A transparent film for automobile glass and its preparation method

Abstract

The present invention relates to the field of membrane material technology, and in particular to a transparent film for automotive glass and a preparation method thereof. The transparent film for automotive glass of the present invention comprises a substrate layer, an adhesive layer and a release layer, wherein the adhesive layer is prepared by thermal curing of an aqueous self-repairing polyurethane emulsion. The aqueous self-repairing polyurethane emulsion is obtained by emulsification polymerization of polytetramethylene ether glycol, isophorone diisocyanate and functionalized nano-silica under the catalysis of dibutyltin dilaurate; the functionalized nano-silica is prepared by olefinic modification, thiol click reaction and disulfide bond exchange reaction. The transparent film of the present invention has high light transmittance, low haze, excellent mechanical strength and stable self-repairing performance, and solves the problem of optical performance attenuation of the polyurethane self-repairing system constructed by disulfide bonds after multiple repairs.

Description

Technical Field

[0001] The present invention relates to the technical field of film materials, and in particular to a transparent film for automobile glass and a preparation method thereof. Background Art

[0002] With the development of the automotive industry, functional requirements for automotive glass are increasing. Traditional automotive glass protective materials primarily focus on basic properties such as impact resistance and UV protection. For example, patent CN104149453B discloses a UV-blocking window film. This invention comprises an anti-scratch layer, a polyester or polyethylene film substrate, a UV-blocking pressure-sensitive adhesive layer, and a release film, all integrated into a single layer. While this window film provides long-lasting UV protection, it is subject to damage from scratches and other factors during actual use, which can affect its long-term performance.

[0003] The emergence of self-healing materials has provided new solutions for addressing surface micro-damage. Among them, self-healing polyurethane materials based on dynamic covalent bonds have attracted widespread attention due to their reversible crosslinking properties. For example, patent CN119798743A discloses a self-healing polyurethane film containing disulfide and DA bonds and a method for preparing the same. By introducing dynamic disulfide bonds into the polyurethane, this invention achieves superior mechanical properties and self-healing performance.

[0004] However, there are obvious defects in practical applications: first, the optical properties (light transmittance, haze) of the material decrease significantly after multiple repair cycles, which is mainly due to the uncontrollable migration and oxidation side reactions of disulfide bonds during the breakage-recombination process; second, the introduction of nanofillers often leads to increased light scattering, affecting transparency; third, the interface bonding strength between the material and the substrate is insufficient, and stratification problems are prone to occur after long-term use. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a transparent film for automotive glass and a preparation method thereof, so as to solve the problem of optical performance degradation after multiple repairs in the polyurethane self-repairing system constructed by disulfide bonds.

[0006] Based on the above purpose, the present invention provides a transparent film for automotive glass, which includes a substrate layer, an adhesive layer and a release layer; the adhesive layer is obtained by coating a water-based functional polyurethane emulsion on the surface of a release film and then thermally curing it.

[0007] Preferably, the preparation steps of the water-based self-repairing polyurethane emulsion are as follows:

[0008] Under the catalysis of dibutyltin dilaurate, polytetramethylene ether glycol and isophorone diisocyanate react to obtain a prepolymer, followed by the addition of dimethylolpropionic acid and functionalized nano-silica, and finally triethylamine and N,N-dimethylformamide, and deionized water for emulsion polymerization;

[0009] Preferably, the weight ratio of the polytetramethylene ether glycol, isophorone diisocyanate, dibutyltin dilaurate, functionalized nano-silica, dimethylolpropionic acid, triethylamine, N,N-dimethylformamide, and deionized water is 10g:4.7-5.1g:0.2-0.3g:4-6g:0.7-0.9g:0.5g:15-18g:70-90g.

[0010] Preferably, the molecular weight of the polytetramethylene ether glycol is 2000.

[0011] Preferably, the prepolymerization temperature is 80-85° C., and the polymerization time is 2-3 hours.

[0012] Preferably, the emulsification temperature is 35-40°C.

[0013] Preferably, the preparation steps of the functionalized nano-silica are as follows:

[0014] S1: reacting nano-silica with silane coupling agent KH-570 to obtain olefinated nano-silica;

[0015] S2: Under the action of a photoinitiator, olefinated nano-silica undergoes an olefin-thiol click reaction with trimethylolpropane tris(3-mercaptopropionate) and dimethyldiallylammonium chloride to obtain thiol-terminated nano-silica;

[0016] S3: The thiol-terminated nano-silica undergoes a thiol-disulfide exchange reaction with 4,4'-diaminodiphenyl disulfide to obtain functionalized nano-silica.

[0017] Preferably, the weight ratio of the nano-silica to the silane coupling agent KH-570 in step S1 is 10-15 g:0.1-0.15 g.

[0018] Preferably, the particle size of the nano-silica in step S1 is 50-100 nm.

[0019] Preferably, in step S2, the weight ratio of the photoinitiator, olefinic nano-silica, trimethylolpropane tris(3-mercaptopropionate), and dimethyldiallylammonium chloride is 20-25 mg:10-12 g:20-24 g:6-7.2 g.

[0020] Preferably, the photoinitiator is photoinitiator 1173.

[0021] Preferably, in step S3, the weight ratio of N-bromosuccinimide, thiol-terminated nano-silica, and 4,4'-diaminodiphenyl disulfide is 0.5-0.6 g: 10-12 g: 2.8-4 g.

[0022] Furthermore, the present invention also provides a method for preparing a transparent film for automotive glass, comprising uniformly coating a water-based self-healing polyurethane emulsion on a release film, drying the film in an oven at 60°C to a constant weight, covering the adhesive surface with a polyester PET film, and curing the film for 24 hours to obtain a transparent film for automotive glass.

[0023] Beneficial effects of the present invention:

[0024] The present invention establishes a stable interface connection on the surface of nano-silica through double modification with a silane coupling agent, which not only ensures the uniform dispersion of nanoparticles, but also realizes effective stress transmission through covalent bonding. Secondly, the introduction of dynamic disulfide bonds constructs a reversible cross-linking network, which enables the material to achieve self-repair through the rearrangement of molecular chains during the repair process. At the same time, the functionalized silica has a positioning and anti-slip effect by being fixed in the cross-linking network of polyurethane. The rigid aromatic ring structure of 4,4'-diaminodiphenyl disulfide can inhibit the excessive migration of molecular chains during the repair process. This design maintains the reversibility of the dynamic bond and inhibits the excessive migration of molecular chains, solving the problem of optical performance degradation of traditional self-healing materials after multiple repairs.

[0025] The present invention uses dimethyl diallyl ammonium chloride and olefinic nano-silica for cross-linking. On the one hand, cross-linking is achieved; on the other hand, the provided quaternary ammonium salt can expand and swell in an aqueous system through hydrophilicity and ionic interaction, thereby promoting the interpenetration and grafting of polyurethane molecular chains. At the same time, its cationic properties may enhance the interfacial bonding strength between the material and the substrate through electrostatic interaction, so that the polyurethane emulsion has good film-forming properties and interfacial bonding strength. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0027] The average particle size of the nano-silicon dioxide used in the examples and comparative examples of the present invention is 50-100 nm.

[0028] Example 1: A transparent film for automobile glass, the specific preparation steps are as follows:

[0029] (1) 10 g of nano-silica and 5 mol / L sodium hydroxide solution were mixed and kept at 80 ° C for 12 h. The reactant was then filtered, and the resulting precipitate was washed with deionized water and dried. The resulting product, 300 mL of anhydrous ethanol and 0.1 g of KH-570 were then mixed and ultrasonically dispersed for 30 min. The mixture was stirred continuously at 70 ° C for 6 h. After the reaction was completed, the product was dried at 90 ° C to constant weight to obtain olefinated nano-silica.

[0030] (2) At room temperature, 10 g of olefinated nano-silica, 20 g of trimethylolpropane tris(3-mercaptopropionate), and 6 g of dimethyldiallylammonium chloride were added to 150 mL of tetrahydrofuran solution. Subsequently, 20 mg of photoinitiator 1173 was added to the reaction system. After mixing evenly, the mixture was placed under 365 nm ultraviolet light for 2 h. The product was centrifuged, washed, and dried in a vacuum drying oven at 50 ° C to constant weight to obtain thiol-terminated nano-silica.

[0031] (3) 2.8 g of 4,4'-diaminodiphenyl disulfide and 100 mL of 1,4-dioxane were mixed, 0.5 g of N-bromosuccinimide was added and stirred evenly; then 10 g of thiol-terminated nano-silica was added to the reaction system, stirred evenly, and reacted at 25 °C for 5 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain functionalized nano-silica;

[0032] (4) 10 g of polytetramethylene ether glycol (Mn is 2000), 4.7 g of isophorone diisocyanate and 0.2 g of dibutyltin dilaurate were mixed and reacted at 80 ° C for 2 h. Then, the reaction temperature was controlled at 60 ° C, 4 g of functionalized nano-silica and 0.7 g of dihydroxymethylpropionic acid were added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 15 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 35 ° C, and 70 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0033] (5) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0034] Example 2: A transparent film for automobile glass, the specific preparation steps are as follows:

[0035] (1) 13 g of nano-silica and 5 mol / L sodium hydroxide solution were mixed and kept at 80 ° C for 12 h. The reactant was then filtered, and the resulting precipitate was washed with deionized water and dried. The resulting product, 350 mL of anhydrous ethanol and 0.13 g of KH-570 were then mixed and ultrasonically dispersed for 30 min. The mixture was stirred continuously at 70 ° C for 6 h. After the reaction was completed, the product was dried at 90 ° C to constant weight to obtain olefinated nano-silica.

[0036] (2) At room temperature, 11 g of olefinated nano-silica, 22 g of trimethylolpropane tris(3-mercaptopropionate), and 6.6 g of dimethyldiallylammonium chloride were added to 180 mL of tetrahydrofuran solution. Subsequently, 23 mg of photoinitiator 1173 was added to the reaction system. After mixing evenly, the mixture was placed under 365 nm ultraviolet light for 2 h. The product was centrifuged, washed, and dried in a vacuum drying oven at 50 ° C to constant weight to obtain thiol-terminated nano-silica.

[0037] (3) 3.4 g of 4,4'-diaminodiphenyl disulfide and 130 mL of 1,4-dioxane were mixed, 0.55 g of N-bromosuccinimide was added and stirred evenly; then 11 g of thiol-terminated nano-silica was added to the reaction system, stirred evenly, and reacted at 28 °C for 6 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain functionalized nano-silica;

[0038] (4) 10 g of polytetramethylene ether glycol (Mn is 2000), 4.9 g of isophorone diisocyanate and 0.25 g of dibutyltin dilaurate were mixed and reacted at 83 ° C for 2 h. Then, the reaction temperature was controlled at 60 ° C, 5 g of functionalized nano-silica and 0.8 g of dihydroxymethylpropionic acid were added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 16 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 38 ° C, and 80 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0039] (5) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0040] Example 3: A transparent film for automobile glass, the specific preparation steps are as follows:

[0041] (1) 15 g of nano-silica and 5 mol / L sodium hydroxide solution were mixed and kept at 80 ° C for 12 h. The reactant was then filtered, and the resulting precipitate was washed with deionized water and dried. The resulting product, 400 mL of anhydrous ethanol and 0.15 g of KH-570 were then mixed and ultrasonically dispersed for 30 min. The mixture was stirred continuously at 70 ° C for 7 h. After the reaction was completed, the product was dried at 90 ° C to constant weight to obtain olefinated nano-silica.

[0042] (2) At room temperature, 12 g of olefinated nano-silica, 24 g of trimethylolpropane tris(3-mercaptopropionate), and 7.2 g of dimethyldiallylammonium chloride were added to 200 mL of tetrahydrofuran solution. Subsequently, 25 mg of photoinitiator 1173 was added to the reaction system. After mixing evenly, the mixture was placed under 365 nm ultraviolet light for 3 h. The product was centrifuged, washed, and dried in a vacuum drying oven at 50 ° C to constant weight to obtain thiol-terminated nano-silica.

[0043] (3) 4 g of 4,4'-diaminodiphenyl disulfide and 150 mL of 1,4-dioxane were mixed, 0.6 g of N-bromosuccinimide was added and stirred evenly; then 12 g of thiol-terminated nano-silica was added to the reaction system, stirred evenly, and reacted at 30 ° C for 7 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain functionalized nano-silica;

[0044] (4) 10 g of polytetramethylene ether glycol (Mn is 2000), 5.1 g of isophorone diisocyanate and 0.3 g of dibutyltin dilaurate were mixed and reacted at 85 ° C for 3 h. Then, the reaction temperature was controlled at 60 ° C, 6 g of functionalized nano-silica and 0.7-0.9 g of dihydroxymethylpropionic acid were added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 18 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 40 ° C, and 90 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0045] (5) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0046] Comparative Example 1: The difference from Example 2 is that the polyurethane is not modified, and the remaining steps are the same as Example 2. The specific steps are as follows:

[0047] (1) 10 g of polytetramethylene ether glycol (Mn is 2000), 4.9 g of isophorone diisocyanate and 0.25 g of dibutyltin dilaurate were mixed and reacted at 83 ° C for 2 h. Then, the reaction temperature was controlled at 60 ° C, 0.8 g of dihydroxymethylpropionic acid was added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 16 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 38 ° C, and 80 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0048] (2) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0049] Comparative Example 2: The difference from Example 2 is that the functionalized nano-silica is replaced by a mixture of silica and 4,4'-diaminodiphenyl disulfide. The remaining steps are the same as Example 2. The specific steps are as follows:

[0050] (1) 10 g of polytetramethylene ether glycol (Mn is 2000), 4.9 g of isophorone diisocyanate and 0.25 g of dibutyltin dilaurate were mixed and reacted at 83 ° C for 2 h. Then, the reaction temperature was controlled at 60 ° C, 3.82 g of nano-silica, 1.18 g of 4,4'-diaminodiphenyl disulfide and 0.8 g of dihydroxymethylpropionic acid were added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 16 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 38 ° C, and 80 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0051] (2) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0052] Comparative Example 3: The difference from Example 2 is that 4,4'-diaminodiphenyl disulfide is replaced by cystamine, and the remaining steps are the same as Example 2. The specific steps are as follows:

[0053] (1) 13 g of nano-silica and 5 mol / L sodium hydroxide solution were mixed and kept at 80 ° C for 12 h. The reactant was then filtered, and the resulting precipitate was washed with deionized water and dried. The resulting product, 350 mL of anhydrous ethanol and 0.13 g of KH-570 were then mixed and ultrasonically dispersed for 30 min. The mixture was stirred continuously at 70 ° C for 6 h. After the reaction was completed, the product was dried at 90 ° C to constant weight to obtain olefinated nano-silica.

[0054] (2) At room temperature, 11 g of olefinated nano-silica, 22 g of trimethylolpropane tris(3-mercaptopropionate), and 6.6 g of dimethyldiallylammonium chloride were added to 180 mL of tetrahydrofuran solution. Subsequently, 23 mg of photoinitiator 1173 was added to the reaction system. After mixing evenly, the mixture was placed under 365 nm ultraviolet light for 2 h. The product was centrifuged, washed, and dried in a vacuum drying oven at 50 ° C to constant weight to obtain thiol-terminated nano-silica.

[0055] (3) 3.4 g of cystamine and 130 mL of 1,4-dioxane were mixed, 0.55 g of N-bromosuccinimide was added and stirred evenly; then 11 g of thiol-terminated nano-silica was added to the reaction system, stirred evenly, and reacted at 28 ° C for 6 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain functionalized nano-silica;

[0056] (4) 10 g of polytetramethylene ether glycol (Mn is 2000), 4.9 g of isophorone diisocyanate and 0.25 g of dibutyltin dilaurate were mixed and reacted at 83 ° C for 2 h. Then, the reaction temperature was controlled at 60 ° C, 5 g of functionalized nano-silica and 0.8 g of dihydroxymethylpropionic acid were added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 16 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 38 ° C, and 80 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0057] (5) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0058] Comparative Example 4: The difference from Example 2 is that dimethyldiallylammonium chloride is replaced with 1,5-hexadiene, and the remaining steps are the same as Example 2. The specific steps are as follows:

[0059] (1) 13 g of nano-silica and 5 mol / L sodium hydroxide solution were mixed and kept at 80 ° C for 12 h. The reactant was then filtered, and the resulting precipitate was washed with deionized water and dried. The resulting product, 350 mL of anhydrous ethanol and 0.13 g of KH-570 were then mixed and ultrasonically dispersed for 30 min. The mixture was stirred continuously at 70 ° C for 6 h. After the reaction was completed, the product was dried at 90 ° C to constant weight to obtain olefinated nano-silica.

[0060] (2) At room temperature, 11 g of olefinated nano-silica, 22 g of trimethylolpropane tris(3-mercaptopropionate), and 6.6 g of 1,5-hexadiene were added to 180 mL of tetrahydrofuran solution. Subsequently, 23 mg of photoinitiator 1173 was added to the reaction system. After mixing evenly, the mixture was placed under 365 nm ultraviolet light for 2 h. The product was centrifuged, washed, and dried in a vacuum drying oven at 50 ° C to constant weight to obtain thiol-terminated nano-silica.

[0061] (3) 3.4 g of 4,4'-diaminodiphenyl disulfide and 130 mL of 1,4-dioxane were mixed, 0.55 g of N-bromosuccinimide was added and stirred evenly; then 11 g of thiol-terminated nano-silica was added to the reaction system, stirred evenly, and reacted at 28 °C for 6 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain functionalized nano-silica;

[0062] (4) 10 g of polytetramethylene ether glycol (Mn is 2000), 4.9 g of isophorone diisocyanate and 0.25 g of dibutyltin dilaurate were mixed and reacted at 83 ° C for 2 h. Then, the reaction temperature was controlled at 60 ° C, 5 g of functionalized nano-silica and 0.8 g of dihydroxymethylpropionic acid were added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 16 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 38 ° C, and 80 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0063] (5) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0064] Comparative Example 5: The difference from Example 2 is that there is no nano-silicon dioxide. The remaining steps are the same as Example 2. The specific steps are as follows:

[0065] (1) At room temperature, 22 g of trimethylolpropane tris(3-mercaptopropionate) and 6.6 g of dimethyldiallylammonium chloride were added to 180 mL of tetrahydrofuran solution. Then, 23 mg of photoinitiator 1173 was added to the reaction system, mixed evenly, and placed under 365 nm ultraviolet light for 2 h. The product was precipitated with methanol and dried to constant weight in a vacuum drying oven at 50 ° C. Then, it was mixed with 3.4 g of 4,4'-diaminodiphenyl disulfide and 130 mL of 1,4-dioxane in an ice water bath, and 0.55 g of N-bromosuccinimide was added and stirred evenly. After stirring evenly, the mixture was reacted at 25 ° C for 6 h. After the reaction was completed, it was extracted and purified to obtain a functionalized modified substance.

[0066] (2) 10 g of polytetramethylene ether glycol (Mn is 2000), 4.9 g of isophorone diisocyanate and 0.25 g of dibutyltin dilaurate were mixed and reacted at 83 ° C for 2 h. Then, the reaction temperature was controlled at 60 ° C, 5 g of functionalized modified substance and 0.8 g of dihydroxymethylpropionic acid were added, and the reaction was continued for 2 h. Then, 0.5 g of triethylamine was added at 35 ° C and the reaction was continued for 30 min. Finally, 16 g of N, N-dimethylformamide was added, and deionized water was added to the system. The mixture was stirred and emulsified at 38 ° C, and 80 g of deionized water was added to obtain a water-based self-healing polyurethane emulsion.

[0067] (3) The water-based self-healing polyurethane emulsion was evenly coated on the surface of the release film, and then placed in an oven at 60°C to dry to constant weight. The polyester PET film was then covered on the adhesive surface and cured for 24 hours to obtain a transparent film for automotive glass.

[0068] Performance Testing

[0069] Adhesion: According to GB / T 9286-1998, the cross-hatch method was used for testing. The test results are shown in Table 1.

[0070] Light transmittance and haze test: According to GB / T 2410-2008, the samples obtained in the examples and comparative examples were tested using a spectrophotometer. The test results are shown in Table 1.

[0071] Mechanical properties: According to GB / T 1040.3-2006, a universal material testing machine was used to test at a tensile speed of 50 mm / min, and the tensile strength was calculated. The test results are shown in Table 1.

[0072] Self-repair performance: The samples obtained from the embodiment and the comparative example were subjected to 10 repair cycle tests. The specific steps of each repair were to damage the surface of the sample with a micro scratch depth of 20 μm, and then heat it at 60°C for 30 minutes. After repeating 10 times, the transmittance and haze were tested again. The test results are shown in Table 1.

[0073] Table 1 Performance test results

[0074] Light transmittance (%) Haze (%) Adhesion Tensile strength (MPa) Transmittance / 10 repair cycles (%) Haze / 10 repair cycles (%) Example 1 91.8 1.3 0 43.7 89.5 2.0 Example 2 92.5 1.2 0 45.6 90.1 1.8 Example 3 92.0 1.4 0 44.1 89.8 2.1 Comparative Example 1 84.0 5.2 3 25.2 75.0 8.0 Comparative Example 2 85.5 4.2 2 32.5 78.3 6.8 Comparative Example 3 86.2 3.8 1 35.1 80.1 6.0 Comparative Example 4 89.7 2.4 2 30.5 83.5 4.3 Comparative Example 5 88.0 3.5 1 28.7 82.0 5.5

[0075] Data analysis: From the data of Examples 1-3 in Table 1, it can be seen that the transparent film prepared by the present invention exhibits excellent comprehensive performance. The high transmittance, low haze and high tensile strength indicate that the functionalized nano-silica has achieved nano-level uniform dispersion with the polyurethane matrix. This is due to the fact that during the synthesis of water-based polyurethane, nano-silica can participate in the cross-linking reaction. At the same time, the network containing quaternary ammonium salts on the surface can promote the intercalation and grafting of polyurethane molecular chains by stretching, which not only effectively suppresses the light scattering phenomenon, but also improves the mechanical properties of the film. At the same time, the excellent adhesion performance suggests that the water-based self-healing polyurethane emulsion of the present invention can form a strong electrostatic interaction with the substrate during the film formation process through the cationic properties of dimethyldiallyl ammonium chloride. It is particularly noteworthy that after 10 repair cycles, the transmittance only decayed by 1.7%-2.7%, and the haze growth was controlled at 0.6-0.9 percentage points. This stable self-healing performance may be due to the dynamic reversibility of disulfide bonds. The ability of disulfide bonds to break and recombine enables the material to repeatedly repair microcracks. At the same time, functionalized silica is fixed in the cross-linked network of polyurethane, which has a positioning and anti-slip effect. The rigid aromatic ring structure of 4,4'-diaminodiphenyl disulfide may inhibit the excessive migration of molecular chains during the repair process, solving the problem of optical performance attenuation of the polyurethane self-healing system constructed by disulfide bonds after multiple repairs, thereby maintaining optical uniformity.

[0076] From the comparison of the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that the excellent performance exhibited by Example 2 may be due to its unique multi-level structural design: First, after dual modification of alkenylation and thiolation, nano-silica forms a chemically bonded network structure with the polyurethane matrix. This covalent connection method not only improves the mechanical properties of the material, but also ensures the uniform dispersion of the nanoparticles, thereby effectively reducing light scattering; at the same time, silica can construct a large number of disulfide bonds between the polyurethane cross-linked network, which has a certain break complementary effect, and because it is firmly fixed in the cross-linked network, it can form a certain positioning anti-slip effect, thereby preventing the mutual slip between the disulfide bonds; secondly, the synergistic effect of the rigid aromatic ring structure of the introduced 4,4'-diaminodiphenyl disulfide and the flexible polyurethane chain segment not only maintains the high transparency of the material, but also gives it self-healing ability; furthermore, the cationic properties of dimethyldiallylammonium chloride may enhance the interfacial bonding force between the film and the substrate through electrostatic interaction, thereby achieving synergistic optimization of optical properties, mechanical strength and self-healing function.

[0077] From the data comparison of Example 2 and Comparative Example 2 in Table 1, it can be seen that functionalized nano-silica forms a stable network structure with the polyurethane matrix through chemical bonding. This covalent bonding method not only enhances the interfacial interaction, but also ensures the uniform dispersion of nanoparticles, thereby effectively improving the optical properties of the material. The introduction of dynamic disulfide bonds constructs a reversible cross-linked network, which enables the material to achieve self-repair by rearranging the molecular chains when damaged, while maintaining the integrity of the structure. The addition of cationic monomers may optimize the interfacial bonding performance of the material and the substrate through electrostatic interactions. In contrast, Comparative Example 2 uses a physical mixing method to introduce silica and a cross-linking agent. The lack of chemical bonding between its components results in poor interfacial compatibility, which may affect the dispersion state and stress transfer efficiency of the nanoparticles, thereby reducing the overall performance of the material.

[0078] A comparison of the data in Example 2 and Comparative Example 3 in Table 1 shows that the rigid aromatic ring structure of 4,4'-diaminodiphenyl disulfide, used as a crosslinker, likely stabilizes the dynamic disulfide bond exchange process through steric hindrance, preventing disulfide bond slippage during the breakage and recombination process during multiple repairs. Simultaneously, it forms stable π-π stacking interactions with the polyurethane molecular chains. This synergistic effect of intermolecular forces ensures both structural stability during the repair process and uniformity of optical properties. In contrast, the flexible fatty chain structure of cystamine, used as a crosslinker in Comparative Example 3, may lead to excessive migration of molecular segments during the repair process, thus affecting the optical stability of the repaired material.

[0079] From the comparison of the performance data of Example 2 and Comparative Example 4 in Table 1, it can be seen that the role of dimethyl diallyl ammonium chloride is cross-linking on the one hand, and on the other hand, the quaternary ammonium salt provided can stretch and expand in the aqueous system through hydrophilicity and ionic interactions, which on the one hand enables the waterborne polyurethane molecular chain to penetrate into the interior, and on the other hand improves the binding of isocyanate and amino groups. At the same time, its cationic properties may enhance the interfacial bonding strength between the material and the substrate through electrostatic interaction. In contrast, Comparative Example 4 uses 1,5-hexadiene as a cross-linking agent, and its non-ionic properties may lead to a decrease in interfacial bonding strength. At the same time, the lack of electrostatic interaction of cationic groups may affect the uniform film-forming performance of the material.

[0080] From the data comparison of Example 2 and Comparative Example 5 in Table 1, it can be seen that the functionalized nano-silica forms a stable organic-inorganic hybrid network with the polyurethane matrix through chemical bonding. This structure may improve the mechanical properties of the material through the rigidity enhancement effect and stress transfer mechanism of the nanoparticles; at the same time, the uniform dispersion of nano-silica may reduce light scattering through the refractive index matching effect, thereby improving the optical properties of the material; the introduction of dynamic disulfide bonds constructs a reversible cross-linked network, allowing the material to achieve self-repair through the rearrangement of molecular chains during the repair process. In contrast, Comparative Example 5 lacks the reinforcing effect of nano-silica, and its molecular network structure may exhibit lower rigidity and stability, which may lead to stress concentration and optical inhomogeneity; at the same time, the lack of interfacial interaction of nanoparticles may affect the reversible exchange efficiency of the dynamic bond, thereby failing to form a synergistic effect with 4,4'-diaminodiphenyl disulfide.

[0081] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A transparent film for automobile glass, comprising a substrate layer, an adhesive layer and a release layer, characterized in that: The adhesive layer is obtained by coating a water-based functional polyurethane emulsion on the surface of the release film and then thermally curing it; The preparation steps of the water-based self-repairing polyurethane emulsion are as follows: Under the catalysis of dibutyltin dilaurate, polytetramethylene ether glycol and isophorone diisocyanate react to obtain a prepolymer, followed by the addition of dimethylolpropionic acid and functionalized nano-silica, and finally triethylamine and N,N-dimethylformamide, and deionized water for emulsion polymerization; The preparation steps of the functionalized nano-silica are as follows: S1: reacting nano-silica with silane coupling agent KH-570 to obtain olefinated nano-silica; S2: Under the action of a photoinitiator, olefinated nano-silica undergoes an olefin-thiol click reaction with trimethylolpropane tris(3-mercaptopropionate) and dimethyldiallylammonium chloride to obtain thiol-terminated nano-silica; S3: Under the action of N-bromosuccinimide, the thiol-terminated nano-silica undergoes a thiol-disulfide exchange reaction with 4,4'-diaminodiphenyl disulfide to obtain functionalized nano-silica; The weight ratio of nano-silica and silane coupling agent KH-570 in step S1 is 10-15g:0.1-0.15g; The weight ratio of the photoinitiator, olefinic nano-silica, trimethylolpropane tris(3-mercaptopropionate), and dimethyldiallylammonium chloride in step S2 is 20-25 mg:10-12 g:20-24 g:6-7.2 g; In step S3, the weight ratio of N-bromosuccinimide, thiol-terminated nano-silica, and 4,4'-diaminodiphenyl disulfide is 0.5-0.6 g: 10-12 g: 2.8-4 g.

2. The transparent film according to claim 1, characterized in that The weight ratio of the polytetramethylene ether glycol, isophorone diisocyanate, dibutyltin dilaurate, functionalized nano-silica, dihydroxymethylpropionic acid, triethylamine, N,N-dimethylformamide and deionized water is 10g:4.7-5.1g:0.2-0.3g:4-6g:0.7-0.9g:0.5g:15-18g:70-90g.

3. The transparent film according to claim 1, characterized in that The molecular weight of the polytetramethylene ether glycol is 2000.

4. The transparent film according to claim 1, wherein The prepolymerization temperature is 80-85°C, and the polymerization time is 2-3 hours; the emulsification temperature is 35-40°C.

5. The transparent film according to claim 1, characterized in that The particle size of the nano-silica in step S1 is 50-100 nm.

6. A method for preparing a transparent film for automobile glass according to any one of claims 1 to 5, characterized in that: The following steps are involved: The water-based self-repairing polyurethane emulsion is evenly coated on the release film and dried to a constant weight. The adhesive surface is then covered with a polyester PET film and cured to obtain a transparent film for automotive glass.