A slow-release pesticide preparation containing modified montmorillonite and its application

Abstract

The present application relates to a kind of modified montmorillonite-containing slow-release pesticide preparation and its application, belong to the technical field of pesticide preparation, nano-silicon dioxide and montmorillonite are mixed calcination, form rigid porous framework, then the complex of ferroferric oxide and chitosan is formed by physical adsorption and interface bonding and loaded on the surface of composite framework, form modified montmorillonite, after surface functionalization treatment by silane coupling agent, it is synergized with polylactic acid-glycolic acid copolymer to form dense shell layer, pesticide is wrapped inside, then selenium treatment is formed, the composite structure of rigid structure plus outer shell layer, solve the pain point that traditional slow-release preparation mechanical strength is weak, its rigid framework can resist extrusion in field soil, dense shell layer and selenium layer synergistically resist rainwater scouring, while the layered barrier of montmorillonite and the antioxidant properties of selenium layer form synergistic protection, so that the pesticide preparation still has good retention under long time irradiation of ultraviolet, significantly improve the stability of preparation in complex field environment.

Description

Technical Field

[0001] This invention belongs to the field of pesticide formulation technology, and relates to a slow-release pesticide formulation containing modified montmorillonite and its application. Background Technology

[0002] Pesticide controlled-release technology, by controlling the release rate of active ingredients, can increase pesticide utilization by 20%-50%, reduce application rates by 30%-60%, significantly extend the duration of effectiveness, and reduce environmental risks, becoming a core approach to solving the drawbacks of traditional pesticides. In the research and development of controlled-release carrier materials, montmorillonite, with its excellent cation exchange capacity, high specific surface area, and adsorption performance, has become a highly promising natural mineral carrier. While natural montmorillonite is widely used in construction and environmental protection, its research and application in pesticide controlled-release are still relatively limited. Its inherent properties are insufficient to meet the requirements of precise controlled release, necessitating modification to optimize carrier function. Modification can significantly improve the adsorption capacity, controlled-release stability, and environmental adaptability of montmorillonite. For example, modified montmorillonite can be combined with materials such as carboxymethyl chitosan-starch to form an encapsulation structure, effectively delaying the release of active ingredients in pesticides such as herbicides and insecticides, while simultaneously enhancing the water resistance and UV shielding ability of the formulation, reducing pesticide degradation and loss.

[0003] Chinese invention patent application CN116114691A discloses a pH-responsive pesticide slow-release hydrogel ball and its preparation method. It uses carboxylated nanocellulose crystals modified with polyethyleneimine as raw materials, which are self-assembled with modified montmorillonite through electrostatic bonding. Pesticides are loaded in an organic solvent, and sodium alginate is used as a coating material and anhydrous calcium chloride as a crosslinking agent. The pH-responsive pesticide slow-release hydrogel ball composed of nanocellulose crystals and montmorillonite is prepared by drop addition and is used for the slow release of pesticides in the soil environment.

[0004] The slow-release hydrogel spheres in the above-mentioned technical solutions have problems such as large surface pores and weak mechanical strength due to the carrier network structure. In actual field applications, they are easily damaged by external forces such as rainwater erosion and soil compression, which can lead to unexpected burst release of pesticide active ingredients. This not only reduces the effective utilization rate of pesticides, but also significantly shortens the field retention period of pesticide formulations, making it difficult to achieve continuous control of crop diseases. Summary of the Invention

[0005] The purpose of this invention is to provide a slow-release pesticide formulation containing modified montmorillonite and its application. Through the construction of a composite carrier, functional modification, core-shell encapsulation and selenization treatment, the mechanical strength of the formulation is improved and the slow-release performance is optimized.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A slow-release pesticide formulation containing modified montmorillonite is prepared by the following steps:

[0008] Step 1: Mix nano-silica powder with montmorillonite evenly, and calcine to obtain silica-montmorillonite composite powder. Then mix iron salt solution and chitosan solution to obtain precursor solution. Then load the precursor solution onto silica-montmorillonite composite powder through physical adsorption and interfacial bonding to obtain modified montmorillonite.

[0009] Step 2: Surface-treat the modified montmorillonite with a silane coupling agent to obtain surface-functionalized modified montmorillonite. Then, use polylactic acid-glycolic acid copolymer and surface-functionalized modified montmorillonite as a shell to encapsulate the prothioconazole technical inside, obtaining nanocapsule particles. Then, perform selenization modification on the nanocapsule particles to obtain a slow-release pesticide formulation containing modified montmorillonite.

[0010] Furthermore, the preparation process of modified montmorillonite is as follows:

[0011] Ferric chloride hexahydrate, ferric chloride tetrahydrate, and deionized water were added to a reaction vessel and stirred at 90-100℃ and 500-700 r / min for 30-40 min. Then, a chitosan solution with a concentration of 2.5-3.5 wt% was added dropwise, and the reaction was carried out for 1-2 h to obtain a precursor solution. A silica-montmorillonite composite powder suspension with a concentration of 12.4-16.7 g / L was added to the precursor solution and stirred for 6-8 h. The mixture was then filtered, washed, and dried to obtain modified montmorillonite.

[0012] Furthermore, the ratio of ferric chloride hexahydrate, ferric chloride tetrahydrate, deionized water, and chitosan solution is 155-170g: 56-63g: 9-11L: 550-650mL.

[0013] Furthermore, the volume ratio of the silica-montmorillonite composite powder suspension to the precursor solution is 4.5-5.5: 9.5-11.6.

[0014] Furthermore, the preparation process of the silica-montmorillonite composite powder is as follows:

[0015] Nano-sized silica powder with a particle size of 20 nm, montmorillonite, and deionized water were added to a reaction vessel and stirred for 2-3 hours. The mixture was then filtered, dried, and placed in a muffle furnace. It was calcined at 400-500℃ for 4-5 hours, cooled to room temperature, ground, and sieved to obtain silica-montmorillonite composite powder.

[0016] Furthermore, the ratio of nano-silica powder, montmorillonite, and deionized water is 95-105g: 75-85g: 4.5-5.5L.

[0017] Furthermore, the preparation process of the nanocapsule particles is as follows:

[0018] Polylactic acid-glycolic acid copolymer, surface-functionalized montmorillonite, prothioconazole technical and dichloromethane were added to a reaction vessel and added dropwise to a 1 wt% carboxymethyl chitosan aqueous solution under stirring. The mixture was then treated with an ultrasonic cell disruptor at 0-5℃ for 30-40 min, evaporated under reduced pressure, centrifuged, resuspended in deionized water, and freeze-dried to obtain nanocapsule particles.

[0019] Furthermore, the ratio of polylactic acid-glycolic acid copolymer, surface-functionalized modified montmorillonite, prothioconazole technical, dichloromethane, and carboxymethyl chitosan aqueous solution is 85-95g: 30-40g: 55-65g: 55-65g: 28-32L; the power of the ultrasonic cell disruptor is 800W.

[0020] Furthermore, the preparation process of the modified montmorillonite slow-release pesticide formulation is as follows:

[0021] Selenium powder and sodium borohydride were added to a reaction vessel, and deionized water was added under nitrogen protection and at 0-5℃. The mixture was stirred for 5-6 hours, and then nanocapsule particles were added. The mixture was stirred for 36-40 hours, filtered, washed, and freeze-dried to obtain a slow-release pesticide formulation containing modified montmorillonite.

[0022] Furthermore, the ratio of selenium powder, sodium borohydride, deionized water, and nanocapsule particles is 6.0-6.6g: 4.3-4.8g: 0.9-1.1L: 95-105g.

[0023] Application of a slow-release pesticide formulation containing modified montmorillonite in the control of fungal diseases.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention involves calcining nano-silica and montmorillonite to form a rigid porous framework. A complex formed from iron oxide and chitosan is then loaded onto the surface of the composite framework through physical adsorption and interfacial bonding to form modified montmorillonite. This modified montmorillonite is then surface-functionalized with a silane coupling agent, synergistically forming a dense shell with polylactic acid-glycolic acid copolymer to encapsulate the pesticide. Further selenization treatment creates a composite structure with a rigid structure and an outer shell, addressing the weakness of traditional slow-release formulations in terms of mechanical strength. The rigid framework can withstand soil compression in the field, while the dense shell and selenization layer synergistically resist rainwater erosion. Simultaneously, the layered barrier properties of montmorillonite and the antioxidant properties of the selenization layer provide synergistic protection, ensuring good retention of the pesticide formulation even under prolonged ultraviolet irradiation. This significantly improves the stability and lifespan of the formulation in complex field environments.

[0026] 2. The modified montmorillonite of this invention has a high specific surface area and multiple adsorption sites. Combined with surface treatment with a silane coupling agent, the montmorillonite changes from hydrophilic to hydrophilic-hydrophobic amphoteric, improving its interfacial compatibility with polylactic acid-glycolic acid copolymer, thereby increasing the pesticide loading capacity. The surface-functionalized modified montmorillonite is distributed in the core-shell gap and outer shell through chemical bonding and physical entanglement. Together with the ester bond hydrolysis characteristics of polylactic acid-glycolic acid copolymer, it forms a slow-release barrier, further extending the pesticide slow-release time, avoiding pesticide waste and environmental risks, and achieving continuous control of crop diseases.

[0027] 3. In the preparation of nanocapsules, carboxymethyl chitosan acts as an emulsifier adsorbed at the oil-water interface. The hydroxyl and carboxyl groups in its molecular chain form electrostatic attraction and hydrogen bonding with the amino groups on the surface of surface-functionalized montmorillonite. This not only stabilizes the oil droplet structure but also synergistically improves the surface hydrophilicity and hydrophobicity of the formulation, reducing the contact angle of the slow-release pesticide formulation on the wheat leaf surface. It exhibits excellent wetting and adhesion properties, improving the field application effect. At the same time, the polylactic acid-glycolic acid copolymer, montmorillonite, and chitosan carrier materials all have good biocompatibility and degradability. Selenium is an essential trace element for plants and is stably anchored through Se-C bonds, avoiding non-target biological toxicity. This reduces the amount of pesticides applied and also reduces the impact on soil microbial communities and aquatic ecological environments, meeting the needs of green agricultural development.

[0028] 4. This invention uses prothioconazole as the core antibacterial component, which fundamentally destroys the cell membrane structure of pathogens. At the same time, the Fe3O4 in the modified montmorillonite has Fenton-like catalytic properties, which can induce the production of a small amount of reactive oxygen species in the microenvironment of pathogens. The -SeH groups of the selenized layer can induce pathogens to produce excessive reactive oxygen species, destroying their cell membrane structure. This synergistically enhances the inhibitory effect on fungal diseases such as wheat scab and stem rot. In addition, the high efficiency and slow-release properties of the formulation reduce the number of applications, which reduces agricultural production costs and alleviates environmental pressure. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0030] Example 1: This example provides a slow-release pesticide formulation containing modified montmorillonite, prepared through the following steps:

[0031] S1: 100g of 20nm nano-silica powder (purchased from Qinghe County Chaotai Metal Materials Co., Ltd.), 80g of montmorillonite (analytical grade, purchased from Tianjin Huasheng Chemical Reagent Co., Ltd.) and 5.0L of deionized water were added to a reaction vessel and stirred at 400r / min for 2h. After centrifugation and filtration, the mixture was dried at 68℃ for 11h and then placed in a muffle furnace and calcined at 450℃ for 4h to enhance the bonding stability of silica and montmorillonite. After calcination, the mixture was cooled to room temperature, ground, and passed through a 100-mesh sieve to obtain silica-montmorillonite composite powder.

[0032] S2: 162.5g of ferric chloride hexahydrate (analytical grade, purchased from Shanghai Wokai Biotechnology Co., Ltd.), 59.5g of ferric chloride tetrahydrate (analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.), and 10.0L of deionized water were added to a reaction vessel and stirred at 95℃ and 600r / min for 35min. Then, 600mL of 3.0wt% chitosan solution was added dropwise, and the reaction was carried out for 1.5h to obtain a precursor solution. Then, 71.5g of silica-montmorillonite composite powder and 5.0L of deionized water were added to the reaction vessel and mixed evenly. This mixture was then added to 10.6L of the precursor solution and stirred at 95℃ and 600r / min for 7h. After the reaction was completed, the mixture was centrifuged and filtered. The precipitate was washed four times with deionized water and dried at 68℃ for 13h to obtain modified montmorillonite.

[0033] S3: Add 40g of modified montmorillonite and 1.0L of deionized water to the reactor, ultrasonically disperse for 35min, add 75mL of 0.5wt% silane coupling agent KH-550, stir for 2.5h at 55℃ and 350r / min, centrifuge and filter, and dry at 70℃ for 13h to obtain surface-functionalized modified montmorillonite.

[0034] The hydroxyl groups on the surface of modified montmorillonite undergo a condensation reaction with the hydroxyl groups formed by the hydrolysis of silane coupling agent KH-550, changing its surface from hydrophilic to hydrophilic-hydrophobic amphoteric.

[0035] S4: 90g of polylactic acid-glycolic acid copolymer (molecular weight 50000Da, purchased from Maclean Biochemical Co., Ltd.), 35g of surface-functionalized modified montmorillonite, 60g of prothioconazole technical grade (95%, purchased from Qingdao Hailier Pharmaceutical Group Co., Ltd.), and 1.5L of dichloromethane were added to a reaction vessel and mixed evenly. The mixture was then dropped into 30L of 1wt% carboxymethyl chitosan (purchased from Zhejiang Jinke Pharmaceutical Co., Ltd.) aqueous solution at 850r / min. The mixture was treated with an ultrasonic cell disruptor at 2℃ for 35min at 800W, and then evaporated under reduced pressure at 42℃ for 35min to remove dichloromethane. The mixture was centrifuged at 8750r / min for 8min, the precipitate was collected, resuspended in 500mL of deionized water, and freeze-dried at -47℃ for 23h to obtain nanocapsule particles.

[0036] Polylactic acid-glycolic acid copolymer (PLA-GAC) and pesticides are dissolved in dichloromethane to form an oil phase. Surface-functionalized montmorillonite binds to the PLA-GAC molecular chains through hydrophobic interactions. After adding carboxymethyl chitosan, the chitosan acts as an emulsifier and is adsorbed at the oil-water interface. The hydroxyl and carboxyl groups in the chitosan molecular chains form electrostatic attraction and hydrogen bonding with the amino groups on the surface of the surface-functionalized montmorillonite, reducing interfacial tension. Combined with high-speed stirring and ultrasonic disruption, micron-sized oil droplets are formed. After removing dichloromethane by vacuum evaporation, PLA-GAC molecules self-assemble on the surface of the oil droplets to form a core-shell structure, encapsulating the pesticide inside. The surface-functionalized montmorillonite is distributed on the outer shell or in the core-shell gap through chemical bonding and physical entanglement, forming a composite structure.

[0037] S5: 6.3g of selenium powder (99%, purchased from Maclean Biochemical Co., Ltd.) and 4.55g of sodium borohydride (99%, provided by the synthesis laboratory) were added to the reactor. Under nitrogen protection and at 2°C, 1.0L of deionized water was added and stirred at 400r / min for 5.5h. Then, 100g of nanocapsule particles were added and stirred at 500r / min for 38h. After centrifugation and filtration, the precipitate was washed four times with deionized water and freeze-dried at -47°C for 22h to obtain a slow-release pesticide formulation containing modified montmorillonite.

[0038] Sodium borohydride reduces selenium powder in aqueous solution to produce sodium selenide, where Se is converted to Se. 2- In its present form, it reacts with the carbonyl groups on the surface of the polylactic acid-glycolic acid copolymer to form -SeH groups, which are stably anchored to the capsule surface through Se-C bonds. Simultaneously, the surface-functionalized montmorillonite can physically adsorb and fix some sodium selenide, allowing Se to... 2- It is more evenly distributed on the surface of the capsule.

[0039] Example 2: This example provides a slow-release pesticide formulation containing modified montmorillonite, prepared through the following steps:

[0040] S1: 95g of 20nm nano-silica powder (purchased from Qinghe County Chaotai Metal Materials Co., Ltd.), 75g of montmorillonite (analytical grade, purchased from Tianjin Huasheng Chemical Reagent Co., Ltd.) and 4.5L of deionized water were added to a reaction vessel and stirred at 300r / min for 2h. After centrifugation and filtration, the mixture was dried at 65℃ for 10h and then placed in a muffle furnace and calcined at 400℃ for 4h to enhance the bonding stability of silica and montmorillonite. After calcination, the mixture was cooled to room temperature, ground, and passed through a 100-mesh sieve to obtain silica-montmorillonite composite powder.

[0041] S2: 155g of ferric chloride hexahydrate (analytical grade, purchased from Shanghai Wokai Biotechnology Co., Ltd.), 56g of ferric chloride tetrahydrate (analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.), and 9.0L of deionized water were added to a reaction vessel and stirred at 90℃ and 500r / min for 30min. Then, 550mL of 2.5wt% chitosan solution was added dropwise, and the reaction was carried out for 1h to obtain a precursor solution. Next, 68g of silica-montmorillonite composite powder and 4.5L of deionized water were added to the reaction vessel and mixed evenly. This mixture was then added to 9.5L of the precursor solution and stirred at 90℃ and 500r / min for 6h. After the reaction was completed, the mixture was centrifuged and filtered. The precipitate was washed three times with deionized water and dried at 65℃ for 12h to obtain modified montmorillonite.

[0042] S3: Add 30g of modified montmorillonite and 0.8L of deionized water to the reactor, ultrasonically disperse for 30min, add 50mL of 0.5wt% silane coupling agent KH-550, stir for 2h at 50℃ and 300r / min, centrifuge and filter, and dry at 65℃ for 12h to obtain surface-functionalized modified montmorillonite.

[0043] S4: 85g of polylactic acid-glycolic acid copolymer (molecular weight 50000Da, purchased from Maclean Biochemical Co., Ltd.), 30g of surface-functionalized modified montmorillonite, 55g of prothioconazole technical grade (95%, purchased from Qingdao Hailier Pharmaceutical Group Co., Ltd.), and 1.4L of dichloromethane were added to a reaction vessel and mixed evenly. The mixture was then dropped into 28L of 1wt% carboxymethyl chitosan (purchased from Zhejiang Jinke Pharmaceutical Co., Ltd.) aqueous solution at 800r / min. The mixture was treated with an ultrasonic cell disruptor at 0℃ for 30min at 800W, and then evaporated under reduced pressure at 40℃ for 30min to remove dichloromethane. The mixture was centrifuged at 8500r / min for 7min, the precipitate was collected, resuspended in 450mL of deionized water, and freeze-dried at -45℃ for 22h to obtain nanocapsule particles.

[0044] S5: 6.0 g of selenium powder (99%, purchased from Maclean Biochemical Co., Ltd.) and 4.3 g of sodium borohydride (99%, provided by the synthesis laboratory) were added to the reactor. 0.9 L of deionized water was added under nitrogen protection and at 0 °C. The mixture was stirred at 300 r / min for 5 h. Then, 95 g of nanocapsule particles were added and stirred at 500 r / min for 36 h. The mixture was centrifuged and filtered. The precipitate was washed three times with deionized water and freeze-dried at -45 °C for 20 h to obtain a slow-release pesticide formulation containing modified montmorillonite.

[0045] Example 3: This example provides a slow-release pesticide formulation containing modified montmorillonite, prepared through the following steps:

[0046] S1: 105g of 20nm nano-silica powder (purchased from Qinghe County Chaotai Metal Materials Co., Ltd.), 85g of montmorillonite (analytical grade, purchased from Tianjin Huasheng Chemical Reagent Co., Ltd.) and 5.5L of deionized water were added to a reaction vessel and stirred at 500r / min for 3h. After centrifugation and filtration, the mixture was dried at 70℃ for 12h and then placed in a muffle furnace and calcined at 500℃ for 5h to enhance the bonding stability of silica and montmorillonite. After calcination, the mixture was cooled to room temperature, ground, and passed through a 100-mesh sieve to obtain silica-montmorillonite composite powder.

[0047] S2: 170g of ferric chloride hexahydrate (analytical grade, purchased from Shanghai Wokai Biotechnology Co., Ltd.), 63g of ferric chloride tetrahydrate (analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.), and 11.0L of deionized water were added to a reaction vessel and stirred at 100℃ and 700r / min for 40min. Then, 650mL of 3.5wt% chitosan solution was added dropwise, and the reaction was carried out for 2h to obtain a precursor solution. Next, 75g of silica-montmorillonite composite powder and 5.5L of deionized water were added to the reaction vessel and mixed evenly. This mixture was then added to 11.6L of the precursor solution and stirred at 100℃ and 700r / min for 8h. After the reaction was completed, the mixture was centrifuged and filtered. The precipitate was washed 5 times with deionized water and dried at 70℃ for 14h to obtain modified montmorillonite.

[0048] S3: Add 50g of modified montmorillonite and 1.2L of deionized water to the reactor, ultrasonically disperse for 40min, add 100mL of 0.5wt% silane coupling agent KH-550, stir for 3h at 60℃ and 400r / min, centrifuge and filter, and dry at 75℃ for 14h to obtain surface-functionalized modified montmorillonite.

[0049] S4: 95g of polylactic acid-glycolic acid copolymer (molecular weight 50000 Da, purchased from Maclean Biochemical Co., Ltd.), 40g of surface-functionalized modified montmorillonite, 65g of prothioconazole technical (95%, purchased from Qingdao Hailier Pharmaceutical Group Co., Ltd.), and 1.6L of dichloromethane were added to a reaction vessel and mixed evenly. The mixture was then dropped into 32L of 1wt% carboxymethyl chitosan (purchased from Zhejiang Jinke Pharmaceutical Co., Ltd.) aqueous solution at 900r / min. The mixture was treated with an ultrasonic cell disruptor at 5℃ for 40min at 800W, and then evaporated under reduced pressure at 45℃ for 40min to remove dichloromethane. The mixture was centrifuged at 9000r / min for 10min, the precipitate was collected, resuspended in 550mL of deionized water, and freeze-dried at -50℃ for 24h to obtain nanocapsule particles.

[0050] S5: 6.6g of selenium powder (99%, purchased from Maclean Biochemical Co., Ltd.) and 4.8g of sodium borohydride (99%, provided by the synthesis laboratory) were added to the reactor. Under nitrogen protection and at 5°C, 1.1L of deionized water was added and stirred at 500r / min for 6h. Then, 105g of nanocapsule particles were added and stirred at 500r / min for 40h. After centrifugation and filtration, the precipitate was washed 5 times with deionized water and freeze-dried at -50°C for 24h to obtain a slow-release pesticide formulation containing modified montmorillonite.

[0051] Example 4: This example provides a slow-release pesticide formulation containing modified montmorillonite. The difference from Example 1 is that in step S3, silane coupling agent KH-540 is used instead of silane coupling agent KH-550.

[0052] Example 5: This example provides a slow-release pesticide formulation containing modified montmorillonite. The difference from Example 1 is that a polylactic acid-glycolic acid copolymer with a molecular weight of 60,000 Da is used in step S4.

[0053] Comparative Example 1: This comparative example provides a slow-release pesticide formulation containing modified montmorillonite. The difference from Example 1 is that in step S3, the silica-montmorillonite composite powder prepared in step S1 is used instead of the modified montmorillonite.

[0054] Comparative Example 2: This comparative example provides a slow-release pesticide formulation containing modified montmorillonite. The difference from Example 1 is that in step S4, the modified montmorillonite prepared in step S3 is used instead of the surface-functionalized modified montmorillonite.

[0055] Comparative Example 3: This comparative example provides a slow-release pesticide formulation containing modified montmorillonite. The difference from Example 1 is that in step S4, the silica-montmorillonite composite powder prepared in step S1 is used instead of the surface-functionalized modified montmorillonite.

[0056] Comparative Example 4: This comparative example provides a slow-release pesticide formulation containing modified montmorillonite. The difference from Example 1 is that step S5 is not performed. The nanocapsule particles prepared in step S4 are the slow-release pesticide formulation containing modified montmorillonite.

[0057] The performance of the slow-release pesticide formulations containing modified montmorillonite prepared in Examples 1-5 and Comparative Examples 1-4 was tested:

[0058] Rainwater erosion and abrasion test: Take 5g of sample and spread it evenly on a 100-mesh stainless steel sieve (fixed below the funnel), and place a collection bottle below the funnel; use a spray device to simulate rainfall, set the spray pressure to 0.3MPa, water flow rate to 10mL / min, and spray height to 30cm, and spray continuously for 60min (corresponding to 2h of moderate rainfall intensity); after spraying, collect the sample remaining on the sieve and calculate the erosion resistance retention rate (erosion resistance retention rate = residual sample mass / initial sample mass × 100%). Repeat the test 3 times for each sample and take the average value.

[0059] Drug loading determination: 10 mg of sample was weighed and dispersed in a certain amount of dichloromethane. The sample was repeatedly ultrasonically stirred to fully dissolve the prothioconazole technical. The absorbance of the solution at a wavelength of 254 nm was measured by ultraviolet spectrophotometer to analyze the content of prothioconazole technical in the nanocapsules.

[0060] Leaf wettability determination: The wettability of slow-release pesticide formulations containing modified montmorillonite on the surface of wheat leaves within 3 minutes was evaluated using the stop-drop method. Wheat leaves were fixed on a glass slide, and then 5 μL of a 100 mg / L sample aqueous suspension was dropped onto the leaves using a microsyringe. The change in contact angle value was recorded using a contact angle meter.

[0061] UV resistance test: To measure the stability of the slow-release pesticide formulation containing modified montmorillonite under ultraviolet irradiation, a 30 vol% ethanol aqueous solution was first prepared. 1 mg of the slow-release pesticide formulation containing modified montmorillonite was added to 30 mL of the ethanol aqueous solution, and after thorough dispersion, it was placed in a sample bottle and irradiated for 120 h at a distance of 20 cm from an 18 W (254 nm) ultraviolet light source at a temperature of 25 °C. Samples were taken at regular intervals, and the absorbance of the samples was measured using an ultraviolet spectrophotometer to analyze the changes in the content of prothioconazole technical.

[0062] Sustained-release performance determination: The experiment was conducted at room temperature. Release tests were performed in 40 mL of a release medium containing ethanol and water (30:70). The same amount of a sustained-release pesticide formulation containing modified montmorillonite was added to a dialysis bag (molecular weight cutoff: 14000 g / mol). The dialysis bag was immersed in the release medium and stirred at 150 r / min at 25℃. At specific time intervals, 1 mL of release medium was removed and the same volume of fresh release medium was added. The content of prothioconazole technical in the medium was detected at a wavelength of 254 nm using a UV spectrometer, and the cumulative release amount was calculated.

[0063] The test results are shown in the table below:

[0064] Table 1 Performance Test Overview

[0065]

[0066] As shown in Table 1, the erosion resistance retention rates of Examples 1-5 are greater than those of Comparative Examples 1-4. This may be because the nano-silica and montmorillonite form a rigid porous framework after calcination, and the polylactic acid-glycolic acid copolymer and surface-functionalized montmorillonite form a dense shell through chemical bonding and physical entanglement. After selenization treatment, they can synergistically resist rainwater erosion and external pressure, thereby improving the mechanical strength of the slow-release pesticide formulation containing modified montmorillonite.

[0067] As shown in Table 1, the drug loading of Examples 1-5 is higher than that of Comparative Examples 1-3. This may be because the modified montmorillonite has a large specific surface area and multiple adsorption sites. After being modified by silane coupling agent, it becomes hydrophilic-hydrophobic, which improves the interfacial compatibility with prothioconazole, thereby increasing the drug loading.

[0068] As shown in Table 1, the leaf contact angles of Examples 1-5 are smaller than those of Comparative Examples 1-3. This may be because carboxymethyl chitosan and surface-functionalized montmorillonite form a synergistic wettability optimization. Carboxymethyl chitosan, as an emulsifier, is adsorbed at the oil-water interface. The hydroxyl and carboxyl groups in its molecular chain form electrostatic attraction and hydrogen bonding with the amino groups on the surface of surface-functionalized montmorillonite, which synergistically regulate the hydrophilicity and hydrophobicity of the formulation surface, reduce the contact angle with wheat leaves, and improve wettability and adhesion.

[0069] As shown in Table 1, the pesticide retention rates after 120 hours of UV irradiation in Examples 1-5 were greater than those in Comparative Examples 1-4. This may be because montmorillonite and the selenization layer formed a synergistic UV protection system: the layered structure of montmorillonite can block UV penetration and reduce pesticide photodegradation; the -SeH groups of the selenization layer have antioxidant properties and can remove reactive oxygen species generated by UV irradiation, preventing pesticide molecules from being oxidized and destroyed.

[0070] As shown in Table 1, the 24-hour burst release rate of Examples 1-5 was lower than that of Comparative Examples 1-4, and the 120-hour release rate was also lower than that of Comparative Examples 1-4. This may be because the surface-functionalized modified montmorillonite is distributed in the core-shell gap and outer shell through chemical bonding and physical entanglement, forming a physical barrier. The ester bond hydrolysis characteristics of polylactic acid-glycolic acid copolymer enable slow degradation and release. The two work together to delay pesticide diffusion and avoid initial burst release. In addition, the selenized layer plays a role in sealing the pores of the shell, making the release rate more stable.

[0071] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A slow-release pesticide formulation containing modified montmorillonite, characterized in that, Prepared by the following steps: Step 1: Mix nano-silica powder with montmorillonite evenly, and calcine to obtain silica-montmorillonite composite powder. Then mix iron salt solution and chitosan solution to obtain precursor solution. Then load the precursor solution onto silica-montmorillonite composite powder through physical adsorption and interfacial bonding to obtain modified montmorillonite. Step 2: Surface-treat the modified montmorillonite with a silane coupling agent to obtain surface-functionalized modified montmorillonite. Then, use polylactic acid-glycolic acid copolymer and surface-functionalized modified montmorillonite as shells to encapsulate the prothioconazole technical inside to obtain nanocapsule particles. Then, perform selenization modification on the nanocapsule particles to obtain a slow-release pesticide formulation containing modified montmorillonite. The preparation process of the modified montmorillonite is as follows: Ferric chloride hexahydrate, ferric chloride tetrahydrate, and deionized water were added to a reaction vessel and stirred at 90-100℃ and 500-700 r / min for 30-40 min. Then, a chitosan solution with a concentration of 2.5-3.5 wt% was added dropwise, and the reaction was carried out for 1-2 h to obtain a precursor solution. A silica-montmorillonite composite powder suspension with a concentration of 12.4-16.7 g / L was added to the precursor solution and stirred for 6-8 h. The mixture was then filtered, washed, and dried to obtain modified montmorillonite. The ratio of the amounts of ferric chloride hexahydrate, ferric chloride tetrahydrate, deionized water, and chitosan solution is 155-170g: 56-63g: 9-11L: 550-650mL. The volume ratio of the silica-montmorillonite composite powder suspension to the precursor solution is 4.5-5.5: 9.5-11.

6. The preparation process of the silica-montmorillonite composite powder is as follows: Nano-silica powder, montmorillonite, and deionized water are added to a reaction vessel and stirred for 2-3 hours. The mixture is then filtered, dried, and placed in a muffle furnace. It is calcined at 400-500℃ for 4-5 hours, cooled to room temperature, ground, and sieved to obtain silica-montmorillonite composite powder. The ratio of the nano-silica powder, montmorillonite, and deionized water is 95-105g: 75-85g: 4.5-5.5L; The preparation process of the nanocapsule particles is as follows: Polylactic acid-glycolic acid copolymer, surface-functionalized montmorillonite, prothioconazole technical and dichloromethane were added to a reaction vessel and added dropwise to a 1 wt% carboxymethyl chitosan aqueous solution under stirring. The mixture was then treated with an ultrasonic cell disruptor at 0-5℃ for 30-40 min, evaporated under reduced pressure, centrifuged, resuspended in deionized water, and freeze-dried to obtain nanocapsule particles. The ratio of the polylactic acid-glycolic acid copolymer, surface-functionalized modified montmorillonite, prothioconazole technical, dichloromethane, and carboxymethyl chitosan aqueous solution is 85-95g:30-40g:55-65g:55-65g:28-32L; the power of the ultrasonic cell disruptor is 800W. The preparation process of the slow-release pesticide formulation containing modified montmorillonite is as follows: Selenium powder and sodium borohydride were added to a reaction vessel, and deionized water was added under nitrogen protection and at 0-5℃. The mixture was stirred for 5-6 hours, and then nanocapsule particles were added. The mixture was stirred for 36-40 hours, filtered, washed, and freeze-dried to obtain a slow-release pesticide formulation containing modified montmorillonite. The ratio of selenium powder, sodium borohydride, deionized water, and nanocapsule particles is 6.0-6.6g: 4.3-4.8g: 0.9-1.1L: 95-105g.

2. The application of the slow-release pesticide formulation containing modified montmorillonite according to claim 1 in the prevention and control of fungal diseases.

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