Montmorillonite-based pesticide microcapsule suspension, preparation method and application thereof

Abstract

The present invention discloses a montmorillonite-based pesticide microcapsule suspension, a preparation method, and applications thereof. The pesticide microcapsule suspension comprises a pesticide, an organic solvent, isophorone diisocyanate, dibutyltin dilaurate, montmorillonite, and water in a weight ratio of 5-10:0-10:0.5-2:0.025-0.1:8-12:300-500, using a Pickering emulsion as a template and a process combining emulsification and interfacial polymerization. The pesticide microcapsules of the present invention have low preparation cost, sustained release, high safety, and good application efficacy, providing a solid technical foundation for the development of sustainable, environmentally friendly, and highly efficient new pesticides.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide preparations, and particularly relates to a pesticide microcapsule suspension based on nano-montmorillonite and a preparation method thereof. Background Art

[0002] In modern agricultural production, pesticides play an irreplaceable role in controlling pests and diseases and increasing crop yields. Conventional pesticide formulations include emulsifiable concentrates, microemulsions, suspensions, and powders. However, due to their low efficiency, less than 30% of the active ingredients reach the target organisms, while the remainder enters the surrounding natural environment, resulting in significant economic losses, environmental pollution, and even harm to human health. These limitations have promoted the development of novel pesticide delivery systems, including water-based nanopesticides, micro- / nanoemulsions, solid nanodispersions, and microcapsules. These advanced formulations focus on eco-friendliness and environmental safety, offering benefits such as controlled release of the active ingredients, extended shelf life, and reduced acute toxicity to non-target organisms.

[0003] The Pickering emulsion template method is a common method for preparing microcapsules. Compared to traditional surfactant-stabilized emulsions, Pickering emulsions utilize only solid particles to stabilize the oil-water interface. This method offers significant advantages in terms of environmental impact and stability, leading to its widespread application in industries such as food, pharmaceuticals, and cosmetics. Common solid particles include inorganic particles (such as silica, clay, and magnetic nanoparticles), synthetic polymers, and biomass particles.

[0004] Montmorillonite (MMT) is a 2:1 layered silicate clay whose interlayer spacing is easily exfoliated by external forces, forming nano-montmorillonite of varying thickness and diameter. Natural MMT is highly hydrophilic and cannot adsorb at the oil-water interface to form a stable emulsion. Organic modification of montmorillonite uses potentially toxic substances and is expensive to manufacture. Summary of the Invention

[0005] In order to improve the application efficiency of traditional pesticides, reduce pesticide residues and production costs, and reduce environmental pollution, the present invention provides the following technical solutions.

[0006] In a first aspect, the present invention provides a montmorillonite-based pesticide microcapsule suspension, wherein the pesticide microcapsule suspension is prepared from the following raw materials in the following weight ratios:

[0007] Preferably, the ratio of pesticide: organic solvent: isophorone diisocyanate: dibutyltin dilaurate: montmorillonite: water is 5-10: 0-10: 0.5-2: 0.025-0.1: 8-12: 300-500.

[0008] Preferably, the pesticide:organic solvent:isophorone diisocyanate:dibutyltin dilaurate:montmorillonite:water comprises: 5:5:0.5:0.025:8:300, 5:5:0.5:0.025:10:490, 5:5:1:0.05:10:450, 5:5:1:0.05:10:490, 5:5:2:0.1:10:490, 5:5:2:0.1:12:400, 10:0:1:0.05:10:490, 5:10:2:0.1:10:490 or 5:10:2:0.1:12:500.

[0009] Preferably, the montmorillonite is mechanically modified.

[0010] Furthermore, the particle size of the montmorillonite is ≤1000 nm, for example: 200 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 747.5 nm, 800 nm, 1000 nm.

[0011] Preferably, the montmorillonite is selected from any one of calcium-based montmorillonite, sodium-based montmorillonite, sodium-calcium-based montmorillonite, and magnesium-based montmorillonite, or a combination of two or more thereof.

[0012] Preferably, the pesticide is selected from any one or a combination of two or more of pyrethroid pesticides, strobilurin pesticides or avermectin pesticides.

[0013] Furthermore, the pyrethroid pesticides include but are not limited to permethrin, tetramethrin, cypermethrin, cyfluthrin, cypermethrin, etofenprox, tefluthrin, flutothrin or beta-cyfluthrin.

[0014] Furthermore, the strobilurin pesticides include but are not limited to azoxystrobin, kresoxim-methyl, diastereoisomer-methyl, pyraclostrobin, trifloxystrobin, flutostrobin or picoxystrobin.

[0015] Furthermore, the avermectin pesticides include but are not limited to avermectin, emamectin benzoate, ivermectin, abamectin or seramectin.

[0016] Preferably, the organic solvent is selected from any one or a combination of two or more of butyl stearate, cinnamaldehyde, tetradecane or octadecane.

[0017] Preferably, the particle size of the pesticide microcapsule is ≤3000 nm, for example: 600 nm, 682 nm, 746 nm, 800 nm, 865 nm, 1000 nm, 1200 nm, 1400 nm, 1560 nm, 1800 nm, 1845 nm, 1900 nm, 2000 nm, 2200 nm, 2500 nm, 2700 nm, 3000 nm.

[0018] In a second aspect, the present invention provides a method for preparing a montmorillonite-based pesticide microcapsule suspension, the preparation method comprising the following steps:

[0019] (1) Melting the pesticide, then adding isophorone diisocyanate and dibutyltin dilaurate, and mixing them evenly to obtain an oil phase;

[0020] (2) Adding montmorillonite to water, shearing, homogenizing, and diluting to obtain an aqueous phase;

[0021] (3) The aqueous phase is added to the oil phase, and the mixture is sheared, averaged, solidified, and cooled to obtain the pesticide microcapsule suspension.

[0022] Preferably, the weight ratio of the raw materials is: pesticide: organic solvent: isophorone diisocyanate: dibutyltin dilaurate: montmorillonite: water = 5-10: 0-10: 0.5-2: 0.025-0.1: 8-12: 300-500.

[0023] Furthermore, the pesticide: organic solvent: isophorone diisocyanate: dibutyltin dilaurate: montmorillonite: water includes: 5:5:0.5:0.025:8:300, 5:5:0.5:0.025:10:490, 5:5:1:0.05:10:450, 5:5:1:0.05:10:490, 5:5:2:0.1:10:490, 5:5:2:0.1:12:400, 10:0:1:0.05:10:490, 5:10:2:0.1:10:490 or 5:10:2:0.1:12:500.

[0024] Preferably, in step (1), the melting temperature of the pesticide is 55-85°C, for example: 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C.

[0025] Furthermore, when the melting point of the pesticide is less than the melting temperature of the pesticide, the pesticide is first mixed with an organic solvent and then melted; when the melting point of the pesticide is greater than or equal to the melting temperature of the pesticide, the pesticide is directly melted.

[0026] Preferably, in step (2) and step (3), the shearing rotation speed is 10000-13000 rpm, for example: 10000 rpm, 11000 rpm, 12000 rpm, 13000 rpm.

[0027] Preferably, the shearing time is 1 to 3 min, for example: 1 min, 1.5 min, 2 min, 2.5 min, 3 min.

[0028] Preferably, in step (2) and step (3), the mean pressure is 300-600 bar, for example, 300 bar, 400 bar, 500 bar, 600 bar.

[0029] Preferably, the homogenization flow rate is 40-60 mL / min, for example: 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min, 60 mL / min.

[0030] Preferably, the homogenization time is 5 to 15 min, for example: 5 min, 7 min, 10 min, 13 min, 15 min.

[0031] Preferably, in step (3), the stirring speed of the curing is 200-500 rpm, for example: 200 rpm, 300 rpm, 400 rpm, 500 rpm.

[0032] Preferably, the curing time is 4 to 8 hours, for example: 4 hours, 5 hours, 6 hours, 7 hours, 8 hours.

[0033] In a third aspect, the present invention provides use of the pesticide microcapsule suspension according to the first aspect in preventing and controlling plant diseases.

[0034] Preferably, the plant diseases include Pieris rapae, Plutella xylostella, Helicoverpa armigera, Rice blast fungus, Botrytis cinerea, or Fusarium graminearum.

[0035] Furthermore, the plant disease is rice blast or gray mold.

[0036] Beneficial effects of the present invention:

[0037] First, the present invention transforms montmorillonite into nano-montmorillonite through mechanical modification alone, enhancing its emulsifying ability without chemical modification. This simple, low-cost method avoids the high costs and environmental impacts of chemical modification, expanding the application of montmorillonite in pesticide microencapsulation.

[0038] 2. The present invention combines emulsification and interfacial polymerization using Pickering emulsion as a template to produce a pesticide microcapsule suspension that has sustained release, high safety, and good efficacy.

[0039] 3. The present invention does not add surfactants and emulsifiers, thus avoiding the impact of surfactants and emulsifiers on drug efficacy and the environment, reducing preparation costs, and providing a solid technical foundation for the development of sustainable, environmentally friendly and highly efficient new pesticides. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Shown is an image of the average particle size of nano-montmorillonite;

[0041] Figure 2 Shown are scanning electron microscope images of pyraclostrobin pesticide microcapsules, A represents pyraclostrobin microcapsule suspension concentrate sample 1, B represents pyraclostrobin microcapsule suspension concentrate sample 2, and C represents pyraclostrobin microcapsule suspension concentrate sample 3;

[0042] Figure 3 Shown are transmission electron microscope images of pyraclostrobin pesticide microcapsules, A represents pyraclostrobin microcapsule suspension sample 1, B represents pyraclostrobin microcapsule suspension sample 2, and C represents pyraclostrobin microcapsule suspension sample 3;

[0043] Figure 4 Shown are the release curves of pyraclostrobin pesticide microcapsules at different temperatures;

[0044] Figure 5 The figure shows the particle size change curves of pyraclostrobin microcapsules at different temperatures;

[0045] Figure 6 Shown is the inhibition rate of pyraclostrobin microcapsules against gray mold. DETAILED DESCRIPTION

[0046] The technical solution of the present invention will be further described below in conjunction with the embodiments and drawings, and the advantages and features of the present invention will become clearer as the description proceeds. However, it should be understood that the embodiments are merely illustrative and do not limit the scope of the present invention.

[0047] It should be noted that, unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art.

[0048] Example 1 Preparation and characterization of nano-montmorillonite

[0049] 1.1 Disperse 10 g of montmorillonite (Aladdin) in 190 g of pure water and mix thoroughly to obtain a 2% wt% montmorillonite suspension. Shear the suspension at 10,000 rpm for 2 minutes using a high-speed shear. Transfer the suspension to a high-pressure homogenizer and homogenize at a flow rate of 50 mL / min at 500 bar for 10 minutes to form a modified nano-montmorillonite suspension.

[0050] 1.2 The nano-montmorillonite suspension before and after modification was diluted 100 times with pure water, dispersed evenly by ultrasonication, and the particle size was measured by Malvern particle size analyzer.

[0051] like Figure 1 As shown in the figure, after shearing and homogenization, the montmorillonite was exfoliated and the particle size decreased from 1903.7±234.0 nm to 747.5±14.5 nm.

[0052] Example 2 Preparation of Pyraclostrobin Microcapsule Suspension Sample 1

[0053] 2.1 Weigh 5 g of pyraclostrobin and 5 g of butyl stearate, melt them at 60°C, add 0.5 g of isophorone diisocyanate and 0.025 g of dibutyltin dilaurate, and mix well to obtain an oil phase.

[0054] 2.2 Stir the 2% modified montmorillonite suspension prepared in 1.1 in a 60°C water bath for 30 min and obtain the aqueous phase after uniform dispersion.

[0055] 2.3 At 60°C, the aqueous phase was poured into the oil phase and high-speed sheared at 10,000 rpm for 2 minutes to obtain a milky white colostrum. The colostrum was circulated and homogenized for 5 minutes at a pressure of 500 bar and a flow rate of 50 mL / min. The emulsion was then stirred and solidified at 60°C and 300 rpm for 6 hours. After cooling to room temperature, a pyraclostrobin microcapsule suspension sample 1 with a particle size of 682 nm was obtained.

[0056] Example 3 Preparation of Pyraclostrobin Capsule Suspension Sample 2

[0057] The specific preparation process was the same as that of Example 2, except that 1 g of isophorone diisocyanate and 0.05 g of dibutyltin dilaurate were used to obtain a pyraclostrobin microcapsule suspension sample 2 having a particle size of 746 nm.

[0058] Example 4 Preparation of Pyraclostrobin Microcapsule Suspension Sample 3

[0059] The specific preparation process was the same as in Example 2, except that 2 g of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate were used to obtain a pyraclostrobin microcapsule suspension sample 3 having a particle size of 865 nm.

[0060] Example 5 Preparation of Beta-cyfluthrin Microcapsule Suspension Sample

[0061] 5.1 Weigh 10 g of lambda-cyfluthrin and melt it at 60°C. Add 1 g of isophorone diisocyanate and 0.05 g of dibutyltin dilaurate and mix thoroughly to obtain an oil phase.

[0062] 5.2 Stir the 2% modified montmorillonite suspension prepared in 1.1 in a 60°C water bath for 30 min and obtain the aqueous phase after uniform dispersion.

[0063] 5.3 At 60°C, the aqueous phase was poured into the oil phase and high-speed sheared at 10,000 rpm for 2 minutes to produce a milky white colostrum. The colostrum was then circulated and homogenized at a pressure of 500 bar and a flow rate of 50 mL / min for 10 minutes. The emulsion was then stirred and solidified at 60°C and 300 rpm for 8 hours. The mixture was then cooled to room temperature to produce a beta-cyfluthrin microcapsule suspension sample with a particle size of 1560 nm.

[0064] Example 6 Preparation of Avermectin Microcapsule Suspension Sample

[0065] 6.1 Weigh 5 g of avermectin and 10 g of cinnamaldehyde, melt them at 80°C, then add 2 g of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate, and mix well to obtain an oil phase.

[0066] 6.2 Stir the 2% modified montmorillonite suspension prepared in 1.1 in a 60°C water bath for 30 min and obtain the aqueous phase after uniform dispersion.

[0067] 6.3 At 60°C, the aqueous phase was poured into the oil phase and high-speed sheared at 10,000 rpm for 2 minutes to produce a milky white colostrum. The colostrum was then circulated and homogenized at a pressure of 500 bar and a flow rate of 50 mL / min for 10 minutes. The emulsion was then stirred and solidified at 60°C and 300 rpm for 6 hours. The mixture was then cooled to room temperature to produce a microcapsule suspension of ethotripsy with a particle size of 1845 nm.

[0068] Example 7 Performance Determination of Microcapsule Suspension Samples

[0069] 7.1 Morphology Observation of Microcapsule Suspension

[0070] 7.1.1 Take the microcapsule suspension samples prepared in Examples 2 to 4, dilute them 100-fold with deionized water, and evenly disperse them. Take 10 μL of the sample and spot it on a silicon wafer. After air drying, observe the morphology of the microcapsule suspension samples using a scanning electron microscope ( Figure 2 ).

[0071] 7.1.2 Take 5 μL of the diluted suspension and spot it on a copper grid. After drying naturally, use a transmission electron microscope to observe the three-dimensional morphology of the microcapsules ( Figure 3 ).

[0072] like Figure 2 and Figure 3 As shown in the figure, the microcapsules are spherical with diameters ranging from 600 nm to 1500 nm.

[0073] 7.2 Release performance test of microcapsule suspension

[0074] 5 mL of pyraclostrobin microcapsule suspension sample 3 (2 mg / mL pyraclostrobin) was placed in a dialysis bag (MWCO: 3500 Da) and immersed in 95 mL of 40% acetonitrile-water solution. The solution was shaken at 35°C, 25°C, and 10°C. 1 mL of the external acetonitrile-water solution was collected at 1, 3, 6, 9, 12, 24, 36, 48, and 72 h, and 1 mL of fresh acetonitrile-water solution was added. The pyraclostrobin concentration in the samples was analyzed by high-performance liquid chromatography (HPLC). A commercial pyraclostrobin suspension (2 mg / mL pyraclostrobin) at 25°C was used as a control. The cumulative release was calculated, and a cumulative release curve was plotted.

[0075] like Figure 4 As shown, the release rate of pyraclostrobin from the microcapsules gradually slows over time. At 25°C, only 36.9% is released in 72 hours. Furthermore, the release rate increases with increasing temperature, thanks to the phase change material butyl stearate. This demonstrates that the microcapsules of the present invention are not only temperature-responsive but also exhibit a sustained-release effect, extending the pesticide's shelf life and reducing its acute effects.

[0076] 7.3 Storage stability test of microcapsule suspension

[0077] The pyraclostrobin microcapsule suspension sample 3 was placed at 4°C, 25°C and 54°C, and the particle size was measured using a Malvern particle size analyzer on the 1st, 7th and 14th day. Figure 5 .

[0078] Depend on Figure 5 It can be seen that under different temperature conditions, the pyraclostrobin microcapsule suspension maintains excellent stability and the particle size does not change significantly, indicating that the pyraclostrobin microcapsule suspension prepared by the present invention has strong adaptability to ambient temperature, a wide storage temperature range, and high storage stability.

[0079] 7.4 In vivo antifungal assay

[0080] The mycelial growth inhibition method was used to investigate the fungicidal activities of commercially available pyraclostrobin suspension concentrate (SC), Seltima, and pyraclostrobin microcapsule suspension concentrate sample 3 (M) against rice blast fungus.

[0081] Magnaporthe oryzae disks (5.2 mm) were placed on potato dextrose agar containing the indicated concentrations (0.005 mg / L, 0.05 mg / L, 0.1 mg / L, and 0.5 mg / L) of pyraclostrobin. After 14 days of incubation at 28°C in the dark, the average diameter of radial mycelial growth was measured using the intersection method. The EC value of pyraclostrobin against Magnaporthe oryzae was calculated. 50 Deionized water was used as a blank control, and three replicates were set for each experiment.

[0082] Table 1 Test results of anti-particle activity of microcapsule suspension concentrate, rice clear and commercial suspension concentrate against rice blast fungus

[0083]

[0084] As can be seen from Table 1, the commercial suspension has a higher antibacterial activity. This is because the commercial suspension releases quickly and can contact the rice blast fungus at an early stage to inhibit its growth. However, due to the slow release ability of the microcapsule suspension and rice clear, its antibacterial activity is reduced. However, the EC of the pyraclostrobin suspension prepared by the present invention against the rice blast fungus is 50 The antibacterial activity of the microcapsule suspension prepared by the present invention is 0.034 μg / mL, which is 1.8 times that of Daoqing.

[0085] 7.5 In vitro antifungal assay

[0086] Four-week-old cucumber leaves of similar size were placed on Petri dishes containing 2% agar and sprayed with an aqueous solution of pyraclostrobin microcapsule suspension concentrate sample 3, Daoqing, and a commercially available pyraclostrobin suspension concentrate (containing 100 mg / L). Each leaf was sprayed with 1 mL of water. Water served as a blank control. After the leaves dried, they were pierced with a toothpick and inoculated with a 7 mm disk of Botrytis cinerea. The Petri dishes were sealed and incubated in a climate-controlled incubator at 25°C with a 16 h / 8 h light / dark cycle for 5 days. The diameters of lesions on the leaves were then measured in two perpendicular directions, and the Botrytis cinerea inhibition rate was calculated using the following formula.

[0087] Inhibition rate = (control diameter - initial diameter) / (blank diameter - initial diameter) × 100%

[0088] like Figure 6 As shown, there is no significant difference in the inhibition rate of gray mold between microcapsule suspension sample 3 and Daoqing, indicating that the microcapsule suspension prepared by the present invention can effectively inhibit gray mold and can be used for the prevention and control of plant gray mold disease.

[0089] 7.6 Comparative Analysis of Zebrafish Toxicity of Microcapsule Suspension

[0090] The toxicity of pyraclostrobin microcapsules, sample 3, to zebrafish was evaluated using a static method. Commercially available pyraclostrobin suspension concentrates and rice slurry were used as controls. The three pesticide formulations (based on pyraclostrobin content) were diluted to varying concentrations using tap water that had been filtered for 24 hours. Ten randomly selected zebrafish (2-3 cm in length) were then exposed to the solutions. Tap water served as a blank control. Each treatment was replicated three times. Mortality was recorded after 96 hours of exposure.

[0091] Table 2 Zebrafish toxicity test results of microcapsule suspension, Daoqing and commercial suspension

[0092]

[0093] As can be seen from Table 2, after zebrafish were exposed to the pesticide formulation for 96 hours, the LC values ​​of microcapsule suspension concentrate, rice clearing concentrate and commercial suspension concentrate were 50 The concentrations of pyraclostrobin in the microcapsules were 0.49 μg / mL, 0.37 μg / mL, and 0.095 μg / mL, respectively, indicating that microencapsulation of pyraclostrobin significantly reduced its toxicity. The pyraclostrobin microcapsule suspension prepared by the present invention has low toxicity and is environmentally friendly.

[0094] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

Claims

1. A pesticide microcapsule suspension based on montmorillonite, characterized in that: The pesticide microcapsule suspension is prepared from the following raw materials in the following weight ratios: Pesticide: organic solvent: isophorone diisocyanate: dibutyltin dilaurate: montmorillonite: water = 5~10: 0~10: 0.5~2: 0.025~0.1: 8~12: 300~500; The preparation method of the pesticide microcapsule suspension comprises the following steps: (1) The pesticide is mixed with an organic solvent and dissolved, and then isophorone diisocyanate and dibutyltin dilaurate are added and mixed evenly to obtain an oil phase; (2) Adding montmorillonite to water, shearing, homogenizing, and diluting to obtain an aqueous phase; (3) adding the aqueous phase to the oil phase, and subjecting the mixture to shearing, homogenization, solidification, and cooling to obtain the pesticide microcapsule suspension; The pesticide is pyraclostrobin; The organic solvent is selected from any one or a combination of two or more of butyl stearate, cinnamaldehyde, tetradecane or octadecane; The particle size of the montmorillonite after shearing and homogenization is ≤1000 nm.

2. The pesticide microcapsule suspension according to claim 1, wherein The montmorillonite is selected from any one of calcium-based montmorillonite, sodium-based montmorillonite, sodium-calcium-based montmorillonite, and magnesium-based montmorillonite, or a combination of two or more thereof.

3. The pesticide microcapsule suspension according to claim 1, wherein The particle size of the pesticide microcapsule is ≤3000 nm.

4. A method for preparing a pesticide microcapsule suspension based on montmorillonite according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Mixing the pesticide organic solvent and dissolving it, then adding isophorone diisocyanate and dibutyltin dilaurate, and mixing them evenly to obtain an oil phase; (2) Adding montmorillonite to water, shearing, homogenizing, and diluting to obtain an aqueous phase; (3) The aqueous phase is added to the oil phase, and the mixture is sheared, homogenized, solidified, and cooled to obtain the pesticide microcapsule suspension.

5. The preparation method according to claim 4, characterized in that In step (1), the melting temperature of the pesticide is 55-85°C.

6. Use of the pesticide microcapsule suspension according to any one of claims 1 to 3 in preventing and controlling plant diseases, wherein the plant diseases are plant diseases caused by rice blast, gray mold or Fusarium graminearum.

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