Process for manufacturing anion antiviral antibacterial non-woven fabric

Abstract

This invention relates to the field of nonwoven material manufacturing technology and discloses a process for manufacturing negative ion antiviral and antibacterial nonwoven fabric, comprising: extruding polymer melt through a spinneret and refining it using a stretching hot airflow; adjusting the cooling rate to establish the viscoelastic transition zone of the melt from a molten state to a solidified state; injecting negative ion powder into the melt stream through a load flow within the viscoelastic transition zone, maintaining the load flow pressure in the range of 1.2 to 1.8 times the stretching hot airflow pressure, so that the powder is implanted into the fiber surface and its embedding depth is controlled, and stacked into a web. This invention utilizes a phase change window to induce the powder to undergo physical transition to the fiber surface, forming a semi-embedded in-situ anchoring structure, effectively solving the problem of bulk embedding of active sites, and increasing the exposure density of surface ionized active sites while maintaining the physical continuity and strength of the fiber skeleton.

Description

Technical Field

[0001] This invention belongs to the field of nonwoven material manufacturing technology, and in particular relates to a process for manufacturing negative ion antiviral and antibacterial nonwoven fabric. Background Technology

[0002] Currently, introducing functional components into the polymer matrix to enhance the antibacterial properties of nonwoven materials is the mainstream technology in the industry. This typically involves masterbatch blending and spinning, where functional particles are pre-dispersed in the polymer melt, extruded through spinnerets, and drawn into fibers by a high-speed hot airflow. Finally, these fibers are stacked into a web on a receiving device. As filtration efficiency requirements increase, the diameter of nonwoven fibers continues to decrease towards the micron and submicron levels. This leads to physical constraints on traditional blending processes under high-ratio drawing conditions. Due to the significant modulus difference and rheological incompatibility between the polymer matrix and the inorganic functional particles, the particles, as heterogeneous nodes distributed within the fiber, not only cannot effectively contact the external environment but also generate severe stress concentration.

[0003] However, existing functional improvements in nonwovens mostly focus on reinforcing equipment and changing the shape of rollers, while neglecting the profound impact of material spatial distribution logic on fiber quality. This leads to an irreconcilable physical contradiction between the degree of functionalization and the strength of the fiber structure. For example, Chinese invention patent application CN120250248A discloses a negative ion antibacterial far-infrared nonwoven fabric and its production process. By directly adding modified nanocomposite powder and far-infrared filler to polypropylene for melt mixing, composite fibers are produced by relying on the traditional spinning process. This premixed modification mode results in the functional particles being randomly distributed in the cross-section of the fiber. A large number of active sites are buried deep in the fiber core by the polymer matrix and cannot effectively contact the external air environment, resulting in a significant limitation on ionization efficiency and antibacterial activity. At the same time, inorganic particles, as heterogeneous nodes, occupy the stress-bearing cross section of the fiber, which can easily induce stress concentration during ultrafine stretching, thus restricting the overall strength of the nonwoven material.

[0004] Therefore, how to achieve controlled segregation and physical pinning of functional components on the surface of nonwoven fibers, while ensuring efficient exposure of functional sites and maintaining the tensile strength of the fiber skeleton, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] The present invention aims to solve the problems of low utilization rate of functional particles in ultrafine fibers and unstable fiber formation induced by high loading of powder.

[0006] In this technical solution, a process for manufacturing negative ion antiviral and antibacterial nonwoven fabric includes the following steps:

[0007] Step S101: The polymer melt with a melt index of 1200g / 10min to 1500g / 10min is extruded through the spinneret assembly, and a primary side stretching hot airflow is introduced to stretch the melt stream generated by the polymer melt, thereby generating a high-speed melt stream that travels toward the receiving web forming device.

[0008] Step S102: Adjust the cooling rate of the stretching environment along the movement axis of the high-speed melt stream to position the high-speed melt stream in the viscoelastic transition zone where the latent heat of crystallization is released and the surface tension coefficient jumps. The viscoelastic transition zone is located within the axial distance range of 10cm to 30cm below the spinneret assembly.

[0009] In step S103, within the viscoelastic transition zone, negative ion powder with an average particle size of 300 nm to 500 nm is vertically injected into the high-speed melt stream using a conveying airflow. The injection pressure of the conveying airflow is maintained within the range of 1.2 to 1.8 times the pressure of the primary side stretching hot airflow, so that the negative ion powder overcomes the air boundary layer resistance around the high-speed melt stream and tangentially penetrates into the fiber surface. The radial distance between the center of the negative ion powder and the fiber axis is controlled by adjusting the injection pressure, so that the embedding depth of the negative ion powder inside the fiber is within the range of 5% to 15% of the fiber diameter.

[0010] Step S104 involves stacking fibers carrying negative ion powder on a receiving and web-forming device, using the residual heat of the fibers to induce molecular chain diffusion and entanglement at the interface between the negative ion powder and the polymer matrix, forming an in-situ anchoring structure with interfacial active exposed sites.

[0011] Preferably, in step S101, the polymer melt is a polypropylene melt, and the pressure of the primary side stretching hot gas flow is controlled within the range of 0.05 MPa to 0.15 MPa, and the temperature is controlled within the range of 240°C to 280°C; in step S103, the negative ion powder includes one or more combinations of tourmaline powder, nano silver particles, and zinc oxide particles, and the feeding rate of the negative ion powder is controlled within the range of 1.5 g / min to 5.0 g / min.

[0012] Preferably, between step S102 and step S103, the following step is also included: monitoring the ambient humidity in the viscoelastic transition zone; when the relative humidity exceeds 65%, activating the corona discharge device to apply electrostatic charge to the negative ion powder, so that the negative ion powder carries a charge with the opposite polarity to the high-speed melt stream, and using the Coulomb force between opposite charges to counteract the interference of the high humidity environment on the radial movement path of the negative ion powder.

[0013] Preferably, in step S103, airflow is delivered through symmetrical slit nozzles set on both sides of the high-speed melt stream, and the spray angle of the symmetrical slit nozzles is adjusted so that the negative ion powder generates asymmetrical impact on the radial cross section of the high-speed melt stream, inducing surface wrinkles in the high-speed melt stream before solidification, thereby increasing the mechanical bonding area between the negative ion powder and the polymer matrix.

[0014] Preferably, in step S103, the surface of the negative ion powder is coated with a polymer film formed by modification with a silane coupling agent. The difference between the polarity of the polymer film and the polarity of the polymer melt is lower than a preset threshold. The interfacial frictional resistance when the negative ion powder is implanted into the high-speed melt stream is reduced by utilizing the thermal melting characteristics of the polymer film in the viscoelastic transition zone.

[0015] Preferably, step S103 specifically includes the following steps: setting up multiple injection points on the travel path of the high-speed melt stream, and by adjusting the jet pressure of the conveying airflow at different injection points, constructing a concentration gradient distribution of negative ion powder in the thickness direction of the nonwoven fabric, so that the fiber powder load on the side closer to the receiving web forming device is lower than the fiber powder load on the side farther away from the receiving web forming device.

[0016] Preferably, after step S104, the method further includes the step of: feeding the fiber layer after web formation into a two-roller pressing device for hot pressing, setting the temperature of the pressing rollers to be 20°C to 30°C lower than the softening point temperature of the polymer melt, and using mechanical pressure to further press the negative ion powder at the interface active exposure site into the polymer matrix to improve the physical stability of the in-situ anchoring structure under dynamic airflow impact.

[0017] Preferably, in step S102, the position of the viscoelastic transition zone within the axial distance range is adjusted according to the change in the melt index of the polymer melt. When the melt index increases, the axial distance between the viscoelastic transition zone and the spinneret assembly is reduced to compensate for the curing delay caused by the decrease in viscosity of the high-speed melt stream.

[0018] Preferably, the nonwoven fabric produced by the manufacturing method has a filtration efficiency of not less than 99.9% for sodium chloride aerosol with a diameter of 0.3μm at a filtration wind speed of 20m / min, and the decay rate of the negative ion release per unit area generated by the negative ion powder after 50 standard washing cycles is less than 5%.

[0019] Compared with existing technologies, the negative ion antiviral and antibacterial nonwoven fabric manufacturing process of this invention has the following advantages:

[0020] 1. In the production of negative ion antiviral and antibacterial nonwoven fabric, the wettability difference between the polymer matrix and the negative ion powder is utilized to induce incompatible components to undergo directional physical transition to the fiber surface before fiber solidification. This causes the functional components to form a semi-embedded in-situ anchoring structure on the fiber surface. This mechanism avoids the phenomenon of functional sites being confined to the bulk phase inside the fiber. Under the premise of maintaining the total amount added, the direct contact area between the functional components and the external air environment is increased, thereby improving the exposure density of ionized active sites on the surface of the nonwoven fiber at the physical level.

[0021] 2. The momentum compensation effect generated by the micro-perturbation airflow induces the segregation of negative ion powder towards the radial outer side of the fiber, reducing the probability of inorganic particles being distributed in the core stress area of ​​the fiber and reducing the risk of stress concentration inside the fiber cross section. This spatial distribution reconstruction ensures the physical continuity of the ultrafine fiber during high-ratio stretching, avoiding fiber breakage and dripping phenomena caused by traditional mixing methods. While maintaining the overall strength of the nonwoven material, it supports the refinement of the fiber diameter and optimizes the uniformity of the pore size distribution.

[0022] 3. Relying on the self-locking effect of the fiber surface in a subcritical viscoelastic state, the negative ion powder is fixed to the fiber skeleton surface through physical pinning. This in-situ generation process forms a molecular chain-level interpenetrating entanglement between the functional components and the fiber matrix. The strength of this bonding method is better than that of external coating process. Without clogging the existing microporous structure of nonwoven fabric, it solves the problem of functional components peeling off under dynamic airflow impact, and ensures the performance stability of the filter medium during long-term use. Attached Figure Description

[0023] Figure 1 This is a flowchart of the manufacturing process of the negative ion antiviral and antibacterial nonwoven fabric of the present invention;

[0024] Figure 2 This is a schematic diagram illustrating the state evolution principle of the in-situ anchoring structure of negative ion powder in this invention. Detailed Implementation

[0025] 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.

[0026] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0027] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0028] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0029] A manufacturing process for negative ion antiviral and antibacterial nonwoven fabric includes the following steps:

[0030] Step S101: The polymer melt with a melt index of 1200g / 10min to 1500g / 10min is extruded through the spinneret assembly, and a primary side stretching hot airflow is introduced to stretch the melt stream generated by the polymer melt, thereby generating a high-speed melt stream that travels toward the receiving web forming device.

[0031] Step S102: Adjust the cooling rate of the stretching environment along the movement axis of the high-speed melt stream to position the high-speed melt stream in the viscoelastic transition zone where the latent heat of crystallization is released and the surface tension coefficient jumps. The viscoelastic transition zone is located within the axial distance range of 10cm to 30cm below the spinneret assembly.

[0032] In step S103, within the viscoelastic transition zone, negative ion powder with an average particle size of 300 nm to 500 nm is vertically injected into the high-speed melt stream using a conveying airflow. The injection pressure of the conveying airflow is maintained within the range of 1.2 to 1.8 times the pressure of the primary side stretching hot airflow, so that the negative ion powder overcomes the air boundary layer resistance around the high-speed melt stream and tangentially penetrates into the fiber surface. The radial distance between the center of the negative ion powder and the fiber axis is controlled by adjusting the injection pressure, so that the embedding depth of the negative ion powder inside the fiber is within the range of 5% to 15% of the fiber diameter.

[0033] Step S104 involves stacking fibers carrying negative ion powder on a receiving and web-forming device, using the residual heat of the fibers to induce molecular chain diffusion and entanglement at the interface between the negative ion powder and the polymer matrix, forming an in-situ anchoring structure with interfacial active exposed sites.

[0034] Preferably, in step S101, the polymer melt is a polypropylene melt, and the pressure of the primary side stretching hot gas flow is controlled within the range of 0.05 MPa to 0.15 MPa, and the temperature is controlled within the range of 240°C to 280°C; in step S103, the negative ion powder includes one or more combinations of tourmaline powder, nano silver particles, and zinc oxide particles, and the feeding rate of the negative ion powder is controlled within the range of 1.5 g / min to 5.0 g / min.

[0035] Preferably, between step S102 and step S103, the following step is also included: monitoring the ambient humidity in the viscoelastic transition zone; when the relative humidity exceeds 65%, activating the corona discharge device to apply electrostatic charge to the negative ion powder, so that the negative ion powder carries a charge with the opposite polarity to the high-speed melt stream, and using the Coulomb force between opposite charges to counteract the interference of the high humidity environment on the radial movement path of the negative ion powder.

[0036] Preferably, in step S103, airflow is delivered through symmetrical slit nozzles set on both sides of the high-speed melt stream, and the spray angle of the symmetrical slit nozzles is adjusted so that the negative ion powder generates asymmetrical impact on the radial cross section of the high-speed melt stream, inducing surface wrinkles in the high-speed melt stream before solidification, thereby increasing the mechanical bonding area between the negative ion powder and the polymer matrix.

[0037] Preferably, in step S103, the surface of the negative ion powder is coated with a polymer film formed by modification with a silane coupling agent. The difference between the polarity of the polymer film and the polarity of the polymer melt is lower than a preset threshold. The interfacial frictional resistance when the negative ion powder is implanted into the high-speed melt stream is reduced by utilizing the thermal melting characteristics of the polymer film in the viscoelastic transition zone.

[0038] Preferably, step S103 specifically includes the following steps: setting up multiple injection points on the travel path of the high-speed melt stream, and by adjusting the jet pressure of the conveying airflow at different injection points, constructing a concentration gradient distribution of negative ion powder in the thickness direction of the nonwoven fabric, so that the fiber powder load on the side closer to the receiving web forming device is lower than the fiber powder load on the side farther away from the receiving web forming device.

[0039] Preferably, after step S104, the method further includes the step of: feeding the fiber layer after web formation into a two-roller pressing device for hot pressing, setting the temperature of the pressing rollers to be 20°C to 30°C lower than the softening point temperature of the polymer melt, and using mechanical pressure to further press the negative ion powder at the interface active exposure site into the polymer matrix to improve the physical stability of the in-situ anchoring structure under dynamic airflow impact.

[0040] Preferably, in step S102, the position of the viscoelastic transition zone within the axial distance range is adjusted according to the change in the melt index of the polymer melt. When the melt index increases, the axial distance between the viscoelastic transition zone and the spinneret assembly is reduced to compensate for the curing delay caused by the decrease in viscosity of the high-speed melt stream.

[0041] Preferably, the nonwoven fabric produced by the manufacturing method has a filtration efficiency of not less than 99.9% for sodium chloride aerosol with a diameter of 0.3μm at a filtration wind speed of 20m / min, and the decay rate of the negative ion release per unit area generated by the negative ion powder after 50 standard washing cycles is less than 5%.

[0042] Example 1: On a continuous production line for meltblown nonwoven fabric with an annual output of thousands of tons, a process for manufacturing negative ion antiviral and antibacterial nonwoven fabric solves the physical repulsion between functional components and material strength when the fiber diameter is refined to below 2μm. By achieving load orientation and anchoring within the viscoelastic transition zone of the fiber bundle from liquid to semi-solid state, the powder embedding phenomenon caused by traditional blending spinning is avoided, allowing each functional particle to act as an interfacial active center exposed to the air environment. The specific operation process involves using polypropylene melt with a melt index of 1350g / 10min... The molten material is fed to the spinneret assembly via a screw extruder. The spinneret temperature is set to 265°C. Simultaneously, a primary side drawing hot airflow with a pressure of 0.12 MPa and a temperature of 260°C is introduced, generating a melt stream that travels at high speed toward the receiving and web-forming device. During this process, multi-stage variable frequency cold air boxes deployed on both sides of the drawing zone are dynamically intervened. The controller changes the air volume and initial air temperature of the boxes in real time based on the local temperature feedback signal to precisely adjust the convective heat transfer coefficient of the system. This allows the physical application of the environmental cooling rate without disturbing the flow pattern of the main drawing field.

[0043] By adjusting the cooling rate of the drawing environment, the injection point is positioned 20 cm below the spinneret assembly. This position corresponds to the viscoelastic transition zone where the melt stream is in the latent heat of crystallization release and the surface tension coefficient undergoes a jump. Using symmetrical slit nozzles on both sides of the stream, tourmaline powder with an average particle size of 400 nm is injected by a conveying airflow. At this time, the injection pressure of the conveying airflow is maintained. Under the pressure of primary side stretching hot gas flow Although the absolute pressure of this local jet is higher than that of the main drawing gas field, due to the sub-millimeter opening limit of the slit nozzle, the total mass flow rate and the absolute kinetic energy of the system are at an extremely low level. The kinetic energy of this pulse jet can only be consumed at a specific point to break through the aerodynamic resistance boundary layer that is closely attached to the surface of the melt bundle, and is not enough to change or tear the momentum of the main structure of the stream traveling along the axial direction. This ensures the high-speed continuous forming of the fiber. The momentum compensation mechanism drives the powder to penetrate the turbulent boundary layer and implant it into the fiber surface. By adjusting the injection pressure, the embedding depth of the negative ion powder is controlled within 10% of the fiber diameter, so that the powder produces a semi-embedded arrangement on the radial outer side of the fiber.

[0044] This injection method, occurring within a subcritical phase transition window, generates a synergistic effect. Utilizing the stress-induced crystallization phenomenon of polypropylene at extremely high draw ratios, it pushes non-crystallizing inorganic powder to the fiber edge. This process, where surface-level molecular chains rapidly align and densify to form crystal nuclei, causes a sharp contraction and localized spatial collapse of the amorphous region surrounding the crystal. This triggers intense overall structural repulsion and hydrodynamic lateral extrusion, giving the rigid powder free within the amorphous region a driving force to migrate outwards. Combined with the sudden change in surface tension during stream curing, this induces a physical transition of negative ion powder to the low-surface-energy fiber surface, altering the spatial topological distribution of functional components. The powder, originally a stress concentration point, no longer occupies the core stress area of ​​the fiber. While maintaining the physical continuity and strength of the fiber skeleton, the active sites previously locked inside the fiber are reconstructed into interfacial active sites that can directly contact pathogens. The fibers carrying negative ion powder are then stacked on a receiving and web-forming device, utilizing the fiber's own phase transition residue... Thermally induced diffusion entanglement at the molecular chain level occurs between the polymer matrix and the powder interface, forming an in-situ anchoring structure with exposed interfacial active sites. When multi-stage pressure gradient injection is deployed along the jet path, the powder brought in by the kinetic energy of different jets is physically locked onto the cross-section of its corresponding single-strand flying fiber. Due to the rapid cooling of the fibers into a semi-solid state in a very short time and the formation of irreversible strong adhesive mechanical encapsulation of the particles, even if the subsequent web stacking undergoes violent overall three-dimensional airflow turbulence and folding, the load of each layer of functional components that are independently anchored will not undergo overall homogenization or secondary detachment and dispersion in the thickness direction of the fabric. The clear concentration gradient distribution characteristics of the preset injection state are retained from bottom to top. According to the test, the nonwoven fabric prepared by this process has a 210% increase in negative ion release per unit area under the same functional component addition amount, and the retention rate of functional components is maintained at 96.5% after 50 standard washing cycles. This scheme solves the technical conflict between high-load functionalization and the processing stability of ultrafine fibers by introducing momentum perturbation within a specific material physical field time sequence.

[0045] Example 2: In this example, the verification environment used was a pilot-scale meltblown nonwoven fabric unit with online thermal field distribution monitoring. This platform was equipped with a sensor with a melt temperature control accuracy of 0.1℃ and an airflow pressure sensing unit with a sampling frequency of 100Hz. Data acquisition was based on continuous production conditions and superimposed with airflow pulse disturbances with a signal-to-noise ratio of 20dB to simulate the pneumatic interference environment in industrial production. The injection pressure was considered... The setting is based on the primary side stretching hot airflow pressure. Determine the momentum compensation amount to balance the kinetic energy required for the powder to overcome boundary layer resistance with the physical stability of the flow stream within the viscoelastic transition region. When the pressure is in the range of 0.05MPa to 0.15MPa, adjust the injection pressure to... and The ratio remained in the range of 1.2 to 1.8.

[0046] The experiment was divided into a control group using the traditional melt blending process and an experimental group using this process. In the control group, 3% by weight of negative ion powder was premixed with polypropylene chips and then melt-spun. The stress cross section of a single fiber showed that the powder particles were concentrated in the stress area of ​​the fiber center, resulting in a decrease in the single fiber breaking strength from 0.92N in the substrate to 0.58N, and the negative ion release per unit area was 380 ions / cm³. In the experimental group, tourmaline powder with a feed rate of 2.5g / min and an average particle size of 400nm was injected into the viscoelastic transition zone 20cm below the spinneret assembly. The stress-induced crystallization phenomenon during the stretching process was used to guide the powder that did not participate in crystallization to migrate radially outward of the fiber. The measured radial distance between the powder center and the fiber axis showed that its embedding depth inside the fiber was stable at about 8.5% of the fiber diameter, forming a semi-embedded anchoring structure. Under this state, the fiber breaking strength was 0.86N, and the negative ion release per unit area reached 1945 ions / cm³.

[0047] To verify the pressure proportionality coefficient The reasonableness of the scope, increase The lower limit control group with a value of 1.1 and The upper limit control group had a value of 1.9, among which... The pressure proportionality coefficient is determined by... and The ratio is determined when When the value is 1.1, the load flow cannot effectively penetrate the turbulent boundary layer around the high-speed stream, and the negative ion release drops to 412 ions / cm³, indicating that the functional components have not been effectively implanted into the fiber surface; when At a value of 1.9, although the negative ion release remained at 1920 ions / cm³, the excessive lateral shear stress disrupted the stability of the flow stream within the subcritical phase transition window, leading to a deterioration in fiber breaking strength to 0.35 N and impaired network uniformity. The emergence of these nonlinear performance inflection points confirms that the pressure ratio range of 1.2 to 1.8 is the optimal working window for achieving synergy between functional efficiency and strength. Comparison of physical indicators and surface morphology under different process gradients confirms that this process scheme, by capturing the viscoelastic characteristics of the material's phase transition window and using momentum compensation to guide the functional load to generate surface segregation, resolves the physical conflict between high-load functionalization and the stability of ultrafine fiber processing. The experimental data provides a definite physical experimental basis for the pressure ratio range, achieving simultaneous improvement in functional efficiency and mechanical strength.

[0048] Example 3: In a meltblown nonwoven fabric production system with a sub-millisecond feedback response frequency, the cooling process of the melt after flowing through the spinneret is affected by environmental turbulence and humidity fluctuations. Accurately locating the spatial coordinates of the viscoelastic transition zone is crucial. To ensure load orientation and anchoring, a linear array monitoring unit consisting of 12 miniature infrared thermopile sensors is deployed axially below the spinneret assembly. This sensor array has a measurement range covering 100°C to 300°C and a spatial resolution of 2 mm. During the production start-up phase, the system controller acquires the temperature sequence values ​​output by the sensor array in real time. The system identifies the cooling slope of the melt stream by calculating the temperature drop between adjacent measuring points. Based on the physical law that the latent heat release during polymer crystallization phase transition offsets convective heat dissipation, the system converts the temperature drop into an axial temperature gradient. The controller monitors the absolute value of the axial temperature gradient. When the absolute value of the axial temperature gradient between three consecutive adjacent measuring points decreases to within the phase transition determination threshold, it indicates that the latent heat caused by polymer molecular chain rearrangement is being released. The phase transition determination threshold is set to 0.2℃ / cm to 0.5℃ / cm. This characteristic gradient threshold range is based on the current spinning design. The forced convection heat dissipation flux due to the background wind speed in the stretching zone, after deducting the specific heat capacity of the polypropylene matrix and the energy compensated for the sudden release of latent heat of phase change per unit mass, is used to calculate the theoretical net temperature drop slope according to the thermodynamic conservation equilibrium equation of the flow field interface. Below this lower bound, the weak phase change signal will be drowned out by environmental thermal noise; above this upper bound, it indicates that the determination of the freezing point lags behind the actual location of molecular nucleation. A quantitative evaluation procedure is introduced to establish a stability judgment benchmark. When the temperature drop slope changes from linear decay to a plateau and the temperature value is at the crystallization initiation temperature of the polypropylene material, the stability judgment benchmark is established. When the location is nearby, it is determined as the physical boundary of the viscoelastic transition zone; where For spatial coordinates, These are temperature sequence values. The crystallization initiation temperature of polypropylene is determined by the physical mechanism that when the polymer system approaches the crystallization initiation point, the molecular chain conformation is reconstructed from a loose and random state to a tightly ordered aggregated state, which leads to a steep drop in the free energy of the gas-liquid interface. This thermal field temperature measurement plateau period established by the concentrated release of latent heat of crystallization, and the mechanical extreme value transition point of the fluid interfacial tension coefficient, constitute a strictly strong coupled physical synchronous excitation within the millisecond time window of spinning and curing, ensuring that the thermodynamic parameters have a time-difference equivalent marking of the mechanical abrupt change position.

[0049] For closed-loop control of the embedding depth of negative ion powder in the fiber surface, the system is based on established spatial coordinates. Adjust the vertical height of the injection nozzle and implement a pressure proportionality coefficient. The momentum matching procedure employs a linear array charge-coupled device (CCD) sensing unit to acquire backlit contour images between the spinneret and the web-forming assembly during the preparatory stage, establishing a displacement vector model of the melt stream under different lateral wind velocities. Then, during operation, the controller reads the primary side stretching hot gas pressure. The real-time value, and according to the formula To calculate the target injection pressure and stabilize the embedding depth of the negative ion powder at 10% of the fiber diameter, the system automatically performs momentum self-calibration every 300 seconds, which involves monitoring the surface roughness of the fibers after web formation. In the process of acquiring the index, based on the principle of diffuse reflection of the surface structure of the multiphase medium interface, the system uses an online laser scattering instrument to collect the spatial distribution signal of the reflected light intensity on the fabric surface, and uses fast Fourier transform to extract the high-frequency signal components. The low-frequency baseline waveform interference introduced by the overall fiber stacking and pore structure is removed, and the high-frequency roughness feature value characterizing the density of powder particle protrusions on the single fiber surface is output as the fiber surface roughness index. The actual control input is used by the controller to synchronously read the internally stored offline calibration database. The target control range is defined using the correlation data between the absolute embedding depth measured by transmission electron microscopy and the high-frequency roughness feature values. The system compares the currently acquired feature values; if... If the deviation from the preset range is detected, fine-tuning will be performed in increments of 0.01. This value is used to offset momentum dissipation caused by nozzle carbon buildup or changes in filter pressure; among which, The jet pressure for delivering the airflow, The pressure of the hot gas flow during the first side stretching. This is the pressure proportionality coefficient. As an index of fiber surface roughness, before performing the above-mentioned online feedback control, the system preloaded an analytical dimension reduction operator. This operator constructs a unique deterministic algebraic mapping correlation model between the overall light intensity fluctuation amplitude coefficient of offline measured samples of different morphologies and the absolute penetration depth ratio of particles on the surface of the single fiber. This opens up a control link that directly closes the loop to characterize the nanoscale local physical displacement using overall statistical parameters.

[0050] To address the issue of decreased ionization efficiency of functional particles in high-humidity environments, the system introduces charge polarity compensation logic based on ambient humidity. This is achieved by using an electrochemical humidity sensor deployed on the side of the viscoelastic transition region to collect ambient relative humidity data. ,when When the value exceeds the 65% threshold for five consecutive sampling cycles, the controller drives the needle-type corona discharge electrode located at the end of the delivery pipeline to generate a 5kV negative high-voltage DC electric field, so that the tourmaline powder carries a negative charge before being ejected. As the polypropylene melt is extruded at high speed through the micro-holes of the spinneret, the polymer macromolecular chains undergo triboelectric charging due to the strong frictional shearing action of the inner wall of the flow channel, and spontaneously carry and accumulate positive static charge. Therefore, the applied negative electric field can be directly based on the charge state of the powder and the high-speed flow stream with opposite polarities. At the same time, the potential of the electrostatic induction plate of the receiving web forming device is set to +2kV. The Coulomb attraction between opposite charges is used to enhance the migration speed of the powder to the high-speed melt flow stream, thereby maintaining the exposure density of functional components on the fiber surface without increasing the injection pressure. The final nonwoven fabric still has a stable negative ion release under complex weather conditions.

[0051] Example 4: When the production system switches between different batches of polypropylene raw materials, the melt index of the polypropylene raw materials fluctuates within the range of 1200 g / 10 min to 1500 g / 10 min, changing the cooling dynamic path of the melt stream. The system uses a linear array monitoring unit composed of 12 infrared thermopile sensors to perform initial calibration. Under the conditions that the drawing hot gas flow pressure is set to 0.12 MPa and the temperature is set to 260°C, the linear array monitoring unit scans the temperature sequence values ​​of the stream movement axis online. The controller calculates the temperature drop between adjacent measuring points and extracts the spatial position where the temperature drop is reduced to a preset threshold. The system sets the obtained spatial coordinates as the target injection height for the current material batch. Through the above calibration, the system locks the injection position of the negative ion powder at the surface tension transition window caused by the release of latent heat of crystallization.

[0052] When the production system changes the negative ion powder components with different particle size distributions, the system executes the momentum response debugging process to establish the pressure proportional coefficient. The mapping relationship between the pressure and the powder embedding depth, and the selection of pressure proportional coefficients in the debugging process. For the three test nodes 1.2, 1.5, and 1.8, the primary side stretching hot gas flow pressure was fixed. Under these conditions, the production system prepares test sample fabric. The detection module measures the radial distance from the center of the powder to the fiber axis within a single fiber cross-section using electron microscopy and calculates the ratio of the radial distance to the fiber diameter. Based on this, the system uses a linear interpolation algorithm to generate a pressure compensation curve corresponding to the current batch of negative ion powder. During continuous production, the controller retrieves parameters from this pressure compensation curve in real time according to the set target embedding depth and adjusts the injection pressure accordingly. This completes the momentum compensation of the powder under the impact of the high-speed stream.

[0053] Example 5: When the production system is in the start-up phase or facing a batch changeover of polypropylene raw materials, the system initiates the online parameter calibration procedure. Under the conditions that the drawing hot gas flow pressure is set to 0.12 MPa and the temperature is set to 260°C, the system controller drives a linear array monitoring unit composed of 12 infrared thermopile sensors to collect temperature sequence values ​​in real time along the axial direction of the melt flow. The controller calculates the temperature drop between adjacent measuring points, extracts the spatial coordinates of the temperature drop reduction to the judgment threshold, and records the spatial coordinates as the physical boundary of the viscoelastic transition zone of the current material batch. It then sets this spatial coordinate as the target injection height for subsequent processes, thereby calibrating the procedure to lock the spatial coordinates of the surface tension transition region caused by the release of latent heat of crystallization.

[0054] When the production system encounters changes in the particle size distribution characteristics of negative ion powder components, the system performs a momentum calibration test procedure to establish a pressure proportionality coefficient. The system sequentially sets pressure proportionality coefficients to establish a mapping relationship between the powder implantation characteristics and the powder implantation features. The pressures are 1.2, 1.5, and 1.8, with the primary side stretching hot gas flow pressure fixed. Under operating conditions, three sets of test samples were prepared. The radial distance from the powder center to the fiber axis within a single fiber cross-section was extracted using electron microscopy, and the ratio of the radial distance to the fiber diameter was calculated. Based on this ratio, the system controller used a linear interpolation algorithm to generate a pressure compensation curve corresponding to the current batch of powder. In subsequent continuous production processes, the controller dynamically adjusts the jet pressure of the conveying airflow by retrieving parameters from this curve in real time according to the set embedding depth target. To maintain the momentum balance of functional powders under the impact of high-speed melt stream.

[0055] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A manufacturing process for negative ion antiviral and antibacterial nonwoven fabric, characterized in that, Includes the following steps: Step S101: The polymer melt with a melt index of 1200g / 10min to 1500g / 10min is extruded through the spinneret assembly, and a primary side stretching hot airflow is introduced to stretch the melt stream generated by the polymer melt, thereby generating a high-speed melt stream that travels toward the receiving web forming device. Step S102: Adjust the cooling rate of the stretching environment along the movement axis of the high-speed melt stream to position the high-speed melt stream in the viscoelastic transition zone where the latent heat of crystallization is released and the surface tension coefficient jumps. The viscoelastic transition zone is located within the axial distance range of 10cm to 30cm below the spinneret assembly. In step S103, within the viscoelastic transition zone, negative ion powder with an average particle size of 300 nm to 500 nm is vertically injected into the high-speed melt stream using a conveying airflow. The injection pressure of the conveying airflow is maintained within the range of 1.2 to 1.8 times the pressure of the primary side stretching hot airflow, so that the negative ion powder overcomes the air boundary layer resistance around the high-speed melt stream and tangentially penetrates into the fiber surface. The radial distance between the center of the negative ion powder and the fiber axis is controlled by adjusting the injection pressure, so that the embedding depth of the negative ion powder inside the fiber is within the range of 5% to 15% of the fiber diameter. Step S104 involves stacking fibers carrying negative ion powder on a receiving and web-forming device, using the residual heat of the fibers to induce molecular chain diffusion and entanglement at the interface between the negative ion powder and the polymer matrix, forming an in-situ anchoring structure with interfacial active exposed sites.

2. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, In step S101, the polymer melt is polypropylene melt, and the pressure of the primary side stretching hot gas flow is controlled within the range of 0.05MPa to 0.15MPa, and the temperature is controlled within the range of 240℃ to 280℃; in step S103, the negative ion powder includes one or more combinations of tourmaline powder, nano silver particles and zinc oxide particles, and the feeding rate of the negative ion powder is controlled within the range of 1.5g / min to 5.0g / min.

3. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, Between steps S102 and S103, the following step is also included: monitoring the ambient humidity in the viscoelastic transition zone; when the relative humidity exceeds 65%, activating the corona discharge device to apply electrostatic charge to the negative ion powder, so that the negative ion powder carries a charge with the opposite polarity to the high-speed melt stream, and using the Coulomb force between opposite charges to counteract the interference of the high humidity environment on the radial movement path of the negative ion powder.

4. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, In step S103, airflow is delivered through symmetrical slit nozzles set on both sides of the high-speed melt stream, and the spray angle of the symmetrical slit nozzles is adjusted so that the negative ion powder generates asymmetrical impact on the radial cross section of the high-speed melt stream, inducing surface wrinkles to be generated in the high-speed melt stream before solidification, thereby increasing the mechanical bonding area between the negative ion powder and the polymer matrix.

5. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, In step S103, the surface of the negative ion powder is coated with a polymer film formed by modification with a silane coupling agent. The difference between the polarity of the polymer film and the polarity of the polymer melt is lower than a preset threshold. By utilizing the thermal melting characteristics of the polymer film in the viscoelastic transition zone, the interfacial frictional resistance when the negative ion powder is implanted into the high-speed melt stream is reduced.

6. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, Step S103 specifically includes the following steps: setting up multiple injection points on the travel path of the high-speed melt stream, and by adjusting the jet pressure of the conveying airflow at different injection points, constructing a concentration gradient distribution of negative ion powder in the thickness direction of the nonwoven fabric, so that the fiber powder load on the side closer to the receiving web forming device is lower than the fiber powder load on the side farther away from the receiving web forming device.

7. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, After step S104, the following steps are also included: feeding the fiber layer after web formation into a two-roller pressing device for hot pressing, setting the temperature of the pressing rollers to be 20°C to 30°C lower than the softening point temperature of the polymer melt, and using mechanical pressure to further press the negative ion powder at the interface active exposure site into the polymer matrix to improve the physical stability of the in-situ anchoring structure under dynamic airflow impact.

8. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, In step S102, the position of the viscoelastic transition zone within the axial distance range is adjusted according to the change in the melt index of the polymer melt. When the melt index increases, the axial distance between the viscoelastic transition zone and the spinneret assembly is reduced to compensate for the curing delay caused by the decrease in viscosity of the high-speed melt stream.

9. The manufacturing process of a negative ion antiviral and antibacterial nonwoven fabric according to claim 1, characterized in that, The nonwoven fabric produced by the manufacturing method has a filtration efficiency of no less than 99.9% for sodium chloride aerosol with a diameter of 0.3μm at a filtration wind speed of 20m / min, and the decay rate of the negative ion release per unit area generated by the negative ion powder after 50 standard washing cycles is less than 5%.

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