Wear-resistant vehicle body film and preparation method thereof

Abstract

The invention discloses a wear-resistant vehicle body film and a preparation method thereof, and relates to the technical field of films. The wear-resistant automobile body film prepared by the invention is prepared from polytetrahydrofuran ether glycol, isophorone diisocyanate, a catalyst, dihydric alcohol quaternary ammonium salt, a functional aid, modified silicon dioxide and a chain extender. The dihydric alcohol quaternary ammonium salt is obtained by reacting N, N '-dihexyl-N, N'-dimethyl propane-1, 3-diamine with monochloroacetone and then condensing with glycerol; the functional additive is obtained by reacting 2-boric acid thiophene-4-methyl acetate with 2, 7-dibromofluorene and then carrying out bromination hydrolysis; the modified silicon dioxide is obtained by reacting pretreated silicon dioxide with melamine and then reacting with sodium hypophosphite. The wear-resistant vehicle body film prepared by the invention has good anti-aging, wear-resistant, antibacterial and flame-retardant properties.

Description

Technical Field

[0001] This invention relates to the field of membrane technology, specifically to a wear-resistant car body film and its preparation method. Background Technology

[0002] Car wrapping is a protective and decorative material applied to the surface of a vehicle's paint using polymer composite materials. It is widely used in the automotive aftermarket to protect the original paint, personalize the color, and enhance functionality. Its core materials are typically polymers such as polyvinyl chloride (PVC), thermoplastic polyurethane elastomer (TPU), and polyester substrate (PET). PVC is widely used due to its low cost and rich colors, but it suffers from poor photothermal stability, yellowing, and insufficient tensile and impact resistance. TPU, with its high elasticity, low-temperature resistance, and self-healing properties, has become the mainstream choice for high-end car wraps. PET, due to its strong durability and excellent moisture resistance, is exceptionally used in the glass film industry.

[0003] While these materials exhibit good flexibility, ductility, and chemical resistance, traditional car wraps still suffer from insufficient abrasion resistance. For example, they are easily scratched by small stones when driving on gravel roads, and long-term exposure to ultraviolet radiation, high temperatures, and acid rain can lead to material aging, fading, and even delamination. Furthermore, vehicles operating at high temperatures or in extreme environments pose a fire risk, thus requiring the addition of flame retardants to improve the material's flame resistance and prevent combustion accidents caused by short circuits, collisions, or high temperatures. Simultaneously, car wrap surfaces are prone to bacterial and mold growth, especially in humid environments, which not only affects aesthetics but may also threaten the health of passengers. Therefore, antibacterial properties are a crucial indicator for functional car wraps. To address these issues, existing technologies urgently need to develop new car wrap materials that combine high abrasion resistance, anti-aging properties, flame retardancy, and antibacterial properties to achieve a comprehensive improvement in material performance, thereby meeting the diverse needs of the automotive aftermarket for protective, durable, and safe car wraps. Summary of the Invention

[0004] The purpose of this invention is to provide a wear-resistant car body film and its preparation method to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a wear-resistant car body wrap includes the following preparation steps: (1) The bis-headed quaternary ammonium salt was obtained by reacting N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine with monochloroacetone; (2) Glycerol and bis-headed quaternary ammonium salt are reacted to obtain diol quaternary ammonium salt; (3) Pretreated silica and melamine were reacted to obtain pre-modified silica; pre-modified silica, paraformaldehyde and sodium hypophosphite were reacted to obtain modified silica; (4) The intermediate was obtained by reacting 2,7-dibromofluorene and methyl 2-boronthiophene-4-acetate; (5) Brominate the intermediate to obtain the functional additive precursor; acid hydrolyze the functional additive precursor to obtain the functional additive; (6) Weigh the following components: polytetrahydrofuran ether diol, isophorone diisocyanate, catalyst, diol quaternary ammonium salt, acetone, functional additives, modified silica, chain extender; mix and cure the above components to obtain wear-resistant car body film.

[0006] As an optimization, the preparation method of the bis-headed quaternary ammonium salt in step (1) is as follows: N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone, triethylamine, and acetonitrile are mixed and heated to 70-80℃ and refluxed for 20-24h to obtain the bis-headed quaternary ammonium salt; the molar ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone, and triethylamine is 1:(2.2-2.5):(3-3.5); the mass ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, and acetonitrile is 1:(10-12).

[0007] As an optimization, the preparation method of the diol quaternary ammonium salt in step (2) is as follows: glycerol, bis-headed quaternary ammonium salt, catalyst and isobutyl acetate are mixed and stirred at 110-120℃ for 10-12h to obtain diol quaternary ammonium salt; the molar ratio of glycerol and bis-headed quaternary ammonium salt is (2.0-2.05):1; the mass ratio of glycerol, catalyst Amberlyst-15 and isobutyl acetate is 1:(0.02-0.03):(10-12).

[0008] As an optimization, the preparation method of the modified silica in step (3) is as follows: pretreated silica is ultrasonically dispersed in N,N-dimethylformamide, melamine and triethylamine are added, and the mixture is refluxed at 100-110℃ for 10-12 hours under nitrogen protection to obtain pre-modified silica; the mass ratio of pretreated silica, melamine and N,N-dimethylformamide is 1:(0.3-0.5):(20-30). The molar ratio of melamine to triethylamine is 1:(1.3-1.5); the pre-modified silica, paraformaldehyde, sodium hypophosphite, and pure water are ultrasonically mixed in a mass ratio of 1:(0.2-0.3):(0.6-0.9):(20-30), and concentrated hydrochloric acid at a mass ratio of 3-4 times that of paraformaldehyde is added dropwise at a rate of 0.4 mL / min. The mixture is then heated to 70-80℃ and refluxed for 6-8 hours to obtain modified silica.

[0009] As an optimization, the preparation method of the pretreated silica is as follows: 3-chloropropyltriethoxysilane, ethanol, and pure water are mixed in a volume ratio of 1:(2-3):(2-3), the pH of the solution is adjusted to 4-5 with acetic acid, and the mixture is stirred and hydrolyzed for 30-40 min to obtain a siloxane solution; silica, anhydrous ethanol, and the siloxane solution are mixed evenly, and the mixture is heated to 70-80℃ and reacted for 2-3 h to obtain pretreated silica; the mass ratio of silica, anhydrous ethanol, and 3-chloropropyltriethoxysilane is 1:(10-12):(0.1-0.3).

[0010] As an optimization, the preparation method of the intermediate in step (4) is as follows: 2,7-dibromofluorene, methyl 2-boronthiophene-4-acetate, tetratriphenylphosphine palladium, potassium carbonate, and solvent are mixed and heated to 80-90℃ under nitrogen protection and refluxed for 10-12h; after cooling to room temperature, pure water with a volume of 2-3 times that of the solvent is added for dilution, separation and purification are performed to obtain the intermediate; the solvent is obtained by mixing toluene / ethanol / water in a volume ratio of 1:1:1; the mass of the solvent is 20-30 times that of 2,7-dibromofluorene; the molar ratio of 2,7-dibromofluorene, methyl 2-boronthiophene-4-acetate, tetratriphenylphosphine palladium, and potassium carbonate is 1:(2.2-2.5):(0.03-0.05):(3-3.5).

[0011] As an optimization, the preparation method of methyl 2-boronthiophene-4-acetate is as follows: Under nitrogen protection, methyl 2-bromothiophene-4-acetate is dissolved in tetrahydrofuran, cooled to -78°C, and a 2.5M n-butyllithium solution is added dropwise at a rate of 0.2 mL / min. The reaction system temperature is maintained at -78 to -70°C for 1-2 hours. Trimethyl borate is then added dropwise at a rate of 0.2 mL / min, and the reaction continues at -78 to -70°C. After 30-40 minutes, the temperature is raised to 0℃ and reacted for 2-3 hours, then raised to room temperature and reacted for 8-10 hours. The pH is adjusted to 2-3 with hydrochloric acid and stirred for 30 minutes to obtain methyl 2-boronthiophene-4-acetate. The molar ratio of methyl 2-bromothiophene-4-acetate, n-butyllithium, and trimethyl borate is 1:(1.2-1.5):(3-3.5). The mass of tetrahydrofuran is 20-30 times that of methyl 2-bromothiophene-4-acetate. As an optimization, the preparation method of the functional additive in step (5) is as follows: the intermediate, N-bromosuccinimide, benzoyl peroxide and tetrachloromethane are mixed, heated to 50-60℃ and reacted for 10-12h, cooled to room temperature, and the reaction is quenched by stirring with saturated sodium sulfate solution for 10-15min; the functional additive precursor is obtained; the functional additive precursor is dissolved in tetrahydrofuran, the pH is adjusted to 2-3 with hydrochloric acid, heated to 60-80℃ and stirred for 1-2h to obtain the functional additive; the mass ratio of the functional additive to tetrahydrofuran is 1:(10-12); the molar ratio of the intermediate, N-bromosuccinimide and benzoyl peroxide is 1:(1.0-1.1):(0.03-0.05); the mass of tetrachloromethane is 10-12 times that of the intermediate.

[0012] As an optimization, the amount of the components in step (6) is as follows: by mass parts: 100 parts of polytetrahydrofuran ether diol, 50-60 parts of isophorone diisocyanate, 0.1-0.2 parts of dibutyltin dilaurate catalyst, 5-10 parts of diol quaternary ammonium salt, 140-160 parts of acetone, 2-3 parts of functional additives, 10-15 parts of modified silica, and 7-10 parts of chain extender.

[0013] As an optimization, the preparation method of the wear-resistant car body film in step (6) is as follows: Polytetrahydrofuran ether diol, isophorone diisocyanate, dibutyltin dilaurate catalyst, and diol quaternary ammonium salt are mixed and stirred at 70-80℃ for 3-4 hours under a nitrogen atmosphere. Acetone solvent is added and stirred evenly to obtain a polyurethane prepolymer solution. The polyurethane prepolymer solution and chain extender 1,4-butanediol are reacted for 30-40 minutes. Functional additives and modified silica are added. Triethylamine is added to adjust the pH to 7. After mixing evenly, the mixture is poured into a mold and degassed in a vacuum oven at 80℃ for 10 minutes. Finally, it is cured at 80℃ to obtain the wear-resistant car body film. The present invention also provides a wear-resistant car body film prepared according to the above-described method for preparing wear-resistant car body film.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: The wear-resistant vehicle wrap film prepared by this invention comprises polytetrahydrofuran ether diol, isophorone diisocyanate, a catalyst, a diol quaternary ammonium salt, functional additives, modified silica, and a chain extender. The diol quaternary ammonium salt is obtained by reacting N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine with monochloroacetone, followed by condensation with glycerol. The functional additives are obtained by reacting methyl 2-borate-thiophene-4-acetate with 2,7-dibromofluorene, followed by bromination and hydrolysis. The modified silica is obtained by reacting pretreated silica with melamine, followed by reaction with sodium hypophosphite. The wear-resistant vehicle wrap film prepared by this invention exhibits excellent anti-aging, wear-resistant, antibacterial, and flame-retardant properties.

[0015] First, N'-dihexyl-N,N'-dimethylpropane-1,3-diamine containing a dual-terminal tertiary amine is reacted with monochloroacetone to generate a dual-terminal quaternary ammonium salt, and a carbonyl group is introduced onto the quaternary ammonium salt. The diol in glycerol reacts with the carbonyl group to generate a ketal bond. Since the ketal bond is reversible, introducing it into the polyurethane backbone can endow the polyurethane with good self-healing properties. Secondly, nano-silica can impart good wear resistance to polymers through nano-filling effect, interfacial bonding, and the formation of friction film. However, nano-particles are very prone to agglomeration and uneven dispersion in the matrix, affecting the wear resistance. Pretreatment of silica surfaces with 3-chloropropyltriethoxysilane to contain chloropropyl groups, followed by reaction with melamine and then with sodium hypophosphite, generates compounds on the silica surface containing both phosphorus and nitrogen flame-retardant elements, giving the material good flame-retardant properties. At the same time, the formation of phosphoric acid structures gives the nano-silica surface a strong negative charge, preventing particle agglomeration. The positive charge on the polyurethane and the negative charge on the silica surface enhance the dispersion of silica in the material matrix through electrostatic interaction, thereby further improving the wear resistance.

[0016] The functional additive is obtained by reacting methyl 2-boronate-4-acetate with 2,7-dibromofluorene, followed by bromination and hydrolysis. The fluorene group has a moderate band gap and good planar rigidity and conductivity. The thiophene group is a good modifying group; its structure is electron-rich and can consume ultraviolet light energy through electron migration and transition, helping to extend the absorption spectrum to the entire ultraviolet region. By grafting methyl thiopheneate onto both ends of 2,7-dibromofluorene through Suzuki coupling, the spectral absorption range can be broadened. Compounds with this structure can partially convert absorbed ultraviolet light energy into light radiation. The light is released, producing fluorescence. Bromine is then grafted onto thiophene via a bromination reaction, utilizing its heavy atom effect to quench the fluorescence and generate a UV absorber with dual UVB and UVA absorption bands. This UV absorber is added to polyurethane as a functional additive, imparting excellent resistance to UV aging. Finally, acid hydrolysis converts the ester groups on thiophene acetate into carboxyl groups, giving the functional additive double-ended carboxyl groups. These carboxyl groups can then form a cross-linked network between positively charged polyurethane chains through electrostatic attraction of weak bonds, enhancing mechanical properties without affecting the elasticity of the polyurethane. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] The polytetrahydrofuran ether diol described in the following examples and comparative examples has a molecular weight of 1000; the silica has a particle size of 200 nm.

[0019] Example 1: A method for preparing a wear-resistant vehicle body wrap film, the method comprising the following preparation steps: (1) N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone, triethylamine and acetonitrile were mixed and heated to 80℃ and refluxed for 24h. The filtrate was filtered and retained. The crude product was obtained by rotary evaporation. The crude product was then dissolved in acetone, precipitated with diethyl ether, filtered, washed with diethyl ether and dried to obtain a bis-headed quaternary ammonium salt. The molar ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone and triethylamine was 1:2.2:3. The mass ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine and acetonitrile was 1:10. (2) Glycerol, bis-headed quaternary ammonium salt, catalyst Amberlyst-15, and isobutyl acetate were mixed and stirred at 120°C for 12 h. Water was removed by a water separator during the reaction. After the reaction, the catalyst was removed by filtration. The filtrate was subjected to rotary evaporation under reduced pressure, redissolved in dichloromethane, and column chromatography (V) 二氯甲烷 V 甲醇 The diol quaternary ammonium salt was purified by a ratio of 4:1; the molar ratio of glycerol to bis(2.0:1) quaternary ammonium salt was 2.0:1; the mass ratio of glycerol, catalyst Amberlyst-15, and isobutyl acetate was 1:0.02:10. (3) Mix 3-chloropropyltriethoxysilane, ethanol, and pure water in a volume ratio of 1:2:2, adjust the pH of the solution to 5 with acetic acid, and stir and hydrolyze for 40 min to obtain a siloxane solution; mix silica, anhydrous ethanol, and the siloxane solution, and heat to 80℃ for 3 h to obtain pretreated silica; the mass ratio of silica, anhydrous ethanol, and 3-chloropropyltriethoxysilane is 1:10:0.1; ultrasonically disperse the pretreated silica in N,N-dimethylformamide, add melamine and triethylamine, and heat to 11℃ under nitrogen protection. The mixture was refluxed at 0℃ for 12 h, filtered, washed, and dried to obtain pre-modified silica. The mass ratio of pretreated silica, melamine, and N,N-dimethylformamide was 1:0.3:20; the molar ratio of melamine and triethylamine was 1:1.3. The pre-modified silica, paraformaldehyde, sodium hypophosphite, and pure water were ultrasonically mixed at a mass ratio of 1:0.2:0.6:20. Concentrated hydrochloric acid, three times the mass of paraformaldehyde, was added dropwise at a rate of 0.4 mL / min. The mixture was then refluxed at 80℃ for 8 h, filtered, washed, and dried to obtain modified silica. (4) Under nitrogen protection, methyl 2-bromothiophene-4-acetate was dissolved in tetrahydrofuran, cooled to -78°C, and 2.5M n-butyllithium solution was added dropwise at a rate of 0.2 mL / min. The reaction system temperature was maintained at -70°C for 2 h. Trimethyl borate was added dropwise at a rate of 0.2 mL / min. The reaction was continued at -70°C for 40 min, then the temperature was raised to 0°C for 3 h, and then the temperature was raised to room temperature for 10 h. The pH was adjusted to 3 with hydrochloric acid and stirred for 30 min. The product was extracted with ethyl acetate, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was recrystallized from n-hexane, washed, and dried to obtain methyl 2-bromothiophene-4-acetate. The molar ratio of methyl 2-bromothiophene-4-acetate, n-butyllithium, and trimethyl borate was 1:1.2:3. The mass of tetrahydrofuran was 20 times that of methyl 2-bromothiophene-4-acetate. 2,7-Dibromofluorene, methyl 2-boronthiophene-4-acetate, tetra(triphenylphosphine)palladium, potassium carbonate, and solvent were mixed and heated to 90°C under nitrogen protection, and refluxed for 12 h. After cooling to room temperature, the mixture was diluted with twice the volume of pure water, extracted with ethyl acetate, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was purified by column chromatography (n-hexane) to obtain the intermediate. The solvent was prepared by mixing toluene / ethanol / water in a volume ratio of 1:1:1, with the solvent mass being 20 times that of 2,7-dibromofluorene. The molar ratio of 2,7-dibromofluorene, methyl 2-boronthiophene-4-acetate, tetra(triphenylphosphine)palladium, and potassium carbonate was 1:2.2:0.03:3. (5) The intermediate, N-bromosuccinimide, benzoyl peroxide, and tetrachloromethane were mixed and heated to 60°C for 12 h. After cooling to room temperature, the reaction was quenched by stirring with saturated sodium sulfate solution for 15 min. The mixture was then extracted with tetrachloromethane, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The mixture was then subjected to column chromatography (V... 正己烷 V 二氯甲烷 The precursor of the functional additive was purified by a ratio of 5:1; the pH was adjusted to 3 with hydrochloric acid, the temperature was raised to 80℃ and stirred for 2 hours, and the product was extracted with ethyl acetate, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the functional additive; the mass ratio of the functional additive to tetrahydrofuran was 1:10. The molar ratio of the intermediate, N-bromosuccinimide, and benzoyl peroxide is 1:1.0:0.03; the mass of tetrachloromethane is 10 times that of the intermediate.

[0020] (6) Weigh the following components by mass: 100 parts of polytetrahydrofuran ether diol, 50 parts of isophorone diisocyanate, 0.1 parts of catalyst dibutyltin dilaurate, 5 parts of diol quaternary ammonium salt, 140 parts of acetone, 2 parts of functional additives, 10 parts of modified silica, and 7 parts of chain extender; mix polytetrahydrofuran ether diol, isophorone diisocyanate, catalyst dibutyltin dilaurate, and diol quaternary ammonium salt, stir for 4 hours under nitrogen atmosphere and at 80°C, add solvent acetone, stir evenly to obtain polyurethane prepolymer solution, react polyurethane prepolymer solution and chain extender 1,4-butanediol for 40 minutes, add functional additives and modified silica, add triethylamine to adjust pH to 7, mix evenly, pour into mold, degas in vacuum oven at 80°C for 10 minutes, and cure at 80°C to obtain wear-resistant car body film.

[0021] Example 2: A method for preparing a wear-resistant vehicle body wrap film, the method comprising the following preparation steps: (1) N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone, triethylamine and acetonitrile were mixed and heated to 75°C and refluxed for 22 h. The filtrate was filtered and retained. The crude product was obtained by rotary evaporation. The crude product was then dissolved in acetone, precipitated with diethyl ether, filtered, washed with diethyl ether and dried to obtain a bis-headed quaternary ammonium salt. The molar ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone and triethylamine was 1:2.3:3.3. The mass ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine and acetonitrile was 1:11. (2) Glycerol, bis-headed quaternary ammonium salt, catalyst Amberlyst-15, and isobutyl acetate were mixed and stirred at 115°C for 11 h. Water was removed by a water separator during the reaction. After the reaction, the catalyst was removed by filtration. The filtrate was subjected to rotary evaporation under reduced pressure, redissolved in dichloromethane, and column chromatography (V) 二氯甲烷 V 甲醇 The diol quaternary ammonium salt was purified by a ratio of 4:1; the molar ratio of glycerol to bis(2.04:1) quaternary ammonium salt was 2.04:1; the mass ratio of glycerol, catalyst Amberlyst-15, and isobutyl acetate was 1:0.025:11. (3) Mix 3-chloropropyltriethoxysilane, ethanol, and pure water in a volume ratio of 1:2.5:2.5, adjust the pH of the solution to 4.5 with acetic acid, and stir and hydrolyze for 35 min to obtain a siloxane solution; mix silica, anhydrous ethanol, and the siloxane solution, and heat to 75℃ for 2.5 h to obtain pretreated silica; the mass ratio of silica, anhydrous ethanol, and 3-chloropropyltriethoxysilane is 1:11:0.2; ultrasonically disperse the pretreated silica in N,N-dimethylformamide, add melamine and triethylamine, and heat under nitrogen protection. The mixture was refluxed at 105℃ for 11 hours, filtered, washed, and dried to obtain pre-modified silica. The mass ratio of pretreated silica, melamine, and N,N-dimethylformamide was 1:0.4:25; the molar ratio of melamine and triethylamine was 1:1.4. The pre-modified silica, paraformaldehyde, sodium hypophosphite, and pure water were ultrasonically mixed at a mass ratio of 1:0.25:0.8:25. Concentrated hydrochloric acid at a mass ratio of 3.5 times that of paraformaldehyde was added dropwise at a rate of 0.4 mL / min. The mixture was then refluxed at 75℃ for 7 hours, filtered, washed, and dried to obtain modified silica. (4) Under nitrogen protection, methyl 2-bromothiophene-4-acetate was dissolved in tetrahydrofuran, cooled to -78°C, and 2.5M n-butyllithium solution was added dropwise at a rate of 0.2 mL / min. The reaction system temperature was maintained at -75°C for 1.5 h. Trimethyl borate was added dropwise at a rate of 0.2 mL / min. The reaction was continued at -75°C for 35 min, then the temperature was raised to 0°C for 2.5 h, and then the temperature was raised to room temperature for 9 h. The pH was adjusted to 2.5 with hydrochloric acid and stirred for 30 min. The product was extracted with ethyl acetate, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was recrystallized from n-hexane, washed, and dried to obtain methyl 2-bromothiophene-4-acetate. The molar ratio of methyl 2-bromothiophene-4-acetate, n-butyllithium, and trimethyl borate was 1:1.4:3.2. The mass of tetrahydrofuran was 25 times that of methyl 2-bromothiophene-4-acetate. 2,7-Dibromofluorene, methyl 2-boronthiophene-4-acetate, tetra(triphenylphosphine)palladium, potassium carbonate, and solvent were mixed and heated to 85°C under nitrogen protection, and refluxed for 11 h. After cooling to room temperature, the mixture was diluted with 2.5 times the volume of pure water, extracted with ethyl acetate, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was purified by column chromatography (n-hexane) to obtain the intermediate. The solvent was prepared by mixing toluene / ethanol / water in a volume ratio of 1:1:1, and the mass of the solvent was 25 times that of 2,7-dibromofluorene. The molar ratio of 2,7-dibromofluorene, methyl 2-boronthiophene-4-acetate, tetra(triphenylphosphine)palladium, and potassium carbonate was 1:2.3:0.04:3.2. (5) The intermediate, N-bromosuccinimide, benzoyl peroxide, and tetrachloromethane were mixed and heated to 55°C for 11 h. After cooling to room temperature, the reaction was quenched by stirring with saturated sodium sulfate solution for 13 min. The mixture was then extracted with tetrachloromethane, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The mixture was then subjected to column chromatography (V... 正己烷 V 二氯甲烷 The precursor of the functional adjuvant was purified by a ratio of 5:1 to obtain a functional adjuvant precursor. The functional adjuvant precursor was dissolved in tetrahydrofuran, the pH was adjusted to 2.5 with hydrochloric acid, the temperature was raised to 70°C and stirred for 1.5 h, and the mixture was extracted with ethyl acetate, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the functional adjuvant. The mass ratio of the functional adjuvant to tetrahydrofuran was 1:11. The molar ratio of the intermediate, N-bromosuccinimide, and benzoyl peroxide is 1:1.05:0.04; the mass of tetrachloromethane is 11 times that of the intermediate.

[0022] (6) Weigh the following components by mass: 100 parts of polytetrahydrofuran ether diol, 55 parts of isophorone diisocyanate, 0.15 parts of catalyst dibutyltin dilaurate, 7 parts of diol quaternary ammonium salt, 150 parts of acetone, 2.5 parts of functional additives, 13 parts of modified silica, and 8 parts of chain extender; mix polytetrahydrofuran ether diol, isophorone diisocyanate, catalyst dibutyltin dilaurate, and diol quaternary ammonium salt, stir at 75°C for 3.5 h under a nitrogen atmosphere, add acetone solvent, stir evenly to obtain polyurethane prepolymer solution, react polyurethane prepolymer solution and chain extender 1,4-butanediol for 35 min, add functional additives and modified silica, add triethylamine to adjust pH to 7, mix evenly, pour into mold, degas in vacuum oven at 80°C for 10 min, and cure at 80°C to obtain wear-resistant car body film.

[0023] Example 3: A method for preparing a wear-resistant vehicle body wrap film, the method comprising the following preparation steps: (1) N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone, triethylamine and acetonitrile were mixed and heated to 70℃ and refluxed for 20h. The filtrate was filtered and retained. The crude product was obtained by rotary evaporation. The crude product was then dissolved in acetone, precipitated with diethyl ether, filtered, washed with diethyl ether and dried to obtain a bis-headed quaternary ammonium salt. The molar ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone and triethylamine was 1:2.5:3.5. The mass ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine and acetonitrile was 1:12. (2) Glycerol, bis-headed quaternary ammonium salt, catalyst Amberlyst-15, and isobutyl acetate were mixed and stirred at 110°C for 10 h. Water was removed by a water separator during the reaction. After the reaction, the catalyst was removed by filtration. The filtrate was subjected to rotary evaporation under reduced pressure, redissolved in dichloromethane, and column chromatography (V) 二氯甲烷 V 甲醇 The diol quaternary ammonium salt was purified by a ratio of 4:1; the molar ratio of glycerol to bis(2.05:1) quaternary ammonium salt was 2.05:1; the mass ratio of glycerol, catalyst Amberlyst-15, and isobutyl acetate was 1:0.03:12. (3) Mix 3-chloropropyltriethoxysilane, ethanol, and pure water in a volume ratio of 1:3:3, adjust the pH of the solution to 4 with acetic acid, and stir for 30 min to obtain a siloxane solution; mix silica, anhydrous ethanol, and the siloxane solution, and heat to 70℃ for 2 h to obtain pretreated silica; the mass ratio of silica, anhydrous ethanol, and 3-chloropropyltriethoxysilane is 1:12:0.3; ultrasonically disperse the pretreated silica in N,N-dimethylformamide, add melamine and triethylamine, and heat to 1℃ under nitrogen protection. The mixture was refluxed at 00℃ for 10 h, filtered, washed, and dried to obtain pre-modified silica. The mass ratio of pretreated silica, melamine, and N,N-dimethylformamide was 1:0.5:30; the molar ratio of melamine and triethylamine was 1:1.5. The pre-modified silica, paraformaldehyde, sodium hypophosphite, and pure water were ultrasonically mixed at a mass ratio of 1:0.3:0.9:30. Concentrated hydrochloric acid, four times the mass of paraformaldehyde, was added dropwise at a rate of 0.4 mL / min. The mixture was then refluxed at 70℃ for 6 h, filtered, washed, and dried to obtain modified silica. (4) Under nitrogen protection, methyl 2-bromothiophene-4-acetate was dissolved in tetrahydrofuran, cooled to -78°C, and 2.5M n-butyllithium solution was added dropwise at a rate of 0.2 mL / min. The reaction system temperature was maintained at -78°C for 1 h. Trimethyl borate was added dropwise at a rate of 0.2 mL / min. The reaction was continued at -78°C for 30 min, then the temperature was raised to 0°C for 2 h, and then the temperature was raised to room temperature for 8 h. The pH was adjusted to 2 with hydrochloric acid and stirred for 30 min. The product was extracted with ethyl acetate, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was recrystallized from n-hexane, washed, and dried to obtain methyl 2-bromothiophene-4-acetate. The molar ratio of methyl 2-bromothiophene-4-acetate, n-butyllithium, and trimethyl borate was 1:1.5:3.5. The mass of tetrahydrofuran was 30 times that of methyl 2-bromothiophene-4-acetate. 2,7-Dibromofluorene, methyl 2-boronthiophene-4-acetate, tetra(triphenylphosphine)palladium, potassium carbonate, and solvent were mixed and heated to 80°C under nitrogen protection, and refluxed for 10 h. After cooling to room temperature, the mixture was diluted with three times the volume of pure water, extracted with ethyl acetate, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was purified by column chromatography (n-hexane) to obtain the intermediate. The solvent was prepared by mixing toluene / ethanol / water in a volume ratio of 1:1:1, with the solvent mass being 30 times that of 2,7-dibromofluorene. The molar ratio of 2,7-dibromofluorene, methyl 2-boronthiophene-4-acetate, tetra(triphenylphosphine)palladium, and potassium carbonate was 1:2.5:0.05:3.5. (5) The intermediate, N-bromosuccinimide, benzoyl peroxide, and tetrachloromethane were mixed and heated to 50°C for 10 h. After cooling to room temperature, the reaction was quenched by stirring with saturated sodium sulfate solution for 10 min. The mixture was then extracted with tetrachloromethane, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The mixture was then subjected to column chromatography (V... 正己烷 V 二氯甲烷 The functional additive precursor was obtained by purification with a ratio of 5:1. The functional additive precursor was dissolved in tetrahydrofuran, the pH was adjusted to 2 with hydrochloric acid, the temperature was raised to 60°C and stirred for 1 h, and the mixture was extracted with ethyl acetate, washed with saturated brine, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the functional additive. The mass ratio of the functional additive to tetrahydrofuran was 1:12. The molar ratio of the intermediate, N-bromosuccinimide, and benzoyl peroxide is 1:1.1:0.05; the mass of tetrachloromethane is 12 times that of the intermediate.

[0024] (6) Weigh the following components by mass: 100 parts of polytetrahydrofuran ether diol, 60 parts of isophorone diisocyanate, 0.2 parts of catalyst dibutyltin dilaurate, 10 parts of diol quaternary ammonium salt, 160 parts of acetone, 3 parts of functional additives, 15 parts of modified silica, and 10 parts of chain extender; mix polytetrahydrofuran ether diol, isophorone diisocyanate, catalyst dibutyltin dilaurate, and diol quaternary ammonium salt, stir for 3 hours at 70°C under a nitrogen atmosphere, add acetone solvent, stir evenly to obtain polyurethane prepolymer solution, react polyurethane prepolymer solution and chain extender 1,4-butanediol for 30 minutes, add functional additives and modified silica, add triethylamine to adjust pH to 7, mix evenly, pour into mold, degas in vacuum oven at 80°C for 10 minutes, and cure at 80°C to obtain wear-resistant car body film.

[0025] Comparative Example 1: The difference between the preparation method of the wear-resistant car body film of Comparative Example 1 and Example 2 is that it does not contain diol quaternary ammonium salt; specifically, it does not contain steps (1) to (2), and steps (6) are modified as follows: Weigh the following components by mass parts: 100 parts of polytetrahydrofuran ether diol, 55 parts of isophorone diisocyanate, 0.15 parts of catalyst dibutyltin dilaurate, 150 parts of acetone, 2.5 parts of functional additives, 13 parts of modified silica, and 8 parts of chain extender; Phlorone diisocyanate and dibutyltin dilaurate catalyst were mixed and stirred at 75°C for 3.5 h under a nitrogen atmosphere. Acetone solvent was added, and the mixture was stirred until homogeneous to obtain a polyurethane prepolymer solution. The polyurethane prepolymer solution and chain extender 1,4-butanediol were reacted for 35 min. Functional additives and modified silica were added and stirred until homogeneous. After the reaction was completed, the mixture was poured into a mold, degassed in a vacuum oven at 80°C for 10 min, and then cured at 80°C to obtain a wear-resistant car body film. The remaining steps were the same as in Example 2.

[0026] Comparative Example 2: The difference between the preparation method of the wear-resistant car body film of Comparative Example 2 and Example 2 is that the silica is not modified. Specifically, step (3) is not included, and step (6) is modified as follows: Weigh the following components by mass: 100 parts of polytetrahydrofuran ether diol, 55 parts of isophorone diisocyanate, 0.15 parts of catalyst dibutyltin dilaurate, 7 parts of diol quaternary ammonium salt, 150 parts of acetone, 2.5 parts of functional additives, 13 parts of silica, and 8 parts of chain extender; Phlorone diisocyanate, dibutyltin dilaurate catalyst, and diol quaternary ammonium salt were mixed and stirred at 75°C for 3.5 h under a nitrogen atmosphere. Acetone solvent was added, and the mixture was stirred until homogeneous to obtain a polyurethane prepolymer solution. The polyurethane prepolymer solution and chain extender 1,4-butanediol were reacted for 35 min. Functional additives and silica were added and stirred until homogeneous. After the reaction was completed, the mixture was poured into a mold, degassed in a vacuum oven at 80°C for 10 min, and then cured at 80°C to obtain a wear-resistant car body film. The remaining steps were the same as in Example 2.

[0027] Comparative Example 3: The difference between the preparation method of the wear-resistant car body film of Comparative Example 3 and Example 2 is that it does not contain functional additives, specifically steps (4) to (5) are not included, and step (6) is modified as follows: Weigh the following components by mass parts: 100 parts of polytetrahydrofuran ether diol, 55 parts of isophorone diisocyanate, 0.15 parts of catalyst dibutyltin dilaurate, 7 parts of diol quaternary ammonium salt, 150 parts of acetone, 13 parts of modified silica, and 8 parts of chain extender; Ketone diisocyanate, dibutyltin dilaurate catalyst, and diol quaternary ammonium salt were mixed and stirred at 75°C for 3.5 h under a nitrogen atmosphere. Acetone solvent was added, and the mixture was stirred until homogeneous to obtain a polyurethane prepolymer solution. The polyurethane prepolymer solution and chain extender 1,4-butanediol were reacted for 35 min. Modified silica was added and stirred until homogeneous. After the reaction was completed, the mixture was poured into a mold, degassed in a vacuum oven at 80°C for 10 min, and then cured at 80°C to obtain a wear-resistant car body film. The remaining steps were the same as in Example 2.

[0028] Test Example 1: Antibacterial performance testing: Test method: The antibacterial properties of the film were tested using the shaking method according to GB / T 20944—2008. The bacterial strain used in the test was Gram-negative Escherichia coli (ATCC 8099). The results are shown in Table 1: A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 1 shows that the material prepared by the present invention has good antibacterial properties.

[0029] The antibacterial properties of Examples 1-3 are superior to those of the comparative examples, indicating that reacting ,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine containing a dual-terminal tertiary amine with monochloroacetone to generate a dual-terminal quaternary ammonium salt, and introducing the quaternary ammonium salt into the polyurethane backbone, can endow the polyurethane with good antibacterial properties.

[0030] Test Example 2: Mechanical property testing: Test method: The tensile strength of the film was tested according to standard GB / T 13002-91; the films prepared in the examples and comparative examples were cut into dumbbell strips with dimensions of 75mm×25mm×0.6mm and a neck width of 4mm. A universal testing machine was used with a force element of 100N and a tensile test at a speed of 200mm / min.

[0031] Anti-aging performance testing: Test method: The films prepared in the examples and comparative examples were cut into dumbbell strips with dimensions of 75mm × 25mm × 0.6mm and a neck width of 4mm. These strips were placed in an accelerated UV aging chamber and irradiated with a 200W mercury light source for 360 hours. The aged samples were then tested according to the mechanical property test methods. The tensile strength retention rate before and after aging was calculated. The results are shown in Table 2.

[0032] Self-healing performance test: Test method: After scratching the films prepared in the examples and comparative examples 10 times with sandpaper, the samples were placed at 95°C for 10 minutes for observation. A score of more than 80% repaired was considered excellent, 50%–80% repaired was considered average, and less than 50% repaired was considered poor. Results are shown in Table 2. A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 2 reveals that the material prepared by the present invention has good mechanical properties, anti-aging properties, and self-healing properties.

[0033] The mechanical properties of Examples 1-3 are superior to those of the Comparative Example, and the anti-aging properties of Examples 1-3 are superior to those of Comparative Example 2. The Examples have good self-healing properties, indicating that firstly, N'-dihexyl-N,N'-dimethylpropane-1,3-diamine containing a dual-terminal tertiary amine and monochloroacetone are reacted to generate a dual-terminal quaternary ammonium salt, and a carbonyl group is introduced onto the quaternary ammonium salt. The diol in glycerol reacts with the carbonyl group to generate a ketal bond. The ketal bond, as a reversible dynamic bond, can impart good self-healing properties to the polyurethane backbone. The functional additive is obtained by reacting methyl thiophene-4-acetate of 2-borate with 2,7-dibromofluorene, followed by bromination and hydrolysis. The fluorene group has a moderate band gap and good planar rigidity and conductivity. The thiophene group is a good modifying group; its structure is electron-rich and can consume ultraviolet light energy through electron migration and transition, helping to extend the absorption spectrum to the entire ultraviolet region. By grafting methyl thiophene acetate onto both ends of 2,7-dibromofluorene through Suzuki coupling, the spectral absorption range can be broadened. Compounds with this structure can partially absorb ultraviolet light energy. It is released in the form of light radiation, producing fluorescence; then, bromine is grafted onto thiophene via a bromination reaction, and its heavy atom effect can be used to quench the fluorescence, generating an ultraviolet light absorber with dual-band absorption of UVB and UVA. This ultraviolet absorber is added to polyurethane as a functional additive, which can give the material good resistance to ultraviolet aging. Finally, through acid hydrolysis, the ester group on thiophene methyl acetate is converted into a carboxyl group, so that the functional additive has double-ended carboxyl groups. It can form a cross-linked network between positively charged polyurethane chains through electrostatic attraction of weak bonds, thereby enhancing mechanical properties.

[0034] Test Example 3: Flame retardant performance testing: Test method: The films prepared in the examples and comparative examples were made into strips measuring 120 mm × 6 mm × 4 m, and the limiting oxygen index was tested according to GB / T 2406.1—2008. The results are shown in Table 3: A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 3 shows that the material prepared by the present invention has good flame retardant properties.

[0035] The flame retardant properties of Examples 1-3 are better than those of the comparative examples, indicating that the silica surface containing chloropropyl groups is pretreated with 3-chloropropyltriethoxysilane, and after reacting with melamine and then with sodium hypophosphite, a compound containing both phosphorus and nitrogen flame retardant elements is generated on the silica surface, giving the material good flame retardant properties.

[0036] Test Example 4: Abrasion resistance testing: Test method: The wear resistance was characterized by the mass loss rate of the film before and after wear. The film was fixed on a 45# steel disc of a tribological testing machine. The test ball was a GCr15 steel ball with a radius of 3mm, the friction radius was 10mm, the machine speed was 300rpm, the load was 10N, and the number of revolutions was 1000. The results are shown in Table 4. A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 4 shows that the material prepared by the present invention has good wear resistance.

[0037] The wear resistance of Examples 1-3 is superior to that of the comparative example, indicating that nano-silica can impart good wear resistance to polymers through nano-filling effect, interfacial bonding, and the formation of friction film. However, nano-particles are very prone to agglomeration and uneven dispersion in the matrix, affecting the wear resistance effect. Pretreatment of silica surfaces with chloropropyl groups by 3-chloropropyltriethoxysilane, followed by reaction with melamine and then with sodium hypophosphite, generates compounds on the silica surface containing both phosphorus and nitrogen flame-retardant elements, imparting good flame-retardant properties to the material. At the same time, the formation of phosphoric acid structures gives the nano-silica surface a strong negative charge, preventing particle agglomeration. The positive charge on the polyurethane and the negative charge on the silica surface enhance the dispersion of silica in the material matrix through electrostatic interaction, thereby further improving the wear resistance.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a wear-resistant car body film, characterized in that, The preparation steps include the following: (1) The bis-headed quaternary ammonium salt was obtained by reacting N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine with monochloroacetone; (2) Glycerol and bis-headed quaternary ammonium salt are reacted to obtain diol quaternary ammonium salt; (3) Pretreated silica and melamine were reacted to obtain pre-modified silica; pre-modified silica, paraformaldehyde and sodium hypophosphite were reacted to obtain modified silica; (4) The intermediate was obtained by reacting 2,7-dibromofluorene and methyl 2-boronthiophene-4-acetate; (5) Brominate the intermediate to obtain the functional additive precursor; acid hydrolyze the functional additive precursor to obtain the functional additive; (6) Weigh the following components: polytetrahydrofuran ether diol, isophorone diisocyanate, catalyst, diol quaternary ammonium salt, acetone, functional additives, modified silica, chain extender; mix and cure the above components to obtain wear-resistant car body film.

2. The method for preparing a wear-resistant car body film according to claim 1, characterized in that, The preparation method of the bis-headed quaternary ammonium salt in step (1) is as follows: N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone, triethylamine and acetonitrile are mixed and heated to 70-80℃ and refluxed for 20-24h to obtain the bis-headed quaternary ammonium salt; the molar ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine, monochloroacetone and triethylamine is 1:(2.2-2.5):(3-3.5); the mass ratio of N,N'-dihexyl-N,N'-dimethylpropane-1,3-diamine and acetonitrile is 1:(10-12).

3. The method for preparing a wear-resistant car body film according to claim 1, characterized in that, The preparation method of the diol quaternary ammonium salt in step (2) is as follows: glycerol, bis-headed quaternary ammonium salt, catalyst and isobutyl acetate are mixed and stirred at 110-120℃ for 10-12h to obtain diol quaternary ammonium salt; the molar ratio of glycerol and bis-headed quaternary ammonium salt is (2.0-2.05):1; the mass ratio of glycerol, catalyst and isobutyl acetate is 1:(0.02-0.03):(10-12).

4. The method for preparing a wear-resistant car body film according to claim 1, characterized in that, The preparation method of the modified silica in step (3) is as follows: pretreated silica is dispersed in N,N-dimethylformamide, melamine and triethylamine are added, and the mixture is heated to 100-110℃ and reacted for 10-12h to obtain pre-modified silica; the mass ratio of pretreated silica, melamine and N,N-dimethylformamide is 1:(0.3-0.5):(20-30); the molar ratio of melamine and triethylamine is 1:(1.3-1.5); the pre-modified silica, paraformaldehyde, sodium hypophosphite and pure water are mixed in a mass ratio of 1:(0.2-0.3):(0.6-0.9):(20-30), concentrated hydrochloric acid with a mass of 3-4 times that of paraformaldehyde is added, and the mixture is heated to 70-80℃ and refluxed for 6-8h to obtain modified silica.

5. The method for preparing a wear-resistant car body film according to claim 4, characterized in that, The method for preparing the pretreated silica is as follows: 3-chloropropyltriethoxysilane, ethanol, and pure water are mixed in a volume ratio of 1:(2-3):(2-3), the pH of the solution is adjusted to 4-5 with acetic acid, and the mixture is stirred and hydrolyzed for 30-40 min to obtain a siloxane solution; silica, anhydrous ethanol, and the siloxane solution are mixed and heated to 70-80℃ for 2-3 h to obtain pretreated silica; the mass ratio of silica, anhydrous ethanol, and 3-chloropropyltriethoxysilane is 1:(10-12):(0.1-0.3).

6. The method for preparing a wear-resistant car body film according to claim 1, characterized in that, The intermediate in step (4) is prepared by mixing 2,7-dibromofluorene, methyl 2-boronthiophene-4-acetate, tetratriphenylphosphine palladium, potassium carbonate, and solvent, heating to 80-90℃ under nitrogen protection, and refluxing for 10-12 hours to obtain the intermediate; the solvent is obtained by mixing toluene / ethanol / water in a volume ratio of 1:1:1; the mass of the solvent is 20-30 times that of 2,7-dibromofluorene; the molar ratio of 2,7-dibromofluorene, methyl 2-boronthiophene-4-acetate, tetratriphenylphosphine palladium, and potassium carbonate is 1:(2.2-2.5):(0.03-0.05):(3-3.5).

7. The method for preparing a wear-resistant car body film according to claim 6, characterized in that, The preparation method of the methyl 2-boronthiophene-4-acetate is as follows: under nitrogen protection, methyl 2-bromothiophene-4-acetate is dissolved in tetrahydrofuran, cooled to -78℃, and 2.5M n-butyllithium solution is added. The reaction is carried out for 1-2 hours, then trimethyl borate is added, and the reaction is continued for 30-40 minutes. The temperature is then raised to 0℃ and reacted for 2-3 hours, and finally raised to room temperature and reacted for 8-10 hours to obtain methyl 2-boronthiophene-4-acetate. The molar ratio of methyl 2-bromothiophene-4-acetate, n-butyllithium, and trimethyl borate is 1:(1.2-1.5):(3-3.5). The mass of tetrahydrofuran is 20-30 times that of methyl 2-bromothiophene-4-acetate.

8. The method for preparing a wear-resistant car body film according to claim 1, characterized in that, The preparation method of the functional additive in step (5) is as follows: the intermediate, N-bromosuccinimide, benzoyl peroxide and tetrachloromethane are mixed and heated to 50-60℃ for 10-12h to obtain the functional additive precursor; the functional additive precursor is dissolved in tetrahydrofuran, the pH is adjusted to 2-3 with hydrochloric acid, and the mixture is heated to 60-80℃ and stirred for 1-2h to obtain the functional additive; the mass ratio of the functional additive to tetrahydrofuran is 1:(10-12); the molar ratio of the intermediate, N-bromosuccinimide and benzoyl peroxide is 1:(1.0-1.1):(0.03-0.05); the mass of tetrachloromethane is 10-12 times that of the intermediate.

9. The method for preparing a wear-resistant car body film according to claim 1, characterized in that, The amounts of the components used in step (6) are as follows: by mass parts, 100 parts of polytetrahydrofuran ether diol, 50-60 parts of isophorone diisocyanate, 0.1-0.2 parts of dibutyltin dilaurate catalyst, 5-10 parts of diol quaternary ammonium salt, 140-160 parts of acetone, 2-3 parts of functional additives, 10-15 parts of modified silica, and 7-10 parts of chain extender.

10. A wear-resistant car body film prepared by the method according to any one of claims 1-9.

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