Pre-emergence weeding water dispersible granule and preparation method thereof

Abstract

The invention relates to the technical field of herbicides, in particular to pre-emergence weeding water dispersible granules and a preparation method thereof.The pre-emergence weeding water dispersible granules are prepared from, by mass, 25%-75% of main agents, 20%-50% of filler, 5%-15% of functional auxiliaries and 8%-20% of other auxiliaries; the main agent is composed of saflufenacil and triaziflam in a mass ratio of (2-6): 1; the filler is composed of a copper oxalate-loaded attapulgite complex and calcined diatomite in a mass ratio of 1: (1.8-2.5), and the loading rate of copper oxalate is 8-12%; the functional auxiliary agent comprises dicyandiamide and ammonium sulfate, and the mass ratio of the triaziflam to the dicyandiamide to the ammonium sulfate is 1: (0.05-0.08): (0.8-1.2); the other auxiliary agents comprise a wetting agent and a dispersing agent in a mass ratio of 1: (3-4); through cooperation of multiple components, the performance is improved in a breakthrough mode, and the finished product is a granular solid, is good in fluidity, does not adhere to the wall after being poured and does not remain in a packaging container to form secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of herbicide technology, and more particularly to a pre-emergence herbicide water-dispersible granule and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art.

[0003] Pre-emergence herbicides, as a core means of weed control in farmland, face multiple technical challenges. The core issue lies in how to achieve sustained and effective control of weed seeds using limited dosages in complex soil environments. This process requires overcoming not only the dynamic changes in the soil environment but also addressing the challenges of asynchronous weed germination and the development of herbicide resistance.

[0004] In practical field applications, pre-emergence herbicides need to form a stable control zone in the soil surface. This control zone needs to quickly establish effective concentrations, maintain long-term control effects, and adapt to changing climatic conditions. However, existing technologies struggle to meet these requirements simultaneously. Heavy rains can wash away herbicides, causing them to migrate to deeper soil layers and become ineffective, while drought hinders the even distribution of herbicides in the topsoil. Furthermore, weed seed banks exhibit asynchronous germination and resistance evolution, making it difficult for a single herbicide to achieve sustained coverage. The germination periods of different weed species can differ by more than 25 days, leading to the rapid emergence of late-stage weeds after early herbicide consumption. Simultaneously, the proportion of resistant weeds in the soil seed bank increases by 15% annually, and the efficacy of a single herbicide decreases by over 50% after three years of application.

[0005] To address these challenges, current herbicides often employ a combination of multiple active ingredients to achieve a holistic approach. For example, sulfadiazine, a fast-acting contact herbicide, can rapidly kill emerging broadleaf weeds within 24 hours, while trifluralin, by inhibiting acetyl-CoA carboxylase, continuously blocks weed seed germination, providing long-lasting weed control for over 21 days, primarily targeting grassy weeds. The combination of these two herbicides can cover over 95% of the weed spectrum, including resistant goosegrass, with an overall control efficacy 15-20 percentage points higher than that of a single herbicide, and significantly delaying the development of resistance.

[0006] However, despite the significant biochemical synergistic advantages of combining bensulfuron-methyl and trifluralin, the industrialization of their formulation remains hindered. This is because bensulfuron-methyl requires high apparent solubility to achieve rapid diffusion and form an initial film, which causes trifluralin to prematurely escape carrier control. Conversely, delaying trifluralin release using conventional slow-release technology inhibits the diffusion rate of bensulfuron-methyl. More seriously, in the optimal formulation of water-dispersible granules (WDG), the rapid disintegration characteristic causes the two components to separate in the soil: bensulfuron-methyl leaches downwards due to its high solubility, while trifluralin becomes ineffective on the surface due to photodegradation, ultimately leading to the failure of the control zone. Current technologies cannot achieve truly effective long-term control while preserving the advantages of WDG formulations. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a pre-emergence herbicidal water-dispersible granule of pyrimethanil-triflumethin that can synergistically exert fast-acting and long-acting herbicidal activity and is resistant to heavy rain erosion, thereby solving the problems of poor compound stability and insufficient duration of effect caused by the difference in the physicochemical properties of the two agents.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A pre-emergence herbicide water-dispersible granule, comprising, by weight percentage: 25%–75% main agent, 20%–50% filler, 5%–15% functional adjuvant, and 8%–20% other adjuvants.

[0010] The main agent is composed of pyrimethanil and trifluralin in a mass ratio of 2 to 6:1;

[0011] The filler consists of an attapulgite composite loaded with copper oxalate and calcined diatomaceous earth in a mass ratio of 1:1.8 to 2.5, with a copper oxalate loading rate of 8 to 12%.

[0012] Weeds hydroxylate trifluralin using cytochrome P450 monooxygenase, converting it into an inactive, water-soluble metabolite that is excreted. This is a major pathway by which weeds develop resistance. In this invention, the addition of a copper oxalate-loaded attapulgite complex... 2+ It can specifically bind to the heme cofactor of P450 enzymes, causing them to lose their electron transport ability; oxalate can also form ionic bonds with arginine residues in the enzyme's active site, hindering the metabolism of trifluralin and increasing its active lifespan.

[0013] The attapulgite composite and calcined diatomaceous earth are composed of attapulgite in a mass ratio of 1:1.8 to 2.5. The two can intertwine to form a three-dimensional network with both mechanical support and adsorption functions. This allows the fibrous skeleton of attapulgite and the porous structure of diatomaceous earth to complement each other. This not only prevents pesticide migration through physical barriers, but also uses the high specific surface area to adsorb and fix the main agent. This maintains the stability of the pesticide film on the soil surface under heavy rain erosion, while ensuring the uniform distribution of copper oxalate to exert its catalytic effect, thus achieving synergistic optimization of anti-leaching and long-term weed control.

[0014] The copper oxalate loading rate mentioned above ensures that the copper oxalate nanoparticles fully cover the carrier surface, while avoiding excessive loading that could cause the hydrophobic attapulgite fiber structure to break. At the same time, it controls the solubility of heavy metal ions in the soil to below 0.1 mg / L.

[0015] The functional adjuvants include dicyandiamide and ammonium sulfate, with a mass ratio of trifluralin, dicyandiamide, and ammonium sulfate of 1:0.05–0.08:0.8–1.2. More specifically, by controlling the ratio of dicyandiamide to ammonium sulfate, the ammonium nitrogen produced by the dissociation of ammonium sulfate can enhance the permeability of weed cell membranes to herbicides, promoting the penetration of pyrimisulfuron and trifluralin into weed seeds or young roots. Dicyandiamide, by inhibiting the activity of nitrifying bacteria in the soil, blocks the conversion of ammonium nitrogen to nitrate nitrogen, reduces the decomposition loss of trifluralin in the soil, and significantly extends its residual effect.

[0016] Other additives consist of wetting agents and dispersants in a mass ratio of 1:3 to 4.

[0017] Preferably, the calcined diatomaceous earth has a particle size of 15–25 μm and a specific surface area ≥40 m². 2 / g, pH value 6.5–7.5, oil absorption value 60–80g / 100g. The finer particle size provides a larger contact area, promoting uniform adsorption of the main agent particles (benzylsulfuron and trifluralin) and reducing sedimentation; while the higher specific surface area enhances the capillary adsorption capacity for water, ensuring rapid disintegration of the formulation upon contact with water; at the same time, this particle size range avoids the particle agglomeration problem caused by excessively fine powder, ensuring flowability during granulation; combined with the three-dimensional network structure of attapulgite, a stable suspension system is formed, which can maintain excellent dispersibility even at high main agent contents.

[0018] The oil absorption value within the above range allows calcined diatomaceous earth to physically adsorb and lock in easily leached pyrimisulfuron molecules, slowing down their migration rate under rainwater erosion. At the same time, because its oil absorption capacity is not oversaturated, it can avoid completely encapsulating trifluralin and hindering its long-term weed control release.

[0019] Preferably, the copper oxalate-loaded attapulgite composite consists of copper oxalate nanoparticles loaded onto hydrophobic attapulgite. The contact angle of the hydrophobic attapulgite is ≥120°, and the hydrophobic attapulgite has a fibrous structure with an aspect ratio ≥12. The high aspect ratio of the fibrous structure provides a larger surface area and microporous channels, enabling uniform distribution of copper oxalate nanoparticles, avoiding local agglomeration, significantly improving the catalytic efficiency of copper oxalate, and minimizing the collapse of the fibrous structure during wet milling. During granulation, the fibrous structure is interleaved with the flaky diatomaceous earth to form a stable three-dimensional network framework, improving the mechanical strength of the particles and rapidly disintegrating upon contact with water, ensuring rapid release of the reagent.

[0020] The contact angle of hydrophobic attapulgite soil ≥120° endows the attapulgite soil composite with superhydrophobicity, forming a physical barrier against rainwater erosion. This keeps the leaching rate of the loaded copper oxalate nanoparticles at a low level under heavy rain, while also preventing excessive dissolution of pyrimisulfuron by soil moisture, thus ensuring the slow-release balance of the pesticide.

[0021] Preferably, this invention employs a silane coupling agent wet grinding process to firmly anchor copper oxalate nanoparticles onto the surface of attapulgite, thus solving the catalyst detachment problem caused by traditional physical mixing. The method for loading copper oxalate nanoparticles onto hydrophobic attapulgite includes:

[0022] (1) Prepare a silane coupling agent-ethanol solution with a concentration of 2.5-3.5%; more specifically, utilize the polarity of ethanol to dissolve the silane coupling agent, providing a uniform dispersion medium for subsequent modification;

[0023] (2) Add hydrophobic attapulgite and silane coupling agent-ethanol solution to a solid-liquid ratio of 1:4 to 6 and wet grind to 600 mesh, controlling the temperature to ≤30℃; More specifically, in this process, the low temperature inhibits the grinding heat that causes silane hydrolysis failure, ensuring the integrity of hydrophobic modification, and the solid-liquid ratio of 1:4 to 6 provides sufficient shear force to orient the attapulgite fibers and expose active sites, while the liquid medium buffers mechanical damage, creating a highly active surface for copper oxalate anchoring;

[0024] (3) Add copper oxalate nanoparticles to the system and continue grinding for 8-10 min. After centrifugation, filtration, drying, and sieving, the copper oxalate-loaded attapulgite composite is obtained. More specifically, in this process, grinding promotes the embedding of copper oxalate nanoparticles into the hydrophobic microdomains of hydrophobic attapulgite through hydrogen bonds and van der Waals forces. This avoids excessive grinding that could lead to nanoparticle breakage or detachment, while ensuring that the catalytic sites are fully exposed, thus forming a stable attapulgite composite.

[0025] Preferably, in step (2), yttrium-stabilized zirconium oxide beads are used for wet grinding, and the grinding chamber filling rate is 65-70% (by volume). More specifically, yttrium-stabilized zirconium oxide beads, with their high hardness, high density, and chemical stability, generate strong impact and shear force on the material during wet grinding, ensuring that the hydrophobic attapulgite clay and copper oxalate nanoparticles are ground to a fine particle size. At the same time, their chemical inertness prevents metal ions from contaminating the copper oxalate catalytic sites, thus ensuring the purity and efficiency of the free radical catalytic reaction from the source.

[0026] A 65% lower limit for filling ensures that the collision frequency of the grinding beads is maximized, shortening the grinding time and avoiding excessive shearing and breakage of copper oxalate nanoparticles. A 70% upper limit precisely suppresses the temperature rise of the slurry and avoids the risk of silane hydrolysis failure.

[0027] Preferably, the dispersant is a mixture of lignin sulfonate and polycarboxylate in a mass ratio of 1.5 to 4:1; the wetting agent is fatty alcohol polyoxyethylene ether or alkyl naphthalene sulfonate; wherein the dispersant accounts for 6 to 13% of the mass of the water-dispersible granules, and the wetting agent accounts for 2 to 5% of the mass of the water-dispersible granules.

[0028] Among them, lignin sulfonate provides steric hindrance, polycarboxylate enhances electrostatic repulsion, and polycarboxylate has a strong effect on Ca. 2+ / Mg 2+ The chelating ability ensures that the formulation can still be stably dispersed under hard water conditions, avoiding flocculation. The two work together to prevent the agglomeration of high-content main agent particles. The wetting agent can significantly reduce the surface tension of the drug solution, so that the particles are completely wetted within 30 seconds after contact with water, and promote the capillary water absorption of the porous structure of diatomaceous earth, shortening the disintegration time.

[0029] The dispersant at the above-mentioned proportion can effectively prevent the main agent from agglomerating and hard water from flocculating by relying on the steric hindrance of lignin sulfonate and the electrostatic repulsion and chelating ability of polycarboxylate. It also avoids insufficient dispersion due to too low dosage or increased cost and affected flowability due to too high dosage, thus achieving a balance between dispersion performance and cost.

[0030] Wetting agents within the above-mentioned proportion range can quickly reduce the surface tension of the drug solution, promote rapid wetting of particles and accelerate disintegration, while avoiding the problems of poor wetting effect due to insufficient dosage and deterioration due to excessive dosage.

[0031] Preferably, the lignin sulfonate is sodium lignin sulfonate with a molecular weight of 20,000–50,000 Da and a degree of sulfonation of 2.0–2.8 mmol / g. More specifically, sodium lignin sulfonate has the advantages of readily available and inexpensive raw materials, and the salt structure formed by the combination of sodium ions and sulfonic acid groups has excellent water solubility, which can dissociate into negatively charged polymer chains in water, providing good steric hindrance and electrostatic repulsion. At the same time, the hydrophilic sulfonic acid groups and hydrophobic lignin skeleton in its molecule endow it with outstanding surface properties. Compared to other metal salts such as calcium and magnesium lignin sulfonates, it is less prone to precipitation in water and has stronger stability. This molecular weight range can form a steric hindrance layer of suitable thickness on the surface of the main agent particles, avoiding insufficient steric hindrance due to too low a molecular weight or affecting water solubility due to too high a molecular weight. The degree of sulfonation of 2.0 to 2.8 mmol / g can precisely regulate the hydrophilic-hydrophobic balance, ensuring sufficient electrostatic repulsion during dissociation in water, while maintaining good compatibility with the hydrophobic carrier and trifluralin main agent, synergistically preventing particle aggregation and delaying the photolysis of trifluralin.

[0032] The polycarboxylate is an acrylic acid-maleic anhydride copolymer with a molecular weight of 5000–8000 Da and a carboxyl group density of 4.5–5.2 meq / g. More specifically, the carboxyl groups (-COOH) provided by acrylic acid dissociate in water to carboxylate groups (-COO₂). - It is adsorbed onto the surface of the main agent particles through strong electrostatic repulsion, and at the same time reacts with Ca. 2+ / Mg 2+ Chelation ensures dispersion stability under hard water conditions. The anhydride group (-CO-O-CO-) of maleic anhydride hydrolyzes to generate double carboxyl groups with a carboxyl density of 4.5–5.2 meq / g, which enhances electrostatic repulsion and metal ion chelation ability. Furthermore, its rigid structure works synergistically with the flexible segments of acrylic acid to form a suitable molecular conformation. In addition, its low molecular weight of 5000–8000 Da allows it to quickly penetrate microcracks in particles and accelerate disintegration. At the same time, the polar groups of acrylic acid form hydrogen bonds with pyrimethanil, promoting the diffusion of the pesticide to form an initial film and solving the leaching problem. Preferably, the HLB value (hydrophilic-lipophilic balance value) of the fatty alcohol polyoxyethylene ether is 13-16, and the ethylene oxide addition number is 7-9. More specifically, the HLB value within this range can ensure rapid reduction of surface tension in the aqueous system, promoting the spreading and penetration of water-dispersible granules on the soil surface, and can also form a synergistic effect with the hydrophobic attapulgite soil carrier, avoiding the agglomeration of the agent on the soil surface due to hydrophobicity. The ethylene oxide addition number of 7-9 determines the density of hydrophilic groups in the molecular chain. Within this range, the molecule can form hydrogen bonds with water molecules through hydroxyl groups, ensuring solubility and wettability in water, and will not reduce compatibility with hydrophobic main agents (such as trifluralin) due to excessively long hydrophilic chains. Thus, after disintegration, it helps the main agent to be evenly dispersed in the soil topsoil, avoiding the impact of uneven local concentration on the control effect.

[0033] The alkyl naphthalene sulfonate is sodium diisopropylnaphthalene sulfonate with a purity ≥90%. More specifically, the β-branched structure of sodium diisopropylnaphthalene sulfonate (compared to the straight-chain isomer) significantly reduces steric hindrance, allowing it to quickly wedge into the 15–25 μm pores of calcined diatomaceous earth. This forces water to permeate the pores through capillary action, shortening the disintegration time to within 30 seconds and ensuring the complete establishment of the drug film before heavy rain. Furthermore, the aforementioned branched structure simultaneously blocks the formation of conjugated π bonds, avoiding the defects of straight-chain alkyl naphthalene sulfonate in absorbing ultraviolet light. Combined with the ≥90% high purity, which eliminates photocatalytic side reactions caused by impurities, the photolytic inactivation rate of trifluralin on the surface is greatly reduced.

[0034] The second objective of this invention is to provide a method for preparing a pre-emergence water-dispersible granule for weed control. The prepared water-dispersible granule has good control effect, stable physical and chemical properties, and is not easily decomposed or deteriorated. The finished product is a granular solid with good flowability. It does not stick to the wall after being poured and will not remain in the packaging container to cause secondary pollution.

[0035] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0036] A method for preparing a pre-emergence herbicide water-dispersible granule, the method comprising:

[0037] S1. Copper oxalate nanoparticles were loaded onto hydrophobic attapulgite to obtain a copper oxalate-loaded attapulgite composite for later use.

[0038] S2 involves uniformly mixing calcined diatomaceous earth, the main agent, functional additives, and other additives, and then air-jet milling to a particle size of 10–15 μm to obtain ultrafine powder. In this step, air-jet milling refines each component to the nanoscale and mixes them uniformly. The porous structure of calcined diatomaceous earth forms a nanoscale composite system with the main agent, functional additives, and other additives. This ensures the uniformity of adsorption of the main agent on the carrier surface and provides a fine powder skeleton for subsequent granulation, avoiding prolonged disintegration time or decreased suspension stability due to uneven particle size.

[0039] S3. The copper oxalate-loaded attapulgite composite from step S1 and the ultrafine powder from step S2 are added to a mixer in proportion and dry-mixed. In this step, the attapulgite composite and the ultrafine powder are dry-mixed rather than co-crushed to avoid mechanical damage to the fiber structure of the attapulgite composite, maintain the integrity of the three-dimensional network skeleton, and ensure that the diatomite pores and carrier fibers synergistically adsorb the main agent during granulation, thus preventing the separation of components in the soil.

[0040] S4 sprays atomized water into the mixing system for kneading, and then adds it to the extrusion granulator for granulation into particles with a diameter of 0.4 to 2.0 mm;

[0041] S5 After drying and sieving the granules obtained in step S4, water-dispersible granules are obtained.

[0042] Preferably, in step S2, the inlet air temperature for pulverizing is between 10 and 25°C, and the pressure is between 0.8 and 1.0 MPa. More specifically, the low temperature prevents the main agent from decomposing due to heat generated during high-speed pulverization, maintains the chemical activity of pyrimisulfuron-methyl and trifluralin, and prevents the high-temperature agglomeration of copper oxalate nanoparticles; within the above pressure range, sufficient kinetic energy can be provided to the pulverizing process through airflow or mechanical force, so that the material obtains sufficient collision and shearing forces in the pulverizing chamber, achieving effective particle breakage and ensuring product fineness.

[0043] Preferably, in step S4, the moisture content of the material is controlled at 18±0.5%; the granulation temperature is between 25 and 40°C. More specifically, precisely controlling the moisture content within 18±0.5% ensures that the dispersant and wetting agent form a uniform colloidal film during kneading, encapsulating the main agent and filler particles. This prevents uneven kneading due to insufficient moisture or agglomeration due to excessive moisture, ensuring suitable plasticity of the material during granulation. The low-temperature granulation at 25–40°C prevents the main agent from decomposing due to high temperature and maintains the stability of the fiber structure of the hydrophobic attapulgite composite.

[0044] Preferably, in step S5, the obtained particles are further subjected to fluidized bed drying. The dried particles are collected, sieved, and then columnar, uniform particles are obtained. The drying parameters for fluidized bed drying are: inlet air temperature of 50–85℃, and maintaining the moisture content of the discharged product at 0.8–1.5%. More specifically, in fluidized bed drying, the hot airflow keeps the particles in a fluidized, turbulent state, ensuring uniform heating and preventing localized overheating that could lead to decomposition of the active ingredient. Simultaneously, it rapidly removes moisture, forming smooth, columnar particles with a consistent aspect ratio, reducing dust adhesion. The gentle inlet air temperature prevents the active ingredient from decomposing and becoming ineffective due to high temperatures, while also rapidly evaporating moisture from the particles, ensuring stable drug activity. The low moisture content of 0.8–1.5% effectively prevents the particles from absorbing moisture and clumping during storage, while retaining an appropriate amount of porous structure to ensure rapid disintegration and uniform release of the drug upon contact with water.

[0045] The beneficial effects of the present invention are:

[0046] The essence of pre-emergence weed control lies in the formation of a sealed pesticide layer on the soil surface after application. When weed seeds germinate, the young shoots / radicles penetrate the pesticide layer to absorb the pesticide, which then acts on the seeds to inhibit cell division. This invention achieves a breakthrough in performance through multi-component synergy, with each component achieving a specific ratio and structural characteristics. A low-temperature wet grinding process is used to firmly anchor copper oxalate nanoparticles onto the carrier surface, reducing catalyst shedding and preventing nanoparticle aggregation. The segmented mixing steps ensure the uniformity of the main agent particle size and avoid mechanical damage to the copper oxalate-loaded attapulgite composite. Precisely controlled moisture content and temperature parameters ensure efficient and stable granulation, resulting in a final product with a molding rate of over 95% and a thermal decomposition rate of less than 0.5%, significantly improving the feasibility of industrial production.

[0047] This invention utilizes copper oxalate nanoparticles loaded onto a fibrous, hydrophobic attapulgite soil. The physical barrier formed by the hydrophobic carrier stabilizes the copper oxalate in soils with a pH range of 4.5–9.0. 2+ The catalytic generation of -OH free radicals by pyrimisulfuron increases oxidative damage to weed seed cell membranes. Simultaneously, oxalate competes with trifluralin metabolic intermediates for binding sites on P450 enzymes, blocking trifluralin's detoxification metabolism. This complex, combined with high-surface-area calcined diatomaceous earth, forms a three-dimensional network structure. This network provides skeletal support during granulation and acts as a purely physical suspension and dispersion carrier to adsorb the main agent particles, preventing sedimentation. The combined dispersion system with dispersants and wetting agents ensures disintegration and suspension stability, resulting in a suspension rate of over 96% after rapid disintegration of the water-dispersible granules, ensuring uniform pesticide distribution.

[0048] This invention controls the ratio of dicyandiamide to ammonium sulfate. The ammonium nitrogen produced by the dissociation of ammonium sulfate can enhance the permeability of weed cell membranes to herbicides, promoting the penetration of pyrimisulfuron and trifluralin into weed seeds or young roots. Dicyandiamide inhibits the activity of nitrifying bacteria in the soil, blocks the conversion of ammonium nitrogen to nitrate nitrogen, reduces the decomposition loss of trifluralin in the soil, and significantly extends its effective period. Detailed Implementation

[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0051] All raw materials or reagents used in the embodiments and / or comparative examples of this invention were purchased from mainstream manufacturers on the market. Those without specified manufacturers or concentrations are all analytical grade raw materials or reagents that are routinely available. There are no particular restrictions as long as they achieve the intended effect. The instruments and equipment used in this embodiment were all purchased from major manufacturers on the market. There are no particular limitations as long as they achieve the intended effect. Where specific techniques or conditions are not specified in this embodiment, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions.

[0052]

[0053]

[0054] The method for preparing copper oxalate nanoparticles loaded on hydrophobic attapulgite soil in the embodiments includes:

[0055] (1) Prepare a 3% silane coupling agent-ethanol solution;

[0056] (2) Add hydrophobic attapulgite clay and silane coupling agent-ethanol solution at a solid-liquid ratio of 1:5 and wet grind to 600 mesh, controlling the temperature to ≤30℃;

[0057] (3) Add copper oxalate nanoparticles to the system and continue grinding for 9 min. After centrifugation, filtration, drying and sieving, attapulgite composite loaded with copper oxalate is obtained; wherein, the copper oxalate loading rate (mass ratio) is 10%.

[0058] Example 1

[0059] The content of the pre-emergence weed control water-dispersible granules in this embodiment, calculated by mass fraction, is shown in Table 1.

[0060] Table 1. Content of pre-emergence weed-killing water-dispersible granules in Example 1

[0061]

[0062] The preparation method of the pre-emergence herbicidal water-dispersible granules in Example 1 includes:

[0063] S1 The above-mentioned copper oxalate-loaded attapulgite composite is screened for later use to ensure that the fiber structure is intact and free of agglomerated particles.

[0064] S2 weighs calcined diatomaceous earth, main agent, functional additives and other additives according to the formula in Table 1, mixes them and then pulverizes them to 12μm by airflow to obtain uniform ultrafine powder, wherein the pulverizing air inlet temperature is 20℃ and the pressure is 0.9MPa;

[0065] S3 adds the attapulgite composite and ultrafine powder into the mixer in proportion and dry mixes them at 50 rpm for 15 minutes.

[0066] S4 sprays atomized water into the mixing system, controls the material moisture content to 18%, and kneads it for 5 minutes at 30℃ to form a plastic material; it is then extruded through an extrusion granulator to produce columnar granules with a diameter of 1.0 mm.

[0067] The S5 uses a boiling drying process with an inlet air temperature of 65℃ to control the output moisture content at 1.0%. After drying, the granules are sieved to remove fine powder and obtain uniform columnar granules.

[0068] Example 2

[0069] The content of the pre-emergence weed control water-dispersible granules in this embodiment, calculated by mass fraction, is shown in Table 2.

[0070] Table 2. Content of pre-emergence weed-killing water-dispersible granules in Example 2

[0071]

[0072] The preparation method of the pre-emergence herbicidal water-dispersible granules in Example 2 includes:

[0073] S1 The above-mentioned copper oxalate-loaded attapulgite composite is screened for later use to ensure that the fiber structure is intact and free of agglomerated particles.

[0074] S2 weighs calcined diatomaceous earth, main agent, functional additives and other additives according to the formula, mixes them and then pulverizes them to 12μm by airflow to obtain uniform ultrafine powder. The pulverizing air inlet temperature is 15℃ and the pressure is 1.0MPa.

[0075] S3 adds the attapulgite composite and ultrafine powder into the mixer in proportion and dry mixes them at 60 rpm for 12 minutes.

[0076] S4 sprays atomized water into the mixing system, controls the material moisture content to 18.5%, and kneads it for 5 minutes at 35°C to form a plastic material; it is then extruded through an extrusion granulator to produce columnar granules with a diameter of 1.5 mm.

[0077] The S5 uses a boiling drying process with an inlet air temperature of 75℃ to control the output moisture content at 1.0%. After drying, the granules are sieved to remove fine powder and obtain uniform columnar granules.

[0078] Example 3

[0079] The content of the pre-emergence weed control water-dispersible granules in this embodiment, calculated by mass fraction, is shown in Table 3.

[0080] Table 3. Content of pre-emergence weed-killing water-dispersible granules in Example 3

[0081]

[0082]

[0083] The preparation method of the pre-emergence herbicidal water-dispersible granules in Example 3 includes:

[0084] S1 The above-mentioned copper oxalate-loaded attapulgite composite is screened for later use to ensure that the fiber structure is intact and free of agglomerated particles.

[0085] S2 weighs calcined diatomaceous earth, main agent, functional additives and other additives according to the formula, mixes them and then pulverizes them to 12μm by airflow to obtain uniform ultrafine powder. The pulverizing air inlet temperature is 22℃ and the pressure is 0.8MPa.

[0086] S3 adds the attapulgite composite and ultrafine powder into the mixer in proportion and dry mixes them at 60 rpm for 12 minutes.

[0087] S4 sprays atomized water into the mixing system, controls the material moisture content to 18.5%, and kneads it for 5 minutes at 35°C to form a plastic material; it is then extruded through an extrusion granulator to produce columnar granules with a diameter of 1.5 mm.

[0088] The S5 uses a boiling drying process with an inlet air temperature of 85℃ to control the output moisture content at 1.0%. After drying, the granules are sieved to remove fine powder and obtain uniform columnar granules.

[0089] Example 4

[0090] The content of the pre-emergence weed control water-dispersible granules in this embodiment, calculated by mass fraction, is shown in Table 4.

[0091] Table 4. Content of pre-emergence weed-killing water-dispersible granules in Example 4

[0092]

[0093]

[0094] The preparation method of the pre-emergence herbicidal water-dispersible granules in Example 4 includes:

[0095] S1 The above-mentioned copper oxalate-loaded attapulgite composite is screened for later use to ensure that the fiber structure is intact and free of agglomerated particles.

[0096] S2 weighs calcined diatomaceous earth, main agent, functional additives and other additives according to the formula, mixes them and then pulverizes them to 12μm by airflow to obtain uniform ultrafine powder. The pulverizing air inlet temperature is 22℃ and the pressure is 0.8MPa.

[0097] S3 adds the attapulgite composite and ultrafine powder into the mixer in proportion and dry mixes them at 60 rpm for 12 minutes.

[0098] S4 sprays atomized water into the mixing system, controls the material moisture content to 18.5%, and kneads it for 5 minutes at 35°C to form a plastic material; it is then extruded through an extrusion granulator to produce columnar granules with a diameter of 1.5 mm.

[0099] The S5 uses a boiling drying process with an inlet air temperature of 85℃ to control the output moisture content at 1.0%. After drying, the granules are sieved to remove fine powder and obtain uniform columnar granules.

[0100] Comparative Example 1

[0101] Unlike Example 1, hydrophobic attapulgite without copper oxalate nanoparticles was used instead of the attapulgite composite in Example 1.

[0102] Comparative Example 2

[0103] Unlike Example 3, dicyandiamide was replaced with an equal amount of ammonium sulfate. The content of the pre-emergence herbicidal water-dispersible granules in this comparative example, calculated by mass fraction, is shown in Table 5.

[0104] Table 5. Content of pre-emergence weed-killing water-dispersible granules in Comparative Example 2

[0105]

[0106] Comparative Example 3

[0107] Unlike Example 1, the copper oxalate-loaded attapulgite composite was added together with calcined diatomaceous earth, the main agent, functional additives, and other auxiliaries to obtain ultrafine powder. The specific method is as follows:

[0108] Q1 Weigh out the copper oxalate-loaded attapulgite composite, calcined diatomaceous earth, main agent, functional additives and other additives according to the formula in Table 1, mix them and then pulverize them to 12μm by airflow to obtain uniform ultrafine powder. The pulverizing air temperature is 20℃ and the pressure is 0.9MPa.

[0109] Q2 sprays atomized water into the ultrafine powder, controls the material moisture content to 18%, and kneads it for 5 minutes at 30℃ to form a plastic material; it is then extruded through an extrusion granulator to produce columnar granules with a diameter of 1.0 mm.

[0110] Q3 adopts a fluidized bed drying process with an inlet air temperature of 65℃, controls the output moisture content to 1.0%, and the dried granules are screened to remove fine powder, resulting in uniform columnar granules.

[0111] Comparative Example 4

[0112] Unlike Example 1, hydrophobic attapulgite loaded with ferrous oxalate nanoparticles was used instead of the attapulgite composite loaded with copper oxalate nanoparticles in Example 1.

[0113] The preparation method of hydrophobic attapulgite loaded with ferrous oxalate nanoparticles is as follows:

[0114] Hydrophobic attapulgite was dispersed in an ethanol solution (concentration 10 g / L), and ferrous oxalate nanoparticles were added (loading amount of 10-15% of the mass of attapulgite). The mixture was ultrasonically treated in an ice-water bath (power 300 W, time 30 min) to allow the nanoparticles to adsorb onto the surface and pores of the attapulgite fibers. Subsequently, the ethanol was removed by vacuum distillation, and the mixture was vacuum dried at 60 °C for 8 h to obtain hydrophobic attapulgite loaded with ferrous oxalate nanoparticles.

[0115] The pre-emergence herbicidal water-dispersible granules prepared in the examples and comparative examples were subjected to the following tests:

[0116] (1) Retention rate of pesticides in soil surface layer: The retention ratio of bensulfuron-methyl and trifluralin in the soil surface layer (0-5cm) after simulated rainstorm erosion directly reflects the leaching resistance of the formulation.

[0117] Test method:

[0118] Experimental setup: A columnar soil column (10cm in diameter and 30cm in height) was used, filled with sandy loam soil (2.3% organic matter content, pH 6.8), and compacted in layers to field capacity.

[0119] Chemical treatment: The pre-emergence herbicides water-dispersible granules prepared in the examples and comparative examples, as well as the traditional WDG formulation, were uniformly sprayed onto the surface of the soil column at an application rate of 80 g ai / hm. 2 Let it stand for 24 hours to form a film.

[0120] Simulated rainfall: A rainfall simulator was used to continuously spray water at an intensity of 30 mm / h for 2 hours.

[0121] Testing steps: After rainfall, soil samples were collected from the 0-5cm and 5-10cm layers. The pesticide was extracted with methanol using ultrasound, and the concentration was determined by HPLC. The surface retention rate was calculated as (total amount of pesticide in 0-5cm layer / total amount sprayed) × 100%.

[0122] (2) Weed control duration: The number of days that the herbicide effectively inhibits the germination of weed seeds after spraying, covering the germination cycle of different weed species;

[0123] Test methods

[0124] Pot experiment: Mixed seeds of corn (grass family) and broadleaf plants (purslane, shepherd's purse, and amaranth) (20% of which are resistant species) were sown in flower pots (soil depth 15cm).

[0125] Application of the herbicides: The pre-emergence herbicides prepared in the examples and comparative examples, as well as the traditional WDG formulation, were sprayed separately, with a blank control included. The application rate for all formulations was 80 g ai / hm.2 .

[0126] Observation period: Record the number of weeds that emerge daily. An emergence rate of <5% is considered an effective weed control standard. Count the number of days from application of pesticide to an emergence rate of more than 5%.

[0127] (3) Trifluralin metabolism inhibition rate: The proportion of reduced production of trifluralin hydroxylated metabolites in weeds reflects the inhibitory effect of copper oxalate on P450 enzymes.

[0128] Test methods

[0129] Cultivation of resistant weeds: Select a population of goosegrass resistant to trifluralin (resistance multiple 12 times) and hydroponically cultivate until the two-leaf-one-heart stage.

[0130] Chemical treatment: The leaves were sprayed with the pre-emergence herbicides water-dispersible granules prepared in the examples and comparative examples, with a concentration of 100 mg / L. The granules were sprayed evenly on the leaves using a spraying method, and the amount of solution sprayed per plant was 10 mL.

[0131] Metabolite detection: Leaves were collected 48 hours after application, metabolites were extracted with ethyl acetate, and the contents of trifluralin and its hydroxylated metabolites were determined by LC-MS / MS.

[0132] Calculation method: Metabolic inhibition rate = (Metabolite content of control formulation - Metabolite content of invention formulation) / Metabolite content of control formulation × 100%.

[0133] The pre-emergence herbicidal water-dispersible granules prepared in the examples and comparative proportions were subjected to the above tests, and the data in Table 6 were obtained.

[0134] Table 6 Test Data

[0135]

[0136]

[0137] Examples 1-4 demonstrated excellent performance in terms of soil surface herbicide retention rate, weed control duration, and trifluralin metabolic inhibition rate. The retention rate reached a maximum of 73.5%, primarily due to the three-dimensional network framework constructed by the copper oxalate-loaded attapulgite complex and calcined diatomaceous earth. This effectively prevented leaching loss of the herbicide under simulated heavy rain, ensuring its retention in the soil surface and providing sufficient active ingredients for subsequent weed control. The weed control duration reached 25-32 days, far exceeding traditional formulations. This is because the three-dimensional network framework, adjuvants, and main agent synergistically slowed the decomposition rate of main agents such as trifluralin. Simultaneously, the specific inhibitory effect of copper oxalate on weed P450 enzymes significantly reduced the rate of trifluralin metabolic inactivation by weeds, allowing the herbicide to maintain its inhibitory effect on weed seed germination for a longer period. The trifluralin metabolic inhibition rate reached 78.3% in the examples, mainly due to the Cu in the copper oxalate. 2+ The highly efficient coordination binding with the active site of the P450 enzyme precisely blocks the hydroxylation metabolic pathway of trifluralin, thereby effectively inhibiting the generation of metabolites and achieving optimized performance.

[0138] Compared with existing technologies, herbicides with a residual effect of more than 40 days are prone to causing phytotoxicity to subsequent crops. For example, propyzamide requires a 90-day interval before planting sensitive crops. This invention, while ensuring a sufficient control period, achieves precise degradation in 28-32 days through an adjustable copper oxalate loading rate (8-12%) and a compound structure of dicyandiamide and ammonium sulfate. It can be combined with crop rotation to reduce the risk of resistance, achieving a shorter safety interval and a lower risk of heavy metal accumulation in the soil.

[0139] Comparative Example 1, lacking copper oxalate loading, lacked the crucial inhibitory effect of Cu on P450 enzymes in its trifluralin metabolic inhibition. 2+ P450 enzymes, as key enzymes in the metabolism of trifluralin in weeds, are essential in the absence of Cu. 2+ Under coordination inhibition, the activity is unrestricted, leading to rapid metabolism of trifluralin, with a metabolic inhibition rate of only 10%. In terms of pesticide retention in the soil surface, due to the lack of a hydrophobic complex structure formed by copper oxalate and attapulgite, the pesticide cannot rely on this structure to resist rainwater erosion. A large amount of pesticide is leached into the deeper soil layers with the water flow, resulting in a retention rate of only 32.4%. These two disadvantages make it difficult for the pesticide to maintain an effective concentration in the soil, and the weed control effect is also greatly shortened to 15 days.

[0140] In Comparative Example 2, after replacing dicyandiamide with an equal amount of ammonium sulfate, the inhibitory effect of dicyandiamide on nitrifying bacteria was completely lost. As a result, ammonium nitrogen in the soil was rapidly oxidized to nitrate nitrogen, which led to the accelerated decomposition of trifluralin due to environmental changes. The weed control effect was significantly shortened to 18 days. At the same time, although ammonium sulfate can enhance the permeability of weed cell membranes, it cannot form a synergistic effect of promoting penetration and inhibiting decomposition when used alone. The stability of the agent in the soil was significantly reduced, and the agent retention rate in the soil surface was only 48.3%, which was far lower than the level in Example 2.

[0141] Comparative Example 3 employed a preparation method in which a copper oxalate-loaded attapulgite composite was added to other components and co-pulverized. During air jet milling, the strong mechanical force severely damaged the original fibrous skeleton structure of the attapulgite, causing the copper oxalate nanoparticles to detach from the attapulgite carrier. This prevented the maintenance of the original stable three-dimensional network adsorption structure, directly resulting in a sharp decline in the adsorption and retention capacity of the pesticide in the soil, with a pesticide retention rate of only 28.6% on the soil surface. Simultaneously, the detachment of copper oxalate made it difficult for the pesticide to effectively contact and inhibit the P450 enzyme in weeds, reducing the trifluralin metabolic inhibition rate to 39.2%, leading to a significant decrease in overall performance.

[0142] Comparative Example 4 used ferrous oxalate instead of copper oxalate. From the perspective of trifluralin metabolic inhibition, the binding constant of ferrous ions in ferrous oxalate to P450 enzymes was significantly higher than that of copper oxalate. 2+ Much lower, approximately Cu 2+ 1 / 70, which makes it unable to be like Cu 2+ It binds so effectively to the active site of the P450 enzyme, blocking the trifluralin metabolic pathway, with a metabolic inhibition rate of only 52.7%. In the soil environment, Fe... 2+ It is also easily oxidized to Fe by oxidants such as oxygen in the soil. 3+ This process disrupts the hydrophobic microzones on the surface of the attapulgite soil, resulting in a significant increase in the leaching rate of herbicides that were originally retained on the soil surface due to hydrophobicity. The herbicide retention rate on the soil surface is 55.1%, and the herbicide is not retained in the soil and has poor metabolic inhibition effect, which shortens the herbicide control effect to 20 days.

[0143] Traditional WDG formulations lack the three-dimensional network framework constructed from the copper oxalate-loaded attapulgite composite and calcined diatomaceous earth described in this invention, resulting in poor performance in various aspects.

[0144] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pre-emergence herbicide water-dispersible granule, characterized in that, Calculated by weight percentage, it includes 25%~75% main agent, 20%~50% filler, 5%~15% functional additives, and 8%~20% other additives: The main agent is composed of pyrimethanil and trifluralin in a mass ratio of 2-6:1; The filler is composed of an attapulgite composite loaded with copper oxalate and calcined diatomaceous earth in a mass ratio of 1:1.8~2.5, and the loading rate of copper oxalate is 8~12%. The functional additives include dicyandiamide and ammonium sulfate, and the mass ratio of trifluralin, dicyandiamide and ammonium sulfate is 1:0.05~0.08:0.8~1.2; The other additives are composed of wetting agents and dispersants in a mass ratio of 1:3 to 4.

2. The pre-emergence herbicide water-dispersible granules according to claim 1, characterized in that, The calcined diatomaceous earth has a particle size of 15~25μm and a specific surface area ≥40m². 2 / g, pH value is 6.5~7.5, and oil absorption value is 60~80 g / 100g.

3. The pre-emergence herbicide water-dispersible granules according to claim 1, characterized in that, The copper oxalate-loaded attapulgite composite consists of copper oxalate nanoparticles loaded on hydrophobic attapulgite. The contact angle of the hydrophobic attapulgite is ≥120°, and the hydrophobic attapulgite has a fibrous structure with an aspect ratio ≥12.

4. The pre-emergence herbicide water-dispersible granules according to claim 3, characterized in that, The method for loading copper oxalate nanoparticles onto hydrophobic attapulgite soil includes: Prepare a silane coupling agent-ethanol solution with a concentration of 2.5~3.5%; Add hydrophobic attapulgite clay and silane coupling agent-ethanol solution at a solid-liquid ratio of 1:4~6 and wet grind to 600 mesh, controlling the temperature to ≤30℃; Add copper oxalate nanoparticles to the system and continue grinding for 8-10 minutes. After centrifugation, filtration, drying, and sieving, the copper oxalate-loaded attapulgite composite is obtained.

5. The pre-emergence weed control water-dispersible granules according to claim 4, characterized in that, In step (2), the wet grinding uses yttrium-stabilized zirconium oxide beads as the grinding medium, and the grinding cavity filling rate is 65-70%.

6. The pre-emergence herbicide water-dispersible granules according to claim 1, characterized in that, The dispersant is a mixture of lignin sulfonate and polycarboxylate in a mass ratio of 1.5 to 4:1; the wetting agent is fatty alcohol polyoxyethylene ether or alkyl naphthalene sulfonate; wherein the dispersant accounts for 6 to 13% of the mass of the water-dispersible granules, and the wetting agent accounts for 2 to 5% of the mass of the water-dispersible granules.

7. The pre-emergence herbicide water-dispersible granules according to claim 6, characterized in that, The lignin sulfonate is sodium lignin sulfonate with a molecular weight of 20,000~50,000 Da and a degree of sulfonation of 2.0~2.8 mmol / g; the polycarboxylate is an acrylic acid-maleic anhydride copolymer with a molecular weight of 5,000~8,000 Da and a carboxyl density of 4.5~5.2 meq / g.

8. The pre-emergence herbicide water-dispersible granules according to claim 6, characterized in that, The fatty alcohol polyoxyethylene ether has an HLB value of 13-16 and an ethylene oxide addition number of 7-9; the alkyl naphthalene sulfonate is sodium diisopropyl naphthalene sulfonate with a purity ≥90%.

9. The method for preparing a pre-emergence herbicidal water-dispersible granule according to claim 1, characterized in that, The method for preparing the water-dispersible granules includes: S1. Copper oxalate nanoparticles were loaded onto hydrophobic attapulgite to obtain a copper oxalate-loaded attapulgite composite for later use. S2 mixes calcined diatomaceous earth, main agent, functional additives and other additives evenly, and then air-jet pulverizes it to a particle size of 10~15μm to obtain ultrafine powder; S3. The copper oxalate-loaded attapulgite composite from step S1 and the ultrafine powder from step S2 are added to a mixer in proportion and dry-mixed. S4 sprays atomized water into the mixing system for kneading, and then adds it to the extrusion granulator for granulation into particles with a diameter of 0.4~2.0mm; S5 After drying and sieving the granules obtained in step S4, water-dispersible granules are obtained.

10. The method for preparing a pre-emergence herbicidal water-dispersible granule according to claim 9, characterized in that, In step S4, the moisture content of the material is controlled at 18±0.5%; the granulation temperature is 25~40℃.

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