A tunable ultraviolet shielding and blue light absorbing tung oil-based film or coating, and a preparation method and application thereof

Abstract

An ultraviolet shielding and blue light absorption adjustable tung oil-based film or coating, and a preparation method and application thereof. The film or coating is prepared by reacting an aldehyde group-containing aryloxy triazine monomer, a bridged amine monomer containing primary amine and secondary amine, and a tung oil-maleic anhydride adduct, wherein the aldehyde group condenses with the primary amine to form a dynamic imine bond, and the secondary amine ring-opening with the anhydride to form an amide acid structure, forming a cross-linked network containing triazine rigid units, dynamic imine bonds and tung oil flexible segments. The material can be formed into a film by solution casting, blade coating, spin coating, spraying or casting, and can realize full shielding of the 200-400 nm ultraviolet wave band, continuous adjustable light absorption rate of the 400-500 nm blue light wave band, and high transparency in the 500-800 nm visible light region, meeting the differentiated needs of different application scenarios for blue light management.

Description

Technical Field

[0001] This invention belongs to the field of bio-based dynamic covalent polymer materials, specifically relating to the field of optically modulated functional thin films or coatings, and particularly to a tung oil-based thin film or coating with adjustable ultraviolet shielding and blue light absorption, its preparation method, and its application. Background Technology

[0002] Transparent polymer films and coatings play an increasingly important role in display devices, architectural window films, automotive window films, electronic device packaging, optical component protection, and agricultural covering. These materials are often exposed to sunlight for extended periods during practical use, and ultraviolet (UV) and high-energy blue light from sunlight are the main causes of polymer aging. UV light causes polymer chain breakage and cross-linking, leading to material embrittlement, yellowing, and deterioration of mechanical properties, ultimately resulting in loss of protective function. High-energy blue light poses a potential hazard to the human retina and also accelerates the degradation of organic photosensitive materials. Therefore, developing transparent protective materials with both UV and blue light modulation capabilities has significant application value.

[0003] The mainstream technical approach to achieving UV and blue light protection currently involves physically adding small-molecule UV absorbers or inorganic nanoparticles, such as benzotriazoles, benzophenones, hydroxyphenyltriazine compounds, and zinc oxide and titanium dioxide nanoparticles, to a polymer matrix. While this type of blending is relatively simple, it has inherent drawbacks. The lack of covalent bonding between the small-molecule absorbers and the polymer matrix makes them prone to migration, volatilization, and precipitation during long-term use, leading to a gradual decline in protective performance. Furthermore, the precipitates may contaminate the contact interface. Nano-inorganic fillers, on the other hand, suffer from poor dispersion uniformity and agglomeration. High addition levels significantly increase film haze and reduce transmittance. Additionally, the poor interfacial compatibility between inorganic particles and the organic matrix makes them prone to stress concentration points under external forces, weakening the material's mechanical properties. Moreover, most existing technologies focus only on UV protection, with limited ability to regulate blue light absorption, making it difficult to meet the differentiated control requirements for blue light transmittance in various application scenarios. Some solutions attempt to achieve wideband modulation by stacking multiple functional coatings, but the process is complex, the cost is high, and the stability of the interlayer interface is difficult to guarantee.

[0004] 1,3,5-Triazine aromatic compounds, due to their rigid aromatic ring structure, possess excellent thermal stability and UV absorption properties, attracting researchers' attention in recent years. Existing literature reports the introduction of hydroxyphenyl triazine compounds into petroleum-based epoxy or phenoxy resin systems to improve the UV shielding capability of the materials. However, these approaches are still mainly based on physical blending, and the triazine component is not covalently bonded into the polymer network, thus the long-term stability problem remains unresolved. Furthermore, these systems rely on traditional epoxy-amine high-temperature curing processes, making it difficult to introduce bio-based flexible segments to balance the material's rigidity and toughness, and also hindering solution processing to form films under mild conditions. Moreover, reversible depolymerization of the crosslinked network and material regeneration are difficult to achieve.

[0005] Tung oil, a renewable vegetable oil abundant in my country, contains multiple conjugated double bonds in its molecular structure. Multifunctional bio-based intermediates can be prepared via the Diels-Alder addition reaction of maleic anhydride. Tung oil-based polymers typically exhibit excellent flexibility, hydrophobicity, and film-forming properties, and their applications in coatings and adhesives have been explored. However, pure tung oil-based systems lack rigid aromatic structural units, resulting in lower mechanical strength and modulus. Furthermore, the absence of strong ultraviolet chromophores in the molecular structure limits intrinsic ultraviolet light absorption, making it difficult to meet the requirements of high-performance optical protection materials on its own.

[0006] In view of the problems existing in the above-mentioned prior art, such as easy migration of functional components, the influence of inorganic fillers on optical quality, insufficient blue light modulation ability, non-recyclable cross-linked networks, and low bio-based content, there is an urgent need in this field to develop a new material system that can stably anchor rigid functional units to polymer networks in a covalent manner, while introducing flexible segments from biomass. Summary of the Invention

[0007] Technical Problem Solved: To address the technical problems in existing UV and blue light protection materials, such as the easy migration and precipitation of small molecule functional components leading to decreased protective performance, the impact of inorganic nanofillers on light transmittance and increased haze, and the waste of resources due to the non-recyclability of cross-linked networks, this invention provides a tung oil-based film or coating with adjustable UV shielding and blue light absorption, its preparation method, and its application. This material forms a cross-linked network by reacting aldehyde-containing aryloxytriazine monomers, bridged amine monomers containing primary and secondary amines, and tung oil-maleic anhydride adducts. This allows the triazine chromophores to be covalently fixed in the network to achieve stable optical protection, while also possessing excellent mechanical properties and recyclability.

[0008] Technical Solution: A method for preparing a tung oil-based thin film or coating with adjustable ultraviolet shielding and blue light absorption, comprising the following steps: reacting tung oil with maleic anhydride at a molar ratio of 1:(0.5~5.0) at 100~180℃ for 2~10h to obtain a tung oil-maleic anhydride adduct; reacting cyanuric chloride, an aromatic aldehyde containing phenolic hydroxyl groups, and an acid-binding agent at a molar ratio of 1:(2.4~3.6):(2.4~3.6) at 50~80℃ for 5~10h. h, an aldehyde-containing aryloxytriazine compound is obtained; the aldehyde-containing aryloxytriazine compound is reacted with a bridged amine monomer in an organic solvent, wherein the equivalent ratio of the aldehyde group of the aldehyde-containing aryloxytriazine compound to the primary amine group of the bridged amine monomer is 1:(0.7~1.3), the reaction temperature is 20~100℃, and the reaction time is 0.5~6h, so that the aldehyde group and the primary amine group condense to form an imine bond, and an intermediate retaining a secondary amine group is obtained. The molecular structure of the bridged amine monomer contains at least one primary amine group and at least one secondary amine group; the intermediate is reacted with a tung oil-maleic anhydride adduct at a mass ratio of 1:(1~6) at 40~120℃ for 1~6h, so that the secondary amine group and the anhydride group undergo a ring-opening reaction to form an amide acid structure, and a film-forming liquid is obtained; the film-forming liquid is used to form a film by solution casting, blade coating, spin coating, spraying, or casting, and then dried and cured to obtain the film or coating.

[0009] The above-mentioned aldehyde-containing aryloxy triazine compound is 2,4,6-trisubstituted-1,3,5-triazine, wherein each of the three substituents is independently selected from aldehyde-containing or non-aldehyde-containing aryloxy groups, and at least one substituent is an aldehyde-containing aryloxy group; the aldehyde-containing aryloxy group is provided by vanillin, eugenol, p-hydroxybenzaldehyde, o-vanillin, salicylaldehyde, or isovanillin.

[0010] The bridged amine monomer described above has the structure shown in H2N-R1-NH-R2, wherein R1 is a C2-C12 alkylene group or a C2-C8 divalent segment containing an ether bond, and R2 is a C1-C8 alkyl, hydroxyalkyl, benzyl, or a substituent containing an ether chain; the bridged amine monomer is selected from at least one of N-methyl-1,3-propanediamine, N-ethyl-1,3-propanediamine, N-propyl-1,3-propanediamine, N-isopropyl-1,3-propanediamine, N-butyl-1,3-propanediamine, N-methyl-1,2-ethylenediamine, N-methyl-1,4-butanediamine, N-methyl-1,6-hexanediamine, N-(2-hydroxyethyl)-1,3-propanediamine, or a polyetheramine having at least one primary amine group and at least one secondary amine group.

[0011] The acid-binding agent is selected from at least one of anhydrous calcium carbonate, anhydrous potassium carbonate, sodium carbonate, and sodium bicarbonate; the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

[0012] The molar ratio of tung oil to maleic anhydride is 1:(2~4), and the reaction temperature is 120~160℃; the molar ratio of cyanuric chloride to phenolic hydroxy aromatic aldehyde is 1:(2.8~3.2); and the mass ratio of the intermediate to the tung oil-maleic anhydride adduct is 1:(2~5).

[0013] The solid content of the above film-forming solution is 5wt.%~20wt.%, and the drying and curing are carried out in stages at 20~120℃ for 6~72h.

[0014] The tung oil-based thin film or coating with adjustable ultraviolet shielding and blue light absorption prepared by the above preparation method has an ultraviolet light transmittance of not more than 1% in the 200~400nm wavelength band, a visible light transmittance of not less than 80% in the 500~800nm ​​wavelength band, and a thickness of 10~1000μm.

[0015] The transmittance of the aforementioned film or coating in the 400-500nm wavelength band can be adjusted by changing the mass ratio of the aldehyde-containing aryloxytriazine compound to the tung oil-maleic anhydride adduct or the film thickness. As the mass ratio of the two increases, the transmittance of the film in the 400-500nm wavelength band decreases.

[0016] The aforementioned films or coatings can be reshaped by hot pressing; in an acidic aqueous medium, the imine bonds can dissociate, allowing the aldehyde-containing aryloxytriazine compounds to be separated and recovered from the tung oil-derived components.

[0017] The aforementioned films or coatings are used in transparent ultraviolet protection, blue-violet light modulation, display screen protection, lighting device protection, architectural window film, automotive window film, greenhouse covering, agricultural covering, outdoor weather-resistant coatings, packaging materials, photothermal response, thermal management, flexible electronic packaging, or optical component protection.

[0018] Beneficial Effects: This invention constructs a cross-linked network with aldehyde-containing aryloxytriazine monomers, bridged amine monomers containing primary and secondary amines, and tung oil maleic anhydride adducts through dynamic imine bonds and ammonic acid structures. The triazine chromophores are covalently embedded in the polymer backbone, fundamentally avoiding the problem of functional component migration and precipitation in traditional blending schemes, thus ensuring the long-term stability of optical protection performance. Unlike existing technologies that rely solely on physically adding UV absorbers, this invention utilizes a conjugated light-absorbing system composed of intramolecular triazine rings, aromatic rings, methoxy groups, and imine bonds to achieve complete shielding of the 200–400 nm UV band. Simultaneously, by adjusting the ratio of rigid triazine units to flexible tung oil segments and the film thickness, the absorbance in the 400–500 nm blue light band can be continuously adjusted over a wide range, while maintaining high transparency in the 500–800 nm visible light region, meeting the differentiated blue light management needs of various application scenarios. The presence of dynamic imine bonds in the cross-linked network endows the material with intrinsic photothermal response properties, enabling non-radiative energy conversion without the need for additional photothermal fillers. More importantly, the mechanical strength provided by the rigid triazine aromatic structure and the flexibility imparted by the long fatty chains of tung oil form a synergistic complement. By adjusting their ratio, the tensile strength and elongation at break of the film can be effectively balanced, while maintaining low haze and excellent optical transparency. Furthermore, the reversible exchange properties of the dynamic imine bonds allow the cross-linked network to undergo stress relaxation and network rearrangement under hot-pressing conditions, enabling multiple reshaping processes. In acidic aqueous media, the imine bonds selectively break, allowing for the separate recovery of the aldehyde-containing triazine monomer and tung oil component, achieving closed-loop recycling of the thermosetting polymer material. These performance advantages make this material promising for applications in various fields such as transparent UV protection, blue light modulation, architectural and automotive window films, flexible electronic packaging, and outdoor weather-resistant coatings. Attached Figure Description

[0019] Figure 1 Infrared spectra of TOMA, TVT, TVT-MAPA (a) and Examples 5-8 and Comparative Examples 1-2 (b).

[0020] Figure 2 The UV absorbance of TOMA, TVT, and TVT-MAPA monomers is shown in (a), and the UV-Vis transmission spectra of Examples 4-9 are shown in (b).

[0021] Figure 3 Examples 5-8 show the swelling degree (a) and gel content (b) in different solvents.

[0022] Figure 4 The surface temperature changes in Examples 5-8 were recorded in real time during 365 nm ultraviolet irradiation.

[0023] Figure 5This is a surface SEM image of Example 6 after UV aging at 340 nm. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, and not all embodiments.

[0025] Example 1

[0026] Preparation of tung oil-maleic anhydride adduct (TOMA): 0.02 mol of tung oil (AV = 180 mg KOH / g) and 0.1 mol of maleic anhydride were added to a reactor equipped with a mechanical stirrer, thermometer, and inert gas interface. After purging the reactor with nitrogen, the system was heated to 130℃ and stirred for 6 h. After the reaction was complete, the mixture was cooled to room temperature, and excess maleic anhydride was removed by ethyl acetate extraction. The mixture was dried over anhydrous magnesium sulfate, and most of the ethyl acetate was removed by rotary evaporation. Finally, the tung oil-maleic anhydride adduct, denoted as TOMA, was obtained by vacuum drying, with the following structural formula:

[0027]

[0028] Example 2

[0029] Preparation of vanillin-based triazine trialdehyde (TVT): 0.1 mol cyanuric chloride, 0.45 mol vanillin, and 0.45 mol anhydrous calcium carbonate were added to 300 mL acetone under a nitrogen atmosphere. The initial temperature of the system was controlled at 0–5 °C. After reacting at low temperature for 3 h, the temperature was raised to 65 °C and stirred for 6 h. After cooling the reaction solution to room temperature, the mixture was filtered and the acetone was completely removed under reduced pressure. The solid was washed five times with hot deionized water to remove residual vanillin and inorganic salts. After filtration, the solid was placed in a vacuum drying oven and dried under vacuum at 80 °C for 12 h to obtain the target TVT monomer, with the following structural formula:

[0030]

[0031] Example 3

[0032] Preparation of TVT-MAPA intermediate containing dynamic imine bonds: 10g of TVT from Example 2 was uniformly dispersed in 30mL LDM, 5g of N-methyl-1,3-propanediamine (MAPA) and an appropriate amount of 4A molecular sieve were added, and the reaction was carried out at 50℃ for 2 h to obtain a TVT-MAPA intermediate containing dynamic imine bonds and retaining secondary amine groups, with the following structural formula:

[0033]

[0034] Examples 4-9

[0035] Preparation of films with different TVT-MAPA / TOMA mass ratios: The TVT-MAPA intermediate obtained in Example 3 and the TOMA obtained in Example 1 were added to 40 mL of DMF solution according to the mass ratios shown in Table 1, controlling the solid content of the film-forming liquid to be 5 wt.%~20 wt.%. The mixture was stirred at 80 °C for 5 h to obtain a light yellow, homogeneous film-forming solution. The film-forming solution was applied to a glass plate, a polytetrafluoroethylene plate, or poured into a PP plastic box by solution casting or blade coating. After standing to remove bubbles, the film was dried and cured in an oven at 80 °C for 24 h, and then heated to 100 °C for another 6 h to obtain a transparent film upon demolding.

[0036] Table 1. Basic information on films with different TVT-MAPA-TOMA mass ratios

[0037]

[0038] Compare with Example 1

[0039] Aldehyde-containing aryloxytriazine monomer replacement experiment: Referring to the synthesis process of Example 2, the raw material vanillin was replaced with isovalerin to prepare the modified aldehyde-containing aryloxytriazine monomer; then, according to the film formation process of Example 6, the control film 1 was prepared.

[0040] Compare with Example 2

[0041] Bridged amine monomer substitution experiment: Following the synthesis process of Example 3, the bridged amine MAPA was replaced with N-ethyl-1,3-propanediamine, and the same film-forming steps as in Example 6 were used to prepare control film 2.

[0042] Figure 1 The results showed that TOMA, TVT, TVT-MAPA, and a high-transmittance, high-strength, and tough tung oil-based film and coating with UV full shielding and tunable blue light absorption were successfully prepared.

[0043] The structures of TOMA, TVT, TVT-MAPA, and the final thin film and coating network can be confirmed using Fourier transform infrared spectroscopy. Figure 1 As shown.

[0044] The tensile properties of films were tested according to GB / T 1040.1-2025 "Determination of tensile properties of plastics - Part 1: General". The tensile strength and elongation at break of Examples 5-8 and Comparative Examples 1-2 are shown in Table 2.

[0045] The glass transition temperatures of Examples 5-8 and Comparative Examples 1-2 were tested according to GB / T 19466.1-2004 "Differential Scanning Calorimetry (DSC) for Plastics - Part 1: General Rules", as shown in Table 2.

[0046] The decomposition temperatures of Examples 5-8 and Comparative Examples 1-2 were tested according to GB / T 33047.1-2025 "Thermogravimetric Analysis (TG) of Plastic Polymers - Part 1: General Rules", as shown in Table 2.

[0047] According to ASTM D1003-21, "Standard Test Method for Haze and Transmittance of Transparent Plastics," the transmittance and haze of Examples 4-9 and Control Examples 1-2 were tested using a UV / Vis spectrophotometer in the wavelength range of 200-800 nm, with a thickness of 200 μm. Figure 2 As shown in Table 3.

[0048] The degree of cross-linking reaction of the film was characterized by the gel content: 0.2g of samples from Examples 5-8 were immersed in water, ethanol, N,N-dimethylformamide, tetrahydrofuran, and dichloromethane solvents for 72h, respectively. The gel content and swelling degree of each sample were measured, and the results are as follows: Figure 3 As shown.

[0049] Using a power of 100mW / cm 2 The surface of the thin films in Examples 5-8 was irradiated with 365 nm ultraviolet light. The ultraviolet light emitter was 5 cm away from the surface of the thin film. The light source was turned off after 30 seconds. During the ultraviolet light irradiation process, the surface temperature change of the specimen was recorded in real time using an infrared thermal imager.

[0050] like Figure 4 As shown: In Example 5, the surface temperature of the film increased by ΔT=17℃ after 30 s; in Example 6, the surface temperature of the film increased by ΔT=19.8℃ after 30 s; in Example 7, the surface temperature of the film increased by ΔT=10.4℃ after 30 s; in Example 8, the surface temperature of the film increased by ΔT=7.4℃ after 30 s; and the surface temperature of the blank glass surface without film coverage increased by ΔT=2.1℃ after irradiation under the same conditions.

[0051] According to ASTM G154-2023, "Operating Procedure for Fluorescent Ultraviolet (UV) Lamp Exposure Testing Apparatus for Nonmetallic Materials," a UVA-340 fluorescent ultraviolet lamp was selected to conduct accelerated UV aging tests on the films of Examples 5-8, testing the stability of various material properties after aging. Figure 5 As shown in Table 4.

[0052] Test Examples 5-8: The films were recycled and reshaped by hot pressing at 120℃, 10MPa, and 1h. The retention rates of various properties after monomer recycling and secondary film preparation, and the performance comparison results of the regenerated samples are shown in Tables 5 and 6.

[0053] Table 2. Comparison of optical properties of films / coatings with different ratios

[0054]

[0055] Figure 2 The results in Table 2 show that the tung oil-maleic anhydride adduct, vanillin triazine trialdehyde (TVT), and TVT-MAPA monomers all possess excellent ultraviolet light absorption characteristics (a); the films and coatings prepared by the cross-linking reaction of the three types of monomers can continue this characteristic, achieving full-band ultraviolet shielding and tunable blue light absorption (b).

[0056] Comparing the data from Examples 4-9, it can be seen that increasing the ratio of TVT-MAPA to TOMA in the system reduces the transmittance of the film in the 420-500 nm blue light band, while simultaneously improving the shielding effect of ultraviolet and blue light.

[0057] Compared with Example 6, Comparative Examples 1 and 2, which were prepared by replacing different aldehyde and diamine monomers, still have excellent UV and blue light shielding performance. However, Example 6 also has higher transparency and lower haze.

[0058] Table 3. Mechanical and thermal properties of films with different formulations

[0059]

[0060] Figure 3 The results in Table 3 show that changing the ratio of TVT-MAPA to TOMA can significantly regulate the degree of crosslinking, mechanical strength, and heat resistance of the film. When the mass ratio of TVT-MAPA to TOMA is 1:3 (Example 6), the film gel content reaches 96.4%, the crosslinking network density is optimal, and the sample exhibits the highest mechanical strength and thermal stability temperature (57.62 MPa, 5% thermogravimetric temperature 279℃) among all samples, demonstrating the best overall performance. As the proportion of flexible tung oil segments in the system increases, the film elongation at break increases and the glass transition temperature decreases. The rigidity and toughness of the film can be balanced by adjusting the monomer ratio according to application requirements.

[0061] By replacing the triazine aromatic aldehyde component and the bridged amine monomer, Comparative Examples 1 and 2 can still produce films that combine ultraviolet and blue light shielding, mechanical properties, and light transmittance. Compared to Comparative Examples 1 and 2, the film of Example 6, prepared by combining vanillin-based triazine monomer with N-methyl-1,3-propanediamine (MAPA), exhibits higher tensile strength, glass transition temperature, and gel content. Its overall performance, including crosslinking density, mechanical properties, and thermal stability, is superior to the control film after monomer replacement, demonstrating that the vanillin-based triazine monomer and MAPA bridged amine combination system of this invention has outstanding comprehensive performance advantages.

[0062] Table 4. Performance retention rate after UV accelerated aging

[0063]

[0064] Figure 4 The results in Table 4 show that Examples 5-8 maintained high levels of UV and blue light shielding, transmittance, mechanical properties, and elongation. Example 6 is the sample with the best overall performance, retaining 89% of its original strength and 81% of its elongation after aging, without affecting transmittance and UV shielding performance. Furthermore, the film surface was smooth and without obvious cracks after UV aging.

[0065] Table 5. Performance retention after recycling

[0066]

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a tung oil-based thin film or coating with adjustable ultraviolet shielding and blue light absorption, characterized in that, Includes the following steps: Tung oil and maleic anhydride were reacted at a molar ratio of 1:(0.5~5.0) at 100~180℃ for 2~10 h to obtain a tung oil-maleic anhydride adduct; cyanuric chloride, an aromatic aldehyde containing phenolic hydroxyl groups, and an acid-binding agent were reacted at a molar ratio of 1:(2.4~3.6):(2.4~3.6) at 50~80℃ for 5~10 h. h, to obtain an aldehyde-containing aryloxytriazine compound; react the aldehyde-containing aryloxytriazine compound with a bridged amine monomer in an organic solvent, wherein the equivalence ratio of the aldehyde group of the aldehyde-containing aryloxytriazine compound to the primary amine group of the bridged amine monomer is 1:(0.7~1.3), the reaction temperature is 20~100℃, and the reaction time is 0.5~6h, so that the aldehyde group and the primary amine group condense to form an imine bond, and an intermediate retaining a secondary amine group is obtained. The molecular structure of the bridged amine monomer contains at least one primary amine group and at least one secondary amine group; react the intermediate with a tung oil-maleic anhydride adduct at a mass ratio of 1:(1~6) at 40~120℃ for 1~6h, so that the secondary amine group and the anhydride group undergo a ring-opening reaction to form an amide acid structure, and a film-forming solution is obtained; The film-forming liquid is used to form a film by solution casting, scraping, spin coating, spraying or casting, and then dried and cured to obtain the film or coating.

2. The preparation method according to claim 1, characterized in that, The aldehyde-containing aryloxytriazine compound is 2,4,6-trisubstituted-1,3,5-triazine, wherein each of the three substituents is independently selected from aldehyde-containing or non-aldehyde-containing aryloxy groups, and at least one substituent is an aldehyde-containing aryloxy group; the aldehyde-containing aryloxy group is provided by vanillin, syringaldehyde, p-hydroxybenzaldehyde, o-vanillin, salicylaldehyde, or isovalerin.

3. The preparation method according to claim 1, characterized in that, The bridged amine monomer has the structure shown in H2N-R1-NH-R2, wherein R1 is a C2-C12 alkylene group or a C2-C8 divalent segment containing an ether bond, and R2 is a C1-C8 alkyl, hydroxyalkyl, benzyl, or a substituent containing an ether chain; the bridged amine monomer is selected from at least one of N-methyl-1,3-propanediamine, N-ethyl-1,3-propanediamine, N-propyl-1,3-propanediamine, N-isopropyl-1,3-propanediamine, N-butyl-1,3-propanediamine, N-methyl-1,2-ethylenediamine, N-methyl-1,4-butanediamine, N-methyl-1,6-hexanediamine, N-(2-hydroxyethyl)-1,3-propanediamine, or a polyetheramine having at least one primary amine group and at least one secondary amine group.

4. The preparation method according to claim 1, characterized in that, The acid-binding agent is selected from at least one of anhydrous calcium carbonate, anhydrous potassium carbonate, sodium carbonate, and sodium bicarbonate; the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

5. The preparation method according to claim 1, characterized in that, The molar ratio of tung oil to maleic anhydride is 1:(2~4), and the reaction temperature is 120~160℃; the molar ratio of cyanuric chloride to phenolic hydroxy aromatic aldehyde is 1:(2.8~3.2); and the mass ratio of the intermediate to the tung oil-maleic anhydride adduct is 1:(2~5).

6. The preparation method according to claim 1, characterized in that, The solid content of the film-forming solution is 5wt.%~20wt.%, and the drying and curing are carried out in stages at 20~120℃ for 6~72h.

7. The tung oil-based thin film or coating with adjustable ultraviolet shielding and blue light absorption prepared by the preparation method according to any one of claims 1-6, characterized in that, The film or coating has an ultraviolet light transmittance of no more than 1% in the 200-400nm wavelength band and a visible light transmittance of no less than 80% in the 500-800nm ​​wavelength band, with a thickness of 10-1000μm.

8. The thin film or coating according to claim 7, characterized in that, The transmittance of the film or coating in the 400-500nm wavelength band is adjusted by changing the mass ratio of the aldehyde-containing aryloxytriazine compound to the tung oil-maleic anhydride adduct or the film thickness. As the mass ratio of the two increases, the transmittance of the film in the 400-500nm wavelength band decreases.

9. The thin film or coating according to claim 7, characterized in that, The film or coating can be reshaped by hot pressing; in an acidic aqueous medium, the imine bond can be dissociated, allowing the aldehyde-containing aryloxytriazine compound to be separated and recovered from the tung oil-derived components.

10. The application of the film or coating of claim 7 in transparent ultraviolet protection, blue-violet light modulation, display screen protection, lighting device protection, architectural window film, automotive window film, greenhouse covering, agricultural covering, outdoor weather-resistant coating, packaging materials, photothermal response, thermal management, flexible electronic packaging, or optical component protection.

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