Preparation method of high-resilience yellowing-resistant PBAT supercritical foaming material, foaming material and application

Abstract

The invention relates to a preparation method of a high-resilience yellowing-resistant PBAT supercritical foaming material, the foaming material and application. The method comprises the following steps: S1, pre-drying PBAT and polyester aliphatic series; s2, mixing PBAT, polyester aliphatic series and a nucleating agent; s3, carrying out a melting reaction to form a polymer melt; s4, injecting supercritical carbon dioxide to be mixed with the polymer melt; s5, mixing and cooling to form a uniform melt; s6, extrusion and underwater girdling are carried out, and the PBAT foaming beads are prepared. The PBAT foaming material has high rebound resilience and yellowing resistance and is suitable for products such as shoe soles and the like. By optimizing the formula and the process, the light weight, efficient production and stability of the product are also realized, and the product has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the field of polymer material foaming, and in particular to a method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material, a foaming material prepared by the method, and application of the foaming material in the field of sole molding. Background Art

[0002] Polymer foam materials are a type of materials that use polymers as the base material and foaming gas as the dispersed phase. Biodegradability is a new requirement for polymer foam materials. The copolymer of butylene adipate and butylene terephthalate (PBAT) is a biodegradable random copolymer that not only has the excellent properties of foam materials, such as light weight, excellent thermal insulation, and significant sound insulation, but also has high flexibility and elasticity. It is expected to be widely used in yoga mats, shoe midsoles, insoles, elastic inner pads for flat mops, cushioning packaging, and other fields.

[0003] As the most effective way to solve white pollution, the application of biodegradable materials has attracted more and more attention. PBAT is a copolymer of polybutylene adipate / terephthalate, which combines the excellent degradation performance of aliphatic polyesters and the good mechanical properties of aromatic polyesters. At the same time, the molecular chain has good flexibility, making it a good substitute for polyethylene. Thanks to the benzene ring structure, PBAT has greater tear strength and impact strength than polyethylene, and its molecules have high thermal stability, low degradation rate, and large molecular space. It can be blended with other molecules and has good market application prospects.

[0004] In order to improve the foaming performance of PBAT, commonly used modification methods include blending, filling, cross-linking, chain extension, etc. For example, patent documents CN117186593A and CN113956628A disclose a method for preparing PBAT foaming materials by a kettle pressure method using a physical foaming agent. This method is an intermittent foaming process, the product production efficiency is low, the batch is unstable, and the surface of the particles is severely damaged when the foamed particles are steam bonded, which affects the product elasticity and yield rate and the energy consumption is too high. In addition, the PBAT foaming material prepared by the existing preparation method has insufficient resilience, and the soles formed by the same tend to turn yellow after a long period of use. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material, a foaming material prepared by the method, and an application of the foaming material in the field of sole molding in view of the deficiencies of the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material, characterized in that it comprises the following steps: S1. The polybutylene adipate terephthalate (PBAT) and the polyester aliphatic are fully dried in a vacuum drying oven to a water content of less than 0.5wt%; S2. Weigh polybutylene terephthalate adipate (PBAT), polyester aliphatic, and nucleating agent in a mass ratio of 70-90:10-30:1-5, and mix in a high-speed mixer for 3-5 minutes to obtain a mixture; S3. The mixture obtained in step S2 is added to the barrel of a screw extruder, and a polymer melt is obtained by melting reaction in the first three zones of the screw extruder. The screw portion of the screw extruder is heated in six temperature zones, the temperature of the first temperature zone is T1: 130°C-150°C, the temperature of the second temperature zone is T2: 150°C-170°C, the temperature of the third temperature zone is T3: 170°C-200°C, the temperature of the fourth temperature zone is T4: 170°C-200°C, the temperature of the fifth temperature zone is T5: 140°C-160°C, and the temperature of the sixth temperature zone is T6: 140°C-160°C, wherein T1<T2<T3, T3>T4>T5>T6; S4. Injecting supercritical carbon dioxide into the fourth temperature zone, wherein the injection amount of the supercritical carbon dioxide is 0.1-3wt% and the pressure is 10-30Mpa; the polymer solution in step S3 is mixed with supercritical carbon dioxide after passing through the fourth temperature zone to obtain a polymer / high-pressure carbon dioxide fluid melt; S5. The polymer / high-pressure carbon dioxide fluid melt in step S4 is mixed and cooled in the fifth temperature zone and the sixth temperature zone to obtain a cooled, uniformly mixed polymer / supercritical carbon dioxide melt; S6. The polymer / supercritical carbon dioxide melt in step S5 is extruded from the extruder die through a melt pump, and PBAT foamed beads are obtained by underwater ring cutting. The extruder die temperature is 100°C-120°C.

[0007] By adopting the above technical scheme, in S1, PBAT and polyester aliphatic are first pre-dried to remove moisture to ensure that the moisture content of the raw materials is less than 0.5wt%, so as to prevent the moisture from having adverse effects in the subsequent high-temperature processing, and to avoid the subsequent rapid vaporization of moisture at high temperature, resulting in bubbles, cracks or unevenness in the material, affecting the quality of the final product, and ensuring the reaction stability; in S2, PBAT, polyester aliphatic and nucleating agent are mixed to form a uniform mixture. Since the endothermic chemical foaming agent absorbs heat in the molten state, the local temperature of the polymer melt is reduced, which helps to control the thermal stability during the foaming process; the nucleating agent provides additional nucleation points, Promote the formation of uniform pores. The use of endothermic chemical foaming agents can improve foaming efficiency, reduce thermal decomposition, and improve the physical properties of the material. The use of nucleating agents helps to obtain a fine and evenly distributed pore structure, thereby improving the mechanical properties and stability of the material. In S3, the polymer melt is heated and melted in different temperature zones in the screw extruder to form a polymer melt. By gradually increasing the temperature, the polymer melt reaches the optimal flow state at different stages, while avoiding material decomposition caused by excessive temperature. The temperature of the fourth temperature zone is slightly lower than that of the third temperature zone in order to slightly reduce the melt temperature before injecting supercritical carbon dioxide to maintain the optimal foaming conditions and maintain The overall fluidity and thermal stability; in S4, supercritical carbon dioxide is injected into the fourth temperature zone and mixed with the polymer melt to obtain a polymer / high-pressure carbon dioxide fluid melt, wherein the supercritical carbon dioxide is injected to form uniformly distributed bubble nuclei in the polymer melt. Under appropriate temperature and pressure, supercritical carbon dioxide can be uniformly dissolved in the polymer melt to form uniform bubble nuclei, which is helpful to obtain high-quality foaming materials; in S5, the polymer / supercritical carbon dioxide melt is obtained by mixing and cooling the fifth temperature zone and the sixth temperature zone to control the thermal effect in the foaming process and avoid the degradation of material performance, while helping to maintain the carbon dioxide The dissolved state of carbon in the polymer controls the thermal stability during the foaming process, prevents the polymer melt from overheating, and ensures the solubility of carbon dioxide in the melt, laying the foundation for subsequent physical foaming; in S6, extrusion is to form the polymer / carbon dioxide melt into a specific shape and size, and the underwater ring cutting process can quickly and evenly cut the melt underwater to form beads. By extruding the polymer / carbon dioxide melt into a product of a specific shape and size, foam beads of consistent size can be continuously produced, with high production efficiency and good product consistency. At the same time, underwater ring cutting can reduce the oxidation and thermal degradation of the material to finally produce PBAT foam beads;Compared with the prior art, the entire process uses the physical properties of supercritical carbon dioxide as a foaming medium, and can achieve the foaming effect without an additional chemical foaming agent. The original foaming agent is then removed, avoiding the environmental problems and potential harm to the human body caused by traditional chemical foaming agents, while reducing the cost of raw materials. The extrusion method replaces the kettle pressure method. Since the extrusion method does not require a high-temperature and high-pressure kettle and a complex heating system, and supercritical carbon dioxide foaming utilizes physical state changes and does not require additional chemical reactions, the overall energy consumption is reduced, the production conditions can be more stably controlled, the consistency of materials is improved, the production efficiency is improved, continuous production is achieved, the production cost is reduced, and the performance differences between batches are reduced. It is also beneficial that supercritical carbon dioxide has special physical properties, such as low viscosity and high diffusivity, which can form a finer and more uniform pore structure in the PBAT melt, so that compared with nitrogen in the prior art, supercritical carbon dioxide improves foaming. The uniformity of the pores and the foaming ratio of the material, and the slow diffusion rate of carbon dioxide help to maintain the pore structure and avoid rapid rupture. About 20% of polyester aliphatic is added to the entire ratio. Polyester aliphatic such as PBS or PLA has excellent flexibility and biodegradability. After blending with PBAT, the flexibility and resilience of the overall material can be improved. At the same time, since its chemical structure does not contain benzene rings, it helps to improve the yellowing resistance of the material, improve the flexibility, resilience and yellowing resistance of the PBAT foaming material, and maintain the biodegradability of the material. Overall, through supercritical carbon dioxide foaming technology, high-pressure carbon dioxide is used to form a large number of micropores in the PBAT melt, and then the pressure is quickly released to expand the micropores to form a uniform foaming structure, and a high-resilience and yellowing-resistant PBAT supercritical foaming material is prepared. The prepared PBAT foaming material has good color stability during use, is not easy to yellow, and has high elasticity, and can provide good cushioning and recovery performance. ;

[0008] The above-mentioned method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material can be further configured as follows: the polyester aliphatic is at least one of polylactic acid (PLA), polyvinyl alcohol (PVA), and poly(ε-caprolactone) (PCL).

[0009] By adopting the above technical scheme, the properties of PBAT foaming materials, such as biodegradability, flexibility and resilience, can be adjusted by selecting different polyester aliphatics (PLA, PVA, PCL). For example, polylactic acid (PLA): PLA is an aliphatic polyester polymerized from lactic acid monomers, and is known for its good biodegradability and biocompatibility. It can be blended or copolymerized with PBAT to improve the resilience and yellowing resistance of PBAT. Polyvinyl alcohol (PVA): PVA is a water-soluble polyester with high flexibility and gas barrier properties, and can be used to improve the yellowing resistance and resilience of PBAT. Poly(ε-caprolactone) (PCL): PCL is valued for its flexibility and biodegradability, and can be used to improve the flexibility and resilience of PBAT.

[0010] The above-mentioned method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material can be further configured as follows: the nucleating agent in step S2 is at least one of phenyl zinc phosphate, TMC, talcum powder, silicon dioxide and calcium carbonate.

[0011] Using the above technical solution, phenyl zinc phosphate is usually used as a flame retardant and nucleating agent. As a nucleating agent, it helps to form additional nucleation points in the polymer matrix, increase the crystallization center, thereby improving the crystallinity of the polymer, increasing the rigidity and heat resistance of the material, and helping to improve the pore density and uniformity of the foamed material. TMC as a nucleating agent can increase the crystallization rate and crystallinity of the polymer. Improving the crystallinity helps to improve the strength and heat resistance of the material, and at the same time helps to form a finer and more uniform pore structure during the foaming process. Talc is a layered silicate mineral. As a nucleating agent, its lamellar structure can serve as a crystallization core to promote the orderly arrangement of polymer molecular chains and improve the polymerization. The crystallinity of the material, increase the uniformity of the pores, improve the rigidity and heat resistance of the material. As a nucleating agent, the tiny particles of silica can serve as crystallization cores to promote the crystallization of the polymer, improve the crystallinity and mechanical strength of the polymer, and improve the pore structure and stability of the foamed material. As a nucleating agent, calcium carbonate can provide additional nucleation points and increase the crystallization center of the polymer. Calcium carbonate helps to improve the crystallinity of the material, improve the pore uniformity of the foamed material, and improve its mechanical properties. The use of specific nucleating agents can improve the foaming efficiency, control the pore structure, and enhance the stability and uniformity of the material.

[0012] The above-mentioned method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material can be further configured as follows: the screw extruder in step S3 uses an extended screw with a mixing function having a length-to-diameter ratio of 40 to 60:1, a compression ratio of 3.0 to 4.0, and the first, second, third and fourth temperature zones are all air-cooled and temperature-controlled, and the fifth and sixth temperature zones are all heat-conducting oil-controlled.

[0013] With the above technical solution, the aspect ratio (L / D) of the screw extruder refers to the ratio of the effective working length of the screw to its diameter. The larger the aspect ratio, the higher the mixing and melting efficiency of the screw extruder. The extended screw provides more time and space to mix the raw materials, ensuring that PBAT, polyester aliphatic and nucleating agent are evenly mixed, reducing the inhomogeneity of the material, thereby improving the quality of the final product. The compression ratio refers to the volume change ratio of the polymer melt from the feeding zone to the melting zone in the screw extruder. Specifically, a compression ratio of 3.0 to 4.0 helps to increase the density and pressure of the melt, thereby improving the uniformity and plasticization effect of the melt. The reason why the first to fourth temperature zones use air cooling temperature control is that air cooling temperature control is a method of regulating temperature by air flow. In different temperature zones of the extruder, the temperature of the polymer melt is controlled by adjusting the air flow and temperature to ensure that it maintains a proper molten state during the extrusion process. The temperature of the polymer melt can be controlled more accurately through air cooling temperature control to avoid overheating or incomplete melting, which helps to maintain thermal stability during the extrusion process, reduce thermal degradation of the material, and improve the performance of the final product. The fifth and sixth temperature zones use thermal oil temperature control to control the temperature by utilizing the high heat capacity and uniform heat transfer characteristics of thermal oil. In the back section of the extruder, the temperature of the polymer melt is adjusted by circulating the thermal oil to ensure that it is properly cooled and solidified before extrusion molding, which helps to form a uniform polymer / carbon dioxide melt, helps to control the cooling rate of the polymer melt, and prevents internal stress and unevenness of the material caused by too fast cooling.

[0014] The above-mentioned method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material can be further configured as follows: in step S6, underwater ring cutting is performed to granulate at a pressure of 0.1-20 bar and a temperature of 0° C.-90° C.

[0015] The above technical solution is adopted, and the cutting technology is carried out underwater, and the melt is cut into beads by the rotating cutting blade in contact with the melt. Underwater cutting can reduce the friction heat in the cutting process and avoid thermal degradation of the material. The pressure of 0.1-20bar helps to maintain the stability of the cutting process and prevent the material from being deformed or broken due to excessive pressure. Cutting at a temperature of 0℃-90℃ can reduce the viscosity of the melt, making it easier to cut. Underwater ring cutting under precisely controlled pressure and temperature can ensure that the cut PBAT particles are uniform in size. The cooling effect of water can quickly reduce the surface temperature of the newly cut particles, reduce the adhesion between particles, and facilitate subsequent drying and processing, so as to produce high-quality PBAT foaming beads, providing an ideal raw material for the subsequent foaming process.

[0016] The above-mentioned method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material can be further configured as follows: in step S1, the melt index of polybutylene terephthalate adipate (PBAT) is 5-15 g / 10 min, the melting point is 110-130° C., and the carboxyl content is 10-30 mol / t.

[0017] By adopting the above technical scheme, a melt index of 5-15g / 10min means that PBAT is easier to flow during processing such as extrusion and injection molding, which helps to reduce processing temperature and pressure and improve production efficiency. Good melt fluidity helps to reduce unevenness in products, such as bubbles and voids, and improve the overall quality of products. The melting point of 110-130℃ refers to the temperature range in which the polymer changes from solid to liquid. Within the melting point range, PBAT can maintain thermal stability and avoid excessive thermal decomposition or degradation. The carboxyl content refers to the number of carboxyl functional groups in the PBAT molecular chain. The carboxyl group is a key functional group in the biodegradation process. A higher carboxyl content helps to improve the biodegradability of PBAT. Changes in the carboxyl content can affect the polarity, compatibility and miscibility of PBAT with other polymers, which helps to customize the performance of PBAT according to the needs of shoe factories to meet specific application requirements, improve the mechanical properties, thermal stability and durability of PBAT foaming materials, and make it perform better in various applications.

[0018] The above-mentioned method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material can be further configured as follows: in the step S1, the drying conditions are: temperature 50-80° C., and drying in a vacuum drying oven for 6-12 hours.

[0019] With the above technical solution, the temperature of 50-80°C provides sufficient heat energy to accelerate the evaporation of water, ensuring that the water content in PBAT drops to the low level required for processing, avoiding the breakage of PBAT molecular chains or changes in chemical structure due to excessively high temperature, and maintaining the original properties of the material. The drying time determines the degree to which water is completely removed from PBAT, ensuring that the water inside and on the surface of the PBAT particles is fully removed, preventing problems caused by the presence of water in subsequent processing.

[0020] Also disclosed is a PBAT foam material prepared by the above-mentioned method for preparing a high-resilience and yellowing-resistant PBAT supercritical foam material: the PBAT foam material comprises 70-90 parts by mass of polybutylene terephthalate adipate (PBAT), 10-30 parts by mass of polyvinyl alcohol (PVA), and 1-5 parts by mass of a nucleating agent.

[0021] With the above technical solution, PBAT is used as the main foaming material, providing the basic structure and mechanical properties of the foaming material. PBAT provides the necessary strength and toughness for the foaming material, which helps to reduce environmental pollution. PVA, as a water-soluble polymer, has good film-forming and adhesive properties. In the PBAT foaming material, PVA can improve the cohesion and adhesive properties of the material, while increasing the flexibility of the material. The addition of PVA makes the PBAT foaming material have better flexibility and resilience, improves the bonding strength between the particles of the foaming material, and helps to improve the stability of the final product. The nucleating agent helps The temperature in the foaming process is controlled while releasing gas to form pores. The nucleating agent provides a site for bubble nucleation, promotes the formation of a uniform pore structure, and improves the mechanical properties and appearance quality of the material. At the same time, since its chemical structure does not contain a benzene ring, it helps to improve the yellowing resistance of the material. By precisely controlling the ratio of PBAT, PVA and nucleating agent, the prepared PBAT foaming material has good comprehensive properties. The preparation method and formula design of this foaming material make the final product have the characteristics of high resilience, yellowing resistance, light weight and high strength, and is suitable for various application fields, such as shoe materials, cushioning materials, packaging materials, etc.

[0022] At the same time, the application of the above-mentioned PBAT foaming material as a shoe sole is disclosed: the high-resilience and yellowing-resistant PBAT supercritical foaming material is used to make a shoe sole.

[0023] By adopting the above technical solution, high-resilience and yellowing-resistant PBAT supercritical foaming material is applied to the sole, providing a new type of environmentally friendly sole material with excellent rebound performance and durability.

[0024] The application of the above-mentioned PBAT foam material as a shoe sole can be further set as follows: the rebound rate of the shoe sole is ≥50%, and the density is ≤0.10g / cm3.

[0025] By adopting the above technical scheme, by setting the rebound rate of the sole material to ≥50% and the density to ≤0.10g / cm³, a high-performance sole material can be achieved. It is not only lightweight and comfortable, but also has good elasticity and cushioning properties. This material can provide the wearer with excellent sports experience and long-term comfort while ensuring durability. In the preparation process, by precisely controlling the formula and processing technology of the PBAT foaming material, a sole material with a specific rebound rate and density can be obtained. The preparation method of the high-rebound and yellowing-resistant PBAT supercritical foaming material, by using supercritical carbon dioxide as a foaming agent, helps to obtain a uniform pore structure at a lower density, and further improves the rebound performance of the material. Compared with traditional chemical foaming agents, this foaming technology is more environmentally friendly and efficient, and helps to produce high-performance, lightweight, and highly elastic sole materials.

[0026] The beneficial effects of the present invention are: Environmental friendliness: By using biodegradable PBAT as the main material, pollution to the environment is reduced, which meets the current demand for sustainable development and environmentally friendly materials.

[0027] High resilience: Using supercritical carbon dioxide foaming technology, the obtained foam material has high resilience and is suitable for applications such as soles that require good cushioning performance.

[0028] Yellowing resistance: By optimizing the formula and process, the prepared PBAT foam material has good color stability during use and is not easy to yellow, which extends the service life of the product.

[0029] Low density: The foam material has low density, which makes the final product lightweight and improves wearing comfort.

[0030] Efficient production: The continuous extrusion foaming process is adopted to improve production efficiency, reduce energy consumption and production costs.

[0031] Stability: The stability and consistency of the product are ensured by precisely controlling the processing conditions and raw material ratios.

[0032] Low energy consumption: The extrusion method replaces the kettle pressing method, and no additional chemical reaction is required, so the overall energy consumption is reduced.

[0033] Low cost: The original foaming agent is removed and the bag foaming agent is made of supercritical carbon dioxide foaming technology, which avoids the environmental problems and potential harm to the human body caused by traditional chemical foaming agents, while reducing the cost of raw materials.

[0034] The present invention will be further described below in conjunction with the embodiments. Implementation

[0035] Example 1: Raw material preparation: Weigh 90 parts of PBAT, 15 parts of polyvinyl alcohol (PVA), and 5 parts of phenyl zinc phosphate as a nucleating agent.

[0036] Drying: PBAT and PVA were dried in a vacuum oven at 70 °C for 8 hours until the water content was less than 0.5 wt%.

[0037] Mixing: Mix in a high speed mixer for 3-5 minutes to obtain a homogeneous mixture.

[0038] Melting and foaming: Use a screw extruder and set six temperature zones: T1=140℃, T2=160℃, T3=200℃, T4=185℃, T5=160℃, T6=140℃.

[0039] Supercritical carbon dioxide is injected into the fourth temperature zone T4, with an injection amount of 1wt% and a pressure of 20Mpa.

[0040] Extrusion and cutting: After the polymer / carbon dioxide fluid melt is mixed and cooled in the fifth and sixth temperature zones, it is extruded through an extruder die and subjected to underwater ring cutting at a pressure of 15 bar and 25° C. to obtain PBAT foamed beads.

[0041] Molding: The foamed beads were molded into the shape of the sole at 120°C, maintaining a pressure of 15 bar for 240 seconds.

[0042] Post-treatment: After demoulding, the product was dried at 60°C for 4 hours to obtain a high-resilience and yellowing-resistant PBAT foamed sole.

[0043] Example 2: Raw material preparation: Weigh 80 parts of PBAT, 20 parts of polylactic acid (PLA), and 5 parts of silicon dioxide as a nucleating agent.

[0044] Drying: PBAT and PLA were dried in a vacuum oven at 60 °C for 10 h until the water content was less than 0.5 wt%.

[0045] Mixing: Mix in a high speed mixer for 3-5 minutes to obtain a homogeneous mixture.

[0046] Melting and foaming: Use a screw extruder and set six temperature zones: T1=150℃, T2=165℃, T3=190℃, T4=180℃, T5=155℃, T6=150℃.

[0047] Supercritical carbon dioxide is injected into the fourth temperature zone T4, with an injection amount of 2wt% and a pressure of 30Mpa.

[0048] Extrusion and cutting: After the polymer / carbon dioxide fluid melt is mixed and cooled in the fifth and sixth temperature zones, it is extruded through an extruder die and subjected to underwater ring cutting at a pressure of 6 bar and 75° C. to obtain PBAT foamed beads.

[0049] Molding: The foamed beads were molded into the shape of the sole at 180°C, maintaining a pressure of 6 bar for 300 seconds.

[0050] Post-treatment: After demoulding, the product was dried at 50°C for 2 hours to obtain a high-resilience and yellowing-resistant PBAT foamed sole.

[0051] Based on the content of the claims of this application, the following are two other specific embodiments: Example 3: Raw material preparation: Weigh 70 parts of PBAT, 30 parts of polyvinyl alcohol (PVA), and 3 parts of calcium carbonate as a nucleating agent.

[0052] Drying: PBAT and PVA were dried in a vacuum oven at 50 °C for 6 hours until the water content was less than 0.5 wt%.

[0053] Mixing: Mix in a high speed mixer for 3-5 minutes to obtain a homogeneous mixture.

[0054] Melting and foaming: Use a screw extruder and set six temperature zones: T1=130℃, T2=150℃, T3=180℃, T4=170℃, T5=150℃, T6=140℃.

[0055] Supercritical carbon dioxide is injected into the fourth temperature zone T4, with an injection amount of 0.1wt% and a pressure of 20Mpa.

[0056] Extrusion and cutting: After the polymer / carbon dioxide fluid melt is mixed and cooled in the fifth and sixth temperature zones, it is extruded through an extruder die and subjected to underwater ring cutting at a pressure of 20 bar and 90° C. to obtain PBAT foamed beads.

[0057] Molding: The foamed beads were molded into the shape of the sole at 160°C, maintaining a pressure of 20 bar for 180 seconds.

[0058] Post-treatment: After demoulding, the product was dried at 55°C for 3 hours to obtain a high-resilience and yellowing-resistant PBAT foamed sole.

[0059] Example 4: Raw material preparation: Weigh 85 parts of PBAT, 20 parts of poly(ε-caprolactone) (PCL), and 4 parts of TMC as a nucleating agent.

[0060] Drying: PBAT and PCL were dried in a vacuum oven at 80 °C for 12 h until the water content was less than 0.5 wt%.

[0061] Mixing: Mix in a high speed mixer for 3-5 minutes to obtain a homogeneous mixture.

[0062] Melting and foaming: Use a screw extruder and set six temperature zones: T1=145℃, T2=165℃, T3=200℃, T4=190℃, T5=160℃, T6=140℃.

[0063] Supercritical carbon dioxide is injected into the fourth temperature zone T4, with an injection amount of 3wt% and a pressure of 25Mpa.

[0064] Extrusion and cutting: After the polymer / carbon dioxide fluid melt is mixed and cooled in the fifth and sixth temperature zones, it is extruded through an extruder die and subjected to underwater ring cutting at a pressure of 0.5 bar and 0°C to obtain PBAT foamed beads.

[0065] Molding: The foamed beads were molded into the shape of the sole at 200°C, maintaining a pressure of 0.5 bar for 240 seconds.

[0066] Post-treatment: After demoulding, the product was dried at 45°C for 5 hours to obtain a high-resilience and yellowing-resistant PBAT foamed sole.

Claims

1. A method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material, characterized in that: The steps include: S1. The polybutylene adipate terephthalate (PBAT) and the polyester aliphatic are fully dried in a vacuum drying oven to a water content of less than 0.5wt%; S2. Weigh polybutylene terephthalate adipate (PBAT), polyester aliphatic, and nucleating agent in a mass ratio of 70-90:10-30:1-5, and mix in a high-speed mixer for 3-5 minutes to obtain a mixture; S3. The mixture obtained in step S2 is added to the barrel of a screw extruder, and a polymer melt is obtained by melting reaction in the first three zones of the screw extruder. The screw portion of the screw extruder is heated in six temperature zones, the temperature of the first temperature zone is T1: 130°C-150°C, the temperature of the second temperature zone is T2: 150°C-170°C, the temperature of the third temperature zone is T3: 170°C-200°C, the temperature of the fourth temperature zone is T4: 170°C-200°C, the temperature of the fifth temperature zone is T5: 140°C-160°C, and the temperature of the sixth temperature zone is T6: 140°C-160°C, wherein T1<T2<T3, T3>T4>T5>T6; S4. Injecting supercritical carbon dioxide into the fourth temperature zone, wherein the injection amount of the supercritical carbon dioxide is 0.1-3wt% and the pressure is 10-30Mpa; the polymer solution in step S3 is mixed with supercritical carbon dioxide after passing through the fourth temperature zone to obtain a polymer / high-pressure carbon dioxide fluid melt; S5. The polymer / high-pressure carbon dioxide fluid melt in step S4 is mixed and cooled in the fifth temperature zone and the sixth temperature zone to obtain a cooled, uniformly mixed polymer / supercritical carbon dioxide melt; S6. The polymer / supercritical carbon dioxide melt in step S5 is extruded from the extruder die through a melt pump, and PBAT foamed beads are obtained by underwater ring cutting. The extruder die temperature is 100°C-120°C.

2. The method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material according to claim 1, characterized in that: The polyester aliphatic is at least one of polylactic acid (PLA), polyvinyl alcohol (PVA), and poly(ε-caprolactone) (PCL).

3. The method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material according to claim 1, characterized in that: The nucleating agent in step S2 is at least one of phenyl zinc phosphate, TMC, talcum powder, silicon dioxide and calcium carbonate.

4. The method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material according to claim 1, characterized in that: The screw extruder in step S3 uses an extended screw with a mixing function and a length-to-diameter ratio of 40 to 60:1, a compression ratio of 3.0 to 4.0, the first, second, third and fourth temperature zones are all air-cooled, and the fifth and sixth temperature zones are all heat-conducting oil-controlled.

5. The method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material according to claim 4, characterized in that: In step S6, the underwater ring cutting is performed at a pressure of 0.1-20 bar and a temperature of 0° C.-90° C. to granulate.

6. The method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material according to claim 5, characterized in that: In the step S1, the polybutylene terephthalate adipate (PBAT) has a melt index of 5-15 g / 10 min, a melting point of 110-130° C., and a carboxyl content of 10-30 mol / t.

7. The method for preparing a high-resilience and yellowing-resistant PBAT supercritical foaming material according to claim 5, characterized in that: In the step S1, the drying conditions are: temperature 50-80° C., and drying in a vacuum drying oven for 6-12 hours.

8. A PBAT foam material prepared by the method for preparing a high-resilience and yellowing-resistant PBAT supercritical foam material according to any one of claims 1 to 7, characterized in that: The invention comprises, by weight, 70-90 parts of polybutylene terephthalate adipate (PBAT), 10-30 parts of polyvinyl alcohol (PVA), and 1-5 parts of a nucleating agent.

9. An application of the high-resilience and yellowing-resistant PBAT supercritical foaming material according to claim 8, characterized in that: The high-resilience and yellowing-resistant PBAT supercritical foaming material is used for making shoe materials.

10. The use of the high resilience and yellowing resistant PBAT supercritical foaming material according to claim 9, characterized in that: The rebound rate of the sole is ≥50%, and the density is ≤0.10g / cm3.