Method for preparing long-acting antibacterial fabric of metal ion intercalation type polyamide fiber

Abstract

This invention relates to the field of polyamide fiber preparation and discloses a method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber, comprising: preparing a homogeneous precursor fluid with a hydrogen bond network; feeding polyamide melt into a melt modification device, injecting the precursor fluid in the homogenization section to form a mixed melt; inputting specific shear work into the mixed melt by adjusting the shear rate to induce macromolecular chain extension to expose amide groups, causing the precursor fluid phase to decompose and release metal ions, forming metal complexation sites; and locking the metal complexation sites in the amorphous region of the fiber through melt spinning and cooling stretching to produce antibacterial fiber and weave it into a fabric. This invention achieves atomic-level dispersion of functional components through an in-situ coordination mechanism, eliminates component pressure drop fluctuations caused by inorganic phase agglomeration, preserves the intrinsic mechanical strength of the fiber, and achieves simultaneous antibacterial performance and fiber lifespan.

Description

Technical Field

[0001] This invention relates to a method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fibers, belonging to the field of polyamide fiber preparation technology. Background Technology

[0002] The current mainstream technology adopts a melt spinning process that physically blends inorganic metal powder with polyamide chips. It utilizes the broad-spectrum antibacterial properties of metal ions to endow the fabric with biological protective functions. Since the polyamide macromolecular chain has strong polarity, the matrix melt should theoretically exhibit stable rheological behavior to support industrial continuous spinning. The melt extrusion process of high-performance nylon fibers is usually carried out in a high-temperature environment of 260°C to 290°C. There is a natural thermodynamic incompatibility between inorganic metal particles and the strong polar polyamide matrix. When the melt undergoes laminar shear in the screw and flows to the filter component, due to the lack of interfacial chemical bonding, this physical repulsion causes large-scale secondary agglomeration of functional components.

[0003] To alleviate agglomeration, conventional methods involve adding low-molecular-weight organic dispersants or coupling agents. However, under the high-temperature shear field within the extruder, these additives undergo thermal degradation and release small-molecule volatiles. This not only fails to eliminate agglomeration but also causes abnormal fluctuations in the apparent viscosity of the melt, leading to a rapid increase in pressure drop across the filter screen of the spinning assembly. This results in frequent production line shutdowns for cleaning, and the hard clusters cause melt fracture and filament drift when passing through the spinneret. Besides the physical limitations in hardware structure and additive addition, the control strategies and component construction methods in the preparation process also have shortcomings. For example, the disclosed… Chinese invention patent application CN115323522A discloses an antibacterial polyamide fiber and its preparation method. The method involves constructing a multi-component system by acid etching of tourmaline in combination with guanidine antibacterial agents and metal ions. However, the technical solution relies on the physical loading of 300nm to 700nm rigid carrier particles. The carrier and the polyamide matrix are bonded and anchored by physical adsorption and surface protective film. Under the action of high-intensity shear energy field during melt spinning, stress concentration occurs at the heterogeneous interface, which induces carrier detachment or agglomeration. This type of rigid filler physically breaks the continuous crystalline network of polyamide, resulting in the deterioration of the intrinsic mechanical strength of the fiber.

[0004] Therefore, how to establish chemical bonds between metal ions and macromolecular chains during polyamide melt spinning, achieve atomic-level dispersion of functional components, and maintain melt rheological stability has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems in the background art, the technical solution of the present invention is as follows: A method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fibers, comprising the following steps: Step S1: Caprolactam is mixed with a metal salt at 80°C to 110°C to form a homogeneous precursor fluid with a hydrogen bond network. Step S2: The polyamide chips are fed into the melting section of the melt modification equipment and heated to obtain polyamide melt; Step S3: In the homogenization section of the melt modification equipment, the homogeneous precursor fluid is injected into the polyamide melt through the injection unit at a volume flow ratio of 0.01 to 0.05 between the homogeneous precursor fluid and the polyamide melt to form a mixed melt. Step S4: Adjust the screw speed of the melt modification equipment in the homogenization section, input specific shear work into the mixed melt, so that the polyamide macromolecular chains in the polyamide melt extend to expose the amide groups, and cause phase separation of the homogeneous precursor fluid to release metal ions. The metal ions combine with the amide groups to form metal complexation sites. Step S5: The mixed melt containing metal complexation sites is extruded through a spinneret to obtain a primary melt stream. The primary melt stream is sent into a cooling and forming zone. By adjusting the cooling air temperature and stretching tension, a non-isothermal crystallization gradient is generated, so that the chain segments containing metal complexation sites are locked in the amorphous region network of polyamide fibers, thus obtaining long-lasting antibacterial polyamide fibers. Step S6: The long-lasting antibacterial polyamide fiber is woven into an antibacterial fabric.

[0006] Preferably, in step S4, the screw speed is adjusted so that the input specific shear work is greater than the activation energy threshold for the in-situ coordination reaction between metal ions and amide groups; the metal complexation sites are molecularly dispersed in the polyamide melt, and the tensile strength retention rate of the long-lasting antibacterial polyamide fiber is not less than 98% of that of pure polyamide fiber of the same specification; in step S5, the metal complexation sites construct physical crosslinking points in the amorphous network to increase the sliding resistance of the polyamide macromolecular chain under stress.

[0007] Preferably, in step S1, the metal salt is selected from silver nitrate, copper sulfate, zinc chloride, and zinc acetate; the viscosity of the homogeneous precursor fluid at 90°C is 50 mPa·s to 200 mPa·s; and in step S3, the homogeneous precursor fluid is preheated to 90°C to 100°C before being injected into the homogenization section.

[0008] Preferably, in step S3, the outlet pressure of the injection unit is 2 MPa to 5 MPa higher than the melt pressure in the homogenization section; the homogenization section of the melt modification equipment is provided with at least two sets of kneading blocks, which construct a stretching flow field inside the mixed melt to assist the metal ions in combining with the polyamide macromolecular chains.

[0009] Preferably, in step S5, the side-blowing temperature of the cooling forming zone is 15°C to 25°C, and the wind speed is 0.3m / s to 0.8m / s; the draw ratio below the cooling forming zone is 3.0 to 4.5; and the metal complex sites are anchored inside the amorphous region of the long-lasting antibacterial polyamide fiber through coordination bonds.

[0010] Preferably, the monofilament fineness of the long-lasting antibacterial polyamide fiber is 0.5 dtex to 2.5 dtex; the breaking elongation of the antibacterial fabric is 20% to 35%.

[0011] Preferably, in step S2, the polyamide chips are selected from polyamide 6 chips and polyamide 66 chips, and their relative viscosity is 2.4 to 3.2; the polyamide chips are vacuum dried before being fed into the melt modification equipment, and their moisture content is less than 0.03%.

[0012] Preferably, in step S5, the cooling process controls the distribution density of metal complexation sites between polyamide chips by regulating the cooling rate of the nascent melt stream, so as to maintain the lattice integrity of the internal crystalline region of the long-lasting antibacterial polyamide fiber.

[0013] Preferably, step S6 further includes the following sub-steps: Step S61, in the weaving process, long-lasting antibacterial polyamide fiber is interwoven with one of cotton fiber and polyester fiber to obtain a composite antibacterial fabric; wherein, the weight ratio of long-lasting antibacterial polyamide fiber in the composite antibacterial fabric is not less than 30%.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. In metal ion-embedded polyamide fibers, a deep eutectic fluid homologous to the polyamide monomer is used as a metal ion carrier to ensure that the antibacterial component is in a molecularly homogeneous state before being injected into the polyamide melt. Due to the good thermodynamic compatibility between the precursor and the polyamide matrix, stress concentration caused by heterogeneous interfaces is effectively eliminated. Under the action of critical shear mechanical work applied in the homogenization section of the extruder, the metal ions dissociate from the hydrogen bond network and quickly anchor in situ with the amide groups on the polyamide macromolecular chain in the extended conformation. This process avoids the secondary agglomeration of inorganic particles in the melt laminar flow field in traditional physical blending processes, maintains the long-term stability of the pressure drop on both sides of the filter screen of the spinning component, and ensures that high-performance nylon does not experience filament drift or breakage in continuous production.

[0015] 2. Based on the coupling effect of melt rheological field regulation and non-isothermal crystallization kinetics, the chain segments containing metal complex nodes spontaneously repel and lock into the amorphous region between polyamide chips due to steric hindrance. This specific surface distribution pattern maintains the lattice integrity of the polyamide crystalline region and avoids the physical fragmentation of the fiber skeleton structure by traditional inorganic fillers. At the same time, due to the strong coordination bonds formed between metal ions and amide groups, a high density of physical cross-linking points are constructed in the amorphous region network, which increases the sliding resistance of molecular chain segments under stress. This allows the fiber to retain high intrinsic fracture strength and modulus while providing antibacterial activity, and exhibits reinforcing and toughening properties under specific conditions.

[0016] 3. The atomic-level chemical anchoring mechanism between metal ions and the polyamide backbone enables the formation of stable coordination bonds between functional components and the fiber matrix. Since the bond energy of this chemical bond is much higher than that of physical entanglement or van der Waals forces, the metal ions are in a stable and confined state and distributed in the amorphous network inside the fiber. During subsequent fabric weaving, high-temperature dyeing, and high-frequency strong washing by end users, the functional components cannot overcome the coordination bond energy to migrate to the external medium. The fabric has a long-lasting antibacterial ability that is in sync with the physical lifespan of the fiber, effectively avoiding the environmental burden caused by the loss of antibacterial components and the risk of skin sensitization caused by free metal ions. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation process of the metal ion in-situ embedded antibacterial polyamide fabric of the present invention. Figure 2 This is a schematic diagram of the atomic-level dispersion and amorphous region anchoring mechanism of the antibacterial components of this invention.

[0018] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0020] A method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fibers includes the following steps: Step S1: Caprolactam is mixed with a metal salt at 80°C to 110°C to form a homogeneous precursor fluid with a hydrogen bond network. Step S2: The polyamide chips are fed into the melting section of the melt modification equipment and heated to obtain polyamide melt; Step S3: In the homogenization section of the melt modification equipment, the homogeneous precursor fluid is injected into the polyamide melt through the injection unit at a volume flow ratio of 0.01 to 0.05 between the homogeneous precursor fluid and the polyamide melt to form a mixed melt. Step S4: Adjust the screw speed of the melt modification equipment in the homogenization section, input specific shear work into the mixed melt, so that the polyamide macromolecular chains in the polyamide melt extend to expose the amide groups, and cause phase separation of the homogeneous precursor fluid to release metal ions. The metal ions combine with the amide groups to form metal complexation sites. Step S5: The mixed melt containing metal complexation sites is extruded through a spinneret to obtain a primary melt stream. The primary melt stream is sent into a cooling and forming zone. By adjusting the cooling air temperature and stretching tension, a non-isothermal crystallization gradient is generated, so that the chain segments containing metal complexation sites are locked in the amorphous region network of polyamide fibers, thus obtaining long-lasting antibacterial polyamide fibers. Step S6: The long-lasting antibacterial polyamide fiber is woven into an antibacterial fabric.

[0021] Preferably, in step S4, the screw speed is adjusted so that the input specific shear work is greater than the activation energy threshold for the in-situ coordination reaction between metal ions and amide groups; the metal complexation sites are molecularly dispersed in the polyamide melt, and the tensile strength retention rate of the long-lasting antibacterial polyamide fiber is not less than 98% of that of pure polyamide fiber of the same specification; in step S5, the metal complexation sites construct physical crosslinking points in the amorphous network to increase the sliding resistance of the polyamide macromolecular chain under stress.

[0022] Preferably, in step S1, the metal salt is selected from silver nitrate, copper sulfate, zinc chloride, and zinc acetate; the viscosity of the homogeneous precursor fluid at 90°C is 50 mPa·s to 200 mPa·s; and in step S3, the homogeneous precursor fluid is preheated to 90°C to 100°C before being injected into the homogenization section.

[0023] Preferably, in step S3, the outlet pressure of the injection unit is 2 MPa to 5 MPa higher than the melt pressure in the homogenization section; the homogenization section of the melt modification equipment is provided with at least two sets of kneading blocks, which construct a stretching flow field inside the mixed melt to assist the metal ions in combining with the polyamide macromolecular chains.

[0024] Preferably, in step S5, the side-blowing temperature of the cooling forming zone is 15°C to 25°C, and the wind speed is 0.3m / s to 0.8m / s; the draw ratio below the cooling forming zone is 3.0 to 4.5; and the metal complex sites are anchored inside the amorphous region of the long-lasting antibacterial polyamide fiber through coordination bonds.

[0025] Preferably, the monofilament fineness of the long-lasting antibacterial polyamide fiber is 0.5 dtex to 2.5 dtex; the breaking elongation of the antibacterial fabric is 20% to 35%.

[0026] Preferably, in step S2, the polyamide chips are selected from polyamide 6 chips and polyamide 66 chips, and their relative viscosity is 2.4 to 3.2; the polyamide chips are vacuum dried before being fed into the melt modification equipment, and their moisture content is less than 0.03%.

[0027] Preferably, in step S5, the cooling process controls the distribution density of metal complexation sites between polyamide chips by regulating the cooling rate of the nascent melt stream, so as to maintain the lattice integrity of the internal crystalline region of the long-lasting antibacterial polyamide fiber.

[0028] Preferably, step S6 further includes the following sub-steps: Step S61, in the weaving process, long-lasting antibacterial polyamide fiber is interwoven with one of cotton fiber and polyester fiber to obtain a composite antibacterial fabric; wherein, the weight ratio of long-lasting antibacterial polyamide fiber in the composite antibacterial fabric is not less than 30%.

[0029] Example 1: In the production of medical protective fabrics for environments with high-frequency washing and exposure to highly pathogenic bacteria, when 3 wt% of nano-silver powder is added to polyamide 6 melt-spun yarn, secondary agglomeration is triggered by the surface free energy of the nanoparticles, causing the pressure drop across the filter screen of the spinning assembly to increase from the initial 15 MPa to over 35 MPa within 24 hours. This is accompanied by melt fracture and filament drift at the spinneret. To resolve this contradiction between production stability and antibacterial performance, the preparation method of this invention is adopted, mixing caprolactam and silver nitrate at 100°C for 2 hours to obtain a hydrogen-bonded network. A homogeneous precursor fluid with a viscosity of 125 mPa·s at 90°C was used. Polyamide 6 chips with a relative viscosity of 2.8 were vacuum-dried to a moisture content of 0.02% and then fed into the melting section of a twin-screw extruder for heating. In the homogenization section of the extruder, the precursor fluid was continuously injected via a high-pressure metering pump at a volumetric flow rate ratio of 0.02 to the polyamide melt. The outlet pressure of the injection unit was set to be 3 MPa higher than the melt pressure in the homogenization section. Under the condition that the screw speed in the homogenization section was 280 rpm, the shear mechanical work absorbed per unit volume of the mixed melt was... satisfy: ,in: Shear mechanical work absorbed per unit volume of the mixed melt. The apparent viscosity of the mixed melt. For local shear rate, The residence time of the homogenization segment. The activation energy threshold required for silver ions to complete the in-situ coordination reaction with amide groups.

[0030] This critical shear mechanical work induces the polyamide macromolecular chain to extend highly along the flow field direction, exposing the electron clouds of carbonyl oxygen atoms in the amide groups. Simultaneously, the hydrogen bond network within the deep eutectic fluid undergoes dynamic dissociation under the high-temperature, high-shear field, releasing silver ions with empty orbital activity. These exposed silver ions then undergo in-situ coordination reactions with the extended amide groups, generating metal complexation sites uniformly distributed along the main chain. The mixed melt containing these metal complexation sites is metered through the spinning box and extruded by the spinneret to form a primary melt stream. This stream enters the cooling and forming zone with a side-blown air temperature of 18°C ​​and an air velocity of 0.6 m / s. Under the coupling effect of an initial draw tension of 3.8 times that of the guide disc, the polyamide macromolecular chain traverses the crystallization temperature range and undergoes oriented crystallization. Due to the steric hindrance effect generated by the metal complexation sites, the chain segments containing these sites are spontaneously displaced and solidified within the amorphous regions between the polyamide chips. Silver ions are anchored to the chain segments in the amorphous regions on both sides through coordination bonds to form a physical cross-linking network. The resulting long-lasting antibacterial polyamide fiber monofilament has a fineness of 1.2 dtex and a measured breaking strength of 7.2 cN / dtex, reaching 102% of the breaking strength of pure polyamide fibers of the same specification. Moreover, after 100 cycles of water washing, the antibacterial rate against Staphylococcus aureus remains at 99.8%, confirming that the atomic-level chemical anchoring mechanism integrates spinnability, strength, and permanent antibacterial efficacy through the structural enhancement of the amorphous region without destroying the integrity of the crystalline region.

[0031] Example 2: To verify the performance of the in-situ coordination anchoring mechanism in the preparation of high-performance nylon, a twin-screw experimental production line equipped with an online ultrasonic flow monitoring unit and a melt pressure transmitter was used. The melt pressure transmitter has a measurement resolution of 0.01 MPa. The metering pump control accuracy of the injection system is maintained within 0.2% of the output flow rate. The relative viscosity of the polyamide 6 chips used in the experiment was set to 2.80. To simulate industrial electromagnetic interference, Gaussian white noise with a signal-to-noise ratio of 25 dB was superimposed in the sensor data acquisition circuit. The volumetric flow rate ratio of the precursor fluid to the polyamide melt was set based on the trade-off between antibacterial loading and spinnability stability. When this ratio was adjusted within the range of 0.01 to 0.05, the sensitivity index of the complex viscosity of the mixed melt as a function of frequency was found to remain within the range of 0.85 to 0.92 by online rheometer monitoring, ensuring that no melt fracture occurred during the subsequent high-speed spinning process.

[0032] The sample groups were divided into an experimental group using the method of this invention, a control sample A with 3 wt% nano-silver powder added, and a sample with shear mechanical work. Below the activation energy threshold Compared to control group B, data recordings show that after 12 hours of continuous operation, control group A experienced an increase in pressure drop across the filter screen of the spinning assembly from the initial 15.2 MPa to 34.6 MPa, accompanied by yarn breakage and filament drift. In contrast, the test group maintained a pressure drop fluctuation consistently below 1.8 MPa for 120 hours of continuous operation. Monitoring of the melt in the test group... achieve The infrared spectral characteristics at that time revealed that the absorption peak position of amide I changed from Offset to This phenomenon confirms that the carbonyl oxygen atom in the polar amide group coordinates with the released silver ions. Because the bond energy of the coordinate bond is higher than the normal Candle der Waals force, the metal ions maintain synchronous flow with the macromolecular chain under flow field disturbance, avoiding rheological instability caused by inorganic phase aggregation. Compared to sample group B... Only set to The measured fiber breaking strength was only 5.86 cN / dtex, while the experimental group's measured breaking strength reached 7.24 cN / dtex. Furthermore, energy dispersive spectroscopy analysis showed that the coefficient of variation of silver distribution in the fiber cross-section of the experimental group was less than 3.5%. In the gradient test at the critical parameter boundary, when the volumetric flow rate ratio increased from 0.05 to the out-of-range level of 0.08, the fiber orientation degree decreased from 86.8% to 73.2%. This indicates that the small molecule plasticizing effect of excessive caprolactam induced the inflection point of performance decline, confirming that 0.01 to 0.05 is the working window that balances antibacterial load and mechanical properties. Simultaneously, in the performance titration verification performed at the lower limit boundary, it was confirmed that when the volumetric flow rate ratio further decreased to 0.005 and below, the performance... The amount of energy injected was excessively diluted due to flow field shear, causing the effective silver ion distribution density within the cross-section of a single fiber to fall below the critical inhibitory concentration (MIC) threshold, making it impossible to maintain a high killing rate against the target pathogenic bacteria within 24 hours. Therefore, 0.01 was determined as the minimum engineering loading line to ensure long-lasting broad-spectrum antibacterial stability. The antibacterial durability test results showed that the antibacterial rate of the experimental group against Staphylococcus aureus remained at 99.7% after 100 cycles of water washing, while the antibacterial rate of the control group A decreased from the initial 96.8% to 65.4%. This confirms that the atomic-level chemical anchoring mechanism locks the chain segments containing metal complexation sites into the physical cross-linking network of the amorphous region, achieving a synergistic effect of maintaining mechanical strength, stable spinnability, and permanent antibacterial efficacy.

[0033] In a scenario confirming the state of the hydrogen bond network within the precursor fluid, the vibrational frequency characteristics of a mixture of caprolactam and silver nitrate were determined using laser Raman spectroscopy. When the precursor fluid temperature was maintained at 90°C, the amide groups were observed to exhibit... The stretching vibration peak was 3295.2. Offset to 3280.5 Furthermore, the peak width increased by more than 15.6%, and this frequency redshift and peak broadening confirmed the formation of a high-density hydrogen bond cross-linking network between caprolactam molecules and silver ions. Simultaneously, differential scanning calorimetry was used to scan the phase transition behavior of the precursor fluid in the range of -50℃ to 100℃. The measured curves showed that the system only had a single glass transition process and no metal salt crystal precipitation peaks were observed, indicating that the precursor fluid had been transformed into a thermodynamically stable homogeneous deep eutectic state. This form of silver ion existence based on hydrogen bond network locking not only inhibited the spontaneous reduction of silver ions before injection into the homogenization section, but also reduced the interfacial tension at the moment of contact between the precursor fluid and the polyamide melt through changes in fluid rheological properties, providing a homogeneous material basis for the subsequent in-situ coordination reaction under shear field.

[0034] Example 3: This example combines Figures 1 to 2 The preparation method of long-lasting antibacterial fabric made of metal ion-embedded polyamide fibers is described, such as... Figure 1 As shown, in step S1, caprolactam and metal salt are mixed at 80°C to 110°C to form a homogeneous precursor fluid with a hydrogen bond network. In step S2, polyamide chips are fed into the melting section of a melt modification device for heating to prepare a polyamide melt. In step S3, the precursor fluid is injected into the polyamide melt at a volumetric flow rate ratio of 0.01 to 0.05 to form a mixed melt. Instantaneous pressure pulsations are captured by a differential pressure sensor in the injection unit, and a dynamic compensation path is used to adjust the output speed of the injection pump. In step S4, the screw speed is adjusted... Shear work is applied to the mixed melt to extend the macromolecular chains and decompose the phase to release metal ions, which then combine with the exposed amide groups to form metal complexation sites. At the same time, a stretching flow field is constructed inside the mixed melt using a homogenization section kneading block to assist the bonding process. In step S5, the extruded nascent melt stream is sent into the cooling and forming zone to generate a non-isothermal crystallization gradient, thereby locking the chain segments containing metal complexation sites in the amorphous network to obtain long-lasting antibacterial polyamide fibers. Finally, the long-lasting antibacterial polyamide fibers are made into antibacterial fabrics through the weaving process in step S6.

[0035] like Figure 2 As shown, the associated architecture of the preparation system and the surface locking mechanism is revealed. The system begins with a homogeneous precursor fluid with a hydrogen bond network structure constructed in the raw material pretreatment environment. It is precisely delivered to the melt modification equipment via an injection unit. This equipment integrates a specific shear work input module for inducing macromolecular chain extension and a homogenization section kneading block for constructing a stretching flow field. Under the action of flow field coupling, it enters the metal complexation site generation region to achieve phase decomposition and release metal ions. It enters the cooling and forming system through melt spinning extrusion. The cooling air temperature is adjusted in the non-isothermal crystallization gradient region of the system, so that the functional components are bound and locked in the physical cross-linking network in the amorphous region. Finally, the finished fabric is obtained through the weaving process, and the crystallinity locking efficiency can be verified and fed back to the pretreatment stage.

[0036] Example 4: In continuous spinning processes involving the production of high-load medical equipment cover fabrics, due to batch-to-batch fluctuations in the molecular weight distribution of polyamide 6 matrix chips, the melt viscosity in the homogenization section fluctuates between 150 Pa·s and 180 Pa·s. Maintaining a constant rotation speed would lead to shear mechanical work. Deviation from activation energy threshold This can lead to insufficient distribution of antibacterial components or mechanical degradation of macromolecular chains. To maintain production consistency, a critical shear mechanical work calibration method was established: In a laboratory environment, using a capillary rheometer with a pressure measurement accuracy of 0.05%, the mechanical work of a polyamide mixture containing 2 wt% precursor fluid was measured at different shear rates under a temperature gradient from 260°C to 280°C. Shear stress under ,Record Follow The slope inflection point that appears with the increase corresponds to the energy critical state of hydrogen bond network dissociation and coordination bond formation.

[0037] Calculate the activation energy threshold using the formula: ,in, The activation energy threshold, For shear stress, Shear rate, Using the baseline residence time, in this calibration system, the overall shear mechanical work is converted into localized thermal energy and conformational potential energy of molecular chain segments through the viscous dissipation effect of the polyamide melt. The numerical value is not directly equivalent to the chemical bond energy of the surface monomolecules, but rather characterizes the overall mechanical energy input threshold required for a unit volume of mixed melt to overcome the hydrogen bond network and induce in-situ coordination under critical shear conditions. It implicitly contains the viscous dissipation coefficient for the conversion of mechanical energy to chemical activation energy and the molar volume equivalent conversion relationship. Using a capillary rheometer to determine when the slope inflection point of shear stress with increasing local shear rate occurs, the testing system gradually increases the local shear rate at preset step sizes and collects corresponding shear stress values. The difference between adjacent shear stress values ​​is calculated as a local first derivative sequence, formed by the ratio of the local shear rate step size. When the decrease in the local first derivative value exceeds 15% of the initial linear stage reference derivative value within three consecutive test steps, the current test coordinates are extracted as the slope inflection point. The test parameters at the slope inflection point are then retrieved and substituted into the formula. The calibration reference value for the shear mechanical work absorbed per unit volume of the mixed melt was obtained, and the caprolactam-silver nitrate system at 270°C was measured. for In actual production line operation, the apparent viscosity of the mixed melt under the current operating conditions is calculated by real-time acquisition of the driving current and melt pressure in the homogenization section of the twin-screw extruder. And dynamically adjust the screw speed according to the formula: ,in, For shearing mechanical work, For apparent viscosity, For local shear rate, For the residence time, when the melt viscosity is detected to increase from 160 Pa⋅s to 175 Pa⋅s, the screw speed is reduced from 280 rpm to 265 rpm, so that the calculated residence time is achieved. Maintain at 1.05 to 1.15 times. Within the window, to address the interference of matrix melt mainstream flow fluctuations on antibacterial concentration, the injection unit employs a dynamic compensation path based on differential pressure feedback. A differential pressure sensor with a sampling frequency of 50Hz is installed between the injection pump outlet and the homogenization section cavity to capture instantaneous pressure pulsations. The injection pump output speed is set as the product of the matrix melt main pump speed and the volumetric flow rate ratio coefficient, and a pressure compensation operator is superimposed. The volumetric flow rate ratio coefficient is set to 0.03. When the homogenization section pressure increases by 0.5MPa due to increased melt resistance, the control system automatically corrects the pressure compensation operator upward by 2% to offset the injection flow loss caused by the increase in back pressure. The silver ion content in the fibers produced by spinning for 48 consecutive hours is consistently below 0.08wt%. In the differential pressure feedback-adjusted injection pump output speed dynamic compensation control process, the injection unit controller periodically reads the pressure difference between the instantaneous melt pressure in the homogenization section cavity collected by the differential pressure sensor and the preset reference pressure, extracting the pressure difference value within a single control cycle. The discrete-time integral term and the proportional coefficient are multiplied to generate a pressure compensation operator. When the instantaneous melt pressure is higher than the preset reference pressure, an additional positive pressure compensation operator drive signal is transmitted to the injection pump speed control module to increase the output flow rate. When the instantaneous melt pressure is lower than the preset reference pressure, an additional negative pressure compensation operator drive signal is transmitted to the injection pump speed control module to decrease the output flow rate. The proportional parameter of the injection unit and the matrix melt volume flow rate is constrained within the calibration range. In order to adapt to the non-Newtonian shear thinning characteristics of polyamide macromolecular fluid, the proportional coefficient and integral time constant on which the above pressure difference integral term is extracted are not fixed constants, but are obtained by offline tuning based on the step response curve of the polyamide mixed melt. The proportional gain parameter is related to the empirical function that is negatively correlated with the zero-shear viscosity of the melt, and the integral constant is aligned with the average relaxation time of the polymer chain segments at a specific temperature. This eliminates the phase lag and flow oscillation that are easily induced by conventional negative feedback algorithms in viscoelastic media.

[0038] To verify the atomic-level embedded structure, the structure of the fabricated polyamide fibers was characterized. Layer-by-layer peeling and scanning revealed a shift in the silver 3d electron orbital binding energy from 368.2 eV in pure silver nitrate to 367.5 eV. This 0.7 eV shift confirmed the formation of coordinate bonds between silver ions and the carbonyl oxygen atoms of the amide group. Simultaneously, differential scanning calorimetry was used to determine the crystallinity of the fibers. The crystallinity of the experimental group fibers remained between 34.5% and 36.2%, a change of less than 5% compared to pure polyamide fibers. However, the glass transition temperature of its amorphous region remained relatively stable. By increasing the temperature from 52.6℃ to 61.8℃, the physical cross-linking network formed by the metal complex sites in the amorphous region restricts the movement of chain segments. The measured single-filament fracture strength reached 7.32 cN / dtex. In the high-temperature creep experiment at 120℃, the permanent deformation after 10 hours was 45% of that of the control group with added nano-silver powder. This confirms that the in-situ coordination mechanism induced by the precisely calibrated shear mechanical work can strengthen the structure of the amorphous region without interfering with the main crystallization process.

[0039] Example 5: In a preparation scenario where the batch of caprolactam raw material was changed and the ambient humidity changed, the hygroscopicity of caprolactam caused a deviation in the hydrogen bond association strength within the precursor fluid. To determine the initial thermodynamic stability of the homogeneous precursor fluid, caprolactam was heated to 105°C using an oil bath. Silver nitrate crystals (10% by mass) were added in five portions at a stirring rate of 150 rpm, with each addition spaced 20 minutes apart. The conductivity of the system was monitored using a conductivity meter. rate of change ,when When the viscosity at three consecutive sampling points is below 0.05 mS / (cm·min), the system enters a dissolution equilibrium state; the resulting fluid is cooled to 90°C and the apparent viscosity is measured using a rotational viscometer. When the measured viscosity deviates from the benchmark value of 125 mPa·s by more than 5%, the viscosity is restored to the range of 123 mPa·s to 127 mPa·s by adding or distilling off a trace amount of caprolactam. This establishes a compatibility benchmark between the precursor fluid and the polyamide melt at the injection point, and enables the generation of a primary dispersed phase with a particle size distribution variation coefficient of less than 4.2% in the subsequent homogenization stage.

[0040] When the system is deployed in a twin-screw extruder with a length-to-diameter ratio of 40 and a modified screw assembly in the homogenization section, an online calibration procedure is performed using standard polyamide 6 chips with a relative viscosity of 2.80 to calibrate the local shear rate γ to meet the critical shear mechanical work W constraint requirement. The pressure difference ΔP between the inlet and outlet of the homogenization section is recorded within a screw speed gradient from 100 rpm to 400 rpm. The formula γ = ⋅ Calculate the local shear rate, where γ is the local shear rate. The proportionality coefficient is determined by the screw geometry. Given the screw speed, the pressure drop versus speed response curve is fitted to determine the appropriate speed for this equipment. The value is 1.25. Based on the real-time measured apparent viscosity η of the melt, the target rotation speed is determined to be 275 rpm, so that the shear mechanical work W absorbed by the unit volume of the mixed melt is 4.5 × J / m3; Under these parameters, the melt containing metal complexation sites passes through a 0.25mm orifice spinneret, and the melt pressure fluctuation range is within 0.3MPa within 72 hours of continuous spinning. The resulting long-lasting antibacterial polyamide fiber, when observed by transmission electron microscopy, shows that the silver element is in an atomic-level dispersed state and no crystal nuclei aggregates larger than 5nm are observed.

[0041] When the system generates a non-isothermal crystallization gradient by adjusting the cooling air temperature and drawing tension, the depth at which the metal complexation sites are locked in the amorphous region depends on the coupling logic between the cooling rate and the nascent fiber draw ratio. The side-blowing air velocity is set to 0.5 m / s to 0.8 m / s, and the guide plate draw ratio is... satisfy Under this stretching energy field, the conformational entropy of the polyamide macromolecular chain changes, inducing rapid nucleation of crystal grains within milliseconds and displacing large-volume metal complex groups. When the side-blowing air velocity is controlled towards the cooling upper limit of 0.8 m / s, the steep cooling rate of the nascent melt causes the relaxation time of the macromolecular chain to be much longer than the crystallization time, resulting in a high-density explosive generation of crystal nuclei. The displaced metal complex sites are highly densely distributed in the confined amorphous region network. Conversely, reducing the air velocity to 0.5 m / s makes the cooling rate relatively gradual, allowing the crystal to obtain sufficient three-dimensional growth period to form perfect lamellar crystals. The metal complex sites exhibit a more loosely distributed array as the volume of the amorphous region expands relatively, thus establishing a precise mapping path between the cooling conditions and the surface site distribution characteristics. The long period of the fiber is measured using a small-angle X-ray scattering instrument. Changes were observed in the fibers of the experimental group. The value increased by 2.5 nm to 4.2 nm compared to pure polyamide fiber. This increase in spacing confirms that metal ions are anchored in the amorphous region chain segments through coordination bonds to form physical cross-linking points, which restricts the free relaxation of the amorphous region chain segments. After 100 cycles of water washing, the retention rate of metal ions inside the fiber increased to more than 98.5% of the original loading, which confirms the effective binding effect of the physical cross-linking network of the amorphous region on the functional components.

[0042] Example 6: In a preparation environment involving the switching of multiple batches of polyamide 6 chips, fluctuations in the flow field resistance within the homogenization section of the twin-screw extruder were caused by the melt index deviation of different batches of raw materials. To calibrate the pressure balance parameters of the precursor fluid and the polyamide melt at the injection point, a flow response mapping procedure was executed. Under no-load conditions, the temperature of each zone of the twin-screw extruder was set to 270°C. Within the screw speed gradient of 100 rpm to 350 rpm, the back pressure signal of the main flow channel was collected using a pressure transmitter at the injection orifice. Simultaneously, caprolactam fluid was injected through a metering pump, and different pumping pressures were recorded. The flow deviation value is established based on the pressure difference. Traffic correction method ,in, To inject back pressure differential, This is the flow sensitivity coefficient. To determine the system's zero-point residual, the least squares method is used to fit the sampled data points to determine the residual under the equipment's operating conditions. The value is 0.015. The value is 0.002. This correction method is loaded into the controller register of the injection unit. During subsequent operation, when the melt pressure increases by 1.2 MPa due to changes in raw material viscosity, the controller will adjust the correction method accordingly. The metering pump speed is compensated to maintain the volumetric flow rate ratio of the antibacterial component in the polyamide matrix within the range of 0.0195 to 0.0205, and to ensure that the spatial distribution range of metal complexation sites in the nascent melt stream is lower than a preset threshold.

[0043] When the system faces a boundary condition where the filter clogging rate of the spinning assembly reaches 10%, in order to suppress melt fracture and activate the compensation path, an abnormal adjustment procedure based on the second derivative of pressure is executed. The melt pressure in front of the spinneret is monitored by a sensor with a sampling frequency of 100Hz. The processor calculates the first derivative of the rate of pressure change in real time. With the second derivative Set early warning thresholds 0.5MPa / ,when Five consecutive sampling periods exceeding At that time, the system sends a coupled adjustment command for rotational speed and temperature to maintain the shearing mechanical power. Constant at 4.5 Under the condition of J / m3, the homogenization section temperature is increased by 3℃ simultaneously to reduce the apparent viscosity of the melt. And reduce the shear rate By utilizing the reduced viscous resistance to flush away deposits on the filter screen surface, the peak instantaneous pressure fluctuation is reduced to within 0.15 MPa. Due to the minute-level physical hysteresis of heat conduction in the extruder's metal barrel, this command actually triggers a dual-timescale collaborative compensation mechanism: on the millisecond-level transient scale, the controller fine-tunes the output torque of the main motor to induce high-frequency micro-perturbations in the local shear flow field, thereby immediately breaking the dead zone deposits at the filter screen; on the minute-level steady-state scale, the slow rise in the homogenization section temperature serves as a long-term thermodynamic correction, gradually reducing the overall melt's base viscosity. The combination of these two measures achieves physical self-consistency from transient fracture suppression to steady-state flow field reshaping. After the adjustment procedure is completed, the breaking strength of the produced polyamide fiber monofilament is measured to be 7.15 cN / dtex, and the physical crosslinking density of silver ions in the amorphous region within the fiber remains stable. Through quantitative feedback of the equipment's dynamic characteristics, the manufacturing process maintains parameter closed-loop operation under varying operating conditions.

[0044] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0045] Finally, it should be noted that 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fibers, characterized in that, Includes the following steps: Step S1: Caprolactam is mixed with a metal salt at 80°C to 110°C to form a homogeneous precursor fluid with a hydrogen bond network. Step S2: The polyamide chips are fed into the melting section of the melt modification equipment and heated to obtain polyamide melt; Step S3: In the homogenization section of the melt modification equipment, the homogeneous precursor fluid is injected into the polyamide melt through the injection unit at a volume flow ratio of 0.01 to 0.05 between the homogeneous precursor fluid and the polyamide melt to form a mixed melt. Step S4: Adjust the screw speed of the melt modification equipment in the homogenization section, input specific shear work into the mixed melt, so that the polyamide macromolecular chains in the polyamide melt extend to expose the amide groups, and cause phase separation of the homogeneous precursor fluid to release metal ions. The metal ions combine with the amide groups to form metal complexation sites. Step S5: The mixed melt containing metal complexation sites is extruded through a spinneret to obtain a primary melt stream. The primary melt stream is sent into a cooling and forming zone. By adjusting the cooling air temperature and stretching tension, a non-isothermal crystallization gradient is generated, so that the chain segments containing metal complexation sites are locked in the amorphous region network of polyamide fibers, thus obtaining long-lasting antibacterial polyamide fibers. Step S6: The long-lasting antibacterial polyamide fiber is woven into an antibacterial fabric.

2. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, In step S4, the screw speed is adjusted so that the input specific shear work is greater than the activation energy threshold for the in-situ coordination reaction between metal ions and amide groups; the metal complex sites are molecularly dispersed in the polyamide melt, and the tensile strength retention rate of the long-lasting antibacterial polyamide fiber is not less than 98% of that of pure polyamide fiber of the same specification; in step S5, the metal complex sites construct physical crosslinking points in the amorphous network to increase the sliding resistance of the polyamide macromolecular chain under stress.

3. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, In step S1, the metal salt is selected from silver nitrate, copper sulfate, zinc chloride, and zinc acetate; the viscosity of the homogeneous precursor fluid at 90°C is 50 mPa·s to 200 mPa·s; in step S3, the homogeneous precursor fluid is preheated to 90°C to 100°C before being injected into the homogenization section.

4. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, In step S3, the outlet pressure of the injection unit is 2 MPa to 5 MPa higher than the melt pressure in the homogenization section; the homogenization section of the melt modification equipment is equipped with at least two sets of kneading blocks, which construct a stretching flow field inside the mixed melt to assist the metal ions in binding with the polyamide macromolecular chains.

5. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, In step S5, the side-blowing temperature of the cooling forming zone is 15°C to 25°C, and the wind speed is 0.3m / s to 0.8m / s; the draw ratio below the cooling forming zone is 3.0 to 4.5; and the metal complexation sites are anchored inside the amorphous region of the long-lasting antibacterial polyamide fiber through coordination bonds.

6. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, The monofilament fineness of long-lasting antibacterial polyamide fiber is 0.5 dtex to 2.5 dtex; the breaking elongation of antibacterial fabric is 20% to 35%.

7. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, In step S2, the polyamide chips are selected from polyamide 6 chips and polyamide 66 chips, and their relative viscosity is 2.4 to 3.2; the polyamide chips are vacuum dried before being fed into the melt modification equipment, and their moisture content is less than 0.03%.

8. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, In step S5, the cooling process controls the distribution density of metal complexation sites between polyamide chips by regulating the cooling rate of the nascent melt stream, so as to maintain the lattice integrity of the internal crystalline region of the long-lasting antibacterial polyamide fiber.

9. The method for preparing a long-lasting antibacterial fabric of metal ion-embedded polyamide fiber according to claim 1, characterized in that, Step S6 further includes the following sub-steps: Step S61, in the weaving process, long-lasting antibacterial polyamide fiber is interwoven with one of cotton fiber and polyester fiber to obtain a composite antibacterial fabric; wherein, the weight ratio of long-lasting antibacterial polyamide fiber in the composite antibacterial fabric is not less than 30%.

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