Degradable agricultural functional film and preparation method thereof

Abstract

The invention provides a degradable agricultural functional film and a preparation method thereof, and relates to the technical field of degradable materials. The preparation method of the degradable agricultural functional film comprises the following steps: mixing adipic acid, 1, 4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, an inorganic filler, an anti-aging agent, tetrabutyl titanate and phosphite, carrying out polymerization reaction to obtain an anti-aging layer precursor polymer, and preparing the anti-aging layer precursor polymer into an anti-aging layer by adopting a blow molding machine; replacing an anti-aging agent with an anti-fogging agent to prepare an anti-fogging layer; mixing tungstate with a polymer monomer and other auxiliaries to obtain an ultraviolet light reversible color-changing pigment precursor, and coating the ultraviolet light reversible color-changing pigment precursor on the surface of the anti-aging layer subjected to laser etching to obtain an ultraviolet light reversible color-changing layer; and combining the three layers of materials to prepare the degradable agricultural functional film. By reasonably designing the raw materials, the agricultural functional film has degradability and photochromic property while ensuring high strength and stretchability.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, and in particular to a biodegradable agricultural functional film and its preparation method. Background Technology

[0002] In agricultural production, agricultural films are widely used as an important production material for heat preservation, moisture retention, and weed control, playing a vital role in improving crop yield and quality. However, traditional agricultural films are mostly made of non-degradable plastic materials, which leave a large amount of plastic waste in the soil after long-term use, causing serious soil pollution and ecological damage, which does not meet the requirements of sustainable development in modern agriculture.

[0003] With increasing environmental awareness, biodegradable agricultural films have gradually become a research hotspot. However, existing biodegradable agricultural films have certain functional limitations. Most products only have a single degradation function, making it difficult to simultaneously meet multiple agricultural production needs such as anti-aging and anti-fogging. For example, some biodegradable films are easily affected by the external environment during long-term use, leading to aging and damage and shortening their service life. In environments with large temperature and humidity fluctuations, fogging is easily generated on the film surface, affecting light transmittance and hindering crop photosynthesis. At the same time, the high-quality development of modern agriculture has also put forward new requirements for the functionality of agricultural films. Therefore, functional films such as green, blue, red, purple, silver-gray, and black agricultural films have emerged. However, the above-mentioned functional films with basic colors have the following problems during use: the temperature under the film rises sharply in strong sunlight, causing seedlings to be scalded or die; if perforations are made for heat dissipation, the temperature under the film cannot be guaranteed at night or in low-temperature weather, because perforation causes irreversible damage to the agricultural film. How to design an agricultural functional film that can adjust its transmittance according to ultraviolet light and is made of biodegradable and environmentally friendly materials is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a biodegradable agricultural functional film and its preparation method, so as to solve the problem that existing agricultural functional films cannot simultaneously adapt to strong sunlight and nighttime temperature conditions.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a biodegradable agricultural functional film, comprising the following steps: 1) Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, anti-aging agent, tetrabutyl titanate and phosphite are mixed and polymerized to obtain the precursor polymer of the anti-aging layer, which is then made into an anti-aging layer using a blow molding machine. Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, antifogging agent, tetrabutyl titanate and phosphite are mixed and polymerized to obtain the precursor polymer of the antifogging layer, which is then made into an antifogging layer using a blow molding machine. A UV-reversible color-changing pigment precursor is obtained by mixing water, butyl acrylate, photoinitiator, tungstate, glycerol, polyethylene glycol, coloring pigment, dispersant and organic solvent; 2) Laser etching is performed on the surface of the anti-aging layer, and then the UV reversible color-changing pigment precursor is coated on the surface of the anti-aging layer after laser etching to obtain the UV reversible color-changing layer. 3) The layers are combined in the order of anti-aging layer - ultraviolet photochromic layer - anti-fogging layer, and then blown together to form a biodegradable agricultural functional film.

[0006] Preferably, the mass ratio of adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler and anti-aging agent in step 1) is 15:30~45:12~17:30~40:5~10:3~7:2~4; The mass ratio of adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, and antifogging agent is 15:30~45:12~17:30~40:5~10:3~7:2~4.

[0007] Preferably, in step 1), the amount of tetrabutyl titanate added to the anti-aging layer precursor polymer and the anti-fogging layer precursor polymer is independently 0.02~0.12% of the mass of adipic acid, and the amount of phosphite added is independently 0.1~0.6% of the mass of adipic acid.

[0008] Preferably, the anti-aging agent in step 1) includes one or more of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl-p-phenylenediamine and 2,2'-methylenebis(4-methyl-6-tert-butylphenol); The antifogging agent is glyceryl monooleate and / or sorbitan monostearate; The inorganic filler includes one or more of calcium carbonate, magnesium sulfate, talc, potassium sulfate, and mica powder; The polymerization reaction temperature is independently 150~280℃, and the polymerization reaction time is independently 3~6h.

[0009] Preferably, the mass ratio of water, butyl acrylate, photoinitiator, tungstate, glycerol, polyethylene glycol, coloring pigment, dispersant and organic solvent in step 1) is 10~30:30~45:3~6:1~2:5~8:4~10:10~15:0.5~1.5:20~30.

[0010] Preferably, the tungstate in step 1) is Na2WO4; The photoinitiator includes one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and benzoin dimethyl ether; The coloring pigment is carbon black; The dispersant is polyvinyl alcohol; The organic solvent includes one or more of ethanol, acetone, isopropanol, and dipropylene glycol dimethyl ether.

[0011] Preferably, the etching power of the laser etching in step 2) is 1~2W and the scanning rate is 300~600mm / s; The coating method for the ultraviolet reversible color-changing pigment precursor is screen printing; The screen printing process involves a mesh size of 150-300, a printing temperature of 20-30°C, a printing pressure of 1-10 kgf / cm, a printing speed of 200-300 m / min, a printing angle of 30°-50°, and 3-10 overprints.

[0012] Preferably, the blow molding machine in step 3) is a three-layer co-extrusion film machine with a blow molding temperature of 100~200℃.

[0013] The present invention also provides a biodegradable agricultural functional film prepared by the above preparation method, comprising an anti-aging layer, an ultraviolet light reversible color-changing layer, and an anti-fogging layer.

[0014] Preferably, the thickness of the anti-aging layer is 10~50μm, the thickness of the ultraviolet reversible color-changing layer is 5~25μm, and the thickness of the anti-fogging layer is 10~50μm; The width of the biodegradable agricultural functional film is 800~1500mm.

[0015] The present invention has at least the following beneficial effects: 1. The biodegradability of the membrane material stems from the design of the raw material system: the precursor polymers of the anti-aging layer and the anti-fogging layer use adipic acid, 1,4-butanediol, lactic acid, starch, etc., as core raw materials. After polymerization, the membrane material has certain strength and tensile properties. The agricultural functional film produced by subsequent blow molding is relatively flexible and suitable for agricultural production. Lactic acid in the raw materials is a natural biodegradable monomer, and starch is a natural polymer. Both can be decomposed into carbon dioxide and water by enzymes secreted by microorganisms in the natural environment. The polyester segments formed by the polymerization of adipic acid and 1,4-butanediol are also easily broken down into smaller molecules through hydrolysis and biodegradation. At the same time, tetrabutyl titanate acts as a catalyst to promote ester bond formation, and phosphite inhibits oxidative degradation during the polymerization process, ensuring the structural stability of the membrane during its service life and rapid degradation after disposal. This fundamentally solves the soil pollution problem caused by the residue of traditional plastic agricultural films, meeting the needs of green and sustainable agricultural development.

[0016] (2) Anti-aging agents inhibit the aging and degradation of membrane materials caused by light, high temperature, etc. by capturing free radicals and terminating the oxidation chain reaction; inorganic fillers (such as calcium carbonate) are uniformly dispersed in the polymer matrix, which can reflect some ultraviolet rays and reduce the damage of ultraviolet light to the polymer chain; the polymerization reaction is carried out at 150~280℃ to ensure that the monomers react fully to form a stable cross-linked structure, thereby improving the mechanical strength and anti-aging basis of the membrane. The synergistic effect of the three makes the membrane less prone to embrittlement and damage in long-term exposure to sunlight, wind and rain, etc., significantly extending its service life and reducing agricultural production costs.

[0017] (3) The anti-fogging agent is a hydrophilic surfactant that can reduce the surface tension of the membrane, so that water vapor in the air forms a continuous water film on the membrane surface instead of discrete fog droplets, thus avoiding light scattering; the ethylene glycol, polyethylene glycol and other components in the raw materials enhance the hydrophilicity of the membrane and work synergistically with the anti-fogging agent to enhance the anti-fogging durability; the uniformity of the membrane layer controlled by the blow molding process ensures that the anti-fogging agent is distributed in a consistent manner, thus avoiding local fog droplet condensation.

[0018] (4) Under ultraviolet light irradiation, the oxygen vacancies in the crystal structure of tungstate change, achieving a reversible color change, and the degree of color change is positively correlated with the intensity of ultraviolet light; laser etching forms a micro-nano rough structure on the surface of the anti-aging layer, which increases the adhesion of the ultraviolet light color-changing pigment precursor. Detailed Implementation

[0019] This invention provides a method for preparing a biodegradable agricultural functional film, comprising the following steps: 1) Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, anti-aging agent, tetrabutyl titanate and phosphite are mixed and polymerized to obtain the precursor polymer of the anti-aging layer, which is then made into an anti-aging layer using a blow molding machine. Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, antifogging agent, tetrabutyl titanate and phosphite are mixed and polymerized to obtain the precursor polymer of the antifogging layer, which is then made into an antifogging layer using a blow molding machine. A UV-reversible color-changing pigment precursor is obtained by mixing water, butyl acrylate, photoinitiator, tungstate, glycerol, polyethylene glycol, coloring pigment, dispersant and organic solvent; 2) Laser etching is performed on the surface of the anti-aging layer, and then the UV reversible color-changing pigment precursor is coated on the surface of the anti-aging layer after laser etching to obtain the UV reversible color-changing layer. 3) The layers are combined in the order of anti-aging layer - ultraviolet photochromic layer - anti-fogging layer, and then blown together to form a biodegradable agricultural functional film.

[0020] In this invention, the mass ratio of adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, and anti-aging agent in step 1) is 15:30~45:12~17:30~40:5~10:3~7:2~4, preferably 15:33~42:13~16:32~38:6~9:3.5~6.5:2.2~3.8, further preferably 15:35~40:14~15:34~36:7~8:4~6:2.5~3.5, and even more preferably 15:37~38:15:35:7:5:3.

[0021] In this invention, the mass ratio of adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, and antifogging agent is 15:30~45:12~17:30~40:5~10:3~7:2~4, preferably 15:33~42:13~16:32~38:6~9:3.5~6.5:2.2~3.8, further preferably 15:35~40:14~15:34~36:7~8:4~6:2.5~3.5, and even more preferably 15:37~38:15:35:7:5:3.

[0022] In this invention, the amount of tetrabutyl titanate added to the anti-aging layer precursor polymer and the anti-fogging layer precursor polymer in step 1) is independently 0.02~0.12% of the mass of adipic acid, preferably 0.4~1%, more preferably 0.6~0.8%; the amount of phosphite added is independently 0.1~0.6% of the mass of adipic acid, preferably 0.2~0.5%, more preferably 0.3~0.4%.

[0023] In this invention, the anti-aging agent in step 1) includes one or more of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl-p-phenylenediamine, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol).

[0024] In this invention, the anti-fogging agent is glyceryl monooleate and / or sorbitan monostearate.

[0025] In this invention, the inorganic filler includes one or more of calcium carbonate, magnesium sulfate, talc, potassium sulfate, and mica powder.

[0026] In this invention, the temperature of the polymerization reaction is independently 150~280℃, preferably 170~260℃, more preferably 190~240℃, and even more preferably 210~220℃; the time of the polymerization reaction is independently 3~6h, preferably 3.5~5.5h, more preferably 4~5h, and even more preferably 4.5h.

[0027] In this invention, the mass ratio of water, butyl acrylate, photoinitiator, tungstate, glycerol, polyethylene glycol, coloring pigment, dispersant, and organic solvent in step 1) is 10~30:30~45:3~6:1~2:5~8:4~10:10~15:0.5~1.5:20~30, preferably 13~28:32~43:3.5~5.5:1.2~1.8:5.5~7.5:5~9:11~14:0.7~1.3:22~28, further preferably 15~25:35~40:4~5:1.4~1.6:6~7:6~8:12~13:0.9~1.1:24~26, and even more preferably 18~22:36~38:5:1.5:6.5:7:13:1:25.

[0028] In this invention, the tungstate in step 1) is Na2WO4.

[0029] In this invention, the photoinitiator includes one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and benzoin dimethyl ether.

[0030] In this invention, the coloring pigment is carbon black.

[0031] In this invention, the dispersant is polyvinyl alcohol.

[0032] In this invention, the organic solvent includes one or more of ethanol, acetone, isopropanol and dipropylene glycol dimethyl ether.

[0033] In this invention, the etching power of the laser etching in step 2) is 1~2W, preferably 1.2~1.8W, more preferably 1.4~1.6W, and more preferably 1.5W; the scanning rate is 300~600mm / s, preferably 350~550mm / s, more preferably 380~530mm / s, and more preferably 400~500mm / s.

[0034] In this invention, the coating method for the ultraviolet reversible color-changing pigment precursor is screen printing.

[0035] In this invention, the mesh size of the screen printing is 150-300 mesh, preferably 180-260 mesh, more preferably 200-240 mesh, and even more preferably 220 mesh; the printing temperature is 20-30℃, preferably 22-28℃, more preferably 24-26℃, and even more preferably 25℃; the printing pressure is 1-10 kgf / cm², preferably 3-8 kgf / cm², more preferably 4-6 kgf / cm², and even more preferably 5 kgf / cm²; the printing speed is 200-300 m / min, preferably 220-280 m / min, more preferably 240-260 m / min, and even more preferably 250 m / min; the printing angle is 30°-50°, preferably 35°-45°, more preferably 38°-42°, and even more preferably 40°; and the number of overprints is 3-10, preferably 4-8, more preferably 5-7, and even more preferably 6.

[0036] In this invention, the blow molding machine mentioned in step 3) is a three-layer co-extrusion film machine, and the blow molding temperature is 100~200℃, preferably 120~180℃, more preferably 140~160℃, and even more preferably 150℃.

[0037] The present invention also provides a biodegradable agricultural functional film prepared by the above preparation method, comprising an anti-aging layer, an ultraviolet light reversible color-changing layer, and an anti-fogging layer.

[0038] In this invention, the thickness of the anti-aging layer is 10~50μm, preferably 20~40μm, more preferably 25~35μm, and even more preferably 30μm; the thickness of the ultraviolet reversible color-changing layer is 5~25μm, preferably 10~20μm, more preferably 12~18μm, and even more preferably 15μm; the thickness of the anti-fogging layer is 10~50μm, preferably 20~40μm, more preferably 25~35μm, and even more preferably 30μm.

[0039] The width of the biodegradable agricultural functional film is 800~1500mm, preferably 900~1300mm, more preferably 1000~1200mm, and even more preferably 1100mm.

[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] 1) Preparation of the anti-aging layer: Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler (calcium carbonate), and anti-aging agent (2,2,4-trimethyl-1,2-dihydroquinoline polymer) were weighed according to a mass ratio of 15:37:15:35:7:5:3. Then, 0.6% of tetrabutyl titanate and 0.3% of phosphite by mass of adipic acid were added. After these raw materials were thoroughly mixed, a polymerization reaction was carried out at 210°C for 4.5 hours to obtain the precursor polymer of the anti-aging layer. The anti-aging layer was then formed by blow molding.

[0043] Preparation of anti-fogging layer: Weigh adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, and inorganic filler (calcium carbonate) according to the same mass ratio as above. Replace the anti-aging agent with an anti-fogging agent (glyceryl monooleate). The amounts of tetrabutyl titanate and phosphite added, as well as the temperature and time of the polymerization reaction, are the same as when preparing the anti-aging layer. Obtain the precursor polymer of the anti-fogging layer, and then use a blow molding machine to make it into an anti-fogging layer.

[0044] 2) Water, butyl acrylate, photoinitiator (selected as 2-hydroxy-2-methyl-1-phenyl-1-propanone), Na2WO4, glycerol, polyethylene glycol, coloring pigment (carbon black), dispersant (polyvinyl alcohol), and organic solvent (ethanol) are mixed in a mass ratio of 18:36:5:1.5:6.5:7:13:1:25 and stirred thoroughly to obtain the UV reversible color-changing pigment precursor.

[0045] 3) The surface of the anti-aging layer was laser-etched with an etching power of 1.5W and a scanning rate of 400mm / s. After etching, the UV-reversible color-changing pigment precursor was coated onto the etched surface using screen printing. The screen printing parameters were: 220 mesh, 25℃, 5kgf / cm², 250m / min, 40°, and 6 overprints. The resulting UV-reversible color-changing layer was obtained.

[0046] 4) The layers are combined in the following order: anti-aging layer - UV photochromic layer - anti-fogging layer. A three-layer co-extrusion film is then produced at a blow molding temperature of 150℃ to create a biodegradable agricultural functional film. In this functional film, the anti-aging layer is 30μm thick, the UV reversible photochromic layer is 15μm thick, the anti-fogging layer is 30μm thick, and the film width is 1100mm.

[0047] Example 2

[0048] 1) Preparation of anti-aging layer: Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler (talc), and anti-aging agent (N-isopropyl-N'-phenyl-p-phenylenediamine) were weighed in a mass ratio of 15:35:14:34:7:4:2.5. 0.7% tetrabutyl titanate and 0.35% phosphite by mass of adipic acid were added. After mixing, the mixture was polymerized at 220℃ for 4 hours to obtain the precursor polymer of the anti-aging layer. The anti-aging layer was then formed by blow molding.

[0049] Preparation of anti-fogging layer: Weigh the corresponding raw materials according to the above mass ratio, replace the anti-aging agent with anti-fogging agent (sorbitan monostearate), and prepare the anti-fogging layer under the same conditions as the preparation of the anti-aging layer.

[0050] 2) Water, butyl acrylate, photoinitiator (1-hydroxycyclohexylphenyl ketone), Na2WO4, glycerol, polyethylene glycol, carbon black, polyvinyl alcohol and organic solvent (acetone) are mixed in a mass ratio of 25:40:4:1.6:7:8:12:1.1:26 to obtain a UV reversible color-changing pigment precursor.

[0051] 3) The surface of the anti-aging layer is laser-etched at a power of 1.6W and a scanning rate of 530mm / s. Then, a 240-mesh screen is used to overprint the substrate 7 times at 26℃, 6kgf / cm² pressure, 260m / min speed, and 42° angle to coat the substrate onto the etched surface, thus obtaining a UV reversible color-changing layer.

[0052] 4) Combine the layers in sequence and use a three-layer co-extrusion film machine to make a film at 160℃, wherein the anti-aging layer is 35μm thick, the UV reversible color-changing layer is 18μm thick, the anti-fogging layer is 35μm thick, and the width is 1200mm.

[0053] Example 3

[0054] 1) Preparation of anti-aging layer: Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler (a mixture of magnesium sulfate and potassium sulfate, mass ratio 1:1) and anti-aging agent (2,2'-methylenebis(4-methyl-6-tert-butylphenol)) were weighed according to the mass ratio of 15:42:16:38:9:6.5:3.8. 1% tetrabutyl titanate and 0.5% phosphite by mass of adipic acid were added. After mixing, the mixture was polymerized at 260℃ for 5.5h to obtain the precursor polymer of the anti-aging layer. The anti-aging layer was then formed by blow molding.

[0055] Preparation of anti-fogging layer: Weigh the raw materials according to the above mass ratio, replace the anti-aging agent with anti-fogging agent (a mixture of glyceryl monooleate and sorbitan monostearate, mass ratio 1:1), and keep other conditions the same to prepare the anti-fogging layer.

[0056] 2) Water, butyl acrylate, photoinitiator (benzoin dimethyl ether), Na2WO4, glycerol, polyethylene glycol, carbon black, polyvinyl alcohol, and organic solvent (a mixture of isopropanol and dipropylene glycol dimethyl ether in a mass ratio of 1:1) are mixed in a mass ratio of 28:43:5.5:1.8:7.5:9:14:1.3:28 to obtain a UV-reversible color-changing pigment precursor.

[0057] 3) The surface of the anti-aging layer is laser-etched with a power of 1.8W and a scanning rate of 550mm / s. Then, it is overprinted 8 times with a 260-mesh screen at 28℃, 8kgf / cm² pressure, 280m / min speed and 45° angle to coat the precursor and obtain the UV reversible color-changing layer.

[0058] 4) After being assembled in sequence, the film is made at 180°C using a three-layer co-extrusion film machine. The anti-aging layer is 40μm thick, the UV reversible color-changing layer is 20μm thick, the anti-fogging layer is 40μm thick, and the width is 1300mm.

[0059] Test method: The biodegradable agricultural functional films prepared in Examples 1-3 were subjected to performance tests, and the film thickness, tensile properties and weather resistance were tested in accordance with the national standard "Polyethylene blown agricultural ground covering film".

[0060] Transmittance data were tested on samples from Examples 1 to 3. The ordinary plastic film used in the control group was purchased from Shandong Changhao Plastics Co., Ltd.

[0061] Before ultraviolet light irradiation, the transmittance was recorded using a marine spectrometer. Then, both samples were placed at 5 mW / cm². 2 After irradiation with 365nm ultraviolet light for 1 minute, relevant transmittance data were recorded using a marine spectrometer. A reference wavelength of 350nm was used to compare the transmittance data.

[0062] Its degradation performance within 120 days was tested according to the national standard for fully biodegradable agricultural ground cover film (GB / T 35795-2017).

[0063] The specific test data is shown in Table 1.

[0064] Table 1. Performance test results of biodegradable agricultural functional films and ordinary mulch films prepared in Examples 1-3

[0065] As shown in Table 1, the biodegradable agricultural functional films prepared in Examples 1-3 can be decomposed by microorganisms in the natural environment within 120°C after use, exhibiting a long service life, meeting production needs, and causing no environmental damage. Furthermore, these biodegradable agricultural functional films possess excellent color-changing properties, capable of changing color under strong light conditions, thus preventing plants under the film from being scalded.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a biodegradable agricultural functional film, characterized in that, Includes the following steps: 1) Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, anti-aging agent, tetrabutyl titanate and phosphite are mixed and polymerized to obtain the precursor polymer of the anti-aging layer, which is then made into an anti-aging layer using a blow molding machine. Adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, antifogging agent, tetrabutyl titanate and phosphite are mixed and polymerized to obtain the precursor polymer of the antifogging layer, which is then made into an antifogging layer using a blow molding machine. A UV-reversible color-changing pigment precursor is obtained by mixing water, butyl acrylate, photoinitiator, tungstate, glycerol, polyethylene glycol, coloring pigment, dispersant and organic solvent; 2) Laser etching is performed on the surface of the anti-aging layer, and then the UV reversible color-changing pigment precursor is coated on the surface of the anti-aging layer after laser etching to obtain the UV reversible color-changing layer. 3) The layers are combined in the order of anti-aging layer - ultraviolet photochromic layer - anti-fogging layer, and then blown together to form a biodegradable agricultural functional film.

2. The method for preparing a biodegradable agricultural functional film according to claim 1, characterized in that, The mass ratio of adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler and anti-aging agent in step 1) is 15:30~45:12~17:30~40:5~10:3~7:2~4; The mass ratio of adipic acid, 1,4-butanediol, terephthalic acid, ethylene glycol, lactic acid, starch, inorganic filler, and antifogging agent is 15:30~45:12~17:30~40:5~10:3~7:2~4.

3. The method for preparing a biodegradable agricultural functional film according to claim 2, characterized in that, In step 1), the amount of tetrabutyl titanate added to the anti-aging layer precursor polymer and the anti-fogging layer precursor polymer is independently 0.02~0.12% of the mass of adipic acid, and the amount of phosphite added is independently 0.1~0.6% of the mass of adipic acid.

4. A method for preparing a biodegradable agricultural functional film according to any one of claims 1 to 3, characterized in that, The anti-aging agent mentioned in step 1) includes one or more of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl-p-phenylenediamine and 2,2'-methylenebis(4-methyl-6-tert-butylphenol); The antifogging agent is glyceryl monooleate and / or sorbitan monostearate; The inorganic filler includes one or more of calcium carbonate, magnesium sulfate, talc, potassium sulfate, and mica powder; The polymerization reaction temperature is independently 150~280℃, and the polymerization reaction time is independently 3~6h.

5. The method for preparing a biodegradable agricultural functional film according to claim 4, characterized in that, The mass ratio of water, butyl acrylate, photoinitiator, tungstate, glycerol, polyethylene glycol, coloring pigment, dispersant and organic solvent in step 1) is 10~30:30~45:3~6:1~2:5~8:4~10:10~15:0.5~1.5:20~30.

6. The method for preparing a biodegradable agricultural functional film according to claim 5, characterized in that, The tungstate mentioned in step 1) is Na2WO4; The photoinitiator includes one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and benzoin dimethyl ether; The coloring pigment is carbon black; The dispersant is polyvinyl alcohol; The organic solvent includes one or more of ethanol, acetone, isopropanol, and dipropylene glycol dimethyl ether.

7. The method for preparing a biodegradable agricultural functional film according to claim 6, characterized in that, The etching power of the laser etching described in step 2) is 1~2W, and the scanning rate is 300~600mm / s; The coating method for the ultraviolet reversible color-changing pigment precursor is screen printing; The screen printing process involves a mesh size of 150-300, a printing temperature of 20-30°C, a printing pressure of 1-10 kgf / cm, a printing speed of 200-300 m / min, a printing angle of 30°-50°, and 3-10 overprints.

8. The method for preparing a biodegradable agricultural functional film according to claim 7, characterized in that, The blow molding machine mentioned in step 3) is a three-layer co-extrusion film machine with a blow molding temperature of 100~200℃.

9. The biodegradable agricultural functional film prepared by the method according to any one of claims 1 to 8 is characterized in that, It includes an anti-aging layer, a UV reversible color-changing layer, and an anti-fogging layer.

10. A biodegradable agricultural functional film according to claim 9, characterized in that, The thickness of the anti-aging layer is 10~50μm, the thickness of the ultraviolet reversible color-changing layer is 5~25μm, and the thickness of the anti-fogging layer is 10~50μm; The width of the biodegradable agricultural functional film is 800~1500mm.

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