A multi-layer biodegradable packaging material intelligent forming method based on data regulation

Abstract

The application discloses a kind of based on data regulation and control multilayer biodegradable packaging material intelligent forming method, it is related to industrial control technical field, the target mass flow and unit mass plasticization demand energy are determined according to the functional attribute, target thickness and thermal physical parameter of each material layer;The heat and mechanical energy of each independent extrusion unit are implemented synergic regulation and control, and plasticization setting power is obtained;Interface effective fusion energy density is determined by interface rheological matching to adjacent material layer melt;Under interface constraint, in-mold interlayer mass flow redistribution is completed, and in-mold compensation mass flow is obtained;Subsequently, segmented cooling is implemented, and the forming material is matched, layer structure state is distinguished and parameter layering is written back.This method can improve the thickness uniformity of each material layer, interface bonding stability and forming process control precision, reduce the risk of interlayer peeling, warping and material thermal degradation.

Description

Technical Field

[0001] This invention relates to the field of industrial control technology, specifically to a data-driven intelligent molding method for multi-layer biodegradable packaging materials. Background Technology

[0002] Multilayer biodegradable packaging materials typically consist of two or more materials selected from polylactic acid, polybutylene adipate / terephthalate, polybutylene succinate, polyhydroxyalkanoates, thermoplastic starch, polyvinyl alcohol, and bio-based fillers, forming protective, support, barrier, and heat-sealing layers, respectively. These materials are continuously formed through the coordinated operation of multiple extruders, melt metering pumps, manifold composite components, forming dies, cooling and shaping mechanisms, and traction mechanisms. Because the different material layers exhibit significant differences in melt temperature, apparent viscosity, thermal stability range, water sensitivity, crystallization rate, flow resistance, and cooling shrinkage, the molding quality of multilayer materials depends not only on the temperature or speed of a single extruder but also on the mass flow rate matching between extrusion units, the distribution of plasticizing energy, the temperature and viscosity matching of adjacent melts, the redistribution of flow within the die, the zoned cooling rates, and the continuous coordination of traction tension. Therefore, this type of molding process essentially utilizes process parameters such as temperature, pressure, torque, flow rate, layer thickness, tension, and interface state to automatically adjust the heater, drive motor, melt metering pump, flow channel regulator, cooling actuator, and traction mechanism to maintain the stable operation of the multivariable industrial molding process.

[0003] Existing multilayer packaging material molding equipment typically employs fixed temperature zones, fixed screw speeds, and fixed traction ratios, similar to those used for petroleum-based polymers, or only adjusts die lip clearance and total extrusion volume based on total thickness measurements. This control method treats each material layer as a relatively independent feedstock, failing to determine the actual required mass flow rate and plasticizing energy per unit mass for each layer based on target layer thickness, material density, melt enthalpy, initial moisture content, and rheological properties. It also fails to uniformly convert heating input and screw mechanical shear input into a comparable effective plasticizing load. When the raw material batch, moisture content, or viscosity of biodegradable materials changes, fixed control parameters are difficult to adapt in a timely manner, easily leading to insufficient plasticization and melt pressure fluctuations in some material layers, while other material layers undergo molecular chain degradation due to excessive heating or shearing, resulting in decreased melt strength, increased surface crystal points, and unstable mechanical properties of the finished product.

[0004] Furthermore, existing technologies for adjusting multilayer structures typically focus on the final total thickness or appearance, lacking correlation control over the interface state of adjacent material layers and the actual thickness of each layer. Different biodegradable melts may exhibit significant temperature, viscosity, and flow rate differences during confluence and compounding. Simply increasing the flow rate of a single layer to correct the layer thickness can easily lead to interface fluctuations, thin barrier layer shifts, material crosstalk, or localized delamination. Conversely, simply increasing the die temperature to improve interlayer bonding may cause degradation of heat-sensitive materials. Simultaneously, the cooling process after die exit typically employs a uniform roller temperature or fixed air cooling intensity, failing to differentiate between interface locking, layer stabilization, and residual stress release stages based on the mass flow rate, crystallization characteristics, and interface fusion state of each layer. This results in asynchronous shrinkage of different material layers, causing interlayer delamination, edge curling, longitudinal thinning, and surface ripples. Even if the final inspection results can identify unqualified product thickness, it is difficult to accurately determine whether the defect originates from plasticizing energy, interface matching, in-mold flow rate, cooling shrinkage, or traction extension. This leads to repeated adjustments by multiple actuators simultaneously, easily resulting in control oscillations and interference between process parameters. Therefore, there is an urgent need for an intelligent molding method for multi-layer biodegradable packaging materials that embodies the characteristics of industrial automatic control, which integrates layer molding requirements, plasticizing load, interface fusion state, in-mold flow distribution, segmented cooling, and traction feedback into a unified closed-loop control process with sequential relationships. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a data-controlled intelligent molding method for multilayer biodegradable packaging materials, thereby solving the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a data-controlled intelligent molding method for multilayer biodegradable packaging materials, comprising the following steps: S1. Based on the functional properties, target thickness and thermal properties of each material layer in the multi-layer biodegradable packaging material, establish the molding requirement mapping for each material layer and determine the target mass flow rate and unit mass plasticizing energy requirement for each material layer. S2. Based on the target mass flow rate and unit mass plasticizing energy required for each material layer determined in step S1, thermal and mechanical energy are coordinated and controlled for the independent extrusion unit corresponding to each material layer to obtain the plasticizing set power for each material layer. S3. Based on the plasticizing setting power of each material layer obtained in step S2, perform interfacial rheological matching on the melt of adjacent material layers entering the confluence composite zone to obtain the effective fusion energy density of the interface between each adjacent material layer. S4. Based on the effective fusion energy density of the interface between each adjacent material layer obtained in step S3, the interlayer mass flow rate of each material layer melt entering the forming die head is redistributed under interface constraints to obtain the in-die compensated mass flow rate of each material layer. S5. Based on the in-mold compensated mass flow rate of each material layer obtained in step S4 and the effective fusion energy density of the interface obtained in step S3, the multi-layer melt leaving the forming die head is subjected to segmented cooling and shaping to form a cooling and shaping parameter set. S6. Based on the cooling and shaping parameter group formed in step S5 and the in-mold compensation mass flow rate of each material layer obtained in step S4, the multi-layer biodegradable packaging material that has completed cooling and shaping is subjected to traction matching, layer structure state discrimination and layered writing of molding parameters to complete intelligent molding closed-loop control.

[0007] To further optimize this technical solution, step S1 further includes: Based on the wear-resistant protection, mechanical support, gas barrier, water vapor barrier and heat-sealing contact functions of each material layer in the multi-layer biodegradable packaging material, the multi-layer biodegradable packaging material is divided into layers to obtain the layer sequence, target thickness, material composition and thickness ratio of each material layer. Determine the target mass flow rate and energy requirement per unit mass for plasticizing each material layer; By correlating the layer sequence, target mass flow rate, and unit mass plasticizing energy requirement of each material layer, a layered molding demand mapping is formed for plasticizing control of each independent extrusion unit.

[0008] Further optimization of this technical solution includes determining the target mass flow rate and unit mass plasticizing energy requirement for each material layer, including: The target mass flow rate of each material layer is determined based on the target thickness, equivalent density of the material, effective forming width of the multilayer biodegradable packaging material, and baseline velocity. Based on the average specific heat capacity, target plasticizing temperature, initial feed temperature, crystalline phase mass ratio, enthalpy of melt, feed water content, and initial apparent viscosity of each material layer, determine the unit mass plasticizing energy requirement for each material layer.

[0009] To further optimize this technical solution, step S2 further includes: The actual mass flow rate, heating power, screw torque and screw angular velocity of each independent extrusion unit in the current control cycle are obtained. Based on the effective heat transfer efficiency from the heater to the material melt and the effective efficiency of the conversion of screw mechanical work to melt shear heat, the actual input energy per unit mass of each material layer in the current control cycle is determined. The actual input energy per unit mass is compared with the plasticizing energy required per unit mass of the corresponding material layer to obtain the plasticizing energy deviation of each material layer. Based on the plasticizing energy deviation, the target mass flow rate of the corresponding material layer, and the preset plasticizing energy deviation correction coefficient, the plasticizing setting power of each independent extrusion unit in the next control cycle is determined.

[0010] To further optimize this technical solution, the plasticizing setting power is allocated as a proportion of barrel heating power and screw mechanical power based on the shear sensitivity and thermal stability temperature range of each material layer. Under the constraints of the upper limit of material thermal decomposition temperature, the upper limit of screw torque, the upper limit of barrel pressure, and the minimum stable mass flow rate, plasticizing control is performed on each independent extrusion unit.

[0011] To further optimize this technical solution, step S3 further includes: Obtain the actual temperature, apparent viscosity, average interfacial velocity, effective contact length, effective contact area, and effective contact time when the melt from adjacent material layers enters the confluence and composite zone; The effective fusion energy density of the interface between adjacent material layers is determined based on the plasticizing setting power, effective contact time, effective contact area, interfacial energy conversion ratio, viscosity difference and temperature difference between the melts of adjacent material layers.

[0012] To further optimize this technical solution, the effective fusion energy density at the interface is compared with the lowest and highest safe fusion energy densities of the corresponding adjacent material combinations: When the effective fusion energy density of the interface is lower than the minimum interface fusion energy density, the effective fusion energy density of the interface is increased by successively reducing the velocity difference between adjacent material layer melts, implementing local reheating for material layer melts with higher viscosity or lower temperature, and extending the effective contact time in the confluence composite zone. When the effective fusion energy density of the interface is higher than the maximum safe interface fusion energy density, excessive interdiffusion between adjacent material layers is limited by shortening the effective contact time or reducing the local heating power.

[0013] To further optimize this technical solution, in step S4, after determining the in-mold compensation mass flow rate of each material layer, a total constraint is applied to the in-mold compensation mass flow rate of all material layers so that the sum of the in-mold compensation mass flow rate of each material layer is consistent with the current total extrusion mass flow rate. The in-mold compensation mass flow rate after the total constraint is converted into the rotation speed of the corresponding melt metering pump, the opening degree of the branch flow channel regulator, and the position of the variable throttling device.

[0014] To further optimize this technical solution, step S5 further includes: Along the conveying direction of the multi-layer melt from the forming die head to the traction unit, an interface locking zone, a layer stabilization zone, and a stress release zone are set sequentially. Based on the in-mold compensated mass flow rate of each material layer, the effective fusion energy density of the interface between adjacent material layers, the thermal stability temperature range of the material, and the flow state of the material near the interface, the upper and lower surface temperatures, heat transfer intensity, and interface locking time of the interface locking zone are determined to keep the interface between adjacent material layers continuously bonded and to limit further cross-contamination between material layers. Based on the in-mold compensation mass flow rate, target thickness, thermal diffusion characteristics and crystallization characteristics of each material layer, the cooling roller temperature, roller surface contact time, cooling airflow intensity and transverse zone heat transfer intensity in the stable zone of the layer are determined so that each material layer gradually reaches a stable state that can withstand traction load. Based on the temperature difference between the upper and lower surfaces of the multi-layer biodegradable packaging material, the shrinkage difference of each material layer, and the residual stress state, the relaxation temperature, passage time, and tension limit value of the stress release zone are determined so that each material layer can relax its molecular chains without restoring macroscopic flow. The control parameters of the interface locking zone, the layer stabilization zone, and the stress release zone are combined to form a cooling and shaping parameter set that matches the current material layer structure and the in-mold compensation mass flow rate.

[0015] To further optimize this technical solution, in step S6, the plasticizing power, interface contact conditions, in-mold compensation mass flow rate, cooling and shaping parameter group, and traction speed are written back layer by layer according to the priority order of first correcting the thermal stability state and interface continuity state of the material, then correcting the thickness state of each material layer, and finally correcting the surface flatness and edge curling state. This process continues until the thickness of each material layer, interface continuity, surface flatness, and traction tension are within the corresponding allowable range for multiple consecutive control cycles. The current molding parameters are then determined as the stable molding parameters for the current material batch.

[0016] In a second aspect, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, they implement the steps of a data-controlled intelligent molding method for multilayer biodegradable packaging materials as described in the first aspect of the present invention.

[0017] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, the steps of a data-controlled intelligent molding method for multilayer biodegradable packaging materials as described in the first aspect of the present invention are implemented.

[0018] Compared with existing technologies, this invention provides a data-controlled intelligent molding method for multilayer biodegradable packaging materials, which has the following beneficial effects: This data-driven intelligent molding method for multi-layer biodegradable packaging materials determines the target mass flow rate and energy requirement per unit mass for plasticization based on the target thickness, thermal properties, and rheological characteristics of each biodegradable material layer. It then sequentially controls the thermal and mechanical energy inputs of each independent extrusion unit, the effective fusion state of the interface between adjacent melts, the interlayer mass flow rate within the molding die, the zoned cooling process after the die exit, and the traction state after shaping. This allows the output parameters of the previous control stage to serve as constraints for the next. Simultaneously, correction commands are written back to the corresponding molding stage based on the final layer thickness, interface continuity, and residual stress state. This avoids parameter coupling and control oscillations caused by indiscriminate adjustment based solely on the total thickness, improves the uniformity of layer thickness, interlayer bonding stability, and barrier layer continuity, and reduces the risk of degradation, warping, and peeling of biodegradable materials due to overheating, overshearing, or mismatched cooling shrinkage. This achieves automated, continuous, and stable control of the multi-layer biodegradable packaging material molding process. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the process for a data-controlled intelligent molding method for multi-layer biodegradable packaging materials proposed in this invention. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0024] Example 1: Reference Figure 1This is the first embodiment of the present invention, which provides a data-controlled intelligent molding method for multilayer biodegradable packaging materials, comprising the following steps: S1. Based on the functional attributes, target thickness, and thermal properties of each material layer in the multi-layer biodegradable packaging material, establish a molding requirement mapping for each material layer and determine the target mass flow rate and unit mass plasticizing energy requirement for each material layer.

[0025] S1.1. Based on the wear-resistant protection, mechanical support, gas barrier, water vapor barrier and heat-sealing contact functions undertaken by each material layer in the multi-layer biodegradable packaging material, the multi-layer biodegradable packaging material is divided into layers to obtain the layer sequence, target thickness, material composition and thickness ratio of each material layer.

[0026] S1.2. Determine the target mass flow rate of each material layer based on the target thickness, equivalent density of the material, effective forming width of the multilayer biodegradable packaging material, and baseline velocity.

[0027] S1.3. Based on the average specific heat capacity, target plasticizing temperature, initial feed temperature, crystalline phase mass ratio, melting enthalpy, feed water content and initial apparent viscosity of each material layer, determine the unit mass plasticizing energy requirement of each material layer.

[0028] S1.4 Correlate the layer sequence, target mass flow rate, and unit mass plasticizing energy requirement of each material layer to form a layered molding demand mapping for plasticizing control of each independent extrusion unit.

[0029] During implementation, the structure to be formed is first divided into at least three layers according to the functional division of the multi-layer biodegradable packaging material in actual use: an outer wear-resistant protective layer, a middle mechanical support layer, a barrier functional layer, and an inner heat-sealing contact layer. The specific number of layers is denoted as n, and the layer number as i, where i is a positive integer from 1 to n. Different layers can be formed using biodegradable compositions of polylactic acid, polybutylene adipate / terephthalate, polybutylene succinate, polyhydroxyalkanoates, thermoplastic starch, polyvinyl alcohol, nanocellulose, and bio-based modified fillers. The target thickness, material density, melting temperature, initial moisture content, melting enthalpy, and reference viscosity of each layer are converted into molding requirements parameters that can be directly used by subsequent equipment. For the i-th layer, the target mass flow rate is determined based on the total thickness of the packaging material, the corresponding layer thickness ratio, the forming width, and the preset linear velocity. The conversion relationship is as follows:

[0030] in, Let be the target mass flow rate of the i-th layer, in kilograms per second; The equivalent density of the i-th layer material at the molding temperature is expressed in kilograms per cubic meter. The effective forming width of multi-layer sheets or films, in meters; The target thickness of the i-th layer is expressed in meters. The baseline speed set for the current production batch, in meters per second.

[0031] The target thickness is obtained by multiplying the total thickness of the packaging material by the thickness ratio of each layer, with the sum of the thickness ratios of each layer being 1. The equivalent density is determined by combining the density test results of the material supply batch with the volume expansion correction coefficient in the molten state. The effective forming width is obtained by subtracting the width of the side trimmings from the effective flow channel width of the die head. The baseline linear velocity is set according to the packaging specifications, subsequent traction capacity, and unit time production capacity requirements, and is generally controlled within the range of 0.02 to 1.50 meters per second. This conversion relationship ensures that the extrusion feed amount of each layer is no longer determined solely by the screw speed based on experience, but rather forms a definite physical mapping with the final layer thickness and linear velocity.

[0032] After obtaining the target mass flow rate, and further considering the significant differences in heat capacity, enthalpy of melt, water sensitivity, and melt viscosity among different biodegradable materials, a unit mass plasticization energy demand model for the i-th layer is established:

[0033] in, Let be the energy required for plasticizing a unit mass of the i-th layer material, expressed in joules per kilogram. is the average specific heat capacity of the i-th layer material, in joules per kilogram Kelvin; is the target plasticizing temperature of the i-th layer material, in Kelvin; The initial temperature of the i-th layer of material before it enters the extrusion unit is expressed in Kelvin. The mass ratio of the crystalline phase that needs to undergo a melt transformation is a dimensionless parameter between 0 and 1. Let be the enthalpy of fusion of the i-th layer material, in joules per kilogram; Let be the water content of the i-th layer material before it enters the extrusion unit, and be a dimensionless parameter. The correction factor for additional plasticization and moisture removal energy caused by water content, in joules per kilogram; Let be the initial apparent viscosity of the i-th layer material at the reference shear rate, in Pascals per second; To ensure a uniform reference viscosity, the unit is also Pascal-second; therefore, the ratio between the two and their natural logarithm are both dimensionless quantities. This is the plasticizing energy correction factor corresponding to the viscosity difference, expressed in joules per kilogram.

[0034] The specific heat capacity and enthalpy of fusion are obtained by differential scanning calorimetry. The target plasticizing temperature is determined by the melting peak temperature, stable flow temperature, and thermal decomposition initiation temperature, preferably 5–30 Kelvin higher than the continuous flow temperature of the material and 20–60 Kelvin lower than the thermal decomposition initiation temperature. The initial temperature is obtained by the temperature detection unit at the bottom of the hopper. The water content is obtained by the online near-infrared moisture detection unit or by weight loss method before entering the hopper. The initial apparent viscosity is obtained by batch sampling rheological curves or by the bypass micro rheological detection unit installed at the feeding end, and its reference shear rate remains consistent across layers. The water content correction factor and viscosity correction factor are determined by the unit output energy consumption test during the equipment commissioning phase.

[0035] In actual use, the controller calculates separately for each layer. and This generates a layered molding demand map that includes layer number, target mass flow rate, and unit mass plasticizing energy requirement. This map is used only to specify the feed load and plasticizing energy required for the next step in each extrusion unit.

[0036] S2. Based on the target mass flow rate and unit mass plasticizing energy requirement of each material layer determined in step S1, thermal and mechanical energy are coordinated and controlled for the independent extrusion unit corresponding to each material layer to obtain the plasticizing set power of each material layer.

[0037] S2.1 Obtain the actual mass flow rate, heating power, screw torque and screw angular velocity of each independent extrusion unit in the current control cycle, and determine the actual input energy per unit mass of each material layer in the current control cycle based on the effective heat transfer efficiency from the heater to the material melt and the effective efficiency of the screw mechanical work to the melt shear heat conversion.

[0038] S2.2. Compare the actual input energy per unit mass with the plasticizing energy required per unit mass of the corresponding material layer to obtain the plasticizing energy deviation of each material layer.

[0039] S2.3. Based on the plasticizing energy deviation, the target mass flow rate of the corresponding material layer, and the preset plasticizing energy deviation correction coefficient, determine the plasticizing setting power of each independent extrusion unit in the next control cycle. S2.4. Based on the shear sensitivity and thermal stability temperature range of each material layer, the plasticizing setting power is allocated to the barrel heating power share and the screw mechanical power share. Under the constraints of the upper limit of material thermal decomposition temperature, the upper limit of screw torque, the upper limit of barrel pressure, and the minimum stable mass flow rate, the plasticizing control of each independent extrusion unit is performed.

[0040] During implementation, due to the varying sensitivities of materials such as polylactic acid, polybutylene succinate, thermoplastic starch, and polyvinyl alcohol to temperature, shear, and residence time, controlling the process solely with the same barrel temperature or a fixed screw speed can easily lead to insufficient plasticization of some materials while thermal degradation occurs in others. Therefore, this step does not directly use the target plasticizing temperature as the sole control variable. Instead, it converts the effective thermal power input from the heater and the effective mechanical power generated by the screw rotation into a unified effective input energy per unit mass. Based on the deviation between this energy and the unit mass plasticizing energy requirement output by S1, the plasticizing setting power for the next control cycle is calculated. The plasticizing setting power of the i-th extrusion unit in the (k+1)-th control cycle is determined according to the following formula:

[0041] in, Set the plasticizing power for the i-th extrusion unit in the (k+1)-th control cycle, in watts; is the correction coefficient for the plasticizing energy deviation of the i-th layer, and is a dimensionless parameter between 0 and 1; is the effective heat transfer efficiency between the heater and the molten material, which is a dimensionless parameter; The total electric heating power of each heating zone of the i-th extrusion unit during the k-th control cycle is expressed in watts. is the effective efficiency of converting the mechanical work of the screw into the shear heat of the melt, and is a dimensionless parameter; The screw shaft torque of the i-th extrusion unit during the k-th control cycle is expressed in Newton-meters. The corresponding screw angular velocity is expressed in radians per second. This represents the actual mass flow rate of the i-th layer material during the k-th control cycle, expressed in kilograms per second.

[0042] The actual mass flow rate is determined by combining the weight loss per unit time of the loss-in-weight feeder with the calibration results of the melt pump outlet flow rate; the heating power is calculated from the voltage, current, and duty cycle of each barrel heating zone; the screw torque is obtained from the drive motor torque feedback value after efficiency correction by the reduction mechanism; the screw angular velocity is converted from the speed output by the encoder; the heat transfer efficiency and mechanical work conversion efficiency are determined during the calibration process of equipment no-load loss, stable extrusion energy consumption, and melt temperature rise. The heat transfer efficiency is generally taken as 0.45 to 0.90, and the mechanical work conversion efficiency is generally taken as 0.35 to 0.85; the plasticizing energy deviation correction coefficient is set according to the thermal sensitivity of the material. For materials with a narrow thermal stability window, it is taken as 0.10 to 0.35, and for materials with a wide thermal stability window, it is taken as 0.35 to 0.70. For the same batch of materials, the correction coefficient can also be slightly updated based on the melt pressure fluctuation and torque fluctuation within three consecutive control cycles, but the updated value is always limited to the preset range to avoid sudden changes in control power.

[0043] The controller calculates The set power is then allocated to a barrel heating power share and a screw mechanical power share. For layers with a high proportion of thermoplastic starch or polyvinyl alcohol and strong shear sensitivity, the barrel heating power share is prioritized to be increased while limiting the screw angular velocity increase. For layers with a high proportion of polylactic acid or polybutylene succinate and requiring sufficient shear dispersion, the mechanical power share can be appropriately increased within the safe temperature range. During the power allocation process, upper limits for material thermal decomposition temperature, drive motor torque, barrel pressure, and minimum stable mass flow rate are simultaneously set. When the calculated plasticizing set power exceeds the allowable range of the equipment or material, it is truncated at the boundary, and overload is eliminated primarily by reducing the instantaneous feed rate corresponding to the target linear velocity of that layer, rather than continuously increasing the temperature. After each control cycle, the actual heating power, screw torque, angular velocity, and mass flow rate are re-substituted into the model to generate the set value for the next cycle, so that the effective unit mass input energy of each extrusion unit gradually approaches the unit mass plasticizing energy demand determined by S1.

[0044] S3. Based on the plasticizing setting power of each material layer obtained in step S2, perform interfacial rheological matching on the melt of adjacent material layers entering the confluence composite zone to obtain the effective fusion energy density of the interface between each adjacent material layer.

[0045] S3.1 Obtain the actual temperature, apparent viscosity, average interfacial velocity, effective contact length, effective contact area, and effective contact time of the melt from adjacent material layers when it enters the confluence and recombination zone.

[0046] S3.2. Determine the effective fusion energy density of the interface between each adjacent material layer based on the plasticizing setting power, effective contact time, effective contact area, interfacial energy conversion ratio, viscosity difference and temperature difference between the melts of adjacent material layers.

[0047] S3.3. The effective fusion energy density of the interface is compared with the lowest interface fusion energy density and the highest safe interface fusion energy density of the corresponding adjacent material combination.

[0048] S3.4 When the effective fusion energy density of the interface is lower than the minimum interface fusion energy density, the effective fusion energy density of the interface is increased by successively reducing the velocity difference between adjacent material layer melts, implementing local heat replenishment for material layer melts with higher viscosity or lower temperature, and extending the effective contact time in the confluence and composite zone; when the effective fusion energy density of the interface is higher than the maximum safe interface fusion energy density, the excessive interdiffusion between adjacent material layers is limited by shortening the effective contact time or reducing the local heat replenishment power.

[0049] During implementation, an effective fusion energy density model of the interface between adjacent biodegradable melts is constructed, and the contact temperature, contact time, and velocity difference in the confluence composite zone are adjusted accordingly. After S2, each layer of material has formed a continuous melt that meets its own plasticization requirements. However, even if different layers of melt reach a flowable state, it does not mean that they can directly form a stable interface. For example, the polylactic acid layer and the thermoplastic starch layer may have large viscosity differences, non-overlapping temperature windows, and low interfacial diffusion rates; the polyvinyl alcohol barrier layer and the polybutylene succinate support layer may also have local interfacial voids due to polarity differences and moisture migration. Therefore, in this step, after each layer of melt enters the multi-layer confluence composite block and before entering the final forming die, an effective fusion energy density model is established for any adjacent i-th layer and i+1-th layer to comprehensively characterize the effective energy of the two layers of melt in the limited contact area that can be used for interfacial wetting, molecular chain interdiffusion, and interfacial defect compression. The effective fusion energy density of the interface between adjacent layers is calculated according to the following formula:

[0050] in, is the effective fusion energy density of the interface between the i-th layer and the (i+1)-th layer, in joules per square meter; The effective proportion of the energy input to the two-layer melt that can be converted into interfacial wetting and molecular chain interdiffusion is a dimensionless parameter between 0 and 1. The effective time, in seconds, is the time during which two adjacent melt layers remain in direct contact within the confluence and recombination zone. The effective contact area between the two layers of melt during this control cycle, in square meters; and These are the apparent viscosities of the two melt layers when they enter the confluence and recombination zone, both in Pascals per second. and These are the actual temperatures of the two melt layers at the interface inlet, in Kelvin. The interface reference temperature is set uniformly, and the unit is Kelvin; This is the viscosity mismatch penalty coefficient. is the temperature mismatch penalty coefficient, and both are dimensionless parameters.

[0051] The effective contact time is determined based on the ratio of the effective contact length of the confluence zone to the average flow velocity at the interface of the two melt layers; the effective contact area is determined based on the width, contact length, and actual filling coefficient of the confluence zone; the apparent viscosity of the melt is obtained by conversion from the inlet pressure difference of the confluence zone, known channel dimensions, and local flow rate, or periodically calibrated using a bypass slit rheological detection unit; the interface inlet temperature is obtained by temperature detection elements embedded in the walls of adjacent channels of the confluence block, and corrected based on the temperature hysteresis coefficient between the detection element and the melt center; the effective ratio... Calibration is performed through peel strength tests of adjacent material combinations; viscosity mismatch penalty coefficients and temperature mismatch penalty coefficients are obtained by fitting interfacial peel tests with varying viscosity ratios and temperature differences between the two layers, typically set within the ranges of 0.1–1.5 and 0.2–2.0, respectively. For material combinations incorporating bio-based compatibilizers or reactive chain extenders, It can be appropriately increased, but its specific value should still be based on the interface calibration results of the same batch of materials.

[0052] In actual control, the controller calculates the values ​​of each adjacent interface separately. The calculated results are compared with the pre-calibrated minimum and maximum safe interface fusion energy densities. When the calculated result is lower than the minimum interface fusion energy density, it indicates that although the adjacent layers have completed independent plasticization, they are still insufficient to form a stable interface under the current viscosity difference, temperature difference, and contact time conditions. In this case, the velocity difference between the two layers entering the confluence and composite zone is reduced first to make the flow direction of the two layers tend to be consistent. Subsequently, without exceeding the upper limit of the thermal stability of the two materials, local heating is applied to the side with lower temperature or higher viscosity. If the temperature and velocity are close to the allowable boundary, the effective contact time is extended by adjusting the position of the variable contact section in the confluence and composite zone. Conversely, when the effective interface fusion energy density is higher than the maximum safe value, it indicates that there may be excessive heating, excessive residence time, or low molecular migration risk in the interface region. In this case, the effective contact section is shortened or the local heating power is reduced to prevent thermal degradation of the barrier layer, excessive softening of the support layer, or significant material cross-linking at the interface.

[0053] The adjustment goal of this step is to make the adjacent interfaces... All flow rates fall within the allowable range for the corresponding material combinations, while maintaining unconstrained changes in the independent mass flow rates of each layer. The adjusted effective interfacial fusion energy density... As input for the next step, it is used to constrain the flow redistribution and layer thickness balance of the multi-layer melt after entering the forming die, so as to avoid destroying the already formed interface stability state in order to correct the thickness.

[0054] S4. Based on the effective fusion energy density of the interface between each adjacent material layer obtained in step S3, the interlayer mass flow rate of each material layer melt entering the forming die head is redistributed under interface constraints to obtain the in-die compensated mass flow rate of each material layer.

[0055] S4.1 For a material layer located in the middle of a multilayer structure, the smaller value of the effective fusion energy density of the interfaces on both sides of the material layer is determined as the interface constraint value of the material layer; for a material layer located on the outside of the multilayer structure, the effective fusion energy density of the interface of the only adjacent interface of the material layer is determined as the interface constraint value of the material layer.

[0056] S4.2 Detect the thickness of each material layer melt before the die head exit, and correct the detected layer thickness according to the die expansion ratio of the corresponding material to obtain the predicted exit thickness of each material layer.

[0057] S4.3. Determine the in-mold compensation mass flow rate of each material layer based on the target mass flow rate, target thickness, predicted exit thickness, interface constraint value, target interface fusion energy density, thickness deviation correction coefficient, and interface constraint correction coefficient.

[0058] S4.4. The total amount of in-mold compensated mass flow rate of all material layers is constrained so that the sum of the in-mold compensated mass flow rate of each material layer is consistent with the current total extrusion mass flow rate. The in-mold compensated mass flow rate after total amount constraint is converted into the corresponding melt metering pump speed, branch flow channel adjustment component opening degree and variable throttling component position.

[0059] During implementation, after interface matching in S3, adjacent melts form a continuous contact interface within the confluence and composite zone. However, after each layer of melt enters the coat hanger die, distributor die, or multi-manifold die, it is still affected by the difference in flow channel length, die cavity pressure gradient, melt elastic recovery, and inconsistent local resistance of the die lip, causing the actual layer thickness to deviate from the target thickness determined in S1. In particular, the target thickness of the barrier layer is usually significantly smaller than that of the support layer and heat-sealing layer. If the flow rate of the barrier layer is directly increased based solely on the outlet thickness deviation, local material insertion, interface fluctuations, or interlayer instability may occur when the effective fusion energy density at the interface between the barrier layer and adjacent layers is low. Therefore, this step uses the effective fusion energy density at the interface obtained in S3 as the limiting basis for adjusting the in-die flow rate, ensuring that the layer thickness compensation action simultaneously meets the thickness requirements and the interface bearing capacity. For the i-th layer, the effective fusion energy density of its interface with the adjacent layer is first converted into the interface constraint value of the i-th layer. When the i-th layer is located in the middle of the multilayer structure, the smaller value between the effective fusion energy densities of its two adjacent interfaces is taken as the interface constraint value of the i-th layer. When the i-th layer is the outermost layer, the effective fusion energy density of its only adjacent interface is directly used as the interface constraint value. This avoids masking the risk of local interface instability by using an average value when one side of the interface is fully fused while the other side is still in a weak state.

[0060] The intramold compensated mass flow rate of the i-th layer is determined by the following formula:

[0061] in, The in-mold compensation mass flow rate of the i-th layer of melt when it enters the main distribution channel of the forming die head, in kilograms per second; is the thickness deviation correction coefficient for the i-th layer, and is a dimensionless parameter; The predicted exit thickness of the i-th layer of melt under the current in-mold flow state is expressed in meters. Let be the correction coefficient for the interface constraint of the i-th layer, and be a dimensionless parameter; This represents the interface constraint value corresponding to the i-th layer, expressed in joules per square meter, and its value is directly derived from the output of S3. ; The target interface fusion energy density is the amount of joules per square meter required for the i-th layer to allow for conventional flow compensation.

[0062] The predicted exit thickness is not directly based on the final cooled sheet thickness, but rather determined by near-field layer thickness detection results and die expansion correction results located near the die exit. For transparent or semi-transparent multilayer materials, confocal optical detection units can be used to identify the refractive index boundaries of each layer; for materials containing bamboo powder, starch, or mineral fillers with low transparency, terahertz time-domain detection or multi-frequency ultrasonic detection can be used to identify the interlayer interfaces. The detected pre-exit layer thickness is corrected by combining it with the die expansion ratio of the corresponding material to form... The thickness deviation correction coefficient is obtained by changing the melt pump speed and measuring the outlet layer thickness response, and is preferably set to 0.10–0.65; for thinner barrier layers that are sensitive to interlayer coating, the value is preferably 0.10–0.30, and for thicker support layers, the value is preferably 0.30–0.65. The target interface fusion energy density is obtained by reverse calibration of the effective interface fusion energy density corresponding to the peel strength of adjacent layers reaching the design lower limit; the interface constraint correction coefficient is determined according to the interface weakness, and is preferably set to 0.05–0.50.

[0063] The meaning of setting interface constraint terms in the formula is: when Below When the interface constraint difference is negative, the negative sign in the formula transforms this term into positive compensation. However, the controller does not directly and significantly increase the flow rate of a single layer. Instead, it prioritizes allocating the new flow rate to stable channels near the center of the interface and simultaneously limits the instantaneous velocity difference between this layer and adjacent layers to enhance interlayer continuity by increasing the degree of interface compression. Significantly higher When the interface has a high fusion bearing capacity, the interface pressing compensation can be appropriately reduced, allowing thickness correction to rely more on local die lip clearance adjustment, thus avoiding unnecessary increases in single-layer flow rate. For cases with insufficient layer thickness and low interface fusion energy density, the controller limits the flow rate increment within a single cycle to no more than 2% to 8% of the target mass flow rate of that layer; for cases with insufficient layer thickness but sufficient interface fusion energy density, the allowable single-cycle increment can be increased to 5% to 15%.

[0064] Controller calculates all Subsequently, a total constraint is applied to the compensated mass flow rate of each layer to ensure that the sum of the compensated mass flow rates of each layer is consistent with the current total extrusion mass flow rate. When the sum of the calculated results of each layer is higher than the total extrusion mass flow rate, the compensation amount of the layer with higher interface constraint value and larger thickness safety margin is compressed first; when the sum of the calculated results of each layer is lower than the total extrusion mass flow rate, the remaining flow rate is allocated first to the layer that provides mechanical support and has a stable interface fusion state, rather than concentrating the excess flow rate into the thin barrier layer. Finally, the in-die compensated mass flow rate of each layer is converted into the corresponding melt metering pump speed, variable throttle block position, and branch flow channel adjustment opening, so that the multi-layer melt maintains continuous spreading in the die width direction. This step outputs the in-die compensated mass flow rate of each layer. This serves as the direct basis for determining the cooling load and interlayer curing sequence in S5.

[0065] S5. Based on the in-mold compensation mass flow rate of each material layer obtained in step S4 and the effective fusion energy density of the interface obtained in step S3, the multi-layer melt leaving the forming die head is subjected to segmented cooling and shaping to form a cooling and shaping parameter set.

[0066] S5.1 Along the conveying direction of the multi-layer melt from the forming die head to the traction unit, the interface locking zone, the layer stabilization zone, and the stress release zone are set in sequence.

[0067] S5.2. Based on the in-mold compensation mass flow rate of each material layer, the effective fusion energy density of the interface between adjacent material layers, the thermal stability temperature range of the material, and the flow state of the material near the interface, determine the upper and lower surface temperatures, heat transfer intensity, and interface locking time of the interface locking zone, so that the interface between adjacent material layers remains continuously bonded and further cross-contamination between material layers is restricted.

[0068] S5.3. Based on the in-mold compensation mass flow rate, target thickness, thermal diffusion characteristics and crystallization characteristics of each material layer, determine the cooling roller temperature, roller surface contact time, cooling airflow intensity and transverse zone heat transfer intensity in the stable zone of the layer, so that each material layer gradually reaches a stable state that can withstand traction load.

[0069] S5.4. Based on the temperature difference between the upper and lower surfaces of the multi-layer biodegradable packaging material, the shrinkage difference of each material layer, and the residual stress state, determine the relaxation temperature, passage time, and tension limit value of the stress release zone, so that each material layer can relax its molecular chains without restoring macroscopic flow.

[0070] S5.5 Combine the control parameters of the interface locking zone, the control parameters of the layer stabilization zone, and the control parameters of the stress release zone to form a cooling and shaping parameter set that matches the current material layer structure and the in-mold compensation mass flow rate.

[0071] During implementation, after the in-mold flow redistribution in S4, the multilayer melt has essentially formed the target layer thickness relationship when it leaves the die head. However, the thermal diffusion rate, glass transition temperature, crystallization rate, and shrinkage ratio of each layer are not the same. If a single-temperature cooling roller or a fixed air cooling intensity is used for rapid cooling, the outer material may have already solidified, while the middle barrier layer remains in a high-flow state, causing the barrier layer to migrate in the traction direction. If the overall cooling is too slow, the interfacial diffusion area already formed in S3 may continue to expand, leading to blurred boundaries of the thin barrier layer or excessive migration of functional components to adjacent layers. Therefore, this step establishes a sequential partitioning shaping process based on the unit width heat load corresponding to the in-mold compensated mass flow rate of each layer.

[0072] Specifically, the cooling area from the die exit to the final traction roller is sequentially divided into an interface locking zone, a layer stabilization zone, and a stress release zone. The interface locking zone is located immediately adjacent to the die exit. Its function is not to completely solidify all layer materials, but rather to preferentially reduce the molecular chain migration ability near adjacent interfaces, ensuring that the interface fusion structure formed by S3 maintains continuous bonding while preventing significant material cross-linking. The controller determines the proportion of heat carried by different layers based on the compensated mass flow rate within each layer of the die, and sets the upper and lower surface temperatures of the interface locking zone in conjunction with the lower limit of thermal stability of adjacent layer materials and the interface fusion energy density. When the mass flow rate of the outer layer near the upper surface is large, the heat transfer intensity of the upper cooling medium is increased; when the mass flow rate of the heat-sealing layer near the lower surface is large, the contact pressure and heat transfer duration of the lower cooling roller are increased. For the outer layer with a high polylactic acid content, the interface locking zone temperature is preferably controlled above its obvious crystallization temperature range but below the melt free flow temperature, so that it first forms a surface skeleton with a certain strength; for the barrier layer with a high thermoplastic starch or polyvinyl alcohol content, it is best to avoid rapid cooling to below the glass transition temperature in this area to prevent the migration of moisture in the layer from being hindered and the formation of micropores.

[0073] The layer stabilization zone, located after the interface locking zone, gradually brings each layer, which provides support, barrier, heat sealing, and surface protection, to a state capable of withstanding traction loads. The controller adjusts the surface temperature of the cooling roller, the cooling roller wrapping angle, the airflow velocity, and the sheet passage time based on the in-mold compensation mass flow rate, target thickness, and material crystallization characteristics of each layer. Support layers with higher mass flow rates have higher heat loads and longer internal cooling times; the controller extends the roller surface contact path on the corresponding side to gradually reduce their internal temperature, rather than simply lowering the cooling roller temperature. Barrier layers with lower mass flow rates primarily limit the difference in cooling rates to prevent inconsistent shrinkage between adjacent materials. For crystalline biodegradable polyesters, the layer stabilization zone retains a certain crystallization dwell window, allowing the material to form a uniform rather than surface-concentrated crystalline structure. For amorphous or low-crystallinity materials, a gradually decreasing cooling temperature is used to prevent rapid surface freezing while the interior remains at a high temperature.

[0074] Within the stable zone of the sheet, transverse zoned cooling is implemented based on the flow distribution of each layer. Due to the difference in heat dissipation conditions between the center and edge of the forming die, the edge area typically cools faster and shrinks more, easily leading to edge thickening or curling. This step involves setting up multiple independent heat exchange units along the material width direction and adjusting the cooling intensity of the corresponding areas according to the transverse flow distribution results obtained in S4. When the total flow rate of a certain transverse area is high, the circulation volume of the cooling medium in that area is increased or the contact time with the roller surface is extended; when the proportion of the barrier layer in a certain transverse area is too high, the sudden change in cooling intensity in that area is limited to prevent the thin barrier layer from cracking due to inconsistent shrinkage rates between the upper and lower materials. Continuous transition control is used between the transverse heat exchange units, and the temperature difference between adjacent units is preferably no more than 3–12 Kelvin to avoid forming new thermal stress boundaries in the sheet width direction.

[0075] The stress relief zone follows the layer stabilization zone, where the multilayer material has largely maintained its shape, but tensile and shrinkage stresses may still accumulate within each layer due to different cooling rates. This zone allows for limited molecular chain relaxation of each layer without restoring macroscopic flow through gentle reheating or a reduction in the final cooling intensity. For structures with a large difference in shrinkage between the upper and lower surfaces, the temperatures of the hot air or rollers on the upper and lower sides are adjusted to achieve a higher relaxation temperature on the side with greater shrinkage. For structures with a thinner intermediate barrier layer, the reheating temperature is limited to below its re-softening temperature to prevent secondary migration of the barrier layer. The stress relief zone also maintains low and stable tension, keeping the material in a flat, unfolded state.

[0076] Upon completion of this step, a set of cooling and shaping parameters is formed, including interface locking zone temperature, interface locking time, temperatures of each segment of the layer stabilization zone, heat transfer intensity of the upper and lower surfaces, cooling intensity of the transverse zones, stress release temperature, and corresponding time. This set of cooling and shaping parameters is updated according to the changes in the in-mold compensation mass flow rate of each layer output by S4: when the mass flow rate of a certain layer increases, the temperature of all cooling zones is not simply reduced proportionally; instead, the effective time for heat transfer to the outside of that layer is preferentially extended. When the interface fusion state approaches the allowable lower limit, the high-temperature free flow stage is shortened first, followed by a slow shaping process. This ensures that interface stabilization, layer thickness maintenance, and internal stress release form a continuous process with a clear sequence.

[0077] S6. Based on the cooling and shaping parameter group formed in step S5 and the in-mold compensation mass flow rate of each material layer obtained in step S4, the multi-layer biodegradable packaging material that has completed cooling and shaping is subjected to traction matching, layer structure state discrimination and layered writing of molding parameters to complete intelligent molding closed-loop control.

[0078] S6.1 Obtain the actual linear velocity, traction tension, temperature difference between the upper and lower surfaces, and length change of the multi-layer biodegradable packaging material when it leaves the stress release zone, and identify the thermal shrinkage state and traction extension state of the multi-layer biodegradable packaging material based on the traction tension and length change.

[0079] S6.2 When the length of the multi-layer biodegradable packaging material shortens under stable traction tension, reduce the speed difference between the front auxiliary traction roller and the main traction roller and extend the stress release time; when the traction tension increases and the length change is lower than the preset length change threshold, reduce the traction speed of the main traction roller.

[0080] S6.3. After completing the traction matching, test the total thickness, thickness of each material layer, transverse thickness uniformity, longitudinal thickness fluctuation, interface continuity, surface ripples, edge curling, and unit width traction tension of the multi-layer biodegradable packaging material. Then, correlate the test results with the plasticizing setting power, effective interface fusion energy density, in-mold compensation mass flow rate, and cooling and shaping parameter group within the corresponding control cycle.

[0081] S6.4 When it is detected that a material layer is lower than its target thickness in the entire width direction, the correction instruction is written back to step S4 to increase the in-mold compensation mass flow rate of the material layer; when it is detected that a material layer is lower than its target thickness in a local transverse region, the correction instruction is written back to step S4 to adjust the opening of the branch flow channel adjuster in the corresponding transverse region.

[0082] S6.5 When it is detected that the thickness of the material layer before the exit meets the target thickness but the overall longitudinal thinning occurs after cooling, reduce the traction speed of the main traction roller; when it is detected that the interface voids or insufficient interface continuity, write the correction instruction back to step S3 to extend the effective contact time of the melt of adjacent material layers, reduce the speed difference between the melt of adjacent material layers, or reduce the viscosity mismatch; when it is detected that the initial interface is continuous but interlayer cracking occurs after cooling, write the correction instruction back to step S5 to reduce the transverse cooling speed difference and extend the stress release time.

[0083] S6.6. Following the priority order of first correcting the material's thermal stability and interface continuity, then correcting the thickness of each material layer, and finally correcting the surface smoothness and edge curling, the plasticizing setting power, interface contact conditions, in-mold compensation mass flow rate, cooling and shaping parameter group, and traction speed are written back layer by layer until the thickness of each material layer, interface continuity, surface smoothness, and traction tension are within the corresponding allowable range for multiple consecutive control cycles. The current molding parameters are then determined as the stable molding parameters for the current material batch.

[0084] During implementation, after S5, the multilayer material possesses the basic strength to withstand traction and winding tension. However, material shrinkage, crystal orientation, and interfacial stress during cooling may still cause differences in the final layer thickness, total thickness, width, and flatness compared to the die exit state. Therefore, this step first matches the speed relationship between the main traction roller and the auxiliary traction roller based on the actual linear velocity of the material at the stress release zone exit, the temperature difference between the upper and lower surfaces, and the transverse shrinkage trend, rather than directly using the baseline linear velocity set in S1. The traction speed adjustment is based on the premise of not damaging the formed interlayer interface. The speed variation within a single control cycle is limited to avoid sudden increases in traction speed causing the thin barrier layer to be thinned longitudinally, or sudden decreases in traction speed causing material accumulation at the die exit.

[0085] During the traction matching process, the main traction roller is set as the reference execution unit to determine the final linear velocity, and the auxiliary rollers located before and after the stress release zone are set as tension isolation execution units. The controller identifies the thermal shrinkage trend based on the length and tension changes of the material between the two auxiliary rollers. When the material shortens in length under relatively stable tension, it is determined that thermal shrinkage still exists. The controller appropriately reduces the speed difference between the front auxiliary roller and the main traction roller and extends the residence time of the material in the stress release zone. When the material tension rises rapidly but the length change is not significant, it is determined that the current traction speed exceeds the allowable extension speed of the layer. The controller prioritizes reducing the main traction speed rather than forcibly increasing the material stiffness by increasing the cooling intensity. For materials with large temperature differences between the upper and lower surfaces, the controller uses the positional changes of the floating guide rollers to identify upward or downward bending trends and eliminates warping by fine-tuning the heat transfer intensity at the ends of the upper and lower surfaces, rather than using mechanical flattening to cover up internal residual stress.

[0086] After traction matching is completed, the final layer structure undergoes online quality status assessment before the material enters the winding or cutting unit. This assessment does not merely determine whether the product is qualified, but rather distinguishes the formation stages corresponding to different defects. The inspection includes total thickness, layer thickness, transverse thickness uniformity, longitudinal thickness fluctuation, interlayer interface continuity, surface ripples, edge curling, and unit width traction tension. For transparent multilayer packaging materials, multi-wavelength optical interferometry is used to detect layer thickness and interface continuity; for non-transparent materials containing biomass fillers, terahertz or multi-frequency ultrasonic methods are used to identify interlayer boundaries; for surface ripples and curling, surface height changes are obtained through a contour measurement unit set at a fixed angle. All inspection results are mapped to the in-mold compensation mass flow rate in S4 and the cooling and shaping parameter group in S5 according to the same control cycle, thus avoiding misalignment between parameters and inspection results at different time periods.

[0087] When a certain layer is thinner across its entire width, while the thickness of other layers and the total thickness remain relatively stable, the primary cause is determined to be insufficient in-mold compensation mass flow rate in that layer. In the next control cycle, the corresponding mass flow rate should be prioritized for improvement. While keeping the flow rates of other layers basically unchanged; when a layer is only thin in a local lateral region, the main cause is determined to be the lateral distribution of the die head or the local flow channel resistance. Instead of directly increasing the total flow rate of that layer, the opening of the throttling device in the corresponding lateral region is adjusted. If the predicted thickness before the outlet of each layer basically meets the requirements, but the overall longitudinal thinning occurs after cooling, the traction ratio is determined to be too large, and the main traction speed is corrected first; if the total thickness is stable but the barrier layer interface fluctuates, the effective fusion energy density of the interface corresponding to S3 and the interface locking zone parameters of S5 are checked back, and the speed difference between adjacent layers is reduced first or the interface locking is executed in advance, rather than increasing the final cooling intensity.

[0088] When interlayer delamination is detected, the controller further distinguishes between two scenarios: insufficient interfacial fusion and excessive cooling stress. If the delamination location is accompanied by obvious interfacial voids and the layer thickness has not changed significantly, a correction command is written back to S3 to increase the contact time between adjacent layers or reduce viscosity mismatch. If the interface is initially continuous but edge cracking occurs after material cooling, a correction command is written back to S5 to reduce the cooling rate difference between the lateral edge and the center and extend the stress release time. If both layer thickness fluctuations and interfacial delamination occur simultaneously, the controller executes the commands in the order of "stabilizing the interface first, then correcting the flow rate, and finally adjusting the traction" to avoid control oscillations caused by multiple execution units simultaneously adjusting in opposite directions.

[0089] This step also sets the priority for writing back the layered parameters. The first priority is safety states such as material thermal decomposition, excessive in-mold pressure, or interface continuity failure. When these states occur, the plasticizing setting power is immediately limited or the total mass flow rate is reduced. The second priority is functional states such as discontinuous barrier layer, partial loss of heat-sealing layer, and insufficient support layer thickness, which are written back to S3 or S4. The third priority is dimensional and appearance states such as slight deviation in total thickness, edge curling, and surface ripples, which are written back to S5 or the traction execution unit. Only after the previous priority state has stabilized can the next priority state be processed to prevent sacrificing interface bonding or material thermal stability in order to correct appearance defects.

[0090] Through the above write-back logic, the target mass flow rate and unit mass plasticizing energy requirement in S1 remain relatively stable as basic parameters for the batch; the plasticizing setting power in S2 is slowly corrected based on the actual energy input; the effective interfacial fusion energy density in S3 is corrected at a medium speed based on the interfacial continuity state; the in-mold compensation mass flow rate in S4 is corrected more quickly based on the layer thickness deviation; and the cooling and shaping parameters in S5 and the traction speed in this step are finely adjusted in real time based on the shrinkage and stress state. This forms a control structure with different time scales separated from each other, avoiding simultaneous large changes in all parameters within the same cycle. Finally, when the layer thickness, interfacial continuity, surface smoothness, and traction tension remain within the corresponding allowable range for multiple consecutive control cycles, the current plasticizing setting power, interfacial contact conditions, in-mold compensation mass flow rate, cooling and shaping parameter set, and traction speed are determined as the stable molding parameters for the current material batch, thus completing the intelligent molding closed loop of the multilayer biodegradable packaging material.

[0091] Example 2: This embodiment also provides a computer device applicable to a data-controlled intelligent molding method for multi-layer biodegradable packaging materials, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the data-controlled intelligent molding method for multi-layer biodegradable packaging materials as proposed in the above embodiment.

[0092] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements a data-controlled intelligent molding method for multilayer biodegradable packaging materials as proposed in the above embodiments.

[0093] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0094] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0095] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0096] More specific examples (a non-exhaustive list) of computer-readable media include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0097] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0098] 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, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A data-controlled intelligent molding method for multi-layer biodegradable packaging materials, characterized in that, Includes the following steps: S1. Based on the functional properties, target thickness and thermal properties of each material layer in the multi-layer biodegradable packaging material, establish the molding requirement mapping for each material layer and determine the target mass flow rate and unit mass plasticizing energy requirement for each material layer. S2. Based on the target mass flow rate and unit mass plasticizing energy required for each material layer determined in step S1, thermal and mechanical energy are coordinated and controlled for the independent extrusion unit corresponding to each material layer to obtain the plasticizing set power for each material layer. S3. Based on the plasticizing setting power of each material layer obtained in step S2, perform interfacial rheological matching on the melt of adjacent material layers entering the confluence composite zone to obtain the effective fusion energy density of the interface between each adjacent material layer. S4. Based on the effective fusion energy density of the interface between each adjacent material layer obtained in step S3, the interlayer mass flow rate of each material layer melt entering the forming die head is redistributed under interface constraints to obtain the in-die compensated mass flow rate of each material layer. S5. Based on the in-mold compensated mass flow rate of each material layer obtained in step S4 and the effective fusion energy density of the interface obtained in step S3, the multi-layer melt leaving the forming die head is subjected to segmented cooling and shaping to form a cooling and shaping parameter set. S6. Based on the cooling and shaping parameter group formed in step S5 and the in-mold compensation mass flow rate of each material layer obtained in step S4, the multi-layer biodegradable packaging material that has completed cooling and shaping is subjected to traction matching, layer structure state discrimination and layered writing of molding parameters to complete intelligent molding closed-loop control.

2. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 1, characterized in that, Step S1 further includes: Based on the wear-resistant protection, mechanical support, gas barrier, water vapor barrier and heat-sealing contact functions of each material layer in the multi-layer biodegradable packaging material, the multi-layer biodegradable packaging material is divided into layers to obtain the layer sequence, target thickness, material composition and thickness ratio of each material layer. Determine the target mass flow rate and energy requirement per unit mass for plasticizing each material layer; By correlating the layer sequence, target mass flow rate, and unit mass plasticizing energy requirement of each material layer, a layered molding demand mapping is formed for plasticizing control of each independent extrusion unit.

3. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 2, characterized in that, The determination of the target mass flow rate and unit mass plasticizing energy requirement for each material layer includes: The target mass flow rate of each material layer is determined based on the target thickness, equivalent density of the material, effective forming width of the multilayer biodegradable packaging material, and baseline velocity. Based on the average specific heat capacity, target plasticizing temperature, initial feed temperature, crystalline phase mass ratio, enthalpy of melt, feed water content, and initial apparent viscosity of each material layer, determine the unit mass plasticizing energy requirement for each material layer.

4. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 1, characterized in that, Step S2 further includes: The actual mass flow rate, heating power, screw torque and screw angular velocity of each independent extrusion unit in the current control cycle are obtained. Based on the effective heat transfer efficiency from the heater to the material melt and the effective efficiency of the conversion of screw mechanical work to melt shear heat, the actual input energy per unit mass of each material layer in the current control cycle is determined. The actual input energy per unit mass is compared with the plasticizing energy required per unit mass of the corresponding material layer to obtain the plasticizing energy deviation of each material layer. Based on the plasticizing energy deviation, the target mass flow rate of the corresponding material layer, and the preset plasticizing energy deviation correction coefficient, the plasticizing setting power of each independent extrusion unit in the next control cycle is determined.

5. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 4, characterized in that, The plasticizing setting power is allocated to the barrel heating power share and the screw mechanical power share based on the shear sensitivity and thermal stability temperature range of each material layer. Under the constraints of the upper limit of material thermal decomposition temperature, the upper limit of screw torque, the upper limit of barrel pressure, and the minimum stable mass flow rate, the plasticizing control of each independent extrusion unit is performed.

6. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 1, characterized in that, Step S3 further includes: Obtain the actual temperature, apparent viscosity, average interfacial velocity, effective contact length, effective contact area, and effective contact time when the melt from adjacent material layers enters the confluence and composite zone; The effective fusion energy density of the interface between adjacent material layers is determined based on the plasticizing setting power, effective contact time, effective contact area, interfacial energy conversion ratio, viscosity difference and temperature difference between the melts of adjacent material layers.

7. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 6, characterized in that, The effective fusion energy density of the interface is compared with the lowest interface fusion energy density and the highest safe interface fusion energy density of the corresponding adjacent material combinations: When the effective fusion energy density of the interface is lower than the minimum interface fusion energy density, the effective fusion energy density of the interface is increased by successively reducing the velocity difference between adjacent material layer melts, implementing local reheating for material layer melts with higher viscosity or lower temperature, and extending the effective contact time in the confluence composite zone. When the effective fusion energy density of the interface is higher than the maximum safe interface fusion energy density, excessive interdiffusion between adjacent material layers is limited by shortening the effective contact time or reducing the local heating power.

8. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 1, characterized in that, In step S4, after determining the in-mold compensation mass flow rate of each material layer, a total constraint is applied to the in-mold compensation mass flow rate of all material layers so that the sum of the in-mold compensation mass flow rate of each material layer is consistent with the current total extrusion mass flow rate. The in-mold compensation mass flow rate after the total constraint is converted into the rotation speed of the corresponding melt metering pump, the opening degree of the branch flow channel regulator, and the position of the variable throttling device.

9. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 1, characterized in that, Step S5 further includes: Along the conveying direction of the multi-layer melt from the forming die head to the traction unit, an interface locking zone, a layer stabilization zone, and a stress release zone are set sequentially. Based on the in-mold compensated mass flow rate of each material layer, the effective fusion energy density of the interface between adjacent material layers, the thermal stability temperature range of the material, and the flow state of the material near the interface, the upper and lower surface temperatures, heat transfer intensity, and interface locking time of the interface locking zone are determined to keep the interface between adjacent material layers continuously bonded and to limit further cross-contamination between material layers. Based on the in-mold compensation mass flow rate, target thickness, thermal diffusion characteristics and crystallization characteristics of each material layer, the cooling roller temperature, roller surface contact time, cooling airflow intensity and transverse zone heat transfer intensity in the stable zone of the layer are determined so that each material layer gradually reaches a stable state that can withstand traction load. Based on the temperature difference between the upper and lower surfaces of the multi-layer biodegradable packaging material, the shrinkage difference of each material layer, and the residual stress state, the relaxation temperature, passage time, and tension limit value of the stress release zone are determined so that each material layer can relax its molecular chains without restoring macroscopic flow. The control parameters of the interface locking zone, the layer stabilization zone, and the stress release zone are combined to form a cooling and shaping parameter set that matches the current material layer structure and the in-mold compensation mass flow rate.

10. The intelligent molding method for multi-layer biodegradable packaging materials based on data regulation according to claim 1, characterized in that, In step S6, the plasticizing power, interface contact conditions, in-mold compensation mass flow rate, cooling and shaping parameter group and traction speed are written back layer by layer according to the priority order of first correcting the thermal stability state and interface continuity state of the material, then correcting the thickness state of each material layer, and finally correcting the surface flatness and edge curling state. This process continues until the thickness of each material layer, interface continuity, surface flatness and traction tension are within the corresponding allowable range for multiple consecutive control cycles. The current molding parameters are then determined as the stable molding parameters for the current material batch.

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