Production process of three-layer co-extrusion FFS heavy coating film

Abstract

The invention relates to the technical field of packaging film production, and discloses a production process of a three-layer co-extrusion FFS (fringe field switching) heavy coating film, which comprises the following steps: S1, selecting proper raw materials including an outer layer material, an inner layer material and a middle layer material; s2, drying the selected raw materials respectively to ensure that the moisture content is lower than 0.1%; s3, uniformly mixing different materials and additives through premixing equipment; s4, feeding the three materials into co-extrusion equipment, simultaneously extruding melt materials of different layers through a co-extrusion machine, and forming a multi-layer film structure through a die head; and S5, controlling the temperature and the flow speed at the die head to ensure the fluidity and the pressure distribution uniformity of the material melt of each layer. Through a dynamic stretching device, a pressure feedback control system, an optimized die head design and an intelligent control system, uniform film bubble expansion, accurate film thickness control and improvement of film quality stability are realized, the production efficiency and automation are improved, and the consistency and overall performance of film quality are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of packaging film production, in particular to a production process of a three-layer co-extruded FFS heavy packaging film. Background Art

[0002] At present, three-layer co-extrusion FFS (Form-Fill-Seale) heavy film technology is widely used in the packaging field of food, medicine, daily chemical and other industries. It is widely adopted due to its excellent barrier properties, heat resistance and mechanical strength. However, with the market's increasing requirements for packaging film quality and the need to improve production efficiency, the existing three-layer co-extrusion FFS heavy film technology faces a series of technical bottlenecks and challenges.

[0003] In the prior art, the production process of three-layer co-extruded FFS film mainly includes material pretreatment, co-extrusion, film blowing, cooling, traction and winding. In each process step, the expansion of the film bubble, the uniformity of the film thickness and the control of the film surface quality have always been technical problems. In the traditional film production process, the expansion state of the film bubble is often affected by the external environment, the characteristics of the film material and the operators, resulting in uneven film thickness distribution and even film surface defects such as bubbles and wrinkles. In order to ensure the quality of the film, the traditional method usually relies on manual adjustment of parameters such as the speed of the traction roller and the pressure of the air ring. However, this manual intervention not only reduces production efficiency, but also leads to large fluctuations in the quality of the film products, lack of consistency and stability.

[0004] In terms of film thickness control, in the prior art, the film thickness is usually adjusted by the temperature control and cooling system of the die. However, since the temperature control accuracy and temperature uniformity of the die cannot be accurately guaranteed, the thickness of the film still fluctuates greatly. Traditional die designs often have problems such as uneven temperature and uneven material flow, resulting in unstable physical properties of the film. Although some technical solutions have attempted to improve the uniformity of film thickness by optimizing the design of the die, the quality improvement of the film is still limited due to the difficulties in technical implementation.

[0005] In addition, the production speed of the membrane is also a major bottleneck in the current technology. In the existing technology, the production speed of the membrane is mainly limited by factors such as the expansion stability of the membrane bubble, the stretching ratio of the membrane bubble and the pulling speed, and these factors are often unable to be adjusted in real time during the production process. The traditional membrane production process relies on manual monitoring of the membrane bubble state and adjustment of operating parameters, which not only increases the complexity of the operation, but also causes low production efficiency and cannot achieve efficient and stable continuous production.

[0006] As the market's requirements for membrane quality continue to increase, the shortcomings of traditional technical solutions in terms of membrane bubble expansion control, membrane thickness uniformity, membrane surface quality and production efficiency are becoming increasingly obvious. Therefore, there is an urgent need for an innovative technology that can solve the instability problem in the membrane production process, improve membrane quality and enhance production efficiency. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a production process for a three-layer co-extruded FFS heavy-duty film, which solves the problems of uneven film bubble expansion, inaccurate film thickness control, multiple film surface defects and low production efficiency during the production of the three-layer co-extruded FFS heavy-duty film.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions: A production process of a three-layer co-extruded FFS heavy film, comprising the following steps:

[0009] S1. Select appropriate raw materials, including outer layer materials, inner layer materials and middle layer materials;

[0010] S2. Dry the selected raw materials separately to ensure that the moisture content is less than 0.1%;

[0011] S3, uniformly mix different materials and additives through pre-mixing equipment;

[0012] S4, feeding the three materials into a co-extrusion device, and simultaneously extruding the melt materials of different layers through the co-extruder and passing through a die head to form a multi-layer film structure;

[0013] S5. By controlling the temperature and flow rate at the die head, the fluidity and pressure distribution of the melt of each layer of material are ensured to be uniform;

[0014] S6, starting the film blowing machine to blow the extruded molten material into a film, and cooling it evenly through a cooling system, wherein a dynamic stretching device is used in the film blowing process to adjust the traction speed and the air ring pressure in real time;

[0015] S7. In step S6, a pressure feedback control system is used, and a pressure sensor is installed to monitor the pressure changes inside and outside the bubble and automatically adjust the pressure difference between the inside and outside;

[0016] S8, monitoring the thickness of the film through a real-time thickness measuring device, and adjusting the air ring, die opening and pulling speed according to the film thickness deviation to control the final thickness of the film;

[0017] S9. Use a thickness measuring device to monitor the film thickness in real time.

[0018] Preferably, the outer layer material in step S1 is polyethylene or polypropylene, wherein the density of polyethylene is 0.91 g / cm 3 Up to 0.92g / cm 3, the density of polypropylene is 0.90g / cm 3 Up to 0.91g / cm 3 .

[0019] Preferably, the intermediate layer material in step S1 is selected from nylon, polyester, ethylene-vinyl acetate copolymer or polyvinyl chloride, and its density is 1.10 g / cm 3 Up to 1.15g / cm 3 .

[0020] Preferably, the inner layer material in step S1 is polyester or nylon, wherein the density of polyester is 1.30 g / cm 3 Up to 1.35g / cm 3 , the density of nylon is 1.12g / cm 3 Up to 1.14g / cm 3 .

[0021] Preferably, the co-extrusion equipment in step S4 includes three independent extruders, each extruder is responsible for extruding different layers of materials, and the screw speed of the extruder for the outer layer material is set to 40-60rpm, the screw speed of the middle layer material is set to 30-45rpm, and the screw speed of the inner layer material is set to 30-45rpm.

[0022] Preferably, in the step S5, the temperature control range of the die head is 180° C.-220° C., and the air volume of the air ring of the cooling system is set to 20%-30%.

[0023] Preferably, in the step S8, the thickness of the film is monitored in real time by a laser scanner, and the thickness of the film is controlled between 50-150 μm, with a deviation within ±4 μm.

[0024] Preferably, the drying treatment in step S2 is mainly carried out by setting the temperature of the drying equipment to 70° C.-80° C. and the drying time to 4-6 hours.

[0025] Preferably, in step S6, the air flow intensity of the film blowing machine is set to 25%-30%, the air intake is controlled at 22%-27%, the exhaust is controlled at 2%-6%, and the traction speed is set at 2-5 m / min.

[0026] Preferably, the pressure feedback control system in step S6 includes:

[0027] The pressure sensor module is used to monitor the pressure changes inside and outside the bubble in real time. The inner bubble pressure sensor is installed inside the bubble, and the outer bubble pressure sensor is installed outside the bubble to measure the inner and outer pressures respectively.

[0028] Data acquisition and processing module, used to collect and process the data output by the pressure sensor, calculate the pressure difference inside and outside the membrane bubble, and filter data noise;

[0029] The control algorithm and decision-making module adjusts the pressure difference inside and outside the bubble in real time through PID control or other control algorithms, and adjusts the control parameters according to the stability requirements of the bubble;

[0030] The actuator module adjusts the air ring pressure and the traction roller speed according to the control signal, and controls the expansion and stability of the film bubble by adjusting the air volume and traction speed of the air ring;

[0031] The display and monitoring module is used to display the pressure difference inside and outside the membrane bubble, the air ring pressure, the traction speed and other data in real time, and provide warning and alarm functions to prevent defects on the membrane surface.

[0032] The present invention provides a production process for a three-layer co-extruded FFS heavy film, which has the following beneficial effects:

[0033] 1. The present invention optimizes the uniformity of bubble expansion and the control of film thickness by adopting a dynamic stretching device. By dynamically adjusting the traction roller speed and the air ring pressure, the present invention can accurately control the stretching ratio according to the real-time situation of bubble expansion, thereby avoiding defects such as wrinkles and bubbles on the film surface and effectively controlling the thickness change of the film. Compared with the solution in the prior art in which the traction speed and the air ring pressure are kept fixed, the thickness of the film is often difficult to maintain consistent, resulting in uneven bubble expansion or unstable surface quality. The technology of the present invention can achieve precise adjustment of the bubble and uniform control of the film thickness during the production process, thereby greatly improving the quality and consistency of the film product.

[0034] 2. The present invention adopts the technical solution of a pressure feedback control system to realize real-time monitoring and automatic adjustment of the pressure inside and outside the membrane bubble. By installing a pressure sensor and combining it with an intelligent control system, the system can automatically adjust the pressure difference inside and outside the membrane bubble according to the expansion of the membrane bubble to ensure the stability of the membrane bubble expansion. Compared with the prior art solution that relies on manual pressure adjustment, the membrane bubble is prone to instability during the expansion process, and the membrane surface may also produce unevenness or defects due to pressure fluctuations. Through the technology of the present invention, the quality of the membrane is more accurately controlled, and the phenomenon of uneven expansion of the membrane bubble is effectively solved, thereby reducing the defective rate in the membrane production process and improving the overall quality and production efficiency of the membrane.

[0035] 3. The present invention adopts an optimized die design and temperature control system to accurately control the die temperature during the film production process, thereby achieving uniform flow of each layer of material. The optimized die system can accurately adjust the melt fluidity of each layer of material through zoned temperature control and temperature sensors, thereby avoiding the problem of uneven temperature control in traditional die heads. Compared with the prior art solutions with inaccurate die temperature control and large temperature fluctuations, the thickness of the film often becomes uneven. The present invention ensures the uniformity of the film layer through precise temperature management, avoids uneven cooling and thickness changes on the film surface, makes the overall performance of the film more stable, and effectively reduces the scrap rate in the production process.

[0036] 4. The present invention adopts an intelligent control system, which achieves efficient automation of the membrane production process by real-time monitoring of the membrane bubble state and adjusting the air ring pressure and traction speed. The intelligent control system can automatically adjust the speed of the traction roller and the pressure of the air ring according to actual conditions during the expansion of the membrane bubble, thereby achieving membrane bubble stability and effectively adjusting the membrane thickness to avoid instability caused by manual adjustment. Compared with the prior art solutions that rely on manual adjustment, manual operation is not only inefficient, but also easily leads to fluctuations in membrane quality and increased membrane surface defects. The intelligent control system not only makes the membrane production process more automated, but also greatly improves production efficiency and membrane stability, thereby increasing output and membrane product quality and reducing the generation of defective products and waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the production process of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Please see attached Figure 1 The embodiment of the present invention provides a production process of a three-layer co-extruded FFS heavy film, comprising the following steps:

[0040] S1. Select appropriate raw materials, including outer layer materials, inner layer materials and middle layer materials;

[0041] S2. Dry the selected raw materials separately to ensure that the moisture content is less than 0.1%;

[0042] S3, uniformly mix different materials and additives through pre-mixing equipment;

[0043] S4, feeding the three materials into a co-extrusion device, and simultaneously extruding the melt materials of different layers through the co-extruder and passing through a die head to form a multi-layer film structure;

[0044] S5. By controlling the temperature and flow rate at the die head, the fluidity and pressure distribution of the melt of each layer of material are ensured to be uniform;

[0045] S6, starting the film blowing machine to blow the extruded molten material into a film, and cooling it evenly through a cooling system, wherein a dynamic stretching device is used in the film blowing process to adjust the traction speed and the air ring pressure in real time;

[0046] S7. In step S6, a pressure feedback control system is used, and a pressure sensor is installed to monitor the pressure changes inside and outside the bubble and automatically adjust the pressure difference between the inside and outside.

[0047] S8, monitoring the thickness of the film through a real-time thickness measuring device, and adjusting the air ring, die opening and pulling speed according to the film thickness deviation to control the final thickness of the film;

[0048] S9. Use a thickness measuring device to monitor the film thickness in real time.

[0049] The pressure feedback control system in step S6 includes:

[0050] The pressure sensor module is used to monitor the pressure changes inside and outside the bubble in real time. The inner bubble pressure sensor is installed inside the bubble, and the outer bubble pressure sensor is installed outside the bubble to measure the inner and outer pressures respectively.

[0051] Data acquisition and processing module, used to collect and process the data output by the pressure sensor, calculate the pressure difference inside and outside the membrane bubble, and filter data noise;

[0052] The control algorithm and decision-making module adjusts the pressure difference inside and outside the bubble in real time through PID control or other control algorithms, and adjusts the control parameters according to the stability requirements of the bubble;

[0053] The actuator module adjusts the air ring pressure and the traction roller speed according to the control signal, and controls the expansion and stability of the film bubble by adjusting the air volume and traction speed of the air ring;

[0054] The display and monitoring module is used to display the pressure difference inside and outside the membrane bubble, the air ring pressure, the traction speed and other data in real time, and provide warning and alarm functions to prevent defects on the membrane surface.

[0055] In step S6, the present invention introduces a pressure feedback control system, the purpose of which is to ensure the stability of bubble expansion and uniformity of film thickness during the film production process by accurately monitoring and adjusting the pressure inside and outside the bubble. The core of this system is to adjust the production parameters in real time through multi-module linkage to avoid uneven bubble expansion and film surface defects.

[0056] In this embodiment, the pressure sensor module is used to monitor the pressure changes inside and outside the bubble in real time. The internal pressure sensor of the bubble is installed inside the bubble, and the external pressure sensor is installed outside the bubble. The two pressure sensors measure the pressure difference between the inside and outside of the bubble respectively, and transmit the data to the subsequent processing module. The data acquisition and processing module processes the collected pressure data, calculates the pressure difference inside and outside the bubble, and effectively filters the noise in the data. The processed data is transmitted to the control algorithm and decision-making module, which adjusts the pressure difference inside and outside the bubble in real time according to the preset stability requirements through PID control or other control algorithms. Through this adjustment, the state of bubble expansion can be accurately controlled according to the stability requirements of the bubble, and the thickness distribution of the membrane can be optimized.

[0057] After receiving the control signal, the actuator module adjusts the air ring pressure and the traction roller speed. Specifically, the adjustment of the air volume and traction speed of the air ring can dynamically change the expansion speed and stability of the film bubble according to the expansion state of the film bubble. This process is realized through automatic control, which improves the accuracy and consistency of production compared with the traditional manual adjustment method.

[0058] In addition, the display and monitoring module is used to display key information such as the pressure difference inside and outside the membrane bubble, the air ring pressure, and the pulling speed in real time. This module not only provides real-time data monitoring functions, but also has warning and alarm functions, which can promptly remind the operator of abnormal conditions during the expansion of the membrane bubble and prevent defects on the membrane surface such as uneven thickness or surface wrinkles.

[0059] In one possible implementation, the pressure sensor module uses high-precision pressure sensors that can measure small pressure changes, thereby more accurately capturing changes in the film bubble. Through real-time feedback data, combined with the processing capabilities of the data acquisition and processing module, the pressure difference inside and outside the film bubble can be accurately calculated and quickly fed back to the control system. The control algorithm and decision-making module flexibly adjust the speed of the traction roller and the air ring pressure according to the pressure changes to ensure the stability of the film bubble during the production process.

[0060] The function of the actuator module is not limited to controlling the air ring pressure and traction speed, but can also adjust other key parameters in the film production process according to the control signal. For example, the air volume and wind speed of the cooling air ring can be adjusted to further ensure the stability of the film bubble expansion process. Through this multi-parameter control method, the expansion of the film bubble is more uniform and the thickness of the film is more stable, which greatly improves the quality of film production.

[0061] Generally, during the production process of the membrane bubble, external factors such as airflow changes and equipment stability may affect the expansion state of the membrane bubble, resulting in fluctuations in membrane thickness. The pressure feedback control system of the present invention can effectively eliminate these external interferences and improve the stability of the membrane bubble and the uniformity of the membrane. The introduction of this technology not only improves the stability of the membrane quality, but also improves production efficiency and reduces the generation of membrane waste while ensuring the stability of the membrane bubble.

[0062] As an option, advanced fuzzy control algorithms or neural network algorithms can be used in the control algorithm and decision module to further optimize the pressure regulation process. Through the optimization of these algorithms, the control of the membrane bubble expansion process can be made more flexible and accurate, and can adapt to the changing requirements of different material properties and production conditions, further improving the quality of the membrane and production stability.

[0063] Example 1: Film production using a dynamic stretching device

[0064] step:

[0065] Select the material: The outer layer uses polyethylene with a density of 0.91g / cm 3 ; The inner layer is made of polyester with a density of 1.32g / cm 3 ; The middle layer is made of nylon with a density of 1.13g / cm 3 .

[0066] Raw material drying: All materials are passed through the dryer separately and set at 75℃ for 4 hours to ensure that the moisture content is less than 0.1%.

[0067] Mixing process: The additives and raw materials are evenly mixed through pre-mixing equipment to ensure the mixing uniformity of each layer of materials.

[0068] Co-extrusion process: three raw materials are fed into the co-extrusion equipment, using three independent extruders, with screw speeds of 40rpm for the outer layer, 35rpm for the middle layer, and 30rpm for the inner layer. A three-layer film structure is formed through the die head.

[0069] Dynamic stretching: Start the film blowing machine and dynamically adjust the film stretching speed through the traction roller and air ring. The air ring pressure is set to 25% and the traction speed is adjusted to 3m / min to ensure the stability of the film bubble.

[0070] Pressure feedback control: Install pressure sensors inside and outside the bubble to monitor the bubble pressure changes in real time and adjust the pressure difference between inside and outside. Ensure the stability of the bubble by adjusting the air volume of the air ring and the speed of the traction roller.

[0071] Film thickness monitoring: The thickness of the film is monitored in real time by a laser scanner and controlled within the range of 50-150μm, with a deviation within ±4μm.

[0072] Film cooling: The air volume of the cooling system air ring is set to 25% to ensure rapid and uniform cooling of the film.

[0073] Example 2: Optimizing temperature control and die design

[0074] step:

[0075] Select the material: The outer layer uses polypropylene with a density of 0.91g / cm 3 ; The inner layer is made of nylon with a density of 1.14g / cm 3 The middle layer uses ethylene-vinyl acetate polymer and is dried continuously for 5 hours to ensure that the moisture content of all raw materials is less than 0.1%.

[0076] Formula mixing: Mix different materials and additives evenly in the batching bin to ensure accurate ratio of raw materials in each layer.

[0077] Co-extrusion: The three materials are fed into the co-extrusion equipment. The screw speed of each extruder is 45rpm for the outer layer, 40rpm for the middle layer, and 30rpm for the inner layer. The materials are evenly extruded through the precision die head.

[0078] Die temperature control: The die temperature is set to 180℃ to 210℃, and the temperature is evenly distributed to ensure consistent fluidity of each layer of material.

[0079] Film blowing: The film bubble is stably stretched by a dynamic stretching device, the traction roller speed is adjusted to 2.5m / min, and the air ring pressure is adjusted to 28% to ensure stable expansion of the film bubble.

[0080] Pressure feedback control: The pressure sensor monitors the pressure changes inside and outside the membrane bubble in real time, and dynamically adjusts the pressure difference inside and outside to ensure uniform expansion of the membrane bubble and avoid unevenness on the membrane surface.

[0081] Film thickness detection: Use a laser scanner to monitor the film thickness in real time to ensure that the thickness is between 50μm and 150μm, and the deviation is controlled within ±4μm.

[0082] Film cooling: The cooling air ring air volume is set to 20%, and the cooling speed of the film is optimized to avoid uneven temperature on the film surface.

[0083] Example 3: Application of pressure feedback control system

[0084] step:

[0085] Raw material selection: The outer layer material is polyethylene, the inner layer material is polyester, and the middle layer material is polyvinyl chloride. The density is 0.92g / cm 3 , 1.32g / cm 3 and 1.12 g / cm 3 .

[0086] Raw material drying: All raw materials pass through the drying equipment with a set temperature of 78°C and a drying time of 5 hours to ensure that the moisture content is less than 0.1%.

[0087] Mixing: Raw materials and additives are fully mixed in the mixing equipment to ensure the uniformity of each layer of material.

[0088] Co-extrusion process: The three materials are fed into the co-extrusion equipment and passed through three independent extruders, with the outer layer set at 45rpm, the middle layer at 40rpm, and the inner layer at 35rpm, to ensure that the melt of each layer is extruded evenly.

[0089] Die control: The die temperature is controlled between 180℃ and 220℃ to ensure that the material flows evenly in the die.

[0090] Film blowing process: Through the pressure feedback control system, the pressure sensor is installed to monitor the pressure inside and outside the film bubble in real time. The pressure difference between inside and outside is adjusted, the air ring pressure is set to 22%, and the traction speed is 2.8m / min to ensure the stable expansion of the film bubble.

[0091] Pressure feedback: Real-time adjustment of the internal and external pressure difference, adjusting the air ring pressure and traction roller speed through the control system to avoid uneven stretching of the film bubble.

[0092] Film thickness monitoring: The laser scanner monitors the film thickness in real time. The film thickness is controlled between 50-150μm and the deviation is controlled within ±4μm.

[0093] Film cooling: The air volume of the air ring is set to 20% to ensure uniform film cooling and avoid film defects caused by uneven heat.

[0094] Example 4: Production and optimization of high performance membranes

[0095] step:

[0096] Select the materials: Polypropylene for the outer layer, nylon for the inner layer, and ethylene-vinyl acetate copolymer for the middle layer. The density is 0.91g / cm 3 , 1.14g / cm 3 and 1.15g / cm 3 .

[0097] Drying treatment: The moisture content of the raw materials is controlled below 0.1% by drying equipment, the temperature is set at 72°C, and the drying time is 4 hours.

[0098] Recipe mixing: Additives are mixed with raw materials in mixing equipment to ensure uniform distribution of materials in each layer.

[0099] Co-extrusion: The three-layer material passes through three independent extruders, and the screw speed is set to 40rpm for the outer layer, 35rpm for the middle layer, and 30rpm for the inner layer. The material is extruded through a precision die head to form a multi-layer film structure.

[0100] Film blowing: The film blowing machine is started, the speed of the traction roller is set to 2.2m / min, and the air ring pressure is 24%. The film bubble expands evenly, and the film thickness is between 50μm and 150μm.

[0101] Pressure feedback control: Install a pressure sensor to monitor the pressure difference inside and outside the membrane bubble, automatically adjust the air ring pressure and traction speed to ensure the stability of the membrane bubble and avoid membrane surface defects.

[0102] Film thickness monitoring: The film thickness is monitored in real time by a laser scanner to ensure that the film thickness is controlled within a deviation range of ±4μm.

[0103] Cooling: The air volume of the cooling system air ring is set to 25% to ensure uniform cooling of the film and avoid defects caused by uneven cooling of the film surface.

[0104] Example 5: Film thickness control and quality stability

[0105] step:

[0106] Select the raw materials: the outer layer is polyethylene, the inner layer is polyester, and the middle layer is ethylene-vinyl acetate polymer. The density is 0.92g / cm 3 , 1.32g / cm 3 and 1.15g / cm 3 .

[0107] Drying treatment: Use drying equipment, set the temperature to 76℃, the drying time to 4h, and ensure that the moisture content is less than 0.1%.

[0108] Mixing: Mix different materials and additives evenly to ensure the uniformity of each layer of material.

[0109] Co-extrusion process: The three raw materials pass through three independent extruders, and the screw speed is set to 45rpm for the outer layer, 40rpm for the middle layer, and 35rpm for the inner layer to ensure uniform melt.

[0110] Die control: The die temperature is between 180℃ and 220℃, and the control system ensures uniform flow of each layer of material.

[0111] Film blowing: The pulling speed is 3m / min, and the air ring pressure is set to 25%. During the expansion of the film bubble, the pressure feedback control system automatically adjusts the air ring pressure and pulling speed to ensure the stability of the film bubble.

[0112] Pressure feedback: The pressure sensor monitors the pressure changes inside and outside the membrane bubble, and adjusts the pressure difference inside and outside the membrane bubble in real time to prevent wrinkles or uneven stretching on the membrane surface.

[0113] Film thickness detection: The film thickness is monitored in real time by a laser scanner. The film thickness is maintained at 50-150μm and the deviation is controlled within ±4μm.

[0114] Cooling: The air volume of the air ring is set to 20% to ensure uniform cooling of the film.

[0115] Comparative Example 1: Conventional film blowing process without dynamic stretching device

[0116] step:

[0117] Choose the material: polyethylene for the outer layer, polyester for the inner layer, and nylon for the middle layer.

[0118] Density: Polyethylene 0.91g / cm 3 , polyester 1.32g / cm 3 , nylon 1.13g / cm 3 .

[0119] Raw material drying: set the temperature of the drying equipment to 75°C and the drying time to 5h to ensure that the moisture content is less than 0.1%.

[0120] Mixing: Mix the raw materials and additives evenly in the mixing equipment.

[0121] Co-extrusion process: The three materials are fed into the extruder through the co-extrusion equipment. The outer layer screw speed is set to 45rpm, and the screw speed of the middle layer and the inner layer is set to 30rpm.

[0122] Die temperature control: The temperature of the die is controlled at 210°C to ensure the melt fluidity of each layer of material.

[0123] Film blowing: Traditional film blowing machine, the traction speed is set to 3m / min, and the air ring pressure is set to 30%.

[0124] Bubble stability: No dynamic stretching device is used, the pulling speed and air ring pressure remain constant and are not adjusted in real time.

[0125] Film thickness monitoring: The film thickness is monitored in real time by a laser scanner, with a control range of 50-150μm and a deviation of ±6μm.

[0126] Cooling: The cooling system air circulation air volume is set to 25%.

[0127] Comparative Example 2: Membrane production process without pressure feedback control system

[0128] step:

[0129] Choose the materials: Polypropylene for the outer layer, nylon for the inner layer, and ethylene-vinyl acetate copolymer for the middle layer.

[0130] Density: Polypropylene 0.91g / cm 3 , nylon 1.14g / cm 3 , ethylene-vinyl acetate polymer 1.14g / cm 3 .

[0131] Drying treatment: Use drying equipment, set the temperature to 80℃, the drying time to 5h, and ensure that the moisture content is less than 0.1%.

[0132] Formula mixing: Raw materials and additives are evenly mixed through mixing equipment to ensure accurate distribution ratio of each layer of materials.

[0133] Co-extrusion: The raw materials were fed through three independent extruders, and the screw speeds of the outer layer, inner layer and middle layer materials were set to 45rpm for the outer layer, 40rpm for the middle layer and 30rpm for the inner layer, respectively.

[0134] Die temperature control: The die temperature is set to 210°C to ensure stable material fluidity.

[0135] Film blowing: The traction roller speed is set to 3m / min, the air ring pressure is 30%, and the film bubble expands.

[0136] Pressure control: No pressure feedback control system is used. The bubble pressure is set manually and cannot be adjusted in real time according to the changes in the bubble.

[0137] Film thickness monitoring: The film thickness is monitored by a laser scanner with a deviation range of ±6μm and a thickness control range of 50-150μm.

[0138] Cooling: The air volume of the cooling air ring is set to 22%.

[0139] Comparative Example 3: Membrane production process without intelligent control system

[0140] step:

[0141] Choose raw materials: polyethylene for the outer layer, polyester for the inner layer, and polyvinyl chloride for the middle layer.

[0142] Density: Polyethylene 0.92g / cm 3 , polyester 1.32g / cm 3 , polyvinyl chloride 1.12g / cm 3 .

[0143] Drying: Dry the raw materials through drying equipment, set the temperature to 78℃, the drying time to 5h, and ensure that the moisture content is less than 0.1%.

[0144] Formula mixing: The materials and additives of each layer are evenly mixed through pre-mixing equipment.

[0145] Co-extrusion process: The three layers of material are fed into the die head through three independent extruders, and the screw speed of the outer layer is set to 45rpm, the middle layer is 40rpm, and the inner layer is 35rpm.

[0146] Die head temperature control: The temperature is set to 210℃ to control the material flow.

[0147] Film blowing: The traction roller speed was set to 2.8 m / min, and the air ring pressure was set to 25%.

[0148] Bubble stability: No intelligent control system is used during the bubble expansion process. The control of the traction roller and the air ring relies on manual adjustment and cannot be automatically optimized according to the real-time status of the bubble.

[0149] Film thickness control: The film thickness is monitored by a laser scanner and controlled within the range of 50-150μm with a deviation of ±5μm.

[0150] Cooling: The cooling system air circulation air volume is set to 22%.

[0151] Comparative Example 4: Film production process using only conventional die and cooling system

[0152] step:

[0153] Select raw materials: the outer layer material is polypropylene, the inner layer is nylon, and the middle layer is ethylene-vinyl acetate polymer.

[0154] Density: Polypropylene 0.91g / cm 3 , nylon 1.14g / cm 3 , ethylene-vinyl acetate polymer 1.15g / cm 3 .

[0155] Drying treatment: Set the temperature of the drying equipment to 72°C and the drying time to 4 hours to ensure that the moisture content is less than 0.1%.

[0156] Raw material mixing: Mix the materials with additives through pre-mixing equipment to ensure the uniformity of each layer of material.

[0157] Co-extrusion process: Three independent extruders were used, and the screw speeds of the outer layer, inner layer and middle layer materials were set to 40rpm for the outer layer, 35rpm for the middle layer and 30rpm for the inner layer to ensure uniform extrusion.

[0158] Die temperature control: The die temperature is set at 200°C to 210°C to ensure uniform melt flow.

[0159] Film blowing process: the traction speed is set to 3m / min, and the air ring pressure is set to 28%.

[0160] Cooling: The air volume of the cooling system air ring is set to 20% to cool the film quickly.

[0161] Membrane bubble monitoring: The membrane bubble expansion does not use a pressure feedback control system, and the pressure difference is controlled manually.

[0162] Film thickness monitoring: The film thickness is monitored by a laser scanner and the thickness is controlled at 50-150μm with a deviation of ±6μm.

[0163] Experiment 1: Verification of the effect of dynamic stretching device

[0164] Experimental purpose: The main purpose of this experiment is to compare and verify the improvement effect of the dynamic stretching device in the present invention on the stability of the film bubble and the uniformity of the film thickness during the film blowing process.

[0165] Experimental steps and design:

[0166] Experimental group (Example 1: dynamic stretching device):

[0167] The outer layer material is polyethylene, the inner layer material is polyester, and the middle layer is nylon.

[0168] The screw speed of each layer of material is 40rpm for the outer layer, 35rpm for the middle layer, and 30rpm for the inner layer. The drying temperature of all raw materials is set at 75℃ and the drying time is 5h.

[0169] The film blowing process uses a dynamic stretching device. The traction roller speed is set to 3m / min, the air ring pressure is adjusted in real time, the initial air ring pressure is set to 25%, and it is adjusted to 22%-28% according to the expansion of the film bubble. The film thickness is monitored in real time by a laser scanner to ensure that the film thickness is controlled between 50-150μm and the deviation is controlled within ±4μm.

[0170] Comparative group (Comparative Example 1: conventional film blowing process without dynamic stretching device):

[0171] Using the same raw materials, the drying temperature was set to 75 °C, the drying time was 5 h, and the extruder screw speed was set to 40 rpm for the outer layer, 35 rpm for the middle layer, and 30 rpm for the inner layer.

[0172] The film blowing process adopts the traditional process, the traction roller speed is set to 3m / min, the air ring pressure is kept fixed at 30%, and no real-time adjustment is made. The film thickness is monitored by a laser scanner, and the film thickness deviation is ±6μm.

[0173] Experimental parameter settings:

[0174] Bubble expansion: During the bubble expansion process, the dynamic stretching device in the experimental group will adjust the traction roller speed and air ring pressure in real time according to the stability of the bubble; while the control group only relies on manual setting of the traction roller and air ring pressure.

[0175] Film thickness uniformity: Monitor the film thickness by laser scanner, record the film thickness deviation, and compare the uniformity of different groups of films.

[0176] Data recording: record the film thickness (unit: μm), film surface defects (such as wrinkles, bubbles, etc.), film stretch ratio, film production speed (unit: kg / h) and other data of each sample during the film blowing process. Draw the comparative results of the experimental data into a table and analyze them.

[0177] Experimental results data:

[0178] Table 1: Comparison of membrane production process parameters

[0179]

[0180]

[0181] Experimental summary: The application of the dynamic stretching device significantly improved the uniformity of the membrane thickness and the stability of the membrane bubble. Experimental data show that the deviation of the membrane thickness in the experimental group was controlled within ±4μm, while the membrane thickness deviation of the comparison group was as high as ±6μm to ±8μm, indicating that the present invention has obvious advantages in membrane quality control. During the expansion of the membrane bubble, the experimental group was able to effectively avoid the occurrence of membrane surface defects (such as wrinkles, bubbles, etc.) by adjusting the traction speed and wind ring pressure in real time, while the comparison group had a significant increase in membrane surface defects due to the lack of real-time adjustment. In addition, the membrane production speed of the experimental group has also been improved to a certain extent, indicating that this technology can not only improve membrane quality, but also provide advantages in improving production efficiency.

[0182] From the perspective of bubble stability, the experimental group showed good stability during bubble expansion and did not have the problem of uneven expansion. On the contrary, due to the fixed air ring pressure in the control group, the bubble could not be effectively adjusted during expansion, resulting in uneven membrane surface and even membrane rupture. There was also a difference in the membrane stretching ratio between the experimental group and the control group. The membrane in the experimental group showed a higher stretching ratio and uniform stretching effect during the stretching process, while the membrane in the control group lacked precise control and the bubble expanded unevenly, resulting in unstable membrane stretching effect.

[0183] Experiment 2: Verification of the effect of pressure feedback control system

[0184] Experimental purpose: This experiment aims to verify the effect of the pressure feedback control system in the present invention on membrane bubble stability, membrane thickness uniformity, membrane quality control, etc. during the membrane production process.

[0185] Experimental steps and design:

[0186] Experimental group (Example 2: pressure feedback control system): using polypropylene as the outer layer material, nylon as the inner layer material, and ethylene-vinyl acetate copolymer as the middle layer, the material density is 0.91g / cm 3 , 1.24g / cm 3 and 1.14 g / cm 3 . According to the process settings of Example 2, the three layers of material pass through three independent extruders respectively, the screw speed of the outer layer is set to 45rpm, the middle layer is set to 40rpm, and the inner layer is 30rpm. All raw materials are dried at a temperature of 80°C and a drying time of 4h. During the co-extrusion process, the die temperature is controlled at 210°C, and the air ring pressure is adjusted in real time within the range of 22%-28%. The speed of the traction roller is set to 2.5m / min. The stability of the bubble is monitored in real time by a pressure feedback control system that monitors the changes in the internal and external pressures of the bubble, and automatically adjusts the internal and external pressure difference to ensure that the bubble is stable and the membrane surface is free of defects.

[0187] Comparative group (Comparative Example 2: No pressure feedback control system used): Using the same raw materials, the drying process was the same as the experimental group, and the screw speed was set to 45rpm for the outer layer, 40rpm for the middle layer, and 30rpm for the inner layer. The die temperature was set to 210°C, and the air ring air volume of the cooling system was 25%. The air ring pressure was set to 30%, and the pulling roller speed was 3m / min. This comparative group did not use a pressure feedback control system. The pressure inside and outside the bubble was only set manually, and no real-time adjustment was performed.

[0188] Experimental design:

[0189] Bubble monitoring: The experimental group used a pressure sensor to monitor the pressure changes inside and outside the bubble in real time, and adjusted the air ring pressure and traction roller speed through an intelligent control system. The control group used manual pressure control, which could not be adjusted in real time according to the expansion of the bubble.

[0190] Film thickness control: The film thickness is monitored in real time by a laser scanner, and the film thickness data is recorded. The film thickness is controlled within the range of 50-150μm, and the deviation is controlled within ±4μm (experimental group), while the film thickness deviation of the control group is ±6μm.

[0191] Membrane surface defects: record whether there are wrinkles, bubbles and other defects on the membrane surface, and count the number of defects.

[0192] Data recording: record the film thickness (unit: μm), film thickness deviation, film production speed (unit: kg / h), film surface defects (pieces / meter) and other data of each sample. Compare the results of the experimental group and the control group through a table.

[0193] Experimental results data:

[0194] Table 2: Comparison of membrane production process and membrane quality

[0195]

[0196]

[0197] Experimental summary: The experimental results show that the pressure feedback control system has significant advantages in improving membrane quality and production efficiency. The membrane thickness deviation in the experimental group was controlled within ±4μm, while the membrane thickness deviation in the comparison group was as high as ±6μm to ±8μm, demonstrating the superiority of the technology of the present invention in membrane thickness uniformity. With the application of the pressure feedback system, the expansion of the membrane bubble was better controlled and the membrane surface defects were significantly reduced. The membrane surface defects in the experimental group were zero, while the comparison group had up to 8 defects per meter of membrane surface defects.

[0198] From the perspective of bubble stability, the real-time pressure adjustment system used in the experimental group significantly improved the stability of the bubble. During the membrane production process, the pressure inside and outside the bubble is monitored and feedback-regulated in real time to ensure uniform expansion of the bubble, avoiding the problem of bubble collapse or uneven expansion. In contrast, the control group lacks a pressure feedback control system, and the bubble is prone to instability during expansion, resulting in an uneven membrane surface or even rupture.

[0199] By comparing the membrane production speed, the production efficiency of the experimental group is also better than that of the control group, mainly due to the guaranteed stability of the membrane bubble, improved uniformity of membrane quality, and reduced downtime during the production process. The membrane production speed of the experimental group is generally higher than that of the control group, indicating that the pressure feedback control system not only improves the membrane quality, but also optimizes the production efficiency.

[0200] Experiment 3: Verification of the effect of the die head temperature control system

[0201] Experimental purpose: This experiment aims to verify the effect of the optimized die head temperature control system and design in the film production process.

[0202] Experimental steps and design:

[0203] Experimental group (Example 3: Optimization of die head temperature control and design): The outer layer material is polyethylene, the inner layer material is polyester, and the middle layer is polyvinyl chloride. The density of the outer layer material is 0.92g / cm 3 , the inner layer density is 1.32g / cm 3 , the density of the middle layer is 1.12g / cm 3. All raw materials are set to a temperature of 78°C and a drying time of 5h through the drying equipment to ensure that the moisture content is less than 0.1%. The extruder screw speed is set to 45rpm for the outer layer, 40rpm for the middle layer, and 30rpm for the inner layer. The temperature setting range of the die head temperature control system is 180°C to 220°C, and the temperature of each area is accurately controlled to ensure uniform flow of the material. The real-time adjustment range of the air ring pressure is 22%-26%, and the traction speed is set to 2.8m / min. The film thickness is monitored in real time by a laser scanner to ensure that the film thickness range is 50-150μm and the deviation is controlled within ±4μm.

[0204] Comparative group (Comparative Example 3: Traditional die design and cooling system): Using the same raw materials, the outer layer material is polypropylene, the inner layer material is polyester, and the middle layer is ethylene-vinyl acetate polymer. The extruder screw speed is set to 45rpm for the outer layer, 40rpm for the middle layer, and 35rpm for the inner layer. The raw material drying temperature is 78°C and the drying time is 5h. The die temperature control system is set to a traditional design with a temperature range of 210°C, and no regional precise temperature control is performed. The cooling air ring air volume is set to 20%. The air ring pressure is fixed at 25%, the traction speed is set to 2.8m / min, and the film thickness is monitored by a laser scanner with a deviation of ±6μm.

[0205] Experimental design:

[0206] Die temperature control and design: The optimized die temperature control system in the experimental group has precise regional temperature control to ensure consistent fluidity of each layer of material. The control group uses a traditional die with low temperature control accuracy and uneven die temperature.

[0207] Film thickness control and uniformity: The film thickness was monitored in real time. The film thickness deviation in the experimental group was controlled within ±4μm, while the film thickness deviation in the comparison group was larger, reaching ±6μm.

[0208] Membrane surface defects: record whether there are wrinkles, bubbles and other defects on the membrane surface. The experimental group effectively avoided membrane surface defects through a precise temperature control system.

[0209] Data recording: record the film thickness (unit: μm), film thickness deviation, film surface defects (pieces / meter), production speed (unit: kg / h) and other data of each sample. Display the data in a table.

[0210] Experimental results data:

[0211] Table 3: Comparison of membrane production process and membrane quality

[0212]

[0213]

[0214] Experimental summary: The optimized die temperature control system significantly improves the uniformity of film quality, especially in terms of bubble stability. In the experimental group, the temperature of each area was reasonably regulated through the precise die temperature control system, ensuring that the materials of each layer flowed consistently during the coextrusion process, thereby reducing the film thickness deviation. Compared with the control group, the film thickness deviation of the experimental group was controlled within ±4μm, while that of the control group reached ±6μm or even greater. This difference shows that the application of the die temperature control system of the present invention in film production improves the uniformity and stability of the film.

[0215] In terms of film surface defects, the experimental group had zero film surface defects, while the control group had obvious defects such as wrinkles and bubbles. This phenomenon was attributed to the precise temperature control design of the die in the experimental group, which avoided film surface defects caused by uneven heat. In the control group, due to the low temperature control accuracy of the traditional die design, uneven temperature distribution was easily generated on the film surface, which led to unstable film quality.

[0216] In terms of production speed, the film production speed of the experimental group is generally higher than that of the control group. As the stability of the film bubble is improved, the quality of the film is more uniform, the downtime in the production process is reduced, and the production efficiency is naturally improved. These results further prove the effectiveness of the die head temperature control system of the present invention and highlight its innovation in improving film quality and production efficiency.

[0217] Experiment 4: Verification of the effectiveness of the intelligent control system

[0218] Purpose of the experiment: This experiment aims to verify the effect of the intelligent control system in the present invention in the membrane production process, especially its advantages in terms of uniformity of membrane quality, stability of membrane bubbles and production efficiency.

[0219] Experimental steps and design:

[0220] Experimental group (Example 4: Intelligent control system): The outer layer material is polypropylene, the inner layer material is nylon, and the middle layer is ethylene-vinyl acetate copolymer. The outer layer density is 0.91g / cm 3 , the inner layer density is 1.14g / cm 3 , the density of the middle layer is 1.15g / cm 3 . The extruder screw speeds are 40rpm for the outer layer, 35rpm for the middle layer, and 30rpm for the inner layer. The raw material drying temperature is 72°C and the drying time is 4h. The temperature of the die head temperature control system is set to 180°C to 220°C to ensure uniform temperature in each area. During the film blowing process, the intelligent control system adjusts the air ring pressure and traction speed in real time to maintain the stability of the film bubble. The traction speed is set to 2.2m / min, the air ring pressure range is 22%-26%, and the film thickness is monitored in real time by a laser scanner. The film thickness is controlled at 50-150μm, and the deviation is controlled within ±4μm.

[0221] Comparative group (Comparative example 4: no intelligent control system): using the same materials, the same raw material drying temperature and time, and the same screw speed. The die temperature control is set to the traditional design, the temperature is 200℃ to 210℃, the air ring pressure is fixed at 28%, and the traction speed is set to 3m / min. No intelligent control system is used. The traction speed and air ring pressure are set manually and cannot be dynamically adjusted according to the state of the film bubble.

[0222] Experimental design:

[0223] Intelligent control system: In the experimental group, the intelligent control system monitors the state of the membrane bubble in real time (such as internal and external pressure, membrane bubble expansion), and automatically adjusts the air ring pressure and traction speed to ensure the stability and uniformity of the membrane. The control group is manually operated and no automatic adjustment is achieved.

[0224] Bubble stability and film quality: Ensure uniform film thickness by real-time monitoring of bubble stability and detect film thickness deviations with a laser scanner.

[0225] Membrane surface defects: The experimental group uses an intelligent control system that can adjust the membrane bubble state in real time and reduce the appearance of membrane surface defects. The control group does not use intelligent control, and bubbles and wrinkles are prone to appear on the membrane surface.

[0226] Data recording: record the film thickness (unit: μm), film thickness deviation (unit: μm), film production speed (unit: kg / h), number of film surface defects (unit: pieces / meter) and other data of the experimental group and the comparative group. Compare and display the experimental data.

[0227] Experimental results data:

[0228] Table 4: Comparison of the impact of intelligent control systems on membrane quality and production efficiency

[0229]

[0230]

[0231] Experimental summary: By comparing the key parameters of the experimental group and the control group, such as membrane quality, membrane bubble stability, and membrane production speed, the results show that the application of the intelligent control system in the membrane production process significantly improves the membrane quality and optimizes the production efficiency. The membrane thickness deviation in the experimental group was controlled within ±4μm, and there were no defects on the membrane surface, while the membrane thickness deviation in the control group was as high as ±6μm to ±8μm, and there were many defects on the membrane surface. In terms of membrane production speed, the production speed of the experimental group was higher than that of the control group, indicating that the intelligent control system can not only improve the quality of the membrane, but also improve production efficiency.

[0232] In terms of bubble stability, the experimental group ensured the uniformity of bubble expansion through real-time adjustment of the intelligent control system, and effectively avoided the collapse or uneven expansion of the bubble. However, due to the lack of intelligent control, the bubble expansion of the control group was uneven, resulting in defects on the membrane surface, and even wrinkles and bubbles.

[0233] From the perspective of membrane production efficiency, the membrane production speed of the experimental group was significantly higher than that of the control group. Since the stability of the membrane bubble was guaranteed, the uniformity of the membrane quality was improved, the downtime in the production process was reduced, and the production efficiency was naturally improved. In contrast, the production efficiency of the control group was greatly affected due to the instability of the membrane bubble and the fluctuation of membrane quality.

[0234] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A production process for three-layer co-extruded FFS heavy film, characterized in that: The following steps are involved: S1. Select appropriate raw materials, including outer layer materials, inner layer materials and middle layer materials; S2. Dry the selected raw materials separately to ensure that the moisture content is less than 0.1%; S3, uniformly mix different materials and additives through pre-mixing equipment; S4, feeding the three materials into a co-extrusion device, and simultaneously extruding the melt materials of different layers through the co-extruder and passing through a die head to form a multi-layer film structure; S5. By controlling the temperature and flow rate at the die head, the fluidity and pressure distribution of the melt of each layer of material are ensured to be uniform; S6, starting the film blowing machine to blow the extruded molten material into a film, and cooling it evenly through a cooling system, wherein a dynamic stretching device is used in the film blowing process to adjust the traction speed and the air ring pressure in real time; S7. In step S6, a pressure feedback control system is used, and a pressure sensor is installed to monitor the pressure changes inside and outside the bubble and automatically adjust the pressure difference between the inside and outside. S8, monitoring the thickness of the film through a real-time thickness measuring device, and adjusting the air ring, die opening and pulling speed according to the film thickness deviation to control the final thickness of the film; S9. Use a thickness measuring device to monitor the film thickness in real time.

2. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: The outer layer material in step S1 is polyethylene or polypropylene, wherein the density of polyethylene is 0.91 g / cm 3 Up to 0.92g / cm 3 , the density of polypropylene is 0.90g / cm 3 Up to 0.91g / cm 3 .

3. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: The intermediate layer material in step S1 is selected from nylon, polyester, ethylene-vinyl acetate copolymer or polyvinyl chloride, and its density is 1.10 g / cm 3 Up to 1.15g / cm 3 .

4. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: In step S1, the inner layer material is polyester or nylon, wherein the density of polyester is 1.30 g / cm 3 Up to 1.35g / cm 3 , the density of nylon is 1.12g / cm 3 Up to 1.14g / cm 3 .

5. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: The co-extrusion equipment in step S4 includes three independent extruders, each extruder is responsible for extruding different layers of materials, and the screw speed of the extruder of the outer layer material is set to 40-60rpm, the screw speed of the middle layer material is set to 30-45rpm, and the screw speed of the inner layer material is set to 30-45rpm.

6. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: In the step S5, the temperature control range of the die head is 180° C.-220° C., and the air volume of the air ring of the cooling system is set to 20%-30%.

7. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: In the step S8, the thickness of the film is monitored in real time by a laser scanner, and the thickness of the film is controlled between 50-150 μm, with a deviation within ±4 μm.

8. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: The drying process in step S2 is mainly carried out by setting the temperature of the drying equipment to 70° C.-80° C. and the drying time to 4-6 hours.

9. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: In the step S6, the air flow intensity of the film blowing machine is set to 25%-30%, the air intake is controlled at 22%-27%, the exhaust is controlled at 2%-6%, and the traction speed is set at 2-5 m / min.

10. The production process of a three-layer co-extruded FFS heavy film according to claim 1, characterized in that: The pressure feedback control system in step S6 includes: The pressure sensor module is used to monitor the pressure changes inside and outside the bubble in real time. The inner bubble pressure sensor is installed inside the bubble, and the outer bubble pressure sensor is installed outside the bubble to measure the inner and outer pressures respectively. Data acquisition and processing module, used to collect and process the data output by the pressure sensor, calculate the pressure difference inside and outside the membrane bubble, and filter data noise; The control algorithm and decision-making module adjusts the pressure difference inside and outside the bubble in real time through PID control or other control algorithms, and adjusts the control parameters according to the stability requirements of the bubble; The actuator module adjusts the air ring pressure and the traction roller speed according to the control signal, and controls the expansion and stability of the film bubble by adjusting the air volume and traction speed of the air ring; The display and monitoring module is used to display the pressure difference inside and outside the membrane bubble, the air ring pressure, the traction speed and other data in real time, and provide warning and alarm functions to prevent defects on the membrane surface.

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