Ultraviolet-proof automobile film and preparation method thereof

Abstract

The invention discloses a preparation method of an ultraviolet-proof automobile film, which comprises the following steps: uniformly mixing a modified filler, a photoinitiator and a modified coating to prepare a coating solution, coating the surface of a modified substrate with the coating solution, and carrying out ultraviolet curing and drying treatment to prepare the ultraviolet-proof automobile film. The modified filler is prepared by taking titanium dioxide capable of efficiently absorbing ultraviolet rays as a core and hard silicon dioxide as a shell through a sol-gel method. A molecular chain of the modified coating contains a dynamic reversible coordination bond formed by a low-surface-energy polydimethylsiloxane structure and imidazole ring-zinc ions, and the hydrophobic capacity and the microcrack self-repairing capacity of the coating are remarkably improved. The preparation method comprises the following steps: copolymerizing diisocyanate and bis (2-hydroxyethyl) disulfide with a disulfide bond to prepare a polyurethane molecule, and introducing an ultraviolet-proof benzotriazole structure and a hindered phenol structure to a molecular chain end to prepare the modified base material. The ultraviolet-proof fabric has excellent ultraviolet-proof capability and physical protection capability.

Description

Technical Field

[0001] This invention relates to the field of automotive film materials technology, specifically to a UV-blocking automotive film and its preparation method. Background Technology

[0002] UV-blocking automotive films are primarily used in two areas: firstly, as automotive window films, they block ultraviolet rays, insulate against heat, and ensure driving safety and passenger comfort; secondly, as paint protection films (invisible car wraps), they are directly applied to the car paint surface, providing gloss and aesthetics while resisting environmental erosion. However, existing products still have significant shortcomings in long-term use. Regarding physical protection, surface performance is often difficult to balance: ordinary coatings are prone to permanent scratches, while self-healing surfaces are usually soft and lack sufficient wear resistance and scratch resistance; simultaneously, the surface micro-nano structures required to achieve superhydrophobic properties may be worn away during daily car washes and friction, leading to a rapid decline in hydrophobicity, resulting in a contradiction between various physical protective properties. In terms of UV protection, mainstream technologies mostly rely on adding UV absorbers to the substrate or coating. This external method has hidden risks; the absorbers may gradually deplete due to migration and volatilization, or undergo photodegradation under strong, continuous UV radiation, causing the film's UV blocking performance to decline significantly over time, failing to provide long-lasting and stable protection, and consequently affecting the overall weather resistance and lifespan of the substrate and coating. Therefore, there is a clear need to develop a car film with more balanced and durable protective performance. Summary of the Invention

[0003] The purpose of this invention is to provide a UV-blocking automotive film that solves the problem of weak UV blocking and physical protection capabilities of current automotive films.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for preparing a UV-blocking automotive film, specifically including the following steps: Step S1: Disperse the modified filler in tetrahydrofuran, stir and add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and modified coating under the conditions of 200-300 r / min and 50-70℃, and react for 8-10 h to obtain the coating solution. Step S2: Clean the surface of the modified substrate with 800-grit sandpaper, apply the coating solution to the modified substrate with a scraper applicator, irradiate with ultraviolet light at 60-80℃ for 20-30 seconds, turn off the ultraviolet light and continue drying for 30-50 minutes to obtain the ultraviolet-blocking automotive film.

[0005] Furthermore, the weight ratio of the modified filler, tetrahydrofuran, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and the modified coating in step S1 is 10-15:80-90:0.3-0.5:70-85.

[0006] Furthermore, the modified substrate is prepared by the following steps: Step A1: Mix 4-amino-3-nitrophenol, hydrochloric acid and deionized water evenly, stir for 30-40 min at 30-40℃ and 80-100 r / min, cool to 0-5℃, stir and add sodium nitrite, and react for 2-3 h to obtain diazonium salt. Mix p-hydroxybenzoic acid, sodium carbonate and ethanol evenly, stir and add diazonium salt at 0-5℃, 100-120 r / min and pH 8-10, and react for 2-4 h to obtain intermediate 1. Step A2: Mix intermediate 1, ethanol and sodium hydroxide solution evenly, stir and add sodium dithionite at 70-80℃ and 100-120 r / min, and react for 1-2 h to obtain intermediate 2. Mix diisocyanate and N,N-dimethylformamide evenly, stir and add bis(2-hydroxyethyl) disulfide and dibutyltin dilaurate at 80-100 r / min and 60-70℃, and react for 2-3 h. Raise the temperature to 90-100℃, add intermediate 2, adjust the pH to 5-6, and react for 4-6 h to obtain the pretreated polymer. Step A3: Mix the pretreated polymer, 1-hydroxybenzotriazole, and dichloromethane evenly. Stir and add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at a speed of 100-120 r / min and a temperature of 0-5℃. React for 40-50 min. Raise the temperature to 20-30℃, stir, and add 1,2,2,6,6-pentamethylpiperidinol and triethylamine. React for 4-6 h to obtain the modified polymer. Heat the modified polymer to melt at 170-200℃. After mixing and compression, spread it flat on a casting roller, cool and set. At a traction rate of 8-10 m / min, pull and wind it into a film to obtain the modified substrate.

[0007] Furthermore, in step A1, the ratio of 4-amino-3-nitrophenol, hydrochloric acid, deionized water, and sodium nitrite is 2.5g:4mL:20mL:1.2g, the molar concentration of hydrochloric acid is 2mol / L, and the molar ratio of p-hydroxybenzoic acid, sodium carbonate, and diazonium salt is 1mmol:2.1-2.2mmol:1.2mmol.

[0008] Furthermore, in step A2, the ratio of intermediate 1, ethanol, sodium dithionite, and sodium hydroxide solution is 1 mmol: 3-5 mL: 6 mmol: 5 mL, the molar concentration of sodium hydroxide solution is 2 mol / L, and the molar ratio of isocyanate group on diisocyanate, hydroxyl group on bis(2-hydroxyethyl) disulfide, and amino group on intermediate 2 is 1.4: 1.1-1.3: 0.5.

[0009] Further, in step A3, the ratio of the pretreated polymer, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 1,2,2,6,6-pentamethylpiperidinol and triethylamine is 1.2 mmol:1.5 mmol:5-10 mL:1.5 mmol:1 mmol:3 mmol.

[0010] Furthermore, the modified filler is prepared by the following steps: Titanium dioxide, tetraethyl orthosilicate and ethanol are mixed evenly, and under the conditions of 160-180 r / min, pH 5-6 and temperature 75-85℃, mercaptotriethoxysilane is added and the mixture is stirred for 15-18 h to obtain the modified filler.

[0011] Furthermore, the ratio of silicon dioxide, tetraethyl orthosilicate, ethanol, and mercaptotriethoxysilane is 1g:0.3mL:30mL:0.05g.

[0012] Furthermore, the modified coating is prepared by the following steps: Step B1: Mix diisocyanate and N,N-dimethylformamide evenly, stir and add 1,4-butenediol at a speed of 80-100 r / min and a temperature of 60-70℃, and react for 2-3 h. Then raise the temperature to 90-100℃, add aminopropyl-terminated polydimethylsiloxane, and react for 4-6 h to obtain the pretreatment coating. Step B2: Mix the pretreatment coating and tetrahydrofuran evenly, stir and add imidazole-2-carboxaldehyde under the conditions of 200-300 r / min, 60-70℃ and nitrogen gas, and react for 20-24 h. Add zinc chloride and ethanol and react for 12-14 h. Dry at 50-60℃ for 4-6 h to obtain the modified coating.

[0013] Furthermore, in step B1, the ratio of diisocyanate, N,N-dimethylformamide, 1,4-butenediol and aminopropyl-terminated polydimethylsiloxane is 0.4 mmol: 2-4 mL: 0.2 mmol: 0.5 mmol, and the molecular weight of aminopropyl-terminated polydimethylsiloxane is 400.

[0014] Furthermore, in step B2, the ratio of the pretreatment coating, tetrahydrofuran, imidazole-2-carboxaldehyde, zinc chloride, and ethanol is 2g:20mL:15mL:0.15g:5mL.

[0015] The beneficial effects of this invention are as follows: Modified fillers and modified coatings are uniformly dispersed in tetrahydrofuran solvent under a water bath heating environment to obtain a coating solution. The coating solution is then uniformly coated onto a cleaned modified substrate. During ultraviolet irradiation, under the action of a photoinitiator, the thiol groups on the modified fillers react with the carbon-carbon double bonds on the modified coatings to obtain an ultraviolet-blocking automotive film.

[0016] Modified substrate: Under acidic conditions, sodium nitrite is converted to nitrous acid, and the amino group on 4-amino-3-nitrophenol exists as an ammonium salt. At low temperature, the two react to form a diazonium salt. Under weakly alkaline conditions, the phenolic hydroxyl group of p-hydroxybenzoic acid is deprotonated to form a phenoxy anion. Its high ortho-electron density allows it to be attacked by the diazonium salt as an electrophile, generating an azo compound, thus preparing intermediate 1. Under alkaline conditions and the action of the reducing agent sodium dithionite, the nitro group is reduced to hydroxylamine. The newly generated hydroxylamine acts as a nucleophile, attacking the intramolecular azo bond, causing dehydration and cyclization, forming a five-membered heterocyclic structure of benzotriazole, thus preparing intermediate 2. The isocyanate group on the diisocyanate and the hydroxyl group on bis(2-hydroxyethyl) disulfide undergo polymerization under the catalysis of dibutyltin dilaurate. With the addition of intermediate 2, the amino group on it reacts with excess isocyanate groups to obtain the pretreated polymer. Under acidic conditions, the carboxyl groups on the pretreated polymer are activated and then reacted with the hydroxyl groups on 1,2,2,6,6-pentamethylpiperidinol to obtain a modified polymer. The modified substrate is then obtained by extrusion casting.

[0017] Modified filler: Under acidic conditions, the ethoxy group of tetraethyl orthosilicate reacts with water to form a silanol bond, which then undergoes dehydration condensation with the Ti-OH group on the surface of titanium dioxide to form a Si-O-Ti covalent bond, resulting in a silica coating layer. The ethoxy group of mercaptotriethoxysilane hydrolyzes to form a silanol bond, which then undergoes dehydration condensation with the hydroxyl groups on the silica coating layer to form a Si-O-Si covalent bond, thus obtaining the modified filler.

[0018] Modified coating: The isocyanate group on diisocyanate and the hydroxyl group on 1,4-butenediol undergo a polymerization reaction catalyzed by dibutyltin dilaurate. The addition of aminopropyl-terminated polydimethylsiloxane allows the amino groups on it to react with the isocyanate groups, generating an amino-terminated pretreatment coating. The amino groups on the pretreatment coating nucleophilically attack the carbonyl carbon of imidazole-2-carboxaldehyde, forming a Schiff base structure. The nitrogen atom of the imidazole ring on this structure has a lone pair of electrons, which can form stable coordinate bonds with zinc ions, creating ion-coordination crosslinking sites, thus obtaining the modified coating.

[0019] The modified substrate molecular chain contains benzotriazole and hindered phenol structures. Benzotriazole absorbs most of the ultraviolet light, reducing the initial generation of free radicals. The hindered phenols, by scavenging free radicals, protect the benzotriazole structure from free radical attack and failure. This synergistic protection contributes to the long-term stability of the material's UV protection capability. The modified filler forms a core-shell structure with titanium dioxide as the core and silicon dioxide as the shell. The TiO2 core efficiently absorbs and scatters ultraviolet light, while the hard SiO2 shell acts as a physical barrier, enhancing the coating's resistance to friction and scratches. The modified coating contains low surface energy polydimethylsiloxane structures, which significantly improve the coating's hydrophobicity. The dynamic reversible coordination bonds formed by the imidazole ring and zinc ions, as well as the disulfide bonds on the modified substrate molecular chain, can absorb energy through bond breakage when microcracks develop due to scratches or abrasions, preventing the propagation of destructive cracks. Then, the broken bonds recombine, achieving self-repair of the microcracks and enhancing the material's physical protection capability. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: A method for preparing a UV-blocking automotive film, specifically including the following steps: Step S1: Disperse the modified filler in tetrahydrofuran, stir and add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and modified coating at a speed of 200 r / min and a temperature of 50℃, and react for 8 h to obtain the coating solution. Step S2: Clean the surface of the modified substrate with 800-grit sandpaper, apply the coating solution to the modified substrate with a scraper applicator, irradiate with ultraviolet light at 60°C for 20 seconds, turn off the ultraviolet light and continue drying for 30 minutes to obtain the ultraviolet-blocking automotive film.

[0022] The weight ratio of the modified filler, tetrahydrofuran, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and the modified coating in step S1 is 10:80:0.3:85.

[0023] The modified substrate is prepared by the following steps: Step A1: Mix 4-amino-3-nitrophenol, hydrochloric acid and deionized water evenly, stir for 30 min at 30℃ and 80 r / min, cool to 0℃, stir and add sodium nitrite, and react for 2 h to obtain diazonium salt. Mix p-hydroxybenzoic acid, sodium carbonate and ethanol evenly, stir and add diazonium salt at 0℃, 100 r / min and pH 8, and react for 2 h to obtain intermediate 1. Step A2: Mix intermediate 1, ethanol and sodium hydroxide solution evenly, stir and add sodium dithionite at 70℃ and 100 r / min, and react for 1 h to obtain intermediate 2. Mix diisocyanate and N,N-dimethylformamide evenly, stir and add bis(2-hydroxyethyl) disulfide and dibutyltin dilaurate at 80 r / min and 60℃, and react for 2 h. Raise the temperature to 90℃, add intermediate 2, adjust the pH to 5, and react for 4 h to obtain the pretreated polymer. Step A3: Mix the pretreated polymer, 1-hydroxybenzotriazole and dichloromethane evenly. Stir and add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at 100 r / min and 0℃, and react for 40 min. Raise the temperature to 20℃, stir and add 1,2,2,6,6-pentamethylpiperidinol and triethylamine, and react for 4 h to obtain the modified polymer. Heat the modified polymer to 170℃ to melt it. After mixing and compression, spread it flat on the casting roller, cool and set it. At a traction rate of 8 m / min, pull and wind it into a film to obtain the modified substrate.

[0024] In step A1, the ratio of 4-amino-3-nitrophenol, hydrochloric acid, deionized water, and sodium nitrite is 2.5g:4mL:20mL:1.2g, the molar concentration of hydrochloric acid is 2mol / L, and the molar ratio of p-hydroxybenzoic acid, sodium carbonate, and diazonium salt is 1mmol:2.1mmol:1.2mmol.

[0025] In step A2, the ratio of intermediate 1, ethanol, sodium dithionite, and sodium hydroxide solution is 1 mmol:3 mL:6 mmol:5 mL, the molar concentration of sodium hydroxide solution is 2 mol / L, the molar ratio of isocyanate group on diisocyanate, hydroxyl group on bis(2-hydroxyethyl) disulfide, and amino group on intermediate 2 is 1.4:1.1:0.5, and the amount of isocyanate group on diisocyanate is 1 mmol.

[0026] The ratio of the pretreated polymer, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 1,2,2,6,6-pentamethylpiperidinol and triethylamine in step A3 is 1.2 mmol:1.5 mmol:5 mL:1.5 mmol:1 mmol:3 mmol.

[0027] The modified filler is prepared by the following steps: Titanium dioxide, tetraethyl orthosilicate and ethanol were mixed evenly, and then stirred and added with mercaptotriethoxysilane at a speed of 160 r / min, pH 5 and temperature of 75℃ for 15 h to obtain the modified filler.

[0028] The ratio of silicon dioxide, tetraethyl orthosilicate, ethanol and mercaptotriethoxysilane is 1g:0.3mL:30mL:0.05g.

[0029] The modified coating is prepared by the following steps: Step B1: Mix diisocyanate and N,N-dimethylformamide evenly, stir and add 1,4-butenediol at 80 r / min and 60 ℃, react for 2 h, raise the temperature to 90 ℃, add aminopropyl-terminated polydimethylsiloxane, react for 4 h to obtain the pretreatment coating. Step B2: Mix the pretreatment coating and tetrahydrofuran evenly, stir and add imidazole-2-carboxaldehyde under the conditions of 200 r / min, 60℃ and nitrogen gas, and react for 20 h. Add zinc chloride and ethanol and react for 12 h. Dry at 50℃ for 4 h to obtain the modified coating.

[0030] In step B1, the ratio of diisocyanate, N,N-dimethylformamide, 1,4-butenediol and aminopropyl-terminated polydimethylsiloxane is 0.4 mmol:2 mL:0.2 mmol:0.5 mmol, the amount of diisocyanate is 1 mmol, and the molecular weight of aminopropyl-terminated polydimethylsiloxane is 400.

[0031] The ratio of the pretreatment coating, tetrahydrofuran, imidazole-2-carboxaldehyde, zinc chloride and ethanol used in step B2 is 2g:20mL:15mL:0.15g:5mL.

[0032] Example 2, a method for preparing a UV-blocking automotive film, specifically includes the following steps: Step S1: Disperse the modified filler in tetrahydrofuran, stir and add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and modified coating at a speed of 250 r / min and a temperature of 60℃, and react for 9 h to obtain the coating solution. Step S2: Clean the surface of the modified substrate with 800-grit sandpaper, apply the coating solution to the modified substrate with a scraper applicator, irradiate with ultraviolet light at 70°C for 25 seconds, turn off the ultraviolet lamp and continue drying for 40 minutes to obtain the ultraviolet-blocking automotive film.

[0033] The weight ratio of the modified filler, tetrahydrofuran, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and the modified coating in step S1 is 12:85:0.4:75.

[0034] The modified substrate is prepared by the following steps: Step A1: Mix 4-amino-3-nitrophenol, hydrochloric acid and deionized water evenly, stir for 35 min at 35℃ and 90 r / min, cool to 2℃, stir and add sodium nitrite, and react for 2 h to obtain diazonium salt. Mix p-hydroxybenzoic acid, sodium carbonate and ethanol evenly, stir and add diazonium salt at 2℃, 110 r / min and pH 9, and react for 3 h to obtain intermediate 1. Step A2: Mix intermediate 1, ethanol and sodium hydroxide solution evenly, stir and add sodium dithionite at 75℃ and 110 r / min, and react for 1 h to obtain intermediate 2. Mix diisocyanate and N,N-dimethylformamide evenly, stir and add bis(2-hydroxyethyl) disulfide and dibutyltin dilaurate at 65℃, and react for 2 h. Raise the temperature to 95℃, add intermediate 2, adjust the pH to 5, and react for 5 h to obtain the pretreated polymer. Step A3: Mix the pretreated polymer, 1-hydroxybenzotriazole and dichloromethane evenly. Stir and add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at 110 r / min and 2℃, and react for 45 min. Raise the temperature to 25℃, stir and add 1,2,2,6,6-pentamethylpiperidinol and triethylamine, and react for 5 h to obtain the modified polymer. Heat the modified polymer to 180℃ to melt it. After mixing and compression, spread it flat on the casting roller, cool and set it. At a traction rate of 9 m / min, pull and wind it into a film to obtain the modified substrate.

[0035] In step A1, the ratio of 4-amino-3-nitrophenol, hydrochloric acid, deionized water, and sodium nitrite is 2.5g:4mL:20mL:1.2g, the molar concentration of hydrochloric acid is 2mol / L, and the molar ratio of p-hydroxybenzoic acid, sodium carbonate, and diazonium salt is 1mmol:2.1mmol:1.2mmol.

[0036] In step A2, the ratio of intermediate 1, ethanol, sodium dithionite, and sodium hydroxide solution is 1 mmol:4 mL:6 mmol:5 mL, the molar concentration of sodium hydroxide solution is 2 mol / L, the molar ratio of isocyanate group on diisocyanate, hydroxyl group on bis(2-hydroxyethyl) disulfide, and amino group on intermediate 2 is 1.4:1.2:0.5, and the amount of isocyanate group on diisocyanate is 2 mmol.

[0037] The ratio of the pretreated polymer, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 1,2,2,6,6-pentamethylpiperidinol and triethylamine in step A3 is 1.2 mmol:1.5 mmol:8 mL:1.5 mmol:1 mmol:3 mmol.

[0038] The modified filler is prepared by the following steps: Titanium dioxide, tetraethyl orthosilicate and ethanol were mixed evenly, and the mixture was stirred and added under the conditions of 170 r / min, pH 5 and temperature 80℃, and reacted for 16 h to obtain the modified filler.

[0039] The ratio of silicon dioxide, tetraethyl orthosilicate, ethanol and mercaptotriethoxysilane is 1g:0.3mL:30mL:0.05g.

[0040] The modified coating is prepared by the following steps: Step B1: Mix diisocyanate and N,N-dimethylformamide evenly, stir and add 1,4-butenediol at a speed of 90 r / min and a temperature of 65°C, and react for 2 h. Then, raise the temperature to 95°C, add aminopropyl-terminated polydimethylsiloxane, and react for 5 h to obtain the pretreatment coating. Step B2: Mix the pretreatment coating and tetrahydrofuran evenly, stir and add imidazole-2-carboxaldehyde under the conditions of 250 r / min, 65℃ and nitrogen gas, and react for 22 h. Add zinc chloride and ethanol and react for 13 h. Dry at 55℃ for 5 h to obtain the modified coating.

[0041] In step B1, the ratio of diisocyanate, N,N-dimethylformamide, 1,4-butenediol and aminopropyl-terminated polydimethylsiloxane is 0.4 mmol:3 mL:0.2 mmol:0.5 mmol, the amount of diisocyanate is 2 mmol, and the molecular weight of aminopropyl-terminated polydimethylsiloxane is 400.

[0042] The ratio of the pretreatment coating, tetrahydrofuran, imidazole-2-carboxaldehyde, zinc chloride and ethanol used in step B2 is 2g:20mL:15mL:0.15g:5mL.

[0043] Example 3, a method for preparing a UV-blocking automotive film, specifically includes the following steps: Step S1: Disperse the modified filler in tetrahydrofuran, stir and add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and modified coating at a speed of 300 r / min and a temperature of 70℃, and react for 10 h to obtain the coating solution. Step S2: Clean the surface of the modified substrate with 800-grit sandpaper, apply the coating solution to the modified substrate with a scraper applicator, irradiate with ultraviolet light at 80°C for 30 seconds, turn off the ultraviolet lamp and continue drying for 50 minutes to obtain an ultraviolet-blocking automotive film.

[0044] The weight ratio of the modified filler, tetrahydrofuran, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and the modified coating in step S1 is 15:90:0.5:70.

[0045] The modified substrate is prepared by the following steps: Step A1: Mix 4-amino-3-nitrophenol, hydrochloric acid and deionized water evenly, stir for 40 min at 40℃ and 100 r / min, cool to 5℃, stir and add sodium nitrite, and react for 3 h to obtain diazonium salt. Mix p-hydroxybenzoic acid, sodium carbonate and ethanol evenly, stir and add diazonium salt at 5℃, 120 r / min and pH 10, and react for 4 h to obtain intermediate 1. Step A2: Mix intermediate 1, ethanol and sodium hydroxide solution evenly, stir and add sodium dithionite at 80℃ and 120 r / min, and react for 2 h to obtain intermediate 2. Mix diisocyanate and N,N-dimethylformamide evenly, stir and add bis(2-hydroxyethyl) disulfide and dibutyltin dilaurate at 70℃ and 100 r / min, and react for 3 h. Raise the temperature to 100℃, add intermediate 2, adjust the pH to 6, and react for 6 h to obtain the pretreated polymer. Step A3: Mix the pretreated polymer, 1-hydroxybenzotriazole and dichloromethane evenly. Stir and add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at 120 r / min and 5℃, and react for 50 min. Raise the temperature to 30℃, stir and add 1,2,2,6,6-pentamethylpiperidinol and triethylamine, and react for 6 h to obtain the modified polymer. Heat the modified polymer to 200℃ to melt it. After mixing and compression, spread it flat on the casting roller, cool and set it. At a traction rate of 10 m / min, pull and wind it into a film to obtain the modified substrate.

[0046] In step A1, the ratio of 4-amino-3-nitrophenol, hydrochloric acid, deionized water, and sodium nitrite is 2.5g:4mL:20mL:1.2g, the molar concentration of hydrochloric acid is 2mol / L, and the molar ratio of p-hydroxybenzoic acid, sodium carbonate, and diazonium salt is 1mmol:2.2mmol:1.2mmol.

[0047] In step A2, the ratio of intermediate 1, ethanol, sodium dithionite, and sodium hydroxide solution is 1 mmol: 5 mL: 6 mmol: 5 mL, the molar concentration of sodium hydroxide solution is 2 mol / L, the molar ratio of isocyanate group on diisocyanate, hydroxyl group on bis(2-hydroxyethyl) disulfide, and amino group on intermediate 2 is 1.4:1.3:0.5, and the amount of isocyanate group on diisocyanate is 3 mmol.

[0048] The ratio of the pretreated polymer, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 1,2,2,6,6-pentamethylpiperidinol and triethylamine in step A3 is 1.2 mmol:1.5 mmol:10 mL:1.5 mmol:1 mmol:3 mmol.

[0049] The modified filler is prepared by the following steps: Titanium dioxide, tetraethyl orthosilicate and ethanol were mixed evenly, and then stirred and added with mercaptotriethoxysilane at a speed of 180 r / min, pH 6 and temperature of 85℃ for 18 h to obtain the modified filler.

[0050] The ratio of silicon dioxide, tetraethyl orthosilicate, ethanol and mercaptotriethoxysilane is 1g:0.3mL:30mL:0.05g.

[0051] The modified coating is prepared by the following steps: Step B1: Mix diisocyanate and N,N-dimethylformamide evenly, stir and add 1,4-butenediol at 100 r / min and 70 ℃, react for 3 h, heat to 100 ℃, add aminopropyl-terminated polydimethylsiloxane, react for 6 h to obtain the pretreatment coating. Step B2: Mix the pretreatment coating and tetrahydrofuran evenly, stir and add imidazole-2-carboxaldehyde under the conditions of 300 r / min, 70℃ and nitrogen gas, and react for 24 h. Add zinc chloride and ethanol and react for 14 h. Dry at 60℃ for 6 h to obtain the modified coating.

[0052] In step B1, the ratio of diisocyanate, N,N-dimethylformamide, 1,4-butenediol and aminopropyl-terminated polydimethylsiloxane is 0.4 mmol:4 mL:0.2 mmol:0.5 mmol, the amount of diisocyanate is 3 mmol, and the molecular weight of aminopropyl-terminated polydimethylsiloxane is 400.

[0053] The ratio of the pretreatment coating, tetrahydrofuran, imidazole-2-carboxaldehyde, zinc chloride and ethanol used in step B2 is 2g:20mL:15mL:0.15g:5mL.

[0054] Comparative Example 1: This comparative example uses a pretreated polymer instead of a modified polymer, while the other steps are the same as in Example 1.

[0055] Comparative Example 2: This comparative example uses a pretreatment coating instead of a modified coating, while the other steps are the same as in Example 1.

[0056] Comparative Example 3: Compared with Example 1, no modified filler was added in step S1 of this comparative example, but the other steps were the same.

[0057] The UV-blocking automotive films prepared in Examples 1-3 and Comparative Examples 1-3 were tested for abrasion resistance according to GB / T23988-2009 "Determination of Abrasion Resistance of Coatings - Falling Sand Method". The test results are shown in Table 2. The thickness of the modified substrate was 100 μm, and the thickness of the coating was 50 μm. Standard quartz sand was used as the abrasive, and the particle size requirements are shown in Table 1. The sand flow rate was controlled at 90 mL / s.

[0058] The UV-blocking automotive films prepared in Examples 1-3 and Comparative Examples 1-3 were tested for UV transmittance according to GB / T5137.4-2020 "Test Methods for Automotive Safety Glass Part 4: Solar Energy Characteristics Test". The test results are shown in Table 2. Automotive films with a modified substrate thickness of 100 μm and a coating thickness of 50 μm were applied to ordinary flat glass to prepare flat test pieces. The test pieces were 20 cm × 20 cm × 6 mm in size, perpendicular to the incident light beam, and tested three times, with the average value taken.

[0059] The coating thickness of the UV-blocking automotive films prepared in Examples 1-3 and Comparative Examples 1-3 was controlled at 50 μm, and the overall film thickness was 150 μm. A scratch test was performed on the film using a blade, with a scratch depth of 150 μm. The film samples were placed in a constant temperature environment of 25°C for 3 days, and the self-healing performance of the film was analyzed based on the scratch width change rate. The scratch width change rate was calculated using the formula D=(d1-d2) / d1, where D is the scratch width change rate (%), d1 is the initial scratch width (μm), and d2 is the scratch width (μm) after 3 days. Table 1 Square hole sieve aperture / mm Cumulative residue on sieve / % 0.65 ＜3 0.40 40±5 0.25 ＞94 Table 2 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Abrasion resistance (L / μm) 4.25 4.32 4.41 4.24 3.74 3.50 Ultraviolet transmittance (%) 0.51 0.43 0.35 0.80 0.52 1.24 Scratch width change rate (%) 35.8 38.2 42.6 35.5 20.4 35.6 As shown in Table 2, the UV transmittance of the UV-blocking automotive films prepared in Examples 1-3 is in the range of 0.35-0.51%, the abrasion resistance is in the range of 4.25-4.41 L / μm, and the scratch width variation rate is in the range of 35.8-42.6%, indicating that the present invention has excellent UV blocking ability and physical protection ability.

[0060] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a UV-blocking automotive film, characterized in that: Specifically, the steps include the following: Step S1: Disperse the modified filler in tetrahydrofuran, stir and add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and modified coating, and react to obtain a coating solution; Step S2: Clean the surface of the modified substrate with 800-grit sandpaper, apply the coating solution to the modified substrate with a scraper applicator, irradiate with ultraviolet light, turn off the ultraviolet lamp and continue drying for 30-50 minutes to obtain an ultraviolet-blocking car film. The weight ratio of the modified filler, tetrahydrofuran, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and modified coating in step S1 is 10-15:80-90:0.3-0.5:70-85.

2. The method for preparing an ultraviolet-blocking automotive film according to claim 1, characterized in that: The modified substrate is prepared by the following steps: Step A1: Mix and stir 4-amino-3-nitrophenol, hydrochloric acid and deionized water, cool and stir, add sodium nitrite and react to obtain diazonium salt. Mix and stir p-hydroxybenzoic acid, sodium carbonate and ethanol and add diazonium salt to react to obtain intermediate 1. Step A2: Mix and stir intermediate 1, ethanol and sodium hydroxide solution and add sodium dithionite to react and obtain intermediate 2. Mix and stir diisocyanate and N,N-dimethylformamide and add bis(2-hydroxyethyl) disulfide and dibutyltin dilaurate to react. Heat the mixture, add intermediate 2, adjust the pH and react to obtain the pretreated polymer. Step A3: Mix the pretreated polymer, 1-hydroxybenzotriazole and dichloromethane, and add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to react. Heat the mixture, stir, and add 1,2,2,6,6-pentamethylpiperidinol and triethylamine to react and obtain the modified polymer. Heat the modified polymer to melt it, and after mixing and compression, spread it flat on a casting roller, cool and set it, and then pull and wind it into a film to obtain the modified substrate.

3. The method for preparing an ultraviolet-blocking automotive film according to claim 2, characterized in that: The ratio of 4-amino-3-nitrophenol, hydrochloric acid, deionized water, and sodium nitrite in step A1 is 2.5g:4mL:20mL:1.2g, and the molar ratio of p-hydroxybenzoic acid, sodium carbonate, and diazonium salt is 1mmol:2.1-2.2mmol:1.2mmol.

4. The method for preparing an ultraviolet-blocking automotive film according to claim 2, characterized in that: In step A2, the ratio of intermediate 1, ethanol, sodium dithionite and sodium hydroxide solution is 1 mmol: 3-5 mL: 6 mmol: 5 mL, and the molar ratio of isocyanate group on diisocyanate, hydroxyl group on bis(2-hydroxyethyl) disulfide and amino group on intermediate 2 is 1.4: 1.1-1.3: 0.

5.

5. The method for preparing an ultraviolet-blocking automotive film according to claim 2, characterized in that: The ratio of the pretreated polymer, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 1,2,2,6,6-pentamethylpiperidinol and triethylamine in step A3 is 1.2 mmol:1.5 mmol:5-10 mL:1.5 mmol:1 mmol:3 mmol.

6. The method for preparing an ultraviolet-blocking automotive film according to claim 1, characterized in that: The modified filler is prepared by the following steps: Titanium dioxide, tetraethyl orthosilicate and ethanol were mixed and stirred, and mercaptotriethoxysilane was added to carry out the reaction to obtain the modified filler. The ratio of silicon dioxide, tetraethyl orthosilicate, ethanol and mercaptotriethoxysilane is 1g:0.3mL:30mL:0.05g.

7. The method for preparing an ultraviolet-blocking automotive film according to claim 1, characterized in that: The modified coating is prepared by the following steps: Step B1: Mix diisocyanate and N,N-dimethylformamide and add 1,4-butenediol to react. Heat the mixture and add aminopropyl-terminated polydimethylsiloxane to react and obtain the pretreatment coating. Step B2: Mix the pretreatment coating and tetrahydrofuran, stir, and add imidazole-2-carboxaldehyde to initiate the reaction. Zinc chloride and ethanol are added, reacted, and dried to obtain the modified coating.

8. The method for preparing an ultraviolet-blocking automotive film according to claim 7, characterized in that: The ratio of diisocyanate, N,N-dimethylformamide, 1,4-butenediol and aminopropyl-terminated polydimethylsiloxane in step B1 is 0.4 mmol: 2-4 mL: 0.2 mmol: 0.5 mmol.

9. The method for preparing an ultraviolet-blocking automotive film according to claim 7, characterized in that: The ratio of the pretreatment coating, tetrahydrofuran, imidazole-2-carboxaldehyde, zinc chloride and ethanol used in step B2 is 2g:20mL:15mL:0.15g:5mL.

10. A UV-blocking automotive film, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.