Pesticide micro-capsule granules and preparation method thereof

[0066] The first step, preparation of pesticide microcapsule suspension:

[0067] The existing technology of pesticide microencapsulation mainly consists of three process routes:

[0068] The first is to adopt the route of interfacial polymerization, usually using isocyanate (TDI) or prepolymer (MDI) to react with polyamine or polyol to form a polyurea resin shell material.

[0069] The second method adopts the in-situ polymerization process route, generally adopts the urea-formaldehyde prepolymer solution to form the capsule, and controls the process parameters such as the acid addition speed, the acid addition method, the curing temperature, the solution stirring speed, etc., and adjusts the pH range , Under catalysis, polycondensation forms strong and impermeable microcapsules.

[0070] The third is a complex coagulation preparation process. In an aqueous solution mixed with dissolved natural polymer materials (such as gelatin and gum arabic), the solubility of natural polymer materials is reduced by adjusting the pH, and the natural polymer materials are condensed into capsules from the system. The curing agent is added to produce an amine-aldehyde condensation reaction, the natural polymer is cross-linked into a network structure, and the shape of the microcapsule is maintained to become a microcapsule.

[0071] The interfacial polymerization method used in the present invention prepares microcapsules. This method is the most commonly used method for preparing pesticide microcapsules and has the advantages of stable process and easy control. The process is briefly described as follows: Dissolve the active ingredients and suitable polymer capsule wall materials (monomers) in organic solvents, and then add the oil phase to the water phase containing suitable emulsifiers and protective glue under shear conditions In the solution, it is in the form of oil-in-water or water-in-oil, and a certain particle size is controlled as required. In addition, another water-soluble capsule wall material is added to the water phase, and the two materials react at the oil-water interface to form a polymer capsule wall around the droplets containing the active substance. This method can generally be carried out quickly, and the formed cyst wall is more regular and uniform, and the texture is hard.

[0072] The specific method of the present invention is: According to the materials provided in the formula, the microcapsule suspension can be prepared through the following process routes:

[0073] Heat and melt the original drug into the appropriate amount of isocyanate wall material monomer and stir to make the oil phase uniform;

[0074] Add a wetting and dispersing agent to the water in advance and stir evenly, then add the pre-configured oil phase, homogenize at high speed to form a stable oil-in-water emulsion;

[0075] Reduce the rotation speed, under suitable rotation speed conditions, add polyamine or polyol aqueous solution to participate in the interfacial polymerization reaction to form a polyurea resin capsule wall material. The reaction temperature is raised to a suitable interval and maintained for a period of time to solidify the capsule wall material into a capsule. After the capsule material is completely solidified into capsules, add a pH regulator to adjust to the required pH range, add appropriate amount of dispersant, binder, defoamer, etc., stir evenly to form a microcapsule suspension.

[0076] The process of the present invention is implemented and completed under normal pressure.

[0077] The temperature controlled by the polymerization reaction during the encapsulation process mentioned in the present invention is 30°C to 80°C, preferably 40°C;

[0078] The curing time required for the encapsulated material of the present invention is between 2 hours and 24 hours, preferably 8 hours;

[0079] The particle size of the microcapsule suspension obtained by the invention is controlled between 2um and 50um, and it has the characteristics of an aqueous pesticide suspension.

[0080] The content of the microcapsule suspending agent of the present invention can vary between 5% and 40%, and different contents can be formulated according to its different uses. The microcapsule suspension is also a dosage form that can control the release rate of active ingredients. According to its use, the thickness of the capsule shell can be determined to control the release rate to achieve the desired effect.

[0081] The second step: the pesticide microcapsule suspension is granulated and dried to obtain microcapsule granules. Generally, the granulation methods of pesticide granules include: spray drying granulation, fluid bed drying granulation, freeze drying granulation, pan granulation, extrusion granulation, high-speed mixing granulation, fluid bed granulation and compression granulation, etc. . In the present invention, spray drying granulation method (specifically, spray drying and granulation of the prepared microcapsule suspension to obtain microcapsule granules CG) and extrusion granulation method are preferably selected. The present invention mainly obtains microcapsule granules through the following two granulation and drying methods:

[0082] 1. The spray-drying granulation method is realized by the following steps: firstly mix the microcapsule suspension with dispersant, wetting agent, disintegrant and filler carrier, etc., and adjust its concentration and viscosity to obtain a slurry for spraying. Then, the slurry is sprayed into the spray tower into tiny droplets through the nozzle atomizer, and the hot air flows into the drying tower co-currently with the spray droplets. The microcapsule suspension agent enters the atomizer (pressure nozzle) under the action of a high-pressure pump, and then rotates at a high speed in the vortex chamber, and rotates and ejects from the nozzle hole to form spherical droplets. After the droplets are heated, the surface moisture evaporates quickly, and after drying, the hollow microcapsule granules CG are formed. or,

[0083] 2. Extrusion granulation method: the microcapsule suspension agent is adsorbed by the carrier filler, then wetting agent, dispersant, disintegrant, etc. are added together and mixed uniformly, then granulated by an extrusion granulator, and finally dried by boiling The microcapsule CG is obtained. This method is easy to operate and has low energy consumption.

[0084] In order to better illustrate the technology of the present invention, the following specific examples are used to further illustrate, but not limited to this:

[0085] Example 1: Formula components of abamectin microcapsule suspension

[0086]

[0087] Disperse 30kg of insecticide abamectin and 3kg of carrier white carbon black in 15kg of soybean oil (commercially available), stir evenly (oil phase), and then sand through a sand mill until the material is average The particle size reaches 2um~8um, then add 4kg of toluene diisocyanate TDI (Cangzhou Dahua TDI Co., Ltd.) and stir evenly (oil phase); then prepare the water phase: add 10kg of 10% polyvinyl alcohol PVA aqueous solution to 40kg of deionized water Stir evenly (water phase); put the prepared oil phase materials into the water phase and turn on high-speed homogenization to form a stable O/W emulsion; turn on the stirring (maintain 800 rpm), and then heat the homogenized emulsion to Maintain a stable curing temperature of the capsule wall material at 70°C for 3 hours, then add 0.1 kg of glacial acetic acid with a pH regulator to adjust the pH to about 7, and 0.5 kg of silicone defoamer to stir evenly to obtain 30% avermectin 100kg of microcapsule suspension.

[0088] The prepared 30% abamectin microcapsule suspension slurry 16.7kg, filler 60kg diatomaceous earth, ammonium sulfate 20kg, wetting agent Morwet EFW 1.0kg (Morwet series products are Akzo Nobel products), dispersant Morwet D-4255.0 kg, binder hydroxyethyl cellulose (HEC) 0.5 kg, disintegrating agent magnesium aluminum silicate 2 kg, stir and knead uniformly, this example uses the frame extrusion granulation in the extrusion granulation. The outer diameter of the obtained particles is 1mm-2mm, and finally through boiling, drying and sieving to obtain a yellowish-brown appearance, a moisture content of about 2.5%, and a content of 5% abamectin microcapsules.

[0089] Example two, formula components of alachlor microcapsule suspension

[0090]

[0091] Heat 20 kg of the herbicide alachlor to a molten state, add 2 kg of polyphenyl polymethylene polyisocyanate PAPI (Bayer, Germany) and 1 kg of diphenylmethane diisocyanate MDI (Yantai Wanhua Polyurethane Co., Ltd.) Stir evenly (oil phase); add 0.2kg of methyl cellulose CMC to 50kg of deionized water, stir evenly (water phase), put the prepared oil phase materials into the water phase and turn on high-speed homogenization to form a stable O /W emulsion; start stirring (maintain 400 revolutions/min), then heat the homogenized emulsion to 40°C, and slowly add 0.5 kg of ethylene diamine to maintain a stable curing temperature of the capsule wall material for 20 hours, and then add the lubricant Wet agent NNO 3.0kg (Shanghai Tiantan Auxiliary Factory), dispersant sodium lignosulfonate (made in Russia) 5.0kg, disintegrant modified starch 1.0kg, white carbon black 17kg, pH regulator 0.2kg glacial acetic acid, 0.4 kg of organosilicon defoamer is stirred evenly to obtain 20% alachlor microcapsule suspension.

[0092] Please refer to figure 1 , figure 1 It is a schematic diagram of the spray drying granulation process used in the embodiment of the present invention. The spray dryer used in this example is a ZPG-150 spray dryer (Changzhou Xianfeng Drying Engineering Co., Ltd.), which includes the slurry storage tank 1, the feed pump 2, the nozzle 3, and the atomizer 4 connected in sequence by pipelines. , Drying tower 5, cyclone separator 6, induced draft fan 7, water film dust collector 8, using steam heat exchanger for heating. An inlet thermometer 91 is provided at the hot air inlet, and an outlet thermometer 91 is provided at the outlet. The main technical parameters of the ZPG-150 spray dryer equipment are: water evaporation 50-100Kg/h; tower diameter/tower height 4M/9.7M; operating temperature: inlet temperature 50-100/outlet temperature 30-70; atomization LPG-150; Rotation speed: 18000r.pm; Disk diameter: 150mm; Steam consumption: about 325~375kg/h; Drying system: Open circulation system; Feeding method: High-pressure pump stable feeding; Hot air contact method: Parallel flow; Atomization method: centrifugal atomization.

[0093] When granulating, control the temperature of the hot air inlet in the spray dryer at 80℃, pour the 20% alachlor microcapsule suspension agent into the slurry storage tank, and pump it into the atomizer through the feed pump to atomize the slurry , And then produce high-speed rotation in the drying tower, and form spherical droplets after rotating and spraying from the atomizer nozzle. After the droplets are heated, the surface moisture evaporates rapidly to form porous solid particles, which are finally dried to form microcapsule granules. Finally, 50 kg of alachlor microcapsule granules with an appearance of brown granules, a moisture control of about 3% and a content of about 40%, are obtained.

[0094] Example 3: 28% chlorpyrifos microcapsule suspension

[0095]

[0096] Heat 28 kg of chlorpyrifos original drug into a hot melt state, then add 3.0 kg of polyphenyl polymethylene polyisocyanate PAPI (Bayer, Germany) and 1.0 kg of toluene diisocyanate TDI (Cangzhou Dahua TDI Co., Ltd.) and stir well It is the oil phase; add 1.0kg of emulsifier NP-10 (Nanjing Taihua Co., Ltd.), 5kg of binder xanthan gum (2%) aqueous solution into 57.5kg of deionized water and stir to form the water phase; From the oil phase to the water phase and turn on high-speed homogenization to form a stable O/W emulsion; turn on the stirring (maintain 1000 revolutions/min), and then heat the homogenized emulsion to 60°C, while slowly adding 0.5 kg of diethylene Triamine, maintain a stable curing temperature of the capsule wall material for 8 hours, then add 1.0kg of EO/PO block polyether dispersant DP-30, wetting agent NNO 2kg (Shanghai Tiantan Auxiliary Factory), preservative sodium benzoate 0.05 kg, 0.2 kg of organosilicon defoaming agent, stir evenly to obtain 28% chlorpyrifos microcapsule suspension.

[0097] Similarly, use ZPG-150 spray dryer to granulate, control the temperature of the hot air inlet at 70°C, pour 28% chlorpyrifos microcapsule suspension into the slurry storage tank, and pump it into the atomizer through the feed pump to make the slurry After atomization, high-speed rotation is generated in the drying tower, and spherical droplets are formed after rotating and spraying from the atomizer nozzle. After the droplets are heated, the surface moisture evaporates rapidly to form porous solid particles, which are finally dried to form microcapsule granules. Finally, 40 kg of chlorpyrifos microcapsule granules with an appearance of yellow-brown particles, a moisture content of about 2.5% and a content of about 72% are obtained.

[0098] The main technical indicators of the product of the present invention are as follows:

[0099]

[0100] Example three

[0101] The invention has the following advantages because the pesticide is microencapsulated first and then made into granules:

[0102] 1. It inhibits the adverse effects of many environmental factors such as light, heat, air, rain, soil, microorganisms and other chemical substances on the active ingredients of pesticides, reduces the rate of volatilization, decomposition, oxidation, degradation and loss of pesticides, thereby enhancing The stability of pesticides expands the scope of use.

[0103] 2. The content of active ingredients in microcapsule granules is generally between 5% and 75%. Compared with emulsifiable concentrate, the active ingredients are concentrated in the heart of the capsule. Due to the effect of solid particles after use, the adhesion strength is strengthened and it is not easy to volatilize with the solvent, which is also a factor for the improvement of the control effect.

[0104] 3. Reduce the acute toxicity of the original medicine, reduce the irritation to humans and animals, environmental pollution and phytotoxicity to crops, and it is safer and more reliable for humans and animals or the ecological environment.

[0105] 4. After the microencapsulation, the permeability of the active ingredients through the capsule wall material can be controlled artificially, and the slow release rate can be designed in advance. Due to the protection of the capsule skin, the degradation speed of the active ingredients is slowed down, and the duration of pesticides can be extended by 3 to 10 times. Prolonging the effective period can improve the control effect, reduce the frequency of pesticide application and reduce agricultural costs.

[0106] 5. Effectively reduce organic solvents such as toluene and xylene, thereby effectively reducing environmental pollution and reducing the usage of organic solvents.

[0107] 6. Good storage stability and physical and chemical stability, fast disintegration speed of particles and good use effect.

[0108] 7. Compared with wettable powders and suspending agents, the content of active ingredients is high, the relative density of the product is large, and the volume is small, which is convenient for packaging, storage and transportation.