Ultraviolet-resistant TPU film and preparation method thereof

Abstract

The invention relates to the technical field of TPU film preparation, in particular to an ultraviolet-resistant TPU film and a preparation method thereof. The preparation method comprises the following steps: S1, preparation of a prepolymer: adding polytetramethylene ether glycol and polypropylene glycol into a reaction kettle, carrying out vacuum dehydration at 95-105 DEG C, cooling to 55-65 DEG C, adding aliphatic isocyanate, uniformly stirring, dropwise adding a catalyst, heating to 75-80 DEG C under the protection of nitrogen, reacting for 2-4 hours, cooling to 38-45 DEG C, adding a solvent, and reacting for 2-4 hours to obtain the prepolymer; stirring and dispersing to obtain a polyether polyurethane prepolymer; s2, composite modification; and S3, preparing the ultraviolet-resistant TPU film. According to the ultraviolet-resistant TPU film and the preparation method thereof provided by the invention, the problems that the TPU film is easy to yellow and poor in mechanical property under ultraviolet irradiation in the prior art are solved.

Description

Technical Field

[0001] This application relates to the field of TPU film preparation technology, and in particular to a UV-resistant TPU film and its preparation method. Background Technology

[0002] Thermoplastic polyurethane elastomer, also known as thermoplastic polyurethane rubber or TPU for short, is a type of elastomer that can be plasticized by heating and dissolved by solvents. It has excellent comprehensive properties such as high strength, high toughness, wear resistance, and oil resistance, and good processing performance. It is widely used in footwear, cables, clothing, automobiles, films and other fields. Among them, polyether-based TPU films, which are mainly composed of polyurethane / polyether, have become one of the preferred materials for outdoor applications due to the good low-temperature resistance and hydrolytic stability brought by the polyether soft segments.

[0003] In related technologies, to improve the UV resistance of polyether-type TPU films, aliphatic isocyanates are usually chosen to replace aromatic isocyanates to reduce the UV-sensitive benzene ring structure in the molecular chain, thereby reducing the risk of yellowing and degradation from the source. Alternatively, UV absorbers or inorganic shielding particles (nano ZnO, TiO2, etc.) can be blended with TPU substrates to construct chemical absorption or physical shielding systems.

[0004] However, traditional organic UV absorbers have limited compatibility with TPU substrates and are prone to migration, volatilization, or photodegradation failure during long-term use, resulting in yellowing of the film material under UV irradiation. Secondly, the CO bonds in the polyether soft segments are easily attacked and broken by free radicals induced by UV, leading to a significant decline in mechanical properties and making it difficult to maintain good overall performance. Summary of the Invention

[0005] This application provides a UV-resistant TPU film and its preparation method to solve the problem that TPU films in related technologies are prone to yellowing and have poor mechanical properties under UV irradiation.

[0006] In a first aspect, a method for preparing a UV-resistant TPU film is provided, comprising the following steps: S1. Prepolymer preparation: According to the mass fractions, 55-65 parts of polytetramethylene ether glycol and 15-25 parts of polypropylene glycol are added to a reactor. After vacuum dehydration at 95-105°C for 2-3 hours, the temperature is lowered to 55-65°C, 20-30 parts of aliphatic isocyanate are added, and after stirring evenly, 0.1-0.2 parts of catalyst are added dropwise. Under nitrogen protection, the temperature is raised to 75-80°C and reacted for 2-4 hours. After cooling to 38-45°C, 28-32 parts of solvent are added, and after stirring and dispersing, a polyether-type polyurethane prepolymer is obtained. S2, Composite Modification: Add 1-2 parts of UV-absorbing functional monomer and 12-15 parts of modifier to the polyether-type polyurethane prepolymer, stir at high speed for 10-15 min, add 2-3 parts of dispersant, continue stirring for 1-1.5 h, ultrasonically disperse for 30-40 min, add 7-8 parts of chain extender, heat to 50-60℃, add 18-22 parts of solvent and 1-1.5 parts of antioxidant, stir for 20-30 min, and degas under nitrogen protection for 20-30 min to obtain the modified polyurethane resin system; S3. Preparation of UV-resistant TPU film: The modified polyurethane resin system was coated onto a PET release film, dried at 50-60°C for 3-4 hours, then heated to 100-110°C and hot-pressed for 1-2 hours. After cooling to room temperature, the PET release film was peeled off and cured for 10-12 hours to obtain a UV-resistant TPU film. The preparation method of the modifier includes the following steps: Cyclodextrin was dissolved in deionized water at a mass ratio of 1:8~9, stirred at 55~60℃ until transparent, then a UV-absorbing functional monomer was added, stirred at a constant temperature for 1~2 hours, filtered and dried to obtain the inclusion complex. The mass ratio of the UV-absorbing functional monomer to cyclodextrin was 1:4~5. Hydrotalcite was dispersed in 95wt% ethanol solution at a mass ratio of 1:4~5. After ultrasonic dispersion for 20~30 min, nano-zirconium carbide and inclusion complex were added, and ultrasonication was continued for 45~60 min. After heating to 65~70℃, the mixture was stirred for 2~3 h, centrifuged, and dried to obtain the modifier. The amount of nano-zirconium carbide added is 35-40% of the mass of hydrotalcite, and the amount of inclusion complex added is 20-25% of the mass of hydrotalcite.

[0007] Preferably, in S1, the aliphatic isocyanate is selected from one of hexamethylene diisocyanate and isophorone diisocyanate; The catalyst is selected from one of dibutyltin dilaurate and triethylenediamine.

[0008] Preferably, in S2, the antioxidant is selected from sorbic acid; The chain extender is selected from aliphatic chain extenders, and the aliphatic chain extender is selected from one of 1,4-butanediol and ethylene glycol.

[0009] Preferably, in S2, the dispersant is selected from at least one of povidone and carboxyethyl cellulose.

[0010] Preferably, the dispersant comprises polyvinyl ketone and carboxyethyl cellulose in a mass ratio of 3:2.

[0011] Preferably, in S1 and S2, the solvent is selected from either ethyl acetate or acetone.

[0012] Preferably, the method for preparing the modifier further includes the following steps after adding nano-zirconium carbide and the inclusion complex and continuing sonication: Add low molecular weight polypyrrole and ultrasonically disperse for 15-20 minutes; The amount of low molecular weight polypyrrole added is 1 to 3% of the mass of hydrotalcite.

[0013] Preferably, the ultraviolet absorption functional monomer is selected from isoeugenol or 2-hydroxy-4-methoxybenzophenone.

[0014] Preferably, in step S3, the coating thickness is 50~100μm; the coating is performed using a doctor blade coater at a speed of 2~3m / min.

[0015] Secondly, a UV-resistant TPU film is provided, which is prepared by any of the UV-resistant TPU film preparation methods described above.

[0016] The beneficial effects of the technical solution provided in this application include: This application provides a UV-resistant TPU film and its preparation method. Using aliphatic isocyanate and polyether diol as the substrate, it avoids the use of aromatic benzene rings, a UV-sensitive group, thus reducing the risk of yellowing and degradation at the source. Cyclodextrin in the modifier encapsulates the UV-absorbing functional monomer through cavities, forming a stable inclusion complex structure. This improves the compatibility between the UV-absorbing functional monomer and the substrate, effectively preventing its migration, volatilization, or photo-oxidation failure, ensuring long-lasting UV absorption. The layered structure of hydrotalcite and nano-zirconium carbide act as physical shielding materials, reducing the penetration depth of UV light through reflection and scattering, decreasing the excitation probability of CO bonds in the polyether soft segment. Simultaneously, the basic sites of hydrotalcite can capture acidic free radicals generated during degradation, improving the UV blocking rate of the TPU film and mitigating the yellowing problem of traditional TPU films after UV aging.

[0017] On the other hand, this application improves the mechanical properties of TPU film by regulating the crosslinking density of hard segments through chain extenders. Nano-zirconium carbide and hydrotalcite in the modifier also play a role in improving the tensile strength of TPU film. The presence of inclusion complexes further optimizes the interfacial compatibility between dispersants and other additives and the substrate, reduces the obstruction of molecular chain movement by rigid particles, and enables TPU film to maintain high tensile strength and high elongation at break. The dispersant also effectively improves the fluidity and dispersibility of the resin system, resulting in good film-forming properties. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating the preparation method of the UV-resistant TPU film provided in this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] See Figure 1 As shown, this application provides a UV-resistant TPU film and its preparation method.

[0022] Furthermore, the following examples and comparative examples use polytetramethylene ether glycol with a purity ≥99.0%; polypropylene glycol with a purity ≥99.0%; hexamethylene diisocyanate with a purity ≥99.5%; isophorone diisocyanate with a purity ≥99.0%; 1,4-butanediol with a purity ≥99.8%; ethylene glycol with a purity ≥99.8%; β-cyclodextrin with a purity ≥98.0%; low molecular weight polypyrrole with an average molecular weight of 10000 Da and a purity ≥95.0%; nano-zirconium carbide with a particle size of 20~50 nm and a purity ≥99.0%; hydroxyethyl cellulose with a molecular weight of 150000 Da and a purity ≥99.0%; and povidone with a molecular weight of 40000 Da and a purity ≥99.0%.

[0023] Example 1 The method for preparing the UV-resistant TPU film provided in this embodiment is as follows: S101, Prepolymer Preparation: 240g of polytetramethylene ether glycol PTMEG-2000 and 80g of polypropylene glycol PPG-1000 were added to a reactor. After dehydration at 100℃ and -0.09MPa for 2 hours, the temperature was lowered to 60℃, 100g of hexamethylene diisocyanate was added, and after stirring evenly, 0.6g of dibutyltin dilaurate was added dropwise. The temperature was raised to 75℃ under nitrogen protection and reacted for 3 hours. After cooling to 40℃, 120g of acetone was added and stirred to disperse the mixture to obtain a polyether-type polyurethane prepolymer. S102, Composite Modification: Add 6g of isoeugenol and 52g of modifier to the polyether-type polyurethane prepolymer, stir at 1500r / min for 15min, then add 10g of dispersant (6g of povidone PVP-K30 and 4g of hydroxyethyl cellulose), continue stirring for 1h, ultrasonically disperse at 400W for 30min, then add 30g of 1,4-butanediol, heat to 55℃, add 80g of acetone and 4.8g of sorbic acid, stir for 30min, then degas under nitrogen protection for 30min at a vacuum degree of -0.08MPa to obtain the modified polyurethane resin system; S103, Preparation of UV-resistant TPU film: Using a doctor blade coater, the modified polyurethane resin system was coated onto the PET release film at a speed of 2 m / min, with the coating thickness controlled at 80 μm. After drying in a 60°C oven for 3 hours to remove the solvent, the temperature was raised to 100°C and hot-pressed for 2 hours at a pressure of 0.3 MPa. After cooling to room temperature, the PET release film was peeled off and cured in a 40°C oven for 12 hours to obtain a UV-resistant TPU film.

[0024] The method for preparing the modifier used is as follows: Dissolve 10g of cyclodextrin in 85g of deionized water, stir at 60℃ until transparent, add 2g of isoeugenol, stir at constant temperature for 1.5h, filter, dry at 60℃ for 3h, grind to particle size ≤5μm to obtain inclusion complex. 36g of hydrotalcite was dispersed in 150g of 95wt% ethanol solution. After ultrasonic dispersion at 300W for 20min, 13g of nano-zirconium carbide and 8g of inclusion complex were added. Ultrasonic dispersion was continued for 50min. Then, 0.7g of low molecular weight polypyrrole (10000Da) was added. The mixture was heated to 65℃ and stirred for 2h. After centrifugation (8000r / min, 15min), the mixture was dried at 80℃ for 5h to obtain the modifier.

[0025] Example 2 The difference from Example 1 is that in this example, the solvent acetone is completely replaced with ethyl acetate, the catalyst is replaced with triethylenediamine, and low molecular weight polypyrrole is not added in the preparation of the modifier.

[0026] Example 3 The method for preparing the UV-resistant TPU film provided in this embodiment is as follows: S301, Prepolymer Preparation: 220g of polytetramethylene ether glycol PTMEG-1000 and 60g of polypropylene glycol PPG-1000 were added to a reactor. After dehydration at 95℃ and -0.09MPa for 3 hours, the temperature was lowered to 55℃. 80g of isophorone diisocyanate was added and stirred evenly. Then, 0.4g of dibutyltin dilaurate was added dropwise. The temperature was raised to 80℃ under nitrogen protection and reacted for 2 hours. After cooling to 45℃, 112g of acetone was added and stirred to disperse the mixture to obtain a polyether-type polyurethane prepolymer. S302, Composite Modification: Add 4g of 2-hydroxy-4-methoxybenzophenone and 52g of modifier to a polyether-type polyurethane prepolymer. Stir at 1500r / min for 10min, then add 8g of povidone PVP-K30 and continue stirring for 1h. After ultrasonic dispersion at 300W for 40min, add 28g of 1,4-butanediol. Heat to 50℃, add 72g of acetone and 4g of sorbic acid, stir for 20min, and then degas under nitrogen protection for 30min at a vacuum degree of -0.08MPa to obtain a modified polyurethane resin system. Preparation of S303, UV-resistant TPU film: Using a doctor blade coater, the modified polyurethane resin system was coated onto the PET release film at a speed of 2 m / min, with the coating thickness controlled at 50 μm. After drying in a 50°C oven for 3 hours to remove the solvent, the temperature was raised to 100°C and hot-pressed for 1 hour at a pressure of 0.3 MPa. After cooling to room temperature, the PET release film was peeled off and cured in a 40°C oven for 10 hours to obtain a UV-resistant TPU film.

[0027] The method for preparing the modifier used is as follows: Dissolve 10g of cyclodextrin in 80g of deionized water, stir at 60℃ until transparent, add 2g of 2-hydroxy-4-methoxybenzophenone, stir at constant temperature for 1h, filter, dry at 60℃ for 3h, grind to particle size ≤5μm to obtain inclusion complex; 36g of hydrotalcite was dispersed in 144g of 95wt% ethanol solution. After ultrasonic dispersion at 300W for 25min, 12.6g of nano-zirconium carbide and 7.2g of inclusion complex were added. Ultrasonic dispersion was continued for 45min. Then, 0.36g of low molecular weight polypyrrole (10000Da) was added. The mixture was heated to 65℃ and stirred for 2h. After centrifugation (8000r / min, 15min), the mixture was dried at 80℃ for 5h to obtain the modifier.

[0028] Example 4 The method for preparing the UV-resistant TPU film provided in this embodiment is as follows: S401, Prepolymer Preparation: 260g of polytetramethylene ether glycol PTMEG-2000 and 100g of polypropylene glycol PPG-1000 were added to a reactor. After dehydration at 105℃ and -0.09MPa for 2 hours, the temperature was lowered to 65℃, 120g of hexamethylene diisocyanate was added, and after stirring evenly, 0.8g of dibutyltin dilaurate was added dropwise. The temperature was raised to 80℃ under nitrogen protection and reacted for 4 hours. After cooling to 38℃, 128g of acetone was added, and after stirring and dispersing, a polyether-type polyurethane prepolymer was obtained. S402, Composite Modification: Add 8g of isoeugenol and 60g of modifier to the polyether-type polyurethane prepolymer, stir at 1500r / min for 15min, then add 12g of dispersant (7.2g of povidone PVP-K30 and 4.8g of hydroxyethyl cellulose), continue stirring for 1.5h, ultrasonically disperse at 400W for 40min, then add 32g of ethylene glycol, heat to 60℃, add 88g of acetone and 6g of sorbic acid, stir for 30min, then degas under nitrogen protection for 30min at a vacuum degree of -0.08MPa to obtain the modified polyurethane resin system; Preparation of S403, UV-resistant TPU film: Using a doctor blade coater, the modified polyurethane resin system was coated onto the PET release film at a speed of 3 m / min, with the coating thickness controlled at 100 μm. After drying in an oven at 55°C for 4 h to remove the solvent, the temperature was raised to 110°C and hot-pressed for 1.5 h at a pressure of 0.3 MPa. After cooling to room temperature, the PET release film was peeled off and cured in an oven at 40°C for 12 h to obtain a UV-resistant TPU film.

[0029] The method for preparing the modifier used is as follows: Dissolve 12g of cyclodextrin in 108g of deionized water, stir at 55℃ until transparent, add 3g of isoeugenol, stir at constant temperature for 2h, filter, dry at 60℃ for 3h, grind to particle size ≤5μm to obtain inclusion complex. 40g of hydrotalcite was dispersed in 200g of 95wt% ethanol solution. After ultrasonic dispersion at 300W for 30min, 14g of nano-zirconium carbide and 9.2g of inclusion complex were added. Ultrasonic dispersion was continued for 60min. Then, 1.2g of low molecular weight polypyrrole (10000Da) was added. The mixture was heated to 70℃ and stirred for 3h. After centrifugation (8000r / min, 15min), the mixture was dried at 80℃ for 5h to obtain the modifier.

[0030] Example 5 The difference from Embodiment 1 is that, in this embodiment, steps S2 and S3 include the following steps: S502, Composite Modification: Add 48g of modifier to the polyether-type polyurethane prepolymer, stir at 1500r / min for 15min, then add 10g of hydroxyethyl cellulose, continue stirring for 1h, ultrasonically disperse at 400W for 30min, then add 30g of 1,4-butanediol, heat to 55℃, add 80g of acetone and 4.8g of sorbic acid, stir for 30min, then degas under nitrogen protection for 20min at a vacuum degree of -0.08MPa to obtain the modified polyurethane resin system.

[0031] Preparation of S503, UV-resistant TPU film: Using a doctor blade coater, the modified polyurethane resin system was coated onto the PET release film at a speed of 2.5 m / min, with the coating thickness controlled at 80 μm. After drying in a 60°C oven for 3 hours to remove the solvent, the temperature was raised to 100°C and hot-pressed for 2 hours at a pressure of 0.3 MPa. After cooling to room temperature, the PET release film was peeled off and cured in a 40°C oven for 11 hours to obtain a UV-resistant TPU film.

[0032] Furthermore, in the preparation of the modifier, the amount of nano-zirconium carbide added was 4.4g, and the amount of inclusion compound added was 9g.

[0033] Comparative Example 1 The difference between this comparative example and Example 1 is that no modifier is added in step S102.

[0034] Comparative Example 2 The difference between this comparative example and Example 1 is that no catalyst is added in step S101, and no inclusion complex is added in the preparation of the modifier in step S102.

[0035] Comparative Example 3 The difference between this comparative example and Example 1 is that cyclodextrin is not added in the preparation of the modifier in step S102.

[0036] The UV-resistant TPU films (hereinafter referred to as "TPU films") prepared by the preparation methods provided in the above embodiments and comparative examples were tested.

[0037] UV blocking rate and yellowing resistance: The UVB-313 ultraviolet aging lamp was used to directly shine on the TPU film, and the ultraviolet blocking rate was tested from below the TPU film using an ultraviolet blocking rate tester.

[0038] Referring to GB / T 39822-2021 "Determination of Yellow Index and its Change Value of Plastics", UVB-313 ultraviolet accelerated aging was used for 168 hours, and the change value ΔYI of yellow index was tested.

[0039] The results are shown in Table 1.

[0040] Table 1 Examples 1 and 4 showed the smallest change in yellow index ΔYI, indicating the best resistance to yellowing. All examples and comparative examples used aliphatic isocyanates. The hydrophobic cavities of the cyclodextrin modifier stabilized the UV-absorbing monomers within the TPU substrate (polytetramethylene ether glycol), preventing migration or volatilization and improving the compatibility between the organic UV absorber and the TPU substrate. The layered structure of hydrotalcite further enhanced the path-blocking effect of UV light, while its alkaline sites neutralized acidic free radicals generated by UV degradation, inhibiting the spread of chain degradation reactions. The conjugated structure of polypyrrole efficiently captured active free radicals induced by UV light, terminating the chain degradation reaction and indirectly reducing UV damage to the substrate. Example 2, lacking polypyrrole, retained absorption and shielding functions but lacked a free radical scavenging mechanism, allowing some UV light to still cause slight degradation of the substrate. Furthermore, the replacement of the solvent and catalyst somewhat affected the system compatibility, resulting in a slightly lower UV blocking rate than Examples 1 and 4.

[0041] Mechanical strength: Referring to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", dumbbell-shaped type 4 specimens (thickness is the actual thickness of the sample) were cut, and the tensile strength and elongation at break were tested at a tensile speed of 50 mm / min.

[0042] Elongation at break = (gauge length at break - initial gauge length) / initial gauge length × 100% Abrasion resistance: Cut a 100mm×100mm sample, fix it flat on the sample stage, load it with 500g, rotate it at 75r / min, and wear it for 1000 cycles. Calculate the wear resistance rate.

[0043] Wear resistance rate = (mass before wear - mass after wear) / number of wear cycles × 100% The results are shown in Table 2.

[0044] Table 2 Both Examples 1 and 4 used PTMEG-2000 long-chain polyether as the main soft segment, which exhibited good molecular chain flexibility and high elongation at break. Furthermore, the cyclodextrin inclusion complex improved the compatibility of antioxidants and other auxiliaries with TPU, avoiding the obstruction of molecular chain movement by rigid particles. Example 2, lacking polypyrrole as a modifier, had insufficient free radical scavenging ability, resulting in slight molecular chain degradation, decreased flexibility, and a lower elongation than Example 1.

[0045] In Example 4, ethylene glycol was used as a chain extender, and the hard segment crosslinking density was slightly higher than that in Example 1, which used 1,4-butanediol for chain extension, thus the tensile strength was slightly improved. In Example 3, PTMEG-1000 had a lower molecular weight than PTMEG-2000 used in Example 1, and the degree of molecular chain entanglement was insufficient, resulting in an overall strength lower than that of Example 1. In Comparative Example 2, the catalyst was lacking, the prepolymerization reaction was incomplete, the TPU molecular chain length was uneven, the crosslinking density was low, and the tensile strength was the lowest.

[0046] Furthermore, the nano-zirconium carbide and hydrotalcite added to the modifier improve the surface density and internal compactness of the TPU film to a certain extent. The cyclodextrin inclusion complex and dispersant enhance the interfacial bonding force between the modifier and TPU, making the particles less likely to fall off during wear and resulting in good wear resistance. The comparative example 1 without added modifier has low hardness and the greatest wear.

[0047] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a UV-resistant TPU film, characterized in that, It includes the following steps: S1. Prepolymer preparation: According to the mass fractions, 55-65 parts of polytetramethylene ether glycol and 15-25 parts of polypropylene glycol are added to a reactor. After vacuum dehydration at 95-105°C for 2-3 hours, the temperature is lowered to 55-65°C, 20-30 parts of aliphatic isocyanate are added, and after stirring evenly, 0.1-0.2 parts of catalyst are added dropwise. Under nitrogen protection, the temperature is raised to 75-80°C and reacted for 2-4 hours. After cooling to 38-45°C, 28-32 parts of solvent are added, and after stirring and dispersing, a polyether-type polyurethane prepolymer is obtained. S2, Composite Modification: Add 1-2 parts of UV-absorbing functional monomer and 12-15 parts of modifier to the polyether-type polyurethane prepolymer, stir at high speed for 10-15 min, add 2-3 parts of dispersant, continue stirring for 1-1.5 h, ultrasonically disperse for 30-40 min, add 7-8 parts of chain extender, heat to 50-60℃, add 18-22 parts of solvent and 1-1.5 parts of antioxidant, stir for 20-30 min, and degas under nitrogen protection for 20-30 min to obtain the modified polyurethane resin system; S3. Preparation of UV-resistant TPU film: The modified polyurethane resin system was coated onto a PET release film, dried at 50-60°C for 3-4 hours, then heated to 100-110°C and hot-pressed for 1-2 hours. After cooling to room temperature, the PET release film was peeled off and cured for 10-12 hours to obtain a UV-resistant TPU film. The preparation method of the modifier includes the following steps: Cyclodextrin was dissolved in deionized water at a mass ratio of 1:8~9, stirred at 55~60℃ until transparent, then a UV-absorbing functional monomer was added, stirred at a constant temperature for 1~2 hours, filtered and dried to obtain the inclusion complex. The mass ratio of the UV-absorbing functional monomer to cyclodextrin was 1:4~5. Hydrotalcite was dispersed in 95wt% ethanol solution at a mass ratio of 1:4~5. After ultrasonic dispersion for 20~30 min, nano-zirconium carbide and inclusion complex were added, and ultrasonication was continued for 45~60 min. After heating to 65~70℃, the mixture was stirred for 2~3 h, centrifuged, and dried to obtain the modifier. The amount of nano-zirconium carbide added is 35-40% of the mass of hydrotalcite, and the amount of inclusion complex added is 20-25% of the mass of hydrotalcite.

2. The method for preparing the UV-resistant TPU film as described in claim 1, characterized in that: In S1, the aliphatic isocyanate is selected from one of hexamethylene diisocyanate and isophorone diisocyanate; The catalyst is selected from one of dibutyltin dilaurate and triethylenediamine.

3. The method for preparing the UV-resistant TPU film as described in claim 1, characterized in that: In S2, the antioxidant is selected from sorbic acid; The chain extender is selected from aliphatic chain extenders, and the aliphatic chain extender is selected from one of 1,4-butanediol and ethylene glycol.

4. The method for preparing the UV-resistant TPU film as described in claim 1, characterized in that: In S2, the dispersant is selected from at least one of polyvinylpyrrolidone and carboxyethyl cellulose.

5. The method for preparing the UV-resistant TPU film as described in claim 4, characterized in that: The dispersant comprises polyvinyl ketone and carboxyethyl cellulose in a mass ratio of 3:

2.

6. The method for preparing the UV-resistant TPU film as described in claim 1, characterized in that: In S1 and S2, the solvent is selected from either ethyl acetate or acetone.

7. The method for preparing the UV-resistant TPU film as described in claim 1, characterized in that: The preparation method of the modifier, after adding nano-zirconium carbide and its inclusion complex and continuing sonication, also includes the following steps: Add low molecular weight polypyrrole and ultrasonically disperse for 15-20 minutes; The amount of low molecular weight polypyrrole added is 1 to 3% of the mass of hydrotalcite.

8. The method for preparing the UV-resistant TPU film as described in claim 1, characterized in that: The ultraviolet absorption functional monomer is selected from isoeugenol or 2-hydroxy-4-methoxybenzophenone.

9. The method for preparing the UV-resistant TPU film as described in claim 1, characterized in that: In step S3, the coating thickness is 50~100μm; the coating is performed using a doctor blade coater at a speed of 2~3m / min.

10. A UV-resistant TPU film, characterized in that, It is prepared by the method for preparing UV-resistant TPU film as described in any one of claims 1 to 9.

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