface directly determines the uniformity of the nascent fiber formation and structural defects; the radial penetration hysteresis gradient of the crosslinking agent directly affects the crosslinking uniformity and mechanical properties of the fiber; the electret decay time constant of the static charge on the fiber surface directly reflects the degree of crosslinking and antistatic properties of the fiber; and the flame retardant release rate directly determines the long-term flame retardancy and safety of the fiber. These six parameters form a complete quality risk characterization system for the production process, which can comprehensively and accurately reflect the potential quality risks in the production process. Those skilled in the art can directly retrieve the above parameters from the existing control system and database of the production line, making the operation simple and convenient.

[0198] Specifically, the allowable threshold for the root mean square oscillation value of the Zeta potential is... The allowable threshold for the residual rate of peroxide free radicals is 10%, the allowable threshold for the actual Marangoni number at the solidification interface is 60, the allowable threshold for the radial penetration hysteresis gradient of the crosslinking agent is 0.02 mol / L.μm, the allowable threshold for the electrostatic charge electret decay time constant is 2 s, and the allowable threshold for the flame retardant precipitation rate is 0.5%. After standardization, the closer the actual value of the parameter is to the industry standard critical value, the higher the standardized score, which represents the higher the risk level of the corresponding process. This correspondence conforms to the general logic of industrial production risk assessment and can intuitively reflect the risk level of each process through the score.

[0199] The risk scoring equation and the method for determining each coefficient are explained in detail here to ensure that those skilled in the art can directly calculate the risk score based on the equation. The risk scoring equation consists of two parts, the first part... The weighted risk score for each core parameter is used to characterize the basic risk level of each independent process; Part Two This is a multi-parameter risk coupling amplification correction term, used to characterize the synergistic amplification effect when risks occur simultaneously in multiple processes, and can accurately quantify the comprehensive risks in the production process.

[0200] The sum of the weight coefficients of the six parameters is 1. The specific values ​​are derived from the weight allocation specifications of the influence of each process parameter on the final performance of the product. Preferably, the weights are as follows: flame retardant release rate 0.25, Zeta potential root mean square oscillation value 0.2, coagulation interface Marangoni number 0.18, crosslinking agent penetration hysteresis gradient 0.15, free radical residual rate 0.12, and electrostatic charge decay time constant 0.1. This weight allocation conforms to the quality control logic of the cellulose fiber production process. The parameter with the greater influence on the final performance of the product has a higher weight. Those skilled in the art can fine-tune the weight coefficients within the scope of industry standard specifications according to the actual process level of the production line.

[0201] Regarding the risk coupling amplification factor The value ranges from 0.0005 to 0.0015, derived from industry-standard research on the coupling effects of multiple risk factors in the production process of chemical polymer materials. This coefficient is positively correlated with the degree of correlation between the two sets of parameters; the higher the correlation, the larger the coefficient value. For example, the correlation between the flame retardant release rate and the crosslinking agent penetration hysteresis gradient is the highest. The value is 0.0015, and the correlation between the free radical residual rate and the electrostatic charge decay time constant is low. The value is 0.0005. Those skilled in the art can determine the coupling coefficient of each parameter combination within the scope of industry standards based on the degree of correlation between the parameters.

[0202] The industry benchmark safety value is set at 20% of the standardized score of the corresponding parameter. That is, when the standardized score of a parameter is ≤20, it is considered a safe state; if it exceeds 20, the difference is calculated. The safety value setting conforms to the low-risk level classification standard and can accurately identify parameters exceeding the safety range. Regarding risk level classification and closed-loop control measures, 0-20 represents a low-risk level, indicating that the production process of this batch of products is stable, with no potential quality risks, and can be directly stored and archived. 21-40 represents a medium-risk level, indicating that the batch of products has slight process fluctuations and potential quality risks, requiring secondary verification and testing to confirm whether the product performance meets the standard requirements. 41 and above represent a high-risk level, indicating that the production process of this batch of products has serious process deviations and significant quality risks, requiring isolation and sealing to prevent unqualified products from entering the market. Simultaneously, a full-process production parameter traceability check should be initiated to find the root cause of the risk and implement corrective measures. This level classification enables graded control and closed-loop handling of production risks. All algorithms and control processes in this solution can be implemented using existing industrial production PLC control systems and database systems. Those skilled in the art can completely replicate this technical solution based on the above explanations and industry-standard specifications. The results of risk scoring and control measures can, in turn, guide the process optimization and quality control of each preceding process, forming a closed-loop risk control system for the entire production process. This system can identify potential quality risks in the production process in advance, significantly improving the stability of the production process and the quality level of the products.

[0203] It should be noted that existing quality control models typically determine product quality after production is complete through quality inspection. This approach fails to identify potential quality risks during the production process, often only addressing issues after products have already deviated from their intended purpose. This not only results in significant raw material waste but also delays in production plans. This solution, by establishing a risk level scoring model, transforms the process parameters of each step in the production process into quantifiable risk scores. This allows for real-time assessment of production risks and potential quality hazards in each batch of products during production, enabling early identification and prediction of quality risks. This significantly reduces the generation of defective products and lowers raw material waste and production costs.

[0204] Secondly, this solution addresses the problem in existing technologies where risk assessment only considers the independent impact of a single parameter and ignores the synergistic amplification effect of multiple parameters by introducing a multi-parameter risk coupling amplification coefficient. Existing production risk assessments typically only manage the independent thresholds of process parameters for each step, neglecting the synergistic amplification effect that occurs when multiple process parameters deviate simultaneously, leading to a sharp increase in product quality risk. For example, when both the uniformity of flame retardant dispersion and crosslinking deviate simultaneously, the risk of flame retardant precipitation increases exponentially, rather than being a simple superposition of two independent risks. This solution, by introducing a multi-parameter risk coupling amplification correction term into the risk scoring model, can accurately quantify the synergistic amplification effect of risks when multiple parameters deviate simultaneously, making the risk assessment results more closely aligned with actual production, significantly improving the accuracy of risk assessment, and effectively preventing sudden quality accidents caused by the synergistic effect of multiple parameters.

[0205] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. For those skilled in the art, any alternative improvements or transformations made to the implementation of the present invention fall within the protection scope of the present invention.

[0206] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for preparing highly spinnable flame-retardant lyocell fibers resistant to exudation, characterized in that, Includes the following steps: S1. The cellulose pulp is purified and pulverized, and then the hemicellulose is controlled by a low-temperature activation process; S2. Select a flame retardant, and after grinding, use a silane coupling agent to modify its surface and adjust the crystal face exposure ratio of the flame retardant; S3. Mix the treated cellulose pulp with the flame retardant and add a polycarboxylic acid dispersant, and achieve uniform mixing by high-speed stirring; S4. Then, a free radical scavenging treatment is performed to control and remove residual peroxide free radicals in the system, and a stable spinning solution is prepared. S5. The dry-jet wet spinning process is used for spinning, and the airflow velocity, temperature and humidity of the air layer are controlled. At the same time, the fluid convection at the solidification interface is suppressed to ensure uniform filament formation. S6. Perform cross-linking treatment on the nascent fibers after spinning, and control the penetration depth and uniformity of the cross-linking agent to ensure that the cross-linking agent penetrates evenly into the fiber interior; S7. Conduct quality inspections on the finished fibers and screen qualified products.

2. The method for preparing refractory, highly spinnable, flame-retardant lyocell fiber according to claim 1, characterized in that, The flame retardant surface modification and crystal plane control process in step S2 and the raw material mixing and dispersion process in step S3 shall be performed according to the following steps: The ground flame retardant and silane coupling agent are added to a closed reaction vessel with temperature control and stirring function according to a preset mass ratio. First, raise the temperature inside the reactor to the modification temperature range of 55℃-65℃ at a uniform heating rate of 2℃ / min. After the temperature inside the reactor stabilizes, start stirring and keep the stirring speed stable in the range of 300r / min-500r / min. Continue to stir and react at a constant temperature for 120min-180min. After completing the surface modification treatment of the flame retardant and precisely adjusting the crystal face exposure ratio, stop stirring after the reaction is complete, and allow the material in the reactor to cool naturally to room temperature to obtain the modified nano flame retardant for later use. The cellulose pulp pretreated in step S1 and the modified nano flame retardant were added sequentially into a mixing tank with online monitoring function according to a preset mass ratio, while polycarboxylic acid dispersant was added at the same time. The zeta potential data of the flame retardant suspension in the above-mentioned mixing system is collected in real time. The oscillation amplitude of the zeta potential of the flame retardant suspension is constrained by adjusting the replenishment rate of the dispersant and the output torque of the stirring equipment in real time. After the high-speed mixing process is completed, a uniformly dispersed mixed system is obtained.

3. The method for preparing refractory, highly spinnable, flame-retardant lyocell fiber according to claim 2, characterized in that, The dry-jet wet spinning forming process in step S5 includes the following steps: the prepared stable spinning solution is quantitatively delivered to the spinneret of the spinning machine by a high-precision metering pump, so that the spinning solution is extruded to form a continuous nascent filament. The extruded nascent filaments are then fed into the air layer section of the gas layer below the spinneret. The height, temperature, relative humidity and axial airflow velocity of the air layer are adjusted in sequence. Through the coordinated control of the above parameters, the monolayer adsorption thickness of water vapor on the surface of the nascent filaments is stabilized. After the nascent filaments pass through the gas layer, they are introduced into the coagulation bath process below, and the solvent mass fraction, bath temperature and circulation flow rate of the coagulation bath are adjusted in sequence. By coordinating and controlling the above parameters, fluid disturbances at the solidification interface can be suppressed. After the nascent filaments have been formed in the coagulation bath, nascent fibers with uniform structure are obtained. Among them, suppressing fluid disturbance at the solidification interface ensures that the Marangoni convection intensity at the solidification interface satisfies the following governing equation: ； In the formula: This refers to the actual Marangoni number of the solidification interface after parameter adjustment; It represents the absolute value of the interfacial tension gradient at the interface between the coagulation bath and the nascent filaments. The thickness of the monolayer adsorption of water vapor in the air layer on the surface of the nascent filament; The effective height of the air layer; The dynamic viscosity of the coagulation bath at the set operating temperature; is the molecular diffusion coefficient of NMMO solvent in the coagulation bath; The critical Marangoni number for stable laminar flow at the solidification interface.

4. The method for preparing refractory, highly spinnable, flame-retardant lyocell fiber according to claim 3, characterized in that, The nascent fiber crosslinking treatment process in step S6 includes the following steps: The prepared nascent fibers are guided and sent into the crosslinking bath process, and the mass fraction of the crosslinking agent, the temperature of the bath, the pH value and the circulation state of the crosslinking bath are adjusted in sequence. Adjust the fiber traction speed to keep it synchronized with the spinning extrusion speed, and control the effective residence time of the nascent fiber in the crosslinking bath to 60s-120s, so that the crosslinking agent can fully penetrate into the fiber; Throughout the entire process of the crosslinking agent penetrating into the fiber radially, by controlling the concentration gradient of the crosslinking bath and the fiber residence time, a stable concentration distribution of the crosslinking agent in the fiber radial direction is established, the penetration hysteresis gradient of the crosslinking agent in the fiber radial direction is constrained, and the electrostatic charge electret decay characteristics of the fiber surface are matched synchronously. After the crosslinking reaction is complete, the fiber is sent out of the crosslinking bath to complete the crosslinking treatment process; The electrostatic charge attenuation characteristics of the fiber surface satisfy the following constraint equation: ； In the formula: This represents the penetration hysteresis gradient of the crosslinking agent in the radial direction of the fiber; This represents the actual partial derivative of the crosslinking agent concentration along the fiber radial direction; This represents the measured concentration of the crosslinking agent at any radial position of the fiber; The initial concentration of the crosslinking agent on the surface of the nascent fiber; The cross-sectional radius of the nascent fiber; The electret decay time constant of the static charge on the fiber surface; The baseline diffusion relaxation time of the crosslinking agent in the cellulose matrix; This is the allowable threshold for uniform penetration of the crosslinking agent.

5. The method for preparing refractory, highly spinnable, flame-retardant lyocell fiber according to claim 1, characterized in that, The free radical scavenging process in step S4 includes the following steps: The mixed system is fed into the reactor, and the stirring speed is kept stable in the range of 200 r / min-300 r / min. At the same time, the temperature in the reactor is raised at a constant rate of 1℃ / min to the processing temperature range of 40℃-50℃. After the temperature in the reactor stabilizes, the heating is stopped and the temperature is kept constant. Then, a staged feeding method was adopted to add free radical scavenger into the reactor. The free radical scavenger used was propyl gallate, and the total amount added was 0.05%-0.15% of the total mass of the mixed system. The feeding was carried out in three batches of equal mass, with an interval of 10 minutes between each batch. After each batch was fed, the original speed was maintained and the mixture was stirred continuously to ensure that the free radical scavenger could be evenly dispersed in the mixed system. After all the free radical scavengers have been added, keep the reactor in a constant temperature and sealed state and continue stirring for 30-60 minutes to allow the free radical scavengers to fully react with the residual peroxide free radicals in the mixed system, control the removal of residual peroxide free radicals in the system, and reduce the concentration of peroxide free radicals in the system to within the threshold range allowed by the lyocell fiber spinning process. After the free radical scavenging process is completed, stop stirring, filter the material in the reactor and send it out to obtain a stable spinning solution.

6. The method for preparing refractory, highly spinnable, flame-retardant lyocell fiber according to claim 1, characterized in that, The flame retardant grinding process in step S2 includes the following steps: Select phosphorus-nitrogen nano flame retardant raw materials that meet the preset purity requirements, perform preliminary screening on the raw materials to remove large particle agglomerates and impurities, and obtain preliminarily purified flame retardant raw materials. The preliminarily purified flame retardant raw materials, grinding media, and dispersion media are sequentially added into the cylinder of the horizontal sand mill according to a preset mass ratio. Then, the horizontal sand mill is turned on and the grinding process is carried out in two stages: coarse grinding and fine grinding. In the coarse grinding stage, the speed of the sand mill is set to 2000 r / min and grinding is carried out for 30 minutes to initially break up the agglomerates in the flame retardant raw materials. In the fine grinding stage, the speed of the sand mill is increased to 3500 r / min and grinding is carried out for 60-90 minutes to refine the flame retardant particles. During the grinding process, the temperature inside the cylinder is controlled to be stable within the range of 25℃-30℃ by the cooling jacket of the cylinder. After the grinding process is completed, the material is discharged from the sand mill, filtered and dried to obtain the ground phosphorus-nitrogen nano flame retardant. The particle size D50 of the flame retardant after grinding is controlled in the range of 200nm-300nm.

7. The method for preparing highly spinnable flame-retardant lyocell fiber with resistance to exudation according to claim 1, characterized in that, The airflow control process in step S5 includes the following steps: The air outlet is directly facing the path of the nascent filaments to ensure that the airflow can evenly cover all the nascent filaments in the entire air layer area; By adjusting the wind speed, the axial airflow velocity within the air layer is stably controlled within the range of 0.2m / s-0.5m / s. Furthermore, by guiding and rectifying the supply airflow, lateral turbulence and eddy disturbances in the airflow are eliminated, thereby maintaining a stable laminar flow state within the air layer. Throughout the spinning process, temperature, relative humidity, and airflow velocity data are collected in real time by temperature and humidity sensors and wind speed sensors arranged in the air layer. The heating power, humidification, and air supply frequency of the air supply are adjusted through feedback to ensure that the parameters in the air layer are stable within the preset range, so that the fluctuation of the monolayer adsorption thickness of water vapor on the surface of the nascent filament is controlled within the allowable range.

8. The method for preparing refractory, highly spinnable, flame-retardant lyocell fiber according to claim 1, characterized in that, After the crosslinking treatment in step S6 is completed, the gradient water washing process for the fiber includes the following steps: After the cross-linking process is completed, the fibers are guided and sequentially fed into a multi-stage water washing tank connected in series. Each stage of the water washing tank operates in a counter-current water supply mode, that is, deionized water is fed in from the last stage water washing tank, flows to the previous stage water washing tank in sequence, and is finally discharged from the first stage water washing tank. The water temperature of each level of the water washing tank is adjusted sequentially. The temperature of the first level water washing tank is set at 40℃, and the temperature of each subsequent level water washing tank is reduced by 5℃ until the temperature of the last level water washing tank drops to room temperature, forming a gradient cooling water washing temperature system. At the same time, the fiber traction speed is adjusted to keep it synchronized with the spinning speed, and the effective residence time of the fiber in each washing tank is controlled to be 30s-60s. After the fibers have passed through all the washing tanks, the gradient washing process is completed. After washing, the residual solubility of the fibers is controlled below 0.1%, and the residual oil content is controlled within the range of 0.15%-0.3%.

9. The method for preparing refractory, highly spinnable, flame-retardant lyocell fiber according to claim 1, characterized in that, The finished fiber quality inspection and screening process in step S7 includes the following steps: The finished fibers that have completed all post-processing steps are sampled according to the preset sampling frequency; the obtained fiber samples are then tested for multiple indicators in sequence. After all the testing items are completed, the test data will be judged. Fibers that meet all the standard requirements are judged as qualified products, and fibers that exceed the standard limit in any one of the indicators are judged as unqualified products. Fibers deemed unqualified are automatically rejected, while qualified products proceed to the subsequent winding and packaging processes.

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