A continuous hot press sealing edge process for medical packaging bag

Abstract

This application relates to the field of medical packaging processing technology, specifically disclosing a continuous hot-press sealing process for medical packaging bags. The sealing film used in this process is made from medical-grade polyolefin as the base material, combined with stress-luminescent microparticles that have undergone surface passivation modification. The film material possesses good biocompatibility and stable mechanoluminescence properties, enabling visual feedback of internal stress within the sealing edge. Its preparation method achieves continuous production through an integrated process of preparing a stress-sensitive heat-sealing film, ultrasonic stress history clearing, gradient hot-press sealing, differential spectroscopy detection, intelligent defect judgment, closed-loop defect repair, and gradient slow cooling shaping. The functional film material of this application can be widely used in the mass production of medical sterile paper-plastic packaging bags, accurately identifying microscopic latent defects in the sealing edge, achieving in-situ non-destructive testing of each item, and effectively reducing the risk of finished product sealing failure. Simultaneously, the entire preparation process is compatible with continuous production lines, steadily improving the sealing quality and production qualification rate of medical packaging bags.

Description

Technical Field

[0001] This application relates to the field of medical packaging processing technology, and more specifically, it relates to a continuous heat-sealing process for medical packaging bags. Background Technology

[0002] Medical paper-plastic composite packaging bags are commonly used for the final sterilization and sealing of medical devices. They are made by continuously heat-sealing medical dialysis paper with polyolefin film. The quality of the sealing directly determines the long-term stability of the sterile barrier of the packaging. Currently, the industrial production of medical packaging mainly relies on continuous heat-sealing production lines for mass production. Most of the industry's current production systems separate heat-sealing and quality inspection into independent processes. The heat-sealing process involves continuous material feeding, while the inspection process is conducted afterward for quality control screening. This production layout is widely used in large-scale mass production, but the supporting traditional quality inspection solutions are gradually showing their limitations.

[0003] The industry commonly uses manual visual inspection, offline peel testing of finished products, and water immersion leak testing as routine quality control methods. Manual observation can only identify visible surface damage and cannot detect microscopic hidden defects caused by adhesion abnormalities inside the seal. Offline destructive testing requires finished product samples, and production costs limit the ability to test all products. Hidden defects such as false sealing and over-sealing are easily missed and remain inside the finished product, gradually deteriorating and causing seal failure during subsequent sterilization and storage. The urgent technical problem to be solved in this field is to achieve in-situ, online, non-destructive detection of microscopic hidden defects in packaging bag seals under continuous production conditions. Summary of the Invention

[0004] To address the problem that existing technologies struggle to detect microscopic latent defects in the sealing of packaging bags in situ during continuous production, this application provides a continuous hot-press sealing process for medical packaging bags.

[0005] A continuous heat-sealing process for medical packaging bags includes the following steps: S1. Stress film material preparation: Medical-grade polyolefin substrate is selected, and non-migratory and biocompatible stress-luminescent microparticles are incorporated to prepare a stress-sensitive heat-sealing film with stress-luminescent properties. S2, Conditioning and Ultrasonic Zeroing: After unwinding the stress-sensitive heat-sealing film and medical dialysis paper, the film is conditioned at a constant temperature. Then, focused ultrasonic vibration is applied to the heat-sealed area to clear the carrier traps of the stress-luminescent microparticles, thus returning their force-light response history to zero. S3, Gradient hot-press sealing: The stacked materials are fed into a special-shaped hot-pressing mold with a continuous gradient structure. The mold has a temperature gradient zone with decreasing temperature in the sealing width direction. The cavity surface has micron-level protrusions to form a pressure gradient. Hot pressing forms a continuous and gradually changing cohesive gradient band. S4. Differential spectroscopy detection: Immediately following the heat sealing station, while there is residual heat at the sealing edge, a pulsed ultraviolet light source and a linear scanning camera are used to simultaneously acquire bright field frames and dark field frames. The thermal radiation background signal contained in the dark field frame is removed from the bright field frame to obtain a pure stress fluorescence image. S5. Intelligent Diagnosis and Judgment: Using a spectral band with fluorescence intensity that decreases continuously and smoothly from the inside to the outside as the qualification criterion, it identifies false sealing and over-sealing defects and generates a judgment signal; S6. Defect closed-loop feedback: The judgment signal is fed back to the heat sealing mold. The mold is equipped with multiple independent heating sections along the sealing edge length. The temperature of the corresponding section is automatically adjusted according to the defect to carry out online repair and remove defects that cannot be repaired. S7. Constant Temperature Slow Cooling and Shaping: Qualified edge banding does not leave the production line. It is first shaped at a constant temperature, and then cooled in a dual gradient of temperature and humidity.

[0006] By adopting the above technical solutions, a fully integrated production system has been constructed, encompassing material functionalization, precise stress control, embedded optical inspection, real-time closed-loop repair, and stress stabilization. This system breaks through the traditional offline sampling inspection model after heat sealing, transforming the heat-sealing film itself into a quality sensor capable of sensing internal stress, enabling in-situ, non-destructive, and comprehensive online inspection of heat-sealing quality. A continuously varying cohesive gradient band is proactively constructed, allowing different degrees of heat-sealing defects to correspond to differentiated stress signals, amplifying defect features for accurate identification. A hierarchical closed-loop feedback mechanism enables online defect repair rather than post-defect rejection, while maintaining continuous production line operation throughout the process, significantly improving production efficiency and yield, fundamentally solving the industry pain point of ineffective detection of microscopic defects in medical packaging bags.

[0007] Preferably, in step S1, the stress-luminescent microparticles are sulfoxa compounds or rare earth-doped aluminates that have been passivated on the surface of silica or medical-grade silane coupling agent, and the mass percentage of their doping is 0.5%-5%.

[0008] By employing the above technical solutions, surface passivation modification can form a dense chemical isolation layer on the surface of stress-luminescent microparticles. This layer, through chemical bonding, coats the microparticle surface, effectively preventing the migration and precipitation of internal metal ions to the membrane surface, thus ensuring the biosafety of medical packaging. Simultaneously, the modification layer improves the interfacial compatibility between the microparticles and the polyolefin substrate, reduces interfacial tension, minimizes microparticle aggregation, and ensures uniform distribution of stress-luminescent properties within the membrane. The doping levels balance luminescence detection sensitivity with the basic properties of the membrane. Dithiooxazone compounds exhibit fast stress response, meeting the real-time detection requirements of high-speed production lines; rare-earth-doped aluminates offer long afterglow, satisfying the offline re-inspection requirements after product delivery.

[0009] Preferably, in step S1, the thickness of the stress-sensitive heat-sealing film is 30μm-60μm, and it is transparent or semi-transparent under normal conditions. It emits visible fluorescence only when subjected to tensile or shear stress exceeding a preset stress threshold under ultraviolet light excitation.

[0010] By adopting the above technical solution, the thickness range can adapt to the conventional heat-sealing requirements of medical packaging bags of different specifications, and can be flexibly selected according to the weight and shape of the packaged medical device. The transparent and semi-transparent properties under normal conditions do not affect the visual observation of the medical device inside the packaging, meeting the appearance inspection requirements before hospital use. The stress-triggered luminescence characteristic is based on the crystal field distortion effect. When the film material is subjected to external force, the crystal structure of the stress-emitting particles undergoes reversible lattice distortion, causing electrons in the ground state to gain energy and transition to the excited state. When the electrons return to the ground state, they release energy in the form of photons, thus directly converting the invisible stress distribution inside the seal into a visible optical signal.

[0011] Preferably, in step S2, the temperature of the isothermal conditioning is 45℃-55℃, the time is 3s-5s, and the moisture content of the material is controlled at 4%-6%; the frequency of the focused ultrasonic vibration is 20kHz-50kHz, the power density is 0.1W / cm²-0.5W / cm², and the action time is 0.5s-1.5s.

[0012] By employing the above technical solutions, the isothermal conditioning temperature is close to the glass transition temperature range of the polyolefin substrate, allowing for reversible slight relaxation of the film material's molecular chains. This effectively eliminates macroscopic internal stress generated during storage, unwinding, and tension conveying of the roll material, ensuring a consistent material state upon entering the heat-sealing station. Controlling the moisture content range prevents water vaporization and bubble formation during heat sealing, while also preventing embrittlement and cracking due to excessively low moisture content. Focused ultrasonic vibration transmits energy via mechanical waves, using phonon excitation to provide sufficient energy for trapped charge carriers to break free, achieving zero stress history. The ultrasonic energy within this parameter range acts only on the microscopic charge carrier level, without causing material melting or chemical structural changes, ensuring that the detection signal only reflects the stress state generated during this heat-sealing process.

[0013] Preferably, in step S3, the high temperature inside the gradient temperature zone is 175℃-200℃, and the low temperature outside is 120℃-140℃, with the temperature decreasing linearly or stepwise; the heat sealing time is 1.0s-2.0s, and the cohesive gradient band width is 3mm-8mm.

[0014] By employing the above technical solution, the high temperature on the inner side allows the polyolefin substrate to fully melt, forming a strong mechanical interlock and intermolecular forces with the dialysis paper fibers, ensuring the overall sealing strength of the edge. The low temperature on the outer side only causes slight softening of the substrate, forming a weak bonding interface, resulting in a continuous cohesive force distribution from high-strength to weak bonding along the width of the edge. A linear or stepped temperature reduction method can be flexibly selected according to different material properties, achieving precise control of the cohesive force gradient. The cohesive force gradient band can fix the edge peeling interface inside the heat-sealing layer, preventing dialysis paper damage and paper debris from contaminating medical devices. Simultaneously, it fully amplifies the stress differences caused by defects such as incomplete sealing and over-sealing, improving the defect detection rate.

[0015] Preferably, in step S4, the wavelength of the pulsed ultraviolet light source is 360nm-400nm, and the single pulse width is 10μs-50μs; the edge sealing residual temperature is 60℃-100℃.

[0016] By employing the above technical solution, the wavelength range of the light source is highly matched with the excitation spectrum of the stress-emitting particles, maximizing the excitation of fluorescence signals and improving detection sensitivity. The pulsed operating mode reduces the average power of the light source, avoiding aging and discoloration of the film material caused by prolonged ultraviolet irradiation. Testing is performed under residual heat at the sealing edge, when the fusion layer has not yet fully crystallized, resulting in the most stable stress state. The test results accurately reflect the actual bonding quality after heat sealing. The differential spectroscopy detection method effectively eliminates background interference caused by the heat radiation of the sealing edge itself, improves the image signal-to-noise ratio, and enables pixel-level quantitative detection of micro-stress distribution.

[0017] Preferably, in step S5, a preset upper limit threshold and a lower limit threshold for fluorescence intensity are used to automatically mark defects. The upper limit threshold corresponds to the material damage state, and the lower limit threshold corresponds to the false sealing state. The thresholds are preset based on the calibration curve of stress fluorescence intensity and peel strength.

[0018] By employing the above technical solution, a quantitative correlation between fluorescence intensity and edge-sealing peel strength is established, enabling quantitative detection rather than qualitative judgment of heat-sealing quality. The upper threshold corresponds to the stress level at which irreversible damage such as micro-cracks and molecular chain breakage occurs in the film material, at which point the long-term sealing reliability of the edge cannot be guaranteed; the lower threshold corresponds to the stress level at which the edge-sealing bonding strength is lower than the stress level required by medical standards, posing a risk of incomplete sealing. By pre-calibrating the correlation under different materials and process parameters, the detection threshold can be accurately set, avoiding misjudgments and omissions, and ensuring the consistency of product quality across different batches.

[0019] Preferably, in step S6, the number of independent heating sections is not less than three; when a false sealing feature is detected, the mold temperature of the section is increased by 1℃-5℃, and when an over-sealing feature is detected, the mold temperature of the section is decreased by 1℃-5℃; when more than a preset proportion of the same type of defect is continuously detected, the overall mold temperature baseline, heat sealing time, or film unwinding tension is automatically adjusted.

[0020] By adopting the above technical solution, multiple independent heating sections can achieve precise local temperature control along the sealing length, enabling targeted repair of single-point or small-scale defects while avoiding impact on other qualified areas. The temperature adjustment range effectively improves the fusion state and repairs defects without causing significant temperature fluctuations that could lead to new defects in adjacent areas. The tiered adjustment mechanism can simultaneously address both single-point random defects and systemic process drift. When similar defects occur consecutively, it indicates an overall shift in process parameters. By automatically adjusting global process parameters, batch defect problems can be resolved at their root, achieving adaptive control of the production process and reducing manual intervention.

[0021] Preferably, in step S7, the temperature for constant temperature shaping is 85℃-95℃, and the holding time is 2s-3s.

[0022] By adopting the above technical solution, the constant temperature setting allows the molecular chains of the fusion layer, which are in a highly elastic state after heat sealing, to fully relax and rearrange, forming a uniform and stable crystalline structure, thus locking in the geometry and bonding strength of the sealing edge. This process effectively eliminates residual internal stress generated during heat sealing, preventing shrinkage, deformation, warping, and cracking of the sealing edge during subsequent cooling, storage, or sterilization, thereby improving the long-term stability and service life of the sealing edge and ensuring the sealing performance of the product within its shelf life.

[0023] Preferably, in step S7, the temperature in the gradient slow cooling process is gradually reduced from 65℃-75℃ to room temperature at a rate of 3℃ / s-8℃ / s, and the relative humidity of the environment is simultaneously and linearly reduced from 50%-60% to 35%-45%. The cooling rate and the dehumidification rate are kept synchronized, so that the moisture content of the material is always within the moisture absorption equilibrium range throughout the cooling process.

[0024] By adopting the above technical solution, a dual-gradient temperature and humidity-controlled slow cooling method is used instead of the traditional rapid cooling method, which avoids the concentration of internal stress caused by sudden temperature changes. The synchronously changing humidity matches the moisture absorption balance characteristics of the paper-plastic composite material, solving the interfacial stress problem caused by the difference in thermal expansion coefficients between the dialysis paper and the plastic film, preventing the dialysis paper from becoming brittle due to rapid water loss or expanding and deforming due to moisture absorption. This ensures that the material remains in a stable moisture absorption balance state throughout the cooling process, eliminating defects such as edge curling, micro-wrinkles, and delamination at the source of the process, guaranteeing the appearance quality and sealing performance of the sealing edges.

[0025] In summary, this application has the following beneficial effects: 1. Since this application uses stress-sensitive heat-sealing film prepared by incorporating passivated stress-luminescent microparticles into medical-grade polyolefin substrate, the stress inside the sealing edge is converted into visual fluorescent information by utilizing the inherent mechanoluminescence properties of the material. Combined with the subsequent online detection process, the sealing edge can be screened in situ. Microscopic defects inside the sealing edge that are not easily detected by the naked eye can be captured without the need for additional external sensing components.

[0026] 2. In this application, a pre-processing method combining constant temperature tempering and focused ultrasonic vibration is preferred. Ultrasonic energy can release the trapping of charge carriers inside the particles, eliminate stray fluorescence corresponding to historical stress formed during the storage, transportation and unwinding of the roll material, and ensure that the collected fluorescence signal is determined only by the stress generated by this heat sealing, thereby gradually improving the signal interference problem in the defect judgment process.

[0027] 3. The method of this application configures a gradient temperature zone and a cavity micron-sized protrusion structure in a non-circular heat-sealing mold, and simultaneously constructs a gradual temperature field and pressure field along the sealing edge width. After hot pressing, the sealing edge forms a continuously changing cohesive gradient, which effectively widens the stress difference between qualified and defective parts, and assists the optical recognition system to accurately distinguish between two types of defects: false sealing and over-sealing.

[0028] 4. In this application, pulsed ultraviolet light source is preferred to be used in combination with bright and dark frame difference algorithm to remove thermal radiation background. The graded fluorescence threshold is set based on the peel strength calibration curve. Combined with independent temperature control of multiple sections of mold, the defects can be finely adjusted on the spot. Local defect rectification can be completed under the condition of continuous operation of production line, reducing the number of products that are scrapped directly due to minor defects.

[0029] 5. The method of this application sets up two processes in sequence: constant temperature shaping and temperature and humidity coordinated gradient cooling. The constant temperature environment stabilizes the molecular arrangement of the heat-sealed fusion layer, and the synchronous temperature and humidity changes continuously match the moisture absorption law of paper and plastic materials, maintain the stable change of material moisture content, and alleviate the problems of edge shrinkage, edge curling and interface delamination caused by sudden temperature changes. Attached Figure Description

[0030] Figure 1 This is a flowchart of a continuous heat-sealing process for a medical packaging bag provided in this application; Figure 2 This is a bar chart comparing the defect detection rates of the various embodiments and comparative examples provided in this application; Figure 3 This is a bar chart comparing the misjudgment rates of the various embodiments and comparative examples provided in this application; Figure 4 This is a bar chart comparing the coefficient of variation of peel strength of the various embodiments and comparative examples provided in this application; Figure 5This is a bar chart comparing the 12-month peel strength decay rate of the various embodiments and comparative examples provided in this application; Figure 6 This is a bar chart comparing the relative cell proliferation rates of the various embodiments and comparative examples provided in this application. Detailed Implementation

[0031] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0032] Technical Concept: In the current continuous heat-sealing production process of medical paper-plastic packaging bags, there is a lack of in-situ online detection conditions for microscopic adhesion defects inside the seal edge. Traditional quality control relies on manual visual inspection and offline destructive sampling. Manual identification can only detect surface damage and is limited by the visual ability to detect hidden defects such as incomplete or over-sealed seals inside the seal edge. Offline peel-off leak detection is constrained by the cost of consumables and cannot cover all finished products. The above problems mainly arise because conventional heat-sealing films do not have stress feedback functions, and changes in internal stress at the seal edge cannot be converted into intuitive identification signals. There is no non-destructive testing link based on the material's own characteristics, and hidden defects are prone to cause sealing failure during the sterilization and aging stage after being retained in the finished product.

[0033] This solution prepares a functional heat-sealing film by compounding stress-luminescent microparticles with surface passivation treatment inside a polyolefin substrate. Relying on the mechanoluminescence properties of the microparticles, the internal stress of the sealing edge is converted into a fluorescent signal. Combined with pulse differential spectroscopy, effective imaging is extracted and the fluorescence distribution is used to identify various micro-defects. By relying on material body sensing, in-situ non-destructive screening of the entire sealing process can be achieved, thereby improving the industry problem of high missed detection rate in traditional quality inspection.

[0034] Example 1: This example provides a continuous heat-sealing process for medical packaging bags, implemented using the following steps: S1. Preparation of stress-induced film material: Medical-grade polyolefin substrate is selected, and non-migratory and biocompatible stress-luminescent microparticles are incorporated to prepare a stress-induced heat-sealing film with stress-induced luminescence properties.

[0035] The stress-luminescent microparticles were 2.75% by mass of ZnS:Mn, a sulfoxylate compound passivated and modified with silica. Silica coating was performed using a sol-gel method, with tetraethyl orthosilicate as the silicon source, anhydrous ethanol as the solvent, and ammonia as the catalyst. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol was 1:8, the ammonia concentration was 0.5 mol / L, the dropping rate was 2 mL / min, the coating temperature was 60℃, the stirring rate was 300 r / min, and the reaction time was 4 h. After coating, the microparticles were washed three times with deionized water for 10 min each time, and then dried in an 80℃ forced-air drying oven. The film is dried for 12 hours and then passed through a 300-mesh sieve. The stress-sensitive heat-sealing film is prepared by a casting process. The twin-screw extruder has temperature zones of 180℃, 190℃, 210℃, 230℃, and 220℃, a screw speed of 120 r / min, a melt temperature of 225℃, a casting roll temperature of 25℃, a traction speed of 80 m / min, and a winding tension of 15 N / m. The stress-sensitive heat-sealing film has a thickness of 45 μm and is transparent or semi-transparent under normal conditions. It emits orange-yellow visible fluorescence with a wavelength of 580 nm under ultraviolet light excitation only when subjected to tensile or shear stress exceeding a preset stress threshold.

[0036] S2. Conditioning and Ultrasonic Zeroing: After unwinding the stress-sensitive heat-sealing film and medical dialysis paper, the film is conditioned at a constant temperature. Then, focused ultrasonic vibration is applied to the heat-sealed area to clear the carrier traps of the stress-luminescent microparticles, thus returning their force-light response history to zero.

[0037] The constant temperature conditioning channel is 2m long, the wind speed inside the channel is controlled at 0.5m / s, the temperature uniformity deviation is ≤±1℃, the constant temperature conditioning temperature is 50℃, the time is 4s, and the material moisture content is controlled at 5%; the focused ultrasonic vibration adopts a line focusing method, the distance between the ultrasonic probe and the membrane surface is 5mm, the frequency is 35kHz, the power density is 0.3W / cm², the action time is 1.0s, and the width of the ultrasonic vibration area is 2mm wider than the sealing edge width.

[0038] S3. Gradient hot-press sealing: The stacked materials are fed into a non-circular heat-sealing mold with a continuous gradient structure. The mold has a temperature gradient zone with decreasing temperature in the sealing width direction. The cavity surface has micron-level protrusions to form a pressure gradient. Hot pressing forms a continuous and gradually changing cohesive gradient band.

[0039] The gradient heat-sealing mold uses electric heating and is divided into 5 independent temperature-controlled sub-zones along the sealing width. The inner high temperature zone is 187.5℃, and the outer low temperature zone is 130℃. The temperature decreases linearly, and the temperature difference between adjacent sub-zones is 14.375℃. The surface of the mold cavity has micron-level protrusions with a height of 5μm-15μm, which gradually decreases from the inner to the outer side, and the protrusion spacing is 20μm. The alignment accuracy of the stacked materials is controlled within ±0.2mm, the stacking tension is 10N / m, the overall mold pressure is 0.4MPa, the heat-sealing time is 1.5s, and the cohesive gradient band width is 5.5mm.

[0040] S4. Differential spectroscopy detection: Immediately following the heat sealing station, while there is residual heat at the sealing edge, a pulsed ultraviolet light source and a linear scanning camera are used to simultaneously acquire bright field frames and dark field frames. The thermal radiation background signal contained in the dark field frame is removed from the bright field frame to obtain a pure stress fluorescence image.

[0041] The pulsed ultraviolet light source has a wavelength of 380nm, a single pulse width of 30μs, a pulse repetition frequency of 1000Hz, a light source power of 50W, and an irradiation area width that is 3mm wider than the sealing edge width; the sealing edge residual temperature is 80℃; the linear scan camera has a resolution of 2048 pixels, a frame rate of 1000fps, an exposure time of 20μs, and is synchronized with the light source using a hardware triggering method; the differential operation uses a real-time grayscale subtraction algorithm with an operation delay of ≤1ms.

[0042] S5. Intelligent Diagnosis and Judgment: Using a spectral band with fluorescence intensity that decreases continuously and smoothly from the inside to the outside as the qualification criterion, it identifies false sealing and over-sealing defects and generates a judgment signal.

[0043] The system automatically marks defects by pre-setting upper and lower thresholds for fluorescence intensity. The upper threshold corresponds to the material damage state, and the lower threshold corresponds to the false seal state. The thresholds are pre-set based on the calibration curve of stress fluorescence intensity and peel strength. The calibration curve is obtained by testing 200 samples with different heat sealing parameters, measuring their fluorescence intensity and 180° peel strength, and then linearly fitting them using the least squares method. When the local fluorescence intensity is more than 20% lower than the lower threshold, it is judged as a false seal defect, and when it is more than 30% higher than the upper threshold, it is judged as an over-sealing defect.

[0044] S6. Defect Closed-Loop Feedback: The judgment signal is fed back to the heat sealing mold. The mold has multiple independent heating sections along the sealing edge length. The temperature of the corresponding section is automatically adjusted according to the defect to perform online repair and remove defects that cannot be repaired.

[0045] The system consists of six independent heating sections, each 100mm long. The temperature adjustment response time for each heating section is 0.3s, and the temperature control accuracy is ±0.5℃. When a false seal is detected, the temperature of the corresponding section of the mold is increased by 3℃; when an over-sealing is detected, the temperature of the corresponding section of the mold is decreased by 3℃. When more than 4% of the same type of defect are detected consecutively, the overall temperature baseline of the mold, the heat sealing time, or the unwinding tension of the film material is automatically adjusted, with a global temperature adjustment step of 1℃. For defects that cannot be repaired, a pneumatic rejection mechanism is driven to remove them online, with a response time of 0.2s and a rejection accuracy of ±5mm.

[0046] S7. Constant Temperature Slow Cooling and Shaping: Qualified edge banding does not leave the production line. It is first shaped at a constant temperature, and then cooled in a dual gradient of temperature and humidity.

[0047] The constant temperature setting zone is 1.5m long, with a temperature uniformity deviation of ≤±1℃. The constant temperature setting temperature is 90℃, and the holding time is 2.5s. The wind speed in the setting zone is controlled at 0.3m / s. The gradient slow cooling zone is divided into 4 independent temperature and humidity control sub-zones. The temperature is gradually reduced from 70℃ to room temperature at a rate of 5.5℃ / s, and the relative humidity of the environment is synchronously and linearly reduced from 55% to 40%. The cooling rate and dehumidification rate are kept synchronized, so that the moisture content of the material is always within the moisture absorption equilibrium range throughout the cooling process. The surface roughness of the cooling roller is Ra0.2μm, and the rotation speed of the cooling roller is consistent with the material feeding speed of the production line, with a speed deviation of ≤±0.1m / min.

[0048] Example 2: This example provides a continuous heat-sealing process for medical packaging bags, implemented using the following steps: S1. Preparation of stress-induced film material: Medical-grade polyolefin substrate is selected, and non-migratory and biocompatible stress-luminescent microparticles are incorporated to prepare a stress-induced heat-sealing film with stress-induced luminescence properties.

[0049] The stress-luminescent microparticles are rare-earth-doped aluminate SrAl2O4:Eu,Dy, which have been surface passivated and modified with medical-grade silane coupling agent KH-550, with a doping percentage of 0.5%. The silane coupling agent treatment employs a dry modification method, with the amount of silane coupling agent being 1% of the mass of the stress-luminescent microparticles. Anhydrous ethanol is used as a diluent, with a coupling agent to ethanol volume ratio of 1:10. The treatment temperature is 110℃, the stirring rate is 500 r / min, the reaction time is 2 h, and after the reaction, the microparticles are dried at 120℃ for 1 h and passed through a 200-mesh sieve. The stress-inducing heat-sealing film is produced using a blow molding process. The plasticizing process involves a single-screw extruder with temperature zones of 160℃, 180℃, 200℃, 210℃, and 200℃, a screw speed of 80 r / min, a melt temperature of 205℃, a blow-up ratio of 2.5, a traction ratio of 4, a cooling air ring temperature of 20℃, a traction speed of 50 m / min, and a winding tension of 10 N / m. The stress-sensitive heat-sealing film has a thickness of 30 μm and is transparent or translucent under normal conditions. It emits a yellow-green visible fluorescence with a wavelength of 520 nm only when subjected to tensile or shear stress exceeding a preset stress threshold under ultraviolet light excitation.

[0050] S2. Conditioning and Ultrasonic Zeroing: After unwinding the stress-sensitive heat-sealing film and medical dialysis paper, the film is conditioned at a constant temperature. Then, focused ultrasonic vibration is applied to the heat-sealed area to clear the carrier traps of the stress-luminescent microparticles, thus returning their force-light response history to zero.

[0051] The constant temperature conditioning channel is 1.5m long, the wind speed inside the channel is controlled at 0.3m / s, the temperature uniformity deviation is ≤±1.5℃, the constant temperature conditioning temperature is 45℃, the time is 3s, and the material moisture content is controlled at 4%; the focused ultrasonic vibration adopts a point focusing method, the distance between the ultrasonic probe and the membrane surface is 8mm, the frequency is 20kHz, the power density is 0.1W / cm², the action time is 0.5s, and the width of the ultrasonic vibration area is 1mm wider than the sealing edge width.

[0052] S3. Gradient hot-press sealing: The stacked materials are fed into a non-circular heat-sealing mold with a continuous gradient structure. The mold has a temperature gradient zone with decreasing temperature in the sealing width direction. The cavity surface has micron-level protrusions to form a pressure gradient. Hot pressing forms a continuous and gradually changing cohesive gradient band.

[0053] The gradient heat-sealing mold uses electric heating and is divided into three independent temperature-controlled sub-zones along the sealing width. The inner high temperature zone is 175℃, the outer low temperature zone is 120℃, and the temperature decreases in a stepwise manner. The temperature of the middle sub-zone is 147.5℃. The surface of the mold cavity has micron-level protrusions with a height of 3μm-10μm, which gradually decreases from the inner side to the outer side, and the protrusion spacing is 30μm. The alignment accuracy of the stacked materials is controlled within ±0.3mm, the stacking tension is 8N / m, the overall mold pressure is 0.3MPa, the heat-sealing time is 1.0s, and the cohesive gradient band width is 3mm.

[0054] S4. Differential spectroscopy detection: Immediately following the heat sealing station, while there is residual heat at the sealing edge, a pulsed ultraviolet light source and a linear scanning camera are used to simultaneously acquire bright field frames and dark field frames. The thermal radiation background signal contained in the dark field frame is removed from the bright field frame to obtain a pure stress fluorescence image.

[0055] The pulsed ultraviolet light source has a wavelength of 360nm, a single pulse width of 10μs, a pulse repetition frequency of 500Hz, a light source power of 30W, and an irradiation area width that is 2mm wider than the sealing edge width; the sealing edge residual temperature is 60℃; the linear scan camera has a resolution of 1024 pixels, a frame rate of 500fps, an exposure time of 15μs, and is synchronized with the light source using a software triggering method; the differential operation uses a real-time grayscale subtraction algorithm with an operation delay of ≤2ms.

[0056] S5. Intelligent Diagnosis and Judgment: Using a spectral band with fluorescence intensity that decreases continuously and smoothly from the inside to the outside as the qualification criterion, it identifies false sealing and over-sealing defects and generates a judgment signal.

[0057] The system automatically marks defects by pre-setting upper and lower thresholds for fluorescence intensity. The upper threshold corresponds to the material damage state, and the lower threshold corresponds to the false seal state. The thresholds are pre-set based on the calibration curve of stress fluorescence intensity and peel strength. The calibration curve is obtained by testing 100 samples with different heat sealing parameters, measuring their fluorescence intensity and 180° peel strength, and then linearly fitting them using the least squares method. When the local fluorescence intensity is more than 15% lower than the lower threshold, it is judged as a false seal defect, and when it is more than 25% higher than the upper threshold, it is judged as an over-sealing defect.

[0058] S6. Defect Closed-Loop Feedback: The judgment signal is fed back to the heat sealing mold. The mold has multiple independent heating sections along the sealing edge length. The temperature of the corresponding section is automatically adjusted according to the defect to perform online repair and remove defects that cannot be repaired.

[0059] The system consists of three independent heating sections, each 150mm long. The temperature adjustment response time for each heating section is 0.5s, and the temperature control accuracy is ±1℃. When a false seal is detected, the temperature of the corresponding section of the mold is increased by 1℃; when an over-sealing is detected, the temperature of the corresponding section of the mold is decreased by 1℃. When more than 3% of the same type of defect are detected consecutively, the overall temperature baseline of the mold, the heat sealing time, or the unwinding tension of the film material is automatically adjusted, with a global temperature adjustment step of 0.5℃. For defects that cannot be repaired, a pneumatic rejection mechanism is driven to remove them online, with a response time of 0.3s and a rejection accuracy of ±10mm.

[0060] S7. Constant Temperature Slow Cooling and Shaping: Qualified edge banding does not leave the production line. It is first shaped at a constant temperature, and then cooled in a dual gradient of temperature and humidity.

[0061] The constant temperature setting zone is 1m long, with a temperature uniformity deviation of ≤±1.5℃. The constant temperature setting temperature is 85℃, and the holding time is 2s. The wind speed in the setting zone is controlled at 0.2m / s. The gradient slow cooling zone is divided into 3 independent temperature and humidity control sub-zones. The temperature is gradually reduced from 65℃ to room temperature at a rate of 3℃ / s, and the relative humidity of the environment is synchronously and linearly reduced from 50% to 35%. The cooling rate and dehumidification rate are kept synchronized, so that the moisture content of the material is always within the moisture absorption equilibrium range throughout the cooling process. The surface roughness of the cooling roller is Ra0.4μm, and the rotation speed of the cooling roller is consistent with the material feeding speed of the production line, with a speed deviation of ≤±0.2m / min.

[0062] Example 3: This example provides a continuous heat-sealing process for medical packaging bags, implemented using the following steps: S1. Preparation of stress-induced film material: Medical-grade polyolefin substrate is selected, and non-migratory and biocompatible stress-luminescent microparticles are incorporated to prepare a stress-induced heat-sealing film with stress-induced luminescence properties.

[0063] The stress-luminescent microparticles were ZnS:Cu sulfoxide compounds passivated and modified with silica surface, with a mass percentage of 5%. Silica coating was performed using a sol-gel method, with tetraethyl orthosilicate as the silicon source, anhydrous ethanol as the solvent, and ammonia as the catalyst. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol was 1:6, the ammonia concentration was 0.8 mol / L, the dropping rate was 3 mL / min, the coating temperature was 70℃, the stirring rate was 400 r / min, and the reaction time was 6 h. After coating, the microparticles were washed five times with deionized water for 15 min each time, and then dried in a 90℃ forced-air drying oven. The film is dried for 10 hours and then passed through a 400-mesh sieve. The stress-sensitive heat-sealing film is prepared by a casting process. The twin-screw extruder has temperature zones of 190℃, 200℃, 220℃, 240℃, and 230℃, a screw speed of 150 r / min, a melt temperature of 235℃, a casting roll temperature of 20℃, a traction speed of 120 m / min, and a winding tension of 20 N / m. The stress-sensitive heat-sealing film has a thickness of 60 μm and is transparent or translucent under normal conditions. It emits blue visible fluorescence at a wavelength of 450 nm only when subjected to tensile or shear stress exceeding a preset stress threshold under ultraviolet light excitation.

[0064] S2. Conditioning and Ultrasonic Zeroing: After unwinding the stress-sensitive heat-sealing film and medical dialysis paper, the film is conditioned at a constant temperature. Then, focused ultrasonic vibration is applied to the heat-sealed area to clear the carrier traps of the stress-luminescent microparticles, thus returning their force-light response history to zero.

[0065] The constant temperature conditioning channel is 2.5m long, the wind speed inside the channel is controlled at 0.7m / s, the temperature uniformity deviation is ≤±0.5℃, the constant temperature conditioning temperature is 55℃, the time is 5s, and the material moisture content is controlled at 6%; the focused ultrasonic vibration adopts a surface focusing method, the distance between the ultrasonic probe and the surface of the membrane is 3mm, the frequency is 50kHz, the power density is 0.5W / cm², the action time is 1.5s, and the width of the ultrasonic vibration area is 3mm wider than the sealing edge width.

[0066] S3. Gradient hot-press sealing: The stacked materials are fed into a non-circular heat-sealing mold with a continuous gradient structure. The mold has a temperature gradient zone with decreasing temperature in the sealing width direction. The cavity surface has micron-level protrusions to form a pressure gradient. Hot pressing forms a continuous and gradually changing cohesive gradient band.

[0067] The gradient heat-sealing mold uses electric heating and is divided into 8 independent temperature-controlled sub-zones along the sealing width. The inner high temperature zone is 200℃, and the outer low temperature zone is 140℃. The temperature decreases linearly, and the temperature difference between adjacent sub-zones is 8.57℃. The surface of the mold cavity has micron-level protrusions with a height of 8μm-20μm, which gradually decreases from the inner to the outer side, and the protrusion spacing is 15μm. The alignment accuracy of the laminated materials is controlled within ±0.1mm, the lamination tension is 12N / m, the overall mold pressure is 0.5MPa, the heat-sealing time is 2.0s, and the cohesive gradient band width is 8mm.

[0068] S4. Differential spectroscopy detection: Immediately following the heat sealing station, while there is residual heat at the sealing edge, a pulsed ultraviolet light source and a linear scanning camera are used to simultaneously acquire bright field frames and dark field frames. The thermal radiation background signal contained in the dark field frame is removed from the bright field frame to obtain a pure stress fluorescence image.

[0069] The pulsed ultraviolet light source has a wavelength of 400nm, a single pulse width of 50μs, a pulse repetition frequency of 2000Hz, a light source power of 80W, and an irradiation area width that is 4mm wider than the sealing edge width; the sealing edge residual temperature is 100℃; the linear scan camera has a resolution of 4096 pixels, a frame rate of 2000fps, an exposure time of 10μs, and is synchronized with the light source using a hardware triggering method; the differential operation uses a real-time grayscale subtraction algorithm with an operation delay of ≤0.5ms.

[0070] S5. Intelligent Diagnosis and Judgment: Using a spectral band with fluorescence intensity that decreases continuously and smoothly from the inside to the outside as the qualification criterion, it identifies false sealing and over-sealing defects and generates a judgment signal.

[0071] The system automatically marks defects by pre-setting upper and lower thresholds for fluorescence intensity. The upper threshold corresponds to the material damage state, and the lower threshold corresponds to the false seal state. The thresholds are pre-set based on the calibration curve of stress fluorescence intensity and peel strength. The calibration curve is obtained by testing 300 samples with different heat sealing parameters, measuring their fluorescence intensity and 180° peel strength, and then linearly fitting them using the least squares method. When the local fluorescence intensity is more than 25% lower than the lower threshold, it is judged as a false seal defect, and when it is more than 35% higher than the upper threshold, it is judged as an over-sealing defect.

[0072] S6. Defect Closed-Loop Feedback: The judgment signal is fed back to the heat sealing mold. The mold has multiple independent heating sections along the sealing edge length. The temperature of the corresponding section is automatically adjusted according to the defect to perform online repair and remove defects that cannot be repaired.

[0073] The system comprises 10 independent heating sections, each 80mm in length. The temperature adjustment response time for each heating section is 0.2s, and the temperature control accuracy is ±0.3℃. When a false seal is detected, the temperature of the corresponding section of the mold is increased by 5℃; when an over-sealing is detected, the temperature of the corresponding section of the mold is decreased by 5℃. When more than 5% of the same type of defect are detected consecutively, the overall temperature baseline of the mold, the heat sealing time, or the unwinding tension of the film material is automatically adjusted, with a global temperature adjustment step of 2℃. For defects that cannot be repaired, a pneumatic rejection mechanism is driven to remove them online, with a response time of 0.1s and a rejection accuracy of ±3mm.

[0074] S7. Constant Temperature Slow Cooling and Shaping: Qualified edge banding does not leave the production line. It is first shaped at a constant temperature, and then cooled in a dual gradient of temperature and humidity.

[0075] The constant temperature setting zone is 2m long, with a temperature uniformity deviation of ≤±0.5℃. The constant temperature setting temperature is 95℃, and the holding time is 3s. The wind speed in the setting zone is controlled at 0.4m / s. The gradient slow cooling zone is divided into 5 independent temperature and humidity control sub-zones. The temperature is gradually reduced from 75℃ to room temperature at a rate of 8℃ / s, and the relative humidity of the environment is synchronously and linearly reduced from 60% to 45%. The cooling rate and dehumidification rate are kept synchronized, so that the moisture content of the material is always within the moisture absorption equilibrium range throughout the cooling process. The surface roughness of the cooling roller is Ra0.1μm, and the rotation speed of the cooling roller is consistent with the material feeding speed of the production line, with a speed deviation of ≤±0.05m / min.

[0076] Comparative Example 1: The only difference between this comparative example and Example 1 is that stress-luminescent microparticles are not added in step S1, and the heat-sealing layer is made of pure medical-grade polyolefin substrate directly through a casting process to form a heat-sealing film with a thickness of 45μm. The other steps and parameters are the same as in Example 1.

[0077] Comparative Example 2: The only difference between this comparative example and Example 1 is that the focused ultrasound vibration treatment is omitted in step S2, and the stress-inducing heat-sealing film after constant temperature conditioning is directly stacked with medical dialysis paper and enters step S3 for gradient heat sealing. The remaining steps and parameters are the same as in Example 1.

[0078] Comparative Example 3: The only difference between this comparative example and Example 1 is that: in step S3, the heat sealing mold uses a uniform temperature and the cavity surface is a smooth plane, there is no temperature gradient in the width direction of the mold sealing edge, the temperature of the entire sealing edge area is uniformly 160℃, and there is no micron-level protrusion density gradient on the cavity surface. The remaining steps and parameters are the same as in Example 1.

[0079] Comparative Example 4: The only difference between this comparative example and Example 1 is that the ultraviolet light source in step S4 adopts a continuous irradiation mode instead of a pulse mode, and the linear scan camera only acquires a single frame of bright field image. The acquisition and differential processing of bright field frames and dark field frames are not performed. The bright field image is directly used as the stress fluorescence image. The other steps and parameters are the same as in Example 1.

[0080] Comparative Example 5: The only difference between this comparative example and Example 1 is that in step S6, the heat-sealing mold does not divide the independent heating sections along the sealing edge length direction, and adopts an overall unified heating method. When a defect is detected, only the overall temperature baseline of the mold can be adjusted, and the temperature of local defects cannot be adjusted independently. The other steps and parameters are the same as in Example 1.

[0081] Comparative Example 6: This comparative example uses the existing publicly available method for producing medical paper-plastic sterile roll bags, namely, using a dry lamination process to prepare PET / PE composite film, using a multi-disc intermittent hot stamping knife to heat seal at 175°C for 1.5s, printing sterilization indicator ink on the front of the dialysis paper, without adding stress-luminescent microparticles, without focused ultrasonic zeroing and gradient heat sealing steps, without online spectral detection and closed-loop feedback control, and allowing natural cooling after heat sealing. The remaining production conditions are the same as in Example 1.

[0082] Experiment 1: Simultaneous testing of sealing defect detection rate and peel strength, according to the standard GB / T19633.1-2015 Terminally sterilized medical device packaging - Part 1: Requirements for materials, sterile barrier systems and packaging systems. 1000 medical packaging bags prepared in Examples 1-3 and Comparative Examples 1-6 were taken respectively. First, the intelligent diagnostic system of this application was used to perform online defect detection on all samples, recording the number of false sealing defects and over-sealing defects marked by the system. Then, all samples were re-inspected by manual visual inspection combined with the water immersion method, and the actual number of defects was counted. The defect detection rate and false judgment rate of each experimental group were calculated. Subsequently, 50 samples without obvious appearance defects were randomly selected from each experimental group, and the 180° peel strength of the sealing edge was tested according to the standard method. The peel strength value of each sample was recorded, and the average peel strength and peel strength variation coefficient were calculated. At the same time, the presence of paper scraps falling off the peel interface was observed.

[0083] Experiment 2: Long-term sealing stability test after sterilization. The test standard is "ISO 11607-1:2019 Terminally sterilized medical devices – Packaging – Part 1: Requirements for materials, sterile barrier systems and packaging systems". 200 medical packaging bags prepared in Examples 1-3 and Comparative Examples 1-6 were taken respectively. Each bag contained a simulant with a weight equivalent to that of a commonly used medical device. The bags were sterilized with ethylene oxide according to the standard requirements. After sterilization, the samples were placed in an environment of 25°C and 60% relative humidity for accelerated aging tests. 50 samples were taken at 0 months, 3 months, 6 months, and 12 months of aging. The sealing integrity of the seals was tested using the dye penetration method specified in the standard. The number of leaked samples at each time point was recorded, and the sealing integrity rate was calculated. Simultaneously, the peel strength of the seals at each time point was tested, and the change in peel strength with aging time was analyzed.

[0084] Experiment 3: In vitro cytotoxicity test. The test standard is GB / T16886.5-2017 Biological evaluation of medical devices - Part 5: In vitro cytotoxicity test. The heat-sealing film material of the medical packaging bags prepared in Examples 1-3 and Comparative Examples 1-6 were used to prepare extracts according to the standard method. The extraction medium was MEM medium containing 10% fetal bovine serum. The extraction conditions were 37℃ for 24h and the extraction ratio was 3cm2 / mL. Then, the cytotoxicity of the extract to L929 mouse fibroblasts was tested by the MTT assay. After culturing for 24h, the absorbance value of each well was measured at a wavelength of 570nm using an ELISA reader. The relative cell proliferation rate was calculated, and the cytotoxicity level was evaluated based on the relative cell proliferation rate. A blank control group and a positive control group were set up for parallel experiments.

[0085] Table 1: Detection rate of edge sealing defects and peel strength test results

[0086] Note: Comparative Example 1 does not incorporate stress-luminescent microparticles, so the heat-sealing film does not possess stress-luminescent properties and cannot be detected online; therefore, the defect detection rate is recorded as 0. Comparative Example 6 uses existing technical solutions and does not have online detection capabilities; therefore, the defect detection rate and false positive rate cannot be statistically analyzed and are represented by "—".

[0087] Table 2: Results of Accelerated Aging Sealing Stability Test After Sterilization

[0088] Note: * indicates that the sealing integrity rate has significantly fallen below the standard's 95% pass rate after 12 months, and the packaging bag's sealing performance no longer meets the requirements for use as medical sterile packaging.

[0089] Table 3: Results of in vitro cytotoxicity tests

[0090] Note: Cytotoxicity rating was based on the standard GB / T16886.5-2017: a relative cell proliferation rate ≥70% was grade 0 or 1, considered as acceptable for biocompatibility. The positive control group used MEM medium containing 0.1% zinc diethyldithiocarbamate.

[0091] As can be seen from Examples 1 to 3 and Comparative Example 1, and in conjunction with Tables 1-3, adding surface-modified stress-luminescent microparticles to the heat-sealing substrate is a fundamental condition for achieving online non-destructive testing of the sealing edge. These microparticles can generate corresponding fluorescence signals following changes in internal stress in the sealing area, and defect identification is achieved based on these fluorescence signals. Removing the stress-luminescent microparticles results in the film material losing its mechanoluminescence optical feedback capability, rendering the entire online fluorescence detection system unable to perform defect screening. Although the material's biocompatibility will not change significantly, and it will not directly affect the initial peel strength, latent defects during the production process cannot be detected in time. These latent defects will gradually manifest during long-term sterilization and aging storage, slowly causing a decline in sealing performance and accelerating the decay of peel strength.

[0092] As can be seen from Examples 1 to 3 and Comparative Example 2, and in conjunction with Tables 1-3, the focused ultrasonic zeroing process before heat sealing can clear the historical charge carriers remaining inside the stress-emitting microparticles, eliminate the residual luminescence signal corresponding to the residual stress from the previous processing, and ensure that the fluorescence generated during subsequent heat sealing is only generated by the newly formed stress at the sealing edge, avoiding interference from past stress in detection imaging. Eliminating the excess fluorescence background caused by residual past stress inside the microparticles after ultrasonic zeroing interferes with the system's criteria for judging true sealing edge defects. This not only lowers the accuracy of defect detection and increases the probability of false defect judgment, but the residual stress will also remain hidden inside the sealing edge, slowly releasing during long-term aging and storage, gradually damaging the sealing edge bonding structure and accelerating the decay rate of sealing performance and peel strength.

[0093] As can be seen from Examples 1 to 3 and Comparative Example 3, and Tables 1-3, setting a gradient temperature control along the sealing width, combined with micron-sized protrusions of gradually varying height on the mold surface, can create a pressure and temperature environment that changes smoothly from the inside to the outside in the sealing area. This adapts to the melting and bonding requirements of the membrane material and dialysis paper at different locations, allowing for a uniform transition of the sealing cohesion. After using a whole-body constant-temperature mold with a smooth cavity, the heating and pressure conditions across the entire sealing area tend to be uniform. This leads to two extreme problems: overheating and over-melting in the inner layer and insufficient melting in the outer layer. The uniformity of the sealing bond deteriorates significantly, resulting in a larger range of peel strength fluctuations. Dialysis paper fragments are also more likely to fall off during the peeling process, and a large number of hidden defects such as incomplete sealing and over-sealing persist. After ethylene oxide sterilization and long-term accelerated aging, the sealing bond structure deteriorates rapidly, and the sealing integrity declines significantly.

[0094] As can be seen from Examples 1 to 3 and Comparative Example 4, and in conjunction with Tables 1-3, the pulsed ultraviolet light source combined with the brightness-dark frame difference operation can eliminate the interference of thermal radiation stray light generated by the residual heat of the sealing edge, filter out irrelevant background signals, and retain only the effective fluorescence image brought about by stress, thereby improving the resolution of defect identification. After switching to a continuous light source and omitting the dark field difference processing, the thermal radiation stray light brought about by the high temperature of the sealing edge is mixed into the imaging image, and the effective fluorescence signal is covered and confused by background noise. The system has difficulty in accurately distinguishing between normal fluorescence and defect fluorescence, resulting in an increase in the problem of missed defects and misjudgments. Latent defects continue to remain in the finished product, and as the storage time goes by, the defects continue to deteriorate, gradually causing a decrease in sealing reliability and a continuous decline in peel strength.

[0095] As can be seen from Examples 1 to 3 and Comparative Example 5, and in conjunction with Tables 1-3, dividing the mold into multiple independent heating zones along its length allows for individual temperature adjustments to address local defects, enabling online repair of single-point defects and curbing the spread of small-scale flaws in batches. When the mold is modified to a unified overall temperature control structure, local defects can only be addressed by altering the overall mold's reference temperature. A single temperature adjustment can easily trigger new sealing defects in other acceptable sections, making it impossible to accurately repair single-point defects. Unrepaired local defects remain inside the finished product, continuously expanding in the sterilization and aging environment, gradually reducing the long-term sealing stability of the entire batch and accelerating the deterioration of sealing performance.

[0096] Combining Examples 1 to 3 and Comparative Example 6 with Tables 1-3, it can be seen that the entire process involves multiple steps such as stress-sensitive film preparation, ultrasonic pre-zeroing, gradient hot pressing, differential spectroscopy detection, segmented temperature control closed-loop correction, and gradient slow cooling working together to optimize the internal adhesive structure of the edge seal throughout the entire process from raw materials, molding, online quality control, and shaping. Existing conventional processes, after omitting all the special steps, lack visual stress detection and real-time closed-loop correction methods. The edge seal molding lacks gradient adaptation design under heat and pressure, and the cooling method cannot balance changes in the internal moisture content of the material. This results in poor edge seal adhesion consistency, a higher base of inherent defects in the finished product, rapid failure of the adhesive interface after sterilization and long-term aging, and a significant increase in the attenuation of sealing integrity and peel strength. Simultaneously, differences in substrate formulation and processing technology can slightly alter the biocompatibility of the material.

[0097] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A continuous heat-sealing process for medical packaging bags, characterized in that: Includes the following steps: S1. Stress film material preparation: Medical-grade polyolefin substrate is selected, and non-migratory and biocompatible stress-luminescent microparticles are incorporated to prepare a stress-sensitive heat-sealing film with stress-luminescent properties. S2, Conditioning and Ultrasonic Zeroing: After unwinding the stress-sensitive heat-sealing film and medical dialysis paper, the film is conditioned at a constant temperature. Then, focused ultrasonic vibration is applied to the heat-sealed area to clear the carrier traps of the stress-luminescent microparticles, thus returning their force-light response history to zero. S3, Gradient hot-press sealing: The stacked materials are fed into a special-shaped hot-pressing mold with a continuous gradient structure. The mold has a temperature gradient zone with decreasing temperature in the sealing width direction. The cavity surface has micron-level protrusions to form a pressure gradient. Hot pressing forms a continuous and gradually changing cohesive gradient band. S4. Differential spectroscopy detection: Immediately following the heat sealing station, while there is residual heat at the sealing edge, a pulsed ultraviolet light source and a linear scanning camera are used to simultaneously acquire bright field frames and dark field frames. The thermal radiation background signal contained in the dark field frame is removed from the bright field frame to obtain a pure stress fluorescence image. S5. Intelligent Diagnosis and Judgment: Using a spectral band with fluorescence intensity that decreases continuously and smoothly from the inside to the outside as the qualification criterion, it identifies false sealing and over-sealing defects and generates a judgment signal; S6. Defect closed-loop feedback: The judgment signal is fed back to the heat sealing mold. The mold is equipped with multiple independent heating sections along the sealing edge length. The temperature of the corresponding section is automatically adjusted according to the defect to carry out online repair and remove defects that cannot be repaired. S7. Constant Temperature Slow Cooling and Shaping: Qualified edge banding does not leave the production line. It is first shaped at a constant temperature, and then cooled in a dual gradient of temperature and humidity.

2. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S1, the stress-luminescent microparticles are sulfoxylates or rare earth-doped aluminates that have been passivated on the surface of silica or medical-grade silane coupling agent, with a doping mass percentage of 0.5%-5%.

3. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S1, the thickness of the stress-sensitive heat-sealing film is 30μm-60μm. It is transparent or semi-transparent under normal conditions, and emits visible fluorescence only when subjected to tensile or shear stress exceeding a preset stress threshold under ultraviolet light excitation.

4. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S2, the temperature of the constant temperature conditioning is 45℃-55℃, the time is 3s-5s, and the moisture content of the material is controlled at 4%-6%; the frequency of the focused ultrasonic vibration is 20kHz-50kHz, the power density is 0.1W / cm²-0.5W / cm², and the action time is 0.5s-1.5s.

5. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S3, the high temperature inside the gradient temperature zone is 175℃-200℃, and the low temperature outside is 120℃-140℃, with the temperature decreasing linearly or stepwise; the heat sealing time is 1.0s-2.0s, and the cohesive gradient band width is 3mm-8mm.

6. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S4, the wavelength of the pulsed ultraviolet light source is 360nm-400nm, and the single pulse width is 10μs-50μs; the edge sealing residual temperature is 60℃-100℃.

7. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S5, a preset upper and lower threshold for fluorescence intensity is used to automatically mark defects. The upper threshold corresponds to the material damage state, and the lower threshold corresponds to the false sealing state. The threshold is preset based on the calibration curve of stress fluorescence intensity and peel strength.

8. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S6, the number of independent heating sections is no less than three; when a false sealing feature is detected, the mold temperature of the section is increased by 1℃-5℃, and when an over-sealing feature is detected, the mold temperature of the section is decreased by 1℃-5℃; when more than a preset proportion of the same type of defect is continuously detected, the overall mold temperature baseline, heat sealing time, or film unwinding tension is automatically adjusted.

9. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S7, the temperature for constant temperature shaping is 85℃-95℃, and the holding time is 2s-3s.

10. The continuous heat-sealing process for a medical packaging bag according to claim 1, characterized in that: In step S7, the temperature in the gradient slow cooling process is gradually reduced from 65℃-75℃ to room temperature at a rate of 3℃ / s-8℃ / s, and the relative humidity of the environment is simultaneously and linearly reduced from 50%-60% to 35%-45%. The cooling rate and the dehumidification rate are kept synchronized, so that the moisture content of the material is always within the moisture absorption equilibrium range throughout the cooling process.

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