Montmorillonite-based pesticide microcapsule suspending agent as well as preparation method and application thereof

Abstract

The invention discloses a montmorillonite-based pesticide microcapsule suspending agent as well as a preparation method and application thereof. The pesticide microcapsule suspending agent is prepared from a pesticide, an organic solvent, isophorone diisocyanate, dibutyltin dilaurate, montmorillonite and water according to a weight ratio of (5-10): (0-10): (0.5-2): (0.025-0.1): (8-12): (300-500) by taking Pickering emulsion as a template and adopting a process combining an emulsification technology and an interfacial polymerization technology. The pesticide microcapsule disclosed by the invention is low in preparation cost, capable of realizing slow release, high in safety and good in application pesticide effect, and a solid technical foundation is provided for development of sustainable, environment-friendly and efficient novel pesticides.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide preparations, and in particular 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 preventing and controlling pests and diseases and increasing crop yields. Conventional pesticide formulations include emulsifiable concentrates, microemulsions, suspensions, and powders. However, due to low efficiency, less than 30% of the active ingredients act on the target organisms, while the rest enter the surrounding natural environment, resulting in huge 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, and their benefits include controlled release of 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 with traditional emulsions stabilized by surfactants, Pickering emulsions only use solid particles to stabilize the oil-water interface, which has significant advantages in terms of environmental impact and stability. It is widely used 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 type of layered silicate clay, whose interlayer spacing is easily peeled off by external forces, forming nano-montmorillonite of different thicknesses and diameters. Natural MMT is highly hydrophilic and cannot be adsorbed at the oil-water interface to form a stable emulsion. Organic modification of montmorillonite uses substances that are potentially toxic and 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 pesticide microcapsule suspension based on montmorillonite, wherein the pesticide microcapsule suspension is prepared from the following raw materials in a weight ratio; 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.

[0007] 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.

[0008] Preferably, the montmorillonite is mechanically modified.

[0009] 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.

[0010] 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.

[0011] Preferably, the pesticide is selected from any one or a combination of two or more of pyrethroid pesticides, strobilurin pesticides or avermectin pesticides.

[0012] Furthermore, the pyrethroid pesticides include but are not limited to permethrin, tetramethrin, cypermethrin, cyfluthrin, cypermethrin, ethomethrin, tefluthrin, fluthrin or high-efficiency fluthrin.

[0013] Furthermore, the strobilurin pesticides include but are not limited to azoxystrobin, kresoxim-methyl, kresoxim-methyl, pyraclostrobin, trifloxystrobin, fluazifop-butyl or picoxystrobin.

[0014] Furthermore, the avermectin pesticides include but are not limited to avermectin, emamectin benzoate, ivermectin, abamectin or seratomectin.

[0015] Preferably, the organic solvent is selected from any one or a combination of two or more of butyl stearate, cinnamaldehyde, tetradecane or octadecane.

[0016] 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.

[0017] 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: (1) Melting the pesticide, then adding isophorone diisocyanate and dibutyltin dilaurate, and mixing 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 subjected to shearing, averaging, solidification, and cooling to obtain the pesticide microcapsule suspension.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] Preferably, the shearing time is 1 to 3 min, for example: 1 min, 1.5 min, 2 min, 2.5 min, 3 min.

[0024] Preferably, in step (2) and step (3), the mean pressure is 300-600 bar, for example, 300 bar, 400 bar, 500 bar, 600 bar.

[0025] 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.

[0026] Preferably, the homogenization time is 5 to 15 min, for example: 5 min, 7 min, 10 min, 13 min, 15 min.

[0027] Preferably, in step (3), the stirring speed of the curing is 200-500 rpm, for example: 200 rpm, 300 rpm, 400 rpm, 500 rpm.

[0028] Preferably, the curing time is 4 to 8 h, for example: 4 h, 5 h, 6 h, 7 h, 8 h.

[0029] In a third aspect, the present invention provides use of the pesticide microcapsule suspension described in the first aspect in preventing and controlling plant diseases.

[0030] Preferably, the plant diseases include Pieris rapae, Plutella xylostella, Helicoverpa armigera, Rice blast, Botrytis cinerea, or Fusarium graminearum.

[0031] Furthermore, the plant disease is rice blast or gray mold.

[0032] Beneficial effects of the present invention: 1. The present invention converts montmorillonite into nano-montmorillonite only by mechanical modification, and can enhance its emulsification ability without chemical modification. The operation is simple and low in cost, avoiding the high cost and environmental impact caused by chemical modification, and expanding the application of montmorillonite in pesticide microcapsules.

[0033] 2. The present invention combines emulsification and interfacial polymerization using Pickering emulsion as a template, and the obtained pesticide microcapsule suspension has sustained release, high safety, and good application efficacy.

[0034] 3. The present invention does not add surfactants and emulsifiers, thus avoiding the impact of surfactants and emulsifiers on 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

[0035] Figure 1 Shown is an image of the average particle size of nano-montmorillonite; Figure 2 The images are scanning 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; 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; Figure 4 Shown is the release curve of pyraclostrobin pesticide microcapsules at different temperatures; Figure 5 The figure shows the particle size change curve of pyraclostrobin microcapsules at different temperatures; Figure 6 Shown is the inhibition rate of pyraclostrobin microcapsules against Botrytis cinerea. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with the embodiments and drawings, and the advantages and features of the present invention will become clearer with the description. However, it should be understood that the embodiments are only exemplary and do not limit the scope of the present invention.

[0037] It should be noted that the experimental methods used in the following examples are conventional methods in the art unless otherwise specified.

[0038] Example 1 Preparation and characterization of nano-montmorillonite

[0039] 1.1 Disperse 10 g of montmorillonite (Aladdin) in 190 g of pure water and mix to obtain a 2%wt% montmorillonite suspension. Then use a high-speed shearing machine to shear at 10,000 rpm for 2 min. Then transfer the suspension to a high-pressure homogenizer and homogenize at a flow rate of 50 mL / min at 500 bar for 10 min to form a modified nano-montmorillonite suspension.

[0040] 1.2 The nano-montmorillonite suspension before and after modification was diluted 100 times with pure water, and after being evenly dispersed by ultrasonic, the particle size was measured by Malvern particle size analyzer.

[0041] like Figure 1 As shown, after shearing and homogenization, montmorillonite was exfoliated and the particle size decreased from 1903.7±234.0 nm to 747.5±14.5 nm.

[0042] Example 2 Preparation of pyraclostrobin microcapsule suspension sample 1

[0043] 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.

[0044] 2.2 Stir the 2% modified montmorillonite suspension prepared in 1.1 in a 60°C water bath for 30 min to obtain an aqueous phase after it is evenly dispersed.

[0045] 2.3 At 60°C, the aqueous phase was poured into the oil phase and high-speed sheared at 10,000 rpm for 2 min to obtain milky colostrum. The colostrum was circulated and homogenized for 5 min at a pressure of 500 bar and a flow rate of 50 mL / min. The double emulsion solution was then stirred and solidified at 60°C and 300 rpm for 6 h, and cooled to room temperature to obtain a pyraclostrobin microcapsule suspension sample 1 with a particle size of 682 nm.

[0046] Example 3 Preparation of pyraclostrobin capsule suspension sample 2

[0047] The specific preparation process is the same as that of Example 2, except that the amount of isophorone diisocyanate is 1 g and the amount of dibutyltin dilaurate is 0.05 g. A pyraclostrobin microcapsule suspension sample 2 with a particle size of 746 nm is obtained.

[0048] Example 4 Preparation of pyraclostrobin microcapsule suspension sample 3

[0049] The specific preparation process is the same as that of Example 2, except that the amount of isophorone diisocyanate is 2 g and the amount of dibutyltin dilaurate is 0.1 g. A pyraclostrobin microcapsule suspension sample 3 with a particle size of 865 nm is obtained.

[0050] Example 5 Preparation of High-efficiency Cyfluthrin Microcapsule Suspension Sample

[0051] 5.1 Weigh 10 g of highly effective cyfluthrin, melt it at 60°C, add 1 g of isophorone diisocyanate and 0.05 g of dibutyltin dilaurate, and mix well to obtain an oil phase.

[0052] 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 it is evenly dispersed.

[0053] 5.3 At 60°C, pour the aqueous phase into the oil phase and high-speed shear at 10,000 rpm for 2 min to obtain milky colostrum. Then circulate and homogenize the colostrum at a pressure of 500 bar and a flow rate of 50 mL / min for 10 min. Then, stir and solidify the emulsion solution at 60°C and 300 rpm for 8 h, cool it to room temperature, and obtain a highly effective cypermethrin microcapsule suspension sample with a particle size of 1560 nm.

[0054] Example 6 Preparation of Avermectin Microcapsule Suspension Sample

[0055] 6.1 Weigh 5 g of avermectin and 10 g of cinnamaldehyde, melt them at 80°C, add 2 g of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate, and mix well to obtain an oil phase.

[0056] 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 it is evenly dispersed.

[0057] 6.3 At 60°C, pour the aqueous phase into the oil phase and high-speed shear at 10,000 rpm for 2 min to obtain milky colostrum. Then circulate and homogenize the colostrum at a pressure of 500 bar and a flow rate of 50 mL / min for 10 min. Then, stir and solidify the emulsion solution at 60°C and 300 rpm for 6 h, and cool to room temperature to obtain a microcapsule suspension sample of ethoxyfen with a particle size of 1845 nm.

[0058] Example 7 Performance Determination of Microcapsule Suspension Samples

[0059] 7.1 Observation of the morphology of microcapsule suspension 7.1.1 Take the microcapsule suspension samples prepared in Examples 2 to 4, dilute them 100 times with deionized water, and after evenly dispersing, take 10 μL and spot them on a silicon wafer. After drying naturally, use a scanning electron microscope to observe the morphological characteristics of the microcapsule suspension samples ( Figure 2 ).

[0060] 7.1.2 Take 5 μL of the diluted suspension and spot it on a copper grid. After it is dried naturally, use a transmission electron microscope to observe the three-dimensional morphology of the microcapsules ( Figure 3 ).

[0061] like Figure 2 and Figure 3 As shown, the microcapsules are spherical with diameters ranging from 600nm to 1500nm.

[0062] 7.2 Release performance test of microcapsule suspension 5 mL of pyraclostrobin microcapsule suspension sample 3 solution (pyraclostrobin content of 2 mg / mL) was placed in a dialysis bag (MWCO: 3500 Da), immersed in 95 mL of 40% acetonitrile aqueous solution, and shaken at 35°C, 25 °C, and 10°C, respectively. 1 mL of external acetonitrile aqueous solution was collected at 1 h, 3 h, 6 h, 9 h, 12 h, 24 h, 36 h, 48 h, and 72 h, and 1 mL of fresh acetonitrile aqueous solution was added. The concentration of pyraclostrobin in the sample was analyzed by high performance liquid chromatography, and a commercial pyraclostrobin suspension (pyraclostrobin content of 2 mg / mL) was used as a control at 25°C. The cumulative release amount was calculated and the cumulative release curve was drawn.

[0063] like Figure 4 As shown in the figure, the release rate of pyraclostrobin in the microcapsule gradually slows down over time. Only 36.9% is released in 72 hours at 25°C. In addition, the release rate becomes faster as the temperature rises, which is due to the phase change material butyl stearate. This shows that the microcapsule of the present invention not only has temperature response, but also has a sustained release effect, which prolongs the shelf life of the pesticide and reduces the acute effect of the pesticide.

[0064] 7.3 Storage stability test of microcapsule suspension 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 sizer on the 1st, 7th and 14th day. Figure 5 .

[0065] 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.

[0066] 7.4 In vivo antifungal assay The mycelium growth inhibition method was used to study the fungicidal activities of commercially available pyraclostrobin suspension concentrate (SC), Seltima and pyraclostrobin microcapsule suspension concentrate sample 3 (M) against Magnaporthe oryzae.

[0067] 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, 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 by 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.

[0068] Table 1 Test results of anti-particle activity of microcapsule suspension, Daoqing and commercial suspension

[0069] As can be seen from Table 1, the commercial suspension has a higher antibacterial activity, which is due to the fast release of the commercial suspension, which can contact the rice blast fungus at an early stage and 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.

[0070] 7.5 In vitro antifungal test Four-week-old cucumber leaves of similar size were selected and placed on a petri dish containing 2% agar. The cucumber leaves were sprayed with an aqueous solution of pyraclostrobin microcapsule suspension sample 3, Daoqing and commercially available pyraclostrobin suspension (containing 100 mg / L of pyraclostrobin). Each cucumber leaf was sprayed with 1 mL, and water was used as a blank control. After the leaves were dried, the cucumber leaves were pierced with a toothpick, and the gray mold disk (7 mm) was inoculated on the cucumber leaves, and the petri dish was sealed. The petri dish was placed in a climate incubator at 25°C with a light / dark cycle of 16 h / 8 h for 5 days. The lesion diameters in two vertical directions on the leaves were then measured, and the gray mold inhibition rate was calculated using the following formula.

[0071] Inhibition rate = (control diameter - initial diameter) / (blank diameter - initial diameter) × 100% like Figure 6 As shown, there is no significant difference in the inhibition rate of Botrytis cinerea between microcapsule suspension sample 3 and Daoqing, indicating that the microcapsule suspension prepared by the present invention can effectively inhibit Botrytis cinerea and can be used for the prevention and control of plant gray mold disease.

[0072] 7.6 Comparative analysis of toxicity of microcapsule suspension to zebrafish The toxicity of pyraclostrobin microcapsule sample 3 to zebrafish was evaluated using the static method, and commercially available pyraclostrobin suspension and rice clear were used as control groups. The three pesticide preparations (based on pyraclostrobin content) were diluted into different concentrations of liquid medicine using tap water after 24 hours of circulation filtration. Ten zebrafish (2-3 cm in length) were randomly selected and placed in the liquid medicine. Tap water was used as a blank control, and each treatment was repeated 3 times. The mortality rate of zebrafish after 96 hours in the liquid medicine was recorded.

[0073] Table 2 Zebrafish toxicity test results of microcapsule suspension, Daoqing and commercial suspension

[0074] As can be seen from Table 2, after zebrafish were exposed to pesticide formulations for 96 hours, the LC values ​​of microcapsule suspension, rice clear and commercial suspension 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 the toxicity of pyraclostrobin was significantly reduced by microencapsulation. The pyraclostrobin microcapsule suspension prepared by the present invention has low toxicity and is environmentally friendly.

[0075] 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, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope 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 weight ratio: Pesticide: organic solvent: isophorone diisocyanate: dibutyltin dilaurate: montmorillonite: water = 5~10: 0~10: 0.5~2: 0.025~0.1: 8~12: 300~500.

2. The pesticide microcapsule suspension according to claim 1, characterized in that: The particle size of the montmorillonite is ≤1000nm.

3. The pesticide microcapsule suspension according to claim 1, characterized in that: 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.

4. The pesticide microcapsule suspension according to claim 1, characterized in that: The pesticide is selected from any one or a combination of two or more of pyrethroid pesticides, strobilurin pesticides or avermectin pesticides.

5. The pesticide microcapsule suspension according to claim 1, characterized in that: The organic solvent is selected from any one or a combination of two or more of butyl stearate, cinnamaldehyde, tetradecane or octadecane.

6. The pesticide microcapsule suspension according to claim 1, characterized in that: The particle size of the pesticide microcapsule is ≤3000 nm.

7. A method for preparing a pesticide microcapsule suspension based on montmorillonite, characterized in that: The preparation method comprises the following steps: (1) Melting the pesticide, then adding isophorone diisocyanate and dibutyltin dilaurate, and mixing 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 subjected to shearing, averaging, solidification, and cooling to obtain the pesticide microcapsule suspension.

8. The preparation method according to claim 7, characterized in that: In step (1), the melting temperature of the pesticide is 55-85°C; 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 ≥ the melting temperature of the pesticide, the pesticide is directly melted.

9. Use of the pesticide microcapsule suspension according to claims 1-6 in preventing and controlling plant diseases.

10. The use according to claim 9, characterized in that: The plant diseases include cabbage looper, diamondback moth, cotton bollworm, rice blast fungus, gray mold or Fusarium graminearum.

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