Macromolecular TPU (thermoplastic polyurethane) vehicle color-changing film and preparation method thereof

Abstract

The invention relates to the field of color changing films, in particular to a macromolecular TPU color changing film for a vehicle and a preparation method thereof.The macromolecular TPU color changing film comprises a surface layer, a middle layer and a bonding layer, and the surface layer is prepared from, by mass, 85-90 parts of aliphatic polyether type TPU, 5-8 parts of perfluoropolyether glycol, 3-5 parts of an amino silane coupling agent, 0.5-1 part of an ultraviolet absorbent and 0.3-0.5 part of a hindered amine light stabilizer; through the three-layer composite structure design of the functional surface layer, the intelligent middle layer and the high-viscosity bottom layer and by combining the layered temperature control co-extrusion and electron beam curing technology, compared with the prior art, the weather resistance and pollution resistance of the film material are remarkably improved, the scratch self-repairing function is achieved, and the lasting bonding stability is enhanced; meanwhile, the processing integrity of functional components is guaranteed, and the method has a wide application prospect in the field of customized color change of high-end automobiles.

Description

Technical Field

[0001] This invention relates to the field of color-changing films, and more particularly to a polymer TPU automotive color-changing film and its preparation method. Background Technology

[0002] TPU automotive color-changing film is a multi-layered functional film based on thermoplastic polyurethane. It achieves customized car exterior colors through surface lamination and also has functions such as protecting the paint from weathering and aging, preventing scratches, and decoration.

[0003] In existing technologies, traditional automotive color-changing films suffer from insufficient weather resistance of the substrate, which easily leads to yellowing and embrittlement after long-term exposure, resulting in a significantly shortened service life. At the same time, their functional design is limited and cannot effectively repair everyday scratches and damage, reducing their practical value. In addition, due to the poor reliability of the adhesive system, they are prone to delamination failure under high temperature environments, affecting long-term stability. Furthermore, conventional high-temperature co-extrusion processes can damage the structure of functional components, causing the self-healing mechanism to fail and the protective performance to decline, ultimately resulting in low product yield.

[0004] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a polymer TPU automotive color-changing film and its preparation method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a polymer TPU automotive color-changing film and its preparation method, so as to solve the problems of insufficient weather resistance of the substrate, limited functionality, poor reliability of the adhesive layer, and damage to functionality by the processing technology in the prior art.

[0006] To achieve the above objectives, the present invention provides a polymer TPU automotive color-changing film and its preparation method.

[0007] A polymeric TPU automotive color-changing film includes a surface layer, an intermediate layer, and an adhesive layer. The surface layer is composed of the following components in parts by weight: 85-90 parts aliphatic polyether TPU, 5-8 parts perfluoropolyether glycol, 3-5 parts aminosilane coupling agent, 0.5-1 part ultraviolet absorber, 0.3-0.5 parts hindered amine light stabilizer, and 0.2-0.5 parts lubricant. The intermediate layer is composed of the following components in parts by weight: 90-92 parts of modified polytetrahydrofuran diol 1000, 8-10 parts of microcapsules, 0.5-1 part of polyether-modified siloxane, and 0.3-0.5 parts of antioxidant. The adhesive layer is composed of the following components in parts by weight: 88-90 parts of modified polybutylene adipate diol, 4-6 parts of sodium dimyristoyl phosphate, 1-2 parts of zinc oxide nanoparticles, 3-5 parts of hydrogenated rosin glycerol ester, and 0.5-1 parts of nano silica.

[0008] Preferably, the preparation steps of the aliphatic polyether type TPU are as follows: Under a nitrogen atmosphere, polytetrahydrofurandiol 2000 was added to a flask, heated to 80-90℃, and hexamethylene diisocyanate and dibutyltin dilaurate catalyst were added. The reaction was carried out for 80-100 minutes. After the reaction was completed, the temperature was lowered to 65-75℃, 1,4-butanediol was added, and the mixture was placed in a high-shear mixing head and mixed for 3-5 seconds. The mixture was then injected into a twin-screw extruder, and antioxidant 1135, UV absorber UV-384, light stabilizer 292 and silicone masterbatch were added. The temperature was raised to 150-160℃, granulated, and dried to obtain aliphatic polyether type TPU. Aliphatic polyether TPU is a yellowing-resistant substrate. It is combined with perfluoropolyether glycol and aminosilane coupling agent to enhance component compatibility. UV absorber UV-384 and hindered amine light stabilizer 292 are added to form a synergistic protection against photo-oxidative aging. At the same time, the perfluoropolyether is uniformly dispersed at high temperature to form a dense protective layer, which improves stain resistance and long-lasting color stability.

[0009] Preferably, the mass ratio of polytetrahydrofuran diol 2000, hexamethylene diisocyanate, 1,4-butanediol, catalyst, antioxidant 1135, ultraviolet absorber UV-384, light stabilizer 292 to silicone masterbatch is 1:0.32-0.33:0.09-0.1:0.0002-0.0004:0.007-0.009:0.004-0.006:0.002-0.004:0.001-0.003.

[0010] Preferably, the preparation steps of the modified polytetrahydrofuran diol 1000 are as follows: Under a nitrogen atmosphere, polytetrahydrofurandiol 1000 was added to a flask, heated to 80-90°C, and hexamethylene diisocyanate and dibutyltin dilaurate catalyst were added. The reaction was carried out for 80-100 minutes until the reaction was complete. The temperature was then lowered to 65-75°C, and 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 20-40 seconds. The mixture was then injected into a twin-screw extruder, heated to 90-110°C, and antioxidant 1076 and light stabilizer 622 were added. The temperature was then raised to 150-160°C, granulated, and dried to obtain modified polytetrahydrofurandiol 1000.

[0011] Preferably, the mass ratio of polytetrahydrofuran diol 1000, hexamethylene diisocyanate, 1,4-butanediol, catalyst, antioxidant 1076, and light stabilizer 622 is 1:0.36-0.37:0.045-0.055:0.0001-0.0003:0.0014-0.0016:0.0002-0.0004. Preferably, the microcapsule preparation steps are as follows: Step A1: Add indoline spiropyran to toluene solvent, heat to 40-60℃, stir for 20-40 min to obtain core material solution; Step A2: Under a nitrogen atmosphere, toluene diisocyanate is added to trimethylolpropane, the temperature is raised to 50-70℃, the reaction is carried out for 1-3 hours, the temperature is lowered to 30-40℃, the core material solution is added, and the mixture is stirred for 10-12 minutes to obtain an oil phase solution. Step A3: Add polyvinyl alcohol to deionized water, heat to 50-70℃, stir for 50-70 min, cool to 10-20℃, add oil phase solution, place in a high-speed disperser, speed 7000-9000 rpm, emulsify for 4-6 min, then heat to 30-40℃, add chain extender ethylenediamine, react for 3-5 h, add 5% sodium hydroxide solution, adjust pH to 8.5-9.0, distill under reduced pressure, add isophorone diisocyanate, heat to 40-50℃, react for 1-3 h, centrifuge, wash, dry and sieve to obtain microcapsules; The microcapsule wall material is a polymer of toluene diisocyanate and trimethylolpropane. When stimulated by ultraviolet light, the core material undergoes molecular isomerization, releasing active components to fill surface scratches. Meanwhile, the microcapsules are prepared by a three-step method of emulsion polymerization-chain extension-secondary coating. The emulsification speed and pH are strictly controlled to ensure the integrity of the capsule wall and the response sensitivity. During co-extrusion, the microcapsules are added by side feeding to avoid high-temperature shearing damage to the structure.

[0012] Preferably, the mass ratio of toluene diisocyanate, trimethylolpropane, and core material solution in step A2 is 0.48-0.52:0.48-0.52:1. The mass ratio of polyvinyl alcohol, deionized water, oil phase solution, chain extender and isophorone diisocyanate in step A3 is 0.32-0.34: 16.5-16.7: 1: 0.04-0.06: 0.082-0.084.

[0013] Preferably, the preparation steps of the modified polybutylene adipate diol are as follows: Step B1: Under a nitrogen atmosphere, polybutylene adipate diol is added to a flask, heated to 80-90℃, 4,4'-diphenylmethane diisocyanate is added, and the reaction is carried out for 80-100 min. After the reaction is completed, the temperature is lowered to 65-75℃, and a 40% N-methylpyrrolidone solution of dimethylolpropionic acid is added. The reaction is carried out for 2-4 h to obtain the prepolymer. Step B2: Add the prepolymer to a flask, heat to 40-60℃, add triethylamine, stir for 8-12 minutes, adjust the pH to 7.5-8.0, add 1,4-butanediol and ethylene glycol, place in a high-shear emulsifier, emulsify for 50-70 seconds to obtain an emulsion; Step B3: Add the emulsion to deionized water, heat to 30-50℃, add ethylenediamine and nano zinc oxide, stir for 8-10 minutes, filter, wash, dry, place in a twin-screw extruder, add antioxidant, UV stabilizer and nano silica, heat to 170-190℃, granulate, and obtain modified polybutylene adipate diol. The mass ratio of the polybutylene adipate diol, 4,4'-diphenylmethane diisocyanate, and N-methylpyrrolidone solution of dimethylolpropionic acid is 1:0.33-0.34:0.1-0.11; The mass ratio of the prepolymer, triethylamine, 1,4-butanediol, and ethylene glycol is 1:0.02-0.022:0.06-0.062:0.01-0.011; The mass ratio of the emulsion, ethylenediamine, nano zinc oxide, antioxidant, UV stabilizer and nano silica is 1:0.0031-0.0033:0.01-0.012:0.003-0.005:0.001-0.003:0.0032-0.0034.

[0014] Preferably, the preparation steps of the polyether-modified siloxane are as follows: Under a nitrogen atmosphere, hydrogen-containing silicone oil and allyl polyether are added to isopropanol, heated to 80-90℃, sodium acetate and platinum catalyst are added, the reaction is carried out for 3-5 hours, the temperature is lowered to 50-70℃, activated clay is added, the mixture is stirred for 50-70 minutes, filtered and washed, and then distilled under reduced pressure to obtain polyether-modified siloxane. The mass ratio of the hydrogen-containing silicone oil, allyl polyether, isopropanol, sodium acetate, platinum catalyst, and activated clay is 1:1.7-1.9:0.4-0.6:0.0008-0.0012:0.0004-0.0006:0.04-0.06.

[0015] A method for preparing a polymer TPU automotive color-changing film, the preparation steps of which are as follows: Step S1: Add aliphatic polyether TPU, perfluoropolyether glycol and aminoethylaminopropyltrimethoxysilane into a high-speed mixer, dry mix for 3-7 minutes at a speed of 700-900 rpm, place in a twin-screw reactor, heat to 180-200℃, granulate and dry to obtain surface TPU particles. Step S2: Add the modified polybutylene adipate diol to the internal mixer, heat to 150-170℃, mix for 1-3 minutes at 20-40 rpm, add sodium dimyroyl phosphate and nano zinc oxide, mix for 6-10 minutes at 50-70 rpm, transfer to a two-roll mill with a roll gap of 0.4-0.6 mm, pass through a thin mill 4-6 times, and produce a 2 mm sheet. Air cool at 40-60℃ to obtain the adhesive layer sheet. Step S3: Add the surface TPU particles to a single-screw extruder, heat to 180-210℃, and screw speed 35-40 rpm. Add the adhesive layer sheet to the single-screw extruder, heat to 165-185℃, and screw speed 30-35 rpm. Then, add the modified polytetrahydrofuran diol to a twin-screw extruder, heat to 180-220℃, and screw speed 25-30 rpm. Add the polyether-modified siloxane and antioxidant. Add the microcapsules via a side feeder. The shear rate is 1200-1400 s. -1 Mix for 20-30 seconds, then add maleic anhydride, polyethylene octene polymer and initiator dicumyl peroxide, cool to 150-170℃, extrude to a thickness of 0.045-0.055mm, and cure by electron beam layering to obtain automotive color-changing film. The adhesive layer uses modified polybutylene adipate diol as the matrix, with added sodium dimyristoyl phosphate and zinc oxide nanoparticles. Hydrogenated rosin glycerol ester enhances the initial tack, and nano silica strengthens the mechanical anchoring. At the same time, the adhesive layer is mixed in stages using an internal mixer and an open mill to ensure uniform dispersion of nanoparticles and avoid agglomeration failure. By ensuring fluidity through high-temperature extrusion of the surface layer, preventing thermal degradation through low-temperature processing of the adhesive layer, avoiding thermal damage through side-feeding of microcapsules in the intermediate layer, and replacing thermal curing with electron beam layered curing, the degree of crosslinking is precisely controlled to achieve low-temperature and high-efficiency molding. This reduces the damage of high temperatures to microcapsules and light stabilizers, improves product yield, and reduces energy consumption.

[0016] The mass ratio of the aliphatic polyether TPU, perfluoropolyether glycol, and aminoethylaminopropyltrimethoxysilane is 1:0.065-0.07:0.04-0.05. The mass ratio of the modified polybutylene adipate diol, sodium dimyristoyl phosphate, and nano zinc oxide is 1:0.05-0.06:0.015-0.02. The mass ratio of the surface TPU particles, adhesive sheet, modified polytetrahydrofuran diol, polyether-modified siloxane, antioxidant, microcapsules, maleic anhydride, polyvinyl octene polymer, and initiator dicumyl peroxide is 1:0.9-1.1:4.2-4.3:0.045-0.05:0.022-0.024:0.44-0.48:0.044-0.048:0.022-0.024:0.012-0.014.

[0017] The beneficial effects of this invention are: This invention provides a high-performance automotive TPU color-changing film and its preparation process. The invention utilizes a three-layer composite structure design consisting of a functionalized surface layer, an intelligent intermediate layer, and a high-adhesion bottom layer. Combined with layered temperature-controlled co-extrusion and electron beam curing technology, this invention significantly improves the film's weather resistance and stain resistance, enables scratch self-healing, and enhances long-lasting adhesion stability compared to existing technologies. At the same time, it ensures the integrity of the functional components during processing and has broad application prospects in the field of customized color-changing for high-end automobiles. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] Example 1: The preparation steps of aliphatic polyether TPU are as follows: Under a nitrogen atmosphere, 100g of polytetrahydrofuran glycol 2000 was added to a flask, heated to 80°C, and 32g of hexamethylene diisocyanate and 0.02g of dibutyltin dilaurate catalyst were added. The reaction was carried out for 100 minutes until the reaction was complete. The temperature was then lowered to 65°C, and 9g of 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 5 seconds. The mixture was then injected into a twin-screw extruder, and 0.7g of antioxidant 1135, 0.4g of UV absorber UV-384, 0.2g of light stabilizer 292, and 0.1g of silicone masterbatch were added. The mixture was heated to 150°C, granulated, and dried to obtain aliphatic polyether TPU.

[0020] Example 2: The preparation steps of aliphatic polyether TPU are as follows: Under a nitrogen atmosphere, 100g of polytetrahydrofuran glycol 2000 was added to a flask, heated to 85°C, and 32.5g of hexamethylene diisocyanate and 0.03g of dibutyltin dilaurate catalyst were added. The reaction was carried out for 90 minutes until completion. The temperature was then lowered to 70°C, and 9.5g of 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 4 seconds. The mixture was then injected into a twin-screw extruder, and 0.8g of antioxidant 1135, 0.5g of UV absorber UV-384, 0.3g of light stabilizer 292, and 0.2g of silicone masterbatch were added. The mixture was heated to 155°C, granulated, and dried to obtain aliphatic polyether TPU.

[0021] Example 3: The preparation steps of aliphatic polyether TPU are as follows: Under a nitrogen atmosphere, 100g of polytetrahydrofuran glycol 2000 was added to a flask, heated to 90°C, and 33g of hexamethylene diisocyanate and 0.04g of dibutyltin dilaurate catalyst were added. The reaction was carried out for 80 minutes until the reaction was complete. The temperature was then lowered to 75°C, and 10g of 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 3 seconds. The mixture was then injected into a twin-screw extruder, and 0.9g of antioxidant 1135, 0.6g of UV absorber UV-384, 0.4g of light stabilizer 292, and 0.3g of silicone masterbatch were added. The mixture was heated to 160°C, granulated, and dried to obtain aliphatic polyether TPU.

[0022] Example 4: The preparation steps of the modified polytetrahydrofuran diol 1000 are as follows: Under a nitrogen atmosphere, 100g of polytetrahydrofurandiol 1000 was added to a flask, heated to 80°C, and 36g of hexamethylene diisocyanate and 0.01g of dibutyltin dilaurate catalyst were added. The reaction was carried out for 100 min until the reaction was complete. The temperature was then lowered to 65°C, and 4.5g of 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 40 s. The mixture was then injected into a twin-screw extruder, heated to 90°C, and 0.14g of antioxidant 1076 and 0.002g of light stabilizer 622 were added. The temperature was then raised to 160°C, granulated, and dried to obtain modified polytetrahydrofurandiol 1000.

[0023] Example 5: The preparation steps of the modified polytetrahydrofuran diol 1000 are as follows: Under a nitrogen atmosphere, 100g of polytetrahydrofuran glycol 1000 was added to a flask, heated to 85°C, and 36.5g of hexamethylene diisocyanate and 0.02g of dibutyltin dilaurate catalyst were added. The reaction was carried out for 90 minutes until completion. The temperature was then lowered to 70°C, and 5g of 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 30 seconds. The mixture was then injected into a twin-screw extruder, heated to 100°C, and 0.15g of antioxidant 1076 and 0.03g of light stabilizer 622 were added. The mixture was then heated to 155°C, granulated, and dried to obtain modified polytetrahydrofuran glycol 1000.

[0024] Example 6: The preparation steps of the modified polytetrahydrofuran diol 1000 are as follows: Under a nitrogen atmosphere, 100g of polytetrahydrofuran glycol 1000 was added to a flask, heated to 90°C, and 37g of hexamethylene diisocyanate and 0.03g of dibutyltin dilaurate catalyst were added. The reaction was carried out for 80 minutes until completion. The temperature was then lowered to 75°C, and 5.5g of 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 20 seconds. The mixture was then injected into a twin-screw extruder, heated to 110°C, and 0.16g of antioxidant 1076 and 0.04g of light stabilizer 622 were added. The temperature was then raised to 150°C, granulated, and dried to obtain modified polytetrahydrofuran glycol 1000.

[0025] Example 7: The microcapsule preparation steps are as follows: S1: Add 100g of indoline spiropyran to 150mL of toluene solvent, heat to 40℃, stir for 40min to obtain core material solution; S2: Under a nitrogen atmosphere, 48g of toluene diisocyanate was added to 48g of trimethylolpropane, the temperature was raised to 50℃, the reaction was carried out for 3h, the temperature was lowered to 30℃, 100g of core material solution was added, and the mixture was stirred for 10min to obtain an oil phase solution. S3: Add 32g of polyvinyl alcohol to 1650g of deionized water, heat to 50℃, stir for 70min, cool to 10℃, add 100g of oil phase solution, place in a high-speed disperser, rotate at 7000rpm, emulsify for 6min, then heat to 30℃, add 4g of chain extender ethylenediamine, react for 3h, add 5% sodium hydroxide solution, adjust pH to 8.5-9.0, distill under reduced pressure, add 8.2g of isophorone diisocyanate, heat to 40℃, react for 3h, centrifuge, wash, dry and sieve to obtain microcapsules.

[0026] Example 8: The microcapsule preparation steps are as follows: S1: Add 100g of indoline spiropyran to 150mL of toluene solvent, heat to 50℃, stir for 30min to obtain core material solution; S2: Under a nitrogen atmosphere, 50g of toluene diisocyanate was added to 50g of trimethylolpropane, the temperature was raised to 60℃, the reaction was carried out for 2 hours, the temperature was lowered to 35℃, 100g of core material solution was added, and the mixture was stirred for 11 minutes to obtain an oil phase solution. S3: Add 34g of polyvinyl alcohol to 1660g of deionized water, heat to 60℃, stir for 60min, cool to 15℃, add 100g of oil phase solution, place in a high-speed disperser, spin at 8000rpm, emulsify for 5min, then heat to 35℃, add 5g of chain extender ethylenediamine, react for 4h, add 5% sodium hydroxide solution, adjust pH to 8.5-9.0, distill under reduced pressure, add 8.3g of isophorone diisocyanate, heat to 45℃, react for 2h, centrifuge, wash, dry and sieve to obtain microcapsules.

[0027] Example 9: The microcapsule preparation steps are as follows: S1: Add 100g of indoline spiropyran to 150mL of toluene solvent, heat to 60℃, stir for 20min to obtain core material solution; S2: Under a nitrogen atmosphere, 52g of toluene diisocyanate was added to 52g of trimethylolpropane, the temperature was raised to 70℃, the reaction was carried out for 1h, the temperature was lowered to 40℃, 100g of core material solution was added, and the mixture was stirred for 10min to obtain an oil phase solution. S3: Add 34g of polyvinyl alcohol to 1670g of deionized water, heat to 50℃, stir for 70min, cool to 10℃, add 100g of oil phase solution, place in a high-speed disperser, rotate at 7000rpm, emulsify for 6min, then heat to 30℃, add 6g of chain extender ethylenediamine, react for 5h, add 5% sodium hydroxide solution, adjust pH to 8.5-9.0, distill under reduced pressure, add 8.4g of isophorone diisocyanate, heat to 45℃, react for 2h, centrifuge, wash, dry and sieve to obtain microcapsules.

[0028] Example 10: The preparation steps of the modified polybutylene adipate diol are as follows: S1: Under a nitrogen atmosphere, 100g of polybutylene adipate diol was added to a flask, the temperature was raised to 80℃, 34g of 4,4'-diphenylmethane diisocyanate was added, the reaction was carried out for 80min, the reaction was completed, the temperature was lowered to 75℃, 10g of 40% N-methylpyrrolidone solution of dimethylolpropionic acid was added, and the reaction was carried out for 2h to obtain the prepolymer; S2: Add 100g of prepolymer to a flask, heat to 50℃, add 2g of triethylamine, stir for 8min, adjust pH to 7.5-8.0, add 6g of 1,4-butanediol and 1g of ethylene glycol, place in a high-shear emulsifier, emulsify for 50s to obtain an emulsion. S3: Add 100g of emulsion to 150mL of deionized water, heat to 30℃, add 0.31g of ethylenediamine and 1g of nano zinc oxide, stir for 8min, filter, wash, dry, place in a twin-screw extruder, add 0.3g of antioxidant, 0.1g of UV stabilizer and 0.32g of nano silica, heat to 170℃, granulate, and obtain modified polybutylene adipate diol.

[0029] Example 11: The preparation steps of the modified polybutylene adipate diol are as follows: S1: Under a nitrogen atmosphere, 100g of polybutylene adipate diol was added to a flask, the temperature was raised to 85℃, 33.5g of 4,4'-diphenylmethane diisocyanate was added, the reaction was carried out for 90min, the reaction was completed, the temperature was lowered to 70℃, 10.5g of 40% N-methylpyrrolidone solution of dimethylolpropionic acid was added, and the reaction was carried out for 3h to obtain the prepolymer; S2: Add 100g of prepolymer to a flask, heat to 50℃, add 2.1g of triethylamine, stir for 10min, adjust pH to 7.5-8.0, add 6.1g of 1,4-butanediol and 1.5g of ethylene glycol, place in a high-shear emulsifier, emulsify for 60s to obtain an emulsion; S3: Add 100g of emulsion to 150mL of deionized water, heat to 40℃, add 0.32g of ethylenediamine and 1.1g of nano zinc oxide, stir for 9min, filter, wash, dry, place in a twin-screw extruder, add 0.4g of antioxidant, 0.2g of UV stabilizer and 0.33g of nano silica, heat to 180℃, granulate, and obtain modified polybutylene adipate diol.

[0030] Example 12: The preparation steps of the modified polybutylene adipate diol are as follows: S1: Under a nitrogen atmosphere, 100g of polybutylene adipate diol was added to a flask, the temperature was raised to 90℃, 34g of 4,4'-diphenylmethane diisocyanate was added, the reaction was carried out for 100min, the reaction was completed, the temperature was lowered to 75℃, 11g of 40% N-methylpyrrolidone solution of dimethylolpropionic acid was added, and the reaction was carried out for 2h to obtain the prepolymer; S2: Add 100g of prepolymer to a flask, heat to 60℃, add 2.2g of triethylamine, stir for 12min, adjust pH to 7.5-8.0, add 6.2g of 1,4-butanediol and 1.1g of ethylene glycol, place in a high-shear emulsifier, emulsify for 50s to obtain an emulsion; S3: Add 100g of emulsion to 150mL of deionized water, heat to 50℃, add 0.33g of ethylenediamine and 1.2g of nano zinc oxide, stir for 8min, filter, wash, dry, place in a twin-screw extruder, add 0.5g of antioxidant, 0.3g of UV stabilizer and 0.34g of nano silica, heat to 190℃, granulate, and obtain modified polybutylene adipate diol.

[0031] Example 13: The preparation steps of the polyether-modified siloxane are as follows: Under a nitrogen atmosphere, 100g of hydrogen-containing silicone oil and 170g of allyl polyether were added to 40g of isopropanol, heated to 80℃, and 0.08g of sodium acetate and 0.04g of platinum catalyst were added. The reaction was carried out for 3 hours, cooled to 70℃, and 4g of activated clay was added. The mixture was stirred for 50 minutes, filtered, washed, and distilled under reduced pressure to obtain polyether-modified siloxane.

[0032] Example 14: The preparation steps of the polyether-modified siloxane are as follows: Under a nitrogen atmosphere, 100g of hydrogen-containing silicone oil and 180g of allyl polyether were added to 50g of isopropanol, heated to 85°C, and 0.1g of sodium acetate and 0.05g of platinum catalyst were added. The mixture was reacted for 4 hours, cooled to 60°C, and 5g of activated clay was added. The mixture was stirred for 60 minutes, filtered, washed, and distilled under reduced pressure to obtain polyether-modified siloxane.

[0033] Example 15: The preparation steps of the polyether-modified siloxane are as follows: Under a nitrogen atmosphere, 100g of hydrogen-containing silicone oil and 190g of allyl polyether were added to 60g of isopropanol, heated to 90℃, and 0.12g of sodium acetate and 0.06g of platinum catalyst were added. The reaction was carried out for 3 hours, cooled to 70℃, and 6g of activated clay was added. The mixture was stirred for 50 minutes, filtered, washed, and distilled under reduced pressure to obtain polyether-modified siloxane.

[0034] Example 16: A method for preparing a polymer TPU automotive color-changing film S1: 100g of aliphatic polyether TPU, 6.5g of perfluorinated polyether glycol and 4g of aminoethylaminopropyltrimethoxysilane were put into a high-speed mixer, dry mixed for 3 minutes at 900 rpm, placed in a twin-screw reactor, heated to 180℃, granulated and dried to obtain surface TPU particles. S2: Add 100g of modified polybutylene adipate diol to a mixer, heat to 150℃, mix for 3 minutes at 20 rpm, add 5g of sodium dimyroyl phosphate and 1.5g of nano zinc oxide, mix for 6 minutes at 70 rpm, transfer to a two-roll mill with a roll gap of 0.4-0.6mm, pass through 4 times, produce a 2mm sheet, air cool at 60℃ to obtain the adhesive layer sheet; S3: Add 100g of surface TPU particles to a single-screw extruder, heat to 180℃, and set the screw speed to 40rpm. Add 90g of adhesive layer sheet to the single-screw extruder, heat to 165℃, and set the screw speed to 35rpm. Then, add 420g of modified polytetrahydrofuran diol to a twin-screw extruder, heat to 180℃, and set the screw speed to 30rpm. Add 4.5g of polyether-modified siloxane and 2.2g of antioxidant. Add 44g of microcapsules to the side feeder. The shear rate is 1200s. -1 Mix for 20 seconds, then add 4.4g of maleic anhydride, 2.2g of polyethylene octene polymer and 1.2g of initiator dicumyl peroxide. Cool to 150℃, extrude to a thickness of 0.045-0.055mm, and cure by electron beam layering to obtain automotive color-changing film.

[0035] Example 17: A method for preparing a polymer TPU automotive color-changing film S1: Add 100g of aliphatic polyether TPU, 6.8g of perfluorinated polyether glycol and 4.5g of aminoethylaminopropyltrimethoxysilane into a high-speed mixer, dry mix for 5 minutes at 800 rpm, place in a twin-screw reactor, heat to 190℃, granulate and dry to obtain surface TPU particles. S2: Add 100g of modified polybutylene adipate diol to a mixer, heat to 160℃, mix for 2 minutes at 30 rpm, add 5.5g of sodium dimyristoyl phosphate and 1.8g of nano zinc oxide, mix for 8 minutes at 60 rpm, transfer to a two-roll mill with a roll gap of 0.4-0.6mm, pass through 5 times, produce a 2mm sheet, air cool at 50℃ to obtain the adhesive layer sheet; S3: Add 100g of surface TPU particles to a single-screw extruder, heat to 180℃, and set the screw speed to 40rpm. Add 100g of adhesive layer sheet to the single-screw extruder, heat to 170℃, and set the screw speed to 32rpm. Then, add 425g of modified polytetrahydrofuran glycol to a twin-screw extruder, heat to 200℃, and set the screw speed to 28rpm. Add 4.8g of polyether-modified siloxane and 2.3g of antioxidant. Add 46g of microcapsules to the side feeder. The shear rate is 1300s. -1 Mix for 25 seconds, then add 4.6g of maleic anhydride, 2.3g of polyethylene octene polymer and 1.3g of initiator dicumyl peroxide. Cool to 160℃, extrude to a thickness of 0.045-0.055mm, and cure by electron beam layering to obtain automotive color-changing film.

[0036] Example 18: A method for preparing a polymer TPU automotive color-changing film S1: Add 100g of aliphatic polyether TPU, 7g of perfluorinated polyether glycol and 5g of aminoethylaminopropyltrimethoxysilane into a high-speed mixer, dry mix for 7 minutes at 700 rpm, place in a twin-screw reactor, heat to 200℃, granulate and dry to obtain surface TPU particles. S2: Add 100g of modified polybutylene adipate diol to a mixer, heat to 150℃, mix for 3 minutes at 20 rpm, add sodium dimyroyl phosphate and nano zinc oxide, mix for 10 minutes at 50 rpm, transfer to a two-roll mill with a roll gap of 0.4-0.6mm, pass through 6 times, produce a 2mm sheet, air cool at 40℃ to obtain the adhesive layer sheet; S3: Add 100g of surface TPU particles to a single-screw extruder, heat to 210℃, and set the screw speed to 35rpm. Add 110g of adhesive layer sheet to the single-screw extruder, heat to 165℃, and set the screw speed to 35rpm. Then, add 430g of modified polytetrahydrofuran glycol to a twin-screw extruder, heat to 180℃, and set the screw speed to 30rpm. Add 5g of polyether-modified siloxane and 2.4g of antioxidant. Add 48g of microcapsules to the side feeder. The shear rate is 1400s. -1Mix for 20 seconds, then add 4.8g of maleic anhydride, 2.4g of polyethylene octene polymer and 1.4g of initiator dicumyl peroxide. Cool to 170℃, extrude to a thickness of 0.045-0.055mm, and cure by electron beam layering to obtain automotive color-changing film.

[0037] Comparative Example 1: Compared with Example 13, this comparative example did not add microcapsules during the preparation of the polymer TPU automotive color change film. Only the modified polytetrahydrofuran diol, polyether-modified siloxane, and antioxidant were retained. The remaining steps and parameters were the same, and will not be repeated in this comparative example. The final automotive color change film was obtained.

[0038] Comparative Example 2: Compared with Example 13, this comparative example only replaces "zinc oxide nanoparticles" with "calcium carbonate powder". All other steps and parameters are the same, and will not be repeated here. The final product is a car color change film.

[0039] Comparative Example 3: Compared with Example 13, this comparative example eliminates the layered temperature control in the preparation process of polymer TPU automotive color change film. The three layers of materials are co-extruded uniformly at 200°C. The microcapsules, surface layer and adhesive layer are added to the main feed at the same time. The remaining steps and parameters are the same. This comparative example will not be repeated. Finally, the automotive color change film is obtained.

[0040] Comparative Example 4: Compared with Example 13, this comparative example only replaces "electron beam curing" with "120°C hot air curing for 20 minutes". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a car color change film is obtained.

[0041] Performance testing: Weather resistance test: In accordance with the ISO 4892-3 testing standard, a xenon lamp aging chamber and a colorimeter were used. Take the automotive color-changing films from Examples 13-15 and Comparative Examples 1-4 respectively, and cut them into 150mm × 70mm pieces with a xenon lamp irradiance of 0.51W / m². 2 The blackboard temperature was 65±5℃, the relative humidity was 50±5%, the water spraying cycle was 18 min / 102 min, the test duration was 500h, and the color difference (ΔE) and yellowing index (YI) were recorded after 500h of light exposure. Table 1 Weather resistance test results of the examples and comparative examples Self-healing performance test: A scratch tester was used in accordance with ASTM D7027 testing standards. 1. Take the car color change film of Examples 13-15 and Comparative Examples 1-4 respectively, cut it into 100mm×100mm, set a scratch with a depth of 50μm and a length of 100mm on its surface, and place it under natural light at a temperature of 25±5℃ for 24h. 2. Formula for calculating the repair rate: 00% Table 2. Self-healing performance test results of the examples and comparative examples Bond strength test: The universal testing machine was used in accordance with the GB / T 2792 testing standard. 1. Take the automotive color-changing films of Examples 13-15 and Comparative Examples 1-4 respectively, cut them into strips 25mm wide, place them on a universal testing machine, peel angle 180°, tensile speed 300 mm / min, test environment 25℃, and record the initial strength. 2. Place the sample in a xenon aging chamber, heat it to 80°C, leave it for 7 days, and then test its strength again.

[0042] 3. Retention rate calculation formula: 00% Table 3. Bond strength test results of the examples and comparative examples Antibacterial test: According to the ISO 22196 testing standard, the bacterial strains were Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538). Take the automotive color-changing films from Examples 13-15 and Comparative Examples 1-4 respectively, cut them into 100mm × 100mm pieces, and dilute 1mL of bacterial solution to 1×10⁻⁶. 5 CFU / mL, contact time 24h, temperature 37℃.

[0043] Table 4. Bond strength test results of the examples and comparative examples Data Analysis: As can be seen from Tables 1-4, the polymer TPU automotive color-changing film prepared by this invention has superior weather resistance, outstanding self-healing function, enhanced adhesion stability, and excellent antibacterial properties. In contrast, Comparative Example 1, due to the absence of microcapsules, experienced a sharp drop in its self-repair rate to 10% and a significant decrease in weather resistance. This was because the lack of microcapsules rendered the scratch repair mechanism ineffective, and the protective function of the intermediate layer was weakened, making it unable to resist photoaging. In Comparative Example 2, the adhesive strength retention rate was only 72.4% and the antibacterial rate dropped to 55.4% due to the substitution of zinc oxide with calcium carbonate. This was because calcium carbonate lacked nano-effects and photocatalytic activity, which weakened mechanical anchoring and antibacterial functions, and its poor dispersibility caused interface defects. Comparative Example 3 suffered severe deterioration in weather resistance due to the elimination of layered temperature control and high-temperature co-extrusion, with a self-repair rate of only 20%. This was because the 200°C high temperature damaged the microcapsule structure and the activity of the light stabilizer, while also causing thermal degradation of the components, resulting in the failure of the protective and repair functions. Comparative Example 4 showed that the adhesive strength retention rate dropped to 77.3% and the self-healing rate was only 30% due to the replacement of electron beam curing with thermosetting. This was because thermosetting at 120℃ caused thermal degradation, weakened the cross-linking network, damaged the microcapsule response activity, and reduced the interface stability. In summary, this invention comprehensively solves the problems of poor weather resistance, single function, adhesion failure and processing damage of traditional color-changing films through a three-layer functional design, layered temperature-controlled co-extrusion process and electron beam curing technology. Furthermore, the microcapsule three-step preparation method ensures the integrity of the capsule wall, realizes ultraviolet-triggered repair, simultaneous enhancement of adhesion strength and antibacterial properties by zinc oxide nanoparticles, and the layered process maximizes the preservation of the activity of functional components.

[0044] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0045] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A polymer TPU automotive color-changing film, comprising a surface layer, an intermediate layer, and an adhesive layer, characterized in that, The surface layer is composed of the following components in parts by weight: 85-90 parts aliphatic polyether TPU, 5-8 parts perfluoropolyether glycol, 3-5 parts aminosilane coupling agent, 0.5-1 part ultraviolet absorber, 0.3-0.5 parts hindered amine light stabilizer, and 0.2-0.5 parts lubricant. The intermediate layer is composed of the following components in parts by weight: 90-92 parts of modified polytetrahydrofuran diol 1000, 8-10 parts of microcapsules, 0.5-1 part of polyether-modified siloxane, and 0.3-0.5 parts of antioxidant. The adhesive layer is composed of the following components in parts by weight: 88-90 parts of modified polybutylene adipate diol, 4-6 parts of sodium dimyristoyl phosphate, 1-2 parts of zinc oxide nanoparticles, 3-5 parts of hydrogenated rosin glycerol ester, and 0.5-1 parts of nano silica.

2. The TPU automotive color-changing film according to claim 1, characterized in that, The preparation steps of the aliphatic polyether type TPU are as follows: Under a nitrogen atmosphere, polytetrahydrofuran diol 2000 was added to a flask, heated to 80-90℃, and hexamethylene diisocyanate and dibutyltin dilaurate catalyst were added. The reaction was carried out for 80-100 minutes until the reaction was complete. The temperature was then lowered to 65-75℃, and 1,4-butanediol was added. The mixture was placed in a high-shear mixing head and mixed for 3-5 seconds. The mixture was then injected into a twin-screw extruder, and antioxidant 1135, UV absorber UV-384, light stabilizer 292, and silicone masterbatch were added. The temperature was raised to 150-160℃, granulated, and dried to obtain aliphatic polyether type TPU.

3. The TPU automotive color-changing film according to claim 2, characterized in that, The mass ratio of polytetrahydrofuran diol 2000, hexamethylene diisocyanate, 1,4-butanediol, catalyst, antioxidant 1135, ultraviolet absorber UV-384, light stabilizer 292 to silicone masterbatch is 1:0.32-0.33:0.09-0.1:0.0002-0.0004:0.007-0.009:0.004-0.006:0.002-0.004:0.001-0.

003.

4. The TPU automotive color-changing film according to claim 1, characterized in that, The preparation steps of the modified polytetrahydrofuran diol 1000 are as follows: Under a nitrogen atmosphere, polytetrahydrofurandiol 1000 was added to a flask, heated to 80-90°C, and hexamethylene diisocyanate and dibutyltin dilaurate catalyst were added. The reaction was carried out for 80-100 minutes until the reaction was complete. The temperature was then lowered to 65-75°C, and 1,4-butanediol was added. The mixture was placed in a high-shear mixer head and mixed for 20-40 seconds. The mixture was then injected into a twin-screw extruder, heated to 90-110°C, and antioxidant 1076 and light stabilizer 622 were added. The temperature was then raised to 150-160°C, granulated, and dried to obtain modified polytetrahydrofurandiol 1000.

5. A polymer TPU automotive color-changing film according to claim 4, characterized in that, The mass ratio of polytetrahydrofuran diol 1000, hexamethylene diisocyanate, 1,4-butanediol, catalyst, antioxidant 1076 and light stabilizer 622 is 1:0.36-0.37:0.045-0.055:0.0001-0.0003:0.0014-0.0016:0.0002-0.0004.

6. The TPU automotive color-changing film according to claim 1, characterized in that, The microcapsule preparation steps are as follows: Step A1: Add indoline spiropyran to toluene solvent, heat to 40-60℃, stir for 20-40 min to obtain core material solution; Step A2: Under a nitrogen atmosphere, toluene diisocyanate is added to trimethylolpropane, the temperature is raised to 50-70℃, the reaction is carried out for 1-3 hours, the temperature is lowered to 30-40℃, the core material solution is added, and the mixture is stirred for 10-12 minutes to obtain an oil phase solution. Step A3: Add polyvinyl alcohol to deionized water, heat to 50-70℃, stir for 50-70 min, cool to 10-20℃, add oil phase solution, place in a high-speed disperser, speed 7000-9000 rpm, emulsify for 4-6 min, then heat to 30-40℃, add chain extender ethylenediamine, react for 3-5 h, add 5% sodium hydroxide solution, adjust pH to 8.5-9.0, distill under reduced pressure, add isophorone diisocyanate, heat to 40-50℃, react for 1-3 h, centrifuge, wash, dry and sieve to obtain microcapsules.

7. The TPU automotive color-changing film according to claim 6, characterized in that, The mass ratio of toluene diisocyanate, trimethylolpropane, and the core material solution in step A2 is 0.48-0.52:0.48-0.52:

1. The mass ratio of polyvinyl alcohol, deionized water, oil phase solution, chain extender and isophorone diisocyanate in step A3 is 0.32-0.34: 16.5-16.7: 1: 0.04-0.06: 0.082-0.

084.

8. The TPU automotive color-changing film according to claim 1, characterized in that, The preparation steps of the modified polybutylene adipate diol are as follows: Step B1: Under a nitrogen atmosphere, polybutylene adipate diol is added to a flask, heated to 80-90℃, 4,4'-diphenylmethane diisocyanate is added, and the reaction is carried out for 80-100 min. After the reaction is completed, the temperature is lowered to 65-75℃, and a 40% N-methylpyrrolidone solution of dimethylolpropionic acid is added. The reaction is carried out for 2-4 h to obtain the prepolymer. Step B2: Add the prepolymer to a flask, heat to 40-60℃, add triethylamine, stir for 8-12 minutes, adjust the pH to 7.5-8.0, add 1,4-butanediol and ethylene glycol, place in a high-shear emulsifier, emulsify for 50-70 seconds to obtain an emulsion; Step B3: Add the emulsion to deionized water, heat to 30-50℃, add ethylenediamine and nano zinc oxide, stir for 8-10 minutes, filter, wash, dry, place in a twin-screw extruder, add antioxidant, UV stabilizer and nano silica, heat to 170-190℃, granulate, and obtain modified polybutylene adipate diol. The mass ratio of the polybutylene adipate diol, 4,4'-diphenylmethane diisocyanate, and N-methylpyrrolidone solution of dimethylolpropionic acid is 1:0.33-0.34:0.1-0.11; The mass ratio of the prepolymer, triethylamine, 1,4-butanediol, and ethylene glycol is 1:0.02-0.022:0.06-0.062:0.01-0.011; The mass ratio of the emulsion, ethylenediamine, nano zinc oxide, antioxidant, UV stabilizer and nano silica is 1:0.0031-0.0033:0.01-0.012:0.003-0.005:0.001-0.003:0.0032-0.0034.

9. The TPU automotive color-changing film according to claim 1, characterized in that, The preparation steps of the polyether-modified siloxane are as follows: Under a nitrogen atmosphere, hydrogen-containing silicone oil and allyl polyether are added to isopropanol, heated to 80-90℃, sodium acetate and platinum catalyst are added, the reaction is carried out for 3-5 hours, the temperature is lowered to 50-70℃, activated clay is added, the mixture is stirred for 50-70 minutes, filtered and washed, and distilled under reduced pressure to obtain polyether-modified siloxane. The mass ratio of the hydrogen-containing silicone oil, allyl polyether, isopropanol, sodium acetate, platinum catalyst, and activated clay is 1:1.7-1.9:0.4-0.6:0.0008-0.0012:0.0004-0.0006:0.04-0.

06.

10. A method for preparing a polymeric TPU automotive color-changing film according to any one of claims 1-9, characterized in that, The preparation steps are as follows: Step S1: Add aliphatic polyether TPU, perfluoropolyether glycol and aminoethylaminopropyltrimethoxysilane into a high-speed mixer, dry mix for 3-7 minutes at a speed of 700-900 rpm, place in a twin-screw reactor, heat to 180-200℃, granulate and dry to obtain surface TPU particles. Step S2: Add the modified polybutylene adipate diol to the internal mixer, heat to 150-170℃, mix for 1-3 minutes at 20-40 rpm, add sodium dimyroyl phosphate and nano zinc oxide, mix for 6-10 minutes at 50-70 rpm, transfer to a two-roll mill with a roll gap of 0.4-0.6 mm, pass through a thin mill 4-6 times, and produce a 2 mm sheet. Air cool at 40-60℃ to obtain the adhesive layer sheet. Step S3: Add the surface TPU particles to a single-screw extruder, heat to 180-210℃, and screw speed 35-40 rpm. Add the adhesive layer sheet to the single-screw extruder, heat to 165-185℃, and screw speed 30-35 rpm. Then, add the modified polytetrahydrofuran diol to a twin-screw extruder, heat to 180-220℃, and screw speed 25-30 rpm. Add the polyether-modified siloxane and antioxidant. Add the microcapsules via a side feeder. The shear rate is 1200-1400 s. -1 Mix for 20-30 seconds, then add maleic anhydride, polyethylene octene polymer and initiator dicumyl peroxide, cool to 150-170℃, extrude to a thickness of 0.045-0.055mm, and cure by electron beam layering to obtain automotive color-changing film. The mass ratio of the aliphatic polyether TPU, perfluoropolyether glycol, and aminoethylaminopropyltrimethoxysilane is 1:0.065-0.07:0.04-0.

05. The mass ratio of the modified polybutylene adipate diol, sodium dimyristoyl phosphate, and nano zinc oxide is 1:0.05-0.06:0.015-0.

02. The mass ratio of the surface TPU particles, adhesive sheet, modified polytetrahydrofuran diol, polyether-modified siloxane, antioxidant, microcapsules, maleic anhydride, polyvinyl octene polymer, and initiator dicumyl peroxide is 1:0.9-1.1:4.2-4.3:0.045-0.05:0.022-0.024:0.44-0.48:0.044-0.048:0.022-0.024:0.012-0.014.

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