Preparation method of slow-release pesticide

Abstract

The invention relates to the technical field of pesticide preparations, and provides a slow-release pesticide preparation method which comprises the following steps: (1) homogenizing pesticide active ingredients and an emulsifier aqueous solution to form a pesticide-loaded emulsion; (2) dissolving a biodegradable high polymer material in an organic solvent to form a coating phase; (3) dropwise adding the drug-loaded emulsion into the coating phase, and carrying out ultrasonic emulsification to form a W / O emulsion; (4) adding a cross-linking agent under a low-temperature condition for interfacial polymerization; and (5) centrifugally washing and freeze-drying to obtain the sustained-release microcapsule. The particle size of the obtained product is 80-300 [mu] m, the encapsulation efficiency is greater than or equal to 88%, the accumulated release rate in water at 25 DEG C for 30 days is 75-95%, and the lasting period is 3-4 times that of a conventional preparation. The method is suitable for slow-release processing of insecticides, bactericides and herbicides. Through a 4-15 DEG C low-temperature cross-linking process, the decomposition of the heat-sensitive pesticide is effectively inhibited, and the utilization rate of effective components is remarkably improved. A chitosan-PLA composite capsule wall structure is adopted, gradient release is achieved, a chitosan hydrophilic layer is rapidly swelled, 15-20% of the chitosan hydrophilic layer is released within 7 days, and the rapid effect taking requirement is met.

Description

Technical Field

[0001] This invention relates to the field of pesticide formulation technology, specifically a method for preparing a slow-release pesticide. Background Technology

[0002] With the advancement of technology and the development of agriculture, pesticides play a crucial role in ensuring crop yield and quality. However, the overuse of pesticides has led to environmental pollution and food safety risks. Therefore, slow-release pesticides, as a new type of pesticide formulation, have gradually gained attention and favor. Slow-release pesticides refer to pesticides that use natural or synthetic carriers as slow-release materials, combining insecticides, herbicides, and fungicides to create a slow-release formulation. Especially for some highly toxic pesticides, microencapsulation technology can be used to encapsulate them, reducing the frequency of direct contact with pesticides during application and minimizing harm to the human body.

[0003] A search revealed an existing patent (application publication number: CN103688928A) that discloses a slow-release pesticide, comprising: a hydrophobic pesticide agent; and a starch-based capsule encapsulating the hydrophobic pesticide agent, wherein the starch-based capsule is a reaction product of a click reaction between a starch-based surfactant and a thiol compound under photoinitiation.

[0004] In the aforementioned application, the double bonds in the starch-based surfactant and the thiol groups in the thiol compound undergo a click reaction, causing the starch-based surfactant and thiol compound to crosslink and form a starch-based capsule. This starch-based capsule exhibits good water resistance, thus providing the sustained-release pesticide with good rain resistance. Furthermore, the starch-based capsule is biodegradable in the natural environment, making the provided sustained-release pesticide more environmentally friendly; moreover, the raw material cost of the starch-based capsule is low, thereby reducing the production cost of the provided sustained-release pesticide.

[0005] However, the aforementioned patents or traditional pesticide formulations still have the following drawbacks: (1) Low utilization rate: The field utilization rate of conventional formulations is <30%; (2) Environmental pollution: Non-degradable coating materials cause soil residues; (3) Process defects: High-temperature cross-linking leads to pesticide decomposition rate >15%.

[0006] In view of this, the present invention proposes a method for preparing a slow-release pesticide. This solves the problems of non-degradable materials, uncontrollable release, and activity loss caused by high-temperature processes in existing technologies. Summary of the Invention

[0007] This invention proposes a method for preparing slow-release pesticides, which solves the problems of non-degradable materials, uncontrollable release, and loss of activity caused by high-temperature processes in the prior art.

[0008] The technical solution of the present invention is as follows: A method for preparing a slow-release pesticide, comprising the following steps: (a) Mix the pesticide active ingredient, emulsifier and water, and homogenize at 8000-15000 rpm for 1-10 minutes to form a pesticide-loaded emulsion; (b) Dissolve the biodegradable polymer material in an organic solvent to form a coating solution with a mass concentration of 5%-20%; (c) The drug-loaded emulsion obtained in step (a) is added dropwise to the coating solution and ultrasonically emulsified at 100-500W for 1-5 minutes to form a W / O type emulsion; (d) Add crosslinking agent to emulsion and stir the reaction at a low temperature of 4-15℃ for 2-6 hours; (e) After the reaction is completed, the mixture is centrifuged, washed with ethanol and deionized water in sequence, and freeze-dried to obtain sustained-release pesticide microcapsule particles.

[0009] Preferably, the biodegradable polymer material is a composite of at least two of sodium alginate, chitosan, polylactic acid (PLA), and polycaprolactone (PCL), with a composite mass ratio of 1:0.5~2.

[0010] Preferably, the active pesticide ingredient is a pyrethroid insecticide, a triazole fungicide, or a sulfonylurea herbicide, and its loading in the microcapsule is 15%-45%.

[0011] Preferably, the crosslinking agent is glutaraldehyde, calcium chloride, or genipin, and the amount added is 0.5%-8% of the total mass of the biodegradable polymer material.

[0012] Preferably, the stirring speed in step (d) is 200-600 rpm.

[0013] Preferably, the present invention also provides a slow-release pesticide microcapsule. - Particle size distribution is 80-300μm - Encapsulation rate ≥ 88% - In a buffer solution at 25°C and pH 6.5, the cumulative release rate over 30 days is 75%-95%.

[0014] The slow-release pesticide preparation method provided by this invention has the following significant advantages compared with the prior art: 1. Improved pesticide activity protection rate: The low-temperature cross-linking process at 4-15℃ (compared to the traditional high-temperature curing at 50-80℃) effectively inhibits the decomposition of heat-sensitive pesticides. Actual measurements show that the decomposition rate of highly efficient cyhalothrin is ≤3.8% (compared to >22% with the traditional process), and the decomposition rate of difenoconazole is ≤4.5% (compared to >18% with the traditional process), significantly improving the utilization rate of active ingredients.

[0015] 2. Release behavior is precise and controllable: The chitosan-PLA composite capsule structure enables gradient release: the hydrophilic chitosan layer swells rapidly, releasing 15-20% in 7 days to meet the need for rapid onset of action; the hydrophobic PLA layer hydrolyzes slowly, releasing 75-95% cumulatively in 30 days to form long-lasting protection.

[0016] 3. Revolutionary breakthrough in environmental compatibility: Biodegradability: The soil degradation rate of the capsule wall material is ≥92% after 90 days (ISO 17556 standard), reducing the risk of environmental residues compared to polyvinyl alcohol materials (<5%); Ecological safety: Earthworm acute toxicity LC 50 >1000mg / kg (OECD 207), Zebrafish LC 50 =98mg / L (OECD 203), which is superior to the traditional sustained-release formulations of 320mg / kg and 42mg / L.

[0017] 4. Field application benefits are doubled: Extended duration of efficacy: A field trial in Jiangsu rice paddies (2023) showed that the control efficacy against sheath blight reached 89.3% (76.8% for conventional formulations), and the number of applications was reduced from 3 to 1. Overall cost reduction: The amount of pesticide used per mu was reduced by 37.5% (120g → 75g), and the labor cost was reduced by 60% (180 yuan → 60 yuan / mu / season).

[0018] 5. The process has strong universality: It is compatible with water-soluble (thiamethoxam encapsulation rate 91.2%), lipid-soluble (tebuconazole encapsulation rate 93.5%) and photosensitive pesticides (avermectin encapsulation rate 90.1%), and reduces energy consumption by 62% in pilot production (500L reactor). Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a process flow diagram of a slow-release pesticide preparation method proposed in this invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figure 1 As shown in the figure, this embodiment proposes a method for preparing a slow-release pesticide, including the following steps: (a) Mix the pesticide active ingredient, emulsifier and water, and homogenize at 8000-15000 rpm for 1-10 minutes to form a pesticide-loaded emulsion; (b) Dissolve the biodegradable polymer material in an organic solvent to form a coating solution with a mass concentration of 5%-20%; (c) The drug-loaded emulsion obtained in step (a) is added dropwise to the coating solution and ultrasonically emulsified at 100-500W for 1-5 minutes to form a W / O type emulsion; (d) Add crosslinking agent to emulsion and stir the reaction at a low temperature of 4-15℃ for 2-6 hours; (e) After the reaction is completed, the mixture is centrifuged, washed with ethanol and deionized water in sequence, and freeze-dried to obtain sustained-release pesticide microcapsule particles.

[0023] Preferably, the biodegradable polymer material is a composite of at least two of sodium alginate, chitosan, polylactic acid (PLA), and polycaprolactone (PCL), with a composite mass ratio of 1:0.5~2.

[0024] Preferably, the active pesticide ingredient is a pyrethroid insecticide, a triazole fungicide, or a sulfonylurea herbicide, and its loading in the microcapsule is 15%-45%.

[0025] Preferably, the crosslinking agent is glutaraldehyde, calcium chloride, or genipin, and the amount added is 0.5%-8% of the total mass of the biodegradable polymer material.

[0026] Preferably, the stirring speed in step (d) is 200-600 rpm.

[0027] Preferably, the present invention also provides a slow-release pesticide microcapsule. - Particle size distribution is 80-300μm - Encapsulation rate ≥ 88% - In a buffer solution at 25°C and pH 6.5, the cumulative release rate over 30 days is 75%-95%.

[0028] Example 1 (Insecticide Microcapsules) 1. Drug-loaded emulsions: - 12g of high-efficiency cyhalothrin + 3g of Tween-20 + 50mL of water → homogenize at 10000rpm for 5min 2. Encapsulated phase: - 2g chitosan + 2g PLA + 100mL ethyl acetate → Dissolve by magnetic stirring 3. Emulsification: - Add the drug-loaded emulsion dropwise to the coating phase → Sonicate at 300W for 2 minutes 4. Crosslinking: Add 5 mL of 1% glutaraldehyde → Stir at 5℃ for 4 hours (400 rpm). 5. Post-processing: Centrifuge at 10,000 rpm → Wash three times with ethanol → Freeze-dry at -50℃ for 24 hours Results: Encapsulation efficiency 93.2% | Average particle size 182 μm | 30-day release rate 79.6%.

[0029] In this embodiment, a low-temperature crosslinking process of 4-15℃ (compared to the traditional high-temperature curing of 50-80℃) effectively inhibits the decomposition of heat-sensitive pesticides. The measured decomposition rate of lambda-cyhalothrin was ≤3.8% (compared to >22% with the traditional process), and the decomposition rate of difenoconazole was ≤4.5% (compared to >18% with the traditional process), significantly improving the utilization rate of the active ingredients.

[0030] Example 2 (Microcapsules of bactericide) Comparative test 2023 Jiangsu Rice Field Experiment (Sheath Blight Control) In this embodiment, the field application benefits are doubled: the effective period is extended: the Jiangsu rice field trial (2023) showed that the control efficacy against sheath blight reached 89.3% (76.8% for conventional preparations), and the number of applications was reduced from 3 to 1; the overall cost is reduced: the amount of medicine used per mu is reduced by 37.5% (120g→75g), and the labor cost is reduced by 60% (180 yuan→60 yuan / mu·season).

[0031] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a slow-release pesticide, characterized in that, Includes the following steps: (a) Mix the pesticide active ingredient, emulsifier and water, and homogenize at 8000-15000 rpm for 1-10 minutes to form a pesticide-loaded emulsion; (b) Dissolve the biodegradable polymer material in an organic solvent to form a coating solution with a mass concentration of 5%-20%; (c) The drug-loaded emulsion obtained in step (a) is added dropwise to the coating solution and ultrasonically emulsified at 100-500W for 1-5 minutes to form a W / O type emulsion; (d) Add crosslinking agent to emulsion and stir the reaction at a low temperature of 4-15℃ for 2-6 hours; (e) After the reaction is completed, the mixture is centrifuged, washed with ethanol and deionized water in sequence, and freeze-dried to obtain sustained-release pesticide microcapsule particles.

2. The method according to claim 1, characterized in that: The biodegradable polymer material is a composite of at least two of sodium alginate, chitosan, polylactic acid (PLA), and polycaprolactone (PCL), with a composite mass ratio of 1:0.5~2.

3. The method according to claim 1, characterized in that: The active ingredient of the pesticide is a pyrethroid insecticide, a triazole fungicide, or a sulfonylurea herbicide, and its loading in the microcapsule is 15%-45%.

4. The method according to claim 1, characterized in that: The crosslinking agent is glutaraldehyde, calcium chloride, or genipin, and the amount added is 0.5%-8% of the total mass of the biodegradable polymer material.

5. The method according to claim 1, characterized in that: The stirring speed described in step (d) is 200-600 rpm.

6. A sustained-release pesticide microcapsule prepared by any one of claims 1-5, characterized in that: - Particle size distribution is 80-300μm - Encapsulation rate ≥ 88% - In a buffer solution at 25°C and pH 6.5, the cumulative release rate over 30 days is 75%-95%.

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