Environment-friendly pesticide slow-release agent and preparation method thereof

Abstract

The invention relates to an environment-friendly pesticide sustained-release agent, a preparation method and application of the environment-friendly pesticide sustained-release agent in agricultural pest and weed management, and aims to improve the pesticide use efficiency, prolong the action time and remarkably reduce the pollution to the environment at the same time. According to the invention, by selecting the pesticide with strong biological activity and low environmental toxicity as an effective component and using a biodegradable material as a slow-release carrier, slow and continuous release of the effective component of the pesticide is innovatively realized.

Description

Technical Field

[0001] This invention belongs to the field of agricultural chemicals, specifically the development of an environmentally friendly sustained-release pesticide and its application in agricultural pest management. This technology involves the design and preparation of pesticide formulations, aiming to improve pesticide efficiency, extend its duration of action, and significantly reduce pesticide residues in the environment, thereby promoting the sustainable development of agricultural production. Background Art

[0002] With the global population growing and food demand rising, ensuring crop yield and quality has become a crucial task in agricultural production. As a crucial means of protecting crops and controlling pests and diseases, the rational use of pesticides is directly related to agricultural production efficiency and environmental sustainability. However, traditional pesticide formulations, due to their rapid release and high loss rates, not only lead to inefficient pesticide use but also exacerbate environmental pollution, such as pesticide residues in soil and water, and potential threats to non-target organisms.

[0003] To address these issues, pesticide slow-release technology has emerged. By modifying the release dynamics of pesticides, this technology allows them to be released slowly and continuously onto crops or pests over a defined period of time. This improves pesticide utilization efficiency, reduces application frequency, and helps mitigate environmental pollution. However, existing slow-release pesticide formulations often rely on difficult-to-degrade synthetic polymers as carriers. While this achieves the desired slow-release effect, it still carries a risk of environmental residue and contamination.

[0004] Therefore, developing a new, environmentally friendly, slow-release pesticide formulation using biodegradable materials as a carrier, which not only effectively releases the pesticide but also naturally degrades after use, significantly reducing its environmental impact, is a key area of ​​current pesticide formulation research. Furthermore, by precisely controlling the release rate and duration of the pesticide, it is possible to further enhance its effectiveness on target crops or pests and reduce its impact on non-target organisms, thereby promoting ecological and sustainable agricultural development while ensuring agricultural yield and quality.

[0005] To address the shortcomings of existing technologies, this invention provides a novel, environmentally friendly sustained-release pesticide formulation and its preparation method. By using biodegradable materials as carriers, this formulation aims to achieve slow and sustained release of the pesticide while ensuring environmental safety and eco-friendliness after use. The successful application of this technology will provide a more efficient and environmentally friendly solution for modern agricultural pest management, and will be of great significance in promoting the green transformation of agricultural production methods and improving the sustainability of agricultural production. Summary of the Invention

[0006] This invention aims to provide an environmentally friendly sustained-release pesticide and its preparation method to address the high environmental pollution risks, low efficiency, and potential threats to non-target organisms associated with existing pesticide applications. By utilizing a biodegradable material as a sustained-release carrier for the pesticide, this invention achieves sustained release while ensuring environmental safety and eco-friendliness after use.

[0007] In order to achieve the above object, the present invention proposes the following technical solutions: An environmentally friendly pesticide slow-release agent, comprising a pesticide active ingredient and a slow-release carrier; the slow-release carrier is a PLA-PCL copolymer; the pesticide active ingredient comprises an insecticide, a fungicide or a herbicide; The PLA-PCL copolymer of the present invention is prepared by ring-opening polymerization of lactide and caprolactone, wherein the mass ratio of lactide to caprolactone is (9:1)-(5:1); preferably, the mass ratio of lactide to caprolactone is 8:2.

[0008] The active ingredient of the pesticide is imidacloprid, pyraclostrobin or bensulfuron-methyl.

[0009] The pesticide slow-release agent is in the form of granules, microspheres, tablets or any other form suitable for agricultural applications, preferably microspheres.

[0010] The preparation method of the environmentally friendly pesticide slow-release agent of the present invention comprises the following steps: (1) adding lactide and caprolactone, a catalyst stannous octoate and an initiator 1,4-butanediol into a dry reaction vessel, vacuum drying, and heating the reaction under argon protection to prepare a PLA-PCL copolymer; (2) preparing slow-release microspheres by an O / W emulsification-solvent evaporation method.

[0011] The O / W emulsification-solvent evaporation method of the present invention comprises the following steps: adding a carrier and an active ingredient to dichloromethane to form an organic phase; weighing a surfactant, Tween 20, and dissolving it in ultrapure water, heating and stirring at 40°C to prepare an aqueous solution of a certain concentration, i.e., the aqueous phase; slowly adding the organic phase dropwise to the aqueous phase under stirring, stirring evenly, and then ultrasonically emulsifying the mixture; magnetically stirring at room temperature overnight to completely evaporate the organic solvent; collecting the microspheres by centrifugation, repeatedly washing with ultrapure water to remove the surfactant, and vacuum freeze-drying to obtain powdered solid microspheres.

[0012] The pesticide slow-release agent of the present invention is used for preventing and controlling crop diseases, insect pests or weed pests.

[0013] The environmentally friendly pesticide slow-release agent of the present invention has the following technical effects: Through sustained-release technology, pesticides can be continuously released in the target area, which prolongs the duration of action of the pesticides, reduces the number of applications, and improves the efficiency of pesticide use.

[0014] Biodegradable materials are used as carriers. After the use of pesticides, the carriers can be degraded under natural conditions, reducing pollution to the soil and water bodies and lowering the risk of environmental pollution.

[0015] The present invention uses a PLA-PCL copolymer as a sustained-release carrier, and the encapsulation efficiency and drug loading of the prepared sustained-release microspheres are significantly improved. The reason is speculated to be that the introduction of the flexible chain segment PCL into the carrier material can, on the one hand, improve the brittleness and poor toughness of PLA and prevent damage; on the other hand, it increases the structural domain in the carrier material that binds to the drug, thereby increasing the encapsulation efficiency and drug loading. DETAILED DESCRIPTION

[0016] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0017] The present invention will be further explained below with reference to specific embodiments.

[0018] Example In order to further verify the effect of the present invention, the following examples were carried out: 1. Preparation of sustained-release carrier Preparation of modified polylactic acid: PLA-PCL copolymer A total of 10 g of lactide LA and caprolactone CL, 10 mg of catalyst stannous octoate, and 10 mg of initiator 1,4-butanediol were added to a dry round-bottom flask. After vacuum drying at 30 °C for 2.0 h, the temperature was raised to 150 °C under argon protection and the reaction was carried out for 6 h. After the reaction, the crude product was dissolved in an appropriate amount of chloroform and then precipitated in a large amount of anhydrous ethanol. The precipitate was vacuum dried at 60 °C for 24 h to obtain a copolymer.

[0019] Table 1 Mass ratio of monomers in copolymers

[0020] Preparation of polylactic acid: PLA 10 g of lactide LA, 5 mg of catalyst stannous octoate, and 5 mg of initiator 1,4-butanediol were added to a dry round-bottom flask. After vacuum drying at 30 °C for 2.0 h, the temperature was raised to 150 °C under argon protection and the reaction was carried out for 6 h. After the reaction, the crude product was dissolved in an appropriate amount of chloroform and then precipitated in a large amount of anhydrous ethanol. The precipitate was vacuum dried at 60 °C for 24 h to obtain a copolymer.

[0021] Preparation of polycaprolactone: PCL 10 g of caprolactone CL, 5 mg of catalyst stannous octoate, and 5 mg of initiator 1,4-butanediol were added to a dry round-bottom flask and vacuum dried at 30 °C for 2.0 h. The temperature was then raised to 150 °C under argon protection and reacted for 6 h. After the reaction, the crude product was dissolved in an appropriate amount of chloroform and then precipitated in a large amount of anhydrous ethanol. The precipitate was vacuum dried at 60 °C for 24 h to obtain a copolymer.

[0022] 2. Preparation of sustained-release microspheres Polylactic acid microspheres were prepared using the O / W emulsification-solvent evaporation method: 2 g of carrier and 1 g of active ingredient were added to 400 mL of dichloromethane to form the organic phase. 20 g of the surfactant Tween 20 was accurately weighed and dissolved in 4000 mL of ultrapure water. The solution was heated and stirred at 40°C to dissolve to form an aqueous solution of a certain concentration, i.e., the aqueous phase. The organic phase was slowly added dropwise to the aqueous phase under stirring. After uniform stirring, the solution was ultrasonically emulsified for 15 minutes and magnetically stirred at room temperature overnight to completely evaporate the organic solvent. The microspheres were collected by centrifugation, repeatedly washed with ultrapure water to remove the surfactant, and then freeze-dried in a vacuum to obtain powdered solid microspheres.

[0023] 3. Determination of drug loading and encapsulation efficiency of imidacloprid sustained-release microspheres Accurately weigh 0.01 g of powdered solid microspheres, dissolve them in dichloromethane, evaporate the solvent, dissolve them in acetonitrile and make up to 10 mL, filter them through a 0.22 μm filter membrane, and determine the concentration of imidacloprid in the filtrate by high performance liquid chromatography (HPLC) with an external standard method.

[0024] Drug loading = mass of imidacloprid in microspheres / total mass of microspheres × 100%; Encapsulation efficiency = mass of imidacloprid in microspheres / actual mass of imidacloprid added × 100%.

[0025] Table 2: Performance test of Imidacloprid sustained-release microspheres

[0026] As shown in Table 2, when PLA or PCL was used as the sustained-release carrier in the imidacloprid sustained-release microspheres, the encapsulation efficiency and drug loading of the microspheres were low, ranging from 60% to 70% and from 20% to 22%. Using modified polylactic acid (PLA-PCL copolymer) as the sustained-release carrier significantly improved the encapsulation efficiency and drug loading, ranging from 70% to 90% and from 26% to 33%. In particular, PLA-PCL-2, when used as the sustained-release carrier, achieved an encapsulation efficiency of 88.4% and a drug loading of 32.1%, significantly different from the other test groups. This is hypothesized to occur because the introduction of the flexible PCL segment into the carrier material not only mitigates the brittleness and poor toughness of PLA, preventing breakage, but also increases the number of drug-binding domains within the carrier material, thereby increasing the encapsulation efficiency and drug loading.

[0027] 4. Determination of drug loading and encapsulation efficiency of pyraclostrobin sustained-release microspheres Accurately weigh 0.01 g of powdered solid microspheres, dissolve them in dichloromethane, evaporate the solvent, dissolve them in acetonitrile and make up to 10 mL, filter them through a 0.22 μm filter membrane, and determine the concentration of pyraclostrobin in the filtrate by high performance liquid chromatography (HPLC) external standard method.

[0028] Drug loading = mass of pyraclostrobin in microspheres / total mass of microspheres × 100%; Encapsulation efficiency = mass of pyraclostrobin in microspheres / mass of pyraclostrobin actually added × 100%.

[0029] Table 3: Performance test of pyraclostrobin sustained-release microspheres

[0030] As can be seen from Table 3, when PLA or PCL is used as the sustained-release carrier in pyraclostrobin sustained-release microspheres, the encapsulation efficiency and drug loading of the microspheres are low, with the encapsulation efficiency ranging from 60-65% and the drug loading ranging from 18-20%. When modified polylactic acid (PLA-PCL copolymer) is used as the sustained-release carrier, the encapsulation efficiency and drug loading are significantly improved, with the encapsulation efficiency ranging from 71-83% and the drug loading ranging from 22-28%. In particular, when PLA-PCL-2 is used as the sustained-release carrier, its encapsulation efficiency is 82.2 and the drug loading is 27.5%, which are significantly different from those of the other test groups.

[0031] 5. Determination of drug loading and encapsulation efficiency of bensulfuron-methyl sustained-release microspheres Accurately weigh 0.01 g of powdered solid microspheres, dissolve them in chloroform, evaporate the solvent, dissolve them in acetonitrile and make up to 10 mL, filter them through a 0.22 μm filter membrane, and determine the concentration of bensulfuron-methyl in the filtrate by high performance liquid chromatography (HPLC) with an external standard method.

[0032] Drug loading = mass of bensulfuron-methyl in microspheres / total mass of microspheres × 100%; Encapsulation efficiency = mass of bensulfuron-methyl in microspheres / actual mass of bensulfuron-methyl added × 100%.

[0033] Table 4: Performance test of bensulfuron-methyl sustained-release microspheres

[0034] As shown in Table 4, when PLA or PCL was used as the sustained-release carrier in bensulfuron-methyl sustained-release microspheres, the encapsulation efficiency and drug loading of the microspheres were low, with the encapsulation efficiency ranging from 63-67% and the drug loading ranging from 22-25%. When modified polylactic acid (PLA-PCL copolymer) was used as the sustained-release carrier, the encapsulation efficiency and drug loading were significantly improved. In particular, when PLA-PCL-2 was used as the sustained-release carrier, its encapsulation efficiency was 85.0 and the drug loading was 31.3%, which were significantly different from those of the other test groups.

[0035] 6. Field application trials have shown that compared with traditional insecticides, this slow-release agent has a more lasting effect in controlling similar pests, reducing the number of applications by 50% and increasing crop yields by 15%.

[0036] 7. In its application in rice fields, compared with traditional herbicides, the slow-release agent not only effectively controls weeds in the fields, but also significantly reduces pollution to the water environment. The water quality test results of farmland water bodies show that pesticide residues are reduced by 60%.

[0037] in conclusion The environmentally friendly pesticide sustained-release agent and preparation method provided by the present invention, by using biodegradable materials as carriers, not only achieves the sustained release of pesticides and improves the use efficiency, but also significantly reduces the risk of environmental pollution and protects non-target organisms.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same.

Claims

1. An environmentally friendly pesticide slow-release agent, characterized in that: It comprises a pesticide active ingredient and a slow-release carrier; the slow-release carrier is a PLA-PCL copolymer; the pesticide active ingredient comprises an insecticide, a fungicide or a herbicide; The PLA-PCL copolymer is prepared by ring-opening polymerization of lactide and caprolactone, wherein the mass ratio of lactide to caprolactone is (9:1)-(5:1).

2. The environmentally friendly pesticide slow-release agent according to claim 1, characterized in that The active ingredients of the pesticides are imidacloprid, pyraclostrobin or benzylsulfuron-methyl.

3. The environmentally friendly pesticide slow-release agent according to claim 1 or 2, characterized in that: The mass ratio of lactide to caprolactone is 8:

2.

4. The environmentally friendly pesticide slow-release agent according to any one of claims 1 to 3, characterized in that: The dosage form is: granules, microspheres, tablets or any other form suitable for agricultural application.

5. The environmentally friendly pesticide slow-release agent according to claim 4, characterized in that: Its dosage form is microspheres.

6. The method for preparing the environmentally friendly sustained-release pesticide according to claim 5, characterized in that: The method comprises the following steps: (1) adding lactide and caprolactone, a catalyst stannous octoate and an initiator 1,4-butanediol into a dry reaction vessel, vacuum drying, and heating the reaction under argon protection to prepare a PLA-PCL copolymer; and (2) preparing sustained-release microspheres by an O / W emulsification-solvent evaporation method.

7. The preparation method according to claim 6, characterized in that The O / W emulsification-solvent evaporation method comprises the following steps: The carrier and active ingredient are added to dichloromethane to form an organic phase; the surfactant Tween 20 is weighed and dissolved in ultrapure water, heated and stirred at 40°C to dissolve to prepare an aqueous solution of a certain concentration, i.e., the aqueous phase; under stirring, the organic phase is slowly added dropwise to the aqueous phase, stirred evenly, and then ultrasonically emulsified. Magnetic stirring is carried out at room temperature overnight to allow the organic solvent to completely evaporate. The microspheres are collected by centrifugation, repeatedly washed with ultrapure water to remove the surfactant, and vacuum freeze-dried to obtain powdered solid microspheres.

8. Use of the slow-release pesticide according to claim 1 for preventing and controlling crop diseases, insect pests or weed pests.

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