Heat insulation type color changing film for vehicle and preparation method of heat insulation type color changing film

Abstract

The invention relates to the technical field of color alteration films, in particular to a heat insulation type vehicle color alteration film and a preparation method thereof.The heat insulation type vehicle color alteration film is prepared from, by mass, 60-65 parts of modified thermoplastic polyurethane basic solution, 30-35 parts of modified hollow glass beads, 8-12 parts of modified polyurethane surface coating liquid and the like; compared with the prior art, by innovatively combining the specific functional filler, the customized and synthesized light stable component and the optimized matrix resin system, the comprehensive performance of the membrane material is remarkably improved: on one hand, an excellent heat insulation effect is realized, and the temperature in a vehicle is effectively reduced; on the other hand, long-term weather resistance and ultraviolet aging resistance of the material are ensured; meanwhile, good mechanical strength and adhesive force are achieved, and the automotive requirements are met; the preparation technology is reasonable in parameter design, large-scale production is facilitated, and the product is suitable for various automobile appearance color changing and protection requirements and has wide market application prospects.

Description

Technical Field

[0001] This invention relates to the field of color-changing film technology, and in particular to a heat-insulating automotive color-changing film and its preparation method. Background Technology

[0002] As a high-polymer functional film covering the exterior surface of a car, the core value of automotive color-changing film lies in achieving the dual functions of exterior color change and paint protection; while the "heat insulation" characteristic requires the material to have the ability to block heat conduction by reflecting or scattering infrared radiation, so as to solve the drawback of the temperature rise inside the car caused by the metal body easily absorbing heat, and improve the riding experience.

[0003] In existing technologies, magnetron sputtering of metal films is often used to improve thermal insulation, but the application of such materials is not universal and can only provide a silver surface effect. More importantly, the traditional ultraviolet absorber UV-329 exists in the matrix in the form of physical doping. After long-term use, it is easy to migrate and precipitate, causing severe yellowing of the film layer and an actual service life of less than 3 years. In addition, polyvinyl chloride materials are prone to embrittlement and breakage at low temperatures, while thermoplastic polyurethane-based products are difficult to resist scratches from sand and gravel due to insufficient surface hardness. Moreover, at the process level, high-filling thermal insulation fillers cause a sharp increase in system viscosity, resulting in leveling defects and drying bubbles during coating.

[0004] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a heat-insulating 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 heat-insulating automotive color-changing film and its preparation method, so as to solve the problems of low heat insulation efficiency, poor weather resistance and weak mechanical strength in the prior art.

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

[0007] A heat-insulating automotive color-changing film is composed of the following components in parts by weight: 60-65 parts of modified thermoplastic polyurethane base solution, 30-35 parts of modified hollow glass microspheres, 8-12 parts of modified polyurethane topcoat liquid, 0.1-0.3 parts of leveling agent, and 0-0.1 parts of defoamer.

[0008] Preferably, the preparation steps of the modified thermoplastic polyurethane base solution are as follows: Step A1: Add polytetrahydrofuran ether glycol and perfluoropolyether glycol to a reaction vessel, heat to 100-120℃, dehydrate under vacuum for 1-3 hours, and the reaction is complete to obtain a mixture; Step A2: Under a nitrogen atmosphere, isophorone diisocyanate and the catalyst dibutyltin dilaurate are added to the mixture, the temperature is raised to 55-65℃, and the reaction is carried out for 2-4 hours. Then, 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone and the chain extender polyetheramine D2000 are added, the temperature is raised to 70-80℃, and the reaction is carried out for 1-3 hours. Ethanol is added, and the reaction is completed. The temperature is lowered to 40-50℃, and a mixed solvent of butanone and N,N-dimethylacetamide is added. The mixture is stirred for 50-70 minutes to obtain a modified thermoplastic polyurethane solution. By modifying the thermoplastic polyurethane matrix and introducing perfluoropolyether segments and reactive UV absorbers, flexibility, abrasion resistance and chemical stability are improved.

[0009] Preferably, the mass ratio of polytetrahydrofuran ether diol to perfluoropolyether diol in step A1 is 1:0.18-0.22; The mass ratio of the mixture, isophorone diisocyanate, 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone, chain extender, catalyst, ethanol, and mixed solvent in step A2 is 1:0.24-0.26:0.062-0.063:0.1-0.11:0.0008-0.0012:0.02-0.021:7.2-7.3; The mass ratio of butanone to N,N-dimethylacetamide in step A2 is 3:2.

[0010] Preferably, the preparation steps of the 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone are as follows: Step B1: Under a nitrogen atmosphere, 2,4-dihydroxybenzophenone and anhydrous potassium carbonate were added to acetone solvent, heated to 50-60℃, stirred for 20-40 min, 3-chloropropanol was added, the temperature was raised to 60-70℃, and the reaction was refluxed for 7-9 h. After the reaction was completed, the mixture was cooled, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-chloropropoxy)benzophenone. Step B2: Under a nitrogen atmosphere, 2-hydroxy-4-(3-chloropropoxy)benzophenone, methacrylic acid, p-toluenesulfonic acid and 4-methoxyphenol are added to toluene solvent, heated to 110-120℃, stirred and refluxed for 5-7 hours. After the reaction is complete, the temperature is lowered to 50-60℃, washed and dried, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone. 2-Hydroxy-4-(3-methacryloyloxypropoxy)benzophenone contains a methacryloyl group in its molecule, which can participate in the polymerization reaction and thus be firmly bonded to the polyurethane chain. In addition, it can combine with the light stabilizer added to the surface coating liquid to form a dual protection system, which can effectively delay the aging, yellowing and fading of the film material caused by ultraviolet radiation.

[0011] Preferably, the mass ratio of 2,4-dihydroxybenzophenone, anhydrous potassium carbonate and 3-chloropropanol in step B1 is 1:1.2-1.4:0.6-0.7; The mass ratio of 2-hydroxy-4-(3-chloropropoxy)benzophenone, methacrylic acid, p-toluenesulfonic acid and 4-methoxyphenol in step B2 is 1:0.61-0.63:0.02-0.024:0.0025-0.003.

[0012] Preferably, the modified hollow glass microspheres are prepared using the following steps: Add silane coupling agent KH-560 to a mixture of ethanol and deionized water, add acetic acid, adjust the pH to 4.5-5.5, hydrolyze for 20-40 min, add hollow glass microspheres, heat to 50-70℃, stir for 2-4 h, filter, and dry to obtain modified hollow glass microspheres. Hollow glass microspheres have a hollow internal structure, which can effectively block heat transfer. At the same time, the surface of the microspheres is modified with silane coupling agent, which enhances the interfacial bonding force with the polyurethane matrix and significantly improves the film material's ability to reflect and scatter heat radiation, thereby reducing the temperature inside the vehicle.

[0013] Preferably, the mass ratio of the silane coupling agent KH-560 to the hollow glass microspheres is 1:33.2-33.4; The volume ratio of ethanol to deionized water is 19:1.

[0014] Preferably, the preparation steps of the modified polyurethane surface coating liquid are as follows: Step C1: Add nano-silica to ethyl acetate solvent, heat to 30-40℃, disperse for 20-30 min, rotate at 1500-2500 rpm, add silane coupling agent KH-570, heat to 50-70℃, stir for 1-3 h to obtain silanized silica dispersion; Step C2: Add polyurethane acrylate and 1,6-hexanediol diacrylate to the silanized silica dispersion, heat to 30-50℃, stir for 30-50 min, add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, light stabilizer, defoamer and leveling agent, transfer to a three-roll mill, circulate and grind, add butyl acetate, adjust the viscosity to 1100-1300 mPa·s, filter to obtain modified polyurethane surface coating liquid; Nano-silica in polyurethane surface coating liquid is surface-treated with silane coupling agent, forming a strong interfacial bond with polyurethane acrylate, which enhances the coating hardness, scratch resistance and adhesion to the substrate.

[0015] The mass ratio of the nano-silica to the silane coupling agent KH-570 is 1:0.02-0.04; The mass ratio of the polyurethane acrylate, 1,6-hexanediol diacrylate, silanized silica dispersion, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, light stabilizer, defoamer, and leveling agent is 1:0.4-0.44:0.16-0.18:0.04-0.06:0.01-0.03:0.004-0.006:0.007-0.009.

[0016] A method for preparing a heat-insulating automotive color-changing film, comprising the following steps: Step S1: Add the modified hollow glass microspheres to the modified thermoplastic polyurethane base solution, heat to 30-50℃, stir for 20-40 minutes at a speed of 150-250 rpm, add to a three-roll mill with a roller speed ratio of 1:2:5, add defoamer and leveling agent, stir for 15-25 minutes to obtain slurry; Step S2: Place the silicone release film on the coating machine's feed roller and process it online using a corona treatment machine with a power density of 50W / m³. 2 The conveying speed is 10m / min, and the process is carried out once per batch. The slurry is added to the liquid tank of the coating machine, the film thickness is controlled at 250μm, the temperature is raised to 48-52℃, and the film is dried for 4-6min. The temperature is raised to 58-62℃, and the film is dried for 7-9min. The temperature is raised to 68-72℃, and the film is dried for 8-12min. The modified polyurethane surface coating liquid is then added to the liquid tank of the coating machine for coating. The temperature is raised to 70-90℃, and the film is dried for 4-6min. The film is then cured under a UV lamp, cooled, and allowed to stand for curing to obtain the automotive color-changing film. Staged drying avoids bubble formation and ensures uniform film layer. At the same time, UV curing combined with thermal curing can improve crosslinking efficiency. In addition, raw material ratio, roller speed, corona treatment parameters, etc. are all quantitatively controlled to ensure product consistency and production efficiency, making it suitable for industrial applications.

[0017] Preferably, the mass ratio of the modified hollow glass microspheres, modified thermoplastic polyurethane solution, defoamer and leveling agent in step S1 is 1:1.6-1.8:0.0028-0.003:0.0055-0.0058; In step S2, the mass ratio of the silicone release film, slurry, and modified polyurethane surface coating liquid is 1:4.5-4.9:0.54-0.58.

[0018] The beneficial effects of this invention are: This invention provides a heat-insulating automotive color-changing film and its preparation method. By innovatively combining specific functional fillers, custom-synthesized light-stabilizing components, and an optimized matrix resin system, this invention significantly improves the overall performance of the film material compared to existing technologies. On the one hand, it achieves excellent heat insulation, effectively reducing the temperature inside the vehicle; on the other hand, it ensures the material's long-term weather resistance and resists ultraviolet aging; simultaneously, it possesses good mechanical strength and adhesion, meeting automotive requirements. Its manufacturing process parameters are rationally designed, facilitating large-scale production. This product is suitable for various automotive exterior color-changing and protection needs, and has broad market application prospects. Detailed Implementation

[0019] 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.

[0020] Example 1: The preparation steps of 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone are as follows: S1: Under a nitrogen atmosphere, 100g of 2,4-dihydroxybenzophenone and 120g of anhydrous potassium carbonate were added to 500mL of acetone solvent, heated to 50℃, stirred for 40min, 60g of 3-chloropropanol were added, the temperature was raised to 60℃, and the reaction was refluxed for 9h. After the reaction was completed, the temperature was lowered and cooled, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-chloropropoxy)benzophenone. S2: Under a nitrogen atmosphere, 100g of 2-hydroxy-4-(3-chloropropoxy)benzophenone, 61g of methacrylic acid, 2g of p-toluenesulfonic acid and 0.25g of 4-methoxyphenol were added to 200mL of toluene solvent, heated to 110℃, stirred and refluxed for 7h, and after the reaction was completed, cooled to 50℃, washed and dried, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone.

[0021] Example 2: The preparation steps of 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone are as follows: S1: Under a nitrogen atmosphere, 100g of 2,4-dihydroxybenzophenone and 130g of anhydrous potassium carbonate were added to 500mL of acetone solvent, heated to 55℃, stirred for 30min, 65g of 3-chloropropanol were added, the temperature was raised to 65℃, and the reaction was refluxed for 8h. After the reaction was completed, the mixture was cooled, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-chloropropoxy)benzophenone. S2: Under a nitrogen atmosphere, 100g of 2-hydroxy-4-(3-chloropropoxy)benzophenone, 62g of methacrylic acid, 2.2g of p-toluenesulfonic acid and 0.28g of 4-methoxyphenol were added to 200mL of toluene solvent. The mixture was heated to 115℃ and stirred under reflux for 6h. After the reaction was completed, the mixture was cooled to 55℃, washed and dried, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone.

[0022] Example 3: The preparation steps of 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone are as follows: S1: Under a nitrogen atmosphere, 100g of 2,4-dihydroxybenzophenone and 140g of anhydrous potassium carbonate were added to 500mL of acetone solvent, heated to 60℃, stirred for 20min, 70g of 3-chloropropanol were added, the temperature was raised to 70℃, and the reaction was refluxed for 9h. After the reaction was completed, the temperature was lowered and cooled, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-chloropropoxy)benzophenone. S2: Under a nitrogen atmosphere, 100g of 2-hydroxy-4-(3-chloropropoxy)benzophenone, 63g of methacrylic acid, 2.4g of p-toluenesulfonic acid and 0.3g of 4-methoxyphenol were added to 200mL of toluene solvent. The mixture was heated to 120℃ and stirred under reflux for 5h. After the reaction was completed, the mixture was cooled to 60℃, washed and dried, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone.

[0023] Example 4: The preparation steps of the modified thermoplastic polyurethane base solution are as follows: S1: Add 100g of polytetrahydrofuran ether glycol and 18g of perfluoropolyether glycol to a reaction vessel, heat to 100℃, dehydrate under vacuum for 3 hours, and the reaction is complete to obtain a mixture; S2: Under a nitrogen atmosphere, 24g of isophorone diisocyanate and 0.08g of catalyst dibutyltin dilaurate were added to 100g of a mixture, heated to 55℃, and reacted for 4h. Then, 6.2g of 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone and 10g of chain extender polyetheramine D2000 were added, heated to 70℃, and reacted for 3h. 2g of ethanol was added, and the reaction was completed. The temperature was lowered to 40℃, and 432g of butanone and 288g of N,N-dimethylacetamide mixed solvent were added. The mixture was stirred for 70min to obtain a modified thermoplastic polyurethane base solution.

[0024] Example 5: The preparation steps of the modified thermoplastic polyurethane base solution are as follows: S1: Add 100g of polytetrahydrofuran ether glycol and 20g of perfluoropolyether glycol to a reaction vessel, heat to 110℃, dehydrate under vacuum for 2 hours, and the reaction is complete to obtain a mixture. S2: Under a nitrogen atmosphere, 25g of isophorone diisocyanate and 0.1g of catalyst dibutyltin dilaurate were added to 100g of a mixture, heated to 60℃, and reacted for 3h. Then, 6.25g of 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone and 10.5g of chain extender polyetheramine D2000 were added, heated to 75℃, and reacted for 2h. 2.5g of ethanol was added, and the reaction was completed. The temperature was lowered to 45℃, and 435g of butanone and 290g of N,N-dimethylacetamide mixed solvent were added. The mixture was stirred for 60min to obtain a modified thermoplastic polyurethane base solution.

[0025] Example 6: The preparation steps of the modified thermoplastic polyurethane base solution are as follows: S1: Add 100g of polytetrahydrofuran ether glycol and 22g of perfluoropolyether glycol to a reaction vessel, heat to 120℃, dehydrate under vacuum for 3 hours, and the reaction is complete to obtain a mixture; S2: Under a nitrogen atmosphere, 26g of isophorone diisocyanate and 0.12g of catalyst dibutyltin dilaurate were added to 100g of a mixture, heated to 65℃, and reacted for 2h. Then, 6.3g of 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone and 11g of chain extender polyetheramine D2000 were added, heated to 80℃, and reacted for 1h. 2.1g of ethanol was added, and the reaction was completed. The temperature was lowered to 50℃, and 438g of butanone and 292g of N,N-dimethylacetamide mixed solvent were added. The mixture was stirred for 50min to obtain a modified thermoplastic polyurethane base solution.

[0026] Example 7: The preparation steps of the modified hollow glass microspheres are as follows: Add 10g of silane coupling agent KH-560 to a mixture of 380mL ethanol and 20mL deionized water, add acetic acid, adjust the pH to 4.5-5.5, hydrolyze for 20min, add 332g of hollow glass microspheres, heat to 70℃, stir for 2h, filter, and dry to obtain modified hollow glass microspheres.

[0027] Example 8: The preparation steps of the modified hollow glass microspheres are as follows: Add 10g of silane coupling agent KH-560 to a mixture of 380mL ethanol and 20mL deionized water, add acetic acid, adjust the pH to 4.5-5.5, hydrolyze for 30min, add 333g of hollow glass microspheres, heat to 60℃, stir for 3h, filter, and dry to obtain modified hollow glass microspheres.

[0028] Example 9: The preparation steps of the modified hollow glass microspheres are as follows: Add 10g of silane coupling agent KH-560 to a mixture of 380mL ethanol and 20mL deionized water, add acetic acid, adjust the pH to 4.5-5.5, hydrolyze for 40min, add 334g of hollow glass microspheres, heat to 50℃, stir for 4h, filter, and dry to obtain modified hollow glass microspheres.

[0029] Example 10: The preparation steps of the modified polyurethane surface coating liquid are as follows: S1: Add 100g of nano silica to 200mL of ethyl acetate solvent, heat to 30℃, disperse for 30min, rotate at 1500rpm, add 2g of silane coupling agent KH-570, heat to 70℃, stir for 1h to obtain silanized silica dispersion. S2: Add 100g of polyurethane acrylate and 40g of 1,6-hexanediol diacrylate to 16g of silanized silica dispersion, heat to 30℃, stir for 50min, add 4g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1g of light stabilizer, 0.4g of defoamer BYK-054 and 0.7g of leveling agent TEGO-370, transfer to a three-roll mill, circulate and grind, add butyl acetate, adjust the viscosity to 1100-1300mPa·s, filter to obtain modified polyurethane surface coating liquid.

[0030] Example 11: The preparation steps of the modified polyurethane surface coating liquid are as follows: S1: Add 100g of nano silica to 200mL of ethyl acetate solvent, heat to 35℃, disperse for 25min, rotate at 2000rpm, add 3g of silane coupling agent KH-570, heat to 60℃, stir for 2h to obtain silanized silica dispersion. S2: Add 100g of polyurethane acrylate and 42g of 1,6-hexanediol diacrylate to 17g of silanized silica dispersion, heat to 40℃, stir for 40min, add 5g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2g of light stabilizer, 0.5g of defoamer BYK-067A and 0.8g of leveling agent BYK-3565, transfer to a three-roll mill, circulate and grind, add butyl acetate, adjust the viscosity to 1100-1300mPa·s, filter to obtain modified polyurethane surface coating liquid.

[0031] Example 12: The preparation steps of the modified polyurethane surface coating liquid are as follows: S1: Add 100g of nano silica to 200mL of ethyl acetate solvent, heat to 40℃, disperse for 20min, rotate at 2500rpm, add 4g of silane coupling agent KH-570, heat to 50℃, stir for 3h to obtain silanized silica dispersion. S2: Add 100g of polyurethane acrylate and 44g of 1,6-hexanediol diacrylate to 18g of silanized silica dispersion, heat to 50℃, stir for 30min, add 6g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 3g of light stabilizer, 0.6g of defoamer BYK-070 and 0.9g of leveling agent TEGO Rad 2300, transfer to a three-roll mill, circulate and grind, add butyl acetate, adjust the viscosity to 1100-1300mPa·s, filter to obtain modified polyurethane surface coating liquid.

[0032] Example 13: A method for preparing a heat-insulating automotive color-changing film S1: Add 100g of modified hollow glass microspheres to 160g of modified thermoplastic polyurethane base solution, heat to 30℃, stir for 40min at 150rpm, add to a three-roll mill with a roller speed ratio of 1:2:5, add 0.28g of defoamer TEGOAirex 900 and 0.55g of leveling agent BYK-345, stir for 25min to obtain slurry; S2: Place 10g of silicone release film on the coating machine's feed roller and process it online using a corona treatment machine with a power density of 50W / m³. 2 The conveying speed is 10m / min, and the process is carried out once. 45g of slurry is added to the coating machine liquid tank, the film thickness is controlled at 250μm, the temperature is raised to 48℃, dried for 6min, the temperature is raised to 58℃, dried for 9min, the temperature is raised to 68℃, dried for 12min, 5.4g of modified polyurethane surface coating liquid is added to the coating machine liquid tank for coating, the temperature is raised to 70℃, dried for 6min, cured by UV lamp, cooled, and allowed to stand for curing to obtain automotive color change film.

[0033] Example 14: A method for preparing a heat-insulating automotive color-changing film S1: Add 100g of modified hollow glass microspheres to 170g of modified thermoplastic polyurethane base solution, heat to 40℃, stir for 30min at 200rpm, add to a three-roll mill with a roller speed ratio of 1:2:5, add 0.29g of defoamer TEGO Glide 420 and 0.56g of leveling agent BYK-361N, stir for 20min to obtain slurry; S2: Place 10g of silicone release film on the coating machine's feed roller and process it online using a corona treatment machine with a power density of 50W / m³. 2The conveying speed is 10m / min, and the process is carried out once. 47g of slurry is added to the coating machine liquid tank, the film thickness is controlled at 250μm, the temperature is raised to 50℃, dried for 5min, the temperature is raised to 60℃, dried for 8min, the temperature is raised to 70℃, dried for 10min, 5.6g of modified polyurethane surface coating liquid is added to the coating machine liquid tank for coating, the temperature is raised to 80℃, dried for 5min, cured by UV lamp, cooled, and allowed to stand for curing to obtain automotive color change film.

[0034] Example 15: A method for preparing a heat-insulating automotive color-changing film S1: Add 100g of modified hollow glass microspheres to 180g of modified thermoplastic polyurethane base solution, heat to 50℃, stir for 20min at 250rpm, add to a three-roll mill with a roller speed ratio of 1:2:5, add defoamer TEGO GlideB1484 and leveling agent TEGO-432, stir for 15-25min to obtain slurry; S2: Place 10g of silicone release film on the coating machine's feed roller and process it online using a corona treatment machine with a power density of 50W / m³. 2 The conveying speed is 10m / min, and the process is carried out once. 49g of slurry is added to the coating machine tank, the film thickness is controlled at 250μm, the temperature is raised to 52℃ and dried for 4min, the temperature is raised to 62℃ and dried for 7min, the temperature is raised to 72℃ and dried for 8min, 5.8g of modified polyurethane surface coating liquid is added to the coating machine tank for coating, the temperature is raised to 90℃ and dried for 4min, cured by UV lamp, cooled and allowed to stand for curing, and the automotive color change film is obtained.

[0035] Comparative Example 1: Compared with Example 13, this comparative example did not add modified hollow glass microspheres in the preparation process of a heat-insulating automotive color-changing film. All other steps and parameters were the same, and will not be repeated in this comparative example. The final automotive color-changing film was obtained.

[0036] Comparative Example 2: Compared with Example 13, this comparative example only replaces "2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone" with "UV absorber UV-9". All other steps and parameters are the same, and will not be repeated here. The final product is a car color change film.

[0037] Comparative Example 3: Compared with Example 13, this comparative example did not add perfluoropolyether glycol in the preparation process of the modified thermoplastic polyurethane solution, but only used polytetrahydrofuran ether glycol. The remaining steps and parameters were the same, and will not be repeated in this comparative example. Finally, a color-changing film for automobiles was obtained.

[0038] Comparative Example 4: Compared with Example 13, this comparative example only replaces "modified polyurethane topcoat liquid" with "polyurethane topcoat liquid". 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.

[0039] Performance testing: Thermal insulation performance test: The ultraviolet-visible-near-infrared spectrophotometer was used in accordance with the GB / T 2680-2021 testing standard. 1. Cut the automotive color-changing films of Examples 13-15 and Comparative Examples 1-4 into 100mm×100mm samples, respectively, and attach them to a 2mm thick quartz glass substrate, ensuring that there are no bubbles or wrinkles. Place them in the sample chamber and scan the wavelength range of 300-2500nm. Repeat three times and take the average value of reflectance R(λ) and transmittance T(λ). 2. Direct solar reflectance (ρ) e ): ; Total solar transmittance (g): ; Insulation efficiency (η): ; E sol (λ): Standard solar radiation spectrum; λ: Wavelength (unit: nm); R(λ): The reflectivity of the sample at wavelength λ; T(λ): The transmittance of the sample at wavelength λ.

[0040] Table 1. Test results of thermal insulation performance of the examples and comparative examples (Note: Negative values ​​indicate excessively high transmittance) Weather resistance test: The ultraviolet aging test chamber was used in accordance with the GB / T 1865-2009 test standard. 1. Cut the car color-changing films of Examples 13-15 and Comparative Examples 1-4 into 150mm×70mm samples respectively, and attach them to the surface of a clean aluminum plate, ensuring that there are no bubbles or wrinkles. 2. Use a colorimeter to measure the initial colorimetric values ​​(L0, a0, b0) of the sample surface and record them according to the CIE LAB color space standard. Use a gloss meter to measure the initial gloss value G0 at an incident angle of 60°. 3. Fix the sample vertically on the sample rack in the aging chamber, ensuring that the light-receiving side faces the lamp tube. Ultraviolet irradiation phase: temperature 60±3℃, duration 8h, irradiation intensity 0.71W / m2; Condensation stage: temperature 50±3℃, relative humidity 100%, duration 4h; total test time is 2000h.

[0041] 4. Color difference (ΔE): ; 5. Gloss retention rate (%): .

[0042] Table 2 Weather resistance test results of the examples and comparative examples Mechanical performance testing: Adhesion: Tested according to GB / T 9286-2021 standard; Hardness: Refer to GB / T 6739-2022 test standard; Low temperature toughness: Referring to the GB / T 11185-2021 testing standard, a bending tester was used to cut the automotive color-changing films of Examples 13-15 and Comparative Examples 1-4 into 150mm×10mm samples, which were then attached to the surface of a polycarbonate sheet, ensuring no bubbles or wrinkles. The samples were placed in a constant temperature chamber at -20℃±2℃ for 24 hours, then removed and placed on the bending tester. The samples were bent 180° around a cylindrical shaft with a diameter of 10 mm at a uniform speed of 1 second. The damage was graded as follows: Grade A: no cracks, Grade B: crack length ≤1 mm (minor cracking), Grade C: crack length >1 mm or partial detachment.

[0043] Table 3 Mechanical property test results of the examples and comparative examples Data Analysis: As can be seen from Tables 1-3, the automotive color-changing film prepared by this invention has excellent heat insulation performance, long-lasting weather resistance, and excellent mechanical properties. In contrast, Comparative Example 1, lacking modified hollow glass microspheres, experienced a dramatic drop in heat insulation rate to -13.2%. This was because the hollow glass microspheres, being vacuum cavities, had low thermal conductivity and could reflect >85% of infrared radiation. After removal, the film lost its primary heat insulation medium, causing the total solar transmittance g to surge to 55.7%, allowing heat to directly penetrate the film. Simultaneously, its weather resistance decreased. This was because the microspheres, after being silanized with KH-560, formed -Si-O-Si- bonds, enhancing the interfacial bonding with the polyurethane matrix. Removal of these bonds resulted in uneven dispersion of the ultraviolet absorber and accelerated local aging. Furthermore, the microspheres, acting as a reinforcing phase, improved the film's density; their absence led to increased shrinkage stress in the matrix, weakening the adhesion to the substrate. Comparative Example 2 showed reduced weather resistance due to the replacement of the UV absorber with UV-9. This is because UV-9 is 2-hydroxy-4-methoxybenzophenone, a small-molecule physical dopant with poor compatibility with polyurethane. During damp heat aging, it migrates to the membrane surface through free volume channels, leading to the failure of UV protection inside the membrane, accelerated chain segment photo-oxidation, and the scattering of light by precipitated crystals, resulting in increased haze and decreased gloss. In contrast, 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone contains methacryloyl groups, which can form a permanent UV shielding network by copolymerizing and bonding to the polyurethane backbone. Comparative Example 3 showed deterioration in mechanical properties due to the addition of perfluoropolyether diol. This is because perfluoropolyether contains -CF2-O- flexible segments, which, after copolymerization with polytetrahydrofuran ether, can enhance molecular chain mobility and maintain elasticity at -20°C. Simultaneously, its fluorine-rich surface reduces interfacial energy and enhances adhesion. Furthermore, the CF bond vibration absorption peak of perfluoropolyether can scatter some mid-infrared thermal energy, and after removal, the reflectance ρ... e reduce; In Comparative Example 4, the hardness decreased because the modified polyurethane surface coating was replaced with the unmodified polyurethane surface coating. This was because in the modified surface coating, the SiO2 surface treated with KH-570 was grafted with methacryloyloxy groups, which covalently crosslinked with the polyurethane acrylate to form an organic-inorganic interpenetrating network. In contrast, Comparative Example 4 used a common surface coating, where SiO2 was only physically filled, leading to stress concentration at the interface and the initiation of microcracks, causing the hardness to drop from 2H to B grade.

[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 heat-insulating automotive color-changing film, characterized in that, It is composed of the following components in parts by weight: 60-65 parts modified thermoplastic polyurethane base solution, 30-35 parts modified hollow glass microspheres, 8-12 parts modified polyurethane topcoat liquid, 0.1-0.3 parts leveling agent, and 0-0.1 parts defoamer.

2. The heat-insulating automotive color-changing film according to claim 1, characterized in that, The modified thermoplastic polyurethane solution is prepared using the following steps: Step A1: Add polytetrahydrofuran ether glycol and perfluoropolyether glycol to a reaction vessel, heat to 100-120℃, dehydrate under vacuum for 1-3 hours, and the reaction is complete to obtain a mixture; Step A2: Under a nitrogen atmosphere, isophorone diisocyanate and the catalyst dibutyltin dilaurate are added to the mixture, heated to 55-65℃, and reacted for 2-4 hours. Then, 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone and the chain extender polyetheramine D2000 are added, heated to 70-80℃, and reacted for 1-3 hours. Ethanol is added, and the reaction is completed. The temperature is then lowered to 40-50℃, and a mixed solvent of butanone and N,N-dimethylacetamide is added. The mixture is stirred for 50-70 minutes to obtain a modified thermoplastic polyurethane base solution.

3. The heat-insulating automotive color-changing film according to claim 2, characterized in that, The mass ratio of polytetrahydrofuran ether diol to perfluoropolyether diol in step A1 is 1:0.18-0.22; The mass ratio of the mixture, isophorone diisocyanate, 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone, chain extender, catalyst, ethanol, and mixed solvent in step A2 is 1:0.24-0.26:0.062-0.063:0.1-0.11:0.0008-0.0012:0.02-0.021:7.2-7.3; The mass ratio of butanone to N,N-dimethylacetamide in step A2 is 3:

2.

4. The heat-insulating automotive color-changing film according to claim 2, characterized in that, The preparation steps for the 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone are as follows: Step B1: Under a nitrogen atmosphere, 2,4-dihydroxybenzophenone and anhydrous potassium carbonate were added to acetone solvent, heated to 50-60℃, stirred for 20-40 min, 3-chloropropanol was added, the temperature was raised to 60-70℃, and the reaction was refluxed for 7-9 h. After the reaction was completed, the mixture was cooled, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-chloropropoxy)benzophenone. Step B2: Under a nitrogen atmosphere, 2-hydroxy-4-(3-chloropropoxy)benzophenone, methacrylic acid, p-toluenesulfonic acid and 4-methoxyphenol are added to toluene solvent, heated to 110-120℃, stirred and refluxed for 5-7 hours. After the reaction is complete, the temperature is lowered to 50-60℃, washed and dried, filtered, and distilled under reduced pressure to obtain 2-hydroxy-4-(3-methacryloyloxypropoxy)benzophenone.

5. The heat-insulating automotive color-changing film according to claim 4, characterized in that, The mass ratio of 2,4-dihydroxybenzophenone, anhydrous potassium carbonate, and 3-chloropropanol in step B1 is 1:1.2-1.4:0.6-0.

7. The mass ratio of 2-hydroxy-4-(3-chloropropoxy)benzophenone, methacrylic acid, p-toluenesulfonic acid and 4-methoxyphenol in step B2 is 1:0.61-0.63:0.02-0.024:0.0025-0.

003.

6. The heat-insulating automotive color-changing film according to claim 1, characterized in that, The modified hollow glass microspheres are prepared in the following steps: Add silane coupling agent KH-560 to a mixture of ethanol and deionized water, add acetic acid, adjust the pH to 4.5-5.5, hydrolyze for 20-40 minutes, add hollow glass microspheres, heat to 50-70℃, stir for 2-4 hours, filter, and dry to obtain modified hollow glass microspheres.

7. The heat-insulating automotive color-changing film according to claim 6, characterized in that, The mass ratio of the silane coupling agent KH-560 to the hollow glass microspheres is 1:33.2-33.4; The volume ratio of ethanol to deionized water is 19:

1.

8. The heat-insulating automotive color-changing film according to claim 1, characterized in that, The preparation steps of the modified polyurethane surface coating liquid are as follows: Step C1: Add nano-silica to ethyl acetate solvent, heat to 30-40℃, disperse for 20-30 min, rotate at 1500-2500 rpm, add silane coupling agent KH-570, heat to 50-70℃, stir for 1-3 h to obtain silanized silica dispersion; Step C2: Add polyurethane acrylate and 1,6-hexanediol diacrylate to the silanized silica dispersion, heat to 30-50℃, stir for 30-50 min, add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, light stabilizer, defoamer and leveling agent, transfer to a three-roll mill, circulate and grind, add butyl acetate, adjust the viscosity to 1100-1300 mPa·s, filter to obtain modified polyurethane surface coating liquid; The mass ratio of the nano-silica to the silane coupling agent KH-570 is 1:0.02-0.04; The mass ratio of the polyurethane acrylate, 1,6-hexanediol diacrylate, silanized silica dispersion, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, light stabilizer, defoamer, and leveling agent is 1:0.4-0.44:0.16-0.18:0.04-0.06:0.01-0.03:0.004-0.006:0.007-0.

009.

9. A method for preparing a heat-insulating automotive color-changing film according to any one of claims 1-8, characterized in that, The preparation steps are as follows: Step S1: Add the modified hollow glass microspheres to the modified thermoplastic polyurethane base solution, heat to 30-50℃, stir for 20-40 minutes at a speed of 50-250 rpm, add to a three-roll mill with a roller speed ratio of 1:2:5, add defoamer and leveling agent, stir for 15-25 minutes to obtain slurry; Step S2: Place the silicone release film on the coating machine's feed roller and process it online using a corona treatment machine with a power density of 50W / m³. 2 The conveying speed is 10m / min, and the process is carried out once per batch. The slurry is added to the coating machine tank, the film thickness is controlled at 250μm, the temperature is raised to 48-52℃, and the film is dried for 4-6min. The temperature is raised to 58-62℃, and the film is dried for 7-9min. The temperature is raised to 68-72℃, and the film is dried for 8-12min. The modified polyurethane surface coating liquid is then added to the coating machine tank for coating, the temperature is raised to 70-90℃, and the film is dried for 4-6min. The film is then cured under a UV lamp, cooled, and allowed to stand for curing to obtain the automotive color-changing film.

10. A method for preparing a heat-insulating automotive color-changing film according to claim 9, characterized in that, The mass ratio of the modified hollow glass microspheres, modified thermoplastic polyurethane base solution, defoamer and leveling agent mentioned in step S1 is 1:1.6-1.8:0.0028-0.003:0.0055-0.0058; In step S2, the mass ratio of the silicone release film, slurry, and modified polyurethane surface coating liquid is 1:4.5-4.9:0.54-0.58.

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