Biological protection full-degradation soil moisture conservation agricultural film and preparation method thereof

Abstract

The invention discloses a biological protection full-degradable soil moisture conservation agricultural film and a preparation method thereof, and belongs to the technical field of degradable agricultural films. The preparation method of the agricultural film comprises the following steps: blending and extruding titanium dioxide and polycaprolactone to prepare a PCL-coated TIO film; the PCL-coated TIO film is coated with plant essential oil, and an antibacterial and insect-proof layer is prepared; the preparation method comprises the following steps: uniformly mixing silicon dioxide, a zinc salt solution and an imidazole ligand, and carrying out ultrasonic microwave reaction to prepare a ZIF coated SiO2 hybrid; the ZIF coated SiO2 hybrid and dopamine are stirred and mixed, and an active agent is obtained; polylactic acid and layered filler are co-extruded and mixed to prepare a PLA film, and the PLA film is coated with an active agent to prepare an active insect-proof layer; the antibacterial insect-proof layer and the active insect-proof layer are compounded in situ to prepare the biological protection full-degradable soil moisture conservation agricultural film. The agricultural film prepared by the invention can simultaneously realize the functions of temperature increasing, humidity increasing, antibiosis and insect prevention.

Description

Technical Field

[0001] The present invention relates to the technical field of degradable agricultural films, and more specifically to a biological protection fully degradable moisture-retaining agricultural film and a preparation method thereof. Background Art

[0002] In addition to protecting crops from adverse growth conditions such as bad weather, insects and birds, the use of agricultural films can increase surface temperature, retain moisture and promote the growth of plant seedlings and roots. Agricultural films have become the third largest agricultural production material after fertilizers and pesticides.

[0003] The agricultural films currently used are mostly made of chemical fibers, and their main components are polyethylene or polyvinyl chloride, which can remain in the field for decades without being degraded. Years of use have led to the accumulation of broken films in the soil plow layer year by year, causing soil compaction, poor permeability, obstructed root growth, and reduced yields of subsequent crops. Regardless of the crops covered, all covered soils will have residual film.

[0004] The main varieties that have been commercially developed include poly(butylene succinate) [PBS], polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL) and poly(butylene adipate-co-terephthalate) [PBAT]. They can be degraded by soil microorganisms within a period of time after use, which can better solve the pollution problem caused by traditional agricultural films. Existing degradable agricultural film products are mainly committed to the realization of warming and humidifying functions. However, high temperature and high humidity environments are prone to breeding toxic bacteria, resulting in poor growth of some plants. In addition, the pest control effect is poor, which greatly limits the practical application of biodegradable plastic agricultural films. Summary of the invention

[0005] In view of the above problems, the present invention provides a bioprotective and fully degradable moisture-retaining agricultural film and a preparation method thereof. The prepared agricultural film can simultaneously achieve the functions of increasing temperature and humidity and preventing bacteria and insects.

[0006] The first object of the present invention is to provide a method for preparing a bioprotective fully degradable moisture-retaining agricultural film, comprising the following steps:

[0007] Titanium dioxide and polycaprolactone were blended and extruded to prepare a PCL@TIO film; plant essential oil was coated on the PCL@TIO film to prepare an antibacterial and insect-proof layer.

[0008] After silica, zinc salt solution and imidazole ligand are evenly mixed, ultrasonic microwave reaction is carried out. During the reaction, the zinc salt solution and imidazole ligand react to prepare zeolite imidazolate framework structure material, and silica is coated on the surface of the zeolite imidazolate framework structure material to prepare ZIF@SiO2 hybrid.

[0009] The ZIF@SiO2 hybrid and dopamine are stirred and mixed. During the stirring process, dopamine self-polymerizes to form polydopamine, and the polydopamine adheres to the surface of the ZIF@SiO2 hybrid to obtain an active agent.

[0010] The polylactic acid and the layered filler are co-extruded to prepare a PLA film, and the active agent is coated on the PLA film to prepare an active insect-proof layer.

[0011] The antibacterial and insect-proof layer and the active insect-proof layer are in situ composited to obtain a biological protection and fully degradable moisture-retaining agricultural film.

[0012] In a preferred embodiment of the present invention, the mass ratio of titanium dioxide to polycaprolactone is 1 to 10:100. For example, the mass ratio of titanium dioxide to polycaprolactone is 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0013] In a preferred embodiment of the present invention, the mass ratio of ZIF@SiO2 hybrid to dopamine is 1 to 10:1, for example, the mass ratio of ZIF@SiO2 hybrid to polydopamine is 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0014] The ultrasonic frequency is 20 kHz to 100 kHz. For example, the ultrasonic frequency is 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, 100 kHz, etc.

[0015] The ultrasonic time is 3 min to 60 min, for example, the ultrasonic time is 3 min, 5 min, 9 min, 15 min, 23 min, 33 min, 45 min, 55 min, 60 min, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0016] In a preferred embodiment of the present invention, the mass ratio of polylactic acid to the layered filler is 100:1-10. For example, the mass ratio of polylactic acid to the layered filler is 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, etc.

[0017] The coating thickness of the active agent is 0.01μm to 3μm, for example, the coating thickness is 0.01μm, 0.05μm, 0.1μm, 0.5μm, 1μm, 2μm, 3μm, etc.; but it is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0018] In a preferred embodiment of the present invention, the thickness ratio of the antibacterial and insect-proof layer to the active insect-proof layer is 0.2-5:1. For example, the thickness ratio of the antibacterial and insect-proof layer to the active insect-proof layer is 0.2:1, 0.6:1, 1:1, 1.4:1, 1.8:1, 2.2:1, 2.6:1, 3:1, 3.4:1, 3.8:1, 4.2:1, 4.6:1, 5:1, etc.; but it is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0019] In a preferred embodiment of the present invention, the molar ratio of the imidazole ligand to the zinc salt is 1 to 10:1; for example, the molar ratio of the imidazole ligand to the zinc salt is 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.;

[0020] The molar ratio of zinc salt to SiO2 is 8:1 to 10; for example, the molar ratio of zinc salt to SiO2 is 8:1, 8:2, 8:3, 8:4, 8:5, 8:6, 8:7, 8:8, 8:9, 8:10, etc.

[0021] When preparing the ZIF@SiO2 hybrid, the output power of the ultrasonic microwave reaction is 500W to 1000W; for example, the output power is 500W, 600W, 700W, 800W, 900W, 1000W, etc.

[0022] The ultrasonic frequency is 20 kHz to 100 kHz. For example, the ultrasonic frequency is 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, 100 kHz, etc.

[0023] The reaction temperature is 80°C to 200°C, for example, the reaction temperature is 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, etc.

[0024] The reaction time is 5 min to 40 min. For example, the reaction time is 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0025] In a preferred embodiment of the present invention, the plant essential oil is at least one of eucalyptus oil, peppermint oil, thyme oil, turpentine oil, carnation oil, and black pepper oil, and the coating thickness is 0.01 μm to 3 μm; for example, the coating thickness is 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, etc.; but it is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0026] In a preferred embodiment of the present invention, titanium source, alcohol solvent and water are mixed and then subjected to ultrasonic microwave reaction to obtain titanium dioxide.

[0027] The volume ratio of the titanium source, the alcohol solvent and water is 1 to 2:5:1; for example, the volume ratio of the titanium source, the alcohol solvent and water is 1:5:1, 1.2:5:1, 1.4:5:1, 1.6:5:1, 1.8:5:1, 2:5:1, etc.

[0028] When preparing titanium dioxide, the microwave output power of the ultrasonic microwave reaction is 500W to 1000W, for example, the output power is 500W, 600W, 700W, 800W, 900W, 1000W, etc.

[0029] The ultrasonic frequency is 20 kHz to 100 kHz. For example, the ultrasonic frequency is 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, 100 kHz, etc.

[0030] The reaction temperature is 80°C to 200°C, for example, the reaction temperature is 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, etc.

[0031] The reaction time is 3 min to 40 min, and the reaction time is 3 min, 5 min, 9 min, 15 min, 23 min, 33 min, 40 min, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0032] The second object of the present invention is to provide a bioprotective and fully degradable moisture-retaining agricultural film prepared by the above-mentioned preparation method.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention provides a method for preparing a bioprotective and fully degradable moisture-retaining agricultural film, wherein titanium dioxide nanoparticles and PCL are co-extruded to prepare a PCL@TIO film, and plant essential oil is applied by micro-gravure coating to prepare an antibacterial and insect-proof layer; the introduction of titanium dioxide in the antibacterial and insect-proof layer can improve the light-induced antibacterial performance of the agricultural film, thereby inhibiting the growth of bacteria in the agricultural film, and reflecting ultraviolet light under sunlight to drive away harmful insects, thereby achieving the effect of antibacterial and insect-proofing. In addition, the coating of plant essential oil can effectively prevent and control insect pests inside the agricultural film.

[0035] The super-hydrophobic active hybrid ZIF@SiO2 assisted by silica dispersion was prepared in situ by ultrasonic microwave, and the super-dispersed active agent was prepared by combining it with polydopamine through ultrasonic dispersion technology, and coated on a high-barrier PLA film to prepare an active insect-proof layer; the active free radicals generated by ZIF can repel and kill insects outside the agricultural film, and silica and ZIF improve the hydrophobicity of the agricultural film, which can effectively block the evaporation of crop water and thus play a humidification role. Polydopamine has excellent infrared absorption and photothermal conversion capabilities, which can significantly improve the warming performance of the agricultural film. The antibacterial and insect-proof layer and the active insect-proof layer are composited in situ, and finally a degradable composite agricultural film that simultaneously achieves warming and humidification and antibacterial and insect-proof functions is obtained.

[0036] (2) The agricultural film prepared by the present invention has an antibacterial efficiency of 89%-100%, an insect-proof efficiency of 83%-100%, a water contact angle of the warming and humidifying layer of 132.1°-152.5°, and an environmental humidity of the area covered by the agricultural film is 83%RH-93%RH. The ambient temperature can be increased by 7.4℃-13.2℃. The breaking strength of the agricultural film is 28.9MPa-34.7MPa, and the mass loss after being buried in the soil for 3 months exceeds 10.7%. The agricultural film not only has the advantages of antibacterial, insect-proof, warming and humidifying, but also plays a role in increasing the yield and quality of crops. The agricultural film also has good degradability and has no significant effect on soil and crops. It is expected to replace ordinary agricultural films and be promoted in farmland, reduce the pollution of soil caused by agricultural films, and accelerate the development of modern ecological agriculture. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a flow chart for preparing the bioprotective and fully degradable moisture-retaining agricultural film.

[0038] Figure 2 The present invention is a flow chart for preparing titanium dioxide.

[0039] Figure 3 Flow chart of the preparation of ZIF@SiO2 hybrids of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] As described in the background technology, the existing degradable agricultural films mainly study the functions of warming and humidifying, but the high temperature and high humidity environment will cause bacteria to breed, affect the growth of plants, and the pest control effect is poor. Based on this, the present invention develops a degradable agricultural film that can simultaneously achieve warming and humidifying and antibacterial and insect-proof functions. The present invention uses ultrasonic microwaves to assist in the preparation of titanium dioxide nanoparticles, which are blended and extruded with PCL to prepare PCL@TIO film, and plant essential oils are applied by micro-gravure coating to prepare an antibacterial and insect-proof layer; the super-hydrophobic active hybrid ZIF@SiO2 assisted by silica is prepared in situ by ultrasonic microwaves, and the super-dispersed active agent is prepared by ultrasonic dispersion technology with polydopamine, and coated on a high-barrier PLA film to prepare an active insect-proof layer; the antibacterial and insect-proof layer and the active insect-proof layer are composited in situ to finally obtain a degradable composite agricultural film with biological protection function. The composite agricultural film prepared by the present invention has the advantages of antibacterial, insect-proof, temperature-increasing and humidifying, and plays a role in increasing the yield and quality of crops. The agricultural film also has good degradability and has no significant effect on soil and crops. It is expected to replace ordinary agricultural films and be promoted in farmland, reduce the pollution of soil caused by agricultural films, and accelerate the development of modern ecological agriculture. The specific technical scheme is as follows:

[0042] A method for preparing a bioprotective fully degradable moisture-retaining agricultural film, the preparation process is as follows Figure 1 As shown, the following steps are included:

[0043] Titanium dioxide and polycaprolactone were blended and extruded to prepare a PCL@TIO film; plant essential oil was coated on the PCL@TIO film to prepare an antibacterial and insect-proof layer.

[0044] By introducing titanium dioxide into the PCL matrix through co-extrusion, the light-induced antibacterial properties of the agricultural film can be improved, effectively inhibiting the growth of bacteria in the agricultural film, and can also reflect ultraviolet light under sunlight to repel harmful insects. The plant essential oil coating can make the agricultural film show multiple modes of action on insects and mites, such as contact killing, fumigation, repelling, killing eggs, and inhibiting growth and development, effectively improving the pest control effect of the agricultural film.

[0045] After the silicon dioxide, zinc salt solution and imidazole ligand are uniformly mixed, an ultrasonic microwave reaction is carried out. During the reaction, the zinc salt solution and the imidazole ligand react to prepare a zeolite imidazole ester framework structure material, and the silicon dioxide is coated on the surface of the zeolite imidazole ester framework structure material to prepare a ZIF@SiO2 hybrid. The preparation process is as follows: Figure 2 shown.

[0046] The ZIF@SiO2 hybrid and dopamine are stirred and mixed. During the stirring process, dopamine self-polymerizes to form polydopamine, and the polydopamine adheres to the surface of the ZIF@SiO2 hybrid to obtain an active agent. Polylactic acid and layered fillers are co-extruded to prepare a PLA film, and the active agent is coated on the PLA film to prepare an active insect-proof layer.

[0047] Ultrasonic microwave reaction effectively improves the reactivity of silica, zinc salt solution, and imidazole ligand, and can evenly carry out crystal doping to form a silica-coated ZIF@SiO2 hybrid with a core-shell structure. The core-shell structure ZIF@SiO2 hybrid can prevent ZIF from agglomerating and give full play to the ability of ZIF to produce active free radicals and kill pests. In addition, ZIF@SiO2 provides superhydrophobicity for agricultural film, which can prevent water evaporation and increase the temperature and humidity of crops.

[0048] Through the self-polymerization of dopamine, polydopamine with adhesive properties is produced and adhered to the surface of the ZIF@SiO2 hybrid. On the one hand, polydopamine can act as an adhesive to prevent the hybrid from falling off, and on the other hand, it can act as a dispersant to prevent the hybrid from agglomerating. In addition, the wide light absorption and excellent light-to-heat conversion ability of polydopamine can provide insulation for agricultural film. Specifically, dopamine self-polymerization is under alkaline conditions and under the action of oxygen, and dopamine oxidative self-polymerization obtains polydopamine, that is, the catechol group of dopamine is oxidized to form dopamine benzoquinone to form polydopamine.

[0049] The antibacterial and insect-proof layer is used as the inner layer and the active insect-proof layer is used as the outer layer, and a biological protective and fully degradable moisture-retaining agricultural film is prepared by in-situ composite.

[0050] The antibacterial and insect-proof layer as the inner layer can give full play to the light-induced antibacterial properties of titanium dioxide and effectively inhibit the growth of bacteria in the agricultural film. The plant essential oil coating provides an insect-proof effect inside the agricultural film. The active insect-proof layer as the outer layer can repel and kill insects outside the agricultural film due to the active free radicals produced by ZIF, thereby achieving a dual biological protection effect inside and outside the agricultural film. The active insect-proof layer has high barrier properties, hydrophobicity and light absorption capabilities, and can provide support, waterproofing and heat preservation capabilities for the agricultural film.

[0051] The bioprotective and fully degradable moisture-retaining agricultural film prepared by the present invention comprises an antibacterial and insect-proof layer and an active antibacterial layer; specifically: the degradable material used in the antibacterial and insect-proof layer is PCL, which has good biodegradability, excellent mechanical properties, and has the function of being able to stably release drugs for a long time; the added titanium dioxide has light-induced antibacterial properties on the one hand, which can effectively inhibit the growth of bacteria in the agricultural film, and on the other hand, can reflect ultraviolet rays under sunlight to repel harmful insects, thereby achieving the effect of pest control; the coated plant essential oil exhibits multiple modes of action on insects and mites, such as contact killing, fumigation, repelling, egg killing, and growth and development inhibition, and is highly selective and safe for humans and animals. Most of them are non-toxic to natural enemies, can be completely degraded in the environment, and will not produce residues, so they are environmentally friendly pesticides.

[0052] The biodegradable material used for the active antibacterial layer is PLA, which has excellent mechanical properties, good biocompatibility, and is non-toxic and mild; ZIF can produce a large number of active free radicals under light conditions, which have a killing effect on harmful insects; silica-assisted dispersion can prevent ZIF from agglomerating, so that it can effectively play an active insect repellent role. In addition, the synergistic effect of silica and ZIF can effectively improve the hydrophobicity of agricultural film, block water evaporation, and increase the temperature and humidity of crops; polydopamine can act as an adhesive to prevent the hybrid from falling off, and can act as a dispersant to prevent the hybrid from agglomerating. In addition, its wide light absorption and superior photothermal conversion ability can provide thermal insulation.

[0053] Furthermore, the mass ratio of titanium dioxide to polycaprolactone is 1 to 10: 100. During the preparation process, titanium dioxide and polycaprolactone need to be weighed according to the above mass ratio. If the above parameter range is exceeded, when the mass ratio of the two is too large, the titanium dioxide loading amount will be insufficient, and when the mass ratio of the two is too small, the titanium dioxide particles will agglomerate in the matrix, both of which will affect the antibacterial and insect repellent effect of the agricultural film.

[0054] Furthermore, the plant essential oil is at least one of eucalyptus oil, peppermint oil, thyme oil, turpentine oil, carnation oil, and black pepper oil, and the coating thickness is 0.01 μm to 3 μm. During the preparation process, the coating thickness of the plant essential oil needs to be applied according to the above parameter range. If it exceeds the above parameter range, the coating thickness of the plant essential oil is too large, which will increase the cost and weight of the agricultural film and affect the covering effect; the coating thickness of the plant essential oil is too small, which will affect the insect pest prevention ability of the agricultural film.

[0055] Furthermore, the molar ratio of the imidazole ligand to the zinc salt is 1 to 10:1, and the molar ratio of the zinc salt to SiO2 is 8:1 to 10. During the preparation process, the imidazole ligand and the zinc salt need to be weighed according to the above molar ratio. If it exceeds the above parameter range, when the molar ratio of the imidazole ligand to the zinc salt is too high, the growth of the ZIF-8 crystal nucleus will be delayed, resulting in the synthesized ZIF-8 particle size being too small, resulting in its ability to generate active free radicals being weakened; when the molar ratio of the imidazole ligand to the zinc salt is too low, it will cause Zn 2+ It cannot fully participate in the reaction, affecting the yield of ZIF-8 crystals.

[0056] During the preparation process, the imidazole ligand and the zinc salt need to be weighed according to the above-mentioned molar ratio. If it exceeds the above parameter range, the molar ratio of zinc salt to SiO2 is too large, which will cause agglomeration of ZIF crystals; and the molar ratio of zinc salt to SiO2 is too small, which will weaken the ability of ZIF to produce active free radicals.

[0057] Furthermore, when preparing the ZIF@SiO2 hybrid, the output power of the ultrasonic microwave reaction is 500W-1000W, the ultrasonic frequency is 20kHz-100kHz, the reaction temperature is 80℃-200℃, and the reaction time is 5min-40min. During the preparation process, the output power, ultrasonic frequency, reaction temperature and reaction time of the ultrasonic microwave reaction should be controlled within the above parameter range. If the above parameter range is exceeded, when the output power, ultrasonic frequency and temperature are too high, the time is too long, the ZIF@SiO2 hybrid will grow excessively, and the internal structure of the reactant will be damaged, affecting the generation of its active free radicals; when the output power, ultrasonic frequency and temperature are too low, the time is too short, the reaction will be insufficient, the growth of the ZIF@SiO2 hybrid will not be complete, and its active antibacterial and insect repellent ability will be fully exerted.

[0058] Furthermore, the mass ratio of ZIF@SiO2 hybrid to dopamine is 1 to 10:1, the ultrasonic frequency is 20kHz to 100kHz, and the ultrasonic time is 3min to 60min. Too large a mass ratio of ZIF@SiO2 hybrid to dopamine will cause the ZIF@SiO2 hybrid to agglomerate; too small a mass ratio will affect the active antibacterial and insecticidal ability and hydrophobicity of the agricultural film. Too high an ultrasonic frequency and too long an ultrasonic time will destroy the structure of the ZIF@SiO2 hybrid; too low an ultrasonic frequency and too short an ultrasonic time will cause the ZIF@SiO2 to agglomerate and also affect the adhesion of the ZIF@SiO2 hybrid. The dopamine used in the present invention is dopamine hydrochloride.

[0059] Furthermore, the titanium source, alcohol solvent and water are mixed and then subjected to ultrasonic microwave reaction to obtain titanium dioxide. Figure 3As shown, when preparing titanium dioxide, the microwave output power of the ultrasonic microwave reaction is 500W to 1000W, the ultrasonic frequency is 20kHz to 100kHz, the reaction temperature is 80°C to 200°C, and the reaction time is 3min to 40min.

[0060] Ultrasonic microwave reaction is a new method that combines ultrasonic dispersion with microwave hydrothermal synthesis. First, ultrasonic waves are used to generate mechanical vibrations, cavitation effects, thermal effects, and chemical effects in liquids, acting on titanium source particle clusters, breaking them up through shear and compression forces. At the same time, the high-pressure shock waves generated by the instantaneous collapse of bubbles formed by the cavitation effect further promote particle dispersion, while the thermal and chemical effects enhance the dispersion effect by changing the surface properties of the particles. Then, the microwave field is used as a heat source. Under high temperature and high pressure conditions, the medium water is in a critical state, and the reaction activity of the titanium source and alcohol solvent in water is greatly improved. Under microwave heating conditions, the temperature of the entire reaction system can instantly reach the crystallization temperature, greatly accelerating the speed of synthesis and crystallization, shortening the crystallization time, and efficiently preparing nano-titanium dioxide particles with regular structure and uniform size. Titanium dioxide with regular structure has a stronger ability to produce active free radicals induced by light, and the active antibacterial and insect repellent effect of agricultural film is better.

[0061] When preparing titanium dioxide, the microwave output power of the ultrasonic microwave reaction is 500W to 1000W, the ultrasonic frequency is 20kHz to 100kHz, the reaction temperature is 80℃ to 200℃, and the reaction time is 3min to 40min. During the preparation process, the output power, ultrasonic frequency, reaction temperature and reaction time of the ultrasonic microwave reaction should be controlled within the above parameter range. If the above parameter range is exceeded, when the output power, ultrasonic frequency and temperature are too high, the time is too long, it will cause excessive growth of titanium dioxide crystals, and will also damage the internal structure of the reactants, affecting its light-induced antibacterial performance; when the output power, ultrasonic frequency and temperature are too low, the time is too short, it will lead to insufficient reaction and incomplete growth of titanium dioxide crystals, affecting the full play of its antibacterial and insect repellent functions.

[0062] Furthermore, the mass ratio of polylactic acid to layered filler is 100:1-10, and the coating thickness of the active agent is 0.01μm-3μm. If the mass ratio of polylactic acid to layered filler is too large, the agricultural film cannot guarantee sufficient support and barrier properties; if the mass ratio is too small, the cost and weight of the agricultural film will increase, and the strength and rigidity of the agricultural film will also be reduced. If the coating thickness of the active agent is too large, the cost and weight of the agricultural film will increase, affecting the covering effect; if the coating thickness is too small, the active antibacterial and insect repellent ability of the agricultural film will be affected. The layered filler is at least one of boron nitride nanosheets, graphene nanosheets, nanomica sheets and natural montmorillonite. The layered filler has excellent barrier properties, good chemical stability and antioxidant properties, etc., and can improve multiple mechanical properties and thermodynamic properties of the film, including creep resistance, tensile strength, puncture resistance, aging resistance, heat deformation temperature, etc. The sheet diameter of the layered filler is 1μm-2μm. If the sheet diameter is too large or too small, it will affect the barrier and mechanical properties of the film.

[0063] Furthermore, the thickness ratio of the antibacterial and insect-proof layer to the active insect-proof layer is 0.2 to 5:1. If the thickness of the antibacterial and insect-proof layer is too large, the cost and weight of the agricultural film will be increased, and the covering effect will be affected; if the thickness of the antibacterial and insect-proof layer is too small, the antibacterial and insect-proof ability of the agricultural film will be affected. If the thickness of the active insect-proof layer is too large, the cost and weight of the agricultural film will be increased, and the temperature and humidity inside the agricultural film will be too high, which is not conducive to the normal growth of crops; if the thickness of the active insect-proof layer is too small, the active insect-proof and warming and humidifying abilities of the agricultural film will be affected, and the mechanical properties of the agricultural film will be weakened.

[0064] Example 1

[0065] A degradable composite agricultural film with biological protection function and a preparation method thereof, comprising the following steps:

[0066] S1. Preparation of PCL@TIO Film

[0067] 10 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The microwave power was 800 W, the ultrasonic frequency was 50 kHz, and the temperature was 160°C for 10 min to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 100 nm.

[0068] Titanium dioxide nanoparticles and PCL were fed into a screw extruder in a mass ratio of 8:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling in turn to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 12μm.

[0069] S2. Preparation of antibacterial and insect-proof layer

[0070] The coating agent is prepared by dissolving eucalyptus oil in water containing an emulsifier, wherein the mass fraction of eucalyptus oil in the coating agent is 5%, the mass fraction of Tween 80 is 10%, and the mass fraction of water is 85%.

[0071] The PCL@TIO film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min, and after drying, an antibacterial and insect-proof layer with a thickness of 2 μm was obtained.

[0072] S3. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0073] According to the molar ratio of 2-methylimidazole to zinc acetate being 8:1 and the molar ratio of zinc acetate to SiO2 being 8:5, 0.4 mol of 2-methylimidazole, 0.05 mol of zinc acetate and 0.03125 mol of SiO2 were weighed.

[0074] 0.05 mol of zinc acetate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0075] 0.4 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0076] The zinc salt solution, 2-methylimidazole solution and silica were evenly mixed and placed in an ultrasonic-microwave reactor, and reacted for 10 minutes at a microwave power of 800 W, an ultrasonic frequency of 50 kHz and a temperature of 140°C. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes, washed and dried to obtain a silica-assisted dispersed ZIF@SiO2 super-hydrophobic and highly active hybrid.

[0077] S4. Preparation of ultra-dispersible active agent:

[0078] 2 g of ZIF@SiO2 superhydrophobic active hybrid prepared in S3, 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer solution with a pH of 8.5 were mixed, stirred and reacted for 2 h in a water bath at 60°C, and centrifuged and dried to obtain polydopamine-modified ZIF@SiO2. The polydopamine-modified ZIF@SiO2 was dispersed in deionized water and ultrasonically dispersed at 50 kHz for 10 min to prepare an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0079] S5. Preparation of active insect repellent layer

[0080] Polylactic acid and boron nitride nanosheets are fed into a screw extruder at a mass ratio of 100:8, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 12μm, and the ultra-dispersed active agent solution prepared by S4 is coated with a coating thickness of 2μm to obtain an active insect repellent layer.

[0081] S6. Preparation of biodegradable composite agricultural film with biological protection function

[0082] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0083] Example 2

[0084] A degradable composite agricultural film with biological protection function and a preparation method thereof, comprising the following steps:

[0085] S1. Preparation of PCL@TIO Film

[0086] 10 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 20 min at a microwave power of 800 W, an ultrasonic frequency of 50 kHz and a temperature of 140°C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 200 nm.

[0087] Titanium dioxide nanoparticles and PCL were fed into a screw extruder at a mass ratio of 5:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 10μm.

[0088] S2. Preparation of antibacterial and insect-proof layer

[0089] The peppermint oil is dissolved in Tween 80 to prepare a coating agent, wherein the mass fraction of the peppermint oil in the coating agent is 5%, the mass fraction of Tween 80 is 10%, and the mass fraction of water is 85%.

[0090] The PCL@TIO film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min, and after drying, an antibacterial and insect-proof layer with a thickness of 1.5 μm was obtained.

[0091] S3. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0092] According to the molar ratio of 2-methylimidazole, zinc acetate and SiO2 being 64:8:2, 0.4 mol of 2-methylimidazole, 0.05 mol of zinc acetate and 0.0125 mol of SiO2 were weighed.

[0093] 0.05 mol of zinc acetate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0094] 0.4 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0095] The zinc salt solution, 2-methylimidazole solution and silica were evenly mixed in an ultrasonic microwave reactor and reacted for 20 min at a microwave power of 800 W, an ultrasonic frequency of 50 kHz and a temperature of 140°C. After centrifugation at 8000 rpm for 15 min, washing and drying, a silica-assisted dispersed ZIF@SiO2 super-hydrophobic active hybrid was obtained with a particle size of about 500 nm.

[0096] S4. Preparation of ultra-dispersible active agents

[0097] 3 g of ZIF@SiO2 superhydrophobic active hybrid prepared in S3 was mixed with 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer with a pH of 8.5 to prepare polydopamine-modified ZIF@SiO2. The polydopamine-modified ZIF@SiO2 was dispersed in deionized water and ultrasonically dispersed at 20 kHz for 40 min to prepare an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0098] S5. Preparation of active insect repellent layer

[0099] Polylactic acid and graphene nanosheets are fed into a screw extruder at a mass ratio of 100:5, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 10μm, and the ultra-dispersed active agent solution prepared by S4 is coated with a coating thickness of 1.5μm to obtain an active insect repellent layer.

[0100] S6. Preparation of biodegradable composite agricultural film with biological protection function

[0101] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0102] Example 3

[0103] A degradable composite agricultural film with biological protection function and a preparation method thereof, comprising the following steps:

[0104] S1. Preparation of PCL@TIO Film

[0105] 10 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 40 min at a microwave power of 600 W, an ultrasonic frequency of 50 kHz and a temperature of 100 ° C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 300 nm.

[0106] Titanium dioxide nanoparticles and PCL were fed into a screw extruder at a mass ratio of 3:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 15μm.

[0107] S2. Preparation of antibacterial and insect-proof layer

[0108] The thyme oil is dissolved in Tween 80 to prepare a coating agent, wherein the mass fraction of the thyme oil in the coating agent is 5%, the mass fraction of the Tween 80 is 10%, and the mass fraction of water is 85%.

[0109] The PCL@TIO film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min. After drying, an antibacterial and insect-proof layer with a thickness of 1 μm was obtained.

[0110] S3. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0111] According to the molar ratio of 2-methylimidazole, zinc nitrate and SiO2 being 64:8:1, 0.4 mol of 2-methylimidazole, 0.05 mol of zinc nitrate and 0.00625 mol of SiO2 were weighed.

[0112] 0.05 mol of zinc nitrate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0113] 0.4 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0114] The zinc salt solution, 2-methylimidazole solution and silica were mixed in an ultrasonic microwave reactor and reacted for 60 min at a microwave power of 600 W, an ultrasonic frequency of 50 kHz and a temperature of 100 ° C. After centrifugation at 7000 rpm for 20 min, washing and drying, a silica-assisted dispersed ZIF@SiO2 super-hydrophobic active hybrid was obtained with a particle size of about 700 nm.

[0115] S4. Preparation of ultra-dispersible active agents

[0116] 1.5 g of ZIF@SiO2 superhydrophobic active hybrid prepared in S3 was mixed with 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer with a pH of 8.5 to prepare polydopamine-modified ZIF@SiO2. The polydopamine-modified ZIF@SiO2 was dispersed in deionized water and ultrasonically dispersed at 30 kHz for 30 min to prepare an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0117] S5. Preparation of active insect-proof layer: polylactic acid and nano mica sheets are fed into a screw extruder at a mass ratio of 100:3, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 8μm, and the ultra-dispersed active agent solution prepared in S4 is coated with a coating thickness of 1μm to obtain an active insect-proof layer.

[0118] S6. Preparation of biodegradable composite agricultural film with biological protection function

[0119] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0120] Example 4

[0121] A degradable composite agricultural film with biological protection function and a preparation method thereof, comprising the following steps:

[0122] S1. Preparation of PCL@TIO Film

[0123] 10 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 5 min at a microwave power of 1000 W, an ultrasonic frequency of 50 kHz and a temperature of 180°C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 150 nm.

[0124] Titanium dioxide nanoparticles and PCL were fed into a screw extruder at a mass ratio of 1:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 8μm.

[0125] S2. Preparation of antibacterial and insect-proof layer

[0126] Peppermint oil was dissolved in Tween 80 to prepare a coating agent, and the PCL@TIO film prepared in S1 was coated with the coating agent by micro-gravure coating at a coating speed of 5 m / min. After drying, an antibacterial and insect-proof layer with a thickness of 0.5 μm was obtained.

[0127] S3. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0128] According to the molar ratio of 2-methylimidazole, zinc nitrate and SiO2 being 64:8:1, 0.4 mol of 2-methylimidazole, 0.05 mol of zinc nitrate and 0.00625 mol of SiO2 were weighed.

[0129] 0.05 mol of zinc nitrate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0130] 0.4 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0131] The zinc salt solution, 2-methylimidazole solution and silica were mixed evenly, placed in an ultrasonic microwave reactor, reacted for 40 min at a microwave power of 1000 W, an ultrasonic frequency of 50 kHz and a temperature of 120°C, centrifuged at 12000 rpm for 5 min, washed and dried to obtain a silica-assisted dispersed ZIF@SiO2 super-hydrophobic active hybrid with a particle size of about 1000 nm.

[0132] S4. Preparation of ultra-dispersible active agents

[0133] 1 g of ZIF@SiO2 superhydrophobic active hybrid prepared in S3, 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer at pH 8.5 were mixed to prepare polydopamine-modified ZIF@SiO2. The polydopamine-modified ZIF@SiO2 was dispersed in deionized water and ultrasonically dispersed at 40 kHz for 20 min to obtain an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0134] S5. Preparation of active insect repellent layer

[0135] Polylactic acid and natural montmorillonite are fed into a screw extruder at a mass ratio of 100:1, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 15μm, and the ultra-dispersed active agent solution prepared by S4 is coated with a coating thickness of 0.5μm to obtain an active insect-proof layer.

[0136] S6. Preparation of biodegradable composite agricultural film with biological protection function

[0137] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0138] Example 5

[0139] A degradable composite agricultural film with biological protection function and a preparation method thereof, comprising the following steps:

[0140] S1. Preparation of PCL@TIO Film

[0141] 15 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 3 min at a microwave power of 500 W, an ultrasonic frequency of 50 kHz and a temperature of 200 ° C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 300 nm.

[0142] Titanium dioxide nanoparticles and PCL were fed into a screw extruder at a mass ratio of 1:10, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling in turn to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 1.6μm.

[0143] S2. Preparation of antibacterial and insect-proof layer

[0144] The coating agent is prepared by dissolving black pepper seed oil in Tween 80, wherein the mass fraction of the black pepper seed oil in the coating agent is 5%, the mass fraction of Tween 80 is 10%, and the mass fraction of water is 85%.

[0145] The PCL@TIO film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min. After drying, an antibacterial and insect-proof layer was obtained with a thickness of 0.01 μm.

[0146] S3. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0147] According to the molar ratio of 2-methylimidazole, zinc nitrate and SiO2 being 1:1:1, 0.05 mol of 2-methylimidazole, 0.05 mol of zinc acetate and 0.05 mol of SiO2 were weighed.

[0148] 0.05 mol of zinc nitrate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0149] 0.05 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0150] The zinc salt solution, 2-methylimidazole solution and silica were mixed in an ultrasonic microwave reactor and reacted for 40 min at a microwave power of 1000 W, an ultrasonic frequency of 20 kHz and a temperature of 80°C. After centrifugation at 7000 rpm for 20 min, washing and drying, a silica-assisted dispersed ZIF@SiO2 super-hydrophobic active hybrid was obtained with a particle size of about 700 nm.

[0151] S4. Preparation of ultra-dispersible active agents

[0152] 5 g of ZIF@SiO2 superhydrophobic active hybrid prepared in S3 was mixed with 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer with a pH of 8.5 to prepare polydopamine-modified ZIF@SiO2. The polydopamine-modified ZIF@SiO2 was dispersed in deionized water and ultrasonically dispersed at 100 kHz for 3 min to prepare an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0153] S5. Preparation of active insect-proof layer: polylactic acid and nano mica sheets are fed into a screw extruder at a mass ratio of 10:1, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 8μm, and the ultra-dispersed surfactant solution prepared in S4 is coated with a coating thickness of 0.01μm to obtain an active insect-proof layer.

[0154] S6. Preparation of biodegradable composite agricultural film with biological protection function

[0155] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0156] Example 6

[0157] A degradable composite agricultural film with biological protection function and a preparation method thereof, comprising the following steps:

[0158] S1. Preparation of PCL@TIO Film

[0159] 20 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 30 min at a microwave power of 1000 W, an ultrasonic frequency of 100 kHz and a temperature of 80°C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 300 nm.

[0160] Titanium dioxide nanoparticles and PCL were fed into a screw extruder in a mass ratio of 3:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling in turn to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 37μm.

[0161] S2. Preparation of antibacterial and insect-proof layer

[0162] The coating agent is prepared by dissolving carnation oil in Tween 80, wherein the mass fraction of carnation oil in the coating agent is 5%, the mass fraction of Tween 80 is 10%, and the mass fraction of water is 85%.

[0163] The PCL@TIO film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min. After drying, an antibacterial and insect-proof layer was obtained with a thickness of 3 μm.

[0164] S3. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0165] According to the molar ratio of 2-methylimidazole, zinc nitrate and SiO2 being 80:8:10, 0.5 mol of 2-methylimidazole, 0.05 mol of zinc acetate and 0.0625 mol of SiO2 were weighed.

[0166] 0.05 mol of zinc nitrate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0167] 0.5 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0168] The zinc salt solution, 2-methylimidazole solution and silica were mixed in an ultrasonic microwave reactor and reacted for 5 min at a microwave power of 600 W, an ultrasonic frequency of 100 kHz and a temperature of 200 ° C. After centrifugation at 7000 rpm for 20 min, washing and drying, a silica-assisted dispersed ZIF@SiO2 super-hydrophobic active hybrid was obtained with a particle size of about 700 nm.

[0169] S4. Preparation of ultra-dispersible active agents

[0170] 1 g of ZIF@SiO2 superhydrophobic active hybrid prepared in S3 was mixed with 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer at pH 8.5 to prepare polydopamine-modified ZIF@SiO2. The polydopamine-modified ZIF@SiO2 was dispersed in deionized water and ultrasonically dispersed at 20 kHz for 60 min to obtain an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0171] S5. Preparation of active insect-proof layer: polylactic acid and nano mica sheets are fed into a screw extruder at a mass ratio of 100:1, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 5μm, and the ultra-dispersed surfactant solution prepared in S4 is coated with a coating thickness of 3μm to obtain an active insect-proof layer.

[0172] S6. Preparation of biodegradable composite agricultural film with biological protection function

[0173] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0174] Comparative Example 1

[0175] The degradable composite agricultural film was prepared by basically adopting the method of Example 1. The difference is that titanium dioxide nanoparticles were not added to the antibacterial and insect-proof layer in this comparative example. The specific preparation steps are as follows:

[0176] S1. PCL is fed into a screw extruder with a melt blending temperature of 200°C and a screw speed of 140 r / min. The blended melt extruded by the screw is successively water-cooled and air-cooled and solidified to form blended pellets. After the blended pellets are dried, they are fed into a film blowing machine with a temperature of 150°C, a screw speed of 110 r / min, and a traction speed of 6 m / min. The blended pellets are blown into film by the film blowing machine, and a PCL film is prepared by extrusion molding with a thickness of 12 μm.

[0177] S2. Dissolving eucalyptus oil in Tween 80 to prepare a coating agent, wherein the mass fraction of eucalyptus oil in the coating agent is 5%, the mass fraction of Tween 80 is 10%, and the mass fraction of water is 85%.

[0178] The PCL film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min, and after drying, an antibacterial and insect-proof layer with a thickness of 2 μm was obtained.

[0179] S3. According to the molar ratio of 2-methylimidazole to zinc acetate of 8:1 and the molar ratio of zinc acetate to SiO2 of 8:5, 0.4 mol of 2-methylimidazole, 0.05 mol of zinc acetate and 0.03125 mol of SiO2 were weighed.

[0180] 0.05 mol of zinc acetate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0181] Dissolve 0.4 mol of 2-methylimidazole in 500 mL of deionized water to obtain a 2-methylimidazole solution;

[0182] The zinc salt solution, 2-methylimidazole solution and silica were evenly mixed and placed in an ultrasonic-microwave reactor, and reacted for 10 minutes at a microwave power of 800 W, an ultrasonic frequency of 50 kHz and a temperature of 140°C. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes, washed and dried to obtain a silica-assisted dispersed ZIF@SiO2 super-hydrophobic and highly active hybrid.

[0183] S4. Mix 2 g of the ZIF@SiO2 superhydrophobic active hybrid prepared in S3, 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer solution with a pH of 8.5 to prepare polydopamine-modified ZIF@SiO2. Disperse the polydopamine-modified ZIF@SiO2 in deionized water and ultrasonically disperse it at 50 kHz for 10 min to obtain an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0184] S5. Polylactic acid and boron nitride nanosheets are fed into a screw extruder at a mass ratio of 100:8, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 12μm, and the ultra-dispersed active agent solution prepared in S4 is coated with a coating thickness of 2μm to obtain an active insect repellent layer.

[0185] S6. The antibacterial and insect-proof layer prepared in S2 is used as the inner layer, and the active insect-proof layer prepared in S5 is used as the outer layer, and in-situ lamination is performed at 100°C and 10 MPa to prepare a degradable composite agricultural film.

[0186] Comparative Example 2

[0187] The degradable composite agricultural film was prepared by basically adopting the method of Example 2. The difference is that plant essential oil was not coated on the PCL@TIO film in this comparative example. The specific preparation steps are as follows:

[0188] S1. Preparation of PCL@TIO Film

[0189] 10 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 20 min at a microwave power of 800 W, an ultrasonic frequency of 50 kHz and a temperature of 140°C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 200 nm.

[0190] Titanium dioxide nanoparticles and PCL were fed into a screw extruder at a mass ratio of 5:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 10μm.

[0191] S2. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0192] According to the molar ratio of 2-methylimidazole, zinc acetate and SiO2 being 64:8:2, 0.4 mol of 2-methylimidazole, 0.05 mol of zinc acetate and 0.0125 mol of SiO2 were weighed.

[0193] 0.05 mol of zinc acetate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0194] 0.4 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0195] The zinc salt solution, 2-methylimidazole solution and silica were evenly mixed in an ultrasonic microwave reactor and reacted for 20 min at a microwave power of 800 W, an ultrasonic frequency of 50 kHz and a temperature of 140°C. After centrifugation at 8000 rpm for 15 min, washing and drying, a silica-assisted dispersed ZIF@SiO2 super-hydrophobic active hybrid was obtained with a particle size of about 500 nm.

[0196] S3. Preparation of ultra-dispersible active agents

[0197] 3 g of ZIF@SiO2 superhydrophobic active hybrid prepared in S3 was mixed with 500 mL of 1 mg / mL dopamine hydrochloride solution and 0.5 g of Tris buffer with a pH of 8.5 to prepare polydopamine-modified ZIF@SiO2. The polydopamine-modified ZIF@SiO2 was dispersed in deionized water and ultrasonically dispersed at 20 kHz for 40 min to prepare an ultra-dispersed active agent solution with a concentration of 0.5 mg / mL.

[0198] S4. Preparation of active insect repellent layer

[0199] Polylactic acid and graphene nanosheets are fed into a screw extruder at a mass ratio of 100:5, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 10μm, and the ultra-dispersed active agent solution prepared by S4 is coated with a coating thickness of 1.5μm to obtain an active insect repellent layer.

[0200] S5. Preparation of biodegradable composite agricultural film with biological protection function

[0201] The PCL@TIO film prepared by S1 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer. In-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0202] Comparative Example 3

[0203] The degradable composite agricultural film was prepared by basically adopting the method of Example 3. The difference is that the ZIF@SiO2 super-hydrophobic active hybrid was not added to the active insect-proof layer in this comparative example. The specific preparation steps are as follows:

[0204] S1. Preparation of PCL@TIO Film

[0205] 10 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 40 min at a microwave power of 600 W, an ultrasonic frequency of 50 kHz and a temperature of 100 ° C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 300 nm.

[0206] Titanium dioxide nanoparticles and PCL were fed into a screw extruder at a mass ratio of 3:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 15μm.

[0207] S2. Preparation of antibacterial and insect-proof layer

[0208] The thyme oil is dissolved in Tween 80 to prepare a coating agent, wherein the mass fraction of the thyme oil in the coating agent is 5%, the mass fraction of the Tween 80 is 10%, and the mass fraction of water is 85%.

[0209] The PCL@TIO film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min. After drying, an antibacterial and insect-proof layer with a thickness of 1 μm was obtained.

[0210] S3. Preparation of active insect-proof layer: polylactic acid and nano-mica sheets are fed into a screw extruder at a mass ratio of 100:3, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 8μm to obtain an insect-proof layer.

[0211] S4. Preparation of biodegradable composite agricultural film with biological protection function

[0212] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S3 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0213] Comparative Example 4

[0214] The degradable composite agricultural film was prepared by basically adopting the method of Example 4. The difference is that polydopamine was not added to the active insect-proof layer in this comparative example. The specific preparation steps are as follows:

[0215] S1. Preparation of PCL@TIO Film

[0216] 10 mL of tetraisopropyl titanate, 50 mL of isopropanol and 10 mL of deionized water were mixed and placed in an ultrasonic microwave reactor. The mixture was reacted for 5 min at a microwave power of 1000 W, an ultrasonic frequency of 50 kHz and a temperature of 180°C to prepare titanium dioxide nanoparticles with a regular structure and a particle size of about 150 nm.

[0217] Titanium dioxide nanoparticles and PCL were fed into a screw extruder at a mass ratio of 1:100, the melt blending temperature was 200°C, the screw speed was 140r / min, and the blended melt extruded by the screw was solidified by water cooling and air cooling to form blended pellets; after the blended pellets were dried, they were fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed of 6m / min. The blended pellets were blown into film by the film blowing machine to prepare a PCL@TIO film with a thickness of 8μm.

[0218] S2. Preparation of antibacterial and insect-proof layer

[0219] The peppermint oil is dissolved in Tween 80 to prepare a coating agent, wherein the mass fraction of the peppermint oil in the coating agent is 5%, the mass fraction of Tween 80 is 10%, and the mass fraction of water is 85%.

[0220] The PCL@TIO film prepared in S1 was coated with a coating agent by micro-gravure coating at a coating speed of 5 m / min, and after drying, an antibacterial and insect-proof layer with a thickness of 0.5 μm was obtained.

[0221] S3. Preparation of ZIF@SiO2 superhydrophobic active hybrid

[0222] According to the molar ratio of 2-methylimidazole, zinc nitrate and SiO2 being 64:8:1, 0.4 mol of 2-methylimidazole, 0.05 mol of zinc acetate and 0.00625 mol of SiO2 were weighed.

[0223] 0.05 mol of zinc nitrate was dissolved in 500 mL of deionized water to obtain a zinc salt solution.

[0224] 0.4 mol of 2-methylimidazole was dissolved in 500 mL of deionized water to obtain a 2-methylimidazole solution.

[0225] The zinc salt solution, 2-methylimidazole solution and silica were mixed evenly, placed in an ultrasonic microwave reactor, reacted for 40 min at a microwave power of 1000 W, an ultrasonic frequency of 50 kHz and a temperature of 120°C, centrifuged at 12000 rpm for 5 min, washed and dried to obtain a silica-assisted dispersed ZIF@SiO2 super-hydrophobic active hybrid with a particle size of about 1000 nm.

[0226] S4. Preparation of active insect repellent layer

[0227] Polylactic acid and natural montmorillonite are fed into a screw extruder in a mass ratio of 100:1, the melt blending temperature is 200°C, the screw speed is 140r / min, and the blended melt extruded by the screw is solidified by water cooling and air cooling in sequence to form blended pellets; after the blended pellets are dried, they are fed into a film blowing machine at a temperature of 150°C, a screw speed of 110r / min, and a traction speed set to 6m / min. The blended pellets are blown into film by the film blowing machine to prepare a high barrier PLA film with a thickness of 15μm, and the ZIF@SiO2 superhydrophobic active hybrid prepared by S3 is coated with a coating thickness of 0.5μm to obtain an active insect-proof layer.

[0228] S6. Preparation of biodegradable composite agricultural film with biological protection function

[0229] The antibacterial and insect-proof layer prepared by S2 was used as the inner layer, and the active insect-proof layer prepared by S5 was used as the outer layer, and in-situ lamination was performed at 100°C and 10 MPa to prepare a degradable composite agricultural film with biological protection function.

[0230] The performance of the degradable composite agricultural films prepared in the examples and comparative examples was tested below.

[0231] Water contact angle test: The water contact angle of the warming and humidifying layer of the agricultural film was tested using a contact angle meter (model DSA100, manufacturer: KRUSS, Germany).

[0232] Water retention and warming performance test: An integrated temperature and humidity sensor (model DS1923-F5, manufactured by Shanghai Wodisen Electronic Technology Co., Ltd.) was placed on the soil covered with agricultural film to record the changes in humidity and temperature inside the film.

[0233] Antibacterial performance test: The plate culture method was used to observe the antibacterial effect of agricultural film on Escherichia coli, and the plate colony counting method was used to calculate the antibacterial efficiency of agricultural film. Escherichia coli was purchased from Ningbo Mingzhou Biotechnology Co., Ltd., and the product number of Escherichia coli is BMZ109324.

[0234] Insect repellent performance test: Cut the agricultural film evenly into plastic bags of 10 cm × 10 cm. Add 10 adults of Plutella xylostella and 10 adults of Coccinella chinensis into the agricultural film bags, and then add 10 grams of wheat and 10 grams of mung beans as food for the adults. Observe once every 24 hours. All experiments were repeated three times, and the insect mortality rate was calculated at 96 hours.

[0235] Tensile property test: The obtained agricultural film was cut to obtain tensile specimens, and the tensile properties of the agricultural film were tested using a universal tensile machine (model 4403, sensor 100N) of Instron Company of the United States according to the plastic tensile property test standard ASTMD638-2003 of the American Society for Testing and Materials. At least 3 parallel test samples were guaranteed for each group, and the results were averaged.

[0236] Degradation performance test: The traditional soil burial degradation method was used to conduct a degradation experiment on the agricultural film. The agricultural film was weighed before the experiment and weighed again after being buried in the soil for 3 months. The mass loss rate was calculated to evaluate the degradation performance.

[0237] Table 1 Test results of antibacterial and insect repellent, warming and humidifying, mechanical properties and degradation performance of degradable composite agricultural films Table 1 compares the test results of antibacterial and insect-proof, warming and humidifying, mechanical properties and degradation performance of the multilayer biodegradable agricultural film obtained in the examples and comparative examples. Examples 1 to 4 and comparative examples 2 to 4 all have high antibacterial efficiency (78%-100%), because titanium dioxide can induce light to produce highly oxidizing active oxygen groups, which can directly or indirectly bind to bacterial cells and inhibit or kill environmental bacteria. The antibacterial efficiency of comparative example 1 is relatively low, mainly due to the lack of titanium dioxide loading, and the ability to inhibit bacterial growth is relatively weak.

[0238] Examples 1 to 4 and Comparative Examples 1 and 4 have a high insect repellent efficiency of 75% to 100%. This is due to the combined effect of ZIF and plant essential oils. ZIF can produce a large number of active free radicals under light conditions, which have a killing effect on harmful insects, and the coated plant essential oils can show multiple modes of action such as contact killing, fumigation, repelling, killing eggs, and inhibiting growth and development on insects and mites, thereby achieving a significant insect repellent effect. The insect repellent efficiency of Comparative Example 2 is only 40%, because the lack of biological protective coating can not kill harmful insects. The insect repellent efficiency of Comparative Example 3 is also relatively low, only 55%, because the lack of a large number of active free radicals generated by ZIF reduces the damage of agricultural film to insects.

[0239] Except for Comparative Example 3, all of them have a large water contact angle of 127.6° to 152.5°. This is because the SiO2@ZIF-8 superhydrophobic hybrid particles greatly improve the hydrophobicity of the agricultural film, thereby effectively blocking water evaporation and ensuring that the crops are in a high humidity environment of 83%RH-93%RH. Comparative Example 3 lacks the loading of SiO2@ZIF-8, PLA is hydrophilic due to the influence of polydopamine, and the water in the soil is easy to evaporate, and a high humidity environment cannot be guaranteed.

[0240] The ambient temperature of Examples 1 to 4 and Comparative Examples 1 to 3 was significantly increased by 7.1°C to 12.8°C, because polydopamine has a wide range of light absorption and excellent light-to-heat conversion capabilities, thus providing good warming performance for the agricultural film. In Comparative Example 4, due to the lack of polydopamine addition, the light absorption capacity of the agricultural film was weakened, so the temperature increase was not obvious, only 4.3°C.

[0241] The embodiments and comparative examples all have a high breaking strength of 28.3MPa to 34.7MPa, reflecting excellent mechanical properties. The degradable composite agricultural film fully meets the mechanical property requirements for application in farmland. The agricultural film was subjected to degradation experiments using the traditional soil burial degradation method. After 3 months of soil burial, the mass loss of all the embodiments and comparative examples was above 10.7%, indicating that the degradable composite agricultural film with biological protection function also has good biodegradability, protecting the agricultural ecological environment.

[0242] If the agricultural film does not adopt a composite structure of an antibacterial and insect-proof layer and an active insect-proof layer, and directly extrude polycaprolactone, polylactic acid, titanium dioxide, layered filler, polydopamine-modified ZIF@SiO2 hybrid and plant essential oil to prepare a single-layer agricultural film, the inhibitory effect of titanium dioxide on the growth of bacteria inside the agricultural film cannot be fully exerted, the plant essential oil will be affected by the external environment and cause problems such as too fast release or even loss of effectiveness, and the high barrier, support and waterproof properties of the agricultural film cannot be guaranteed.

[0243] The degradable composite agricultural film prepared by the present invention not only has the advantages of antibacterial, insect-proof, temperature-increasing and humidifying, and plays a role in increasing the yield and quality of crops, but also has good degradability, reducing the pollution of the agricultural film to the soil, which is likely to benefit from the following aspects:

[0244] (1) Titanium dioxide nanoparticles can be photoinduced to produce highly oxidizing reactive oxygen groups, which can bind to bacterial cells directly or indirectly and have an inhibitory or killing effect on environmental bacteria.

[0245] (2) ZIF can produce a large number of active free radicals under light conditions, which have a killing effect on harmful insects. The coated plant essential oil can show a variety of actions on insects and mites, such as contact killing, fumigation, repelling, killing eggs, and inhibiting growth and development, thereby achieving a significant insect pest control effect.

[0246] (3) The super-hydrophobic active hybrid ZIF@SiO2 obtained by the ultrasonic microwave-assisted method uses silica to assist in dispersing ZIF crystals, which reduces agglomeration and can better exert its active insect repellent effect. Silica gives the agricultural film super-hydrophobic properties, allowing the agricultural film to effectively block the evaporation of water in the soil and provide a high-humidity environment for crops.

[0247] (4) Polydopamine can act as an adhesive to prevent the hybrid from falling off, and can act as a dispersant to prevent the hybrid from agglomerating, so that the ZIF@SiO2 superhydrophobic active hybrid can effectively play its function. In addition, it has excellent infrared absorption and photothermal conversion capabilities, which can significantly improve the warming performance of agricultural film.

[0248] (5) The antibacterial and insect-proof layer serves as the inner layer, which fully utilizes the light-induced antibacterial properties of titanium dioxide to effectively inhibit the growth of bacteria in the agricultural film, and the plant essential oil coating provides an insect-proof effect inside the agricultural film; the active insect-proof layer serves as the outer layer, and the active free radicals generated by ZIF can be used to repel and kill insects outside the agricultural film. The inner and outer layers of the agricultural film work synergistically to achieve a dual biological protection effect.

[0249] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0250] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a bioprotective and fully degradable moisture-retaining agricultural film, characterized in that: The following steps are involved: Titanium dioxide and polycaprolactone are blended and extruded to prepare a PCL@TIO film; plant essential oil is coated on the PCL@TIO film to prepare an antibacterial and insect-proof layer; After the silicon dioxide, zinc salt solution and imidazole ligand are uniformly mixed, an ultrasonic microwave reaction is performed. During the reaction, the zinc salt solution and the imidazole ligand react to prepare a zeolite imidazole ester framework structure material, and the silicon dioxide is coated on the surface of the zeolite imidazole ester framework structure material to prepare a ZIF@SiO2 hybrid. The ZIF@SiO2 hybrid and dopamine are stirred and mixed, and during the stirring process, dopamine self-polymerizes to form polydopamine, and the polydopamine adheres to the surface of the ZIF@SiO2 hybrid to obtain an active agent; The polylactic acid and the layered filler are co-extruded to prepare a PLA film, and the active agent is coated on the PLA film to prepare an active insect-proof layer; The antibacterial and insect-proof layer and the active insect-proof layer are in situ composited to obtain a biological protection and fully degradable moisture-retaining agricultural film.

2. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 1, characterized in that: The mass ratio of titanium dioxide to polycaprolactone is 1 to 10:

100.

3. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 1, characterized in that: The mass ratio of ZIF@SiO2 hybrid to dopamine is 1-10:1, the ultrasonic frequency is 20kHz-100kHz, and the ultrasonic time is 3min-60min.

4. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 1, characterized in that: The mass ratio of polylactic acid to the layered filler is 100:1-10, and the coating thickness of the active agent is 0.01 μm-3 μm.

5. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 1, characterized in that: The thickness ratio of the antibacterial and insect-proof layer to the active insect-proof layer is 0.2 to 5:

1.

6. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 1, characterized in that: The molar ratio of the imidazole ligand to the zinc salt is 1 to 10:1, and the molar ratio of the zinc salt to SiO2 is 8:1 to 10; When preparing the ZIF@SiO2 hybrid, the output power of the ultrasonic microwave reaction is 500W to 1000W, the ultrasonic frequency is 20kHz to 100kHz, the reaction temperature is 80°C to 200°C, and the reaction time is 5min to 40min.

7. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 1, characterized in that: The plant essential oil is at least one of eucalyptus oil, peppermint oil, thyme oil, turpentine oil, carnation oil and black pepper oil, and the coating thickness is 0.01 μm to 3 μm.

8. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 1, characterized in that: After a titanium source, an alcohol solvent and water are mixed, an ultrasonic microwave reaction is carried out to obtain titanium dioxide.

9. The method for preparing a bioprotective and fully degradable moisture-retaining agricultural film according to claim 8, characterized in that: The volume ratio of titanium source, alcohol solvent and water is 1 to 2:5:1; When preparing titanium dioxide, the microwave output power of the ultrasonic microwave reaction is 500W to 1000W, the ultrasonic frequency is 20kHz to 100kHz, the reaction temperature is 80°C to 200°C, and the reaction time is 3min to 40min.

10. A biological protection and fully degradable moisture-retaining agricultural film prepared by the preparation method according to any one of claims 1 to 9.

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