Colored TPU (thermoplastic polyurethane) shading film and preparation method thereof

Abstract

The invention relates to a colored TPU (thermoplastic polyurethane) shading film and a preparation method thereof. The colored TPU shading film comprises the following components in parts by mass: 60-70 parts of a thermoplastic polyurethane elastomer, 25-35 parts of epoxy resin, 10-16 parts of a flexibilizer, 1-5 parts of a stabilizer and 4-6 parts of a slow-release antioxidant, the slow-release anti-ultraviolet agent is prepared from modified lignin, a bimetal framework and tannic acid. The anti-ultraviolet TPU shading film has the effect of improving the anti-ultraviolet performance of the TPU shading film.

Description

Technical Field

[0001] This application relates to the field of TPU films, and in particular to a colored TPU light-shielding film and its preparation method. Background Technology

[0002] TPU (thermoplastic polyurethane) is increasingly popular due to its superior performance and environmental friendliness. TPU not only possesses high tensile strength, high tear strength, toughness, and aging resistance, but it is also a mature and environmentally friendly material.

[0003] Light-blocking films can be used to block light, achieving partial or complete light transmission, thereby controlling light to meet specific light-blocking needs. The base material of light-blocking films can be polymer films such as polyolefin films, polyimide films, or polyurethane films. TPU, in particular, is a polymer compound with urethane as repeating units, formed by the reaction of polyols and polyisocyanates. It features adjustable hardness, solvent resistance, low-temperature resistance, and good adhesion to most materials, making it a high-performance polymer material widely used in tablecloths, shower curtains, curtains, furniture fabrics, coated fabrics, and lining materials.

[0004] Light often contains ultraviolet rays, but long-term exposure to ultraviolet radiation can easily cause aging, increasing the brittleness of the material. The surface layer loses its adhesive force due to molecular chain degradation, resulting in micro-cracks and affecting the stability of the light-shielding film. Summary of the Invention

[0005] To improve the UV protection performance of the light-shielding film, this application provides a colored TPU light-shielding film and its preparation method.

[0006] In the first aspect, this application provides a colored TPU light-shielding film, which adopts the following technical solution: A colored TPU light-blocking film comprises the following components in parts by weight: 60-70 parts thermoplastic polyurethane elastomer, 25-35 parts epoxy resin, 10-16 parts toughening agent, 1-5 parts stabilizer, and 4-6 parts slow-release antioxidant; The slow-release UV inhibitor comprises modified lignin, a bimetallic framework, and tannic acid.

[0007] By adopting the above technical solution, TPU films exposed to ultraviolet light for a long time will experience degradation, yellowing, and a decline in mechanical properties. Adding a slow-release UV stabilizer to the light-shielding film system can continuously absorb or reflect ultraviolet light, thereby reducing cracking and powdering on the film surface caused by ultraviolet radiation and effectively improving the film's UV resistance. The slow-release antioxidant is prepared by modifying lignin, a bimetallic framework, and tannic acid. Lignin contains abundant aromatic rings, phenolic hydroxyl groups, and conjugated double bonds, which have a strong absorption capacity for ultraviolet light. The phenolic hydroxyl groups in lignin have antioxidant properties. It can capture free radicals induced by ultraviolet light and further play an antioxidant role. As a novel biocompatible and environmentally friendly carrier material, the bimetallic framework can improve the loading effect of modified lignin and improve its stability. In addition, the bimetallic framework has the characteristics of large specific surface area and large porosity, which can enable the slow release of modified lignin and has excellent biological activity, making the slow-release anti-ultraviolet agent more stable in the system. At the same time, the bimetallic framework can be more uniformly dispersed in the system after being treated with tannic acid.

[0008] Preferably, the bimetallic framework is prepared by the following method: Zinc nitrate hexahydrate and a metal ion system were mixed and added to water to obtain a composite dispersion. 1-Hexyl-3-methylimidazolium chloride was mixed with water and sonicated to obtain an organic system. The organic system was mixed with the composite dispersion and stirred, then centrifuged. The resulting precipitate was washed and dried to obtain a bimetallic framework.

[0009] By adopting the above technical solution, a bimetallic framework system is obtained by combining the metal ion complex with Zn ions. This system has a multi-page cross structure, which improves the overall specific surface area and porosity of the bimetallic framework. This further improves the loading rate of the bimetallic framework on the modified lignin and enhances the stability of the slow-release UV stabilizer.

[0010] Preferably, the metal ion complex includes either nickel nitrate or copper chloride.

[0011] By adopting the above technical solution, Ni ions and Cu ions can form competitive coordination with Zn ions to change the overall coordination environment of the bimetallic skeleton, thereby creating embryonic or metal node defects in the leaf structure, which increases the active sites and unsaturation of the metal. This results in an increase in the overall specific surface area of ​​the prepared bimetallic skeleton, an increase in the loading rate of modified lignin, and further improves the stability of the slow-release UV stabilizer.

[0012] Preferably, the mass ratio of zinc nitrate to metal ions is 1:(1.6-1.7).

[0013] By adopting the above technical solution, and preferably within the above range the mass ratio between zinc nitrate and metal ions, the prepared bimetallic skeleton has a more stable leaf roughness, thereby increasing the overall specific surface area of ​​the system and further improving the loading rate of modified lignin.

[0014] Preferably, the modified lignin comprises lignin, 1-methylimidazole and octadecyltrichlorosilane as lignin raw materials.

[0015] Preferably, the modified lignin is prepared by the following method: After mixing lignin with water, a lignin dispersion was obtained. 1-Methylimidazole was added to the lignin dispersion and stirred. Then, octadecyltrichlorosilane and acetone were added. After heating and stirring, the mixture was washed, centrifuged, and dried to obtain modified lignin.

[0016] By employing the above technical solution, using 1-methylimidazole as the activator and octadecyltrichlorosilane as the hydrophobic agent to modify lignin into a superhydrophobic material, a modified lignin with superhydrophobic properties was prepared. This modified lignin exhibits good stability and dispersibility. The surface of the modified lignin particles is very rough, resembling scales, with a more layered appearance and increased spacing between particles, resulting in a more porous structure. This may be because the original lignin surface is rich in hydroxyl groups, which are replaced by chlorosilanes after modification. This breaks hydrogen bonds in the molecules, lengthens the molecular chains, and increases the distance between molecules, thus improving dispersibility.

[0017] Preferably, the mass ratio of lignin to octadecyltrichlorosilane is 1:(1.8-1.9).

[0018] By adopting the above technical solution, and preferably having the mass ratio of lignin to octadecyltrichlorosilane within the above range, the stability of the prepared modified wood can be further improved.

[0019] Preferably, the sustained-release antioxidant is prepared by the following method: Modified lignin, tannic acid, and a bimetallic framework were added to a solvent, the mixture was shaken and loaded on a shaker, and then centrifuged to dry the resulting precipitate, thus obtaining a slow-release antioxidant.

[0020] By adopting the above technical solution, the bimetallic framework is treated with tannic acid, which makes the bimetallic framework more stable and dispersed in the system, thereby further improving the overall stability of the sustained-release UV stabilizer.

[0021] Preferably, the mass ratio of the modified lignin, bimetallic skeleton and tannic acid is (6.2-6.8):1:0.15.

[0022] By adopting the above technical solution, and optimizing the mass ratio of modified lignin, bimetallic framework and tannic acid within the above range, the overall stability of the prepared sustained-release UV stabilizer can be further improved.

[0023] Secondly, this application provides a method for preparing a colored TPU light-shielding film, using the following technical solution: A method for preparing a colored TPU light-shielding film includes the following steps: Thermoplastic polyurethane elastomer, epoxy resin, color masterbatch, toughening agent, stabilizer and slow-release UV inhibitor are mixed and stirred to obtain a composite system. The composite system is extruded using a twin-screw extruder and cast into a film to obtain a colored TPU light-blocking film.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. The addition of a slow-release UV stabilizer to the light-shielding film system enables continuous absorption or reflection of ultraviolet (UV) radiation, thereby reducing surface cracking and powdering caused by UV exposure and effectively improving the UV resistance of the film. The slow-release antioxidant is prepared by modifying lignin, a bimetallic framework, and tannic acid. Lignin contains abundant aromatic rings, phenolic hydroxyl groups, and conjugated double bonds, which have a strong absorption capacity for UV radiation. The phenolic hydroxyl groups in lignin have antioxidant properties, capturing free radicals induced by UV radiation and further enhancing their antioxidant effect. The bimetallic framework, as a novel biocompatible and environmentally friendly carrier material, can improve the loading effect of modified lignin and enhance its stability. Furthermore, the bimetallic framework has a large specific surface area and high porosity, enabling the slow release of modified lignin and exhibiting excellent bioactivity, thus making the slow-release UV stabilizer more stable in the system. Additionally, the use of tannic acid to treat the bimetallic framework ensures more uniform dispersion within the system. 2. Both Ni and Cu ions can compete for coordination with Zn ions, thereby changing the overall coordination environment of the bimetallic framework. This results in embryonic or metal node defects in the leaf structure, which increases the active sites and unsaturation of the metal. Consequently, the specific surface area of ​​the prepared bimetallic framework is increased, the loading rate of modified lignin is improved, and the stability of the slow-release UV stabilizer is further enhanced. 3. Using 1-methylimidazole as the activator and octadecyltrichlorosilane as the hydrophobic agent, lignin was modified to exhibit superhydrophobic properties, resulting in modified lignin with good stability and dispersibility. The modified lignin particles had a very rough, scaly surface, with a more layered appearance and increased interparticle spacing, leading to a more porous particle structure. This may be because the original lignin surface is rich in hydroxyl groups, which are replaced by chlorosilanes after modification. This breaks hydrogen bonds in the molecules, lengthens the molecular chains, and increases the distance between molecules, thus improving dispersibility. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments: Raw material description: All raw materials in the examples are commercially available; among them, the toughening agent is styrene-butadiene-styrene block copolymer (CAS No.: 9003-55-8) and the stabilizer is dibutyltin dilaurate (CAS No.: 77-58-7).

[0026] Example 1 Preparation of modified lignin: 8.93 g of lignin (CAS No.: 8068-05-1) was mixed with deionized water, and 1.3 g of 1-methylimidazole (CAS No.: 616-47-7) was added. The mixture was stirred at 25 °C for 1 h to obtain a mixture. Then, 16.07 g of octadecyltrichlorosilane (CAS No.: 112-04-9) and 80 g of acetone were added to the mixture. The temperature was raised to 50 °C and stirred for 24 h. The mixture was then centrifuged for 10 min, washed with anhydrous ethanol, and finally dried in a hollow oven at 70 °C for 24 h to obtain modified lignin.

[0027] Preparation of bimetallic framework: 10g of zinc nitrate hexahydrate and 16g of the metal ion system were mixed and added to 200g of deionized water to obtain a composite dispersion. 30g of 1-hexyl-3-methylimidazolium chloride (CAS No.: 171058-17-6) was mixed with 200g of water and sonicated to obtain a solvent system. The solvent system was mixed with the composite dispersion and stirred at 400rpm for 4h at 25℃. Then, it was centrifuged at 9000rpm for 10min. The precipitate was washed three times alternately with deionized water and ethanol and then vacuum dried at 60℃ for 12h to obtain a bimetallic framework.

[0028] The metal ion system is nickel nitrate.

[0029] Preparation of sustained-release UV inhibitors: 12.65 g of modified lignin, 0.31 g of tannic acid (CAS No.: 1401-55-4) and 2.04 g of bimetallic framework were added to 100 g of acetone and shaken at 1000 rpm for 1.5 h on a shaker. Then, the mixture was centrifuged at 10000 rpm for 5 min. The resulting precipitate was vacuum dried at 40 °C for 12 h to obtain a sustained-release UV stabilizer.

[0030] Preparation of colored TPU light-blocking film: 60g of thermoplastic polyurethane elastomer, 25g of epoxy resin, 20g of color masterbatch, 10g of toughening agent, 1g of stabilizer, and 4g of slow-release UV inhibitor were mixed and stirred at 1000rpm to obtain a composite system. The composite system was then extruded using a twin-screw extruder with the following temperatures: Zone 1 temperature 160℃, Zone 2 temperature 180℃, Zone 3 temperature 190℃, and Die head temperature 185℃. After extrusion, the mixture was cast into a film with a thickness of 0.01mm to obtain a colored TPU light-blocking film.

[0031] Example 2 Preparation of modified lignin: 8.62 g of lignin was mixed with deionized water, and 1.3 g of 1-methylimidazole was added. The mixture was stirred at 25 °C for 1 h to obtain a solution. Then, 16.38 g of octadecyltrichlorosilane and 80 g of acetone were added to the solution. The mixture was heated to 50 °C and stirred for 24 h. The solution was then centrifuged for 10 min, washed with anhydrous ethanol, and finally dried in a hollow oven at 70 °C for 24 h to obtain modified lignin.

[0032] Preparation of bimetallic framework: 10g of zinc nitrate hexahydrate and 16g of the metal ion system were mixed and added to 200g of deionized water to obtain a composite dispersion. 30g of 1-hexyl-3-methylimidazolium chloride was mixed with 200g of water and sonicated to obtain a solvent system. The solvent system was mixed with the composite dispersion and stirred at 400rpm for 4h at 25℃. Then, it was centrifuged at 9000rpm for 10min. The resulting precipitate was washed three times alternately with deionized water and ethanol and then vacuum dried at 60℃ for 12h to obtain a bimetallic framework.

[0033] The metal ion system is nickel nitrate.

[0034] Preparation of sustained-release UV inhibitors: 12.83 g of modified lignin, 0.28 g of tannic acid and 1.89 g of bimetallic framework were added to 100 g of acetone and shaken at 1000 rpm for 1.5 h on a shaker. Then, the mixture was centrifuged at 10000 rpm for 5 min. The resulting precipitate was vacuum dried at 40 °C for 12 h to obtain a slow-release UV stabilizer.

[0035] Preparation of colored TPU light-blocking film: 70g of thermoplastic polyurethane elastomer, 35g of epoxy resin, 30g of color masterbatch, 16g of toughening agent, 5g of stabilizer, and 6g of slow-release UV inhibitor were mixed and stirred at 1000rpm to obtain a composite system. The composite system was then extruded using a twin-screw extruder with the following temperatures: Zone 1 temperature 160℃, Zone 2 temperature 180℃, Zone 3 temperature 190℃, and Die head temperature 185℃. After extrusion, the mixture was cast into a film with a thickness of 0.01mm to obtain a colored TPU light-blocking film.

[0036] Example 3 Preparation of modified lignin: 8.77 g of lignin was mixed with deionized water, and 1.3 g of 1-methylimidazole was added. The mixture was stirred at 25 °C for 1 h to obtain a solution. Then, 16.23 g of octadecyltrichlorosilane and 80 g of acetone were added to the solution. The mixture was heated to 50 °C and stirred for 24 h. The solution was then centrifuged for 10 min, washed with anhydrous ethanol, and finally dried in a hollow oven at 70 °C for 24 h to obtain modified lignin.

[0037] Preparation of bimetallic framework: 10g of zinc nitrate hexahydrate and 16g of the metal ion system were mixed and added to 200g of deionized water to obtain a composite dispersion. 30g of 1-hexyl-3-methylimidazolium chloride was mixed with 200g of water and sonicated to obtain a solvent system. The solvent system was mixed with the composite dispersion and stirred at 400rpm for 4h at 25℃. Then, it was centrifuged at 9000rpm for 10min. The resulting precipitate was washed three times alternately with deionized water and ethanol and then vacuum dried at 60℃ for 12h to obtain a bimetallic framework.

[0038] The metal ion system is nickel nitrate.

[0039] Preparation of sustained-release UV inhibitors: 12.75 g of modified lignin, 0.29 g of tannic acid and 1.96 g of bimetallic framework were added to 100 g of acetone and shaken at 1000 rpm for 1.5 h on a shaker. Then, the mixture was centrifuged at 10000 rpm for 5 min. The resulting precipitate was vacuum dried at 40 °C for 12 h to obtain a slow-release UV stabilizer.

[0040] Preparation of colored TPU light-blocking film: 65g of thermoplastic polyurethane elastomer, 30g of epoxy resin, 25g of color masterbatch, 13g of toughening agent, 3g of stabilizer, and 5g of slow-release UV inhibitor were mixed and stirred at 1000rpm to obtain a composite system. The composite system was then extruded using a twin-screw extruder with the following temperatures: Zone 1 temperature 160℃, Zone 2 temperature 180℃, Zone 3 temperature 190℃, and Die head temperature 185℃. After extrusion, the mixture was cast into a film with a thickness of 0.01mm to obtain a colored TPU light-blocking film.

[0041] Example 4 Example 4 is based on Example 3. In Example 4, 14g of copper chloride was added during the preparation of the bimetallic framework.

[0042] Example 5 Example 5 is based on Example 3. In Example 5, 20g of copper chloride was added when preparing the bimetallic framework.

[0043] Example 6 Example 6 is based on Example 3. In Example 6, the metal ion system used in the preparation of the bimetallic framework is ferrous sulfate.

[0044] Example 7 Example 7 is based on Example 3. In Example 7, the metal ion system used in the preparation of the bimetallic framework is cobalt nitrate.

[0045] Example 8 Example 8 is based on Example 3. In Example 8, when preparing the slow-release UV inhibitor, the modified lignin added is 12.52g, the bimetallic skeleton is 2.16g, and the tannic acid is 0.32g.

[0046] Example 9 Example 9 is based on Example 3. In Example 9, when preparing the slow-release UV inhibitor, the modified lignin added is 12.93g, the bimetallic skeleton is 1.8g, and the tannic acid is 0.27g.

[0047] Example 10 Example 10 is based on Example 3. In Example 10, the vibration load time is 1 hour when preparing the sustained-release UV inhibitor.

[0048] Example 11 Example 11 is based on Example 3. In Example 11, the vibration load time is 3 hours when preparing the sustained-release UV inhibitor.

[0049] Example 12 Example 12 is based on Example 3, but no tannic acid was added when preparing the sustained-release UV protectant in Example 12.

[0050] Example 13 Example 13 is based on Example 3. In Example 13, when preparing modified lignin, the amount of lignin used is 9.62g and the amount of octadecyltrichlorosilane used is 15.38g.

[0051] Example 14 Example 14 is based on Example 3. In Example 14, when preparing modified lignin, the amount of lignin used is 8.06g and the amount of octadecyltrichlorosilane used is 16.94g.

[0052] Example 15 Example 15 is based on Example 3, except that 1-methylimidazole was not added during the preparation of the modified lignin in Example 15.

[0053] Example 16 Example 16 is based on Example 3. In Example 16, when preparing the slow-release UV-resistant reagent, the modified lignin is replaced with an equal amount of ordinary unmodified lignin.

[0054] Comparative Example 1 Comparative Example 1 is based on Example 3. In Comparative Example 1, when preparing the sustained-release UV inhibitor, the bimetallic framework was replaced with a metal framework containing only one metal ion. The metal framework was prepared by the following method: 10g of zinc nitrate hexahydrate was added to 200g of deionized water to obtain a dispersion. 30g of 1-hexyl-3-methylimidazolium chloride was mixed with 200g of water and added to the dispersion. The mixture was stirred at 400rpm for 4h at 25℃, then centrifuged at 9000rpm for 10min. The precipitate was washed three times alternately with deionized water and ethanol, and then vacuum dried at 60℃ for 12h to obtain the metal framework.

[0055] Comparative Example 2 Comparative Example 2 is based on Example 3, except that the slow-release UV stabilizer is replaced with an equal amount of modified lignin.

[0056] Performance testing The following performance tests were performed on the samples of Examples 1-16 and Comparative Examples 1-2: (1) Mechanical strength test Using GB / T13022-1991 as the testing reference, a UTM-2360 universal testing machine was used to conduct tensile tests on the specimens at a tensile rate controlled at 50 mm / min. (2) Ultraviolet aging test Using GB / T 14522-2008 as the testing reference, accelerated aging was performed using a ZWLH-5 type ultraviolet aging chamber. The distance between the sample and the ultraviolet lamp was 25cm, the irradiation power was 500W, the ultraviolet wavelength was 280-400nm, the light intensity was 30±5×102μW / cm2, the ambient temperature was 53±3℃, and the test cycle was 168h. Tensile properties were then tested on the aged samples, and the specific test results are shown in Table 1. Table 1 Performance test results of Examples 1-16 and Comparative Examples 1-2 Testing items Tensile strength / MPa Tensile strength after UV aging / MPa Example 1 61.1 59.9 Example 2 61.3 59.5 Example 3 61.6 60.4 Example 4 58.6 56.2 Example 5 58.8 56.3 Example 6 57.4 55.5 Example 7 57.5 55.6 Example 8 58.3 56.0 Example 9 58.0 56.9 Example 10 60.0 57.6 Example 11 60.2 57.8 Example 12 59.1 55.5 Example 13 60.4 56.1 Example 14 60.6 56.6 Example 15 60.3 56.2 Example 16 60.6 51.4 Comparative Example 1 55.2 51.0 Comparative Example 2 50.1 46.2 As shown in Table 1, the tensile strength of Examples 1-3 is above 61 MPa, indicating that the TPU light-shielding film prepared in this application has good tensile properties. The tensile strength of Examples 1-3 after UV aging is 59.5 MPa and above, indicating that the TPU light-shielding film prepared in this application has good UV resistance.

[0057] In Examples 4 and 5, the mass ratio between zinc nitrate and copper chloride during the preparation of the bimetallic framework was not within the range specified in this application. When the content of copper chloride was too low or too high, it was difficult to form a stable bimetallic framework. The particle size uniformity of the bimetallic framework decreased, and the specific surface area improvement effect was not obvious. It was also difficult to further improve the loading rate of modified lignin, which affected the overall stability of the system. Therefore, the performance of Examples 4 and 5 was reduced.

[0058] In Example 6, the metal ion system was ferrous sulfate, and in Example 7, the metal ion system was cobalt nitrate. It was difficult for iron ions and cobalt ions to further enhance the synergistic effect between zinc ions, thus making it difficult to improve the loading efficiency of the prepared bimetallic framework on modified lignin, thereby affecting the overall sustained-release effect of the system. It was also difficult to improve the mechanical strength and UV resistance of the system. Therefore, the performance of both Example 6 and Example 7 decreased.

[0059] In Examples 8 and 9, the mass ratios of modified lignin, bimetallic framework, and tannic acid during the preparation of the sustained-release UV stabilizer were not within the range specified in this application. When the amount of modified lignin added was too small, the effective UV stabilizer content decreased, and the pores of the bimetallic framework were not fully loaded, resulting in a decrease in the loading rate of modified lignin and affecting the overall UV stabilizer performance of the system. Therefore, the performance of Example 8 decreased. When the amount of modified lignin added was too large, it exceeded the loading capacity of the bimetallic framework. Excessive modified lignin had reduced dispersion performance in the system and agglomerated in the system, affecting the release performance of modified lignin and decreasing the stability of the system. Therefore, the performance of Example 9 decreased.

[0060] In Examples 10 and 11, the vibration loading times were 1 hour and 3 hours, respectively. When the vibration loading time was too short, it was difficult for the modified lignin to further fill the pores in the bimetallic framework, thus making it difficult to further improve the loading rate of the modified lignin in the bimetallic framework and reducing stability. When the vibration loading time was too long, the modified lignin already loaded in the pores would fall off, thus reducing the loading rate and the stability of the prepared system. Therefore, the performance of Examples 10 and 11 both decreased.

[0061] In Example 12, no tannic acid was added during the preparation of the sustained-release UV stabilizer, and the bimetallic framework system was not dispersed. This caused the bimetallic framework system loaded with modified lignin to aggregate in the system, thereby affecting the subsequent release stability of the modified lignin and the overall performance of the system. Therefore, the performance of Example 14 was reduced.

[0062] In Examples 13 and 14, the mass ratio of lignin to octadecyltrichlorosilane during the preparation of modified lignin was not within the range specified in this application. When the content of octadecyltrichlorosilane was too low, it was difficult to further improve the modification of lignin, the dispersibility of lignin in the system decreased, and agglomeration occurred, affecting the stability when loaded onto the metal skeleton, thereby affecting the subsequent sustained-release performance. When the content of octadecyltrichlorosilane was too high, the particle size of lignin became too large, and the stability in the system decreased, thereby affecting the overall stability of the prepared sustained-release antioxidant. Therefore, the performance of Examples 13 and 14 was reduced.

[0063] In Example 15, 1-methylimidazole was not added during the preparation of modified lignin, which resulted in a decrease in the grafting rate. Consequently, the modification effect of lignin decreased, affecting the stability of the lignin in the subsequent process. Therefore, the performance of Example 15 was reduced.

[0064] In Example 16, when preparing the slow-release UV stabilizer, the modified lignin was replaced with unmodified lignin. The unmodified lignin agglomerated in the system, affecting the overall stability of the prepared TPU film. Therefore, the UV resistance and mechanical strength of Example 16 were reduced.

[0065] In Comparative Example 1, the bimetallic framework was replaced with a metal framework containing only one metal ion. The specific surface area of ​​the metal framework system prepared by the single metal ion was difficult to be further improved, and the porosity of the metal framework was difficult to be further increased. The loading rate of modified lignin was difficult to be further improved, and the stability was also reduced.

[0066] In Comparative Example 2, the slow-release UV stabilizer was replaced with an equal amount of modified lignin. Without the slow-release lignin, it was difficult to achieve long-lasting UV protection. Furthermore, the TPU film without a bimetallic skeleton was difficult to further improve mechanical strength and stability. Therefore, the performance of Comparative Example 2 was reduced.

[0067] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A colored TPU light-blocking film, characterized in that: The components include the following parts by mass: 60-70 parts thermoplastic polyurethane elastomer, 25-35 parts epoxy resin, 10-16 parts toughening agent, 1-5 parts stabilizer, and 4-6 parts slow-release antioxidant; The slow-release UV inhibitor comprises modified lignin, a bimetallic framework, and tannic acid.

2. The colored TPU light-shielding film according to claim 1, characterized in that: The bimetallic framework was prepared using the following method: Zinc nitrate hexahydrate and a metal ion system were mixed and added to water to obtain a composite dispersion. 1-Hexyl-3-methylimidazolium chloride was mixed with water and sonicated to obtain an organic system. The organic system was mixed with the composite dispersion and stirred, then centrifuged. The resulting precipitate was washed and dried to obtain a bimetallic framework.

3. The colored TPU light-shielding film according to claim 1, characterized in that: The metal ion complex includes either nickel nitrate or copper chloride.

4. The colored TPU light-shielding film according to claim 1, characterized in that: The mass ratio of zinc nitrate to metal ions is 1:(1.6-1.7).

5. A colored TPU light-shielding film according to claim 1, characterized in that: The modified lignin includes modified lignin raw materials including lignin, 1-methylimidazolium and octadecyltrichlorosilane.

6. A colored TPU light-shielding film according to claim 5, characterized in that: The modified lignin was prepared by the following method: After mixing lignin with water, a lignin dispersion was obtained. 1-Methylimidazole was added to the lignin dispersion and stirred. Then, octadecyltrichlorosilane and acetone were added. After heating and stirring, the mixture was washed, centrifuged, and dried to obtain modified lignin.

7. A colored TPU light-shielding film according to claim 6, characterized in that: The mass ratio of lignin to octadecyltrichlorosilane is 1:(1.8-1.9).

8. A colored TPU light-shielding film according to claim 1, characterized in that: The sustained-release antioxidant is prepared by the following method: Modified lignin, tannic acid, and a bimetallic framework were added to a solvent, the mixture was shaken and loaded on a shaker, and then centrifuged to dry the resulting precipitate, thus obtaining a slow-release antioxidant.

9. A colored TPU light-shielding film according to claim 1, characterized in that: The mass ratio of the modified lignin, bimetallic skeleton and tannic acid is (6.2-6.8):1:0.

15.

10. A colored TPU light-shielding film applied to any one of claims 1-9, characterized in that: Includes the following steps: Thermoplastic polyurethane elastomer, epoxy resin, color masterbatch, toughening agent, stabilizer and slow-release UV inhibitor are mixed and stirred to obtain a composite system. The composite system is extruded using a twin-screw extruder and cast into a film to obtain a colored TPU light-blocking film.