Preparation method of slow-release fully biodegradable weed-killing film

Abstract

The present invention belongs to the technical field of agricultural materials, and specifically relates to a method for preparing a slow-release fully biodegradable weed-killing film. A COFs-carbon nanotube-herbicide pesticide complex and a fully biodegradable resin are melt-blended and extruded and blow-molded to obtain a slow-release fully biodegradable weed-killing film; wherein the COFs-carbon nanotube-herbicide pesticide complex is prepared by loading the herbicide on the COFs-carbon nanotube. The film prepared by the present invention has both an extremely long weed-killing functional period and excellent anti-ultraviolet aging properties, and has good mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural materials, and in particular relates to a method for preparing a slow-release fully biodegradable weed-killing film. Background Art

[0002] Ground film is an important agricultural production material with a wide range of applications and significant yield-increasing effects. Traditional ground films are mostly made of polyethylene, and the residual film after use is difficult to degrade, which can easily lead to the problem of "white pollution" in the soil. Biodegradable ground films can be degraded into carbon dioxide, water and inorganic substances in the natural environment after use, and will not cause harm to the soil environment. This is the future development trend.

[0003] At present, the fully biodegradable mulch is easily affected by weeds under the film during use, and it is necessary to spray herbicides for weed control many times, which is time-consuming and labor-intensive. Once the weeds break through, it will quickly crack and degrade rapidly, losing its original heat preservation and moisture retention functions, which has become a bottleneck problem for the further promotion and application of this type of mulch. At present, there are two main types of fully biodegradable weed control mulch: one is a weed control mulch with sunscreen added, the most common of which is black weed control mulch; the other is to add chemical herbicides to the mulch to achieve the weed control effect. This type of weed control mulch has been used on crops such as peanuts, corn, aloe vera, and sugarcane, and has a significant weed control effect.

[0004] Patents related to fully degradable mulch films with added chemical herbicides include Chinese patents CN102276966A, CN207744480U, CN110684327A, CN211909873U, CN103497412A, CN106496968A, CN106496969A, etc., which have the following common disadvantages: the herbicide components in the weed-killing mulch films will be completely released in a short time, thereby losing their weed-killing function, and the weed-killing function period is short (<1 month), which cannot meet the long-term requirements of the entire crop growth period (3-4 months). Chinese patents CN109122679A, CN110583639A, CN106879587A, etc. load herbicides into nanoparticles, and add the nanoparticles into ground film to prepare a ground film with weed control function; however, due to the poor compatibility of such nanoparticles with the ground film matrix, such nanoparticles are difficult to be evenly dispersed in the ground film matrix, and are very prone to agglomeration, resulting in a significant reduction in the mechanical properties of the ground film, and the ground film is prone to rupture, which not only affects the normal use of the ground film, but also easily breeds weeds again. Therefore, it is of great significance to develop a ground film with a longer weed control function period and excellent mechanical properties to meet the weed control function of crops throughout the entire growth period. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a slow-release fully biodegradable weed control film. The prepared film has an extremely long weed control functional period and excellent anti-ultraviolet aging properties, and has good mechanical properties.

[0006] The preparation method of the slow-release fully biodegradable weed-killing mulch film described in the present invention is to melt-blend a COFs-carbon nanotube-herbicide pesticide complex and a fully biodegradable resin, and extrude and blow mold to obtain a slow-release fully biodegradable weed-killing mulch film; wherein the COFs-carbon nanotube-herbicide pesticide complex is prepared by loading the herbicide on the COFs-carbon nanotube.

[0007] The herbicide is one or more of oxyfluorfen, acifluorfen, lactofen, fomesafen, fluazifop-butyl, bromoxynil, bromoxynil octanoyl or iodoxynil octanoyl, preferably oxyfluorfen.

[0008] The COFs-carbon nanotube preparation method comprises the following steps: reacting 2,6,14-triaminotriptycene, 1,4,5,8-naphthalenetetracarboxylic anhydride, carbon nanotubes, N,N-dimethylformamide and propionic acid, cooling to room temperature after the reaction, and filtering to obtain a solid product; washing, freezing and freeze-drying the solid product to obtain the COFs-carbon nanotube.

[0009] The ratio of 2,6,14-triaminotriptycene, 1,4,5,8-naphthalenetetracarboxylic anhydride, carbon nanotubes, N,N-dimethylformamide and propionic acid is 0.1-0.3:0.1-0.3:0.002-0.18:10-15:5-8, wherein 2,6,14-triaminotriptycene is measured in g, 1,4,5,8-naphthalenetetracarboxylic anhydride is measured in g, carbon nanotubes are measured in g, N,N-dimethylformamide is measured in mL, and propionic acid is measured in mL.

[0010] The reaction temperature is 120-220°C, and the reaction time is 12-36h.

[0011] The freezing temperature is -10--50°C, and the freezing time is 6-18h.

[0012] The freeze-drying temperature is -10 to -50°C, and the freeze-drying time is 12 to 36 hours.

[0013] The preparation method of the COFs-carbon nanotube-herbicide pesticide complex is as follows: dissolving a herbicide in deionized water to prepare a herbicide solution, stirring the COFs-carbon nanotubes and the herbicide solution to obtain a mixed suspension; filtering the mixed suspension, washing to obtain a filter cake, and drying the filter cake to obtain the COFs-carbon nanotube-herbicide pesticide complex.

[0014] The concentration of the herbicide solution is 0.01-0.2 g / mL.

[0015] The mass ratio of the COFs-carbon nanotubes to the herbicide solution is 5-50:3.

[0016] The stirring time is 3-8h.

[0017] The rinsing is performed with deionized water, and the number of rinsing times is 2-5 times.

[0018] The drying temperature is 30-80°C.

[0019] The fully biodegradable resin is one or more of PHA, BSR, PPCP or PGA, preferably PPCP.

[0020] The particle size of the fully biodegradable resin is 2-4 mm.

[0021] The particle size of the COFs-carbon nanotube-herbicide complex is 10-1000 nm, preferably 100-200 nm.

[0022] The mass ratio of the COFs-carbon nanotube-herbicide complex to the fully biodegradable resin is 0.5-5:95-99.5.

[0023] The method for preparing COFs-carbon nanotubes comprises the following steps:

[0024] 2,6,14-triaminotriptycene and 1,4,5,8-naphthalenetetracarboxylic anhydride are added to a reaction tube, and then carbon nanotubes are added to the reaction tube, and then N,N-dimethylformamide and propionic acid are added thereto, ultrasonicated for 0.1-1h, the reaction tube is sealed and then freeze-dried three times to exhaust the gas in the tube, and then the reaction tube is placed in an oil bath pot, and magnetically stirred at 120-220°C for 12-36h. After the reaction is completed, the reaction tube is taken out and cooled to room temperature, and the filtered solid product is collected by suction, and washed three times with N,N-dimethylformamide, methanol and deionized water respectively. The obtained solid product is placed in a refrigerator at -10--50°C for 6-18h, and then freeze-dried in a freeze dryer at -10--50°C for 12-36h to obtain carbon nanotubes loaded with COFs, which are recorded as COFs-carbon nanotubes.

[0025] The method for preparing the COFs-carbon nanotube-herbicidal pesticide complex comprises the following steps:

[0026] The COFs-carbon nanotubes were vacuum dried for 5-10 hours, and an appropriate amount of dried COFs-carbon nanotubes were accurately placed in a 100mL vacuum reaction tube, and the reverse rubber stopper was plugged. The air in the COFs and nanotube cavities was evacuated as much as possible to form a negative pressure. The herbicide was accurately weighed and dissolved in deionized water to prepare a herbicide solution. The herbicide solution was injected into the vacuum reaction tube through the rubber stopper with a syringe and magnetically stirred for 3-8 hours. The mixed suspension was filtered with a sand core funnel, rinsed with deionized water 2-5 times, and the free herbicides outside were washed away. The obtained COFs-carbon nanotube-herbicidal pesticide complex filter cake was dried in a vacuum drying oven at 30-80°C until constant weight. The dried COFs-carbon nanotube-herbicidal pesticide complex was crushed with a mortar to obtain a COFs-carbon nanotube-herbicidal pesticide complex powder.

[0027] The method for preparing the slow-release fully biodegradable weed-killing film of the present invention comprises the following steps:

[0028] (1) The COFs-carbon nanotube-herbicide pesticide complex and the fully biodegradable resin are dried at 60-100°C for 8-15h, and are added to a high-speed mixer for 3-10min for premixing, so that the COFs-carbon nanotube-herbicide pesticide complex and the fully biodegradable resin are uniformly mixed. The mixture is added to the feed port of a twin-screw extruder, the feed rate is 50-200g / min, the temperature of the seven zones from the feed port to the extruder head is set to: 175 / 175 / 170 / 165 / 165 / 160 / 155°C, the screw speed is 100-300rpm, and the resin is melt-blended, water-cooled, air-dried, and then granulated in a pelletizer to obtain a composite masterbatch.

[0029] (2) Dry the obtained composite masterbatch at 60-100°C for 8-15h, add it into a single screw extruder for melt extrusion, and blow it into a slow-release fully biodegradable weed-killing mulch film through a film blowing machine; wherein the temperature of the single screw extruder head and the heating zone are set to: 175 / 170 / 160 / 155°C, and the screw speed is 20-50rpm. The obtained slow-release fully biodegradable weed-killing mulch film is packaged in a black opaque plastic bag and stored in a dry, cool and dark place.

[0030] The thickness of the slow-release fully biodegradable weed-killing film is controlled between 4 and 21 μm.

[0031] Covalent organic framework materials (COFs) are an emerging type of "porous" polymer materials composed of organic molecules connected by covalent bonds. They have the following advantages: (1) Due to their "porous" characteristics, this type of material has extremely strong adsorption properties; (2) This type of material has an ultraviolet-visible light absorption band (250-800nm), which can effectively absorb ultraviolet rays and is an excellent ultraviolet-visible shielding material; (3) According to the principle of like dissolves like, they have good compatibility with the polymer matrix of fully biodegradable mulch. After adding them to the mulch, they have no significant effect on the mechanical properties of the mulch.

[0032] Carbon nanotubes are a tubular one-dimensional quantum nanomaterial, and the hollow tubular structure gives it a very strong adsorption function. Therefore, in the present invention, COFs materials are loaded onto carbon nanotubes, and then herbicidal pesticide molecules are adsorbed to obtain COFs-carbon nanotube-herbicidal pesticide complexes. This type of complex has the function of dual slow-release herbicidal pesticides. After the complex is added to the degradable mulch film matrix, the mulch film is given a long slow-release herbicidal function and excellent anti-ultraviolet aging properties, and the mechanical properties of the mulch film will not be significantly reduced.

[0033] The COFs-carbon nanotube-herbicide complex has a dual slow-release effect on the herbicide. The weed-killing film covers the soil, and the water vapor in the soil condenses into water droplets on the surface of the film. The herbicide molecules will be slowly released into the water droplets; and the COFs on the surface of the complex are organic polymer materials. According to the principle of similar compatibility, they have good compatibility with the polymer matrix.

[0034] Both COFs and carbon nanotubes have a sustained release effect on pesticides. The interior of the carbon nanotube cavity has a sustained release effect on pesticides, and COFs are loaded on the surface of the carbon nanotube, that is, the outside of the cavity, so that the outside of the carbon nanotube also has a sustained release effect, so that it has a sustained release effect from the inside to the outside.

[0035] The pesticide molecules released from the internal cavity of the carbon nanotubes can be adsorbed again by the COFs outside, and the pesticide molecules released from the COFs outside can also be adsorbed again by the internal carbon nanotube cavity. In this way, there is a dynamic adsorption-release balance inside and outside, so COFs and carbon nanotubes have a synergistic slow-release effect.

[0036] The beneficial effects of the present invention are as follows:

[0037] The present invention is to load COFs material onto carbon nanotubes to obtain COFs-carbon nanotubes, and then load herbicides onto COFs-carbon nanotubes to obtain COFs-carbon nanotubes-herbicidal pesticide complexes, which have the function of dual sustained-release herbicidal pesticides; the complexes and fully biodegradable resins are melt blended and extruded by blow molding to prepare dual sustained-release fully biodegradable mulch films with extremely long herbicidal functional periods and excellent anti-ultraviolet visible light aging properties, and the mechanical properties of such mulch films will not be significantly reduced. During use, the herbicidal pesticide molecules loaded inside the COFs-carbon nanotubes-herbicidal pesticide complexes will be slowly released into the mulch matrix, and then further released onto the mulch surface, and finally contacted with weed leaves to achieve the weeding effect. The slow-release fully biodegradable weed-killing film prepared by the present invention has a weed-killing function period of 115-150 days. Compared with the traditional weed-killing film without slow-release function, the slow-release fully biodegradable weed-killing film of the present invention has a longer weed-killing function period and can meet the requirements of weeding during the entire growth period of crops. The fully biodegradable resin used as a mulch material has the characteristics of full biodegradability in the soil, green and environmental protection, and will not cause environmental pollution. The present invention has important economic, social and ecological benefits for the further development and application of the fully biodegradable mulch film, and meets the requirements of sustainable agricultural development. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a graph showing the cumulative release rate of herbicide components of weed film in water.

[0039] Figure 2 These are photos of the weed control effects of five types of mulch covering ryegrass at different times.

[0040] Figure 3 This is a graph showing the tensile strength and nominal strain at break of three types of mulch films.

[0041] Figure 4 This is a graph showing the loss rate of mechanical properties (nominal strain at break and tensile strength) of three types of mulch films after exposure to a high-temperature UV aging box at 60°C for 9 days.

[0042] Figure 5 This is the UV-visible absorption spectrum of COFs material. DETAILED DESCRIPTION

[0043] The present invention is further described below with reference to the embodiments.

[0044] Unless otherwise specified, all raw materials in the following examples were purchased from the market.

[0045] Example 1

[0046] The preparation method of COFs-carbon nanotubes comprises the following steps:

[0047] 0.2 g of 2,6,14-triaminotriptycene and 0.26 g of 1,4,5,8-naphthalenetetracarboxylic anhydride were added to a reaction tube, and then 0.046 g of carbon nanotubes were added to the reaction tube, followed by the addition of 12.0 mL of N,N-dimethylformamide and 7.0 mL of propionic acid, ultrasonication for 0.5 h, the reaction tube was sealed and then freeze-dried three times to exhaust the gas in the tube, and then the reaction tube was placed in an oil bath pot and reacted with magnetic stirring at 170° C. for 24 h. After the reaction was completed, the reaction tube was taken out and cooled to room temperature, the filtered solid product was collected by suction, and washed three times with N,N-dimethylformamide, methanol and deionized water respectively, and the obtained solid product was placed in a refrigerator and frozen at -30° C. for 12 h, and then freeze-dried in a freeze dryer at -30° C. for 24 h to obtain carbon nanotubes loaded with COFs, which were recorded as COFs-carbon nanotubes.

[0048] The preparation method of COFs-carbon nanotube-herbicide complex comprises the following steps:

[0049] The COFs-carbon nanotubes were vacuum dried for 8 hours, and 180g of the dried COFs-carbon nanotubes were accurately placed in a 100mL vacuum reaction tube, and the reverse rubber stopper was plugged. The vacuum was evacuated with a circulating water vacuum pump for 20 minutes to exhaust the air in the COFs and nanotube cavities as much as possible to form a negative pressure. 1g of the herbicide oxyfluorfen was weighed and dissolved in a ground-mouth conical flask containing 100mL of pure water to prepare a herbicide solution. The herbicide solution was injected into the vacuum reaction tube through the rubber stopper with a syringe and magnetically stirred for 5 hours. The mixed suspension was filtered with a sand core funnel, rinsed with deionized water 3 times to rinse off the free herbicide outside, and the obtained COFs-carbon nanotube-herbicide pesticide complex filter cake was dried in a vacuum drying oven at 50°C until constant weight. The dried COFs-carbon nanotubes-herbicide complex was ground in a mortar to obtain COFs-carbon nanotubes-herbicide complex powder with a particle size distribution of 100 nm.

[0050] The preparation method of the slow-release fully biodegradable weed-killing film comprises the following steps:

[0051] First, the COFs-carbon nanotube-herbicide complex and the fully biodegradable resin PHA particles (particle size 2-4mm) were dried at 80°C for 12h, and added to a high-speed mixer at a mass ratio of 1:99 for 5min for pre-mixing to make the complex and the resin evenly mixed. The mixture was added to the feed port of the twin-screw extruder at a feed rate of 150g / min. The temperature of the seven zones from the feed port to the extruder head was set to: 175 / 175 / 170 / 165 / 165 / 160 / 155°C, and the screw speed was 200rpm. After the resin was melted and blended, it was water-cooled and air-dried before entering the pelletizer for granulation to obtain a composite masterbatch.

[0052] The obtained composite masterbatch was then dried at 80°C for 12 hours, added to a single screw extruder for melt extrusion, and blown into a slow-release fully biodegradable weed control film by a film blowing machine. The temperature of the single screw extruder head and the heating zone was set to: 175 / 170 / 160 / 155°C, and the screw speed was 40rpm. The obtained slow-release fully biodegradable weed control film was packaged in a black opaque plastic bag and stored in a dry, cool and dark place. The thickness of the slow-release fully biodegradable weed control film was controlled at 5±1μm.

[0053] Example 2

[0054] The preparation method of COFs-carbon nanotubes comprises the following steps:

[0055] 0.1 g of 2,6,14-triaminotriptycene and 0.18 g of 1,4,5,8-naphthalenetetracarboxylic anhydride were added to a reaction tube, and then 0.056 g of carbon nanotubes were added to the reaction tube, followed by addition of 10.0 mL of N,N-dimethylformamide and 5.0 mL of propionic acid, ultrasonication for 0.1 h, sealing the reaction tube and then freeze-desorbing it three times to exhaust the gas in the tube, then placing the reaction tube in an oil bath, stirring it with magnetic stirring at 120° C. for 36 h, after the reaction was completed, taking out the reaction tube and cooling it to room temperature, collecting the filtered solid product by suction, and washing it three times with N,N-dimethylformamide, methanol and deionized water respectively, the obtained solid product was placed in a refrigerator and frozen at -10° C. for 18 h, and then freeze-dried in a freeze dryer at -10° C. for 36 h to obtain carbon nanotubes loaded with COFs, recorded as COFs-carbon nanotubes.

[0056] The preparation method of COFs-carbon nanotube-herbicide complex comprises the following steps:

[0057] The COFs-carbon nanotubes were vacuum dried for 5 hours, and 210g of the dried COFs-carbon nanotubes were accurately placed in a 100mL vacuum reaction tube, and the reverse rubber stopper was plugged. The vacuum was evacuated with a circulating water vacuum pump for 50 minutes to exhaust the air in the COFs and nanotube cavities as much as possible to form a negative pressure. 3g of the herbicide trifluorfen was weighed and dissolved in a ground-mouth conical flask containing 100mL of pure water to prepare a herbicide solution. The herbicide solution was injected into the vacuum reaction tube through the rubber stopper with a syringe and magnetically stirred for 3 hours. The mixed suspension was filtered with a sand core funnel, rinsed with deionized water twice to rinse off the free herbicide outside, and the obtained COFs-carbon nanotube-herbicide pesticide complex filter cake was dried in a vacuum drying oven at 30°C until constant weight. The dried COFs-carbon nanotubes-herbicide complex was ground in a mortar to obtain COFs-carbon nanotubes-herbicide complex powder with a particle size distribution of 500 nm.

[0058] The preparation method of the slow-release fully biodegradable weed-killing film comprises the following steps:

[0059] First, the COFs-carbon nanotube-herbicide complex and the fully biodegradable resin BSR particles (particle size 2-4mm) were dried at 60°C for 15h, and added to a high-speed mixer at a mass ratio of 3:97 for 3min for pre-mixing to make the complex and the resin evenly mixed. The mixture was added to the feed port of the twin-screw extruder at a feed rate of 200g / min. The temperature of the seven zones from the feed port to the extruder head was set to: 175 / 175 / 170 / 165 / 165 / 160 / 155°C, the screw speed was 100rpm, and the resin was melt-blended, water-cooled, air-dried, and then entered the pelletizer for granulation to obtain a composite masterbatch.

[0060] The obtained composite masterbatch was then dried at 60°C for 15h, added to a single screw extruder for melt extrusion, and blown into a slow-release fully biodegradable weed control film by a film blowing machine. The temperature of the single screw extruder head and the heating zone was set to: 175 / 170 / 160 / 155°C, and the screw speed was 20rpm. The obtained slow-release fully biodegradable weed control film was packaged in a black opaque plastic bag and stored in a dry, cool and dark place. The thickness of the biodegradable weed control film was controlled at 10±1μm.

[0061] Example 3

[0062] The preparation method of COFs-carbon nanotubes comprises the following steps:

[0063] 0.22 g of 2,6,14-triaminotriptycene and 0.3 g of 1,4,5,8-naphthalenetetracarboxylic anhydride were added to a reaction tube, and then 0.156 g of carbon nanotubes were added to the reaction tube, followed by addition of 15.0 mL of N,N-dimethylformamide and 8.0 mL of propionic acid, ultrasonication for 1 h, sealing the reaction tube and then freeze-desorbing three times to exhaust the gas in the tube, then placing the reaction tube in an oil bath, stirring magnetically at 220° C. for 12 h, after the reaction was completed, taking out the reaction tube and cooling it to room temperature, collecting the filtered solid product by suction, and washing it three times with N,N-dimethylformamide, methanol and deionized water respectively, the obtained solid product was placed in a refrigerator and frozen at -50° C. for 6 h, and then freeze-dried in a freeze dryer at -50° C. for 12 h to obtain carbon nanotubes loaded with COFs, recorded as COFs-carbon nanotubes.

[0064] The preparation method of COFs-carbon nanotube-herbicide complex comprises the following steps:

[0065] The COFs-carbon nanotubes were vacuum dried for 10 hours, and 250g of the dried COFs-carbon nanotubes were accurately placed in a 100mL vacuum reaction tube, and the reverse rubber stopper was plugged. The vacuum was evacuated with a circulating water vacuum pump for 10 minutes to exhaust the air in the COFs and nanotube cavities as much as possible to form a negative pressure. 5g of the herbicide lactofenyl was weighed and dissolved in a ground-mouth conical flask containing 100mL of pure water to prepare a herbicide solution. The herbicide solution was injected into the vacuum reaction tube through the rubber stopper with a syringe and magnetically stirred for 8 hours. The mixed suspension was filtered with a sand core funnel, rinsed with deionized water 5 times to rinse off the free herbicide outside, and the obtained COFs-carbon nanotube-herbicide pesticide complex filter cake was dried at 80°C in a vacuum drying oven until constant weight. The dried COFs-carbon nanotubes-herbicide complex was crushed in a mortar to obtain COFs-carbon nanotubes-herbicide complex powder with a particle size distribution of 1000 nm.

[0066] The preparation method of the slow-release fully biodegradable weed-killing film comprises the following steps:

[0067] First, the COFs-carbon nanotube-herbicide complex and the fully biodegradable resin PPCP particles (particle size 2-4mm) were dried at 100°C for 8h, and added to a high-speed mixer at a mass ratio of 5:95 for 10min for pre-mixing to make the complex and the resin evenly mixed. The mixture was added to the feed port of the twin-screw extruder, the feed rate was 100g / min, the temperature of the seven zones from the feed port to the extruder head was set to: 175 / 175 / 170 / 165 / 165 / 160 / 155°C, the screw speed was 300rpm, and the resin was melted and blended, water-cooled, air-dried, and then entered the pelletizer for granulation to obtain a composite masterbatch.

[0068] The obtained composite masterbatch was then dried at 100°C for 8 hours, added to a single screw extruder for melt extrusion, and blown into a slow-release fully biodegradable weed control film by a film blowing machine. The temperature of the single screw extruder head and the heating zone was set to: 175 / 170 / 160 / 155°C, and the screw speed was 50rpm. The obtained slow-release fully biodegradable weed control film was packaged in a black opaque plastic bag and stored in a dry, cool and dark place. The thickness of the biodegradable weed control film was controlled at 20±1μm.

[0069] Accelerated release test of pesticides from weed control mulch in water:

[0070] The traditional non-slow-release pesticide weed killing film (referred to as non-slow-release film), the slow-release fully biodegradable weed killing film prepared in Example 2 (the mass of the COFs-carbon nanotubes-herbicide complex is 3% of the mass of the slow-release fully biodegradable weed killing film, recorded as slow-release film-3%), and the slow-release fully biodegradable weed killing film prepared in Example 3 (the mass of the COFs-carbon nanotubes-herbicide complex is 5% of the mass of the slow-release fully biodegradable weed killing film, recorded as slow-release film-5%) were used as film samples.

[0071] Accurately weigh 3g of the mulch sample, soak the mulch sample in a 200mL ground-mouth conical flask containing 100mL of pure water, cover the stopper, and place the conical flask in a constant temperature air bath oscillator with the temperature set to 40°C and the amplitude set to 20mm. Use a pipette to transfer 5mL of release liquid (i.e., herbicide pesticide aqueous solution) at regular intervals, and add 5mL of pure water to ensure that the total volume remains unchanged. Use liquid chromatography to detect the concentration of the herbicide pesticide aqueous solution and calculate the final cumulative release rate. The results are shown in Figure 1 .

[0072] Weed control test:

[0073] A weed control test was conducted using ryegrass as the test object, and the test design is as follows: prepare 5 flower pots with a diameter of 15 cm and a height of 10 cm, accurately weigh 300 g of nutrient soil and place it in the flower pots, and spray the same volume of deionized water. Accurately weigh 5 portions of 0.5 g ryegrass seeds, sprinkle them into the flower pots, cover them with a thin layer of soil, and then spray them with the same volume of water. A blank non-weeb film, a traditional non-slow-release weed control film, and a slow-release fully biodegradable weed control film prepared in Examples 1-3 were used as mulch film samples. Cut the 5 mulch film samples to the same length of about 30 cm, cover the flower pots, tie them tightly with rubber strips, and place them on a sunny and well-ventilated balcony to maintain the same environmental conditions. Take pictures on the 41st and 117th days of cultivation, and the results are shown in the table below. Figure 2 In the figure, A1 is a photograph of ryegrass covered with a blank non-weeding film on the 41st day, A2 is a photograph of ryegrass covered with a traditional non-slow-release weeding film on the 41st day, A3 is a photograph of ryegrass covered with a slow-release fully biodegradable weeding film prepared in Example 1 on the 41st day, A4 is a photograph of ryegrass covered with a slow-release fully biodegradable weeding film prepared in Example 2 on the 41st day, A5 is a photograph of ryegrass covered with a slow-release fully biodegradable weeding film prepared in Example 3 on the 41st day, B1 is a photograph of ryegrass covered with a blank non-weeding film on the 117th day, B2 is a photograph of ryegrass covered with a traditional non-slow-release weeding film on the 117th day, B3 is a photograph of ryegrass covered with a slow-release fully biodegradable weeding film prepared in Example 1 on the 117th day, B4 is a photograph of ryegrass covered with a slow-release fully biodegradable weeding film prepared in Example 2 on the 117th day, and B5 is a photograph of ryegrass covered with a slow-release fully biodegradable weeding film prepared in Example 3 on the 117th day.

[0074] The results showed that the blank non-weed removal film had a Figure 2 A1) and day 117 ( Figure 2 All ryegrasses in B1) grew normally and did not die. The traditional non-slow-release weed control film was Figure 2 A2) The weeding effect was obvious and the ryegrass had died; on the 117th day ( Figure 2 B2) The weed control effect was reduced, and the ryegrass was basically not dead, which shows that the non-slow-release weed control film no longer has a weed control effect on the 117th day. The slow-release fully biodegradable weed control film prepared in Example 1 was Figure 2 A3) The weeding effect was obvious and the ryegrass had died; on the 117th day ( Figure 2 B3) The weed control effect was still obvious, and all the ryegrass died. The slow-release fully biodegradable weed control film prepared in Example 2 was Figure 2 A4) The weeding effect was obvious and the ryegrass had died; on the 117th day ( Figure 2 B4) The weed control effect was still obvious, and all the ryegrass died. The slow-release fully biodegradable weed control film prepared in Example 3 was Figure 2 A5) The weeding effect was obvious and the ryegrass had died; on the 117th day ( Figure 2 At B5), the weed control effect was still obvious and all the ryegrass died.

[0075] The slow-release fully biodegradable weed killing film prepared in Examples 1-3 has a very obvious slow-release effect and has a long-lasting weed killing effect. The weed killing period of the slow-release fully biodegradable weed killing film prepared in Example 1 is 117 days, the weed killing period of the slow-release fully biodegradable weed killing film prepared in Example 2 is 130 days, and the weed killing period of the slow-release fully biodegradable weed killing film prepared in Example 3 is 145 days.

[0076] Mechanical properties test:

[0077] The blank non-weed control film, the traditional non-slow-release weed control film and the slow-release fully biodegradable weed control film prepared in Example 3 were used as film samples for mechanical property testing. The results are shown in Figure 3 In the figure, A is the tensile strength result diagram, B is the nominal strain at break result diagram, 1 is a blank non-weeding film, 2 is a traditional non-slow-release weeding film, and 3 is a slow-release fully biodegradable weeding film prepared in Example 3.

[0078] High temperature UV aging test:

[0079] The blank non-weed control film, the conventional non-slow-release weed control film and the slow-release fully biodegradable weed control film prepared in Example 3 were used as mulch film samples and tested according to the national standard GB / T 14522-2008. The loss rate of mechanical properties (nominal strain at break and tensile strength properties) of the mulch film samples after exposure to a high-temperature UV aging box at 60°C for 9 days is shown in Table 1. Figure 4 In the figure, 1 is a blank non-weeding film, 2 is a traditional non-slow-release weeding film, and 3 is a slow-release fully biodegradable weeding film prepared in Example 3.

[0080] Covalent organic framework materials (COFs) can effectively absorb ultraviolet rays and are excellent ultraviolet-visible shielding materials. COFs materials were tested and the ultraviolet-visible absorption spectrum of COFs materials is shown in Figure 5 .

Claims

1. A method for preparing a slow-release fully biodegradable weed control film, characterized in that The COFs-carbon nanotubes-herbicide pesticide complex and a fully biodegradable resin are melt-blended and extruded and blow-molded to obtain a slow-release fully biodegradable herbicide film; wherein the COFs-carbon nanotubes-herbicide pesticide complex is prepared by loading the herbicide on the COFs-carbon nanotubes; The COFs-carbon nanotube preparation method comprises the following steps: reacting 2,6,14-triaminotriptycene, 1,4,5,8-naphthalenetetracarboxylic anhydride, carbon nanotubes, N,N-dimethylformamide and propionic acid, cooling to room temperature after the reaction, and filtering to obtain a solid product; washing, freezing and freeze-drying the solid product to obtain the COFs-carbon nanotube.

2. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 1, characterized in that The herbicide is one or more of oxyfluorfen, acifluorfen, lactofen, fomesafen, fluazifop-butyl, bromoxynil, bromoxynil octanoyl or ioxynil octanoyl.

3. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 1, characterized in that The ratio of 2,6,14-triaminotriptycene, 1,4,5,8-naphthalenetetracarboxylic anhydride, carbon nanotubes, N,N-dimethylformamide and propionic acid is 0.1-0.3:0.1-0.3:0.002-0.18:10-15:5-8, wherein 2,6,14-triaminotriptycene is measured in g, 1,4,5,8-naphthalenetetracarboxylic anhydride is measured in g, carbon nanotubes are measured in g, N,N-dimethylformamide is measured in mL, and propionic acid is measured in mL.

4. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 1, characterized in that The reaction temperature is 120-220°C, and the reaction time is 12-36h; the freezing temperature is -10--50°C, and the freezing time is 6-18h; the freeze-drying temperature is -10--50°C, and the freeze-drying time is 12-36h.

5. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 1, characterized in that The preparation method of the COFs-carbon nanotube-herbicide pesticide complex is to dissolve the herbicide in deionized water to prepare a herbicide solution, and stir the COFs-carbon nanotube and the herbicide solution to obtain a mixed suspension; The mixed suspension is filtered and rinsed to obtain a filter cake, and the filter cake is dried to obtain a COFs-carbon nanotube-herbicide complex.

6. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 5, characterized in that The concentration of the herbicide solution is 0.01-0.2 g / mL, and the mass ratio of COFs-carbon nanotubes to the herbicide solution is 5-50:

3.

7. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 5, characterized in that The stirring time is 3-8 hours; the rinsing is performed with deionized water for 2-5 times; and the drying temperature is 30-80°C.

8. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 1, characterized in that The fully biodegradable resin is one or more of PHA, BSR, PPCP or PGA, and the particle size of the COFs-carbon nanotube-herbicide complex is 10-1000nm.

9. The method for preparing the sustained-release fully biodegradable weed-killing film according to claim 1, characterized in that The mass ratio of the COFs-carbon nanotube-herbicide complex to the fully biodegradable resin is 0.5-5:95-99.5.

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