Mancozeb polyurethane microcapsule suspending agent as well as preparation method and application thereof

Abstract

The invention provides a mancozeb polyurethane microcapsule suspending agent as well as a preparation method and application thereof, and belongs to the technical field of pesticide preparations. According to the mancozeb microcapsule, polyurethane is used as the capsule wall of the microcapsule through an interfacial polymerization technology, mancozeb is coated in the polyurethane capsule wall, and direct contact between core substance mancozeb and external water, oxygen and other environmental factors is effectively prevented through the physical isolation effect of the compact polyurethane capsule wall, so that the storage stability of the product is greatly prolonged. The polyurethane capsule wall is used as a release barrier and can control the release rate of the mancozeb, so that the mancozeb is slowly released on the surface of a crop target, thereby prolonging the lasting period of the pesticide effect, reducing the pesticide application frequency and reducing the pesticide application cost.

Description

Technical Field

[0001] This invention relates to the field of pesticide formulation technology, specifically to a mancozeb polyurethane microcapsule suspension, its preparation method, and its application. Background Technology

[0002] Mancozeb is a broad-spectrum, protective organosulfur fungicide widely used to control fungal diseases in various crops. However, mancozeb technical has several drawbacks during storage and use, such as poor chemical stability, susceptibility to photodegradation, easy generation of dust during application, and a relatively short duration of efficacy.

[0003] Existing mancozeb formulations, such as wettable powder (WP), generate significant dust pollution during preparation, posing a potential threat to the health of applicators and the surrounding environment. While suspension concentrates (SC) mitigate the dust problem to some extent, mancozeb is prone to hydrolysis in aqueous media, leading to degradation of the active ingredient during storage, thus affecting the product's shelf life and control efficacy.

[0004] Microencapsulation is a technique that encapsulates an active core substance (solid, liquid, or gas) within a micron-sized polymer capsule. This technique effectively protects the core substance, isolating it from external environmental factors (such as water, oxygen, and light), and preventing premature decomposition or volatilization. However, despite existing reports on pesticide microencapsulation, developing a microcapsule suspension with stable preparation process, high encapsulation efficiency, excellent storage stability, and significantly extended effective duration remains a pressing technical challenge in this field, particularly for active ingredients like mancozeb, which are highly sensitive to humidity and temperature. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a mancozeb polyurethane microcapsule suspension, its preparation method, and its application. The preparation method provided by this invention features mild reaction conditions and an easily controllable process. The prepared mancozeb polyurethane microcapsule suspension exhibits high encapsulation efficiency, suspension rate, and thermal storage stability, effectively extending the duration of action of mancozeb.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing mancozeb polyurethane microcapsule suspension, comprising the following steps: (1) Mix the polyisocyanate and the hydrophobic solvent to obtain the oil phase; (2) Mix mancozeb technical, dispersant, wetting agent and water to obtain an aqueous suspension of mancozeb; (3) The oil phase is added to the aqueous suspension of mancozeb and shear emulsification is performed to obtain an O / W type emulsion; (4) The O / W type emulsion is mixed with a polyol and subjected to interfacial polymerization to obtain a polyurethane microcapsule slurry containing mancozeb. (5) The polyurethane microcapsule slurry containing mancozeb is mixed with a suspending agent, an antifreeze agent, an antifoaming agent and a thickener, and the pH value is adjusted to 6-8 to obtain a mancozeb polyurethane microcapsule suspension.

[0007] Preferably, the polyisocyanate includes one or more of polyphenylmethane polyisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate; The mass ratio of the polyisocyanate to the hydrophobic solvent is 1:(0.5~5).

[0008] Preferably, the mixing method in step (2) is shear mixing or sand milling mixing; The aqueous suspension of mancozeb, by mass percentage, comprises: 30-70% mancozeb technical, 1-10% dispersant, 0.5-5% wetting agent, and the balance being water.

[0009] Preferably, the dispersant comprises one or more of sodium lignosulfonate, polycarboxylate dispersant, naphthalene sulfonate formaldehyde condensate, styrene-acrylic acid copolymer, and EO / PO block polyether; The wetting agent includes one or more of sodium dodecyl sulfate, alkylphenol polyoxyethylene ether phosphate, saponins, sodium dioctyl succinate sulfonate and alkyl naphthalene sulfonate.

[0010] Preferably, the volume ratio of the oil phase to the aqueous suspension of mancozeb is 1:(3~12). The shear emulsification rate is 5000~12000 rpm, and the time is 10~30 min.

[0011] Preferably, the polyol includes one or more of ethylene glycol, propylene glycol, butanediol, polyethylene glycol, glycerol, and trimethylolpropane; The molar ratio of isocyanate to hydroxyl group in the polyisocyanate is (1.0~1.5):1; The interfacial polymerization temperature is 10~80℃, and the time is 1~4 h.

[0012] Preferably, the suspending agent is xanthan gum and / or magnesium aluminum silicate; the mass content of the suspending agent in the mancozeb polyurethane microcapsule suspension is 0.1-1%; The antifreeze is ethylene glycol and / or propylene glycol, and the mass content of the antifreeze in the mancozeb polyurethane microcapsule suspension is 2-8%; The defoamer is an organosilicon defoamer, and the mass content of the defoamer in the mancozeb polyurethane microcapsule suspension is 0.1~0.5%; The thickener is xanthan gum and / or gum arabic, and the mass content of the thickener in the mancozeb polyurethane microcapsule suspension is 0.1-1%.

[0013] This invention provides a mancozeb polyurethane microcapsule suspension prepared by the above preparation method.

[0014] Preferably, the D of the mancozeb polyurethane microcapsules 50 The particle size is 1~10 μm.

[0015] This invention provides the application of the above-mentioned mancozeb polyurethane microcapsule suspension as a fungicide for crops.

[0016] This invention provides a method for preparing a mancozeb polyurethane microcapsule suspension. Using interfacial polymerization technology, polyurethane is used as the microcapsule wall, encapsulating mancozeb within the polyurethane wall. The dense polyurethane wall effectively prevents direct contact between the core substance, mancozeb, and external environmental factors such as water and oxygen, significantly extending the product's storage stability. The polyurethane wall also acts as a release barrier, controlling the release rate of mancozeb, allowing it to be slowly released onto the crop target surface, thereby extending the duration of efficacy, reducing the number of applications, and lowering costs. The mancozeb polyurethane microcapsule suspension obtained by this invention is a water-based suspension, completely solving the dust problem associated with traditional powder (WP) formulations, significantly reducing the risk of inhalation and skin irritation for applicators, and is more environmentally friendly.

[0017] Furthermore, this invention employs interfacial polymerization to prepare microcapsules. By precisely controlling the proportions of polyurethane prepolymer monomers, dispersants, and solvents in the preparation of mancozeb polyurethane microcapsule suspensions, synergistic optimization of the microcapsule structure and performance is achieved: 1) Regarding encapsulation efficiency: The optimized amount of capsule wall material ensures that the polyurethane shell has a suitable thickness and cross-linking density, effectively solving the "puncture" problem caused by the irregular shape of mancozeb solid particles. This ensures that the active ingredient is completely encapsulated within the core, significantly improving the encapsulation efficiency of the microcapsules and effectively isolating the external environment from the unstable mancozeb. 2) Regarding suspension efficiency: The optimized ratio of dispersant to wetting agent significantly reduces the oil-water interfacial tension. Combined with the interfacial polymerization process, microcapsules with small particle size and uniform distribution are obtained. Simultaneously, a strong steric hindrance layer and electrostatic repulsion layer are constructed on the capsule wall surface, preventing flocculation and sedimentation of the microcapsules during storage. This results in excellent autodispersibility and high suspension efficiency after dilution, leading to a more sustained and uniform efficacy.

[0018] Furthermore, this invention uses interfacial polymerization to prepare microcapsules, which has mild reaction conditions, a clear process flow, conventional equipment requirements, strong process applicability, and is easy to realize industrial production. Attached Figure Description

[0019] Figure 1 This is a SEM image of the mancozeb polyurethane microcapsule suspension obtained in Example 1. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of protection of this invention.

[0021] This invention provides a method for preparing mancozeb polyurethane microcapsule suspension, comprising the following steps: (1) Mix the polyisocyanate and the hydrophobic solvent to obtain the oil phase; (2) Mix mancozeb technical, dispersant, wetting agent and water to obtain an aqueous suspension of mancozeb; (3) The oil phase is added to the aqueous suspension of mancozeb and shear emulsification is performed to obtain an O / W type emulsion; (4) The O / W type emulsion is mixed with a polyol and subjected to interfacial polymerization to obtain a polyurethane microcapsule slurry containing mancozeb. (5) The polyurethane microcapsule slurry containing mancozeb is mixed with a suspending agent, an antifreeze agent, an antifoaming agent and a thickener, and the pH value is adjusted to 6-8 to obtain a mancozeb polyurethane microcapsule suspension.

[0022] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0023] This invention involves mixing a polyisocyanate with a hydrophobic solvent to obtain an oil phase. In this invention, the polyisocyanate is preferably one or more of polyphenylmethane polyisocyanate (PAPI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI); the hydrophobic solvent is preferably one or more of aromatic solvents, ester solvents, vegetable oil solvents, alkane / mineral oil solvents, and ketone solvents; the aromatic solvent is preferably xylene, toluene, or mesitylene. The solvent is selected from one or more of heavy aromatic hydrocarbons; the ester solvent is preferably one or more of sec-butyl acetate, butyl acetate, fatty acid methyl esters (such as methyl oleate), and dibutyl phthalate; the vegetable oil solvent is preferably one or more of soybean oil, rapeseed oil, corn oil, and their epoxidized modified products; the alkane / mineral oil solvent is preferably one or more of solvent oil S-150, S-200, white oil, liquid paraffin, and isoalkanes; the ketone solvent is preferably cyclohexanone and / or methyl isobutyl ketone.

[0024] In this invention, the mass ratio of the polyisocyanate to the hydrophobic solvent is preferably 1:(0.5~5), more preferably 1:(1~3), and specifically can be 1:0.5, 1:1, 1:2, 1:3, 1:4 or 1:5. This invention does not have special requirements for the mixing method; any mixing method well known in the art can be used, such as stirring.

[0025] This invention involves mixing mancozeb technical, a dispersant, a wetting agent, and water to obtain an aqueous suspension of mancozeb. In this invention, the purity of the mancozeb technical is preferably 94-98%. This purity range ensures that the active ingredient of mancozeb is sufficiently high during production, thereby guaranteeing the efficacy of the formulation, while also reducing the impact of impurities on the stability and performance of the final formulation. For different dosage forms in practical applications, the purity of the selected technical can be adjusted as needed to achieve optimal efficacy and cost-effectiveness.

[0026] In this invention, the dispersant preferably includes one or more of sodium lignosulfonate, polycarboxylate dispersant, naphthalene sulfonate formaldehyde condensate, styrene-acrylic acid copolymer, and EO / PO block polyether. The polycarboxylate dispersant is preferably SD-816, SD-819, or Geropon T / 36. The naphthalene sulfonate formaldehyde condensate is preferably NNO. The styrene-acrylic acid copolymer is preferably Atlox 4913. The wetting agent preferably includes one or more of sodium dodecyl sulfate, alkylphenol polyoxyethylene ether phosphate, saponins, sodium dioctyl succinate sulfonate, and alkyl naphthalene sulfonate.

[0027] In this invention, the mixing method is preferably shear mixing or sand milling mixing. In this invention, the shear mixing is preferably carried out in a high-speed shear disperser, preferably using a toothed rotor-stator shear head. During the shear mixing process, the material temperature is preferably controlled to be ≤40℃. If necessary, an ice water bath or jacket cooling can be used. The shear mixing is preferably carried out by first mixing at low speed (2000~4000 rpm) for 1~2 minutes, and then increasing to high speed (8000~10000 rpm) for shearing for 15~25 minutes to ensure initial uniformity and reduce splashing.

[0028] In this invention, the sand milling and mixing is preferably wet sand milling, and the preferred sand milling parameters are: grinding media particle size of 0.4~1.2 mm, more preferably 0.6~0.8 mm; sand mill rotor linear velocity of 10~15 m / s; sand milling time of 14 hours, more preferably 1.5~2.5 hours; and material circulation grinding to the system particle size D. 90 ≤ 5 μm, D is preferred 90 ≤ 3 μm. In this invention, the material temperature is controlled to be ≤ 50℃ during the sand milling process.

[0029] The aqueous suspension of mancozeb, by mass percentage, preferably comprises: 30-70% mancozeb technical grade, more preferably 40-60%; 1-10% dispersant, more preferably 2-8%; 0.5-5% wetting agent, more preferably 1-3%; and the balance being water. By controlling the amount of mancozeb in the aqueous suspension, this invention can ensure both the solid content and drug loading of the system while maintaining a suitable pre-dispersion viscosity and sufficient wetting and dispersion in the aqueous phase. This results in an aqueous suspension with fine and uniformly distributed particles, facilitating subsequent shear emulsification to form a stable O / W emulsion and perform interfacial polymerization. It avoids agglomeration, sedimentation, or cell wall breakage caused by excessive technical grade, thereby significantly improving the microcapsule encapsulation rate and suspension rate, enhancing thermal storage stability, and extending the duration of efficacy.

[0030] This invention does not have any special requirements regarding the order of preparation of the oil phase and the aqueous suspension of mancozeb.

[0031] In this invention, the oil phase is added to the aqueous suspension of mancozeb, and shear emulsification is performed to obtain an O / W type emulsion. In this invention, the volume ratio of the oil phase to the aqueous suspension of mancozeb is preferably 1:(3~12), more preferably 1:(4~8), and even more preferably 1:(4.5~6). In this invention, when the aqueous phase ratio is too low (e.g., below 1:3), the system viscosity increases, the active ingredient easily agglomerates and settles, the emulsion is unstable, leading to uneven capsule walls or core leakage; when the aqueous phase ratio is too high (e.g., above 1:12), the oil droplets are too sparsely dispersed, the interfacial polymerization efficiency decreases, which is not conducive to the formation of a dense capsule wall. Therefore, controlling the volume ratio of the oil phase to the aqueous phase at 1:(3~12), preferably 1:(4~8), can obtain a microcapsule suspension with uniform particle size, high encapsulation efficiency, and stable suspension.

[0032] In this invention, the shear emulsification rate is preferably 5000~12000 rpm, more preferably 6000~10000 rpm, and the time is preferably 10~30 min, more preferably 15~25 min, and even more preferably 20 min.

[0033] After obtaining the O / W emulsion, the present invention mixes the O / W emulsion with a polyol and performs an interfacial polymerization reaction to obtain a polyurethane microcapsule slurry containing mancozeb. In the present invention, the mixing method is preferably: the polyol is added to the O / W emulsion under stirring conditions.

[0034] In this invention, the polyol preferably includes one or more of ethylene glycol, propylene glycol, butanediol, polyethylene glycol, glycerol, and trimethylolpropane. The molar ratio of isocyanate to hydroxyl group in the polyisocyanate is preferably (1.0~1.5):1, more preferably (1.2~1.4):1. By controlling the excess of isocyanate, this invention can ensure sufficient interfacial polymerization while avoiding excessive crosslinking, thus keeping the polyurethane capsule wall formation rate and density within the optimal range. This results in a capsule wall with a complete structure, moderate thickness, and few defects, effectively reducing embrittlement, porosity, or side reactions caused by unreacted isocyanate. It also prevents incomplete film formation and core leakage caused by insufficient isocyanate, ultimately significantly improving the encapsulation efficiency, thermal storage stability, and sustained-release performance of the microcapsules.

[0035] In this invention, the temperature for interfacial polymerization is preferably 10-80°C, more preferably 20-60°C, and even more preferably 30-50°C, and the time is preferably 1-4 h, more preferably 2-3 h. After the interfacial polymerization reaction, the present invention preferably allows the mixture to cool naturally to room temperature.

[0036] After obtaining the polyurethane microcapsule slurry containing mancozeb, the present invention mixes the polyurethane microcapsule slurry containing mancozeb with a suspending agent, an antifreeze agent, an antifoaming agent and a thickener, and adjusts the pH value to 6-8 to obtain a mancozeb polyurethane microcapsule suspension. In this invention, the suspending agent is preferably xanthan gum and / or magnesium aluminum silicate, and the mass content of the suspending agent in the mancozeb polyurethane microcapsule suspension is 0.1-1%, more preferably 0.3-0.6%; the antifreeze agent is preferably ethylene glycol and / or propylene glycol, and the mass content of the antifreeze agent in the mancozeb polyurethane microcapsule suspension is 2-8%, more preferably 4-6%; the defoamer is preferably an organosilicon defoamer, and the mass content of the defoamer in the mancozeb polyurethane microcapsule suspension is 0.1-0.5%, more preferably 0.2-0.4%; the thickener is xanthan gum and / or gum arabic, and the mass content of the thickener in the mancozeb polyurethane microcapsule suspension is 0.1-1%, more preferably 0.3-0.7%.

[0037] This invention does not impose any special requirements on the mixing method; any mixing method well-known to those skilled in the art can be used. In this invention, the reagents used to adjust the pH value are preferably citric acid, sodium hydroxide, sodium carbonate, and / or sodium bicarbonate, and the amount used is sufficient to adjust the pH of the system to 6-8.

[0038] This invention provides a mancozeb polyurethane microcapsule suspension prepared by the above-described method. In this invention, the preferred contents of each component in the mancozeb polyurethane microcapsule suspension are as follows: Mancozeb contains 20-60%, more preferably 30-40%, and even more preferably 50%; The polyurethane wall material comprises 2-10%, more preferably 2-8%, and even more preferably 5-6%; The hydrophobic solvent is 1-15%, more preferably 3-10%, and even more preferably 5-8%; The dispersant is 2-8%, more preferably 3-7%, and even more preferably 4-6%; The wetting agent is 1-5%, more preferably 2-4%, and even more preferably 3%; The suspending agent is 0.1-1.0%, more preferably 0.3-0.6%; Antifreeze 2-8%, more preferably 4-6%; The defoamer is 0.1-0.5%, more preferably 0.2-0.4%; Thickener: 0.1-1.0%, more preferably 0.3-0.7%; The dosage of pH adjuster should be adjusted to a pH value of 6-8. Water balance.

[0039] In this invention, the polyurethane wall material is obtained by interfacial polymerization of polyisocyanate and polyol.

[0040] In this invention, the D of the mancozeb polyurethane microcapsules 50 The particle size is preferably 1~10 μm, more preferably 2~8 μm, and even more preferably 4~6 μm.

[0041] This invention provides the application of the above-mentioned mancozeb polyurethane microcapsule suspension as a fungicide for crops. In this invention, the crop is preferably potato, and the pathogen targeted is preferably *Potato blight pathogen*, a pathogen / oomycete that causes potato late blight.

[0042] The following detailed description, in conjunction with embodiments, illustrates the mancozeb polyurethane microcapsule suspension, its preparation method, and its application, but these should not be construed as limiting the scope of protection of this invention.

[0043] Example 1: Preparation of 40% Mancozeb Polyurethane Microcapsule Suspension (1) Preparation of oil phase: Weigh 3.0g of polyphenylmethane polyisocyanate (PAPI), dissolve it in 5.0g of xylene, stir evenly to obtain oil phase A.

[0044] (2) Preparation of aqueous phase: 35.0g of deionized water was added to the reactor, followed by 2.0g of wetting agent (sodium dodecyl sulfate) and 4.0g of dispersant (sodium lignosulfonate). After stirring and dissolving, 42.0g (95% pure content) of mancozeb technical was added. The high-speed shearing machine was turned on and sheared at 6000 rpm for 20 minutes to obtain a uniform mancozeb aqueous suspension B.

[0045] (3) Emulsification and interfacial polymerization: Oil phase A was slowly pumped into the reactor containing mancozeb aqueous suspension B, while the shear speed was increased to 10,000 rpm. Emulsification was carried out for 15 minutes to form a stable O / W emulsion. Then, 1.0 g of ethylene glycol was added under stirring, and the system was slowly heated to 60°C. The reaction was maintained at this temperature for 3 hours to form microcapsule slurry. During this process, the molar ratio of -NCO to -OH was approximately 1.1:1.

[0046] (4) Post-processing: The above microcapsule slurry was naturally cooled to room temperature, and 0.3g xanthan gum (as a suspending agent and thickener), 5.0g propylene glycol (as an antifreeze agent), and 0.2g silicone defoamer were added in sequence. The pH value was adjusted to 7.0 with 10% citric acid solution. Finally, deionized water was added to 100.0g and mixed evenly under stirring to obtain the 40% mancozeb polyurethane microcapsule suspension product.

[0047] SEM images of the obtained mancozeb polyurethane microcapsule suspension are shown below. Figure 1 As shown, by Figure 1 It can be seen that the sample as a whole has a near-spherical / spherical particle morphology, with a wide particle size distribution: mainly submicron to several micrometer particles, with larger and smaller particles coexisting in some areas. Most particle surfaces show slight roughness / undulation, and typical "satellite particles" can be observed attached to the surface of larger particles or distributed in the interparticle gaps.

[0048] Performance testing of mancozeb polyurethane microcapsule suspension: (1) The suspension rate was determined in accordance with CIPAC MT 184.1 "Determination of suspension rate of preparations formed by dilution with water": The sample was dispersed in CIPAC standard hard water at the specified concentration, and after the graduated cylinder was allowed to stand, the upper 9 / 10 was extracted, the content of active ingredients was determined, and the suspension rate was calculated. The suspension rate of the preparation was found to be ≥95%.

[0049] (2) Thermal storage stability test: The test was conducted in accordance with CIPAC MT 46.3.2 standard. The test conditions were as follows: 50 mL of the preparation sample was placed in a sealed glass bottle and stored in a constant temperature oven at 54℃ for 14 consecutive days. The content of the effective ingredients, suspension rate and pH value of the preparation were measured before and after storage.

[0050] Test results: After heat storage, the appearance of the suspending agent in this embodiment showed no obvious changes, the decomposition rate of the effective ingredients was <5.0%, and the suspension rate was still ≥90%, which was judged to be qualified for heat storage stability.

[0051] (3) Particle size detection: The particle size D of the microcapsules was detected using a laser particle size analyzer (Malvern Mastersizer 2000). 50 It is 5.2 μm.

[0052] (4) Encapsulation rate test: The encapsulation rate was calculated by measuring the content of free mancozeb outside the capsule wall, and the encapsulation rate reached 96.5%.

[0053] Example 2: Preparation of 60% Mancozeb Polyurethane Microcapsule Suspension (1) Preparation of oil phase: Weigh a mixture of 4.0g toluene diisocyanate (TDI) and 2.0g diphenylmethane diisocyanate (MDI), dissolve it in 8.0g of solvent oil S-150, mix it evenly, and obtain oil phase C.

[0054] (2) Aqueous phase preparation: Add 15.0g deionized water, 3.0g wetting agent (alkylphenol polyoxyethylene ether phosphate, 601P), and 6.0g dispersant (polycarboxylate dispersant, SD-816) to a sand mill, then add 64.0g (94% purity) of mancozeb technical material, and perform wet sand milling until the particle size D is reached. 90 A high-concentration mancozeb aqueous suspension D was obtained with a particle size of less than 5 μm.

[0055] (3) Emulsification and interfacial polymerization: The oil phase C was added to the aqueous suspension D and emulsified for 25 minutes under high-speed shear at 8000 rpm. Then, 1.5 g of glycerol was added and the system was heated to 75 °C and reacted at this temperature for 2.5 hours. During this process, the molar ratio of -NCO to -OH was approximately 1.2:1.

[0056] (4) Post-treatment: Cool the reaction solution to room temperature, add 0.5g magnesium aluminum silicate (as a suspending agent), 6.0g ethylene glycol (as an antifreeze agent), 0.3g defoamer, and 0.2g xanthan gum (as a thickener) in sequence, adjust the pH value to 6.5 with 5% sodium hydroxide solution, and finally add deionized water to 100.0g, stir evenly, and obtain the 60% mancozeb polyurethane microcapsule suspension product.

[0057] Performance testing of mancozeb polyurethane microcapsule suspension: (1) The suspension rate of the preparation was tested to be ≥92%.

[0058] (2) The heat storage stability test was the same as in Example 1. The test results showed that after heat storage, the appearance of the preparation in this example did not change significantly, the decomposition rate of the active ingredient was <3.0%, and the suspension rate was still ≥90%, which was determined to be qualified for heat storage stability.

[0059] (3) Particle size detection: The particle size D of the microcapsules was detected using a laser particle size analyzer (Malvern Mastersizer 2000). 50 It is 4.8μm.

[0060] (4) Encapsulation rate test: The encapsulation rate was calculated by measuring the content of free mancozeb outside the capsule wall, and the encapsulation rate reached 97.2%.

[0061] Example 3: Preparation of 30% Mancozeb Polyurethane Microcapsule Suspension (1) Preparation of oil phase: Weigh 2.5g of isophorone diisocyanate (IPDI), dissolve it in 4.0g of vegetable oil (soybean oil), stir evenly to obtain oil phase E.

[0062] (2) Aqueous phase preparation: 50.0g of deionized water, 1.5g of wetting agent (saponin) and 3.0g of dispersant (naphthalenesulfonate formaldehyde condensate) were added to the reactor and stirred to dissolve. Then, 32.0g (94% 100% content) of mancozeb technical was added and sheared at 5000rpm for 30 minutes to obtain an aqueous suspension F containing mancozeb.

[0063] (3) Emulsification and interfacial polymerization: The oil phase E was added to the aqueous suspension F and emulsified at a high-speed shear of 12,000 rpm for 10 minutes. Then, a mixture of 0.8 g of trimethylolpropane and 0.5 g of polyethylene glycol-400 polyol was added, and the system was heated to 50 °C and reacted for 4 hours. During this process, the molar ratio of -NCO to -OH was approximately 1.05:1.

[0064] (4) Post-treatment: Cool the reaction solution to room temperature, add 0.2g gum arabic (as a suspending agent and thickener), 4.0g propylene glycol, and 0.1g defoamer, adjust the pH value to 7.5, and finally add deionized water to 100.0g, mix evenly, and obtain the 30% mancozeb polyurethane microcapsule suspension product.

[0065] Performance testing of mancozeb polyurethane microcapsule suspension: (1) The suspension rate of the preparation was tested to be ≥94%.

[0066] (2) The heat storage stability test was the same as in Example 1. The test results showed that after heat storage, the appearance of the preparation in this example did not change significantly, the decomposition rate of the active ingredient was <4%, and the suspension rate was still ≥90%, which was judged to be qualified for heat storage stability.

[0067] (3) Particle size detection: The particle size D of the microcapsules was detected using a laser particle size analyzer (Malvern Mastersizer 2000). 50 It is 5.5μm.

[0068] (4) Encapsulation rate test: The encapsulation rate was calculated by measuring the content of free mancozeb outside the capsule wall, and the encapsulation rate reached 95.5%.

[0069] Comparative Example 1: Preparation of a conventional 30% mancozeb suspension (SC) Weigh 32.0g (94% purity) of mancozeb technical grade, add 3.0g dispersant (such as sodium lignosulfonate), 2.0g wetting agent (such as sodium dodecyl sulfate), 5.0g ethylene glycol, 0.3g xanthan gum, 0.2g magnesium aluminum silicate, 0.2g defoamer, and 57.3g deionized water. Mix well and then grind to a particle size D using a sand mill. 90 With a particle size less than 5 μm, a conventional 30% mancozeb suspension (SC) was obtained as a control.

[0070] field trials Target disease for control: Potato late blight (Phytophthora infestans) Test reagents: 30% mancozeb polyurethane microcapsule suspension prepared in Example 3, and conventional 30% mancozeb suspension prepared in Comparative Example 1.

[0071] Experimental design: A randomized block design was adopted, with 3 treatments, 4 replicates, and a plot area of ​​20 m². 2 .

[0072] Dosage: Treatment Group 1 (Example 3): Spray with water at a concentration of 600 g / ha of active ingredient (i.e., 2000 g / ha of formulation). Treatment Group 2 (Comparative Example 1): Spray with water at a concentration of 600 g / ha of active ingredient (i.e., 2000 g / ha of formulation). Treatment Group 3: Blank control (spray with water).

[0073] Application method: Apply the medicine at the early stage of potato late blight, for a total of 2 applications, with an interval of 7 days.

[0074] Survey and data analysis: Disease index was investigated 7, 14 and 21 days after application of the medicine to calculate the prevention and control effect.

[0075] Duration of efficacy determination: Focus on observing the control effect 14 days and 21 days after application.

[0076] 1) Calculation of the Disease Index (DI) The disease severity index reflects the prevalence of disease at a certain point in time, and is usually calculated using formula (1): Formula (1); in: : No. Grading values ​​for diseases (usually 0-9 or 0-5); : Belongs to the The number of plants (or leaves) at each level; Maximum severity level (e.g., 0-9 or 0-5); Total number of plants (or leaves) surveyed.

[0077] 2) Calculation of Control Efficacy (CE) The prevention and control effect was calculated by comparing the disease index of the treatment group and the blank control group, and the calculation formula is shown in formula (2): Formula (2); in: Disease index of the blank control group (control area without medication); Disease index of the treatment group (treatment area after drug administration).

[0078] The control effect is calculated at 7, 14 and 21 days after application, with particular attention paid to the control effect at 14 and 21 days as the standard for measuring the duration of effectiveness.

[0079] Experimental results: At the same application dosage (based on active ingredient), 14 days after application, the control efficacy of treatment group 1 (Example 3) was 85.2%, and the control efficacy of treatment group 2 (Comparative Example 1) was 70.5%. The results indicate that the microcapsule formulation of Example 3 has a significantly longer effective period than conventional suspension concentrate, extending its effective period against potato late blight by 5-7 days.

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of mancozeb polyurethane microcapsule suspension concentrate characterized in that, The preparation method comprises the following steps: (1) mixing a polyisocyanate and a hydrophobic solvent to obtain an oil phase; (2) mixing a maneb raw material, a dispersant, a wetting agent and water to obtain an aqueous suspension of maneb; (3) adding the oil phase into the aqueous suspension of maneb, and performing shear emulsification to obtain an O / W emulsion; (4) mixing the O / W emulsion and a polyol to perform interfacial polymerization, thereby obtaining a polyurethane microcapsule slurry containing maneb; (5) mixing the polyurethane microcapsule slurry containing maneb, a suspending agent, an antifreezing agent, an antifoaming agent and a thickening agent, and adjusting the pH value to 6-8, thereby obtaining a maneb polyurethane microcapsule suspension.

2. The production method according to claim 1, characterized by, The polyisocyanate comprises one or more of polyphenylmethane polyisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate; The mass ratio of the polyisocyanate to the hydrophobic solvent is 1:(0.5-5).

3. The preparation method according to claim 1, characterized in that, The mixing mode in step (2) is shear mixing or sand mill mixing; The aqueous suspension of maneb comprises, in terms of mass percentage, 30-70% of maneb raw material, 1-10% of dispersant, 0.5-5% of wetting agent and the balance of water.

4. The production method according to claim 1 or 3, characterized by, The dispersant comprises one or more of sodium lignosulfonate, polycarboxylate dispersant, naphthalene sulfonate formaldehyde condensate, styrene-acrylic acid copolymer and EO / PO block polyether. The wetting agent comprises one or more of sodium dodecyl sulfate, alkylphenol polyoxyethylene ether phosphate, saponin, dioctyl sodium sulfosuccinate and alkyl naphthalene sulfonate.

5. The preparation method according to claim 1, characterized in that, The volume ratio of the oil phase to the aqueous suspension of maneb is 1:(3-12); The shear emulsification is performed at a rate of 5000-12000 rpm for 10-30 min.

6. The preparation method according to claim 1, characterized in that, The polyol comprises one or more of ethylene glycol, propylene glycol, butanediol, polyethylene glycol, glycerol and trimethylolpropane; The molar ratio of isocyanate in the polyisocyanate to hydroxyl in the polyol is (1.0-1.5):1; The interfacial polymerization is performed at a temperature of 10-80 ℃ for 1-4 h.

7. The method of claim 1, wherein, The suspending agent is xanthan gum and / or magnesium aluminum silicate, and the mass content of the suspending agent in the maneb polyurethane microcapsule suspension is 0.1-1%; The antifreezing agent is ethylene glycol and / or propylene glycol, and the mass content of the antifreezing agent in the maneb polyurethane microcapsule suspension is 2-8%; The antifoaming agent is silicone antifoaming agent, and the mass content of the antifoaming agent in the maneb polyurethane microcapsule suspension is 0.1-0.5%; The thickening agent is xanthan gum and / or gum arabic, and the mass content of the thickening agent in the maneb polyurethane microcapsule suspension is 0.1-1%.

8. The maneb polyurethane microcapsule suspension prepared by the preparation method in any one of claims 1-7.

9. The mancozeb polyurethane microcapsule suspension concentrate according to claim 8, characterized in that, The D of the mancozeb polyurethane microcapsule is 1-10 μm. 50 The particle size is 1-10 μm.

10. The maneb polyurethane microcapsule suspension in claim 8 or 9 as a fungicide for crops.

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