Safe butachlor-oxadiargyl microcapsule suspending agent and preparation method thereof

Abstract

The invention discloses a safe butachlor-oxadiargyl microcapsule suspending agent and a preparation method thereof in the field of herbicides. The safe butachlor-oxadiargyl microcapsule suspending agent comprises the following components in parts by weight: 3-5 parts of modified polylactic acid, 25-30 parts of butachlor, 1-3 parts of oxadiargyl, 15-20 parts of a dispersing agent, 1-2 parts of an anti-freezing agent, 3-5 parts of a thickening agent, 0.5-1 part of a preservative and 30-50 parts of water. Modified polylactic acid is adopted as a micelle wall material, so that the stability and release control capability of the microcapsule are improved, butachlor and oxadiargyl can be uniformly coated into the microcapsule, nano-particles are formed, the dispersity and stability of active ingredients are improved, and the bioavailability of the microcapsule is improved. The microencapsulation technology effectively reduces the toxicity and volatility of the pesticide, and improves the environmental friendliness and use safety.

Description

Technical Field

[0001] This invention belongs to the field of herbicide technology, specifically referring to a safe butachlor-propyne oxadiazon microcapsule suspension and its preparation method. Background Technology

[0002] The sustainable utilization of the black soil in Northeast China has become a major national need. The typical black soil region of Northeast China covers approximately 278 million mu (18.9 million hectares), responsible for a quarter of the nation's grain output, one-third of its marketable grain, and half of its japonica rice production, making it a core production area for ensuring China's food security. However, long-term high-intensity farming has led to an average annual erosion of 0.1-0.5 cm of the black soil layer, a decrease of one-third in the organic matter content of the topsoil compared to the initial reclamation period, with some areas experiencing a decrease of up to 50%, and soil erosion affecting over 20% of the area.

[0003] Propylene oxadiazon and butachlor are two commonly used herbicides in agricultural production. The pharmacological mechanism of propylene oxadiazon involves its role as a protoporphyrinogen oxidase (PPO) inhibitor. This compound affects cell membrane and chlorophyll metabolism by inhibiting the normal function of the enzyme. Protoporphyrinogen oxidase is involved in the crucial process of chlorophyll synthesis in plants; therefore, inhibiting this enzyme leads to chlorophyll decomposition, cell membrane rupture, and damage to meristematic tissues. The pharmacological mechanism of butachlor involves its role as an amide herbicide. This class of herbicides primarily works by inhibiting the synthesis of proteases in weed seedlings. Proteases are key enzymes for plant cell growth and metabolism; their inhibition hinders normal plant cell growth, particularly affecting the normal development of seedlings and roots. Amide and oxadiazon herbicides may pose persistent problems in soil and water.

[0004] On the one hand, the long-term residues of herbicides and their decomposition products in the soil may affect the diversity and activity of soil microorganisms, thereby disrupting the balance of the soil ecosystem. In the black soil region of Northeast China, eight typical herbicide residues have been detected, and their decomposition products inhibit the activity of carbohydrate-containing enzymes and the accumulation of carbon in microbial residues, leading to disordered soil carbon metabolism. For example, butachlor has a half-life of approximately 30 days in the soil and a residual effect of up to 6 weeks; its residues inhibit functional microbial communities such as nitrogen-fixing bacteria and phosphate-solubilizing bacteria, weakening the soil's nutrient cycling capacity.

[0005] On the other hand, long-term herbicide residues alter soil colloidal properties, reducing the stability of black soil aggregates and exacerbating the risk of wind and water erosion. In northeastern China, the use of traditional herbicides on farmland increased runoff by 15-20% and sediment loss by 30-40%. These chemicals can also enter water bodies through runoff, causing water pollution and affecting the growth and development of aquatic organisms. Herbicides enter the Songhua River and Liao River basins through runoff, leading to changes in the structure of aquatic communities. For example, the acute toxicity LC50 value of propyzinazole to fish is less than 1 mg / L, posing a high risk to aquatic ecosystems.

[0006] Furthermore, some herbicides are highly volatile and may spread through the atmosphere, causing pollution over a wider area. Herbicide application in the field is greatly affected by climatic conditions; sunlight, rain, and temperature can all accelerate herbicide decomposition and reduce their effectiveness. For example, under high temperatures and ultraviolet radiation, some amide and oxadiazon herbicides will rapidly lose their effectiveness, failing to provide sustained weed control. Additionally, soil microorganisms may accelerate herbicide degradation, posing a new challenge to their sustained efficacy. Therefore, it is essential to develop herbicide formulations that can remain stable under various environmental conditions. Traditional liquid or solid forms of herbicides can easily cause direct contact during application, threatening the health of users and leading to skin allergies, respiratory problems, and even more serious poisoning risks. Furthermore, herbicides can be wind-borne to nearby non-target plants or crops, causing indirect harm, resulting in crop losses and secondary environmental pollution. These technical challenges need to be addressed by improving formulations, enhancing application precision, and adhering to safe operating procedures. Long-term and monotonous use of a single type of herbicide can easily lead to weed resistance to that herbicide. Once weeds develop resistance, conventional doses of herbicides become ineffective in controlling their growth, sometimes necessitating increased dosages or a change in herbicide type. This not only increases weeding costs but also exacerbates environmental and health risks. Therefore, developing diversified and combined herbicide formulations has become an important direction for addressing this problem. The high frequency and dosage of traditional herbicides not only increase pesticide costs but also the labor involved in application, indirectly raising agricultural production costs. Multiple applications can also interfere with crop growth. Therefore, providing a herbicide formulation that is effective for a long time and requires only a single application can significantly improve economic efficiency and reduce resource waste.

[0007] The degradation of black soil directly leads to a decline in the yield of crops such as corn and soybeans. Data from the Heilongjiang Academy of Agricultural Sciences shows that for every 1 centimeter decrease in the thickness of the black soil layer, the yield of corn per mu (a Chinese unit of area, approximately 0.067 hectares) decreases by 20-30 kilograms. If no measures are taken, it is estimated that grain production in Northeast China will decrease by more than 15% by 2030. Summary of the Invention

[0008] To address the above issues and overcome the shortcomings of existing technologies, this invention provides a safe butachlor-propyne oxadiazon microcapsule suspension and its preparation method. This invention utilizes modified polylactic acid as the micelle wall material, improving the stability and release control of the microcapsules. During the preparation of the modifier, a series of chemical reactions, including esterification and sulfonylation, increase the reactivity and compatibility of the material. High shear force and vacuum distillation methods ensure that butachlor and propyne oxadiazon are uniformly encapsulated within the microcapsules, forming nanoparticles and improving the dispersibility and stability of the active ingredients. High-speed shearing and nano-sizing processes result in drug particles with a high surface area, thereby enhancing drug efficacy. Microencapsulation technology effectively reduces the toxicity and volatility of pesticides, improving environmental friendliness and safety. The polylactic acid wall material endows the microcapsules with excellent controlled release characteristics, allowing for more effective release of the active ingredients in the target area and prolonging the efficacy. The prepared microcapsule suspension exhibits better dispersibility and stability, is easy to store and use, and is less prone to sedimentation or stratification.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention proposes a safe butachlor·propyne oxadiazon microcapsule suspension, wherein the microcapsule suspension comprises the following components in parts by weight: 3-5 parts modified polylactic acid, 25-30 parts butachlor, 1-3 parts propyne oxadiazon, 15-20 parts dispersant, 1-2 parts antifreeze, 3-5 parts thickener, 0.5-1 part preservative, and 30-50 parts water;

[0010] Preferably, the dispersant comprises at least one of polyethylene glycol, sodium polyacrylate, octylphenol polyoxyethylene ether, and sodium dodecylbenzene sulfonate;

[0011] Preferably, the antifreeze agent includes at least one of glycerin, propylene glycol, and ethylene glycol;

[0012] Preferably, the thickener includes at least one of sodium carboxymethyl cellulose, xanthan gum, and hydroxyethyl cellulose;

[0013] Preferably, the preservative includes at least one of sodium benzoate, methylisothiazolinone, and phenoxyethanol;

[0014] Preferably, the raw materials for preparing the modified polylactic acid include the following components in parts by weight: 10 parts L-lactic acid, 1.45-1.55 parts acryloyl chloride, and 4.3-4.5 parts modifier;

[0015] Preferably, the preparation method of the modifier specifically includes the following steps:

[0016] S1. Maleic anhydride and 3-dimethylamino-1-propanol were dissolved in tetrahydrofuran. The reaction temperature was increased and the reaction was refluxed. After the reaction was completed, an activator was added for activation treatment. After the reaction was completed, triethylamine was added to remove the reaction byproducts. After purification, intermediate 1 was obtained.

[0017] Preferably, in step S1, the mass ratio between maleic anhydride and 3-dimethylamino-1-propanol is 1:1.05-1.6;

[0018] Preferably, in step S1, the reflux reaction temperature is 70-90℃ and the reflux reaction time is 1-2h;

[0019] Preferably, in step S1, the activator includes at least one of DCC, CDMT (N,N'-carbonyldiimidazole), and NMM (N-methylmorpholine);

[0020] Preferably, in step S1, the mass ratio of maleic anhydride, CDMT and NMM is 1:1.8-2:1.04-1.16;

[0021] Preferably, in step S1, the activation temperature is 0-5℃ and the activation time is 60-90 min;

[0022] S2. Dissolve intermediate 1 prepared in step S1 in tetrahydrofuran, add p-toluenesulfonic acid, mix well, add 3-dimethylamino-1-propanol, raise the reaction temperature to reflux reaction, after the reaction is completed, adjust the reaction system to neutral, add dichloromethane for extraction, collect the organic phase, dry with anhydrous magnesium sulfate, concentrate and purify to obtain intermediate 2.

[0023] Preferably, in step S2, the amount of p-toluenesulfonic acid added is 5%-10% of the mass of maleic anhydride;

[0024] Preferably, in step S2, the reflux reaction temperature is 65-75°C, and the reflux reaction time is 2-4 hours.

[0025] S3. Dissolve intermediate 2 prepared in step S2 in ethyl acetate, add 1,3-propanesulfonyl lactone and mix, then raise the reaction temperature and reflux the reaction. After the reaction is completed, filter, wash with ethyl acetate and diethyl ether, rotary evaporate, purify, and dry to obtain the modifier.

[0026] Preferably, in step S3, the mass ratio between maleic anhydride and 1,3-propanesulfonyl lactone is 1:2.5-2.75;

[0027] Preferably, in step S3, the reflux reaction temperature is 70-90℃ and the reflux reaction time is 12-18h;

[0028] Preferably, the preparation method of the modified polylactic acid specifically includes the following steps:

[0029] S4. Place L-lactic acid in a flask, add carboxyl activator and catalyst, raise the temperature to 130-140℃, react for 1.5-2.5h, then raise the temperature to 170-180℃, adjust the pressure in the reaction system to 100-200Pa, and continue the reaction for 4-6h. Add dichloromethane to dissolve the reactants, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind and dry to obtain oligomeric polylactic acid.

[0030] Preferably, in step S4, the added mass of the carboxyl activator is 0.08-0.1% of the mass of L-lactic acid, and the carboxyl activator includes at least one of methanesulfonic acid, toluenesulfonic acid, sulfosuccinic acid, p-toluenesulfonyl chloride, and p-toluenesulfonic acid.

[0031] Preferably, in step S4, the mass of the catalyst added is 0.1-0.2% of the mass of L-lactic acid, and the catalyst includes at least one of stannous chloride, stannous oxide, and dibutyltin dilaurate;

[0032] S5. Dissolve the oligomeric polylactic acid prepared in step S4 in dichloromethane, place it in an ice-water bath, add triethylamine and mix well, then add acryloyl chloride dropwise. After the addition is complete, raise the reaction temperature and stir the reaction. After the reaction is complete, filter to remove impurities, wash with saturated sodium carbonate aqueous solution and saturated sodium chloride aqueous solution in sequence, collect the organic phase, dry with anhydrous sodium sulfate, rotary evaporate, and purify to obtain double bond modified polylactic acid.

[0033] Preferably, in step S5, the added triethylamine is 16.2%-17.2% of the mass of L-lactic acid;

[0034] Preferably, in step S5, the reaction temperature of the stirring reaction is 30-40℃, and the stirring reaction time is 12-18h;

[0035] S6. Dissolve the double-bond modified polylactic acid prepared in step S5 in dichloromethane, add the modifier prepared in step S3, mix well, add the initiator, raise the reaction temperature to carry out the modification reaction, and after the reaction is completed, filter, dry and purify to obtain modified polylactic acid.

[0036] Preferably, in step S6, the mass of the initiator added is 0.4%-0.5% of the mass of the modifier;

[0037] Preferably, in step S6, the reaction temperature of the modification reaction is 80-100℃, and the reaction time of the modification reaction is 4-6h;

[0038] This invention also provides a method for preparing a safe butachlor-propyne oxadiazon microcapsule suspension, specifically comprising the following steps:

[0039] ① Dissolve modified polylactic acid in ethyl acetate, add butachlor and propyzoxystrobin, mix well, and obtain the oil phase;

[0040] ② The oil phase prepared in step ① is added to deionized water, subjected to high-speed shear mixing, vacuum distillation, washing and drying to obtain pesticide nanoparticles;

[0041] ③ After mixing the pesticide nanoparticles, dispersant, antifreeze, thickener and preservative prepared in step ② evenly in deionized water, a microcapsule suspension is obtained.

[0042] The beneficial effects achieved by this invention are as follows:

[0043] This invention provides a safe butachlor-propyne oxadiazon microcapsule suspension and its preparation method. By using modified polylactic acid as the micelle wall material, the stability and release control of the microcapsules are improved. During the preparation of the modifier, a series of chemical reactions, including esterification and sulfonylation, increase the reactivity and compatibility of the material. High shear force and vacuum distillation methods allow butachlor and propyne oxadiazon to be uniformly encapsulated into the microcapsules, forming nanoparticles, thus improving the dispersibility and stability of the active ingredients. High-speed shearing and nano-sizing processes result in drug particles with a high surface area, thereby improving drug efficacy. Microencapsulation technology effectively reduces the toxicity and volatility of pesticides, improving environmental friendliness and safety. The polylactic acid wall material endows the microcapsules with excellent controlled release characteristics, allowing for more effective release of the active ingredients in the target area and prolonging the efficacy. The prepared microcapsule suspension has better dispersibility and stability, is easy to store and use, and is less prone to precipitation or stratification. In this invention, modified PLA is used as the microcapsule wall material, and a "ester bond-acryloyl bond-modifier" copolymer structure is used to achieve dual encapsulation of butachlor and propyzoxystrobin. The microcapsules form a stable and dense polymer network on their surface in the aqueous phase, slowing down the initial release rate of the active ingredients and enabling sustained release of effective concentrations for up to several weeks. The combination of high-speed shearing and microencapsulation technology results in nanoscale particles with a large specific surface area and uniform particle size distribution, further extending the overall release cycle while ensuring rapid efficacy. The slow-release system reduces the rapid hydrolysis and photodegradation of the active ingredients, increases the field residual effect, reduces the frequency of repeated applications, and provides a smooth controlled-release curve, maintaining effective concentrations on crop leaves or rhizospheres for extended periods, thus improving the killing efficiency against target weeds and reducing the overall dosage. The biodegradability of the microcapsule wall polymer allows the residues to be decomposed by soil microorganisms after release, reducing long-term soil accumulation and secondary pollution. The slow-release system also reduces... The reduced dissolution rate of active ingredients in water significantly lowers the toxicity risk to non-target organisms (such as fish and aquatic plants) from runoff and leaching. Encapsulating relatively highly toxic active ingredients within a polymer network reduces dust and vapor volatilization, lowering occupational exposure risks during spraying or mixing. Microencapsulation reduces direct contact with active ingredients, improving both acute and subacute toxicity to non-target organisms such as bees and natural enemies. The addition of low-toxicity antifreeze agents like glycerol and highly efficient thickeners like CMC-Na ensures the formulation remains stable in suspension within a temperature range of -5 to 40°C, without crystallization, stratification, or severe sedimentation. Broad-spectrum preservatives such as sodium benzoate guarantee the formulation's microbial safety for over 6 months at room temperature, eliminating performance degradation caused by mold and bacterial growth. The microencapsulation structure effectively extends the soil dissipation half-life of herbicides while reducing initial release, significantly lowering the risk of soil microbial exposure. Microcapsules form a "smart release system" in the soil, with slow release of the active ingredient reducing direct harm to soil animals such as earthworms. Attached Figure Description

[0044] Figure 1 The graph shows the drug loading capacity of the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-2 of this invention.

[0045] Figure 2 The graphs show the wetting properties of the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-2 of this invention.

[0046] Figure 3 The diagram shows the pot experiment efficacy results of the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-2 of this invention.

[0047] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0050] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0051] Example 1

[0052] This embodiment provides a safe butachlor-propyne oxadiazon microcapsule suspension, which comprises the following components in parts by weight: 3 parts modified polylactic acid, 25 parts butachlor, 1 part propyne oxadiazon, 15 parts octylphenol polyoxyethylene ether, 1 part glycerol, 3 parts sodium carboxymethyl cellulose, 0.5 parts sodium benzoate, and 50 parts water.

[0053] The raw materials for preparing modified polylactic acid include the following components in parts by weight: 10 parts L-lactic acid, 1.45 parts acryloyl chloride, and 4.3 parts modifier;

[0054] The preparation method of the modifier specifically includes the following steps:

[0055] S1. Dissolve 5.00 g of maleic anhydride and 5.26 g of 3-dimethylamino-1-propanol in 150 mL of tetrahydrofuran. Raise the reaction temperature to 80 °C and reflux for 1 h. After the reaction is complete, add 9.0 g of CDMT and 5.2 g of NMM and place at 0 °C for activation treatment for 60 min. After the reaction is complete, add triethylamine to remove reaction byproducts. After purification, intermediate 1 is obtained.

[0056] S2. Dissolve intermediate 1 prepared in step S1 in 100 mL of tetrahydrofuran, add 0.25 g of p-toluenesulfonic acid, mix well, add 5.26 g of 3-dimethylamino-1-propanol, raise the reaction temperature to 65 °C, and reflux for 3 h. After the reaction is complete, adjust the reaction system to neutral, add dichloromethane for extraction, collect the organic phase, dry it with anhydrous magnesium sulfate, concentrate and purify it to obtain intermediate 2.

[0057] S3. Dissolve intermediate 2 prepared in step S2 in 100 mL of ethyl acetate, add 12.46 g of 1,3-propanesulfonyl lactone and mix, raise the reaction temperature to 80 °C and reflux for 12 h. After the reaction is completed, filter, wash with ethyl acetate and diethyl ether, rotary evaporate, purify, and dry to obtain the modifier.

[0058] The preparation method of modified polylactic acid specifically includes the following steps:

[0059] S4. Accurately weigh 10g of L-lactic acid and place it in a flask. Add 0.1g of p-toluenesulfonic acid and 0.1g of stannous chloride. Stir the mixture at 200rpm and raise the temperature to 140℃. After reacting for 2 hours, raise the temperature to 180℃ and adjust the pressure in the reaction system to 200Pa. Continue reacting for 6 hours. After the reaction system cools to room temperature, add dichloromethane to dissolve the reaction product, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind it, and place it in a vacuum drying oven at 60℃ for 24 hours to obtain low molecular weight polylactic acid powder.

[0060] S5. Dissolve the oligomeric polylactic acid prepared in step S4 in 50 mL of dichloromethane, place it in an ice-water bath, add 1.62 g of triethylamine and mix well, then add 1.45 g of acryloyl chloride dropwise. After the addition is complete, raise the reaction temperature to 30 °C and stir the reaction for 18 h. After the reaction is complete, filter to remove impurities, wash with saturated sodium carbonate aqueous solution and saturated sodium chloride aqueous solution in sequence, collect the organic phase, dry with anhydrous sodium sulfate, rotary evaporate, and purify to obtain double bond modified polylactic acid.

[0061] S6. Dissolve the double-bond modified polylactic acid prepared in step S5 in 100 mL of dichloromethane, add 4.3 g of the modifier prepared in step S3, mix well, add 21.5 mg of BPO (benzoyl peroxide), raise the reaction temperature to 90 °C to carry out the modification reaction, and after the reaction is completed, filter, dry and purify to obtain modified polylactic acid;

[0062] This embodiment also provides a method for preparing a safe butachlor·propycinoxaflutole microcapsule suspension, specifically including the following steps:

[0063] ① Dissolve modified polylactic acid in 100 mL of ethyl acetate, add butachlor and propyzoxystrobin, mix well, and obtain the oil phase;

[0064] ② The oil phase prepared in step ① is added to 200 mL of deionized water and mixed by high-speed shearing at 10000 rpm. After vacuum distillation, washing and drying, pesticide nanoparticles are obtained.

[0065] ③ After mixing the pesticide nanoparticles, dispersant, antifreeze, thickener and preservative prepared in step ② evenly in deionized water, a microcapsule suspension is obtained.

[0066] Example 2

[0067] This embodiment provides a safe butachlor-propyne oxadiazon microencapsulated suspension, which comprises the following components in parts by weight: 4 parts modified polylactic acid, 27 parts butachlor, 3 parts propyne oxadiazon, 20 parts polyethylene glycol 400, 2 parts propylene glycol, 4 parts sodium carboxymethyl cellulose, 0.8 parts methylisothiazolinone, and 40 parts water.

[0068] The raw materials for preparing modified polylactic acid include the following components in parts by weight: 10 parts L-lactic acid, 1.5 parts acryloyl chloride, and 4.4 parts modifier;

[0069] The preparation method of the modifier specifically includes the following steps:

[0070] S1. Dissolve 5.00 g of maleic anhydride and 6.28 g of 3-dimethylamino-1-propanol in 150 mL of tetrahydrofuran. Raise the reaction temperature to 90 °C and reflux for 1.5 h. After the reaction is complete, add 9.5 g of CDMT and 5.5 g of NMM and place at 4 °C for activation treatment for 90 min. After the reaction is complete, add triethylamine to remove reaction byproducts. After purification, intermediate 1 is obtained.

[0071] S2. Dissolve intermediate 1 prepared in step S1 in 100 mL of tetrahydrofuran, add 0.35 g of p-toluenesulfonic acid, mix well, add 6.28 g of 3-dimethylamino-1-propanol, raise the reaction temperature to 70 °C, and reflux for 4 h. After the reaction is complete, adjust the reaction system to neutral, add dichloromethane for extraction, collect the organic phase, dry it with anhydrous magnesium sulfate, concentrate and purify it to obtain intermediate 2.

[0072] S3. Dissolve intermediate 2 prepared in step S2 in 100 mL of ethyl acetate, add 13.10 g of 1,3-propanesulfonyl lactone and mix, raise the reaction temperature to 70 °C and reflux for 18 h. After the reaction is complete, filter, wash with ethyl acetate and diethyl ether, rotary evaporate, purify, and dry to obtain the modifier.

[0073] The preparation method of modified polylactic acid specifically includes the following steps:

[0074] S4. Accurately weigh 10g of L-lactic acid and place it in a flask. Add 0.08g of p-toluenesulfonic acid and 0.2g of stannous chloride. Stir the mixture at 200rpm and raise the temperature to 130℃. After reacting for 2.5h, raise the temperature to 170℃ and adjust the pressure in the reaction system to 100Pa. Continue reacting for 4h. After the reaction system cools to room temperature, add dichloromethane to dissolve the reaction product, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind it, and place it in a vacuum drying oven at 60℃ for 24h to obtain low molecular weight polylactic acid powder.

[0075] S5. Dissolve the oligomeric polylactic acid prepared in step S4 in 50 mL of dichloromethane, place it in an ice-water bath, add 1.67 g of triethylamine and mix well, then add 1.50 g of acryloyl chloride dropwise. After the addition is complete, raise the reaction temperature to 30 °C and stir the reaction for 18 h. After the reaction is complete, filter to remove impurities, wash with saturated sodium carbonate aqueous solution and saturated sodium chloride aqueous solution in sequence, collect the organic phase, dry with anhydrous sodium sulfate, rotary evaporate, and purify to obtain double bond modified polylactic acid.

[0076] S6. Dissolve the double bond modified polylactic acid prepared in step S5 in 100 mL of dichloromethane, add 4.4 g of the modifier prepared in step S3, mix well, add 20 mg of BPO, raise the reaction temperature to 90 °C to carry out the modification reaction, and after the reaction is completed, filter, dry and purify to obtain modified polylactic acid.

[0077] This embodiment also provides a method for preparing a safe butachlor-propyne oxadiazon microcapsule suspension, which is the same as in Example 1.

[0078] Example 3

[0079] This embodiment provides a safe butachlor-propyne oxadiazon microencapsulated suspension, which comprises the following components in parts by weight: 5 parts modified polylactic acid, 30 parts butachlor, 2 parts propyne oxadiazon, 18 parts octylphenol polyoxyethylene ether, 1.5 parts ethylene glycol, 4 parts xanthan gum, 1 part methylisothiazolinone, and 30 parts water.

[0080] The raw materials for preparing modified polylactic acid include the following components in parts by weight: 10 parts L-lactic acid, 1.55 parts acryloyl chloride, and 4.5 parts modifier;

[0081] The preparation method of the modifier specifically includes the following steps:

[0082] S1. Dissolve 5.00 g of maleic anhydride and 7.90 g of 3-dimethylamino-1-propanol in 150 mL of tetrahydrofuran. Raise the reaction temperature to 70 °C and reflux for 2 h. After the reaction is complete, add 10.0 g of CDMT and 5.8 g of NMM and place at 5 °C for activation treatment for 90 min. After the reaction is complete, add triethylamine to remove reaction byproducts. After purification, intermediate 1 is obtained.

[0083] S2. Dissolve intermediate 1 prepared in step S1 in 100 mL of tetrahydrofuran, add 0.50 g of p-toluenesulfonic acid, mix well, add 7.90 g of 3-dimethylamino-1-propanol, raise the reaction temperature to 75 °C, and reflux for 2 h. After the reaction is complete, adjust the reaction system to neutral, add dichloromethane for extraction, collect the organic phase, dry it with anhydrous magnesium sulfate, concentrate and purify it to obtain intermediate 2.

[0084] S3. Dissolve intermediate 2 prepared in step S2 in 100 mL of ethyl acetate, add 13.70 g of 1,3-propanesulfonyl lactone and mix, raise the reaction temperature to 80 °C and reflux for 15 h. After the reaction is complete, filter, wash with ethyl acetate and diethyl ether, rotary evaporate, purify, and dry to obtain the modifier.

[0085] The preparation method of modified polylactic acid specifically includes the following steps:

[0086] S4. Accurately weigh 10g of L-lactic acid and place it in a flask. Add 0.1g of p-toluenesulfonic acid and 0.15g of stannous chloride. Stir the mixture at 200rpm and raise the temperature to 135℃. After reacting for 1.5h, raise the temperature to 175℃ and adjust the pressure in the reaction system to 100Pa. Continue reacting for 5h. After the reaction system cools to room temperature, add dichloromethane to dissolve the reaction product, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind it, and place it in a vacuum drying oven at 60℃ for 24h to obtain low molecular weight polylactic acid powder.

[0087] S5. Dissolve the oligomeric polylactic acid prepared in step S4 in 50 mL of dichloromethane, place it in an ice-water bath, add 1.72 g of triethylamine and mix well, then add 1.54 g of acryloyl chloride dropwise. After the addition is complete, raise the reaction temperature to 30 °C and stir the reaction for 18 h. After the reaction is complete, filter to remove impurities, wash with saturated sodium carbonate aqueous solution and saturated sodium chloride aqueous solution in sequence, collect the organic phase, dry with anhydrous sodium sulfate, rotary evaporate, and purify to obtain double bond modified polylactic acid.

[0088] S6. Dissolve the double bond modified polylactic acid prepared in step S5 in 100 mL of dichloromethane, add 4.5 g of the modifier prepared in step S3, mix well, add 18 mg of BPO, raise the reaction temperature to 90 °C to carry out the modification reaction, and after the reaction is completed, filter, dry and purify to obtain modified polylactic acid.

[0089] This embodiment also provides a method for preparing a safe butachlor-propyne oxadiazon microcapsule suspension, which is the same as in Example 1.

[0090] Comparative Example 1

[0091] This comparative example provides a microencapsulated herbicide and its preparation method. The only difference between this example and Example 1 is that the modified polylactic acid is replaced with polylactic acid in the same weight parts of the microencapsulated suspension. The remaining components and their contents are the same as in Example 1.

[0092] Comparative Example 2

[0093] This comparative example provides a microencapsulated herbicide and its preparation method. The only difference between this example and Example 1 is that maleic anhydride is replaced with the same amount of modifier in the modified polylactic acid component, while the other components and their contents are the same as in Example 1.

[0094] Experimental Example 1

[0095] This experiment measures the drug loading and encapsulation efficiency of the microcapsule herbicides prepared in Examples 1-3 and Comparative Examples 1-2. These two parameters are important indicators for evaluating the performance of drug delivery systems and can reflect the drug loading capacity of microcapsules and the drug loss during the preparation process.

[0096] Accurately weigh 0.01 g of the dried microencapsulated herbicide powder prepared in Examples 1-3 and Comparative Examples 1-2 (accurate to 0.001 g) and dissolve it in an appropriate amount of methanol. To ensure complete dissolution of the microcapsules and release of the encapsulated drug, the solution was sonicated for 30 minutes. The sonicated solution was transferred to a 100 mL volumetric flask and diluted to the mark with methanol to obtain a homogeneous solution. Subsequently, the solution was centrifuged to remove undissolved solid particles or other impurities. After centrifugation, the supernatant was filtered through a 0.45 μm organic filter membrane to obtain a clear filtrate. The contents of butachlor and propyzamide were determined by HPLC and calculated. The drug loading (LC, %) and encapsulation efficiency (EE, %) were calculated according to the following formulas.

[0097] ;

[0098] ;

[0099] Figure 1 The figure shows the drug loading capacity results of the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-2 of this invention. As shown in the figure, the microencapsulated herbicides prepared in the examples of this invention have high encapsulation efficiency and drug loading. The high encapsulation efficiency indicates that the microencapsulated herbicides prepared in the examples of this invention can continuously release the drug, prolong the effectiveness of the active ingredient, and at the same time reduce the risk caused by premature drug release. The high drug loading indicates that the microencapsulated herbicides prepared in this invention can reduce the amount of carrier material applied, reduce costs, and avoid the phenomenon of sudden drug release in the early stage, thus reducing phytotoxicity.

[0100] Experimental Example 2

[0101] This experiment tested the wetting properties of the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-2 using a German Kruss DSA100 droplet shape analyzer. This instrument can accurately record the morphological changes of droplets on solid surfaces and calculate the contact angle value. First, fresh rice leaves were cut into strips and fixed on glass slides to ensure the flatness and stability of the test surface. Then, 5 μL of Pyr@DPA-PUMCs suspension was dropped onto the rice leaf surface using a microsyringe. All operations were performed at room temperature (25 ± 2 °C). For comparative analysis, deionized water and the commercial formulation Seltima were used as control samples. To ensure the reliability and repeatability of the experimental results, all operations were performed in triplicate, and the average value was taken as the final result.

[0102] Figure 2 The figures show the wetting performance results of the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. As shown, plant leaves are covered with a layer of hydrophobic epidermal wax, so pesticide sprays must be effectively wetted and diffused to achieve the best effect. The contact angle of the microencapsulated herbicides prepared in Examples 1-3 of this invention decreased from 102.3°-108.6° to 62.3°-68.2° after 5 minutes. This enhanced wetting promotes better pesticide adsorption and deposition while minimizing loss, thereby significantly improving its spreading performance. The increased wetting is conducive to the retention of pesticides on the leaf surface, ultimately improving pesticide utilization.

[0103] Experimental Example 3

[0104] This experiment conducted indoor pot experiments on the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-2. Following the guidelines for indoor bioactivity testing of pesticides, Part III: Soil Spraying Method for Activity Testing (NY / T1155.3-2006), the experiment used 50% humus, 25% loess, and 25% yellow sand. The materials were sterilized at high temperatures before the experiment. The temperature was set at 10-30℃ (reaching 0℃ briefly at night), and the humidity at 75-90%. The management of the test materials was consistent with greenhouse cultivation conditions. A pipette dripping system was used, and the herbicide was applied 24 hours after sowing, for a total of one application. After treatment, the plants were moved to a greenhouse for conventional cultivation, with watering via bottom irrigation. Weed emergence and growth were visually observed periodically after application. The number of weeds was surveyed at 20, 34, and 60 days post-application, and the fresh weight was also surveyed at the last application. The efficacy was calculated using the following formula:

[0105] ;

[0106] ;

[0107] Figure 3The figures show the pot experiment efficacy results of the microencapsulated herbicides prepared in Examples 1-3 and Comparative Examples 1-2 of this invention. As shown in the figures, Examples 1-3 of this invention have significant effects on the seedling emergence rate and fresh weight inhibition rate of grass plants, and can achieve the control effect.

[0108] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0109] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A safe butachlor · oxadiargyl microcapsule type suspension agent, characterized by: The microcapsule type suspension agent comprises the following components in parts by weight: 3-5 parts of modified polylactic acid, 25-30 parts of butachlor, 1-3 parts of oxadiargyl, 15-20 parts of dispersing agent, 1-2 parts of antifreezing agent, 3-5 parts of thickening agent, 0.5-1 part of preservative and 30-50 parts of water; the raw material for preparing the modified polylactic acid comprises the following components in parts by weight: 10 parts of L-lactic acid, 1.45-1.55 parts of acryloyl chloride and 4.3-4.5 parts of modifier.

2. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 1, characterized by: The dispersing agent comprises at least one of polyethylene glycol, sodium polyacrylate, octylphenol polyoxyethylene ether and sodium dodecyl benzene sulfonate; the antifreezing agent comprises at least one of glycerol, propylene glycol and ethylene glycol; the thickening agent comprises at least one of sodium carboxymethyl cellulose, xanthan gum and hydroxyethyl cellulose; and the preservative comprises at least one of sodium benzoate, methyl isothiazolinone and phenoxyethanol.

3. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 2, characterized by: The preparation method of the modifier specifically comprises the following steps: S1, maleic anhydride and 3-dimethylamino-1-propanol are dissolved in tetrahydrofuran, the reaction temperature is increased for reflux reaction, after the reaction is completed, an activating agent is added for activation treatment, after the reaction is completed, triethylamine is added to remove reaction byproducts, and after purification, an intermediate 1 is obtained; S2, the intermediate 1 prepared in step S1 is dissolved in tetrahydrofuran, p-toluenesulfonic acid is added, after being uniformly mixed, 3-dimethylamino-1-propanol is added, the reaction temperature is increased for reflux reaction, after the reaction is completed, the reaction system is adjusted to be neutral, dichloromethane is added for extraction, the organic phase is collected, dried with anhydrous magnesium sulfate, concentrated, purified, and an intermediate 2 is obtained; S3, the intermediate 2 prepared in step S2 is dissolved in ethyl acetate, 1,3-propane sulfolane is added for mixing, the reaction temperature is increased for reflux reaction, after the reaction is completed, filtration is performed, washing is performed with ethyl acetate and diethyl ether, rotary evaporation is performed, purification is performed, and after drying, a modifier is obtained.

4. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 3, characterized by: In step S1, the mass ratio between the maleic anhydride and the 3-dimethylamino-1-propanol is 1:1.05-1.6; the activating agent comprises at least one of DCC, CDMT and NMM; and the mass ratio between the maleic anhydride, the CDMT and the NMM is 1:1.8-2:1.04-1.

16.

5. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 4, characterized by: In step S1, the reaction temperature of the reflux reaction is 70-90°C, and the reaction time of the reflux reaction is 1-2h.

6. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 5, characterized by: In step S2, the addition amount of the p-toluenesulfonic acid is 5%-10% of the mass of the maleic anhydride; The reaction temperature of the reflux reaction is 65-75°C, and the reaction time of the reflux reaction is 2-4h.

7. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 6, characterized by: In step S3, the mass ratio between the maleic anhydride and the 1,3-propane sulfolane is 1:2.5-2.75; the reaction temperature of the reflux reaction is 70-90°C, and the reaction time of the reflux reaction is 12-18h.

8. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 7, characterized by: The preparation method of the modified polylactic acid specifically comprises the following steps: S4, the L-lactic acid is placed in a flask, after adding a carboxyl activating agent and a catalyst, the temperature is raised to 130-140℃, after 1.5-2.5h of reaction, the temperature is continuously raised to 170-180℃, the pressure in the reaction system is adjusted to 100-200Pa, after 4-6h of continuous reaction, the reaction product is dissolved in dichloromethane, filtration is performed, the filtrate is collected, anhydrous methanol is added for precipitation, filtration is performed, the precipitate is collected, grinding and drying are performed, and low molecular weight polylactic acid is obtained; S5, the low molecular weight polylactic acid prepared in step S4 is dissolved in dichloromethane, placed in an ice water bath, after adding triethylamine and mixing uniformly, acryloyl chloride is added dropwise, after the dropwise addition is completed, the reaction temperature is raised for stirring reaction, after the reaction is completed, impurities are removed by filtration, washed with saturated sodium carbonate aqueous solution and saturated sodium chloride aqueous solution in sequence, the organic phase is collected, dried with anhydrous sodium sulfate, rotary evaporation is performed, purification is performed, and double bond modified polylactic acid is obtained; S6, the double bond modified polylactic acid prepared in step S5 is dissolved in dichloromethane, the modifier prepared in step S3 is added, after mixing uniformly, an initiator is added, the reaction temperature is raised for modification reaction, after the reaction is completed, filtration, drying and purification are performed, and modified polylactic acid is obtained.

9. The security butachlor · oxadiargyl microcapsule type suspension agent according to claim 8, characterized by: In step S4, the addition mass of the carboxyl activating agent is 0.08-0.1% of the mass of the L-lactic acid, and the carboxyl activating agent includes at least one of methylsulfonic acid, toluenesulfonic acid, sulfosuccinic acid, p-toluenesulfonyl chloride and p-toluenesulfonic acid; in step S4, the addition mass of the catalyst is 0.1-0.2% of the mass of the L-lactic acid, and the catalyst includes at least one of stannous chloride, stannous oxide and dibutyltin dilaurate; In step S5, the addition mass of the triethylamine is 16.2%-17.2% of the mass of the L-lactic acid; in step S5, the reaction temperature of the stirring reaction is 30-40℃, and the time of the stirring reaction is 12-18h; In step S6, the addition mass of the initiator is 0.4%-0.5% of the mass of the modifier; in step S6, the reaction temperature of the modification reaction is 80-100℃, and the reaction time of the modification reaction is 4-6h.

10. A method for preparing the security butachlor · oxadiargyl microcapsule type suspension agent according to claim 9, characterized by: Specifically includes the following steps: ①The modified polylactic acid is dissolved in ethyl acetate, butachlor and oxadiargyl are added, and after mixing uniformly, an oil phase is obtained; ②The oil phase prepared in step ① is added to deionized water, high-speed shearing mixing is performed, and after vacuum distillation, washing and drying, pesticide nanoparticles are obtained; ③The pesticide nanoparticles prepared in step ②, a dispersing agent, an antifreezing agent, a thickening agent and a preservative are mixed uniformly in deionized water, and a microcapsule type suspension agent is obtained.

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