Preparation and application of prothioconazole sustained-release microspheres for improving leaf surface stability

Abstract

The invention belongs to the technical field of pesticide preparations, and relates to a preparation method and application of prothioconazole sustained-release microspheres. The preparation method comprises the following steps: adding an active compound, an emulsifier, isocyanate and polycaprolactone polyol into cyclohexanone, and uniformly mixing to obtain an oil phase; adding a dispersing agent into water and uniformly mixing to obtain a water phase; and adding dibutyltin dilaurate into the oil phase, reacting, mixing with the water phase, shearing, and stirring to obtain the prothioconazole sustained-release microsphere suspending agent. The prothioconazole sustained-release microsphere prepared by the process still keeps higher bactericidal activity on the premise of good leaf surface stability, so that reduction of the pesticide application frequency, improvement of the pesticide utilization rate and long-acting prevention and control of prothioconazole in the field are expected to be realized, and the prothioconazole sustained-release microsphere conforms to the national double reduction policy and is suitable for large-scale popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide preparations and relates to a preparation method and application of prothioconazole sustained-release microspheres for improving leaf surface stability. Background Art

[0002] Prothioconazole, CAS No.: 178928-70-6, chemical name: 2-[(2RS)-2-(1-chlorocyclopropyl)-3-(2-chlorophenyl)-2-hydroxypropyl]-2,4-dihydro-1,2,4-triazole-3-thione, is a sterol demethylation (ergosterol biosynthesis) inhibitor that can inhibit the 14α-demethylase ( CYP51 ) interferes with or blocks the biosynthesis of ergosterol in the cell membrane, causing the accumulation of toxic sterols and affecting the structure and function of the cell membrane, thereby exerting its antimicrobial effects. It is primarily used to control various diseases (such as powdery mildew, sheath blight, wilt, leaf spot, and rust in wheat; and sclerotinia rot in rapeseed and peanuts, as well as gray mold, black spot, and brown spot) in crops such as wheat, barley, rapeseed, peanuts, rice, legumes, sugar beets, and field vegetables. Prothioconazole has a broader spectrum of fungicidal activity, resulting in effective disease prevention and treatment, and significant yield increases. Furthermore, prothioconazole has low biological and ecotoxicity, making it safe for users, crops, and the environment.

[0003] Microsphere suspension concentrates utilize a cross-linked polymer carrier to hold the active ingredient. This new pesticide formulation extends the active ingredient's longevity by enhancing the carrier's sustained-release properties and foliar resistance (resistance to stresses such as sunlight and rainfall). Existing prothioconazole sustained-release microsphere suspensions lack sufficient foliar stability, and their resistance to UV photolysis, rain washout, and extended release time require further improvement. Summary of the Invention

[0004] Aiming at the problem of low leaf surface stability of traditional prothioconazole slow-release microsphere suspension, the present invention proposes a novel preparation method and application of prothioconazole slow-release microspheres.

[0005] In order to achieve the above object, the present invention is implemented by adopting the following technical solutions: A method for preparing a prothioconazole sustained-release microsphere suspension for improving leaf surface stability comprises the following steps: (1) Add the technical, emulsifier, isocyanate and polycaprolactone polyol to cyclohexanone and mix well to obtain an oil phase.

[0006] (2) Add the dispersant to water and mix well to obtain an aqueous phase.

[0007] (3) Dibutyltin dilaurate is added to the oil phase, mixed with the aqueous phase after reaction, sheared and stirred to obtain prothioconazole sustained-release microsphere suspension.

[0008] Preferably, the technical drug in step (1) is prothioconazole technical drug, the isocyanate is at least one of diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate, the polycaprolactone polyol is at least one of polycaprolactone diol and polycaprolactone triol, the mass ratio of the isocyanate to the polycaprolactone polyol is 5:1-6:5, and the emulsifier is at least one of a nonionic hydroxy polyethylene oxide block copolymer, phenethylphenol polyoxyethylene polyoxypropylene ether, and phenethylphenol polyoxyethylene ether.

[0009] Preferably, in step (1), the mass fraction of the original drug in the oil phase is 1-15%, the sum of the mass fractions of the isocyanate and the polycaprolactone polyol in the oil phase is 5-11%, and the mass fraction of the emulsifier in the oil phase is 0.5-3%.

[0010] Preferably, the dispersant in step (2) is sodium lignin sulfonate, and the mass fraction of the dispersant in the aqueous phase is 2-8%.

[0011] Preferably, in step (3), after adding 0.05-0.1 g of dibutyltin dilaurate, the reaction time is 20-40 s; after mixing with the aqueous phase, shearing is carried out at a speed of 7000-9000 r / min for 2-4 min, and then stirring is carried out at 200-500 rpm for 25-45 min.

[0012] The present invention proposes the use of the prothioconazole sustained-release microsphere suspension prepared by the method in a fungicide.

[0013] Compared with the prior art, the advantages and positive effects of the present invention are: The present invention loads prothioconazole into microspheres. By adjusting the type and ratio of isocyanate and polycaprolactone polyol, the rigidity and flexibility of the prothioconazole sustained-release microspheres are modified, thereby optimizing the microspheres' ability to resist rainwater erosion, release rate, and photolysis rate. The prothioconazole sustained-release microspheres produced by the process of the present invention maintain high bactericidal activity while maintaining good leaf stability. Therefore, it is expected to reduce the number of pesticide applications, improve pesticide utilization, and provide long-term prothioconazole control in the field. This is in line with the national "double reduction" policy and is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Microscope photos.

[0015] Figure 2 The release rate curve.

[0016] Figure 3 This is the retention curve of pesticide components on the leaf surface. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0018] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] Example 1 5 g of prothioconazole (CAS: 178928-70-6, Anhui Jiuyi Agriculture Co., Ltd.), 0.5 g of nonionic hydroxylated polyethylene oxide block copolymer (Guangzhou Zhuocen Chemical Co., Ltd., product model: 500LQ), 3 g of polycaprolactone triol (Hunan Juren New Materials Co., Ltd., product model: PCL3057), and 1.5 g of PM200 (a mixture of isocyanate and diphenylmethane diisocyanate, CAS: 9016-87-9, Wanhua Chemical Group Co., Ltd.) were dissolved in 7.5 g of cyclohexanone (CAS: 108-94-1, Shanghai MacLean Technology Co., Ltd.) to form an oil phase A. 0.05g of dibutyltin dilaurate (catalyst, CAS: 77-58-7, Shanghai Macklin Technology Co., Ltd.) was added to oil phase A and manually stirred for 30 seconds to form oil phase mixture B. 12.5g of sodium lignin sulfonate (CAS: 8061-51-6, degree of sulfonation: 0.8, MeadWestvaco (China) Investment Co., Ltd.) was dissolved in 20g of deionized water to form an aqueous phase. This oil phase mixture B was poured into the aqueous phase and sheared at 8000 rpm for 3 minutes at room temperature to form microspheres. The mixture was then stirred at 300 rpm using a magnetic stirrer for 30 minutes at room temperature to obtain a prothioconazole sustained-release microsphere suspension. Testing showed that the encapsulation efficiency of the prothioconazole microspheres prepared in this example was 96%, meeting the formulation requirements.

[0020] The prothioconazole sustained-release microsphere suspension prepared in this example and the following examples can be directly diluted with water for spraying. If not used for an extended period, it should be sealed and stored. Before use, shake it manually and then dilute it with deionized water or tap water to the appropriate concentration. Testing showed that the prothioconazole sustained-release microsphere suspension prepared in this example showed no significant changes in appearance or efficacy after six months of sealed storage.

[0021] Example 2 Unless otherwise specified in this embodiment, the preparation process is the same as that in Example 1.

[0022] 5g of prothioconazole, 0.5g of nonionic hydroxypolyethylene oxide block copolymer 500LQ, 3g of polycaprolactone triol (Hunan Juren New Materials Co., Ltd., model: PCL3057), and 1g of PM200 were dissolved in 7.5g of cyclohexanone to form oil phase A. 0.05g of dibutyltin dilaurate was added to oil phase A and stirred for 30 seconds to form oil phase B. 12.5g of sodium lignin sulfonate was dissolved in 20.5g of water to form an aqueous phase. Oil phase B was poured into the aqueous phase and sheared at 8000 rpm for 3 minutes to form microspheres. The mixture was then stirred on a magnetic stirrer at 300 rpm for 30 minutes to obtain a prothioconazole sustained-release microsphere suspension. Testing showed that the encapsulation efficiency of the prothioconazole microspheres prepared in this example was 92%, meeting the formulation requirements. After sealed storage for 6 months, there was no significant change in their morphology or efficacy.

[0023] Example 3 Unless otherwise specified in this embodiment, the preparation process is the same as that in Example 1.

[0024] 5g of prothioconazole, 0.5g of phenylethylphenol polyoxyethylene polyoxypropylene ether 1602 (Nanjing Jierun Technology Co., Ltd.), 3g of polycaprolactone diol (Hunan Juren New Materials Co., Ltd., model: PCL2053), and 0.75g of PM200 were dissolved in 7.5g of cyclohexanone to form oil phase A. 0.05g of dibutyltin dilaurate was added to oil phase A and stirred for 30 seconds to form oil phase B. 12.5g of sodium lignin sulfonate was added to 20.75g of water and mixed evenly to form an aqueous phase. Oil phase B was poured into the aqueous phase and sheared at 8000 rpm for 3 minutes to form microspheres. The mixture was then stirred on a magnetic stirrer at 300 rpm for 30 minutes to obtain a prothioconazole sustained-release microsphere suspension. Testing showed that the encapsulation efficiency of the prothioconazole microspheres prepared in this example was 90%, meeting the formulation requirements. After sealed storage for 6 months, there was no significant change in their morphology or efficacy.

[0025] Example 4 Unless otherwise specified in this embodiment, the preparation process is the same as that in Example 1.

[0026] 5g of prothioconazole, 0.5g of phenethylphenol polyoxyethylene ether 602 (Beijing Guangyuan Yinong Chemical Co., Ltd.), 3g of polycaprolactone diol (Hunan Juren New Materials Co., Ltd., model: PCL2102), and 0.6g of PM200 were dissolved in 7.5g of cyclohexanone to form oil phase A. 0.05g of dibutyltin dilaurate was added to oil phase A and stirred for 30 seconds to form oil phase B. 12.5g of sodium lignin sulfonate was dissolved in 20.9g of water to form an aqueous phase. Oil phase B was poured into the aqueous phase and sheared at 8000 rpm to form microspheres. The mixture was then stirred on a magnetic stirrer at 300 rpm for 30 minutes to obtain a prothioconazole sustained-release microsphere suspension. Testing showed that the encapsulation efficiency of the prothioconazole microspheres prepared in this example was 90%, meeting the formulation requirements. After six months of sealed storage, there was no significant change in their morphology or efficacy.

[0027] Comparative Example 1 This comparative example differs from Example 1 in that it does not contain isocyanate and polycaprolactone polyol. 5g of prothioconazole and 0.5g of 1600S6 were dissolved in 7.5g of cyclohexanone to form Oil Phase A. 0.05g of dibutyltin dilaurate was added to Oil Phase A and stirred for 30 seconds to form Oil Phase B. 12.5g of sodium lignin sulfonate was dissolved in 20g of water to form an aqueous phase. Oil Phase B was poured into the aqueous phase and sheared at 8000 rpm for 3 minutes. The mixture was then stirred on a magnetic stirrer at 300 rpm for an additional 30 minutes.

[0028] Comparative Example 2 This comparative example differs from Example 1 in that it does not contain isocyanate. The details are as follows: 5g of prothioconazole, 0.5g of 1600S6, and 3g of polycaprolactone triol (Hunan Juren New Materials Co., Ltd., model: PCL3057) were dissolved in 7.5g of cyclohexanone to form oil phase A. 0.05g of dibutyltin dilaurate was added to oil phase A and stirred for 30 seconds to form oil phase B. 12.5g of sodium lignin sulfonate was dissolved in 20g of water to form the aqueous phase. Oil phase B was poured into the aqueous phase and sheared at 8000 rpm. The mixture was then stirred on a magnetic stirrer at 300 rpm for 30 minutes.

[0029] Comparative Example 3 This comparative example differs from Example 1 in that it does not contain polycaprolactone polyol. 5g of prothioconazole, 0.5g of 1600S6, and 1.5g of PM200 were dissolved in 7.5g of cyclohexanone to form Oil Phase A. 0.05g of dibutyltin dilaurate was added to Oil Phase A and stirred for 30 seconds to form Oil Phase B. 12.5g of sodium lignin sulfonate was dissolved in 20g of water to form an aqueous phase. Oil Phase B was poured into the aqueous phase and sheared at 8000 rpm. The mixture was then stirred on a magnetic stirrer at 300 rpm for 30 minutes.

[0030] Performance testing and characterization.

[0031] 1. Microscope photography The prothioconazole sustained-release microsphere suspension obtained in Example 1 and Comparative Example 1 were diluted with 30 times the volume of deionized water and applied to a glass slide for microscopic photography. The results are shown in FIG. Figure 1 As shown, Figure 1 a is a microscope photo of the prothioconazole sustained-release microsphere suspension obtained in Example 1, Figure 1 b is a microscope photo of the prothioconazole sustained-release microsphere suspension obtained in Comparative Example 1, wherein Figure 1 c is a microscopic photograph of the prothioconazole sustained-release microsphere suspension obtained in Example 1 after 30-fold dilution. Figure 1 d is a microscopic photograph of the prothioconazole sustained-release microsphere suspension obtained in Comparative Example 1 after 30-fold dilution. Figure 1 It can be seen that the microspheres prepared in Example 1 are translucent, with clear boundaries and a strong three-dimensional effect; while the microspheres prepared in Comparative Example 1 are exposed emulsion-shaped and no effective microspheres are formed.

[0032] 2. Sustained release performance Weigh 1.00 g of the sample to be tested into a dialysis bag, clamp both ends with clips, and place it in a clean, dry 500 mL wide-mouth glass bottle. Pipette 200 mL of a methanol / water (release medium, 30:70, v / v) mixture into the bottle. Immediately place the bottle on a shaker, roll horizontally at 30 ± 10 rpm, and start a timer. Subsequently, at different time intervals, aspirate 1 mL of the extraction mixture and immediately add the same volume of release medium. The amount of prothioconazole released (At) is measured at different time intervals.

[0033] The measurement process of A0 is as follows: 1.00 g of the microsphere suspension prepared in Example 1 is accurately weighed into a 500 mL glass bottle, and 200 mL of methanol is added. Subsequently, the suspension is sonicated at 100 Hz for 30 min using a high-power liquid crystal ultrasonicator. During this process, the prothioconazole encapsulated in the microcapsules can completely diffuse into the methanol solution. Finally, the extracted mixture in the glass bottle is aspirated and centrifuged at 3000 r / min for 5 min. The upper methanol solution is extracted and the total prothioconazole content is determined by high-performance liquid chromatography. The cumulative release rate is calculated using the following formula: .

[0034] The test results are as follows: The products obtained from the four examples and three comparative examples were subjected to the above release test in sequence. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the release performance of the microspheres is related to the compactness of the microsphere material. The release rates of Examples 1-4 are successively faster, and through actual electron microscopy, it is found that the compactness of the microsphere material is also successively weakened. Therefore, the release rate and the compactness of the material are corresponding. Since Comparative Example 1 does not add any material, the release rate is the fastest. The sustained-release properties of Comparative Examples 2 and 3 are slightly better than Comparative Example 1, but are all worse than those of each embodiment. Therefore, the microspheres prepared by each embodiment and comprising isocyanate and polycaprolactone polyol simultaneously in the process are the best in terms of sustained-release properties.

[0035] 3. Erosion resistance The microsphere suspension from each Example 1 was diluted with deionized water to 1000 mg / L, and organosilicon was added to a mass fraction of 0.01% as a wetting agent. 100 μL of the sample dilution was evenly applied to a glass slide. After natural drying, the slide was subjected to a simulated rainwater washout experiment using a stream of water at a flow rate of 30 mL / min. After washout, the slide was allowed to dry naturally and placed in a 50 mL centrifuge tube. 10 mL of methanol was added to the tube, and the mixture was ultrasonicated for 30 minutes, followed by extraction with oscillation for 30 minutes. 1 mL of the supernatant was then collected and filtered for impurities using a 0.22 μm organic filter membrane. The residual content of prothioconazole on the slide (Mt) was determined using high-performance liquid chromatography. The total content (M0) was calculated as the prothioconazole content remaining on the slide before washout. The prothioconazole washout residual rate was used to calculate the foliar pesticide component retention curve after photolysis. The microsphere suspensions prepared in the remaining examples and comparative examples were replaced, and the above treatments were carried out in sequence. Then, the flushing residual rates of the prothioconazole-loaded microspheres were calculated according to the following formula: .

[0036] The results are as follows Figure 3 As shown, from Figure 3As can be seen, the scour resistance of the microsphere suspensions prepared in Examples 1-4 decreases in descending order, but all are significantly superior to those in Comparative Examples 1-3. This difference is particularly amplified in scenarios with prolonged scours (6-8 minutes). The excellent rainwater resistance of prothioconazole sustained-release microspheres means less drug loss, less environmental impact, and greater environmental friendliness, further aligning with the concept of green and sustainable development.

[0037] 4. Anti-ultraviolet photolysis performance The microsphere suspension prepared in Example 1 was diluted to 1000 mg / L with deionized water, and silicone was added to a mass fraction of 0.01% as a wetting agent. 100 μL of the sample dilution was evenly applied on a glass slide. After natural drying, the glass slide was placed on a radiant with an average intensity of 200 μW / cm 2 Under ultraviolet light, the photolysis behavior of prothioconazole by ultraviolet light was simulated. Samples were taken at different photolysis time points, the slides were taken out and placed in 50mL centrifuge tubes, 10mL of methanol was added to the centrifuge tubes, and after ultrasonication for 30 minutes, the extract was shaken for 30 minutes. Then 1mL of supernatant was taken and impurities were filtered out using a 0.22μm organic filter membrane. The residual content (Mt) of prothioconazole on the glass slide at different photolysis times was determined by high performance liquid chromatography, and the content of prothioconazole remaining on the glass slide when not photolyzed was taken as the total content (M0). The ultraviolet residual rate of prothioconazole was calculated to draw the retention curve of the pesticide components on the leaf after photolysis. The photolysis residual rate of prothioconazole-loaded microspheres was calculated according to the following formula: .

[0038] The results are as follows Figure 3 As shown, from Figure 3 It can be seen that the photolysis rates of Examples 1-4 are significantly slower than those of the comparative examples. The microspheres can better resist ultraviolet degradation during the long-term retention on the leaf surface, reducing the number of applications. This not only reduces the input cost of pesticide chemicals, but also provides a good basis for extending the effective period of the microsphere suspension.

[0039] 5. Antibacterial activity The mycelium growth rate method was used to determine the inhibitory effects of the prothioconazole sustained-release microspheres prepared in Example 3 and Comparative Example 1 on corn leaf blight. A 5 mm bacterial disc was taken from the edge of the corn leaf blight colony (provided by the Fungicide Biology Laboratory of Anhui Agricultural University) using a hole punch and inoculated with the mycelium side facing down in the center of the drug-containing PDA plate using an inoculation needle. The concentration gradient of the drug-containing plate was set to 0 μg / mL, 0.25 μg / mL, 0.5 μg / mL, 1.0 μg / mL, 2 μg / mL and 4 μg / mL. After culturing in the dark at 27°C for 7 days, the diameter of the colony was measured using the cross-cross method (vertical cross method) to calculate the growth inhibition rate of mycelium at different drug concentrations. The calculation was performed using the following formula, and each treatment was repeated 3 times: .

[0040] DPS software was used for analysis. The ordinate (Y) represented the probability value of the inhibition rate, and the abscissa (x) represented the logarithm of the drug mass concentration. The toxicity regression equation Y=bx+a and the correlation coefficient R were obtained to calculate the EC 50 Values and 95% confidence intervals, EC 50 The value refers to the concentration of the agent that can cause 50% inhibition effect on pathogens.

[0041] The EC of the prothioconazole microsphere suspension prepared in Example 3 against corn leaf blight pathogen was tested. 50 is 0.3229, the correlation coefficient R is 0.9705, and the virulence regression equation is Y=5.8789+1.7903X; EC of comparative example 1 against corn leaf blight pathogen 50 The correlation coefficient R is 0.3206, the correlation coefficient R is 0.9643, and the toxicity regression equation is Y=5.8672+1.7556X. Since no microsphere material is added in Comparative Example 1, the prothioconazole is directly exposed, so the short-term control effect is better; the microspheres obtained in Example 3 effectively encapsulate prothioconazole, but the rapid effect on corn leaf blight fungi is very little different from that in Comparative Example 1. Therefore, the prothioconazole sustained-release microsphere suspension proposed in this patent not only has good sustained-release performance, but can also effectively inhibit the growth of corn leaf blight fungi in the short term, achieving the dual effects of long-term sustained release and timely control.

[0042] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a prothioconazole sustained-release microsphere suspension for improving leaf surface stability, characterized in that: The steps are as follows: (1) Add the technical, emulsifier, isocyanate, and polycaprolactone polyol to cyclohexanone and mix them evenly to obtain an oil phase; (2) Add the dispersant to water and mix well to obtain an aqueous phase; (3) Dibutyltin dilaurate is added to the oil phase, mixed with the aqueous phase after reaction, sheared and stirred to obtain prothioconazole sustained-release microsphere suspension.

2. The method for preparing the prothioconazole sustained-release microsphere suspension according to claim 1, wherein: The technical drug in step (1) is prothioconazole technical drug, the isocyanate is at least one of diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate, the polycaprolactone polyol is at least one of polycaprolactone diol and polycaprolactone triol, the mass ratio of the isocyanate to the polycaprolactone polyol is 5:1-6:5, and the emulsifier is at least one of a nonionic hydroxy polyethylene oxide block copolymer, phenethylphenol polyoxyethylene polyoxypropylene ether, and phenethylphenol polyoxyethylene ether.

3. The method for preparing the prothioconazole sustained-release microsphere suspension according to claim 1, wherein: In step (1), the mass fraction of the original drug in the oil phase is 1-15%, the sum of the mass fractions of the isocyanate and the polycaprolactone polyol is 5-11%, and the mass fraction of the emulsifier is 0.5-3%.

4. The method for preparing the prothioconazole sustained-release microsphere suspension according to claim 1, wherein: In step (2), the dispersant is sodium lignin sulfonate, and the mass fraction of the dispersant in the aqueous phase is 2-8%.

5. The method for preparing the prothioconazole sustained-release microsphere suspension according to claim 1, wherein: After adding dibutyltin dilaurate in step (3), the reaction time is 20-40 seconds; after mixing with the water phase, shearing is carried out at a speed of 7000-9000 r / min for 2-4 minutes, and then stirring is carried out at 200-500 rpm for 25-45 minutes.

6. Use of the prothioconazole sustained-release microsphere suspension prepared by the method according to any one of claims 1 to 5 in a fungicide.

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