Mancozeb nanoscale aqueous suspension and preparation method thereof

Abstract

The application relates to a mancozeb nanoscale water suspending agent and a preparation method thereof, and belongs to the technical field of pesticide preparations, and comprises the following steps: uniformly mixing a sodium dimethyldithiocarbamate aqueous solution and an amphiphilic polymer containing a siloxane main chain and a polyether side chain, adding a manganese sulfate aqueous solution to carry out reaction, filtering a reaction product, and washing and filtering a solid-phase product obtained through filtration to obtain pretreated mancozeb raw medicine; adding pretreated mancozeb raw medicine, zinc sulfate, cationic polysaccharide, polyoxyethylene polyoxypropylene block copolymer and an auxiliary agent into water to carry out pre-dispersion, and then carrying out sand milling to obtain the mancozeb nanoscale water suspending agent. The particle size of the water suspending agent prepared by the application is stabilized at about 140-180 nm, and the water suspending agent has good high-low temperature stability, drug efficacy and rainwater scouring resistance.

Description

Technical Field

[0001] This application relates to the field of pesticide formulation technology, and in particular to a mancozeb nanoscale aqueous suspension and its preparation method. Background Technology

[0002] Mancozeb is an excellent protective fungicide, classified as a low-toxicity pesticide. Due to its broad-spectrum bactericidal activity and low susceptibility to resistance, its control effect is significantly superior to other similar fungicides. It also has yield-increasing and protective effects on crops, showing remarkable efficacy in controlling pear scab, apple leaf spot, blight in cucurbits and vegetables, downy mildew, and rust in field crops. Currently, the main formulations sold on the market are 70% and 80% mancozeb wettable powders. Compared to wettable powders, suspension concentrates have advantages such as better environmental compatibility and higher utilization rate of the active ingredient. Most currently developed mancozeb water suspension formulations are ordinary suspensions, meaning the active ingredient particles are typically micron-sized (1-10 μm), dispersed in water using mechanical means such as sand milling. However, the limited specific surface area of ​​micron-sized particles results in a small contact area between the pesticide and pathogens, leading to larger dosages, lower efficacy, and poor resistance to rain washout. In areas with frequent rainfall, repeated applications are necessary, increasing agricultural production costs and environmental burden.

[0003] Furthermore, there is a significant technical bottleneck when grinding mancozeb suspension toward nanoscale particle size: traditional dispersant systems are unable to effectively prevent the aggregation of nanoparticles during the grinding process, and the particle size often cannot be reduced further after reaching the submicron level, resulting in a "grinding limit" phenomenon. Particles are prone to aggregation during high-energy grinding, leading to particle size rebound.

[0004] Therefore, developing a technology for preparing manganese zinc nanoscale aqueous suspensions that can overcome the bottleneck of grinding particle size and solve the problem of particle aggregation during grinding, so as to achieve a larger drug contact area, less drug dosage and higher efficacy, is of great practical significance. Summary of the Invention

[0005] The purpose of this application is to provide a mancozeb nanoscale aqueous suspension and its preparation method. This application aims to overcome the bottleneck of grinding particle size in mancozeb suspensions and solve the technical problem of easy aggregation of nanoparticles during grinding, thereby preparing a nanoscale aqueous suspension and achieving the technical effects of large contact area between the drug and the target, low dosage, and high efficacy during drug administration.

[0006] Firstly, the preparation method of the mancozeb nanoscale aqueous suspension provided in this application adopts the following technical solution: the preparation method includes the following steps: S1. After mixing the sodium mancozeb aqueous solution with the amphiphilic polymer containing the siloxane main chain and polyether side chain evenly, add the manganese sulfate aqueous solution to react. Then, filter the reaction product for the first time, and wash and filter the solid product obtained from the first filtration in sequence. The solid product obtained from the second filtration is the pretreated mancozeb technical. S2. The pretreated mancozeb technical, zinc sulfate, cationic polysaccharide, polyoxyethylene-polyoxypropylene block copolymer and additives prepared in step S1 are added to water for pre-dispersion, and then milled to obtain mancozeb nanoscale aqueous suspension. The additives are selected from one or more of preservatives, wetting agents, defoamers and thickeners.

[0007] Through the above technical solution, the amphiphilic polymer containing a siloxane backbone and polyether side chains participates in the reaction during the mancozeb crystal nucleus growth stage. The hydrophobic siloxane backbone is tightly adsorbed onto the hydrophobic surface of the mancozeb crystal by van der Waals forces, while the hydrophilic polyether side chains extend into the aqueous phase. This adsorption reduces the crystal surface energy, inhibits rapid crystal growth, refines the active pharmaceutical ingredient (API) grains, and makes it easier to grind the API to nanoscale fineness during subsequent grinding, effectively solving the problem of particle aggregation during grinding. During the grinding process in step S2, mechanical force continuously breaks down the surface of the pretreated mancozeb particles, exposing fresh active coordination sites. Simultaneously, zinc ions (from zinc sulfate) in the aqueous phase, under high shear force and nano-sizing, have the opportunity to participate in the coordination structure of mancozeb, which is beneficial for the formation of mancozeb zinc. As the particle size decreases to the nanoscale, the sharp increase in specific surface area provides a sufficient reaction interface for zinc ions, enabling the coordination reaction to proceed efficiently under mild conditions. The polyoxyethylene-polyoxypropylene block copolymer added during the grinding stage exhibits hydrophobic polyoxypropylene (PPO) segments that can hydrophobically associate and hydrogen-bond with the siloxane backbone and polyether side chains of the amphiphilic polymer containing siloxane backbone and polyether side chains. Meanwhile, its hydrophilic polyoxyethylene (PEO) segments extend into the aqueous phase, forming a hydration layer. This hydration layer plays a crucial "buffering" role during grinding, effectively preventing the re-aggregation of newly broken nanoparticles. Simultaneously, the cationic polysaccharide molecular chains entangle with the PEO chains of the polyoxyethylene-polyoxypropylene block copolymer through their polysaccharide backbone, while their positively charged groups primarily face the aqueous phase, forming a positively charged protective layer around the particles. This further inhibits particle aggregation during grinding through electrostatic repulsion. The synergistic effect of the cationic polysaccharide and the polyoxyethylene-polyoxypropylene block copolymer creates a dual protection mechanism of electrostatic repulsion and steric hindrance on the particle surface, breaking through the particle size bottleneck of traditional sand milling methods and achieving nanoscale particle size control. The nanoscale particle size significantly increases the contact area between the drug and the target during administration, thereby reducing the dosage and improving efficacy.

[0008] Optionally, the amphiphilic polymer containing a siloxane backbone and a polyether side chain is a polyether-modified polydimethylsiloxane.

[0009] Through the above technical solution, polyether-modified polydimethylsiloxane combines the low surface tension of organosilicon with the hydrophilicity of polyether, and can form a stable adsorption layer on the surface of manganese crystals. This effectively reduces the frictional heat generated between particles during the grinding process, avoids particle softening and adhesion caused by high temperature, thereby preventing particle aggregation, improving grinding efficiency, and enabling particle size to break through to the nanoscale.

[0010] Further optionally, the hydrophilic-lipophilic balance value of the polyether-modified polydimethylsiloxane is 7 to 9.

[0011] Through the above technical solution, the hydrophilic-lipophilic balance (HLB) value range makes the adsorption of polyether-modified polydimethylsiloxane on the surface of manganese crystal more robust, ensuring both the effective binding of the hydrophobic main chain to the crystal surface and the full extension of the hydrophilic side chain in the aqueous phase. This provides a suitable interfacial environment for the adsorption of dispersant in the subsequent grinding stage, which is beneficial for continuously inhibiting particle polymerization during the grinding process.

[0012] Optionally, the cationic polysaccharide is hydroxypropyltrimethylammonium chloride chitosan (HACC).

[0013] Using the above technical solution, hydroxypropyltrimethylammonium chloride chitosan, as a cationic polymer, is widely used as a flocculant in water treatment, sludge dewatering, and other fields. Its high-density quaternary ammonium positively charged groups on its molecular chain can rapidly flocculate and settle suspended particles through charge neutralization and bridging. Therefore, those skilled in the art generally believe that cationic flocculants such as HACC should be avoided in nano-suspension systems requiring high dispersion, otherwise it will lead to instantaneous system instability and particle aggregation.

[0014] However, experimental results show that when polyether-modified polydimethylsiloxane is introduced in the synthesis stage of mancozeb technical and polyoxyethylene polyoxypropylene ether block copolymer is used in conjunction in the grinding stage, HACC does not cause flocculation instability, but effectively inhibits the polymerization of nanoparticles during the grinding process, becoming a key contributor to breaking through the grinding particle size bottleneck.

[0015] Optionally, the amount of the amphiphilic polymer containing the siloxane main chain and polyether side chain is 2 to 8% of the weight of sodium mancozeb.

[0016] Through the above technical solution, the dosage range ensures that the amphiphilic polymer forms a sufficient adsorption layer on the crystal surface to effectively inhibit crystal nucleus growth, while avoiding excessive coating of the original drug surface due to excessive use. This ensures the effective adsorption of the dispersant during the subsequent grinding process, enabling the grinding to successfully achieve nanoscale fineness.

[0017] In a specific embodiment of step S1, the concentration of the manganese sulfate aqueous solution is 0.8~1.6 mol / L, the reaction temperature is 40~50 ℃, and the dropping rate of the manganese sulfate aqueous solution is 8~15 mL / min.

[0018] Optionally, by weight, the amounts of each component in step S2 are as follows: 30-40 parts of pretreated mancozeb technical grade on a dry basis, 5-10 parts of zinc sulfate, 5-10 parts of cationic polysaccharide, 2-6 parts of polyoxyethylene-polyoxypropylene block copolymer, 1-5 parts of additives, and water to make up to 100 parts.

[0019] Through the above technical solution, this ratio enables the cationic polysaccharide and the polyoxyethylene-polyoxypropylene block copolymer to form a reasonable adsorption layer thickness on the particle surface, achieving a synergistic effect of electrostatic repulsion and steric hindrance, effectively solving the problem of nanoparticle polymerization during the grinding process, while ensuring the effective component content of the suspending agent, thus meeting the needs of practical applications.

[0020] In a specific embodiment of step S2, the pretreated mancozeb technical, zinc sulfate, cationic polysaccharide, polyoxyethylene-polyoxypropylene block copolymer, and the first auxiliary agent are added to water for pre-dispersion, and then milled. After milling, the second auxiliary agent is added and stirred evenly to obtain mancozeb nanoscale aqueous suspension. The first auxiliary agent includes a preservative, a wetting agent, and an antifoaming agent, and the second auxiliary agent is a thickener. The preservative, wetting agent, antifoaming agent, and thickener can all be conventional choices in the art.

[0021] Optionally, in step S1, the washing continues until the pH value reaches 6.5 to 7.0.

[0022] Through the above technical solution, the pH range avoids the influence of residual acid and alkali on the raw material and the amphiphilic polymers adsorbed on its surface, ensuring the quality of the pretreated raw material; after filtration, it is directly used as a wet filter cake for subsequent grinding steps, avoiding the possible crystal agglomeration and damage to the amphiphilic polymer adsorption layer during the drying process, which is conducive to achieving nanoscale fineness in subsequent grinding.

[0023] Optionally, the sand grinding in step S2 includes primary grinding and secondary grinding; the primary grinding uses grinding media with a diameter of 0.4~0.6 mm; the secondary grinding uses grinding media with a diameter of 0.1~0.3 mm.

[0024] The above technical solution avoids the problems of low grinding efficiency and high energy consumption caused by directly using small-particle grinding media. Primary grinding rapidly breaks down large particles, while secondary grinding refines them to nanoscale particle size. Combined with a dispersant system, this effectively inhibits particle aggregation during the grinding process, achieving highly efficient preparation of nanoscale particles. The nanoscale particle size significantly increases the contact area between the suspension and pathogens during drug administration, resulting in significantly improved efficacy and reduced dosage.

[0025] Optionally, the pre-dispersion in step S2 includes: first dissolving the cationic polysaccharide and polyoxyethylene-polyoxypropylene block copolymer in water, and then adding the pretreated mancozeb technical and zinc sulfate for dispersion.

[0026] Through the above technical solution, the feeding sequence allows the dispersant to fully dissolve in the aqueous phase and form a micelle structure. When the active ingredient and zinc sulfate are added, the dispersant can be quickly adsorbed onto the particle surface, avoiding particle agglomeration in the pre-dispersion stage and providing a good initial dispersion state for subsequent sand milling to break through the nanoscale particle size.

[0027] Secondly, this application provides a manganese zinc nanoscale aqueous suspension prepared according to the preparation method described above.

[0028] In summary, this application includes at least one of the following beneficial technical effects: 1. This application effectively solves the problem of easy polymerization of nanoparticles during the grinding process by introducing an amphiphilic polymer containing a siloxane backbone and polyether side chains during the mancozeb synthesis stage, combined with the synergistic effect of cationic polysaccharides and polyoxyethylene-polyoxypropylene block copolymers during the grinding stage. This breaks through the particle size bottleneck of traditional sand milling methods, enabling the final product particle size D50 to reach about 140~180 nm. The nanoscale particle size significantly increases the contact area between the drug and the target during drug application, reducing the amount of drug used and improving the efficacy. 2. Pretreatment of the amphiphilic polymer during the crystal nucleation stage refines the active ingredient crystals. Its low surface tension properties act as a micro-lubricant during the grinding process, effectively inhibiting particle aggregation. Combined with a graded grinding strategy, this significantly shortens the grinding time and reduces energy consumption. The grinding process temperature is controlled below 30 ℃, which significantly improves production efficiency and reduces energy consumption. 3. The nano-sized particles extend the effective period of the suspension against citrus black spot disease to more than 26 days. Even if it rains 2 hours after application, the leaf residue rate is still more than 80%, achieving the technical effects of large contact area, low dosage, high efficacy and excellent resistance to rain washout. Detailed Implementation

[0029] The present application will be further described in detail below with reference to specific embodiments.

[0030] It should be noted that the specific embodiments described in this application are intended to elaborate on the technical solutions in the claims. Terms such as "first," "second," "primary," and "secondary" used herein are merely for distinguishing different components or structures and do not indicate any order or importance.

[0031] The following examples further illustrate the mancozeb nanoscale aqueous suspension and its preparation method described in this application. These examples are implemented based on the technical solution of this application, providing detailed implementation methods and specific operating procedures; however, the scope of protection of this application is not limited to the following examples.

[0032] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0033] Preparation of sodium mancozeb aqueous solution: Weigh 2 kg of ethylenediamine (33.333 mol), 6.09 kg of carbon disulfide (79.992 mol), and 3.2 kg of 98% caustic soda flakes (79.992 mol) for later use. Prepare a 30% sodium hydroxide aqueous solution with the weighed 98% caustic soda flakes. First, add the weighed ethylenediamine and water (weight ratio of ethylenediamine to water is 1:1) to a four-necked flask and start stirring. Then add the sodium hydroxide aqueous solution and control the temperature at 40 ℃. Finally, add carbon disulfide dropwise. After the addition is complete, keep warm for 5 h to obtain a sodium mancozeb aqueous solution with a mass concentration of approximately 41%. Polyether-modified polydimethylsiloxane-1: Purchased from Shandong Dayi Chemical Co., Ltd., model DY-ET333 polyether-modified silicone oil, HLB value 8.9; Polyether-modified polydimethylsiloxane-2: Purchased from Shandong Dayi Chemical Co., Ltd., model DY-ET203 polyether-modified silicone oil, HLB value 7.0; Polyether-modified polydimethylsiloxane-3: Purchased from Shandong Dayi Chemical Co., Ltd., model ET1060 polyether-modified silicone oil, HLB value 10.2; Polyether-modified polydimethylsiloxane-4: Purchased from Shandong Dayi Chemical Co., Ltd., model DY-ET204 polyether-modified silicone oil, HLB value 4.9; Hydroxypropyltrimethylammonium chloride chitosan: Purchased from Xi'an Qiyue Biotechnology Co., Ltd.; Polyoxyethylene-polyoxypropylene block copolymer: Purchased from Xi'an Ruixi Biotechnology Co., Ltd. Xanthan gum (thickener): Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Fatty alcohol polyoxyethylene ether (wetting agent): Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Organosilicon defoamer: Purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0034] Test case Particle size determination: The volume median diameter (D50) and particle size distribution span (Span) of the suspension were determined using a laser particle size analyzer. Thermal stability: The sample was stored in a 54 ℃ constant temperature incubator for 14 days. Samples were taken every 3 days to observe the appearance and determine the suspension rate. Suspension rate determination method: 10 mL of sample was placed in a 10 mL stoppered graduated cylinder and allowed to stand for 24 h. Then, 1 mL of suspension was pipetted from 1 cm below the liquid surface and placed in a pre-weighed evaporating dish. The dish was dried at 105 ℃ to constant weight, and the suspension rate was calculated. Low temperature stability: The sample was placed in a 0 ℃ refrigerator for 7 days and observed for phenomena such as freezing, layering, and crystallization. Then it was restored to room temperature and observed whether it could restore a uniform dispersion state. Field efficacy: At the early stage of citrus black spot disease, the fungicide was diluted with an active ingredient concentration of 600 mg / L and sprayed. A commercially available 70% mancozeb wettable powder (with the same active ingredient concentration) was used as a control. Disease index was assessed at 7, 14, 21, and 28 days after application, and the control effect was calculated. Control efficacy (%) = (Disease index in control area - Disease index in treatment area) / Disease index in control area × 100%; Rain washout resistance: The pesticide solution was sprayed on citrus leaves, and artificial simulated rainfall was carried out 2 hours later (rainfall intensity 30 mm / h, lasting 30 min). The leaves were then taken and the residual pesticide was washed off with methanol. The residual amount was determined by high performance liquid chromatography and the leaf surface residue rate was calculated. Residue rate = residual amount of active ingredient after washing / original pesticide load before washing × 100%.

[0035] Example 1 A method for preparing a mancozeb nano-sized aqueous suspension, the method comprising the following steps: S1. Add 1000 g of sodium mancozeb aqueous solution to a four-necked flask, then add 16.5 g of polyether modified polydimethylsiloxane-1 (HLB value 8.9, amount is 4% of the weight of sodium mancozeb), stir and mix evenly at room temperature (25 ℃) for 30 min to obtain a mixture. The four-necked flask was heated to 45 °C and kept at a constant temperature. 1.465 L of 1.2 mol / L manganese sulfate aqueous solution was added dropwise to the above mixture at a rate of 10 mL / min using a constant flow pump. Stirring was maintained during the dropwise addition. After the dropwise addition was completed, the reaction was continued at 45 °C for 2 h. After the reaction was completed, the reaction product was filtered to obtain a yellow solid product. The solid product was repeatedly washed with deionized water, and the pH value of the filtrate was measured after each wash until the pH value of the filtrate reached 6.8. The washed filter cake was filtered again, and the wet filter cake obtained was the pretreated mancozeb technical. S2. First, add 50 g of deionized water to the mixing mill, then add 7.5 g of hydroxypropyltrimethylammonium chloride chitosan and 4 g of polyoxyethylene polyoxypropylene block copolymer in sequence. Stir at high speed (2000 rpm) for 30 min at room temperature to form a uniform micelle solution. Then, add 35 g of the pretreated mancozeb technical prepared in step S1, 7.5 g of zinc sulfate and the first auxiliary agent (including 1.0 g of fatty alcohol polyoxyethylene ether, 0.2 g of sodium benzoate and 0.3 g of organosilicon defoamer) to the above micelle solution and continue stirring at high speed (2500 rpm) for 40 min to obtain a pre-dispersed slurry. The pre-dispersed slurry was transferred to a horizontal sand mill, and zirconia grinding media with a diameter of 0.5 mm (grinding media filling rate of 70%) was added. The mill speed was set to 1200 rpm, and the mill was circulated and ground for 90 min. During the grinding process, the slurry temperature was controlled not to exceed 30 ℃ by circulating cooling water. After the first-stage grinding was completed, the particle size was measured. At this time, D50 was about 600 nm. After primary grinding, the slurry was filtered to remove the 0.5 mm grinding media, and then transferred to another sand mill. Zirconia grinding media with a diameter of 0.2 mm (grinding media filling rate of 75%) was added. The mill speed was set to 1500 rpm, and the grinding was circulated for 120 min. During the grinding process, the temperature was controlled not to exceed 30 ℃ by circulating cooling water. After the secondary grinding was completed, the particle size was measured by sampling. At this time, D50 reached 150 nm. After secondary grinding, the slurry was filtered to remove the grinding media. Then, the second additive (0.8 g xanthan gum) was added under stirring and mixed evenly to obtain the final mancozeb nano-sized aqueous suspension.

[0036] Example 2 The procedure was carried out as described in Example 1, except that in step S1, the amount of polyether-modified polydimethylsiloxane-1 was adjusted to 8.2 g (2% of the weight of sodium mancozeb), the reaction temperature was 40 °C, and the mixture was washed until the pH value was 6.5. In step S2, the amounts of each component are adjusted as follows: 30 g of pretreated mancozeb technical, 5 g of zinc sulfate, 5 g of hydroxypropyltrimethylammonium chloride chitosan, 2 g of polyoxyethylene-polyoxypropylene block copolymer, first auxiliary agent (including 0.8 g of fatty alcohol polyoxyethylene ether, 0.15 g of sodium benzoate and 0.2 g of silicone defoamer), second auxiliary agent (0.6 g of xanthan gum), and water is added to 100 g; the first-stage grinding uses a grinding media with a diameter of 0.4 mm and the grinding time is 100 min; the second-stage grinding uses a grinding media with a diameter of 0.1 mm and the grinding time is 150 min.

[0037] Example 3 The procedure was carried out as described in Example 1, except that in step S1, the amount of polyether-modified polydimethylsiloxane-1 was adjusted to 32.96 g (8% of the weight of sodium mancozeb), the reaction temperature was 50 °C, and the mixture was washed until the pH value was 7.0. In step S2, the amounts of each component are adjusted as follows: 40 g of pretreated mancozeb technical, 10 g of zinc sulfate, 10 g of hydroxypropyltrimethylammonium chloride chitosan, 6 g of polyoxyethylene-polyoxypropylene block copolymer, first auxiliary agent (including 1.2 g of fatty alcohol polyoxyethylene ether, 0.25 g of sodium benzoate and 0.4 g of silicone defoamer), second auxiliary agent (1.0 g of xanthan gum), and water to make up to 100 g; the first-stage grinding uses a grinding media with a diameter of 0.6 mm and the grinding time is 80 min; the second-stage grinding uses a grinding media with a diameter of 0.3 mm and the grinding time is 100 min.

[0038] Example 4 The procedure was carried out as described in Example 1, except that all polyether-modified polydimethylsiloxane-1 was replaced with polyether-modified polydimethylsiloxane-2.

[0039] Example 5 The procedure was carried out as described in Example 1, except that all polyether-modified polydimethylsiloxane-1 was replaced with polyether-modified polydimethylsiloxane-3.

[0040] Example 6 The procedure was carried out as described in Example 1, except that all polyether-modified polydimethylsiloxane-1 was replaced with polyether-modified polydimethylsiloxane-4.

[0041] Example 7 The process was carried out in accordance with Example 1, except that in step S2, 50 g of deionized water, 7.5 g of hydroxypropyltrimethylammonium chloride chitosan, 4 g of polyoxyethylene polyoxypropylene block copolymer, 35 g of the pretreated mancozeb technical wet filter cake prepared in step S1, 7.5 g of zinc sulfate, and the first auxiliary agent (including 1.0 g of fatty alcohol polyoxyethylene ether, 0.2 g of sodium benzoate and 0.3 g of organosilicon defoamer) were added simultaneously to the slurry mixer and stirred at high speed (2500 rpm) for 40 min to obtain a pre-dispersed slurry.

[0042] Example 8 The process is carried out in accordance with Example 1, except that in step S2, no graded grinding is performed, and a grinding medium with a diameter of 0.2 mm is used directly for one-time grinding, and the grinding time is extended to 300 min.

[0043] Comparative Example 1 The procedure was carried out in accordance with Example 1, except that polyether-modified polydimethylsiloxane-1 was not added in step S1, and sodium mancozeb aqueous solution was directly reacted with manganese sulfate aqueous solution, with the remaining operations being the same.

[0044] Comparative Example 2 The procedure was carried out as described in Example 1, except that hydroxypropyltrimethylammonium chloride chitosan was not added in step S2, and only polyoxyethylene polyoxypropylene block copolymer was used as a dispersant, with the amount of polyoxyethylene polyoxypropylene block copolymer increased to 11.5 g.

[0045] Comparative Example 3 The procedure was carried out as described in Example 1, except that in step S2, the polyoxyethylene-polyoxypropylene block copolymer used only hydroxypropyltrimethylammonium chloride chitosan as a dispersant, and the amount of hydroxypropyltrimethylammonium chloride chitosan was increased to 11.5 g.

[0046] Comparative Example 4 The procedure was carried out as described in Example 1, except that in step S1, polyether-modified polydimethylsiloxane-1 was not added. Instead, in step S2, polyether-modified polydimethylsiloxane-1, along with pretreated mancozeb, zinc sulfate, cationic polysaccharide, and polyoxyethylene-polyoxypropylene block copolymer, were added to water for pre-dispersion.

[0047] The mancozeb nano-sized aqueous suspensions prepared in Examples 1-8 and Comparative Examples 1-4 were subjected to particle size determination, thermal storage stability, low temperature stability, field efficacy, and rain erosion resistance tests. The test results are shown in Tables 1 and 2. Table 1

[0048] Table 2

[0049] As shown in Tables 1 and 2, the mancozeb nano-sized aqueous suspension prepared in the embodiments of this application all have a particle size D50 of nanometers (approximately 140-180 nm), effectively breaking through the particle size bottleneck of traditional sand milling and solving the problem of particle aggregation during grinding. The nano-sized particle size significantly increases the contact area between the agent and the target during application, resulting in significantly better field efficacy and resistance to rain washout than the comparative example, achieving the technical effect of low dosage and high efficacy. The thermal storage stability and low temperature stability of all embodiments meet the standards.

[0050] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application.

Claims

1. A method for preparing a mancozeb nano-sized aqueous suspension, characterized in that, The preparation method includes the following steps: S1. After mixing the sodium mancozeb aqueous solution with the amphiphilic polymer containing the siloxane main chain and polyether side chain evenly, add the manganese sulfate aqueous solution to react. Then, filter the reaction product for the first time, and wash and filter the solid product obtained from the first filtration in sequence. The solid product obtained from the second filtration is the pretreated mancozeb technical. S2. The pretreated mancozeb technical, zinc sulfate, cationic polysaccharide, polyoxyethylene-polyoxypropylene block copolymer and additives are added to water for pre-dispersion, and then milled to obtain mancozeb nano-sized aqueous suspension. The additives are selected from one or more of preservatives, wetting agents, defoamers and thickeners.

2. The preparation method according to claim 1, characterized in that, The amphiphilic polymer containing a siloxane main chain and a polyether side chain is polyether-modified polydimethylsiloxane.

3. The preparation method according to claim 2, characterized in that, The hydrophilic-lipophilic balance value of the polyether-modified polydimethylsiloxane is 7-9.

4. The preparation method according to claim 1, characterized in that, The cationic polysaccharide is hydroxypropyltrimethylammonium chloride chitosan.

5. The preparation method according to claim 1 or 2, characterized in that, The amount of the amphiphilic polymer containing the siloxane main chain and polyether side chain is 2-8% of the weight of sodium mancozeb.

6. The preparation method according to claim 1, characterized in that, By weight, the amounts of each component in step S2 are as follows: 30-40 parts of pretreated mancozeb technical grade on a dry basis, 5-10 parts of zinc sulfate, 5-10 parts of cationic polysaccharide, 2-6 parts of polyoxyethylene-polyoxypropylene block copolymer, 1-5 parts of additives, and water to make up to 100 parts.

7. The preparation method according to claim 1, characterized in that, In step S1, the washing continues until the pH value reaches 6.5~7.

0.

8. The preparation method according to claim 1, characterized in that, The sand grinding in step S2 includes primary grinding and secondary grinding; the primary grinding uses grinding media with a diameter of 0.4~0.6 mm; the secondary grinding uses grinding media with a diameter of 0.1~0.3 mm.

9. The preparation method according to claim 1, characterized in that, The pre-dispersion in step S2 includes: first dissolving the cationic polysaccharide and polyoxyethylene-polyoxypropylene block copolymer in water, and then adding the pretreated mancozeb technical and zinc sulfate for dispersion.

10. A manganese zinc nanoscale aqueous suspension obtained by the preparation method according to any one of claims 1 to 9.

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