Continuous production forming process for multi-layer co-extrusion foaming buffer cotton

Abstract

The invention relates to the technical field of foaming, and discloses a multi-layer co-extrusion foaming buffer cotton continuous production forming process which comprises the following steps: pretreating raw materials, respectively placing polyolefin resin, biodegradable polyester and foaming agent master batch in a vacuum drying oven, drying at 60 + / -5 DEG C for 2-4 hours, controlling the water content to be less than 0.1 wt%, melting and co-extruding to obtain the multi-layer co-extrusion foaming buffer cotton. When multi-layer co-extrusion synchronous foaming is carried out, by establishing a melt pressure dynamic threshold standard and setting differential pressure control parameters for different functional layers, the stability of interface bonding of all co-extrusion layers is guaranteed, and meanwhile, melt pressure fluctuation in the supercritical fluid injection process is subjected to feedback analysis in real time; according to the method, whether the problem of abnormal fluctuation of melt pressure occurs on a co-extrusion layer interface or not can be detected in real time, the structural integrity of interlayer bonding is guaranteed, the risk of cell collapse is further reduced, and when foaming ratio mismatch is detected, temperature field distribution can be adjusted in real time according to preset gradient foaming parameters.

Description

Technical Field

[0001] This invention relates to the field of foaming technology, specifically to a continuous production process for multi-layer co-extruded foamed cushioning cotton. Background Technology

[0002] Foaming, as an industrial term, refers to the process of forming a bubble structure inside plastics through physical, chemical, and mechanical methods, and is commonly used in the field of plastics processing.

[0003] Currently, due to various process limitations in the traditional production of cushioning cotton, the distribution of the injected foaming agent in the melt during multi-layer co-extrusion and synchronous foaming cannot be monitored in real time. When the melt pressure fluctuation exceeds the critical threshold, it will cause interlayer bonding failure and cell collapse, making it impossible to guarantee structural integrity.

[0004] Therefore, a continuous production process for multi-layer co-extruded foamed cushioning cotton is proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a continuous production process for multi-layer co-extruded foamed cushioning cotton, which solves the problems mentioned in the background technology that cause interlayer adhesion failure and cell collapse, thus failing to guarantee structural integrity.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a continuous production process for multi-layer co-extruded foamed cushioning cotton, comprising the following steps: Step 1: Raw material pretreatment: Place the polyolefin resin, biodegradable polyester, and foaming agent masterbatch separately in a vacuum drying oven and dry at 60±5℃ for 2-4 hours, controlling the moisture content to be less than 0.1wt%. Step 2, melt co-extrusion: The dried raw materials are melted and plasticized through three independent extruders. Extruder A processes the surface dense layer material, extruder B processes the core foam layer material, and extruder C processes the bottom reinforcement layer material. The melting temperatures are: Zone A 180±5℃, Zone B 160±5℃, and Zone C 175±5℃, respectively. Step 3, Dynamic foaming: The molten material is introduced into the multi-layer co-extrusion die, and supercritical CO2 fluid is injected into the core layer melt. The pressure is controlled at 15±2MPa, and gradient foaming is achieved under the action of the microporous foaming controller. Step 4: Online hot pressing and shaping: The foam is shaped by a double-roller hot press with an upper roller temperature of 110±5℃, a lower roller temperature of 90±5℃, a linear pressure of 50±5N / mm, and a traction speed of 3±0.5m / min. Step 5, Synchronous Cooling and Rewinding: After shaping, the material enters a two-stage cooling system. First, it is cooled with water mist to 60±3℃, then cooled with air to room temperature, and finally rewinded by an automatic tension control system.

[0007] Preferably, in step one, the polyolefin resin is a blend of metallocene linear low-density polyethylene and polypropylene in a weight ratio of 7:3 and a melt index of 2.5±0.5g / 10min. The biodegradable polyester is polybutylene succinate with a molecular weight of 15±20,000. The foaming agent masterbatch contains a complex of azodicarbonamide and trisodium citrate in a mass ratio of 3:1.

[0008] Preferably, the weight ratio of the three layers of raw materials in step two is as follows: surface dense layer 30±5wt%, core foam layer 50±5wt%, bottom reinforcement layer 20±5wt%, wherein the surface dense layer is supplemented with 2±0.5phr nano titanium dioxide light stabilizer and the bottom reinforcement layer is supplemented with 5±1phr basalt fiber.

[0009] Preferably, in step three, the multi-layer co-extrusion die head adopts a zoned temperature control design, with the die lip temperature gradient as follows: feed end 165±3℃ → middle 155±3℃ → discharge end 145±3℃, and the supercritical CO2 fluid injection amount is 8±0.5% of the core layer raw material weight.

[0010] Preferably, in step four, the roller spacing of the double-roller hot press is adjustable, with an adjustment range of 0.1±0.02mm to 5±0.5mm, and the roller surface is hard chrome plated with a roughness Ra of less than 0.05μm.

[0011] Preferably, in step five, the dual-stage cooling system is equipped with a temperature feedback device, the water mist cooling uses an ultrasonic atomizing nozzle with an aperture of 50±5μm, the water pressure is 0.5±0.1MPa, the air cooling system has a wind speed of 15±2m / s and a wind temperature of 18±2℃.

[0012] Preferably, the core foam layer contains a functional additive comprising hindered amine light stabilizer 770, organomontmorillonite, and carbon nanotubes in a mass ratio of 5:3:2, with the total addition amount being 3 ± 0.5% of the weight of the core layer raw materials.

[0013] Preferably, an online foaming monitoring system is set between steps three and four, including an X-ray densitometer and an infrared thermal imager, to detect the foaming ratio and the uniformity of cell distribution in real time.

[0014] Preferably, the winding process adopts a dual-station automatic roll changing system driven by a servo motor, with a roll diameter detection accuracy of ±0.1mm and a tension fluctuation range of ±0.5N.

[0015] Preferably, the functional additive is pretreated with plasma with the following parameters: argon atmosphere, power 500±50W, and treatment time 5±1min. After treatment, the surface energy of the additive is increased to 65±5mN / m.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention provides a continuous production process for multi-layer co-extruded foamed cushioning cotton, which has the following beneficial effects: 1. In this invention, during multi-layer co-extrusion synchronous foaming, by establishing a dynamic threshold standard for melt pressure and setting differentiated pressure control parameters for different functional layers, the stability of the interface bonding of each co-extrusion layer is ensured. At the same time, the melt pressure fluctuation during the supercritical fluid injection process is fed back and analyzed in real time, which can detect whether there is an abnormal fluctuation in melt pressure at the interface of the co-extrusion layer in real time, ensuring the structural integrity of the interlayer bonding and further reducing the risk of cell collapse.

[0017] 2. In this invention, during gradient foaming molding, the matching degree of the foaming ratio between the core layer and the surface layer is calculated, and it is determined in real time whether there is an imbalance in the expansion and contraction rates of each functional layer. This enables the system to reduce the probability of interlayer stress imbalance. Furthermore, when foaming ratio mismatch is detected, the temperature field distribution can be adjusted in real time according to the preset gradient foaming parameters, so that the foaming dynamics behavior can be dynamically corrected when there is interlayer stress imbalance, ensuring the accuracy of the gradient distribution of the cell structure.

[0018] 3. In this invention, during the continuous winding process, the foam body is automatically tracked in multiple regions, and the deformation recovery status of the cells in different temperature zones is monitored in real time. The shaping process parameters are compensated and adjusted in real time according to the trend of cell morphology change, so that the system can achieve dynamic and stable control of the cells throughout the entire process of the composite structure, reduce the occurrence of thickness fluctuations and surface defects in the finished product, and further improve the consistency of the mechanical properties of the cushioning cotton and the yield rate of production.

[0019] 4. In this invention, when blending and foaming bio-based materials, a distribution model of biodegradable active factors is established, and degradation rate matching parameters are set for different environmental conditions to ensure the controllability of the product's ecological compatibility. At the same time, the hydrolysis-sensitive groups of the polyester molecular chain are synergistically designed with the cell structure, which can optimize the microbial permeation channels of the cell wall in real time. This allows the system to reduce the residual risk of traditional foamed materials in the natural environment. Under composting conditions, the ester bond breaking mechanism can be activated according to the preset degradation kinetic curve, so that the material can trigger controllable degradation behavior as needed after disposal, further expanding the application scenarios of green buffer materials. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1, a continuous production process for multi-layer co-extruded foamed cushioning cotton, includes the following steps: Step 1: Raw material pretreatment: Place the polyolefin resin, biodegradable polyester, and foaming agent masterbatch separately in a vacuum drying oven and dry at 60±5℃ for 2-4 hours, controlling the moisture content to be less than 0.1wt%. Step 2, melt co-extrusion: The dried raw materials are melted and plasticized through three independent extruders. Extruder A processes the surface dense layer material, extruder B processes the core foam layer material, and extruder C processes the bottom reinforcement layer material. The melting temperatures are: Zone A 180±5℃, Zone B 160±5℃, and Zone C 175±5℃, respectively. Step 3, Dynamic foaming: The molten material is introduced into the multi-layer co-extrusion die, and supercritical CO2 fluid is injected into the core layer melt. The pressure is controlled at 15±2MPa, and gradient foaming is achieved under the action of the microporous foaming controller. Step 4: Online hot pressing and shaping: The foam is shaped by a double-roller hot press with an upper roller temperature of 110±5℃, a lower roller temperature of 90±5℃, a linear pressure of 50±5N / mm, and a traction speed of 3±0.5m / min. Step 5, Synchronous Cooling and Rewinding: After shaping, the material enters a two-stage cooling system, first cooling with water mist to 60±3℃, then air cooling to room temperature, and finally rewinding through an automatic tension control system; In step one, the polyolefin resin is a blend of metallocene linear low-density polyethylene and polypropylene in a weight ratio of 7:3 and a melt index of 2.5±0.5g / 10min. The biodegradable polyester is polybutylene succinate with a molecular weight of 15±20,000. The foaming agent masterbatch contains a complex of azodicarbonamide and trisodium citrate in a mass ratio of 3:1. In step two, the weight ratio of the three layers of raw materials is as follows: surface dense layer 30±5wt%, core foam layer 50±5wt%, bottom reinforcement layer 20±5wt%, wherein the surface dense layer is added with 2±0.5phr nano titanium dioxide light stabilizer and the bottom reinforcement layer is added with 5±1phr basalt fiber. In step three, the multi-layer co-extrusion die head adopts a zoned temperature control design, with the die lip temperature gradient as follows: 165±3℃ at the feed end → 155±3℃ in the middle → 145±3℃ at the discharge end. The supercritical CO2 fluid injection amount is 8±0.5% of the weight of the core layer raw material. In step four, the roller spacing of the twin-roll hot press is adjustable, ranging from 0.1±0.02mm to 5±0.5mm. The roller surface is hard chrome plated, with a roughness Ra of less than 0.05μm. In step five, the dual-stage cooling system is equipped with a temperature feedback device. The water mist cooling uses an ultrasonic atomizing nozzle with an aperture of 50±5μm, a water pressure of 0.5±0.1MPa, and the air cooling system has a wind speed of 15±2m / s and a wind temperature of 18±2℃. The core foam layer contains functional additives, including hindered amine light stabilizer 770, organomontmorillonite, and carbon nanotubes in a mass ratio of 5:3:2, with a total addition amount of 3±0.5% of the weight of the core layer raw materials; An online foaming monitoring system, including an X-ray densitometer and an infrared thermal imager, is set up between steps three and four to detect the foaming ratio and the uniformity of cell distribution in real time. The winding process adopts a dual-station automatic roll changing system driven by a servo motor, with a roll diameter detection accuracy of ±0.1mm and a tension fluctuation range of ±0.5N. The functional additives were pretreated with plasma. The treatment parameters were: argon atmosphere, power 500±50W, treatment time 5±1min. After treatment, the surface energy of the additives was increased to 65±5mN / m.

[0022] Example 2, a continuous production process for multi-layer co-extruded foamed cushioning cotton, includes the following steps: Step 1: Raw material pretreatment: Place the polyolefin resin, biodegradable polyester, and foaming agent masterbatch separately in a vacuum drying oven and dry at 60±5℃ for 2-4 hours, controlling the moisture content to be less than 0.1wt%. Step 2, melt co-extrusion: The dried raw materials are melted and plasticized through three independent extruders. Extruder A processes the surface dense layer material, extruder B processes the core foam layer material, and extruder C processes the bottom reinforcement layer material. The melting temperatures are: Zone A 180±5℃, Zone B 160±5℃, and Zone C 175±5℃, respectively. Step 3, Dynamic foaming: The molten material is introduced into the multi-layer co-extrusion die, and supercritical CO2 fluid is injected into the core layer melt. The pressure is controlled at 15±2MPa, and gradient foaming is achieved under the action of the microporous foaming controller. Step 4: Online hot pressing and shaping: The foam is shaped by a double-roller hot press with an upper roller temperature of 110±5℃, a lower roller temperature of 90±5℃, a linear pressure of 50±5N / mm, and a traction speed of 3±0.5m / min. Step 5, Synchronous Cooling and Rewinding: After shaping, the material enters a two-stage cooling system, first cooling with water mist to 60±3℃, then air cooling to room temperature, and finally rewinding through an automatic tension control system; In step one, the polyolefin resin is a blend of metallocene linear low-density polyethylene and polypropylene in a weight ratio of 7:3 and a melt index of 2.5±0.5g / 10min. The biodegradable polyester is polybutylene succinate with a molecular weight of 15±20,000. The foaming agent masterbatch contains a complex of azodicarbonamide and trisodium citrate in a mass ratio of 3:1. In step two, the weight ratio of the three layers of raw materials is as follows: surface dense layer 30±5wt%, core foam layer 50±5wt%, bottom reinforcement layer 20±5wt%, wherein the surface dense layer is added with 2±0.5phr nano titanium dioxide light stabilizer and the bottom reinforcement layer is added with 5±1phr basalt fiber. In step three, the multi-layer co-extrusion die head adopts a zoned temperature control design, with the die lip temperature gradient as follows: 165±3℃ at the feed end → 155±3℃ in the middle → 145±3℃ at the discharge end. The supercritical CO2 fluid injection amount is 8±0.5% of the weight of the core layer raw material. In step four, the roller spacing of the twin-roll hot press is adjustable, ranging from 0.1±0.02mm to 5±0.5mm. The roller surface is hard chrome plated, with a roughness Ra of less than 0.05μm. In step five, the dual-stage cooling system is equipped with a temperature feedback device. The water mist cooling uses an ultrasonic atomizing nozzle with an aperture of 50±5μm, a water pressure of 0.5±0.1MPa, and the air cooling system has a wind speed of 15±2m / s and a wind temperature of 18±2℃. The core foam layer contains functional additives, including hindered amine light stabilizer 770, organomontmorillonite, and carbon nanotubes in a mass ratio of 5:3:2, with a total addition amount of 3±0.5% of the weight of the core layer raw materials; An online foaming monitoring system, including an X-ray densitometer and an infrared thermal imager, is set up between steps three and four to detect the foaming ratio and the uniformity of cell distribution in real time. The winding process adopts a dual-station automatic roll changing system driven by a servo motor, with a roll diameter detection accuracy of ±0.1mm and a tension fluctuation range of ±0.5N. The functional additives were pretreated with plasma. The treatment parameters were: argon atmosphere, power 500±50W, treatment time 5±1min. After treatment, the surface energy of the additives was increased to 65±5mN / m.

[0023] Example 3, a continuous production process for multi-layer co-extruded foamed cushioning cotton, includes the following steps: Step 1: Raw material pretreatment: Place the polyolefin resin, biodegradable polyester, and foaming agent masterbatch separately in a vacuum drying oven and dry at 60±5℃ for 2-4 hours, controlling the moisture content to be less than 0.1wt%. Step 2, melt co-extrusion: The dried raw materials are melted and plasticized through three independent extruders. Extruder A processes the surface dense layer material, extruder B processes the core foam layer material, and extruder C processes the bottom reinforcement layer material. The melting temperatures are: Zone A 180±5℃, Zone B 160±5℃, and Zone C 175±5℃, respectively. Step 3, Dynamic foaming: The molten material is introduced into the multi-layer co-extrusion die, and supercritical CO2 fluid is injected into the core layer melt. The pressure is controlled at 15±2MPa, and gradient foaming is achieved under the action of the microporous foaming controller. Step 4: Online hot pressing and shaping: The foam is shaped by a double-roller hot press with an upper roller temperature of 110±5℃, a lower roller temperature of 90±5℃, a linear pressure of 50±5N / mm, and a traction speed of 3±0.5m / min. Step 5, Synchronous Cooling and Rewinding: After shaping, the material enters a two-stage cooling system, first cooling with water mist to 60±3℃, then air cooling to room temperature, and finally rewinding through an automatic tension control system; In step one, the polyolefin resin is a blend of metallocene linear low-density polyethylene and polypropylene in a weight ratio of 7:3 and a melt index of 2.5±0.5g / 10min. The biodegradable polyester is polybutylene succinate with a molecular weight of 15±20,000. The foaming agent masterbatch contains a complex of azodicarbonamide and trisodium citrate in a mass ratio of 3:1. In step two, the weight ratio of the three layers of raw materials is as follows: surface dense layer 30±5wt%, core foam layer 50±5wt%, bottom reinforcement layer 20±5wt%, wherein the surface dense layer is added with 2±0.5phr nano titanium dioxide light stabilizer and the bottom reinforcement layer is added with 5±1phr basalt fiber. In step three, the multi-layer co-extrusion die head adopts a zoned temperature control design, with the die lip temperature gradient as follows: 165±3℃ at the feed end → 155±3℃ in the middle → 145±3℃ at the discharge end. The supercritical CO2 fluid injection amount is 8±0.5% of the weight of the core layer raw material. In step four, the roller spacing of the twin-roll hot press is adjustable, ranging from 0.1±0.02mm to 5±0.5mm. The roller surface is hard chrome plated, with a roughness Ra of less than 0.05μm. In step five, the dual-stage cooling system is equipped with a temperature feedback device. The water mist cooling uses an ultrasonic atomizing nozzle with an aperture of 50±5μm, a water pressure of 0.5±0.1MPa, and the air cooling system has a wind speed of 15±2m / s and a wind temperature of 18±2℃. The core foam layer contains functional additives, including hindered amine light stabilizer 770, organomontmorillonite, and carbon nanotubes in a mass ratio of 5:3:2, with a total addition amount of 3±0.5% of the weight of the core layer raw materials; An online foaming monitoring system, including an X-ray densitometer and an infrared thermal imager, is set up between steps three and four to detect the foaming ratio and the uniformity of cell distribution in real time. The winding process adopts a dual-station automatic roll changing system driven by a servo motor, with a roll diameter detection accuracy of ±0.1mm and a tension fluctuation range of ±0.5N. The functional additives were pretreated with plasma. The treatment parameters were: argon atmosphere, power 500±50W, treatment time 5±1min. After treatment, the surface energy of the additives was increased to 65±5mN / m.

[0024] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example did not use supercritical CO2 fluid dynamic injection technology in the melt co-extrusion process.

[0025] Comparative Example 2 differs from Example 2 in that: this comparative example does not implement a zoned temperature control design in the multi-layer co-extrusion die head.

[0026] Comparative Example 3 differs from Example 3 in that the functional additives in this comparative example were not subjected to plasma pretreatment.

[0027] Comparative Example 4 differs from Example 3 in that the real-time melt pressure monitoring system was turned off during the online hot pressing and shaping process in this comparative example.

[0028] The performance of the multilayer co-extruded foamed cushioning cotton prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and test methods are as follows: Ball rebound rate test: The steel ball impact method is used. A 100g steel ball is dropped freely from a height of 500mm to impact the surface of the sample. The percentage of the rebound height of the steel ball to the initial height is measured. The test standard is GB / T6670-2008. Damp heat aging rate test: After being placed in an environment of 85℃ and 85% relative humidity for 168 hours, the thickness change rate and mass loss rate of the sample are measured. Test standard GB / T3512-2014. Flame retardant performance test: Based on the vertical combustion method, record the continuous burning time and burning length of the sample after it leaves the ignition source, according to the test standard GB / T2408-2021. Compression permanent deformation test: Apply 50 kPa pressure at 70℃ for 24 hours, unload and allow to recover for 30 minutes, then measure the unrecoverable deformation rate of the thickness. Test standard GB / T6669-2008.

[0029] The test data of the foamed cushioning cotton prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0030] By comparing and analyzing the data in the table, it can be seen that the multilayer co-extruded foamed cushioning cotton prepared using the processes in Examples 1-3 has significantly better performance than the cushioning cotton prepared using the processes in Comparative Examples 1-4. This indicates that during multilayer co-extrusion simultaneous foaming, by establishing a dynamic threshold standard for melt pressure and setting differentiated pressure control parameters for different functional layers, the stability of the interface bonding of each co-extruded layer can be ensured. Simultaneously, real-time feedback analysis of melt pressure fluctuations during supercritical fluid injection can detect abnormal melt pressure fluctuations at the co-extruded layer interface, ensuring the structural integrity of interlayer bonding and further reducing the risk of cell collapse. During gradient foaming molding, by calculating the foaming ratio matching degree between the core layer and the surface layer, it is possible to determine in real time whether there is an imbalance in the expansion and contraction rates of each functional layer. This allows the system to reduce the probability of interlayer stress imbalance. Furthermore, when a foaming ratio mismatch is detected, the temperature field distribution can be adjusted in real time according to preset gradient foaming parameters, enabling dynamic correction of foaming kinetics when interlayer stress imbalance occurs, ensuring the gradient distribution of the cell structure. To ensure fabric precision, during continuous winding, the system automatically tracks the morphology of the foam in multiple regions, monitors the deformation recovery status of cells in different temperature zones in real time, and adjusts the shaping process parameters in real time according to the trend of cell morphology changes. This enables the system to achieve dynamic and stable control of cells throughout the entire composite structure process, reducing thickness fluctuations and surface defects in the finished product, and further improving the consistency of mechanical properties and the yield of the cushioning cotton. When blending and foaming with bio-based materials, the system establishes a distribution model of biodegradable active factors and sets degradation rate matching parameters for different environmental conditions to ensure the controllability of the product's ecological compatibility. At the same time, the system co-designs the hydrolysis-sensitive groups of the polyester molecular chain with the cell structure, which can optimize the microbial penetration channels of the cell wall in real time. This allows the system to reduce the residual risk of traditional foamed materials in the natural environment. Under composting conditions, the system can activate the ester bond breaking mechanism according to the preset degradation kinetic curve, enabling the material to trigger controllable degradation behavior as needed after disposal, further expanding the application scenarios of green cushioning materials.

[0031] By comparing and analyzing the relevant data in the table, it can be seen that the multi-layer co-extruded foamed cushioning cotton prepared by the molding process of the present invention has stability, accurate gradient distribution and mechanical properties. This indicates that the continuous production molding process provided by the present invention has a broader market prospect and is more suitable for promotion.

[0032] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A continuous production process for multi-layer co-extruded foamed cushioning cotton, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Place the polyolefin resin, biodegradable polyester, and foaming agent masterbatch separately in a vacuum drying oven and dry at 60±5℃ for 2-4 hours, controlling the moisture content to be less than 0.1wt%. Step 2, melt co-extrusion: The dried raw materials are melted and plasticized through three independent extruders. Extruder A processes the surface dense layer material, extruder B processes the core foam layer material, and extruder C processes the bottom reinforcement layer material. The melting temperatures are: Zone A 180±5℃, Zone B 160±5℃, and Zone C 175±5℃, respectively. Step 3, Dynamic foaming: The molten material is introduced into the multi-layer co-extrusion die, and supercritical CO2 fluid is injected into the core layer melt. The pressure is controlled at 15±2MPa, and gradient foaming is achieved under the action of the microporous foaming controller. Step 4: Online hot pressing and shaping: The foam is shaped by a double-roller hot press with an upper roller temperature of 110±5℃, a lower roller temperature of 90±5℃, a linear pressure of 50±5N / mm, and a traction speed of 3±0.5m / min. Step 5, Synchronous Cooling and Rewinding: After shaping, the material enters a two-stage cooling system. First, it is cooled with water mist to 60±3℃, then cooled with air to room temperature, and finally rewinded by an automatic tension control system.

2. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 1, characterized in that: In step one, the polyolefin resin is a blend of metallocene linear low-density polyethylene and polypropylene in a weight ratio of 7:3 and a melt index of 2.5±0.5g / 10min. The biodegradable polyester is polybutylene succinate with a molecular weight of 15±20,000. The foaming agent masterbatch contains a complex of azodicarbonamide and trisodium citrate in a mass ratio of 3:

1.

3. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 1, characterized in that, In step two, the weight ratio of the three layers of raw materials is as follows: surface dense layer 30±5wt%, core foam layer 50±5wt%, bottom reinforcement layer 20±5wt%, wherein the surface dense layer is supplemented with 2±0.5phr nano titanium dioxide light stabilizer and the bottom reinforcement layer is supplemented with 5±1phr basalt fiber.

4. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 1, characterized in that, In step three, the multi-layer co-extrusion die head adopts a zoned temperature control design. The temperature gradient of the die lip is: 165±3℃ at the feed end → 155±3℃ in the middle → 145±3℃ at the discharge end. The amount of supercritical CO2 fluid injected is 8±0.5% of the weight of the core layer raw material.

5. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 1, characterized in that: In step four, the roller spacing of the double-roller hot press is adjustable, ranging from 0.1±0.02mm to 5±0.5mm. The roller surface is hard chrome plated, with a roughness Ra of less than 0.05μm.

6. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 1, characterized in that: In step five, the dual-stage cooling system is equipped with a temperature feedback device. The water mist cooling uses an ultrasonic atomizing nozzle with an aperture of 50±5μm, a water pressure of 0.5±0.1MPa, and the air cooling system has a wind speed of 15±2m / s and a wind temperature of 18±2℃.

7. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 3, characterized in that: The core foam layer is added with functional additives, including hindered amine light stabilizer 770, organomontmorillonite, and carbon nanotubes in a mass ratio of 5:3:2, with a total addition amount of 3±0.5% of the weight of the core layer raw materials.

8. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 1, characterized in that: An online foaming monitoring system, including an X-ray densitometer and an infrared thermal imager, is set up between steps three and four to detect the foaming ratio and the uniformity of cell distribution in real time.

9. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 1, characterized in that: The winding process employs a servo motor-driven dual-station automatic roll changing system with a roll diameter detection accuracy of ±0.1mm and a tension fluctuation range of ±0.5N.

10. The continuous production molding process for multi-layer co-extruded foamed cushioning cotton according to claim 7, characterized in that, The functional additive is pretreated with plasma with the following parameters: argon atmosphere, power 500±50W, and treatment time 5±1min. After treatment, the surface energy of the additive is increased to 65±5mN / m.

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