A preparation process of high-efficiency herbicide

Abstract

The present invention relates to the technical field of herbicide preparation, and in particular to a process for preparing a highly effective herbicide. The invention aims to solve the technical problems of conflicting physicochemical properties of compound herbicide components, difficulty in controlling the release sequence, overlapping environmental risks, and low field retention rates of common herbicides in severe weather. The herbicide adopts a microcapsule carrier with a core-shell multilayer structure to encapsulate active ingredients with various mechanisms of action in layers, sequentially constructs each layer of microcapsules through microfluidic step-by-step encapsulation technology, and adopts fluidized bed spray coating to form a canopy modification layer, and finally obtains a stable powder product by vacuum freeze drying. The present invention realizes spatiotemporal separation and programmed release of a variety of herbicidal active substances through intelligent carriers, greatly improving the weed control effect and reducing environmental risks, and can be widely used for the efficient prevention and control of weeds in crop fields.

Description

Technical Field

[0001] The present invention relates to the technical field of herbicide preparation, and in particular to a process for preparing a high-efficiency herbicide. Background Art

[0002] Chemical herbicides play an important role in agricultural production, but existing herbicide products have many shortcomings in terms of compound application and field persistence. On the one hand, herbicidal active ingredients with different mechanisms of action are often compounded to expand the control spectrum or improve efficacy. However, due to the differences in the physical and chemical properties of the ingredients, direct mixing may cause compatibility issues, such as solubility and stability conflicts, resulting in reduced formulation performance. In addition, the simultaneous release of multiple agents can easily lead to overlapping crop damage and accumulated environmental risks. On the other hand, traditional herbicides are subject to climatic conditions. When they are washed away by rainfall or exposed to strong sunlight after application, the active ingredients are often rapidly lost or decomposed, resulting in short-term field efficacy and severe weed rebound. Especially when broadleaf weeds and grass weeds coexist in the weed community, releasing all the agents at a single time makes it difficult to achieve both rapid and persistent effects.

[0003] Traditional compound herbicide formulations also suffer from insufficient field stability. For example, many contact herbicides are only effective when sprayed on the surface of weed leaves; once the liquid drips into the soil, it loses its effect because it is not absorbed by the roots. While systemic herbicides can be absorbed and transported by weeds, their effectiveness may diminish before the weeds are completely dead due to their limited shelf life. Furthermore, herbicides such as glufosinate are toxic to green plants and must be applied to stems and leaves to avoid contact with crops. However, once applied to the soil, they are easily fixed in the soil and degraded by microorganisms, making them difficult to achieve a long-term, closed-loop weed control effect. The prior art hopes to achieve better results by improving the compound formulation, but it is not ideal. For example, the prior art CN107396934A discloses a dispersible oil suspension containing glufosinate, fluazifop-butyl and high-efficiency fluazifop-butyl and a preparation method thereof. The method comprises the following steps: first, an emulsifier, a dispersant, glufosinate, fluazifop-butyl and high-efficiency fluazifop-butyl are ground to a particle size of less than 0.01 cm, and then added to a reactor, heated, mixed and dispersed uniformly; a thickener is added under high-speed shearing conditions, ground to a particle size of less than 5 μm, and then a stabilizer, vegetable oil and deionized water are added to the reactor together, mixed and dispersed uniformly to obtain a dispersible oil suspension containing glufosinate, fluazifop-butyl and high-efficiency fluazifop-butyl. Although the treatment is performed, the timing and targeting problems of the release of the active ingredients of the compound combination cannot be changed.

[0004] In view of the above problems, there is an urgent need for an innovative herbicide formulation and production process that can organically combine herbicidal active ingredients with multiple mechanisms of action, overcome the incompatibility between ingredients through reasonable spatial separation and carrier design, and use environmental triggering and intelligent controlled release methods to achieve phased release of drug efficacy, thereby taking into account both fast-acting weed control and sustained weed suppression, while improving field anti-scouring performance and reducing environmental load. Summary of the Invention

[0005] The primary objective of this invention is to provide a process for preparing a highly effective herbicide and its unique time-controlled core-shell carrier composition, overcoming the problems of existing compound herbicides, such as conflicting physicochemical properties, difficulty in regulating release timing, overlapping environmental risks, and poor field persistence. This invention aims to physically isolate and sequentially release different types of herbicidal active ingredients through a multi-layer microcapsule structure, enabling each ingredient to exert its effects under optimal spatial and temporal conditions, significantly improving herbicide efficiency and enhancing safety for crops and the environment.

[0006] The specific technical solutions are as follows:

[0007] A process for preparing a high-efficiency herbicide, wherein the main active ingredients of the high-efficiency herbicide are separated and coated by microcapsules packaged in a core layer, a middle layer, a shell layer and a canopy layer; the microcapsules are prepared by microfluidic step-by-step encapsulation and fluidized bed spraying technology.

[0008] The specific steps include:

[0009] S1: A multiphase microfluidic device is used for encapsulation in sequence. First, the oil phase containing fluazifop-butyl and a photosensitizer is used as the core. Under acidic conditions, it is mixed with an aqueous phase diluted with HPMCP solution to form an oil-in-water primary emulsion to solidify to obtain core layer microparticles A. Secondly, a solution containing a highly effective fluazifop-butyl and a plant hormone analog is blended with PLGA to form secondary emulsions, which are coated on the surface of the core layer microparticles A and solidified to obtain middle layer microcapsules B. Then, a chitosan-catechol polymer solution containing glufosinate, humic acid-iron complex and FeCl3 is added to the microcapsules B and fed into the microfluidic device to further emulsify the gel, cross-link and solidify to form a shell layer, and obtain a core-shell multilayer microcapsule suspension C.

[0010] S2: spray granulating the core-shell multilayer microcapsule suspension C to obtain wet microparticles D, and then spraying the wet microparticles D with a leaf-friendly polymer material solution in a fluidized bed to form a canopy modification layer coating;

[0011] S3: The wet microgranules D coated with S2 are pre-frozen and then freeze-dried under low-temperature vacuum conditions to obtain dry microcapsule herbicide.

[0012] Furthermore, the mass ratio of fluazifop-butyl, high-efficiency fluazifop-butyl and glufosinate described in S1 during preparation is 1:1:1; the mass ratio of the photosensitizer described in S1 to the fluazifop-butyl during preparation is 1:10; the mass ratio of the HPMCP described in S1 to the fluazifop-butyl during preparation is 1:0.625; the mass ratio of the plant hormone analogue described in S1 to the high-efficiency fluazifop-butyl during preparation is 1:50; the mass ratio of the PLGA described in S1 to the high-efficiency fluazifop-butyl during preparation is 2:1; the mass ratio of the humic acid-iron complex described in S1 to the glufosinate during preparation is 1:2.5; the mass ratio of the FeCl3 described in S1 to the glufosinate calculated in the form of FeCl3·6H2O during preparation is 1:5; the mass ratio of the chitosan-catechol polymer described in S1 to the glufosinate during preparation is 1:1.

[0013] Furthermore, the photosensitizer described in S1 is any one or more of a benzophenone photoinitiator, a chlorophyll derivative pheophorbide a or a bacterial chlorophyll derivative; the plant hormone analogue described in S1 is any one or more of naphthylacetic acid, 6-benzyladenine or an abscisic acid analogue.

[0014] Furthermore, the acidic conditions described in S1 are achieved by adding acetate buffer; the formation of water-in-oil primary emulsion droplets described in S1 specifically includes using a dual-channel microfluidic T-shaped connector, the inner phase is the oil phase, and the outer phase is the water phase, which are pushed in at different flow rates at 25°C to form water-in-oil primary emulsion droplets under shear action.

[0015] Furthermore, the pushing at different flow rates specifically includes the pushing flow rate of the inner phase being 0.5 mL / min, and the pushing flow rate of the outer phase being 1.5 to 2.5 mL / min.

[0016] Furthermore, the co-emulsification to form secondary emulsion droplets described in S1 includes first forming a W / O type primary emulsion and then preparing W / O / W double emulsion droplets through a coaxial capillary microfluidic device.

[0017] Furthermore, the gel is further emulsified in the microfluidic device as described in S1, specifically, the microcapsule B is used as the dispersed phase, and the chitosan-catechol polymer solution containing glufosinate, humic acid-iron complex and FeCl3 is used as the continuous phase, and a double emulsion is formed through the microfluidic device at a flow ratio of 1:4 to 1:6.

[0018] Furthermore, the specific process of the spray granulation described in S2 includes rapid spray drying to form fine particles with a moisture content of 20% under the condition that the inlet temperature of the spray equipment is set at 40°C; the specific parameters of the spraying in a fluidized bed described in S2 include a spray rate of 4 to 6 mL / min and a spraying time of 25 to 35 minutes; the foliage-friendly polymer material solution described in S2 is a mixture of polyvinyl alcohol, silicone spreader and water.

[0019] Furthermore, the pre-freezing in S3 is pre-freezing at a low temperature of -40°C for 2 hours; the freeze-drying under low-temperature vacuum conditions in S3 is sublimation drying at -30°C and a vacuum degree of 0.1 mbar for 24 hours.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention rationally combines and releases fast-acting contact killers, systemic herbicides, and lethal herbicides in layers, providing a three-dimensional weed control effect from the stems and leaves to the roots, from immediate killing to sustained suppression. The rapid contact killing of fluazifop-butyl can control the growth of broadleaf weeds on the day of application, while the slow-release systemic release of fluazifop-butyl ensures that the growth points of grass weeds are completely eradicated in the following days. The terminal release of glufosinate-ammonium is used to clean up remaining plants and newly sprouted seedlings, avoiding missed killing and secondary weed breeding. The different mechanisms of action cooperate with each other to improve the overall weed control efficiency, reduce the dosage of a single agent, and delay the development of weed resistance.

[0022] (2) The present invention realizes the sequential and phased release of active ingredients through multiple response mechanisms such as light, pH, enzymes, and metal ions. Compared with the traditional method of releasing all agents at once, the timed release ensures that each herbicide takes effect at the best time and location: the light-responsive core layer ensures that fluazifop-butyl takes effect immediately when exposed to sunlight; the enzyme-degradable middle layer allows the highly effective fluazifop-butyl to take effect after the initial contact killing, and the slow release in the plant body facilitates conduction; Fe 3+ The chelating response shell avoids the crop leaves and releases glufosinate when the agent settles in the soil; this programmed release reduces the interference between different agents, reduces the risk of instantaneous pesticide damage to crops, and achieves a longer lasting effect through continuous drug supply.

[0023] (3) The canopy modification layer of the present invention gives the microcapsules good adhesion, significantly improving the anti-scouring ability of the pesticide in the field; even if it rains after application, the microcapsules can partially adhere to the surface of weeds or remain on the leaf surface to form redeposition, and will not be completely washed away like emulsifiable concentrates or aqueous solutions.

[0024] (4) The microfluidic-fluidized bed-freeze drying process adopted in the present invention realizes the large-scale preparation of multilayer microcapsules; microfluidic technology ensures that the particle size and layer thickness of each microcapsule are uniform and adjustable, thereby ensuring stable product quality; fluidized bed coating technology is mature and can be operated continuously in industry; although freeze drying is relatively expensive, it ensures the activity of heat-sensitive ingredients. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart for preparing a highly effective herbicide according to the present invention;

[0026] Figure 2 Schematic diagram of the release timing and contact sequence mechanism of the timing-controlled core-shell microcapsules of the present invention;

[0027] Figure 3 This is a comparison chart of the cumulative release results of different agents at different time points in the same environment in Experimental Example 1 of the present invention and the comparative example;

[0028] Figure 4 This is a diagram showing the effect of the high-efficiency herbicide prepared by the present invention dispersing into water when used. DETAILED DESCRIPTION

[0029] The following examples further illustrate and describe the technical solutions of the present invention. It is particularly noted that each specific embodiment is intended to be a concretization and explanation of the technical solutions and should not be construed as limiting the scope of protection of the present invention. Persons of ordinary skill in the art are entitled to modify the technical solutions of these embodiments and to substitute equivalent features for some or all of the technical features. Such modifications or substitutions do not alter the essence of the corresponding technical solutions and do not deviate from the scope of the technical solutions described in the present invention.

[0030] The present invention provides a process for preparing a highly effective herbicide. Figure 1 The figure below is a flow chart of the process for preparing a highly effective herbicide according to the present invention. Its innovation lies in the use of a multi-layer structure consisting of a core layer, a middle layer, a shell layer, and a canopy modification layer, along with a corresponding step-by-step production process, to achieve the sequential release and targeted targeting of different herbicide components. The specific technical solution is as follows:

[0031] 1. Design of each layer of timing-controlled core-shell microcapsules

[0032] Core layer design: The innermost layer of the microcapsule is the core layer, and its active ingredient is the fast-acting contact herbicide fluazifop-butyl, with an appropriate amount of photosensitizer added. Fluazifop-butyl is a diphenyl ether protoporphyrinogen oxidase inhibitor that requires light to exert its efficacy. The photosensitizer introduced into the core layer of the present invention uses sunlight to trigger the rapid degradation of the core layer material. When the spray is deposited on weed leaves, the UV / visible light in the sunlight is absorbed by the photosensitizer and produces active free radicals or photogenerated acids, which promote molecular chain scission or swelling and disintegration of the polymer material coating the core layer. This rapidly releases fluazifop-butyl within 24 hours of application, achieving rapid burning and contact killing of the weed surface tissue. The core layer is coated with pH-sensitive hydroxypropyl methylcellulose phthalate (HPMCP), which is easily soluble in a neutral to alkaline environment. Its function is to provide a stable coating during the preparation and storage stages of the formulation. When sprayed onto plant leaves and the microenvironment pH value changes locally under the action of a photosensitizer, it accelerates dissolution and release. At the same time, HPMCP helps prevent fluazifop-butyl from leaking prematurely in the spray liquid, thereby improving the stability of the formulation.

[0033] Middle-layer design: The middle layer of the microcapsule is encapsulated outside the core layer. Its active ingredients are highly effective haloxyfop-p-ethyl and a plant hormone analog. Highly effective haloxyfop-p-ethyl is a selective systemic herbicide used primarily to control grass weeds. Its mechanism of action is to inhibit fatty acid synthesis, halting cell division at the weed's growing point, ultimately leading to the death of the entire plant. Because it requires long-distance transmission within the weed, the present invention places it in the middle sustained-release layer. The middle layer coating material is enzyme-responsive polylactic-co-glycolic acid (PLGA), a biodegradable polymer that gradually hydrolyzes in the environment. Enzymes such as esterases present in plants and soil can accelerate its degradation. By controlling the molecular weight and copolymerization ratio of PLGA, the present invention allows the middle layer to gradually degrade 1 to 3 days after release from the core layer, slowly releasing highly effective haloxyfop-p-ethyl. The plant hormone analogue added to the middle layer is used to guide the directional distribution of the herbicide in the target weeds. The plant hormone analogue can be an artificially synthesized auxin analogue or other signal molecules that promote conduction. Its mechanism of action is to induce the weeds' growth regulation response when the weeds absorb the highly effective haloxyfop-ethyl released by the microcapsules, so that the herbicide is more effectively transported to the growth points and vascular bundles of the grass weeds; this enables the middle layer to achieve the functions of directional enrichment and slow release, ensuring that the highly effective haloxyfop-ethyl fully enters the weeds and avoiding potential pesticide damage to crops caused by excessive release at one time.

[0034] Shell design: The shell of the microcapsule is the outermost functional shell, and its main active ingredients are glufosinate ammonium and humic acid-iron (III) complex, and the carrier material is Fe 3+Responsive chitosan-catechol polymer. Glufosinate is a fast-acting herbicide, but it lacks selectivity and is usually used to treat stems and leaves, so it must avoid contact with crops. The present invention places glufosinate in the outermost layer and is designed to trigger the release of soil. The purpose is to release glufosinate only when the microcapsules fall to the soil surface or are washed into the soil by rainwater, so as to remove weeds remaining on the soil surface or re-germinating, thereby avoiding direct phytotoxicity to crop stems and leaves. Chitosan-catechol polymer is a modified natural polymer. After the catechol group is introduced into its molecular chain, it is responsive to Fe 3+ Ions have strong coordination ability and can form a metal-phenol coordination cross-linking network; the present invention utilizes this characteristic to introduce a small amount of Fe 3+ The ions make the chitosan-catechol polymer form a strong cross-linked shell, which keeps the microcapsules intact during the storage and spraying of the preparation; when the microcapsules reach the soil surface, the humus widely present in the soil will react with Fe 3+ Competitive chelation occurs, especially in the present invention, a certain proportion of humic acid-Fe is pre-introduced into the shell 3+ complexes, so that when encountering a large amount of environmental humic acid, these complexes dissociate and transfer Fe 3+ Take away; with Fe 3+ Removed by chelation, originally by Fe 3+ The bridged chitosan-catechol polymer network immediately disintegrates and swells, causing the shell to rupture rapidly and release glufosinate ammonium. Once released into the soil solution, glufosinate ammonium can have a toxic effect on surrounding weed seedlings or roots that have not yet been eliminated. At the same time, because glufosinate ammonium is easily degraded in the soil, its residual period is short and it will not accumulate for a long time to harm subsequent crops.

[0035] Canopy modification layer design: In order to further improve the effectiveness of the microcapsule preparation when used in the field, the present invention adds a canopy modification layer to the outermost layer of the microcapsule. This layer does not contain additional herbicidal active ingredients, but is composed of special excipients. Its main functions include enhancing leaf affinity, so that the microcapsules can be firmly attached and evenly spread on the weed leaves after being sprayed, and are not easily washed away by rainwater. The material of the canopy modification layer is a polymer with a good hydrophilic-hydrophobic balance; the present invention preferably uses a plant-safe polymer adhesive natural resin, polyvinyl alcohol or alginate to form this layer. Through the action of the canopy modification layer, the microcapsules of the present invention show better anti-scouring properties on the leaf surface, ensuring that the active ingredients remain on the target weeds for a long enough time to exert their effects.

[0036] The spatial design of each layer of the microcapsule includes the following design logic: Figure 2As shown, the release sequence and contact sequence of the time-controlled core-shell microcapsules of the present invention are matched. First, when the herbicide is sprayed, most of it falls on the leaf surface. At this time, the core layer HPMCP forms a 50-100 nm channel after illumination, allowing the fluazifop-butyl loaded in the core layer to be released and quickly act on the leaf tissue through diffusion. Then, the microcapsules enter the plant vascular bundle through leaf absorption or rainwater washing. After contacting the esterase specific to grass weeds, the middle layer PLGA is enzymatically hydrolyzed to form a hydrophilic channel with a pore size of 2-5 nm, allowing the slow release of high-efficiency fluazifop-butyl with a smaller molecular weight, but blocking the premature release of glufosinate. Finally, the remaining outer layer microcapsules fall into the soil and are enriched in the root system after metabolism. 3+ It chelates with the catechol groups of the chitosan-catechol polymer, initiating the dissociation of the polymer cross-linked network. In addition, small molecular acids such as oxalic acid secreted by the roots will accelerate the disintegration of the shell and release glufosinate ammonium.

[0037] It should be noted that if the order of the core layer and the outer layer is swapped, it seems that the acetaminophen that contacts the leaf surface can be released faster, but due to the binding characteristics of acetaminophen and the carrier, it is released too quickly when the outer layer is illuminated and decomposed, resulting in poor effect, or in bad weather, the acetaminophen released too quickly and in large quantities is easily washed away by rainwater, resulting in poor effect; and the microcapsules that fall into the soil are glufosinate-ammonium loaded by the core layer, and cannot contact the soil for release, resulting in being detained all the time, not only weakening the effect, but also causing delayed toxicity; if the middle layer of high-efficiency flupyrazole is placed in the outer layer, the effect will also be poor, and it needs to be in the vascular system to play a role. Exposing it too early on the leaf surface will cause a large amount of loss, and the effect of falling into the soil will also be unable to be achieved. Only by the reasonable space allocation and material combination provided by the present invention can the herbicide microcapsules be maximized in time sequence.

[0038] 2. Continuous production process

[0039] To achieve the above-mentioned multilayer structure, the present invention has developed a continuous microfluidics-spraying-drying process that can efficiently mass-produce the time-controlled core-shell microcapsule herbicide. The main steps include:

[0040] Microfluidic step-by-step encapsulation: Multilayer microcapsules were prepared using microfluidic technology. A microfluidic device with a coaxial fluid structure was used. First, primary emulsion droplets containing a core layer were prepared. Fluazifop-butyl and photosensitizer were dissolved in the oil phase and formed into W / O droplets with the aqueous HPMCP solution in the microchannel. After solidification, core layer particles of tens of microns in size were obtained. These core layer particles were introduced into the next microfluidic device, where they came into contact with the aqueous phase or emulsion containing high-efficiency fluazifop-butyl and plant hormone analogs to form W / O / W double emulsion droplets. PLGA was solidified and deposited on the surface of the core particles in the continuous phase to form a middle layer. Then, the microcapsules with the middle layer were again mixed with chitosan-catechol polymer solution and Fe in the microfluidic device.3+ The crosslinkers meet and coat the hydrogel shell, which is then cured and crosslinked to form a stable core-shell multilayer microcapsule suspension. Microfluidics allows for the stepwise injection of different liquid phases to achieve compartmentalized encapsulation of each active ingredient, while the droplet size can be precisely controlled to ensure uniform and controllable microcapsule layer thickness.

[0041] Fluidized bed spray coating: The microcapsule suspension is spray-dried into aqueous microparticles or directly prepared as wet granules using a high-solids emulsion. These granules are then spray-coated in a fluidized bed. The coating liquid is a canopy-modifying layer solution formulated with a polymer adhesive and surfactant containing a specific solids content. By controlling the fluidized bed inlet air temperature at a low level (preferably <50°C), the coating liquid is evenly sprayed onto the microparticle surface, rapidly forming a film and a durable canopy-modifying layer.

[0042] Vacuum freeze drying: The coated wet microcapsules are frozen at low temperatures and then sublimated in a vacuum freeze dryer to remove any residual moisture. Compared to traditional hot air drying or spray drying, this step avoids the degradation and inactivation of heat-sensitive ingredients like glufosinate ammonium at high temperatures, while maintaining the stability of the microcapsule particle size and structure. The dried product becomes a microcapsule powder with excellent flowability, which can be used for rapid on-site preparation of herbicidal solutions.

[0043] Example 1

[0044] A preparation process of a high-efficiency herbicide is as follows:

[0045] S1: Weigh the following components according to the following proportions: fluazifop-butyl technical 5 g (purity: 97%), photosensitizer benzophenone photoinitiator (Irgacure 184, BASF) 0.5 g; high-efficiency fluazifop-butyl technical 5 g (purity: 99%), auxin analogue naphthaleneacetic acid (NAP-70%Na, Sichuan Guoguang Agrochemical Co., Ltd.) 0.1 g; glufosinate ammonium aqueous solution (50% mass concentration ratio) 10 g, humic acid iron complex (containing 5 wt% iron as Fe, Shandong Agricultural University Fertilizer Technology Co., Ltd.) 2 g; HPMCP polymer (HP-55, Ashland) 8 g, PLGA copolymer (lactic acid: glycolic acid mass ratio = 75:25, molecular weight 50 kDa, RESOMER® RG 753) S, Evonik) 10g, chitosan-catechol polymer (ChitoLux™ series, AMS) 5g, FeCl3·6H2O (Sinopharm Chemical Reagent Co., Ltd.) 1g; the canopy coating liquid composition is polyvinyl alcohol (PVA, PVA-1788, Sichuan Chuanwei Chemical Co., Ltd.) 2g, silicone spreader (Silwet® L-77, Maitu High-Tech Materials Group) 0.2g, and water 50g.

[0046] S2:

[0047] Core layer emulsification: Fluorosulfuron and photosensitizer were dissolved in 11 mL of cyclohexanone organic solvent to form oil phase A. HPMCP was dissolved in 5 mL of ethanol and diluted to aqueous phase B by adding 95 mL of acetate buffer (pH 4.5). A dual-channel microfluidic T-shaped connector was used, with oil phase A as the inner phase and aqueous phase B as the outer phase. The two phases were introduced at 25°C via a precision syringe pump at flow rates of 0.5 mL / min and 2 mL / min, respectively. W / O-type emulsion droplets were formed under shearing action. After flowing out of the microchannel, they were immediately solidified in an alkaline coagulation bath (Na2CO3 buffer, pH 8) to obtain HPMCP-coated fluorosulfuron core layer microparticles. The microparticles were collected and washed by centrifugation to remove residual solvent, resulting in a core layer suspension with an average particle size of 30 µm.

[0048] Middle layer emulsification: The core layer suspension was used as the inner dispersed phase C, and 10 mL of a high-efficiency haloxyfop-ethyl and naphthaleneacetic acid ethanol-water mixed solution was prepared as the intermediate oil phase, and 5 wt% Span-80 emulsifier was dissolved to improve the interfacial tension. PLGA dissolved in 50 mL of dichloromethane was added to form an oil phase D, which was pre-emulsified with the inner dispersed phase C to obtain a W / O type primary emulsion. The primary emulsion was then passed through a coaxial capillary microfluidic device and merged with the external aqueous phase E (0.5% polyvinyl alcohol aqueous solution) to prepare W / O / W double emulsion droplets. The flow rate ratio of the inner and outer phases was adjusted to ensure that each double emulsion contained one core layer particle. The double emulsion evaporated dichloromethane at room temperature and was hydrated and cross-linked to deposit PLGA to form a middle layer solid wall. After centrifugation and concentration, a PLGA microcapsule suspension containing the core layer was obtained.

[0049] Shell emulsification: chitosan-catechol polymer was dissolved in 100 mL of acetate buffer (pH 5.5) to obtain an aqueous phase, and humic acid iron complex, FeCl3 solution and glufosinate aqueous solution were added and mixed evenly as the continuous phase F; the above microcapsule suspension with the middle layer was used as the dispersed phase G and injected into the central channel of the microfluidic device through a syringe pump, and the continuous phase F was injected from the outer channel. The dispersed phase G and the continuous phase F were injected at a flow ratio of 1:5 to produce a double emulsion; the catechol group was in the microemulsion environment and FeCl3 solution was mixed evenly. 3+ Cross-linking occurs rapidly in the presence of chitosan, causing chitosan to gel into a shell on the surface of the microcapsule. After the reaction is maintained for 1 hour, the obtained microcapsules are washed with pure water to obtain a stable core-shell multilayer microcapsule suspension.

[0050] S3: Add the above microcapsule suspension to the spray dryer, set the inlet temperature to 40℃, and quickly spray dry it into fine particles with a moisture content of 20%; then transfer the particles to the fluidized bed equipment, use a downward spray fluidized bed spray gun, fluidize the particles with 45℃ hot air, and spray the prepared canopy coating liquid (PVA, silicone aqueous suspension) at the same time; the spray rate is 5mL / min, and spray for 30 minutes to evenly form a thin film coating on each particle. After stopping spraying, continue to blow air drying for 5 minutes to initially solidify the coating layer.

[0051] S4: The wet microcapsule granules discharged from the fluidized bed are quickly pre-frozen at -40°C for 2 hours, and then transferred to a freeze dryer; sublimation drying is performed at -30°C and a vacuum degree of 0.1 mbar for 24 hours to completely remove moisture and obtain dry microcapsule herbicide powder.

[0052] In actual use, the microcapsule herbicide powder prepared above is dispersed into water (such as Figure 4 As shown), you can start weed spraying.

[0053] Example 2

[0054] The preparation method of reference example 1 is different in that:

[0055] S1: photosensitizer chlorophyll derivative pheophorbide a 0.5g; plant auxin analog 6-benzyladenine 0.1g;

[0056] S2:

[0057] Core layer emulsification: The inner phase is oil phase A, and the outer phase is water phase B, which are injected at a flow rate of 0.5 mL / min and 1.5 mL / min respectively at 25°C through a precision syringe pump;

[0058] Shell emulsification: The continuous phase F is injected from the outer channel, and the dispersed phase G and the continuous phase F produce a double emulsion at a flow ratio of 1:4;

[0059] S3: spray at a rate of 4 mL / min for 25 minutes to form a uniform film coating on each particle;

[0060] The other steps are the same.

[0061] Example 3

[0062] The preparation method of reference example 1 is different in that:

[0063] S1: photosensitizer bacteriochlorophyll derivative 0.5g; plant auxin analogue abscisic acid analogue 0.1g;

[0064] S2:

[0065] Core layer emulsification: The inner phase is oil phase A, and the outer phase is water phase B, which are injected at a flow rate of 0.5 mL / min and 2.5 mL / min respectively at 25°C through a precision syringe pump;

[0066] Shell emulsification: The continuous phase F is injected from the outer channel, and the dispersed phase G and the continuous phase F produce a double emulsion at a flow ratio of 1:6;

[0067] S3: spray at a rate of 6 mL / min for 35 minutes to form a uniform film coating on each particle;

[0068] The other steps are the same.

[0069] Comparative Example 1

[0070] The preparation method of reference example 1 is different in that:

[0071] The preparation involves simply mixing and encapsulating the three active ingredients in a single-layer microcapsule, without employing a sequential control mechanism. The specific method involves uniformly mixing fluazifop-butyl, haloxyfop-ethyl, and glufosinate-ammonium in a 1:1:1 mass ratio. Ethyl cellulose, a polymer encapsulating material, is then added and dissolved in an organic solvent. Microencapsulated particles are then prepared by spray drying. The resulting microcapsules are single-layer structures, containing the three active ingredients coexisting without a specific triggering mechanism.

[0072] Comparative Example 2

[0073] The preparation method of reference example 1 is different in that:

[0074] Microcapsules were prepared using the same core layer, middle layer, and shell layer formulations and microfluidic process as in Example 1, but the final fluidized bed canopy coating step was omitted, and dry powder was obtained by direct drying.

[0075] Comparative Example 3

[0076] The preparation method of reference example 1 is different in that:

[0077] In S4, a conventional spray dryer is used to quickly dry the mixture into powder at an inlet air temperature of 120°C.

[0078] Experimental Example 1

[0079] The microcapsule herbicide powders prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to a content layer release test. The specific test conditions are as follows:

[0080] One gram of microencapsulated herbicide powder was added to an aqueous medium irradiated with simulated sunlight (environment A), a pH 7.0 buffer solution containing esterase (environment B), and a soil extract containing humic acid (environment C). The release of each herbicide was monitored, and the concentration of the active ingredient in the solution was determined by high-performance liquid chromatography to calculate the cumulative release rate. The cumulative release rate at three key time points, 2, 24, and 72 hours, was measured, calculated, and compared.

[0081] The test results are shown in Table 1, Table 2, Table 3 and Appendix Figure 3 shown.

[0082] Table 1 Comparison of the cumulative release rates of fluazifop-butyl in different environments and at different time points in Experimental Example 1

[0083]

[0084] Table 2 Comparison of the cumulative release rates of high-efficiency halpyrazoprop-methyl in different environments and at different time points in Experimental Example 1

[0085]

[0086] Table 3 Comparison of cumulative release rates of glufosinate in different environments and at different time points in Experimental Example 1

[0087]

[0088] Note: In Tables 1 to 3, “>99.9” means very close to 100% and can be approximated to 100% during data processing.

[0089] Combined with attachment Figure 3 , It can be seen from the above comparison results that Comparative Example 1 is an ordinary microcapsule without a layered controlled release design and a single-layer structure. Three drugs coexist in it without a specific trigger mechanism. Due to the lack of layered isolation, the fast-acting and slow-release components are mixed together, and the release is controlled by the single property of the material, and the step-by-step release of the present invention cannot be achieved; Comparative Example 2 lacks a canopy modification layer, and the release situation is close to that of Example 1, with a slightly higher release rate. The absence of the canopy only affects the attachment of the microcapsules to the leaf surface and has little effect on the timing and targeted release; Comparative Example 3 uses conventional spray drying, which results in a greater loss of active ingredients compared to the embodiment. Although it does not affect the timing and targeted release functions, the overall drug loading capacity is reduced to a certain extent; in comparison, the embodiment microcapsules achieve a layered and sequential release characteristic, with light triggering the core layer to quickly release fluazifop-butyl, enzymatic hydrolysis triggering the middle layer to slowly release high-efficiency fluazifop-butyl, and humic acid triggering the shell layer to release glufosinate-ammonium, and each stage is separated from each other.

[0090] Experimental Example 2

[0091] The microcapsule herbicides prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were tested in a field plot test. The specific test conditions are as follows:

[0092] A microencapsulated herbicide (active ingredient content: 10% fluazifop-butyl, 10% haloxyfop-ethyl, and 20% glufosinate-ammonium) was formulated into a dispersant at a total active ingredient dosage of 300 g / ha. Spraying was performed in densely weeded areas of soybean fields. Weed control efficacy and crop safety were assessed 1, 7, and 14 days after application. The drydown rate of broadleaf and grass weeds indicated the proportion of weeds that withered or died. Crop damage symptoms were also observed and recorded as "none" (no damage), "minor" (mild symptoms without growth impact), or "significant" (severe symptoms with growth inhibition). Rainfall occurred twice during the experiment, with an average 24-hour rainfall of 10 ml. Three replicate plots were used for each herbicide spray.

[0093] Table 4 Comparison of field plot test results of Experimental Example 2

[0094]

[0095] As can be seen from the above comparison results, the example formulations showed efficient and long-lasting control effects on both broadleaf weeds and grass weeds. One day after application, Examples 1 to 3 had already caused significant damage to the broadleaf weeds, with the broadweed wilting rate increasing to over 90% on the 7th day and nearly complete kill on the 14th day. Grass weeds showed a slow effect due to their physiological characteristics, but the example formulations showed a high wilting rate one week after application, and the control rate was further improved on the 14th day, significantly better than the comparative example. In comparison, the herbicidal spectrum and persistence of the comparative samples are somewhat insufficient. Although comparative example 1 has a rapid effect on broadleaf weeds in the early stage, the subsequent control of grasses is affected due to the simultaneous application of all ingredients. This is because the fast contact agent quickly burns the surface of the weeds, but hinders the conduction of the systemic conduction agent to the roots of the grass, resulting in subsequent grass regeneration; the embodiment uses multi-layer controlled release to separate the contact component of glufosinate ammonium and the systemic conduction grass herbicide in time, so that the two act synergistically rather than interfere with each other; in addition, the control effect of comparative examples 2 and 3 is also lower than that of the embodiment. Due to the lack of canopy, the herbicide in comparative example 2 has low adhesion to the leaf surface and insufficient residence time, thereby affecting the weed control effect; comparative example 3 uses spray drying, which causes the partial loss of the active ingredient of the herbicide, and the actual active ingredient is lower than expected, resulting in the weed control effect, especially in the early stage.

[0096] In terms of crop safety, no symptoms of crop damage were observed in Examples 1 to 3, and the crops grew normally. This indicates that the multi-layer sustained-release formulation effectively reduced the instantaneous exposure concentration of the pesticides to the crops, avoiding the occurrence of pesticide damage. In contrast, the safety of the crops treated with the comparative examples was significantly poorer. Comparative Example 1 showed obvious pesticide damage after application, with severe burns and yellowing of the crop leaves. Significant signs of inhibition were still visible on the 7th day, and only a slight recovery was seen on the 14th day. This was because the instantaneous concentrations of the three pesticides in Comparative Example 1 were too high, resulting in a combined toxic effect on the crops.

[0097] In summary, the multi-layer controlled-release preparation process for a highly effective herbicide employed in this example not only ensures synergistic, broad-spectrum weed control with the three active ingredients, but also achieves controlled, timed release and a more rational distribution of efficacy. The result is greater weed control efficiency and a longer-lasting effect in the field, while also being safer for crops with no significant phytotoxicity.

Claims

1. A process for preparing a high-efficiency herbicide, characterized in that: The active ingredients of the high-efficiency herbicide are separated and encapsulated by microcapsules with a core layer, a middle layer, a shell layer, and a canopy layer; the microcapsules are prepared by microfluidic step-by-step encapsulation and fluidized bed spraying process, comprising the following steps: S1: A multiphase microfluidic device was used for sequential encapsulation. First, the oil phase containing fluazifop-butyl and photosensitizer was used as the core. Under acidic conditions, it was solidified with the aqueous phase diluted with HPMCP solution to form oil-in-water primary emulsion droplets to obtain core layer microparticles A. Secondly, a solution containing haloxyfop-butyl and a plant hormone analogue is mixed with PLGA to form secondary emulsion droplets, which are coated on the surface of the core layer microparticles A and solidified to obtain the middle layer microcapsules B; then a chitosan-catechol polymer solution containing glufosinate ammonium, humic acid-iron complex and FeCl3 is added to the microcapsules B and fed into a microfluidic device for further emulsification and gelation, and cross-linked and solidified to form a shell layer, thereby obtaining a core-shell multilayer microcapsule suspension C; S2: spray granulating the core-shell multilayer microcapsule suspension C to obtain wet microparticles D, and then spraying the wet microparticles D with a leaf-friendly polymer material solution in a fluidized bed to form a canopy modification layer coating; S3: The wet microgranules D coated with S2 are pre-frozen and then freeze-dried under low-temperature vacuum conditions to obtain dry microcapsule herbicide.

2. A process for preparing a high-efficiency herbicide according to claim 1, characterized in that: The mass ratio of fluazifop-butyl, halofop-ethyl and glufosinate described in S1 during preparation is 1:1:1; the mass ratio of the photosensitizer described in S1 to the fluazifop-butyl during preparation is 1:10; the mass ratio of the HPMCP described in S1 to the fluazifop-butyl during preparation is 1:0.625; the mass ratio of the plant hormone analogue described in S1 to the high-efficiency fluazifop-butyl during preparation is 1:50; the mass ratio of the PLGA described in S1 to the high-efficiency fluazifop-butyl during preparation is 2:1; the mass ratio of the humic acid-iron complex described in S1 to the glufosinate during preparation is 1:2.5; the mass ratio of the FeCl3 described in S1 to the glufosinate during preparation, calculated in the form of FeCl3·6H2O, to the glufosinate is 1:5; the mass ratio of the chitosan-catechol polymer described in S1 to the glufosinate during preparation is 1:

1.

3. The process for preparing a high-efficiency herbicide according to claim 1, wherein: The photosensitizer described in S1 is any one or more of a benzophenone photoinitiator, a chlorophyll derivative pheophorbide a or a bacterial chlorophyll derivative; the plant hormone analogue described in S1 is any one or more of naphthylacetic acid, 6-benzyladenine or an abscisic acid analogue.

4. The process for preparing a high-efficiency herbicide according to claim 1, wherein: The acidic conditions described in S1 are achieved by adding acetate buffer; the formation of water-in-oil primary emulsion droplets described in S1 specifically includes the use of a dual-channel microfluidic T-shaped connector, the inner phase is the oil phase, and the outer phase is the water phase, which are pushed in at different flow rates at 25°C to form water-in-oil primary emulsion droplets under shear action.

5. A process for preparing a high-efficiency herbicide according to claim 4, characterized in that: The pushing at different flow rates specifically includes pushing the inner phase at a flow rate of 0.5 mL / min and pushing the outer phase at a flow rate of 1.5 to 2.5 mL / min.

6. A process for preparing a high-efficiency herbicide according to claim 1, characterized in that: The co-emulsification described in S1 to form secondary emulsion droplets includes first forming a W / O type primary emulsion and then preparing W / O / W double emulsion droplets through a coaxial capillary microfluidic device.

7. The process for preparing a high-efficiency herbicide according to claim 1, wherein: The gel is further emulsified in the microfluidic device as described in S1, specifically, the microcapsule B is used as the dispersed phase, the chitosan-catechol polymer solution containing glufosinate, humic acid-iron complex and FeCl3 is used as the continuous phase, and a double emulsion is formed through the microfluidic device at a flow ratio of 1:4 to 1:

6.

8. The process for preparing a high-efficiency herbicide according to claim 1, wherein: The specific process of the spray granulation described in S2 includes setting the inlet temperature of the spray equipment to 40°C and rapidly spray drying to form fine particles with a moisture content of 20%; the specific parameters of the spraying in a fluidized bed described in S2 include a spray rate of 4 to 6 mL / min and a spraying time of 25 to 35 minutes; the foliage-friendly polymer material solution described in S2 is a mixture of polyvinyl alcohol, silicone spreader and water.

9. The process for preparing a high-efficiency herbicide according to claim 1, wherein: The pre-freezing described in S3 is to pre-freeze at a low temperature of -40°C for 2 hours; the freeze-drying under low-temperature vacuum conditions described in S3 is to sublimate and dry at -30°C and a vacuum degree of 0.1 mbar for 24 hours.

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