Pre-treatment process in 3d curved surface molding material production

Abstract

The present application relates to the field of forming material pretreatment, and discloses a pretreatment process in 3D curved surface forming material production, which comprises conveying a composite film composed of a bio-based polyester base material and an aqueous adhesive layer, establishing an asymmetric temperature and humidity field, using a heating roller to conduct heat to the adhesive-free surface of the base material, spraying a wet and hot laminar flow to the surface of the adhesive layer to maintain a semi-swollen state, using a pulsating airflow with a modulation frequency of 10 Hz to 15 Hz to generate a periodic normal pressure stress, pressing the molecular chain segments of the adhesive layer into the intermolecular gaps of the base material surface to construct a mechanical locking structure, and independently regulating the heat conduction of the base material and the moisture migration of the adhesive layer, eliminating the internal stress of the material processing and inhibiting the hardening and skinning of the adhesive layer, inducing a deep anchoring of the heterogeneous interface through physical momentum transfer, and effectively enhancing the interface bonding stability of the composite material under three-dimensional high-multiplying stretching conditions.

Description

Technical Field

[0001] This invention relates to a pretreatment process in the production of 3D curved surface molding materials, belonging to the field of molding material pretreatment technology. Background Technology

[0002] Currently, the combination of bio-based polyester composite films and water-based adhesives is the mainstream material configuration. Before the molding material enters the mold, it is usually pretreated by a thermal field to adjust the rheological properties of the substrate molecular chain, so that it can be relaxed to adapt to high-ratio geometric stretching. Bio-based materials such as PETG and PLA have physical properties of high rigidity and narrow thermal stability range. The thermal process required to eliminate the residual stress of the substrate processing often causes excessive water migration of the surface water-based adhesive. This premature water loss caused by heat reduces the wetting performance of the adhesive layer and causes interface failure defects such as blistering and peeling in the subsequent molding process.

[0003] Extending the dwell time in the low-temperature field or increasing the instantaneous heating power makes it difficult to simultaneously achieve deep heat penetration into the substrate and maintain the moisture content of the adhesive layer. The former causes the adhesive layer to lose its cohesive strength due to drying; the latter, due to the thermal resistance limitation in the thickness direction of the material, leads to local thermal degradation of the coated surface before the stress in the core layer of the substrate is released. This processing mode based on a uniform thermophysical field presents a physical conflict between substrate stress relaxation and interfacial activity maintenance. Specifically, the existing technology has the following shortcomings: 1. The uniform thermal field cannot distinguish the energy demand in the thickness direction, resulting in an imbalance between the release of substrate strain energy and the maintenance of adhesive layer wettability; 2. The interfacial activation mechanism relying on a single heat conduction is prone to inducing thermal damage to the adhesive layer, reducing the interfacial bonding strength of the composite material; 3. The static pretreatment environment lacks dynamic mechanical intervention, making it difficult to form a stable physical anchoring structure in complex curved surface stretching.

[0004] Therefore, how to construct an asymmetric physical control mechanism that can ensure the isothermal relaxation of the substrate molecular chains to eliminate thermal memory, while blocking the loss of moisture from the adhesive layer and strengthening the interfacial physical interlocking strength, is the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: a pretreatment process for the production of 3D curved surface molding materials, comprising the following steps: Step 101: Convey a bio-based polyester composite film along a preset path. The bio-based polyester composite film includes a bio-based polyester substrate and an aqueous adhesive layer coated on the surface of the bio-based polyester substrate. Step 102: Establish an asymmetric temperature and humidity field. Use a heated roller to contact the adhesive-free surface of the bio-based polyester substrate to conduct heat and make the bio-based polyester substrate reach a high elastic state. Simultaneously spray a humid laminar flow airflow onto the surface of the water-based adhesive layer. The humid laminar flow airflow increases the partial pressure of water vapor in the environment above the water-based adhesive layer and maintains the water-based adhesive layer in a semi-swollen state. Step 103, Pulsating pneumatic compression, a pulsating airflow with a modulation frequency of 10Hz to 15Hz is applied to the water-based adhesive layer in a semi-swollen state. The periodic normal compressive stress generated by the pulsating airflow is used to press the molecular chains of the water-based adhesive layer into the surface molecular gaps generated by the thermal expansion of the bio-based polyester substrate in a highly elastic state, forming a mechanically locked structure. In steps 102 and 103, the bio-based polyester composite film operates continuously, and the asymmetric temperature and humidity field and the pulsating airflow work together to make the bio-based polyester composite film reach stress balance before molding and the heterogeneous interface has physical anchoring activity.

[0006] Preferably, in step 102, the surface temperature of the heating roller is 75°C to 95°C, and the bonding and wrapping angle of the bio-based polyester substrate on the heating roller is 120° to 180°, so as to eliminate internal residual stress by thermal relaxation of the bio-based polyester substrate.

[0007] Preferably, in step 102, the absolute humidity of the humid laminar flow is 18 g / kg to 25 g / kg, and the absolute value of the temperature difference between the humid laminar flow and the surface temperature of the heating roller is not greater than 5 g / kg. By reducing the humidity gradient between the water-based adhesive layer and its surface environment, the diffusion of moisture within the water-based adhesive layer is inhibited.

[0008] Preferably, step 103 specifically includes: using a rotary shut-off valve to periodically modulate the airflow output from the constant pressure gas source to generate a pulsating airflow with a dynamic pressure wave peak value of 0.15 MPa and a dynamic pressure wave trough value of 0.05 MPa, and using the momentum transfer of pressure fluctuations to drive the water-based adhesive layer to move into the interior of the bio-based polyester substrate.

[0009] Preferably, the thickness of the water-based adhesive layer is 5 μm to 15 μm, and after step 103, the physical anchoring depth of the mechanical locking structure on the surface of the bio-based polyester substrate is not less than 0.5 μm.

[0010] Preferably, the bio-based polyester substrate is polyethylene terephthalate-1,4-cyclohexanediol ester or polylactic acid, and the bio-based polyester composite film is heated and held in an asymmetric temperature and humidity field for 15 to 25 seconds.

[0011] Preferably, step 103 is followed by step 104: online tension compensation feedback, monitoring the real-time tension value of the bio-based polyester composite film, and adjusting the conveying rate in step 101 according to the deviation between the real-time tension value and the initial set value, so as to maintain the interface force balance before the mechanical locking structure is locked.

[0012] Preferably, in step 102, the spraying direction of the humid laminar airflow is at 30° to 45° with the running direction of the bio-based polyester composite film, so as to form a micro-positive pressure coverage area on the surface of the water-based adhesive layer to prevent external air from penetrating.

[0013] Preferably, after step 104, the method further includes: cooling the adhesive-free surface of the bio-based polyester composite film with cold air to reduce the temperature of the bio-based polyester substrate to below its glass transition temperature, and locking the molecular chains of the water-based adhesive layer embedded therein through the thermal shrinkage of the bio-based polyester substrate to complete the interface pretreatment.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. An asymmetric physical field is established to achieve independent control of thermal conduction in the bottom layer and proton migration in the top layer of the composite film. Direct conduction heating on the adhesive-free surface drives the molecular chains of the polyester substrate to fully relax. Simultaneously, a physical isolation barrier is constructed using a humid laminar flow air curtain above the adhesive-coated surface to inhibit excessive moisture loss of the water-based adhesive during the pretreatment stage. This method eliminates the underlying physical constraints between substrate stress release and adhesive wetting performance maintenance under a traditional uniform thermal field, ensuring that the composite material is in a quasi-equilibrium state with isotropic stress and highly active interfaces before entering the subsequent molding station.

[0015] 2. By using the periodic normal compressive stress generated by the alternating pulsating air curtain, dynamic pneumatic compression is applied to the semi-swollen water-based adhesive layer, inducing the flexible segments of the adhesive to penetrate into the free volume of the substrate surface as it expands due to heat. The momentum transfer generated by the alternating dynamic pressure field replaces the thermal phase change excitation, avoiding damage to the cohesive strength of the adhesive layer and the residue of microscopic voids caused by the transient vaporization of moisture. This mechanical interlocking mechanism enhances the physical interlocking depth between heterogeneous interfaces, enabling the composite material to have a synergistic stress transmission network when subjected to three-dimensional high-ratio geometric stretching, reducing the probability of peeling or blistering at the molding corners.

[0016] 3. Based on the spatiotemporal synergistic regulation of material thermodynamic characteristics and interfacial rheological properties, the adaptability and stability of bio-based composite films to environmental fluctuations and batch-to-batch material differences are improved. The temperature gradient regulation and pulse-assisted activation in the pretreatment process are coupled to achieve dynamic matching between the macroscopic deformation modulus and microscopic interfacial activity of the composite material. This integrated scheme uses pneumatic mechanical work to compensate for the kinetic obstacles in the heat treatment process, and achieves structural widening of the material's processability window without destroying the original structural characteristics of the material, thus meeting the process robustness requirements of industrial-scale continuous production. Attached Figure Description

[0017] Figure 1 This is a flowchart of the multi-dimensional collaborative process for 3D curved surface material pretreatment according to the present invention; Figure 2 This is a diagram of the asymmetric physical field and state-aware control architecture of the preprocessing system of the present invention.

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

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

[0020] A pretreatment process for the production of 3D curved surface molding materials includes the following steps: Step 101: Convey a bio-based polyester composite film along a preset path. The bio-based polyester composite film includes a bio-based polyester substrate and an aqueous adhesive layer coated on the surface of the bio-based polyester substrate. Step 102: Establish an asymmetric temperature and humidity field. Use a heated roller to contact the adhesive-free surface of the bio-based polyester substrate to conduct heat and make the bio-based polyester substrate reach a high elastic state. Simultaneously spray a humid laminar flow airflow onto the surface of the water-based adhesive layer. The humid laminar flow airflow increases the partial pressure of water vapor in the environment above the water-based adhesive layer and maintains the water-based adhesive layer in a semi-swollen state. Step 103, Pulsating pneumatic compression, a pulsating airflow with a modulation frequency of 10Hz to 15Hz is applied to the water-based adhesive layer in a semi-swollen state. The periodic normal compressive stress generated by the pulsating airflow is used to press the molecular chains of the water-based adhesive layer into the surface molecular gaps generated by the thermal expansion of the bio-based polyester substrate in a highly elastic state, forming a mechanically locked structure. In steps 102 and 103, the bio-based polyester composite film operates continuously, and the asymmetric temperature and humidity field and the pulsating airflow work together to make the bio-based polyester composite film reach stress balance before molding and the heterogeneous interface has physical anchoring activity.

[0021] Preferably, in step 102, the surface temperature of the heating roller is 75°C to 95°C, and the bonding and wrapping angle of the bio-based polyester substrate on the heating roller is 120° to 180°, so as to eliminate internal residual stress by thermal relaxation of the bio-based polyester substrate.

[0022] Preferably, in step 102, the absolute humidity of the humid laminar flow is 18 g / kg to 25 g / kg, and the absolute value of the temperature difference between the humid laminar flow and the surface temperature of the heating roller is not greater than 5 g / kg. By reducing the humidity gradient between the water-based adhesive layer and its surface environment, the diffusion of moisture within the water-based adhesive layer is inhibited.

[0023] Preferably, step 103 specifically includes: using a rotary shut-off valve to periodically modulate the airflow output from the constant pressure gas source to generate a pulsating airflow with a dynamic pressure wave peak value of 0.15 MPa and a dynamic pressure wave trough value of 0.05 MPa, and using the momentum transfer of pressure fluctuations to drive the water-based adhesive layer to move into the interior of the bio-based polyester substrate.

[0024] Preferably, the thickness of the water-based adhesive layer is 5 μm to 15 μm, and after step 103, the physical anchoring depth of the mechanical locking structure on the surface of the bio-based polyester substrate is not less than 0.5 μm.

[0025] Preferably, the bio-based polyester substrate is polyethylene terephthalate-1,4-cyclohexanediol ester or polylactic acid, and the bio-based polyester composite film is heated and held in an asymmetric temperature and humidity field for 15 to 25 seconds.

[0026] Preferably, step 103 is followed by step 104: online tension compensation feedback, monitoring the real-time tension value of the bio-based polyester composite film, and adjusting the conveying rate in step 101 according to the deviation between the real-time tension value and the initial set value, so as to maintain the interface force balance before the mechanical locking structure is locked.

[0027] Preferably, in step 102, the spraying direction of the humid laminar airflow is at 30° to 45° with the running direction of the bio-based polyester composite film, so as to form a micro-positive pressure coverage area on the surface of the water-based adhesive layer to prevent external air from penetrating.

[0028] Preferably, after step 104, the method further includes: cooling the adhesive-free surface of the bio-based polyester composite film with cold air to reduce the temperature of the bio-based polyester substrate to below its glass transition temperature, and locking the molecular chains of the water-based adhesive layer embedded therein through the thermal shrinkage of the bio-based polyester substrate to complete the interface pretreatment.

[0029] Example 1: In the continuous molding production of 3D curved trim parts for new energy vehicles, when a composite film composed of a bio-based polyester substrate and a water-based adhesive layer is conveyed and subjected to stretching deformation, the bio-based polyester substrate has high molecular chain rigidity and a limited thermal stability window, requiring the accumulation of heat energy to release internal orientation stress. Simultaneously, the water-based adhesive layer experiences accelerated moisture evaporation under heated conditions, leading to layer cross-linking or surface hardening. Under uniform thermal field treatment conditions, the release of residual stress inside the substrate and the excessive water loss and loss of adhesive activity of the adhesive layer occur simultaneously, resulting in interlayer separation and localized blistering in the subsequent stretching stress area. To suppress the mutual constraints of the aforementioned material properties, the bio-based polyester composite film is continuously conveyed along a preset path and introduced into an asymmetric temperature and humidity field for independent thermo-mass control. An asymmetric temperature and humidity field is established by using a heated roller with a surface temperature between 75°C and 95°C to contact the adhesive-free surface of the bio-based polyester substrate for unidirectional heat conduction, allowing the segments of the bio-based polyester substrate to acquire thermal energy and reach a highly elastic state. Simultaneously, a humid laminar flow is continuously sprayed onto the surface of the water-based adhesive layer. The absolute humidity of this humid laminar flow is between 18 g / kg and 25 g / kg, and the absolute value of the temperature difference between this flow and the surface temperature of the heated roller is no greater than 5°C. The flow field coordination is achieved based on a multi-layered metal rectifier mesh inside the nozzle, which dampens and homogenizes the initial high-speed airflow to form a stable laminar flow field with a Reynolds number below 2000. In the actual nozzle structure design, this multi-layered metal rectifier mesh is specifically composed of three layers of finely textured stainless steel wire mesh arranged sequentially along the airflow direction. Among them, along the direction from the airflow inlet to the nozzle outlet, the first layer is an 80-mesh coarse filter pressure equalization mesh, used to disperse the local concentrated momentum of the initial high-pressure airflow; the second layer is a 200-mesh intermediate rectifier mesh spaced 5mm apart along the outlet direction, used to initially streamline the airflow and generate uniform damping; the third layer is a 400-mesh intermediate rectifier mesh spaced adjacent to the nozzle outlet. A high-precision rectifier mesh, through further laminarization and damping of the fine mesh openings, eliminates microscopic eddies and velocity gradients within the fluid, ensuring that the gas, after leaving the nozzle, covers the film surface in a uniform, parallel streamline state. Against this background flow field, a rotary cut-off valve installed in the gas supply branch periodically regulates the total pressure, generating frequency-controlled static pressure pulsations on the time axis while maintaining a consistent spatial distribution of the laminar air curtain. This achieves the application of periodic momentum impacts to the adhesive surface while maintaining stable water vapor partial pressure. The humid, hot laminar airflow increases the water vapor partial pressure in the region above the water-based adhesive layer, inhibiting internal moisture diffusion and maintaining... The water-holding adhesive layer is in a semi-swollen state. In specific fluid dynamics control, although the peak pressure of the pulsating airflow reaches 0.15 MPa, the periodic throttling modulation of the rotary throttling valve only changes the mass flow rate and pressure amplitude of the airflow, without changing the streamline parallelism of the gas after being stabilized by the multi-layer rectifier wire mesh of the nozzle. Therefore, the ejected airflow always maintains a quasi-laminar boundary layer structure with a Reynolds number below 2000 in space. This static pressure fluctuation in the time dimension and the laminar morphology in the spatial dimension are in a spatiotemporal orthogonal state, that is, the airflow maintains a layered parallel flow in the delivery direction to block the mixing of external air and lock the high water vapor partial pressure on the surface of the adhesive layer, while the overall air curtain acts as... As a quasi-static pressure barrier, dynamic pressure fluctuations are synchronously generated over time in the normal direction, preventing shear instability and turbulent collapse in the low Reynolds number humid heat concentration boundary layer, thus successfully applying periodic mechanical stress while maintaining the moisture isolation effect. In the dynamic evolution of the hydrodynamic boundary layer, to ensure that parallel laminar streamlines with Reynolds numbers below 2000 do not experience shear instability caused by high-frequency pressure changes, a rotary shut-off valve is used to implement in-phase, homogenized overall shut-off modulation on the main gas source pipeline, ensuring that the static pressure fluctuations before the airflow enters the multi-layer rectifying wire mesh of the nozzle remain completely equipotential in the lateral width. When the dynamic pressure is between 0.05 MPa and 0.When the pressure periodically jumps between 15 MPa and the time axis, the gas only experiences fluctuations in overall mass flow rate and static pressure potential energy in the direction perpendicular to the film surface, while the tangential shear velocity gradient of the fluid parallel to the film's running direction remains zero, thus eliminating the tangential shear stress and microscopic velocity pulsations that induce turbulence transition. Because there is no generation of tangential eddies, gas molecules maintain a uniform, parallel streamline state covering the adhesive layer surface, ensuring that the local Reynolds number within the concentration boundary layer is consistently suppressed within the absolutely safe steady-state range of 1200 to 1450. This achieves lossless transfer of macroscopic mechanical high-frequency pulsating energy to the interface without damaging the vapor barrier. When applied to the semi-swollen aqueous adhesive layer... A pulsating airflow is applied, with a modulation frequency between 10Hz and 15Hz, a peak dynamic pressure wave of 0.15MPa, and a trough dynamic pressure wave of 0.05MPa. The periodic normal compressive stress generated by the pulsating airflow transfers physical momentum to the interface, pressing the molecular chains of the semi-swollen aqueous adhesive layer into the surface molecular gaps generated by the thermal expansion of the highly elastic bio-based polyester substrate. When the pulsating airflow with a frequency of 10Hz to 15Hz acts on the macroscopic continuous medium space of the adhesive layer surface, the cyclic dynamic pressure of 0.05MPa to 0.15MPa generated is transmitted as a normal shear wave through the viscoelastic fluid medium layer of the semi-swollen adhesive layer. Due to the semi-swollen adhesive layer... It possesses both macroscopic fluid flow characteristics and microscopic relaxation characteristics. Macroscopic pulsating kinetic energy is converted into local instantaneous static pressure gradient, thereby overcoming the contact orientation displacement resistance at the interface between the water-based adhesive and the high-elasticity substrate. As the substrate is in a state of thermal expansion, the free volume between its molecules expands, and the resulting surface micro-molecular gaps are on the nanoscale. The thermal relaxation time of the semi-swollen polymer chain segments and the period of the pulsating wave achieve a dynamic coupling between the macroscopic and microscopic dimensions on the rheological characteristic time scale. This allows the shear dynamics of the pulsating pressure wave peak to directly drive the adhesive chain segments to undergo viscous flow along the free volume direction in each cycle, thus completing the cross-scale physical leap from macroscopic mechanical energy to the interfacial micro-molecular interpenetration mechanical locking structure. The reason why low-frequency dynamic fluctuations at the macroscopic level can drive deep interpenetration of microscopic molecular chain segments is that, under the thermal conduction effect of 75℃ to 95℃, the molecular chain segments on the surface of the bio-based polyester substrate in a highly elastic state obtain sufficient unentanglement activation energy, and its relaxation time is shortened to 60ms to 100ms. This resonates with the 66ms to 100ms pressure fluctuation period corresponding to the 10Hz to 15Hz pulsating airflow on the time scale. When the dynamic pressure wave peak of 0.15MPa acts on the surface of the water-based adhesive layer with a thickness of 5μm to 15μm, the macroscopic gas kinetic energy is conducted downward through the viscoelastic medium layer of the semi-swollen adhesive layer, establishing a pressure of 0.01MPa to 0.15MPa per micrometer inside it.A normal micro-pressure gradient of 0.2 MPa, this localized stress concentration overcomes the non-covalent repulsion barrier of polymers between heterogeneous interfaces. Within each pulse cycle, it induces synergistic deformation and rheology of the adhesive's flexible segments along the direction of the heated nanoscale pores on the substrate surface. This allows macroscopic mechanical work to be efficiently converted into directional slippage of the interfacial micro-molecular segments through scale matching of relaxation time, achieving deep physical integration that is unattainable at room temperature and under conventional conditions.

[0030] In actual physical processes, the free volume between molecular chains of the waterborne adhesive layer in a semi-swollen state increases due to the penetration of solvent molecules, reducing the resistance to cooperative motion of chain segments. When the dynamic pressure wave formed by the pulsating airflow contacts the adhesive layer surface, it converts macroscopic kinetic energy into an instantaneous pressure gradient acting on the liquid film surface through the laminar boundary layer. This pressure gradient induces local fluid orientation displacement in the adhesive layer at the micrometer scale, driving rheologically active polymer chains to overcome surface tension and sequentially enter the molecular gaps generated by the thermal expansion of the substrate. This completes the conversion of momentum into interfacial penetration depth at the microscopic level. Pneumatic mechanical compressive stress replaces the heating phase change, thereby inhibiting water vaporization and the formation of intralayer pores. The unidirectional heat transfer and physical isolation in the asymmetric temperature and humidity field, combined with the pulsating air pressure physical extrusion, ensure that the bio-based polyester substrate and the waterborne adhesive layer remain in a stable state without any changes. The bio-based polyester composite film achieves interfacial physical interlocking under thermal degradation conditions. It operates continuously, remaining within a region of synergistic effect between an asymmetric temperature and humidity field and pulsating airflow for 15 to 25 seconds, cooling to below the glass transition temperature of the corresponding material. After undergoing the aforementioned independent thermo-mass regulation and cyclic compression process, the orientation stress within the bio-based polyester composite film is released, and the bio-based polyester substrate shrinks in volume due to cooling. This, in turn, clamps and fixes the molecular chain segments of the water-based adhesive layer embedded in the intermolecular gaps on its surface with a depth greater than or equal to 0.5 μm, forming an interlayer physical locking structure. Under the tensile stress conditions of the subsequent three-dimensional molding die, the deformation stress between the two layers is conducted and dispersed through this physical locking structure, maintaining the adhesion state of the substrate and adhesive layer interface and the consistency of deformation dimensions in the local stress areas.

[0031] Example 2: The experiment was conducted on a continuous roll-to-roll coating and pretreatment test platform. This platform integrates a high-frequency dynamic tension sensor with a measurement resolution of 0.01N and an online infrared moisture analyzer with a sampling frequency of 100Hz to acquire raw process data. In actual control, the specific execution path of online tension compensation feedback is as follows: the high-frequency dynamic tension sensor collects the real-time tension value of the conveyed film at a frequency of 10Hz. The main control unit calculates the algebraic deviation between the tension value and the system's preset initial setting value in real time and converts the tension deviation into a speed correction command for the servo drive. When the detected real-time tension value is greater than the initial setting value, it indicates that the film tension is too high due to thermal shrinkage or conveying synchronization error. The main control unit issues an acceleration command to control the conveyor motor speed to be adjusted upwards slightly to increase the film feed and reduce tension. Conversely, when the real-time tension value is lower than the initial setting value, a deceleration command is issued to control the conveyor motor to reduce its speed to tighten the film. In this way, the tension of the film dynamically returns to the initial setting state through closed-loop negative feedback adjustment, ensuring that the interface deformation of the mechanical locking structure will not be affected by excessive tension before cooling and setting. This can lead to mechanical tearing or misalignment. The proportional-integral feedback control mechanism performs a speed correction calculation every 100ms via the main control unit's digital signal processor. Its input format is a 16-bit high-precision tension digital signal. When the real-time tension value acquired by the high-frequency dynamic tension sensor exceeds the initial set value of 10N and the deviation reaches 0.5N, the main control unit converts this tension deviation into a pulse frequency adjustment for the servo driver through a preset gain coefficient. This adjustment is then output to the drive input of the conveyor motor in increments of 10 pulses per second, adjusting the rated torque of the conveyor motor. The rotation speed is finely adjusted from 15.0 revolutions per minute to 15.3 revolutions per minute, thereby increasing the film feed to release excessive tension. Conversely, when the real-time tension value is detected to be 0.5N lower than the initial set value, the main control unit outputs a proportionally decreasing pulse frequency, causing the rated speed of the conveyor motor to be finely adjusted downward to 14.7 revolutions per minute to tighten the film and prevent interface misalignment, ensuring that the real-time tension deviation is always locked within the allowable tolerance range of ±0.1N. This is designed for industrial production environments where crosswinds cause an absolute humidity fluctuation of 2%.The calibration basis for determining the modulation frequency of the pulsed airflow under the objective condition of local fluctuation interference of 5 g / kg lies in balancing the mechanical relaxation time of polymer chain segments and the input power load of the air source equipment. As the target penetration depth increases, the corresponding modulation frequency needs to approach the lower limit of the range to ensure sufficient kinetic energy transfer in a single cycle. Therefore, 12 Hz was selected as the baseline test value. A control group was set up using conventional uniform thermal field treatment without aerodynamic compression; a partially missing control group was set up with an asymmetric temperature and humidity field but lacking pulsed airflow compression; a first test group was set up using a modulation frequency of 12 Hz; a second test group was set up using a modulation frequency of 10 Hz; a third test group was set up using a modulation frequency of 15 Hz; and out-of-range control groups were set up with modulation frequencies of 5 Hz and 25 Hz. For each group, a bio-based polyester composite film with a uniform thickness and a surface coated with a water-based adhesive layer was selected as the treatment entity.

[0032] The conveying mechanism was activated to guide each group of composite films into their respective processing areas. After heating, the control group showed a residual moisture retention rate of 12.4% for the surface water-based adhesive layer, as recorded by an online moisture analyzer, and an interlayer peel strength of 1.2 N / mm as output by the deep cavity tensile test. The partially missing control group, isolated by laminar airflow in an asymmetric temperature and humidity field, maintained a residual moisture retention rate of 85.1%, and an interlayer peel strength of 2.5 N / mm as recorded by a high-frequency dynamic tension sensor. When faced with fluctuations in ambient crosswind humidity, each experimental group maintained a moisture retention rate around 88.5% by continuously spraying a humid laminar airflow with an absolute humidity of 21 g / kg to stabilize the upper water vapor partial pressure. The first experimental group used a peak pressure of 0.15 MPa and a trough pressure of 0.05 MPa. The 12Hz pulsating airflow generated periodic normal compressive stress, which pressed the molecular chains of the water-based adhesive layer into the intermolecular gaps on the surface of the bio-based polyester substrate in a highly elastic state, increasing the output interlayer peel strength to 5.8 N / mm; the second test group used a 10Hz pulsating airflow, with an output interlayer peel strength of 5.2 N / mm; the third test group used a 15Hz pulsating airflow, with an output interlayer peel strength of 5.5 N / mm; the out-of-range control group with a modulation frequency set to 5Hz had an output interlayer peel strength of 3.1 N / mm due to insufficient momentum transfer frequency per unit time; the out-of-range control group with a modulation frequency set to 25Hz induced high-frequency fatigue and microcrack deterioration on the surface of the water-based adhesive layer, and the output interlayer peel strength decreased to 2.2 N / mm.

[0033] The above process data show the nonlinear evolution law of interfacial cohesive strength within the frequency window of 10Hz to 15Hz; various monitoring values ​​confirm that there is a positive feedback synergy between the interfacial moisture maintenance state provided by the asymmetric temperature and humidity field and the momentum transfer action provided by the pulsating airflow; the system uses mechanical compressive stress in a limited frequency band to replace thermal phase change activation, eliminates the interference of environmental humidity fluctuations, and constructs an interlayer physical locking structure without inducing thermal degradation of the bio-based polyester substrate and skinning of the water-based adhesive layer, thus establishing a quantitative process boundary suitable for three-dimensional high-ratio stretching molding conditions.

[0034] Example 3: Before replacing batches of bio-based polyester substrates with different initial crystallinity and putting them into continuous production, establish a pulsed airflow modulation frequency suitable for the current substrate characteristics and apply standardized parameter calibration procedures; select a bio-based polyester composite film sample to be processed and place it at a surface temperature constant of 85°C. In an asymmetric temperature and humidity field with a constant absolute humidity of 21 g / kg, the thermo-mass state of the composite film was controlled; the peak value of the dynamic pressure wave of the pulsating airflow was maintained at 0.15 MPa and the trough value of the dynamic pressure wave was 0.05 MPa, and the test frequency was set to be distributed in the range of 5 Hz to 20 Hz. Periodic normal compressive stress of different frequencies was applied to each group of samples with a step size of 1 Hz; after each group of samples was cooled to room temperature, a cross-section was cut along the material transport direction, and the cross-sectional morphology was observed using a scanning electron microscope to measure the vertical penetration depth of the molecular chain segments of the water-based adhesive layer embedded in the molecular gaps on the surface of the bio-based polyester substrate; at the same time, the substrate surface deformation rate of the corresponding sample was measured using an optical three-dimensional profilometer.

[0035] Based on the measured output data, a parameter screening logic was established to eliminate test groups with a substrate surface deformation rate greater than 2%, thus controlling the material's appearance flatness. Among the remaining test groups, a sample set with a vertical penetration depth greater than or equal to 0.5 μm was selected. Comparing the frequency input values ​​corresponding to this sample set, the measured data showed a corresponding pattern: in test groups with frequencies less than 10 Hz, the vertical penetration depth was less than 0.3 μm; in test groups with frequencies greater than 15 Hz, the substrate surface deformation rate increased and exceeded the 2% tolerance limit. The test group with the maximum vertical penetration depth in the sample set was selected, and the corresponding frequency value was extracted as the production control frequency for the current batch of materials. This calibration procedure transforms the pulsating frequency setting process into a programmed calculation based on microstructure observation and deformation tolerance constraints, establishing a quantitative physical basis for the formation of interlayer physical interlocking structures.

[0036] Example 4: Under fluctuating temperature and humidity conditions in the workshop environment, a dew point meter placed above the conveyor belt of the bio-based polyester composite film is used to obtain the real-time absolute humidity output by the airflow generator. Simultaneously, the surface temperature fed back by the heating roller is obtained. Adjust the opening of the mixing valve to regulate the mixing ratio of dry air and water vapor, and simultaneously adjust the output power of the heating element until the absolute humidity is reached. The airflow temperature is in the range of 18g / kg to 25g / kg and the output airflow temperature of the airflow generator is... With surface temperature absolute value of the difference No more than 5 The opening degree of the mixing valve and the output power of the heating component at this time are set as the initial feedforward parameters and written into the memory.

[0037] During the continuous transport of the bio-based polyester composite film, a dew point meter acquires environmental parameters in real time, and the absolute humidity is measured. When the deviation from the reference value corresponding to the initial feedforward parameter is detected, the main control unit generates a dynamic compensation coefficient based on the humidity deviation. The opening of the mixing valve is adjusted according to the dynamic compensation coefficient to correct the water vapor injection amount. The duty cycle of the heating component is adjusted simultaneously to maintain the constant enthalpy of the airflow. Feedback adjustment is used to compensate for the temperature and humidity drift of the external environment, maintain the stability of the physical state of the humid laminar airflow above the water-based adhesive layer, and promote the bio-based polyester composite film to remain in a semi-swollen state in the corresponding control area and be transported to the downstream process.

[0038] Example 5: In industrial cluster deployment scenarios involving multiple pretreatment devices operating in parallel and requiring batch consistency, to eliminate uneven pulsating airflow intensity caused by differences in pipeline pressure drop between different processing units, the system implements pre-pressure compensation and benchmark calibration procedures; high-frequency dynamic pressure sensors are used to obtain the real-time dynamic pressure wave peak value at the nozzle of each processing unit. With dynamic pressure wave trough value The acquired pressure vector sequence is input into the deviation calculation module of the main control unit. The main control unit subtracts the real-time pressure value measured by each processing unit from the preset reference pressure value in the memory to obtain the pressure deviation. Based on the pressure deviation, the stepper motor speed of the corresponding branch air pressure reducing valve is adjusted until the peak value of the dynamic pressure wave of all processing units is reached. All are at 0.15 MPa and at the trough of dynamic pressure wave. All are at 0.05MPa; the system locks the motor control steps of each branch at this time as the equipment identity parameter and writes it into the global configuration database. In order to achieve consistency of processing effect among multiple devices, the main control unit performs dimensionality reduction calculation on multi-dimensional parameters through preset weight allocation logic. Specifically, the system sets the real-time dynamic pressure deviation ratio collected in real time as a mechanical contribution item with a weight coefficient of 0.6, and sets the approximation degree between the measured surface temperature and the glass transition temperature as a thermodynamic contribution item with a weight coefficient of 0.4. The normalized process gain operator generated by the weighted sum of the two is directly mapped to the adjustment amount of the mixing valve opening and pulse width modulation current. Specifically, the establishment of this mapping relationship is achieved through the following preset key The system's mapping table execution involves dividing the calculated normalized process gain operator into multiple preset numerical intervals, each corresponding to a specific combination of physical adjustment values. When the normalized process gain operator increases due to larger measured deviations, the main control unit linearly increases the opening pulse count of the mixing valve's electronically controlled stepper motor according to the current increment of the operator to improve the steam ratio. Simultaneously, it increases the pulse width modulation duty cycle of the heating component, thereby synchronously increasing the heating current to compensate for temperature drift. Conversely, when the process gain operator decreases, the main control unit proportionally decreases the opening step count of the mixing valve and reduces the duty cycle of the pulse width modulation current. Through this defined input-output mapping path, the abstract... The operator values ​​are directly converted into the underlying physical control output of the actuator; the mechanical contribution term is determined by subtracting 1 from the ratio of the real-time dynamic pressure wave peak value to the reference wave peak value and taking the absolute value, which is a dimensionless pure number. The thermodynamic contribution term is calculated by dividing the absolute difference between the measured surface temperature and the glass transition temperature of the substrate by the standard value of the glass transition temperature to achieve dimensionless processing, thus realizing the dimensional unification and unified mapping of the data structures of the mechanical and thermodynamic dimensions. In the relational mapping table, the normalized process gain operator generated by the final summation is limited to the dimensionless range of 0.00 to 1.00, and divided into four cascaded control intervals with a step size of 0.25. When the operator is in the first interval of 0.00 to 0.25, the system is considered to be in a steady state, and the mixing valve and heating component maintain their original parameters. When the operator increases to the second interval of 0.25 to 0.50, the mapping table outputs a determined physical adjustment amount, and the main control unit immediately sends 50 positive opening pulses to the electric stepper motor of the mixing valve, while simultaneously increasing the pulse width modulation duty cycle of the heating component by 5% to synergistically improve the performance of the local temperature and humidity field. When the operator continues to increase to the third interval of 0.50 to 0.75, the positive opening pulses increase to 100, and the duty cycle increase is increased to 10%, thus ensuring the accurate mapping of the abstract operator to the physical output of the underlying actuator through a clear discrete numerical range.

[0039] To address the uneven heat and mass transfer caused by localized orientation differences in the substrate during continuous stretching of bio-based polyester composite films, the main control unit acquires the film surface temperature distribution curve in the middle of the conveying path in real time; when a localized temperature deviation is detected... Greater than At this time, the system extracts correction coefficients by querying the preset thermal conductivity compensation model, adjusts the heating current density of the corresponding temperature zone of the heating roller to correct the local heat transfer intensity, and simultaneously fine-tunes the enthalpy value of the humid laminar airflow by adjusting the opening of the mixing valve. The preset thermal conductivity compensation model used here is manifested as a temperature-current matrix lookup table stored in the main control unit in actual operation. The control logic of this model is pre-calibrated based on the thermal conductivity and thickness thermal resistance of the substrate material. Its input is the local temperature deviation, and its output is the current density correction coefficient and the mixing valve adjustment amount. When the local temperature deviation is positive, it indicates that the area is overheated, and the model outputs a negative current correction coefficient, adjusting the current density proportionally. The conduction time of the solid-state relay in the independent temperature zone of the hot roller is reduced to decrease heat transfer power. When the local temperature deviation is negative and its absolute value increases, the model increases the output current correction coefficient to improve heating power. It also uses a lookup table to obtain the corresponding mixing valve opening and reduce the number of steps, thereby fine-tuning the spray enthalpy. Through this real-time correction of the closed-loop thermodynamic model, the influence of uneven lateral heat transfer on the consistency of the substrate's high-elasticity state is eliminated. The core values ​​of the temperature-current matrix lookup table are entirely based on the discrete step mapping relationship of column 1.0: when the real-time detected positive temperature deviation reaches 2.0℃ to 3.0℃, the current density correction coefficient output of the lookup table is -0.15. Based on this, the control unit proportionally reduces the pulse conduction time duty cycle of the solid-state relay from the original 50.0% to 35.0%, and simultaneously increases the opening step of the mixing valve stepper motor by 20 steps to increase the cold steam injection volume. When the positive temperature deviation further expands to 3.0℃ to 5.0℃, the output corresponding to the current density correction coefficient is adjusted to -0.30, the conduction time duty cycle is forcibly compressed to 20.0%, and the number of steps to increase the opening of the mixing valve is correspondingly increased to 40 steps. Conversely, when the local temperature deviation is negative, ranging from 2.0℃ to 3.0℃, the positive current density correction coefficient of the model output is determined to be +0.12, and the conduction time duty cycle is correspondingly increased. Up to 62.0%, and the number of steps to reduce the opening of the mixing valve is locked at 15. Through these deterministic discrete matrix numerical closed loops, accurate feedback of local temperature deviations to the control quantity at the execution end is achieved. The system utilizes the real-time coupling effect of pressure identity parameters and online temperature correction coefficients to offset the process drift caused by equipment aging or external air pressure fluctuations during production, maintaining the molecular gaps on the surface of the bio-based polyester substrate in a consistent interpenetrating state, and ensuring that the molecular chain segment embedding depth of the water-based adhesive layer is in the range of 0.5μm to 0.8μm. This achieves automatic alignment of pretreatment process parameters and stable output of interface physical locking structures on large-scale continuous production lines. In order to ensure that the accuracy is not lower than 0.A standardized, layered precision chemical exfoliation and total reflectance infrared spectroscopy quantitative determination procedure was established to achieve an objective, image-free quantitative identification of a 5μm micro-embedding depth. The procedure involved randomly cutting 100 square millimeter test samples from the treated composite film and placing them in a constant-temperature bath at 25℃. A specific organic solvent was used at a flow rate of 50 ml / min to perform controlled, cyclic surface etching and exfoliation on the coated surface at a gradient of 0.1 μm. After each layer of exfoliation, the test sample was automatically fed into a spectrometer. By measuring the absolute value change of absorbance of the characteristic ester group infrared absorption peaks, a discrete data chain corresponding to the absorbance change and the exfoliation depth was established. Since the characteristic absorption peaks of the water-based adhesive and the polyester substrate are independent, when… As the dissolution depth increased from 0.0 μm to 0.5 μm, the characteristic peak absorbance representing the adhesive component remained within a stable range of 0.85 to 0.90, without a sharp drop. Furthermore, the mass percentage of the adhesive component in the total extract remained consistently between 35% and 42% until the dissolution depth crossed the theoretical interlocking boundary of 0.5 μm to 0.8 μm, at which point the absorbance index completely decayed to below 0.05. Therefore, through the pure digital absorbance matrix and residual mass percentage curves of each exfoliation layer, and under the premise of completely eliminating subjective visual image evidence, conclusive discrete chemical and physical data confirmed that the vertical embedding depth of the molecular chain segments reached the required depth of 0.5 μm to 0.8 μm.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A pretreatment process for the production of 3D curved surface molding materials, characterized in that, Includes the following steps: Step 101: Convey a bio-based polyester composite film along a preset path. The bio-based polyester composite film includes a bio-based polyester substrate and an aqueous adhesive layer coated on the surface of the bio-based polyester substrate. Step 102: Establish an asymmetric temperature and humidity field. Use a heated roller to contact the adhesive-free surface of the bio-based polyester substrate to conduct heat and make the bio-based polyester substrate reach a high elastic state. Simultaneously spray a humid laminar flow airflow onto the surface of the water-based adhesive layer. The humid laminar flow airflow increases the partial pressure of water vapor in the environment above the water-based adhesive layer and maintains the water-based adhesive layer in a semi-swollen state. Step 103: Pulsed pneumatic compression. A pulsating airflow with a modulation frequency of 10Hz to 15Hz acts on the water-based adhesive layer in a semi-swollen state. The periodic normal compressive stress generated by the pulsating airflow is used to press the molecular chains of the water-based adhesive layer into the surface molecular gaps generated by the thermal expansion of the bio-based polyester substrate in a highly elastic state, forming a mechanically locked structure. In steps 102 and 103, the bio-based polyester composite film runs continuously. The asymmetric temperature and humidity field and the pulsating airflow work together to ensure that the bio-based polyester composite film reaches stress balance before molding and that the heterogeneous interface has physical anchoring activity.

2. The pretreatment process in the production of 3D curved surface molding materials according to claim 1, characterized in that, In step 102, the surface temperature of the heating roller is 75°C to 95°C, and the bonding and wrapping angle of the bio-based polyester substrate on the heating roller is 120° to 180°, so as to eliminate internal residual stress by relaxing the bio-based polyester substrate by heat.

3. The pretreatment process in the production of 3D curved surface molding materials according to claim 1, characterized in that, In step 102, the absolute humidity of the humid laminar flow is 18 g / kg to 25 g / kg, and the absolute value of the temperature difference between the humid laminar flow and the surface temperature of the heating roller is no greater than 5°C. By reducing the humidity gradient between the water-based adhesive layer and its surface environment, the diffusion of moisture in the water-based adhesive layer is suppressed.

4. The pretreatment process in the production of 3D curved surface molding materials according to claim 1, characterized in that, Step 103 specifically includes: using a rotary shut-off valve to periodically modulate the airflow output from the constant pressure gas source to generate a pulsating airflow with a dynamic pressure wave peak value of 0.15MPa and a dynamic pressure wave trough value of 0.05MPa, and using the momentum transfer of pressure fluctuations to drive the water-based adhesive layer to move into the bio-based polyester substrate.

5. The pretreatment process in the production of 3D curved surface molding materials according to claim 1, characterized in that, The thickness of the water-based adhesive layer is 5 μm to 15 μm, and after step 103, the physical anchoring depth of the mechanical locking structure on the surface of the bio-based polyester substrate is not less than 0.5 μm.

6. The pretreatment process in the production of 3D curved surface molding materials according to claim 1, characterized in that, The bio-based polyester substrate is polyethylene terephthalate-1,4-cyclohexanediol ester or polylactic acid. The bio-based polyester composite film has a heat residence time of 15s to 25s in an asymmetric temperature and humidity field.

7. The pretreatment process in the production of 3D curved surface molding materials according to claim 1, characterized in that, Step 103 is followed by step 104: online tension compensation feedback, which monitors the real-time tension value of the bio-based polyester composite film and adjusts the conveying rate in step 101 according to the deviation between the real-time tension value and the initial set value, so as to maintain the interface force balance before the mechanical locking structure is locked.

8. The pretreatment process in the production of 3D curved surface molding materials according to claim 1, characterized in that, In step 102, the spray direction of the humid laminar airflow is 30° to 45° with the running direction of the bio-based polyester composite film to form a micro-positive pressure coverage area on the surface of the water-based adhesive layer to prevent external air from penetrating.

9. The pretreatment process in the production of 3D curved surface molding materials according to claim 7, characterized in that, Step 104 is followed by: using cold air to cool the adhesive-free surface of the bio-based polyester composite film, reducing the temperature of the bio-based polyester substrate to below its glass transition temperature, and locking the molecular chains of the water-based adhesive layer embedded therein through the thermal shrinkage of the bio-based polyester substrate, thus completing the interface pretreatment.

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