Biodegradable film with high light transmittance and high efficiency of shielding ultraviolet, and preparation method and application thereof

Abstract

The application discloses a kind of high light-transmitting high-efficiency shielding ultraviolet biodegradable film and its preparation method and application.The high light-transmitting high-efficiency shielding ultraviolet biodegradable film provided by the application includes: biobased degradable film and lignin-tannin composite nanoparticles located in biobased degradable film.The high light-transmitting high-efficiency shielding ultraviolet biodegradable film provided by the application makes full use of the structural characteristics of lignin and tannin, and the composite particles generated by self-assembly of lignin and tannin, the π-π stacking of benzene ring in lignin structure and the rich phenolic hydroxyl in tannin structure can significantly enhance the ultraviolet shielding performance.In addition, tannin is lighter than lignin, which can significantly reduce the color of the film.Therefore, a biodegradable film with high transparency and high-efficiency ultraviolet shielding effect can be prepared at low addition amount.

Description

Technical Field

[0001] This invention relates to the field of UV-resistant materials technology, and more specifically, to a highly transparent and efficient UV-shielding biodegradable film, its preparation method, and its application. Background Technology

[0002] The quality of light and the growing environment are very important for plant growth. Agricultural films used in greenhouses have superior performance in terms of light transmittance, heat preservation, tensile strength and aging resistance, which is of great significance for the growth, yield and income of greenhouse plants.

[0003] High-transmittance, high-efficiency UV-shielding biodegradable films are functional agricultural films that extend their service life by introducing UV absorbers to reduce the damage of UV light to the film material. The UV absorbers in these anti-UV aging biodegradable films absorb UV light and release it as harmless energy. The heat released in this process can increase the temperature for crop growth and development, which is beneficial for accelerating crop growth. Furthermore, the addition of UV absorbers can mitigate the degradation of the biodegradable film, thereby extending the coverage period of the biodegradable film material, which will contribute to increased crop yield. Therefore, the use of anti-UV aging biodegradable films is of great significance to the development of agricultural production.

[0004] Currently, commonly used organic UV absorbers mainly fall into four categories: benzophenones, benzotriazoles, triazines, and salicylates. The main problems with these UV absorbers are their small molecular weight, volatility, and migration, and their prevalence in traditional plastics. Therefore, UV absorbers suitable for degradation materials and with stable performance, as well as biodegradable films that resist UV aging, are urgently needed in the market. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a biodegradable film with high light transmittance and high efficiency in shielding ultraviolet rays, as well as its preparation method and application.

[0006] The technical problem solved by this invention is achieved by the following technical solution.

[0007] This invention provides a biodegradable film with high light transmittance and high efficiency in shielding ultraviolet rays, comprising: a bio-based biodegradable film and lignin-tannin composite nanoparticles located within the bio-based biodegradable film.

[0008] The present invention also provides a method for preparing the above-mentioned high-transmittance, high-efficiency ultraviolet-shielding biodegradable film, which includes: preparing the high-transmittance, high-efficiency ultraviolet-shielding biodegradable film by solution casting.

[0009] The present invention also provides an application of the above-mentioned high light transmittance and high efficiency UV shielding biodegradable film in agricultural greenhouse films.

[0010] The present invention has the following beneficial effects:

[0011] This invention provides a high-transmittance, high-efficiency UV-shielding biodegradable film, its preparation method, and its applications. The high-transmittance, high-efficiency UV-shielding biodegradable film provided by this invention comprises: a bio-based biodegradable film and lignin-tannin composite nanoparticles located within the bio-based biodegradable film. This invention fully utilizes the structural characteristics of lignin and tannin, enabling the self-assembly of lignin and tannin to form well-ordered lignin-tannin composite nanoparticles, improving the dispersibility of the lignin-tannin composite nanoparticles within the bio-based biodegradable film. Simultaneously, the π-π stacking of benzene rings in the lignin structure and the abundant phenolic hydroxyl groups in the tannin structure significantly enhance UV-shielding performance. Tannin is lighter in color than lignin, which can significantly reduce the film's color. Therefore, film materials with both high transparency and high UV-shielding effectiveness can be prepared with low addition amounts. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 SEM images and particle size distribution of lignin nanoparticles and lignin-myricetin nanoparticles;

[0014] Figure 2 The distribution of lignin nanoparticles and lignin-tannin composite nanoparticles in PVA films;

[0015] Figure 3 The UV-Vis transmittance curves and UV protection index values ​​of composite films with different compositions;

[0016] Figure 4 The photodegradation of four different photosensitive pesticides under composite film covering is shown. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0018] The purpose of this invention is to provide a method for preparing a high-efficiency UV-shielding biodegradable film from lignin-tannin composite nanoparticles. This method uses abundant renewable biomass resources as raw materials to achieve high-value utilization of lignin and tannin, promotes the full-component utilization of biomass resources, and the prepared high-transmittance, high-efficiency UV-shielding biodegradable film has both high transparency and high UV-shielding performance at low addition levels. The preparation method is simple and the production cost is low.

[0019] The following is a detailed description of a high-transmittance, high-efficiency UV-shielding biodegradable film, its preparation method, and its application, provided by embodiments of the present invention.

[0020] In a first aspect, embodiments of the present invention provide a biodegradable film with high light transmittance and high efficiency in shielding ultraviolet rays, comprising a bio-based biodegradable film and lignin-tannin composite nanoparticles located within the bio-based biodegradable film.

[0021] This invention provides a highly transparent and efficient UV-shielding biodegradable film containing lignin-tannin composite nanoparticles. Lignin, a natural aromatic polymer composed of phenylpropane units linked by C-C and CO bonds, is abundant in nature, second only to cellulose in abundance. Based on the numerous benzene rings and hydrophilic groups in its structure, lignin oligomers dissolved in organic solvents, upon gradual addition of an antisolvent (water), exhibit hydrophobic cores formed by π-π interactions of the benzene rings, while simultaneously forming hydrophilic shells dominated by hydrophilic groups such as phenolic hydroxyl, alcoholic hydroxyl, and carboxyl groups. This results in lignin nanoparticles dispersed in the aqueous solvent. Lignin nanoparticles possess excellent UV-shielding properties; adding them to film materials can significantly improve their UV-shielding performance. However, excessive addition, while providing high UV-shielding performance, can lead to a darker film color and decreased compatibility with the film material. Tannin, a natural polyphenol compound, is abundant in nature and contains rich phenolic hydroxyl groups, exhibiting excellent UV resistance. However, due to its strong hydrophilicity, tannin has poor self-assembly properties.

[0022] Therefore, the high-transmittance, high-efficiency UV-shielding biodegradable film provided in this embodiment of the invention, composed of composite particles formed by the self-assembly of lignin and tannin, exhibits significantly enhanced UV-shielding performance due to the π-π stacking of benzene rings in the lignin structure and the abundant phenolic hydroxyl groups in the tannin structure. Furthermore, the lighter color of tannin compared to lignin can significantly reduce the film's color. Thus, a film material possessing both high transparency and high-efficiency UV-shielding effect can be prepared with low addition amounts.

[0023] In an optional embodiment, the amount of lignin-tannin composite nanoparticles added to the bio-based biodegradable membrane is 1%-10%, preferably 3%-5%.

[0024] In an optional embodiment, the mass ratio of lignin to tannin is (9:1)-(1:9), more preferably (6:4)-(4:6);

[0025] Preferably, the tannins include at least one of the following: bayberry tannin, larch tannin, mandarin orange tannin, acacia majanis tannin, and black thorn bark tannin;

[0026] Preferably, the lignin includes at least one of organically dissolved lignin, alkali lignin, enzymatically hydrolyzed lignin, and sodium lignin sulfonate.

[0027] In an optional embodiment, the bio-based biodegradable membrane is prepared using one or more of polyvinyl alcohol, polylactic acid, chitosan, and gelatin.

[0028] Secondly, embodiments of the present invention also provide a method for preparing the above-mentioned high-transmittance, high-efficiency ultraviolet-shielding biodegradable film, which includes: preparing the high-transmittance, high-efficiency ultraviolet-shielding biodegradable film by solution casting.

[0029] In an optional embodiment, the preparation of lignin-tannin composite nanoparticles includes: adding lignin and tannin to a mixed solvent of acetone and water, stirring to dissolve, and obtaining a mixed solution; placing the mixed solution in an ultrasonic environment, adding distilled water dropwise to it, and continuing to sonicate after the addition is complete to allow lignin and tannin to fully self-assemble, thereby obtaining lignin-tannin composite nanoparticles.

[0030] Preferably, the mass ratio of lignin to tannin is (9:1)-(1:9), more preferably (6:4)-(4:6);

[0031] Preferably, the concentration of the lignin-tannin solution is 1 mg / mL to 50 mg / mL, more preferably 5 mg / mL to 10 mg / mL;

[0032] Preferably, the distilled water dripping rate is 1 mL / min-20 mL / min, more preferably 5 mL / min-10 mL / min;

[0033] Preferably, the process further includes: after the lignin and tannin have fully self-assembled, the crude product is centrifuged, the supernatant is removed, centrifugation and washing are continued, and then freeze-drying is performed to obtain lignin-tannin composite nanoparticles.

[0034] In an optional embodiment, the preparation of lignin includes: extracting lignin from the first biomass raw material using a solvothermal method, and obtaining organically dissolved lignin by dichloromethane extraction;

[0035] Preferably, the temperature for extracting lignin from the first biomass raw material using the solvothermal method is 180℃-240℃, more preferably 200℃-220℃;

[0036] Preferably, the material-to-liquid ratio for extracting lignin from the first biomass raw material using the solvothermal method is (1:100)-(10:100), more preferably (3:100)-(6:100);

[0037] Preferably, the ratio of acetone to water used in the solvothermal extraction of lignin from the first biomass raw material is (1:9)-(9:1), more preferably (4:6)-(9:1);

[0038] Preferably, the extraction time for extracting lignin from the first biomass raw material using the solvothermal method is 0.5h-3h, more preferably 1h-2h;

[0039] Preferably, the first biomass raw material includes at least one of pine powder and red cedar powder;

[0040] Preferably, the first biomass raw material is placed in a mixed solvent of acetone and water and kept at 180℃-240℃ for a period of time. Then, the obtained extract is extracted with dichloromethane. The organic phase is removed by rotary evaporation to remove dichloromethane and acetone, and then dried to obtain organic dissolved lignin.

[0041] In an optional embodiment, the preparation of tannins includes: extracting tannins from a second biomass raw material using a solvothermal method, and obtaining water-insoluble tannins by precipitation with distilled water;

[0042] Preferably, the temperature for extracting tannins from the second biomass feedstock using the solvothermal method is 40℃-80℃, more preferably 50℃-60℃;

[0043] Preferably, the temperature for extracting tannins from the second biomass feedstock using the solvothermal method is 40℃-80℃, more preferably 50℃-60℃;

[0044] Preferably, the material-to-liquid ratio for extracting tannins from the second biomass feedstock using the solvothermal method is (1:100)-(20:100), more preferably (5:100)-(15:100);

[0045] Preferably, the ratio of acetone to water used in the solvothermal extraction of tannins from the second biomass feedstock is (1:9)-(9:1), more preferably (4:6)-(9:1);

[0046] Preferably, the second biomass raw material includes at least one of the following: bayberry, larch, mandarin orange, acacia mangium, and black thorn bark;

[0047] Preferably, the second biomass raw material is placed in a mixed solvent of acetone and water and kept at 40℃-80℃ for a period of time. Then, the acetone is removed by rotary evaporation of the obtained extract, followed by centrifugation, washing with water, and drying to obtain water-insoluble tannin.

[0048] This invention provides a high-transmittance, high-efficiency UV-shielding biodegradable film containing lignin-tannin composite nanoparticles. In the preparation process, lignin extracted from a first biomass raw material is extracted with dichloromethane to obtain organically dissolved lignin, while tannin extracted from a second biomass raw material is precipitated with distilled water to obtain water-insoluble tannin. After purification, water-soluble components (such as small-molecule sugars, carboxylic acids, proteins, and water-soluble tannin monomers) can be avoided from interfering with self-assembly. Ultrasonic-assisted treatment promotes the preparation of well-formed lignin-tannin composite nanoparticles, and the nanosize effect improves their dispersibility within the biodegradable film. Test results also show that the prepared lignin-tannin composite nanoparticles are uniformly dispersed within the biodegradable film, enabling the preparation of a biodegradable film with both high transparency and high UV shielding effect at low addition levels.

[0049] In an optional embodiment, the preparation of a biodegradable film with high light transmittance and high efficiency in shielding ultraviolet rays includes: mixing lignin-tannin composite nanoparticles with a biodegradable polymer solution, and then forming a film by solution casting to obtain a biodegradable film with high light transmittance and high efficiency in shielding ultraviolet rays.

[0050] Preferably, the amount of lignin-tannin composite nanoparticles added is 1%-10%, more preferably 3%-5%;

[0051] Preferably, the biodegradable polymer solution has a mass concentration of 3% and a dissolution temperature of 90°C;

[0052] Preferably, the biodegradable polymer includes one or more of polyvinyl alcohol, polylactic acid, chitosan, and gelatin.

[0053] Thirdly, embodiments of the present invention also provide an application of the above-mentioned high-transmittance, high-efficiency UV-shielding biodegradable film in agricultural greenhouse films.

[0054] The present invention will be further described below with reference to embodiments.

[0055] In the following examples and comparative examples, polyvinyl alcohol is abbreviated as PVA, lignin is abbreviated as L, and tannin is abbreviated as T.

[0056] Example 1

[0057] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0058] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 18g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 220℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin with a yield of 26.5%. The extraction conditions for tannin were: 50g bayberry bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 50℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble bayberry tannin with a yield of 9.0%.

[0059] ② Preparation of lignin-tannin composite nanoparticles: 200 mg of lignin and 200 mg of myricetin were added to 40 mL of mixed solvent (28 mL of acetone and 12 mL of distilled water). The solvent was stirred with a glass rod until completely dissolved. The solution was placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 240 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 10 mL / min. After the addition was complete, the solution was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The solution was centrifuged, the supernatant was removed, and the solution was centrifuged and washed with water three times. The solution was then freeze-dried to obtain lignin-myricetin composite nanoparticles with a yield of 47.8%.

[0060] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The lignin-tannin composite nanoparticles prepared above were added to the PVA solution at a concentration of 3%, and the mixture was magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composition of the composite film was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 62%, and the UV transmittance was 1.5%.

[0061] Example 2

[0062] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0063] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 24g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 220℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin, with a yield of 24.9%. The extraction conditions for tannin were: 50g larch bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 60℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble larch tannin, with a yield of 6.3%.

[0064] ② Preparation of lignin-tannin composite nanoparticles: 40 mg of lignin and 360 mg of larch tannin were added to 80 mL of mixed solvent (56 mL of acetone and 24 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 480 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 5 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was then centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. Finally, it was freeze-dried to obtain lignin-larch tannin composite nanoparticles with a yield of 30.5%.

[0065] ③ Composite film preparation: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of the PVA. The prepared lignin-tannin composite nanoparticles were added to the PVA at a concentration of 10%, and the mixture was magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was then demolded and stored in a desiccator. The composite film composition was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 29%, and the UV transmittance was 13%.

[0066] Example 3

[0067] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0068] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 18g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 200℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin, with a yield of 24.3%. The extraction conditions for tannin were: 50g citrus peel powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 80℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble citrus tannin, with a yield of 1.5%.

[0069] ② Preparation of lignin-tannin composite nanoparticles: 380 mg of lignin and 20 mg of amla tannin were added to 40 mL of mixed solvent (28 mL of acetone and 12 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 240 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 2 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was then centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. Finally, it was freeze-dried to obtain lignin-amla tannin composite nanoparticles with a yield of 57.1%.

[0070] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA, yielding a PVA solution. The lignin-tannin composite nanoparticles prepared above were added to the PVA solution at a dosage of 6%, and magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composition of the composite film was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 23%, and the UV transmittance was 2%.

[0071] Example 4

[0072] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0073] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 30g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 240℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin, with a yield of 22.3%. The extraction conditions for tannin were: 50g bayberry bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 50℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble bayberry tannin, with a yield of 9.0%.

[0074] ② Preparation of lignin-tannin composite nanoparticles: 20 mg of lignin and 380 mg of myricetin were added to 8 mL of mixed solvent (5.6 mL of acetone and 2.4 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 48 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 1 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. The mixture was then freeze-dried to obtain lignin-myricetin composite nanoparticles with a yield of 40.2%.

[0075] ③ Composite film preparation: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The prepared lignin-tannin composite nanoparticles were added to the PVA solution at 8% concentration. The mixture was magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of the PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composition of the composite film was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 36%, and the UV transmittance was 15%.

[0076] Example 5

[0077] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0078] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 18g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 180℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin, with a yield of 20.1%. The extraction conditions for tannin were: 50g bayberry bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 40℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble bayberry tannin, with a yield of 7.2%.

[0079] ② Preparation of lignin-tannin composite nanoparticles: 360 mg of lignin and 40 mg of myricetin were added to 200 mL of mixed solvent (140 mL of acetone and 60 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 1200 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 20 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was then centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. Finally, it was freeze-dried to obtain lignin-myricetin composite nanoparticles with a yield of 55.6%.

[0080] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The lignin-tannin composite nanoparticles prepared above were added to the PVA solution at a dosage of 1%, and magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composition of the composite film was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 76%, and the UV transmittance was 38%.

[0081] Example 6

[0082] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0083] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 9g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 220℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin, with a yield of 27.2%. The extraction conditions for tannin were: 50g black thorn bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 60℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble black thorn bark tannin, with a yield of 1.6%.

[0084] ② Preparation of lignin-tannin composite nanoparticles: 240 mg of lignin and 160 mg of black thorn bark tannin were added to 80 mL of mixed solvent (56 mL of acetone and 24 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 480 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 5 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was then centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. Finally, it was freeze-dried to obtain lignin-black thorn bark tannin composite nanoparticles with a yield of 54.9%.

[0085] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The lignin-tannin composite nanoparticles prepared above were added to the PVA solution at a concentration of 2%, and the mixture was magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was then demolded and stored in a desiccator. The composition of the composite film was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 64%, and the UV transmittance was 26%.

[0086] Example 7

[0087] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0088] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 3g pine powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 200℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin with a yield of 25.6%. The extraction conditions for tannin were: 50g Acacia mangium bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 50℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble Acacia mangium tannin with a yield of 2.0%.

[0089] ② Preparation of lignin-tannin composite nanoparticles: 160 mg of lignin and 240 mg of acacia mangium tannin were added to 16 mL of mixed solvent (11.2 mL of acetone and 4.8 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 96 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 2 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. The mixture was then freeze-dried to obtain lignin-acacia mangium tannin composite nanoparticles with a yield of 61.9%.

[0090] ③ Composite film preparation: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The prepared lignin-tannin composite nanoparticles were added to the PVA solution at a concentration of 6%, and the mixture was magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of the PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was then demolded and stored in a desiccator. The composite film composition was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 41%, and the UV transmittance was 19%.

[0091] Example 8

[0092] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0093] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 18g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 220℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin with a yield of 26.5%. The extraction conditions for tannin were: 50g larch bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 50℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble larch tannin with a yield of 5.8%.

[0094] ② Preparation of lignin-tannin composite nanoparticles: 200 mg of lignin and 200 mg of larch tannin were added to 40 mL of mixed solvent (28 mL of acetone and 12 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 240 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 5 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was then centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. Finally, the mixture was freeze-dried to obtain lignin-larch tannin composite nanoparticles with a yield of 45.5%.

[0095] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA, yielding a PVA solution. The lignin-tannin composite nanoparticles prepared above were added to the PVA solution at a dosage of 10%, and magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composition of the composite film was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 23%, and the UV transmittance was 1%.

[0096] Example 9

[0097] A method for preparing a biodegradable thin film with high light transmittance and high efficiency in blocking ultraviolet rays includes the following steps:

[0098] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 18g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 200℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin, with a yield of 24.3%. The extraction conditions for tannin were: 50g bayberry bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 60℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble bayberry tannin, with a yield of 9.4%.

[0099] ② Preparation of lignin-tannin composite nanoparticles: 100 mg of lignin and 300 mg of myricetin were added to 80 mL of mixed solvent (56 mL of acetone and 24 mL of distilled water). The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 480 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 10 mL / min. After the addition was complete, the mixture was sonicated for another 30 min to allow the lignin and tannin to fully self-assemble. The mixture was then centrifuged, the supernatant was removed, and the mixture was centrifuged and washed with water three times. Finally, it was freeze-dried to obtain lignin-myricetin composite nanoparticles with a yield of 43.7%.

[0100] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The lignin-tannin composite nanoparticles prepared above were added to the PVA solution at a dosage of 4%, and magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composition of the composite film was PVA-LT. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 51%, and the UV transmittance was 13%.

[0101] Comparative Example 1

[0102] A method for preparing a biodegradable thin film doped with lignin nanoparticles includes the following steps:

[0103] ① Lignin extraction: Lignin was extracted using a solvothermal method. The extraction conditions were: 18g pine powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 220℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the organic dissolved lignin was obtained after drying in an oven at 105℃. The yield was 26.5%.

[0104] ② Preparation of lignin nanoparticles: 400 mg of lignin was added to 40 mL of mixed solvent (28 mL of acetone and 12 mL of distilled water). The solvent was stirred with a glass rod until completely dissolved. The solution was placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 240 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 10 mL / min. After the addition was complete, the solution was sonicated for another 30 min to allow the lignin to fully self-assemble. The solution was centrifuged, the supernatant was removed, and the solution was centrifuged and washed with water three times. The solution was then freeze-dried to obtain lignin nanoparticles with a yield of 56.7%.

[0105] ③ Composite film preparation: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The prepared lignin nanoparticles were added to the PVA solution at a concentration of 3% and magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composite film composition was PVA-L. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 47%, and the UV transmittance was 14%.

[0106] Comparative Example 2

[0107] A method for preparing a biodegradable thin film doped with tannin nanoparticles includes the following steps:

[0108] ① Tannin extraction: Tannin was extracted using a solvothermal method. The extraction conditions were: 50g of bayberry bark powder, 500mL of mixed solvent (350mL of acetone and 150mL of deionized water), extraction temperature of 50℃, and extraction time of 3h. The organic solvent was then removed by rotary evaporation. After centrifugation and washing with water, water-insoluble bayberry tannin was obtained. The yield was 9.0%.

[0109] ② Preparation of tannin nanoparticles: 400 mg of bayberry tannin was added to 40 mL of mixed solvent (28 mL of acetone and 12 mL of distilled water). The solvent was stirred with a glass rod until completely dissolved. The solution was placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. 240 mL of distilled water was added dropwise using a constant flow pump at a flow rate of 10 mL / min. After the addition was complete, the solution was sonicated for another 30 min to allow the tannins to fully self-assemble. The solution was centrifuged, the supernatant was removed, and the solution was centrifuged and washed with water three times. The solution was then freeze-dried to obtain bayberry tannin nanoparticles with a yield of 37.4%.

[0110] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The prepared myricetin nanoparticles were added to the PVA solution at a concentration of 3% and magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and myricetin nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was demolded and stored in a desiccator. The composition of the composite film was PVA-T. The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 83%, and the UV transmittance was 21%.

[0111] Comparative Example 3

[0112] A method for preparing a biodegradable thin film doped with tannin and lignin mixed nanoparticles includes the following steps:

[0113] ① Lignin and Tannin Extraction: Lignin and tannin were extracted separately using a solvothermal method. The extraction conditions for lignin were: 18g pine wood powder, 300mL mixed solvent (210mL acetone and 90mL deionized water), extraction temperature 220℃, time 2h, followed by extraction with dichloromethane. The organic phase was collected, the organic solvent was removed by rotary evaporation, and the product was dried in an oven at 105℃ to obtain organically soluble lignin with a yield of 26.5%. The extraction conditions for tannin were: 50g bayberry bark powder, 500mL mixed solvent (350mL acetone and 150mL deionized water), extraction temperature 50℃, time 3h, followed by removal of the organic solvent by rotary evaporation, centrifugation, and washing with water to obtain water-insoluble bayberry tannin with a yield of 9.0%.

[0114] ② Preparation of lignin nanoparticles and tannin nanoparticles: 200 mg of lignin and 200 mg of myricetin were added to 40 mL of mixed solvent (28 mL of acetone and 12 mL of distilled water), respectively. The mixture was stirred with a glass rod until completely dissolved. The mixture was then placed in an ultrasonic environment under the following conditions: 30 °C, 45 kHz, 100%. The supernatant was removed, and the mixture was centrifuged and washed with water three times. The mixture was then freeze-dried to obtain lignin nanoparticles with a yield of 53.4% ​​and myricetin nanoparticles with a yield of 34.2%.

[0115] ③ Preparation of composite film: A 3% PVA solution was prepared and magnetically stirred at 90℃ for 2 hours to ensure complete dissolution of PVA. The lignin-tannin composite nanoparticles prepared above were added to the PVA solution at a concentration of 3%, and the mixture was magnetically stirred at 60℃ for 0.5 hours to ensure thorough mixing of PVA and lignin-tannin composite nanoparticles. After ultrasonic degassing, the mixture was poured into a 90mm polystyrene petri dish and allowed to air dry at room temperature. The resulting composite film was then demolded and stored in a desiccator. The composition of the composite film was PVA-(L+T). The composite film was tested using a UV-Vis spectrophotometer with an integrating sphere. The visible light transmittance was 64%, and the UV transmittance was 17%.

[0116] Performance testing

[0117] (1) The particle size distribution of lignin nanoparticles and lignin-myricetin nanoparticles was scanned and statistically analyzed. From Figure 1 It can be seen that the average particle size of the lignin-myricetin composite nanoparticles is smaller than that of the lignin nanoparticles. The average particle size of the lignin nanoparticles is 0.47 μm, while that of the lignin-myricetin composite nanoparticles is 0.25 μm.

[0118] (2) The distribution of lignin nanoparticles and lignin-tannin composite nanoparticles in PVA films was tested. Figure 2 It can be seen that lignin nanoparticles are significantly aggregated in the film, while lignin-tannin composite nanoparticles are uniformly dispersed in the film.

[0119] (3) The UV-Vis transmittance curves and UV protection index values ​​of the four composite films with different compositions in Example 1 and Comparative Examples 1-3 were tested using an UV-Vis spectrophotometer with an integrating sphere. The scanning range was 200-800 nm, T%, slit width was 2 nm, and scanning interval was 1 nm.

[0120] See test results Figure 3 ,from Figure 3 It can be seen that, for tannins from different sources (including bayberry tannin, larch tannin, amla tannin, acacia majans tannin, and black thorn bark tannin), the biodegradable film doped with lignin-tannin composite nanoparticles (PVA-LT) has better UV blocking ability than the biodegradable film doped with single lignin nanoparticles (PVA-L), single tannin nanoparticles (PVA-T), and mixed lignin and tannin nanoparticles (PVA-(L+T)), while maintaining good transmittance.

[0121] (4) A certain amount of four different photosensitive pesticides were placed in an open, opaque container, and the container was covered with the high-transmittance, high-efficiency UV-shielding biodegradable film provided in Example 1 of this invention. The container was irradiated under a 365nm UV lamp for a set time. After the four different photosensitive pesticides were redissolved in ethanol, the absorbance values ​​were measured at the maximum absorption wavelength using a UV spectrophotometer. The maximum absorption wavelengths were 254nm, 221nm, 272nm, and 249nm, respectively. The photodegradation performance of the four different photosensitive pesticides under the cover of the high-transmittance, high-efficiency UV-shielding biodegradable film provided in Example 1 of this invention was tested.

[0122] See test results Figure 4 Four representative photosensitive pesticides are abamectin (insecticide), indole-3-acetic acid (plant growth regulator), ethoxyflufenicol (herbicide), and azoxystrobin (fungicide). From Figure 4 It can be seen that PVA films mixed with lignin-tannin composite nanoparticles can significantly extend the working life of all four representative photosensitive pesticides.

[0123] The test results above show that the lignin-tannin composite nanoparticle film (PVA-LT) prepared by the synergistic self-assembly of lignin and tannin provided by this invention has a lower ultraviolet transmittance than the single lignin nanoparticle film (PVA-L) and the single tannin nanoparticle film (PVA-T), while its visible light transmittance is higher than that of the single lignin nanoparticle film (PVA-L). It is expected to be widely used in fields such as agricultural greenhouse films.

[0124] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A biodegradable film with high light transmittance and high efficiency in blocking ultraviolet rays, characterized in that, This includes bio-based biodegradable membranes and lignin-tannin composite nanoparticles located within the bio-based biodegradable membranes; The preparation of the lignin-tannin composite nanoparticles includes: adding the lignin and the tannin to a mixed solvent of acetone and water, stirring to dissolve them, and obtaining a mixed solution; placing the mixed solution in an ultrasonic environment, adding distilled water dropwise to it, and continuing to sonicate after the addition is completed to allow the lignin and the tannin to fully self-assemble, thereby obtaining lignin-tannin composite nanoparticles.

2. The high-transmittance, high-efficiency UV-shielding biodegradable film according to claim 1, characterized in that, The amount of lignin-tannin composite nanoparticles added to the bio-based biodegradable membrane is 1%-10%.

3. The high-transmittance, high-efficiency UV-shielding biodegradable film according to claim 2, characterized in that, The amount of lignin-tannin composite nanoparticles added to the bio-based biodegradable membrane is 3%-5%.

4. The high-transmittance, high-efficiency UV-shielding biodegradable film according to claim 2, characterized in that, The mass ratio of the lignin to the tannin is (9:1)-(1:9).

5. The high-transmittance, high-efficiency UV-shielding biodegradable film according to claim 4, characterized in that, The mass ratio of the lignin to the tannin is (6:4)-(4:6).

6. The high-transmittance, high-efficiency UV-shielding biodegradable film according to claim 1, characterized in that, The tannins include at least one of the following: bayberry tannin, larch tannin, mandarin orange tannin, acacia tannin, and black thorn bark tannin.

7. The high-transmittance, high-efficiency UV-shielding biodegradable film according to claim 1, characterized in that, The lignin includes at least one of organically dissolved lignin, alkali lignin, enzymatically hydrolyzed lignin, and sodium lignin sulfonate.

8. The high-transmittance, high-efficiency UV-shielding biodegradable film according to any one of claims 1-7, characterized in that, The bio-based biodegradable membrane is prepared using a biodegradable polymer, which includes one or more of polyvinyl alcohol, polylactic acid, chitosan, and gelatin.

9. A method for preparing a high-transmittance, high-efficiency ultraviolet-shielding biodegradable thin film according to claim 1, characterized in that, It includes: A biodegradable film with high light transmittance and high UV shielding efficiency was prepared by solution casting.

10. The preparation method according to claim 9, characterized in that, The preparation of the lignin-tannin composite nanoparticles includes: adding the lignin and the tannin to a mixed solvent of acetone and water, stirring to dissolve them, and obtaining a mixed solution; placing the mixed solution in an ultrasonic environment, adding distilled water dropwise, and continuing to sonicate after the addition is complete to allow the lignin and the tannin to fully self-assemble, thereby obtaining lignin-tannin composite nanoparticles; the mass ratio of the lignin and the tannin is (9:1)-(1:9).

11. The preparation method according to claim 10, characterized in that, The mass ratio of the lignin to the tannin is (6:4)-(4:6).

12. The preparation method according to claim 10, characterized in that, The concentration of the lignin-tannin solution is 1 mg / mL to 50 mg / mL.

13. The preparation method according to claim 12, characterized in that, The concentration of the lignin-tannin solution is 5 mg / mL to 10 mg / mL.

14. The preparation method according to claim 10, characterized in that, The distilled water droplet speed is 1 mL / min-20 mL / min.

15. The preparation method according to claim 14, characterized in that, The distilled water was added at a rate of 5 mL / min to 10 mL / min.

16. The preparation method according to claim 10, characterized in that, Also includes: After the lignin and tannin have fully self-assembled, the crude product is centrifuged, the supernatant is removed, centrifugation and washing are continued, and then freeze-drying is performed to obtain the lignin-tannin composite nanoparticles.

17. The preparation method according to claim 10, characterized in that, The preparation of lignin includes: extracting lignin from the first biomass raw material using a solvothermal method, and obtaining organically dissolved lignin by dichloromethane extraction.

18. The preparation method according to claim 17, characterized in that, The temperature for extracting lignin from the first biomass feedstock using the solvothermal method is 180℃-240℃.

19. The preparation method according to claim 18, characterized in that, The temperature for extracting lignin from the first biomass feedstock using the solvothermal method is 200℃-220℃.

20. The preparation method according to claim 17, characterized in that, The material-to-liquid ratio for extracting lignin from the first biomass feedstock using the solvothermal method was (1:100)-(10:100).

21. The preparation method according to claim 20, characterized in that, The material-to-liquid ratio for extracting lignin from the first biomass feedstock using the solvothermal method is (3:100)-(6:100).

22. The preparation method according to claim 17, characterized in that, The ratio of acetone to water used in the solvothermal extraction of lignin from the first biomass feedstock was (1:9)-(9:1).

23. The preparation method according to claim 22, characterized in that, The ratio of acetone to water for extracting lignin from the first biomass feedstock using the solvothermal method is (4:6)-(9:1).

24. The preparation method according to claim 17, characterized in that, The extraction time for lignin from the first biomass raw material using the solvothermal method was 0.5h-3h.

25. The preparation method according to claim 24, characterized in that, The extraction time for lignin from the first biomass raw material using the solvothermal method was 1-2 hours.

26. The preparation method according to claim 17, characterized in that, The first biomass raw material includes at least one of pine powder and red cypress powder.

27. The preparation method according to claim 17, characterized in that, The first biomass raw material was placed in a mixed solvent of acetone and water and kept at 180℃-240℃ for a period of time. The obtained extract was then extracted with dichloromethane. The organic phase was removed by rotary evaporation to remove dichloromethane and acetone, and then dried to obtain organic dissolved lignin.

28. The preparation method according to claim 10, characterized in that, The preparation of the tannins includes: extracting tannins from the second biomass raw material using a solvothermal method, and obtaining water-insoluble tannins by precipitation with distilled water.

29. The preparation method according to claim 28, characterized in that, The temperature for extracting tannins from the second biomass feedstock using the solvothermal method is 40℃-80℃.

30. The preparation method according to claim 29, characterized in that, The temperature for extracting tannins from the second biomass feedstock using the solvothermal method is 50℃-60℃.

31. The preparation method according to claim 28, characterized in that, The material-to-liquid ratio for extracting tannins from the second biomass feedstock using the solvothermal method is (1:100)-(20:100).

32. The preparation method according to claim 31, characterized in that, The material-to-liquid ratio for extracting tannins from the second biomass feedstock using the solvothermal method is (5:100)-(15:100).

33. The preparation method according to claim 28, characterized in that, The ratio of acetone to water for extracting tannins from the second biomass feedstock using the solvothermal method is (1:9)-(9:1).

34. The preparation method according to claim 33, characterized in that, The ratio of acetone to water for extracting tannins from the second biomass feedstock using the solvothermal method is (4:6)-(9:1).

35. The preparation method according to claim 28, characterized in that, The extraction time for tannins from the second biomass feedstock using the solvothermal method was 0.5h-6h.

36. The preparation method according to claim 35, characterized in that, The extraction time for tannins from the second biomass feedstock using the solvothermal method was 2-4 hours.

37. The preparation method according to claim 28, characterized in that, The second biomass raw material includes at least one of the following: bayberry, larch, mandarin orange, acacia mangium, and black thorn bark.

38. The preparation method according to claim 28, characterized in that, The second biomass raw material was placed in a mixed solvent of acetone and water and kept at 40℃-80℃ for a period of time. Then, the acetone was removed by rotary evaporation of the obtained extract, followed by centrifugation, washing with water, and drying to obtain water-insoluble tannin.

39. The preparation method according to claim 9, characterized in that, The preparation of the high-transmittance, high-efficiency UV-shielding biodegradable film includes: mixing the lignin-tannin composite nanoparticles with a biodegradable polymer solution, and then forming a film by solution casting to obtain a high-transmittance, high-efficiency UV-shielding biodegradable film.

40. The preparation method according to claim 39, characterized in that, The amount of lignin-tannin composite nanoparticles added is 1%-10%.

41. The preparation method according to claim 40, characterized in that, The amount of lignin-tannin composite nanoparticles added is 3%-5%.

42. The preparation method according to claim 39, characterized in that, The biodegradable polymer solution has a mass concentration of 3% and a dissolution temperature of 90°C.

43. The preparation method according to claim 39, characterized in that, The biodegradable polymers include one or more of polyvinyl alcohol, polylactic acid, chitosan, and gelatin.

44. The application of a high-transmittance, high-efficiency UV-shielding biodegradable film according to any one of claims 1-8 in agricultural greenhouse films.

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