Preparation method of super-soft high-elastic TPU film

Abstract

The application provides a preparation method of super-soft high-elastic TPU film, and belongs to the technical field of the preparation of super-soft high-elastic TPU film. The preparation method comprises the following steps: adding TPU resin into a solvent and heating to completely dissolve the TPU; uniformly coating the TPU solution on the surface of a flat base; placing the coated TPU film under the irradiation of an infrared lamp to volatilize the solvent until the film layer is completely solidified; performing multi-stage heat pressing treatment on the film to improve the strength and toughness of the film; cooling the film after heat pressing, demolding the film from the base when the temperature drops to room temperature, and obtaining a formed super-soft high-elastic TPU film; and repeatedly annealing the formed super-soft high-elastic TPU film to further improve the performance of the film. The method can solve the problem that the thickness of the film is uneven in the traditional film preparation process, which not only affects the mechanical properties of the film, but also has a negative impact on the environmental safety of the final application.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of ultra-flexible and highly elastic TPU film, and more specifically, it relates to a method for preparing ultra-flexible and highly elastic TPU film. Background Technology

[0002] The background technology for preparing ultra-flexible, high-elastic TPU films involves the performance optimization of thermoplastic polyurethane (TPU) materials and the application of membrane materials in various industrial fields. TPU materials possess good elasticity, abrasion resistance, aging resistance, and chemical corrosion resistance, and are widely used in electronics, automotive, sports equipment, and medical materials. TPU can melt after heating and can be molded through injection molding or extrusion, exhibiting reprocessable characteristics. TPU has high elasticity, rapidly returning to its original shape after significant deformation. TPU films can resist external friction and UV erosion during long-term use. Ultra-flexible, high-elastic TPU films can be used as protective films for electronic devices, providing scratch resistance and shock absorption. Due to its good biocompatibility, TPU films can be used to manufacture films for medical devices, such as artificial joints and catheters. In footwear and sportswear, ultra-flexible, high-elastic TPU films are widely used to enhance comfort and elasticity. TPU films can be used in automotive seats, interior components, and other parts, providing excellent abrasion resistance and comfort.

[0003] In traditional membrane preparation processes, uneven membrane thickness not only affects the mechanical properties of the membrane but may also negatively impact the environmental safety of the final application. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing an ultra-flexible and highly elastic TPU film, which can solve the problem that the film thickness is uneven in the traditional film preparation process, which not only affects the mechanical properties of the film, but also has a negative impact on the environmental safety of the final application.

[0005] This invention is implemented as follows:

[0006] This invention provides a method for preparing an ultra-flexible, highly elastic TPU film, comprising the following specific steps:

[0007] S10: Add TPU resin to the solvent and heat it to completely dissolve the TPU;

[0008] S20: Apply the TPU solution evenly to a flat substrate surface;

[0009] S30: Place the coated TPU film under infrared light to evaporate the solvent until the film is completely cured;

[0010] S40: The membrane undergoes multi-stage hot pressing treatment to improve its strength and toughness;

[0011] S50: The film is cooled after hot pressing and then demolded from the substrate when the temperature drops to room temperature to obtain a shaped ultra-flexible and highly elastic TPU film.

[0012] S60: Repeated annealing treatment of the molded ultra-flexible high-elastic TPU film to further improve the film's performance.

[0013] Based on the above technical solution, the method for preparing an ultra-flexible and highly elastic TPU film of the present invention can be further improved as follows:

[0014] The specific steps involved in performing multi-stage hot-pressing treatment on the membrane to improve its strength and toughness include:

[0015] The first step is to heat the membrane to between 100°C and 120°C to partially relax the molecular chains inside the membrane, laying the foundation for subsequent hot pressing.

[0016] The second step is to place the membrane in a hot press and set the temperature between 160°C and 180°C. At this temperature, apply a pressure of 0.5 MPa to 1 MPa for 5-10 minutes to allow the molecular structure of the membrane to rearrange appropriately, thereby enhancing the density and uniformity of the membrane.

[0017] The third step is to remove the membrane from the first hot pressing process and quickly lower the temperature to prevent the membrane from softening or deforming excessively under hot pressing conditions. The membrane temperature should be reduced to below 50°C. The cooling time is 10-15 minutes to allow the membrane to cool completely and ensure the structural stability of the membrane in the cured state.

[0018] The fourth step involves a second hot pressing on the cooled membrane. The temperature is set between 160°C and 200°C, and the pressure of the hot press is increased to 1 MPa to 1.5 MPa for 5-10 minutes to further improve the mechanical properties and molecular structure arrangement of the membrane.

[0019] The fifth step is to keep the membrane at a high temperature for 1-2 minutes to ensure that the molecular structure of the membrane is fully cross-linked and to improve its toughness.

[0020] The sixth step is to cool the membrane again to ensure that its temperature drops rapidly to room temperature, giving it stable mechanical properties.

[0021] Step 7: Perform a third hot pressing, adjusting the temperature to 180°C to 200°C and increasing the pressure to 1.5 MPa to 2 MPa for 3-5 minutes to ensure the membrane achieves the desired final performance.

[0022] Furthermore, the size of the hot press plate is larger than that of the film, and it is divided into upper and lower layers with different materials. The heat conduction rate of the upper layer is lower than that of the lower layer to avoid uneven heat transfer.

[0023] The upper layer of the hot press plate includes a top plate, a bottom plate, and a flexible layer. The flexible layer is disposed between the top plate and the bottom plate and is used to balance the force on the flexible layer, so that the force received by the top plate and transmitted to the hot press plate through the pushing column is applied evenly on the plane of the hot press plate.

[0024] The thickness of the bottom plate is 1.5-2.5 times the thickness of the top plate.

[0025] Furthermore, the pressure pushing column at the top of the hot press plate includes multiple columns, both sides of which are configured as trumpet-shaped structures to balance the force, and the cross-sectional area at the center is smaller than the cross-sectional area on both sides; the multiple pushing columns on the hot press plate form a sinusoidal curve structure.

[0026] Furthermore, the specific steps for repeatedly annealing the molded ultra-flexible high-elastic TPU film to further improve the film's performance include:

[0027] The first step is to set the temperature between 140°C and 180°C, and heat the film evenly to the set temperature for 10 to 30 minutes. This allows the molecular chains of the TPU film to enter a more loose state, which helps improve the physical properties of the film, such as elasticity and durability. Ensure that the heating process is uniform and avoid excessive temperature differences that could cause stress concentration or localized melting of the film.

[0028] The second step is to slowly cool the heated membrane to room temperature;

[0029] The third step is to repeat the annealing cycle 2 to 3 times, with each annealing time being 10 minutes longer than the previous one, to ensure that the molecular chains are fully relaxed and rearranged during the heat treatment process.

[0030] The fourth step is to allow the membrane to cool fully at room temperature after annealing to ensure that there is no deformation or internal stress in the membrane.

[0031] Furthermore, the infrared curing mechanism for placing the coated TPU film under infrared lamp irradiation to evaporate the solvent includes a power supply, infrared lamps, and an infrared wavelength adjuster. The power supply is electrically connected to the infrared lamps and the infrared wavelength adjuster to provide power to them. Multiple infrared lamps are arranged laterally at uniform intervals and are respectively positioned on the top of the inner wall of the mounting housing to irradiate the surface of the coated TPU film with infrared light. The infrared wavelength adjuster is located on one side of the infrared lamps to adjust the wavelength of the infrared light emitted by the lamps.

[0032] The distance between the infrared lamp tube and the surface of the coated TPU film is 20~30cm.

[0033] Furthermore, the specific steps of uniformly coating the TPU solution onto the smooth substrate surface include:

[0034] The first step is to evenly coat the TPU solution onto the substrate surface, keeping the scraper at a 30-45 degree angle to the substrate surface to ensure that the coating thickness is uniform.

[0035] The second step is to start coating from one edge of the substrate and smoothly cover the entire surface, avoiding omissions and overlaps;

[0036] The third step is to place the coated substrate in a hot air circulating oven to accelerate the evaporation of the solvent.

[0037] Furthermore, TPU resin is added to the solvent and heated to completely dissolve the TPU. During this process, a magnetic stirrer is used to continuously circulate and stir the mixture to ensure uniformity.

[0038] Compared with existing technologies, the beneficial effects of the method for preparing an ultra-flexible and highly elastic TPU film provided by this invention are:

[0039] The TPU resin is added to a solvent and heated to ensure complete dissolution. In this process, the TPU resin is added to a suitable solvent, and heating promotes the dissolution process. Heating increases the volatility of the solvent, helping the TPU resin dissolve more easily into a homogeneous solution. A magnetic stirrer is typically used during this process to ensure the homogeneity of the solution and prevent resin sedimentation or incomplete dissolution. This step is fundamental to ensuring that the TPU resin can ultimately be coated and cured into a film.

[0040] The first step involves evenly coating the TPU solution onto a smooth substrate surface. Using a scraper or similar tool, maintain a 30-45 degree angle between the scraper and the substrate surface to ensure uniform film thickness during coating. The coating process must be kept smooth to avoid omissions or overlaps, ensuring film consistency. The coated film then enters the solvent evaporation stage.

[0041] The coated TPU film is placed under infrared light to evaporate the solvent until the film is completely cured. Infrared heating accelerates solvent evaporation. The wavelength of the infrared lamp can be adjusted to effectively accelerate surface solvent evaporation while avoiding overheating or uneven curing. This process solidifies the TPU film surface, resulting in a robust film layer.

[0042] Multi-stage hot pressing is designed to improve the mechanical properties of the membrane. Specific steps include:

[0043] First hot pressing: The membrane is heated to 100°C to 120°C to relax the molecular chains and lay the foundation for subsequent hot pressing; then hot pressing is carried out at 160°C to 180°C under a pressure of 0.5-1 MPa for 5-10 minutes to promote the rearrangement of the molecular structure and enhance the compactness of the membrane.

[0044] Cooling: After removing the membrane, quickly cool it to below 50°C to prevent the membrane from softening or deforming excessively under hot pressing conditions.

[0045] Second hot pressing: The membrane temperature is adjusted to 160°C to 200°C, the pressure is increased to 1-1.5 MPa, and it is continued for 5-10 minutes to further improve the mechanical properties of the membrane.

[0046] Third hot pressing: The membrane temperature is further increased to 180°C to 200°C, and the pressure is increased to 1.5-2 MPa to ensure that the membrane reaches its final performance.

[0047] After hot pressing, the film is cooled and demolded from the substrate when the temperature drops to room temperature, resulting in a shaped ultra-flexible, highly elastic TPU film. Cooling the hot-pressed film to room temperature ensures a stable structure after curing. After cooling, the film is demolded from the substrate to obtain the final shape of the ultra-flexible, highly elastic TPU film. The speed and uniformity of cooling are crucial to the final performance of the film.

[0048] Repeated annealing further improves the physical properties of the film through heat treatment. The specific steps are as follows:

[0049] First annealing: Heat to 140°C to 180°C and maintain for 10 to 30 minutes to loosen the molecular chains and improve the elasticity and durability of the film.

[0050] Cooling: Slowly cool to room temperature to avoid stress.

[0051] Repeated annealing: Perform 2 to 3 annealing cycles, each extending the annealing time by 10 minutes to ensure that the molecular chains are fully relaxed and rearranged.

[0052] The hot press plate uses different materials for its upper and lower layers to ensure uniform heat transfer. The upper layer has a lower thermal conductivity, which helps to apply pressure evenly and prevents the film from deforming during the hot pressing process.

[0053] Infrared curing uses multiple infrared lamps to evenly irradiate the coated TPU film. The addition of a wavelength modulator ensures that different wavelengths of infrared light can more effectively accelerate solvent evaporation.

[0054] Controlling the doctor blade angle and using a hot air oven during the coating process further ensures the uniformity and stability of the film. Attached Figure Description

[0055] Figure 1 This is a flowchart illustrating the preparation method of an ultra-flexible and highly elastic TPU film.

[0056] The attached diagram lists the components represented by each number as follows: Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0058] like Figure 1 The diagram shows a flowchart of a method for preparing an ultra-flexible, highly elastic TPU film according to the present invention. The specific steps included in the diagram are as follows:

[0059] S10: Add TPU resin to the solvent and heat it to completely dissolve the TPU;

[0060] S20: Apply the TPU solution evenly to a flat substrate surface;

[0061] S30: Place the coated TPU film under infrared light to evaporate the solvent until the film is completely cured;

[0062] S40: The membrane undergoes multi-stage hot pressing treatment to improve its strength and toughness;

[0063] S50: The film is cooled after hot pressing and then demolded from the substrate when the temperature drops to room temperature to obtain a shaped ultra-flexible and highly elastic TPU film.

[0064] S60: Repeated annealing treatment of the molded ultra-flexible high-elastic TPU film to further improve the film's performance.

[0065] In the above technical solution, the specific steps for performing multi-stage hot pressing treatment on the membrane to improve its strength and toughness include:

[0066] The first step is to heat the membrane to between 100°C and 120°C to partially relax the molecular chains inside the membrane, laying the foundation for subsequent hot pressing.

[0067] The second step is to place the membrane in a hot press and set the temperature between 160°C and 180°C. At this temperature, apply a pressure of 0.5 MPa to 1 MPa for 5-10 minutes to allow the molecular structure of the membrane to rearrange appropriately, thereby enhancing the density and uniformity of the membrane.

[0068] The third step is to remove the membrane from the first hot pressing process and quickly lower the temperature to prevent the membrane from softening or deforming excessively under hot pressing conditions. The membrane temperature should be reduced to below 50°C. The cooling time is 10-15 minutes to allow the membrane to cool completely and ensure the structural stability of the membrane in the cured state.

[0069] The fourth step involves a second hot pressing on the cooled membrane. The temperature is set between 160°C and 200°C, and the pressure of the hot press is increased to 1 MPa to 1.5 MPa for 5-10 minutes to further improve the mechanical properties and molecular structure arrangement of the membrane.

[0070] The fifth step is to keep the membrane at a high temperature for 1-2 minutes to ensure that the molecular structure of the membrane is fully cross-linked and to improve its toughness.

[0071] The sixth step is to cool the membrane again to ensure that its temperature drops rapidly to room temperature, giving it stable mechanical properties.

[0072] Step 7: Perform a third hot pressing, adjusting the temperature to 180°C to 200°C and increasing the pressure to 1.5 MPa to 2 MPa for 3-5 minutes to ensure the membrane achieves the desired final performance.

[0073] Furthermore, in the above technical solution, the size of the hot press plate is larger than the size of the film, and it is divided into upper and lower layers. The two layers are made of different materials, so that the heat conduction rate of the upper layer material is lower than that of the lower layer material, so as to avoid uneven heat transfer.

[0074] The upper layer of the hot press plate includes a top plate, a bottom plate, and a flexible layer. The flexible layer is placed between the top plate and the bottom plate to balance the force on the flexible layer, so that the force received by the top plate and transmitted to the hot press plate through the pushing column is applied evenly on the plane of the hot press plate.

[0075] The thickness of the base plate is 1.5-2.5 times that of the top plate.

[0076] Furthermore, in the above technical solution, the pressure pushing column at the top of the hot press plate includes multiple columns, both sides of which are set as trumpet-shaped structures to balance the force, and the cross-sectional area at the center is smaller than the cross-sectional area on both sides; the multiple pushing columns form a sinusoidal curve structure on the hot press plate.

[0077] Furthermore, in the above technical solution, the specific steps for repeatedly annealing the formed ultra-flexible high-elastic TPU film to further improve the film's performance include:

[0078] The first step is to set the temperature between 140°C and 180°C, and heat the film evenly to the set temperature for 10 to 30 minutes. This allows the molecular chains of the TPU film to enter a more loose state, which helps improve the physical properties of the film, such as elasticity and durability. Ensure that the heating process is uniform and avoid excessive temperature differences that could cause stress concentration or localized melting of the film.

[0079] The second step is to slowly cool the heated membrane to room temperature;

[0080] The third step is to repeat the annealing cycle 2 to 3 times, with each annealing time being 10 minutes longer than the previous one, to ensure that the molecular chains are fully relaxed and rearranged during the heat treatment process.

[0081] The fourth step is to allow the membrane to cool fully at room temperature after annealing to ensure that there is no deformation or internal stress in the membrane.

[0082] Furthermore, in the above technical solution, the infrared curing mechanism for placing the coated TPU film under infrared lamp irradiation to evaporate the solvent includes a power supply, infrared lamps, and an infrared wavelength adjuster. The power supply is electrically connected to the infrared lamps and the infrared wavelength adjuster to provide power to them. There are multiple infrared lamps, which are arranged horizontally at uniform intervals and are respectively set on the top of the inner wall of the rear fixing shell to irradiate the surface of the coated TPU film with infrared rays. The infrared wavelength adjuster is set on one side of the infrared lamps to adjust the wavelength of the infrared rays emitted by the infrared lamps.

[0083] The distance between the infrared lamp and the surface of the coated TPU film is 20~30cm.

[0084] Furthermore, in the above technical solution, the specific steps for uniformly coating the TPU solution onto a smooth substrate surface include:

[0085] The first step is to evenly coat the TPU solution onto the substrate surface, keeping the scraper at a 30-45 degree angle to the substrate surface to ensure that the coating thickness is uniform.

[0086] The second step is to start coating from one edge of the substrate and smoothly cover the entire surface, avoiding omissions and overlaps;

[0087] The third step is to place the coated substrate in a hot air circulating oven to accelerate the evaporation of the solvent.

[0088] Furthermore, in the above technical solution, TPU resin is added to the solvent and heated to completely dissolve the TPU. During this process, a magnetic stirrer is used to continuously circulate and stir the mixture to ensure uniformity of the stirring.

[0089] Example 1: Preparation and Hot-pressing of TPU Film

[0090] Materials preparation:

[0091] TPU resin: 100 grams

[0092] Solvent: Dichloromethane (50 ml)

[0093] Substrate: Aluminum alloy plate

[0094] Infrared light: 500W power, 850nm wavelength

[0095] Hot press: Temperature adjustable, maximum pressure 2 MPa

[0096] Operating steps:

[0097] TPU resin dissolution: Add 100g of TPU resin to 50ml of dichloromethane solvent, stir with a magnetic stirrer, heat to 70°C, and continue stirring for 30 minutes until the TPU is completely dissolved.

[0098] Coating: Use a scraper to evenly coat the dissolved TPU solution onto the surface of an aluminum alloy substrate measuring 10×10 cm. The angle between the scraper and the substrate should be maintained at 30 degrees to ensure uniform coating.

[0099] Solvent evaporation: Place the coated film under infrared lamp irradiation to evaporate the solvent. Set the infrared lamp power to 500W, keep it 15 cm away from the film surface, and irradiate continuously for 10 minutes until the film surface is completely cured.

[0100] Hot pressing: Multi-stage hot pressing is performed using a hot press. The temperature is set to 180°C, the pressure to 1 MPa, and the duration to 5 minutes. Then, the membrane is rapidly cooled to below 50°C.

[0101] Film cooling and demolding: The hot-pressed film is demolded from the substrate and cooled to room temperature to obtain an ultra-flexible and highly elastic TPU film with uniform thickness and smooth surface.

[0102] Data Records:

[0103] TPU resin melting time: 30 minutes

[0104] Coated film thickness: 0.1 mm

[0105] Infrared lamp irradiation time: 10 minutes

[0106] Hot pressing treatment temperature: 180°C, pressure: 1 MPa, time: 5 minutes

[0107] Final membrane strength test: tensile strength 25 MPa

[0108] Example 2: Performance Improvement of Improved TPU Film

[0109] Materials preparation:

[0110] TPU resin: 200 grams

[0111] Solvent: N,N-dimethylformamide (100 ml)

[0112] Substrate: Glass plate

[0113] Infrared light: 600W power, 950nm wavelength

[0114] Hot press: Maximum pressure 2.5 MPa, temperature control accuracy ±1°C

[0115] Operating steps:

[0116] TPU resin dissolution: Add 200g of TPU resin to 100ml of N,N-dimethylformamide solvent and stir with a magnetic stirrer at 80°C for 1 hour to ensure that the TPU is completely dissolved.

[0117] Coating: The solution is evenly coated onto the glass substrate using a precision doctor blade at a 35-degree angle to the substrate, and the coating thickness is controlled at 0.08 mm.

[0118] Solvent evaporation: Place the coated film under infrared lamp irradiation. Set the infrared lamp power to 600W, the irradiation time to 15 minutes, and keep the infrared lamp 20 cm away from the film surface.

[0119] Hot pressing treatment: The coated film is subjected to multi-stage hot pressing treatment. The first hot pressing temperature is 160°C and the pressure is 1.5MPa, lasting for 10 minutes; the second hot pressing temperature is 190°C and the pressure is 2MPa, lasting for 5 minutes.

[0120] Film Cooling and Demolding: After hot pressing, the film is rapidly cooled to below 50°C and then demolded from the glass substrate. The resulting TPU film has higher elasticity and durability.

[0121] Data Records:

[0122] TPU resin melting time: 1 hour

[0123] Coated film thickness: 0.08 mm

[0124] Infrared lamp irradiation time: 15 minutes

[0125] Hot pressing temperature: 160°C to 190°C, pressure: 1.5 MPa to 2 MPa, time: 10 minutes + 5 minutes

[0126] Final membrane tensile strength: 30 MPa

[0127] Example 3: Hot pressing and annealing treatment of high-performance TPU film

[0128] Materials preparation:

[0129] TPU resin: 150g

[0130] Solvent: Acetone (70 ml)

[0131] Base: Stainless steel plate

[0132] Infrared light: 400W power, 800nm ​​wavelength

[0133] Hot press: Maximum pressure 2 MPa, temperature control accuracy ±1°C

[0134] Operating steps:

[0135] TPU resin dissolution: Add 150g of TPU resin to 70ml of acetone, heat to 75°C using a magnetic stirrer, and stir for 45 minutes to ensure the TPU is completely dissolved.

[0136] Coating: Use a manual coating machine to evenly coat the solution onto the stainless steel substrate. The coating thickness is controlled at 0.12mm to ensure that the film is flat and free of bubbles.

[0137] Solvent evaporation: Place the coated film under infrared lamp irradiation to evaporate the solvent. The infrared lamp power is set to 400W and the irradiation time is 12 minutes to ensure that the film surface is completely cured.

[0138] Hot pressing treatment: Multi-stage hot pressing treatment is performed using a hot press. The first hot pressing temperature is 170°C, the pressure is 1.8MPa, and the duration is 6 minutes; the second hot pressing temperature is 200°C, the pressure is 2 MPa, and the duration is 4 minutes.

[0139] Annealing treatment: The hot-pressed membrane is annealed at 160°C for 30 minutes to ensure that the molecular chains of the membrane are fully relaxed and rearranged.

[0140] Film cooling and demolding: After annealing, the film is cooled to room temperature and demolded to obtain the final ultra-flexible and highly elastic TPU film with a smooth surface and excellent performance.

[0141] Data Records:

[0142] TPU resin melting time: 45 minutes

[0143] Coated film thickness: 0.12 mm

[0144] Infrared lamp irradiation time: 12 minutes

[0145] Hot pressing temperature: 170°C to 200°C, pressure: 1.8 MPa to 2 MPa, time: 6 minutes + 4 minutes

[0146] Annealing temperature: 160°C, time: 30 minutes

[0147] Final membrane tensile strength: 35 MPa

[0148] Specifically, the principle of this invention is as follows: TPU resin is added to a solvent and heated to completely dissolve the TPU; the TPU solution is uniformly coated onto a flat substrate surface; the coated TPU film is placed under infrared lamp irradiation to allow solvent evaporation until the film layer is completely cured; the film undergoes multi-stage hot pressing treatment to improve its strength and toughness; the film is cooled after hot pressing, and demolded from the substrate when the temperature drops to room temperature to obtain a molded ultra-flexible high-elastic TPU film; the molded ultra-flexible high-elastic TPU film undergoes repeated annealing treatment to further improve its performance.

[0149] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-flexible, highly elastic TPU film, characterized in that, The specific steps include: S10: Add TPU resin to the solvent and heat it to completely dissolve the TPU; S20: Apply the TPU solution evenly to a flat substrate surface; S30: Place the coated TPU film under infrared light to evaporate the solvent until the film is completely cured; S40: The membrane undergoes multi-stage hot pressing treatment to improve its strength and toughness; S50: The film is cooled after hot pressing and then demolded from the substrate when the temperature drops to room temperature to obtain a shaped ultra-flexible and highly elastic TPU film. S60: Repeated annealing treatment of the molded ultra-flexible and highly elastic TPU film to further improve the film's performance; The specific steps for performing multi-stage hot pressing on the membrane to improve its strength and toughness include: The first step is to heat the membrane to between 100°C and 120°C to partially relax the molecular chains inside the membrane, laying the foundation for subsequent hot pressing. The second step is to place the membrane in a hot press and set the temperature between 160°C and 180°C. At this temperature, apply a pressure of 0.5 MPa to 1 MPa for 5-10 minutes to allow the molecular structure of the membrane to rearrange appropriately, thereby enhancing the density and uniformity of the membrane. The third step is to remove the membrane from the first hot pressing process and quickly lower the temperature to prevent the membrane from softening or deforming excessively under hot pressing conditions. The membrane temperature should be reduced to below 50°C. The cooling time is 10-15 minutes to allow the membrane to cool completely and ensure the structural stability of the membrane in the cured state. The fourth step involves a second hot pressing on the cooled membrane. The temperature is set between 160°C and 200°C, and the pressure of the hot press is increased to 1 MPa to 1.5 MPa for 5-10 minutes to further improve the mechanical properties and molecular structure arrangement of the membrane. The fifth step is to keep the membrane at a high temperature for 1-2 minutes to ensure that the molecular structure of the membrane is fully cross-linked and to improve its toughness. The sixth step is to cool the membrane again to ensure that its temperature drops rapidly to room temperature, giving it stable mechanical properties. Step 7: Perform a third hot pressing, adjusting the temperature to 180°C to 200°C and increasing the pressure to 1.5 MPa to 2 MPa for 3-5 minutes to ensure the membrane achieves the desired final performance.

2. The method for preparing an ultra-flexible, highly elastic TPU film according to claim 1, characterized in that, The size of the hot press plate is larger than that of the film, and it is divided into two layers with different materials. The heat conduction rate of the upper material is lower than that of the lower material to avoid uneven heat transfer. The upper layer of the hot press plate includes a top plate, a bottom plate, and a flexible layer. The flexible layer is disposed between the top plate and the bottom plate and is used to balance the force on the flexible layer, so that the force received by the top plate and transmitted to the hot press plate through the pushing column is applied evenly on the plane of the hot press plate. The thickness of the bottom plate is 1.5-2.5 times the thickness of the top plate.

3. The method for preparing an ultra-flexible, highly elastic TPU film according to claim 2, characterized in that, The pressure pushing column at the top of the hot press plate includes multiple columns, both sides of which are set as trumpet-shaped structures to balance the force. The cross-sectional area at the center is smaller than the cross-sectional area on both sides. The multiple pushing columns on the hot press plate form a sinusoidal curve structure.

4. The method for preparing an ultra-flexible, highly elastic TPU film according to claim 3, characterized in that, The specific steps for repeatedly annealing the molded ultra-flexible high-elastic TPU film to further improve its performance include: The first step is to set the temperature between 140°C and 180°C, and heat the film evenly to the set temperature for 10 to 30 minutes. This allows the molecular chains of the TPU film to enter a more loose state, which helps improve the physical properties of the film, such as elasticity and durability. Ensure that the heating process is uniform and avoid excessive temperature differences that could cause stress concentration or localized melting of the film. The second step is to slowly cool the heated membrane to room temperature; The third step is to repeat the annealing cycle 2 to 3 times, with each annealing time being 10 minutes longer than the previous one, to ensure that the molecular chains are fully relaxed and rearranged during the heat treatment process. The fourth step is to allow the membrane to cool fully at room temperature after annealing to ensure that there is no deformation or internal stress in the membrane.

5. The method for preparing an ultra-flexible, highly elastic TPU film according to claim 4, characterized in that, The infrared curing mechanism for placing the coated TPU film under infrared lamp irradiation to evaporate the solvent includes a power supply, an infrared lamp tube, and an infrared wavelength adjuster. The power supply is electrically connected to the infrared lamp tube and the infrared wavelength adjuster to provide power to the infrared lamp tube and the infrared wavelength adjuster. The infrared lamps are multiple and are arranged horizontally at uniform intervals, respectively set on the top of the inner wall of the rear fixing shell, for irradiating the surface of the coated TPU film with infrared rays; the infrared wavelength adjuster is set on one side of the infrared lamps, for adjusting the wavelength of the infrared rays emitted by the infrared lamps. The distance between the infrared lamp tube and the surface of the coated TPU film is 20~30cm.

6. The method for preparing an ultra-flexible, highly elastic TPU film according to claim 5, characterized in that, The specific steps for uniformly coating the TPU solution onto a smooth substrate surface include: The first step is to evenly coat the TPU solution onto the substrate surface, keeping the scraper at a 30-45 degree angle to the substrate surface to ensure that the coating thickness is uniform. The second step is to start coating from one edge of the substrate and smoothly cover the entire surface, avoiding omissions and overlaps; The third step is to place the coated substrate in a hot air circulating oven to accelerate the evaporation of the solvent.

7. The method for preparing an ultra-flexible, highly elastic TPU film according to claim 6, characterized in that, TPU resin is added to a solvent and heated to completely dissolve the TPU. During this process, a magnetic stirrer is used to continuously circulate and stir the mixture to ensure uniformity.

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