A granule of paraquat and a preparation method thereof

Abstract

This invention relates to a paraquat granule and its preparation method, belonging to the field of pesticide technology. The granule consists of paraquat salt, a layered double hydroxide carrier, a disintegrant, microcrystalline cellulose, an outer coating of an emetic / odorant / tracking agent, and the remainder being water-soluble filler. The granule wear rate is ≤2%, it completely disintegrates within 60 seconds in standard hard water at 25℃, and the suspension rate is ≥90%. Preparation employs a one-step process of screw extrusion-centrifugal granulation-vacuum belt drying or fluidized bed granulation, resulting in high content retention. The product is dust-free and non-caking, suitable for drone-based aerial spraying and long-distance sea transport, facilitating large-scale application in overseas registered areas.

Description

Technical Field

[0001] This invention relates to the field of pesticide technology, specifically to a granule form of paraquat and its preparation method. Background Technology

[0002] Paraquat (1,1′-dimethyl-4,4′-bipyridine cationic salt) is a non-selective contact herbicide belonging to the bipyridine class. It was first synthesized in 1958 by ICI (formerly Brunner Chemicals) in the UK and marketed under the trade name "Gramoxone" in 1962. Due to its broad spectrum of weed control, rapid onset of action (weeds wilt within 2 hours on sunny days), low root toxicity, and cost being only one-third that of glyphosate, it quickly became a core tool in no-till agriculture. However, its extreme toxicity to humans and animals remains a major concern for the industry's development: the FAO / WHO Joint Conference on Pesticide Standards classifies 200 g / L paraquat stock solution as a "Class Ib Extremely Hazardous" pesticide, with a lethal dose for adults of only 5–15 mL (approximately 40 mg / kg bw), and there is no specific antidote.

[0003] Existing technologies for paraquat granules still face numerous technical bottlenecks in terms of production processes, product performance, safety protection, and application compatibility, making it difficult to meet market demands.

[0004] CN1247026A discloses a method for preparing paraquat into powder and granules. This technology involves drying and pulverizing liquid paraquat dichloride under reduced pressure to produce powder, adding expanders and surfactants, and optionally adding emetics and odorants, to produce wettable powders and water-soluble granules. However, this technology requires high-temperature drying and pulverizing processes, which not only consumes a lot of energy but also poses a risk of dust leakage, inevitably causing environmental damage during the production process.

[0005] CN103734126B discloses a water-soluble granule containing paraquat dichloride and its preparation method. This method retains 5-20 wt% moisture in the formulation and incorporates humectants, surfactants, emetics, odorants, and other additives. It employs melt spray cooling or slurry cooling granulation processes to reduce processing dust, thus improving production safety to some extent. However, this technical solution still has inherent drawbacks: firstly, the product has a high moisture content, which can easily lead to granule clumping and adhesion during long-term storage due to moisture migration, affecting the fluidity and ease of use of the formulation. Furthermore, the high moisture content may accelerate the decomposition of the active ingredient in paraquat, reducing the product's storage stability; consequently, it significantly restricts the product's export application and makes it difficult to meet the long-term transportation requirements of ocean shipping.

[0006] CN104222088B discloses a water-soluble paraquat granule and its preparation method, which controls the water content of the paraquat mother liquor through negative pressure distillation and combines it with adsorbents, surfactants, and binders to achieve granulation. However, it still has significant shortcomings: it lacks specific safety protection design and effective control over the risk of accidental ingestion; moreover, its formulation relies on a simple combination of conventional adsorbents and adjuvants, without specific optimization of granule forming stability and dissolution and dispersion performance, making it difficult to ensure the consistency and reliability of application effect in practical applications.

[0007] While the existing technologies mentioned above propose converting paraquat aqueous solutions into granules, mitigating some of the safety risks associated with aqueous formulations, they fail to fully meet the high-quality requirements of modern pesticide applications. This is especially true for drone-based aerial spraying, widely used in large-scale, modern agriculture, which places stringent demands on the rapid disintegration, uniform dispersion, and stable suspension of pesticides. Formulations prepared using existing methods may exhibit uneven dissolution rates, insufficient dispersion stability, and poor suspension effects in practical use. This not only affects application uniformity and weed control but may also lead to nozzle clogging due to incomplete granule disintegration, reducing operational efficiency. Furthermore, existing technologies still have shortcomings in product storage stability and comprehensive safety protection, and a technical solution that balances production feasibility, storage stability, application compatibility, and safety has not yet been developed. Therefore, developing a paraquat granule with superior performance and enhanced compatibility is of paramount necessity and urgency within the industry. Summary of the Invention

[0008] To address the aforementioned issues, and based on the company's overseas market strategy, the inventors tackled the technical challenges of paraquat through extensive research and development, achieving satisfactory results.

[0009] This invention is achieved through the following technical means:

[0010] This invention provides a paraquat granule specifically for export, composed of the following components: paraquat salt, layered double hydroxide carrier, disintegrant, microcrystalline cellulose, outer multifunctional coating layer, water-soluble filler, and adjuvants; and the granule abrasion rate is ≤2% (tested according to GB / T 33031-2016 "Test Method for Abrasion Resistance of Pesticides"), and under standard hard water conditions at 25℃, it completely disintegrates within 60 seconds in a 250mL graduated cylinder, with a suspension rate ≥90% (tested according to GB / T 14825-2023 "Test Method for Suspension Rate of Pesticides"), and can be directly added to the water tank of pesticide spraying machinery.

[0011] In a first aspect, the present invention provides a granule formulation of paraquat, the formulation comprising:

[0012] a) Paraquat salt 45–65 wt%; preferably 50–60 wt%, most preferably 55 wt%;

[0013] b) Layered double hydroxide support 10–25 wt%; preferably 15–20 wt%, most preferably 18 wt%;

[0014] c) 2–8 wt% disintegrant; preferably 4–6 wt%, most preferably 5 wt%;

[0015] d) Microcrystalline cellulose 2–5 wt%; preferably 2.5–3.5 wt%, most preferably 3 wt%;

[0016] e) An outer multifunctional coating layer comprising: an emetic, a malodorant, and a tracer, in a proportion of 1-5 wt%; preferably 2-4 wt%, most preferably 3 wt%;

[0017] f) The remainder consists of water-soluble fillers and additives; preferably a mixture of ammonium sulfate and mannitol, most preferably a mixture of ammonium sulfate / mannitol = 1:1 (for the inner layer) and ammonium sulfate (for the outer layer).

[0018] Furthermore, the paraquat salt is one or more of paraquat dichloro salt, paraquat dibromide salt, paraquat dimethyl sulfonate, and paraquat disulfate; preferably paraquat dichloro salt or paraquat dibromide salt.

[0019] Furthermore, the layered double hydroxide carrier is lactate or citrate intercalated hydrotalcite, chloride intercalated hydrotalcite, nitrate intercalated hydrotalcite, phosphate intercalated hydrotalcite, or sulfonate intercalated hydrotalcite; preferably, it is citrate intercalated hydrotalcite.

[0020] Furthermore, the disintegrant is sodium carboxymethyl starch, croscarmellose sodium, croscarmellose polyvinylpyrrolidone, or low-substituted hydroxypropyl cellulose; preferably croscarmellose sodium, and most preferably croscarmellose sodium with a water absorption swelling rate ≥300%.

[0021] Furthermore, the microcrystalline cellulose has a specific surface area (BET) of 0.8-1.3 m² / g, an average particle size (D50, laser particle size distribution) of 45-90 μm, and a moisture content (loss of moisture after drying at 105°C for 2 hours) of ≤7 wt%; preferably, it has a specific surface area of ​​1.0-1.2 m² / g, an average particle size of 60-70 μm, and a moisture content of ≤2 wt%.

[0022] Furthermore, in the aforementioned multifunctional coating layer:

[0023] The emetic is aminopropyltriazolylpyrimidinone or 2-methyl-5-hydroxytryptamine; preferably aminopropyltriazolylpyrimidinone.

[0024] The odorant is 2-methyl-2-propen-1-thiol, cyclohexanethiol, tert-butylthiol, dimethyl sulfide, dipropylene disulfide, isovaleric acid, hexanoic acid, 2-methylpyridine, 3-ethylpyridine; preferably tert-butylthiol, most preferably tert-butylthiol encapsulated in microcapsules (particle size 20-50 μm);

[0025] The tracking agent is potassium p-nitrobenzoate, sodium o-nitrobenzoate, sodium 2,4-dinitrophenolate, or sodium fluorescein; preferably potassium p-nitrobenzoate.

[0026] Furthermore, the water-soluble filler and additives are one or more of ammonium sulfate, sodium sulfate, sodium chloride, sodium bicarbonate, mannitol, sorbitol, sucrose, sodium citrate, and sodium acetate; preferably, one or two of ammonium sulfate and mannitol are used in combination, and most preferably, the outer layer uses ammonium sulfate and the inner layer uses a 1:1 mixture of ammonium sulfate and mannitol.

[0027] Furthermore, the water-soluble filler and additives account for 0–60% of the coating layer; preferably 0% or 53% (i.e., no additives are added in the fluidized bed liquid phase drug delivery process or ammonium sulfate accounts for 53.3% of the total mass of the coating layer in the extrusion and spheroidization solid phase drug delivery process).

[0028] Secondly, the present invention also provides a method for preparing paraquat granules (this method is a preferred preparation method), the specific steps of which are as follows:

[0029] a. Mix the paraquat salt mother liquor with the layered double hydroxide carrier, disintegrant, microcrystalline cellulose, and water-soluble filler (for the inner layer) (mixing paddle speed 200-1000 r / min, cutter speed 1000-3000 r / min, mixing time 1-5 min); preferably, the mixing paddle speed is 400-600 r / min, the cutter speed is 1800-2200 r / min, and the mixing time is 2-3 min; most preferably, the mixing paddle speed is 500 r / min. The mixture is prepared by mixing at 2000 rpm for 2 minutes, followed by extrusion granulation using a screw extruder (screw speed 5-15 Hz, screw mesh size 0.5-1.0 mm, water cooling temperature 5-20℃); preferably, the screw speed is 8-12 Hz, the screw mesh size is 0.7-0.9 mm, and the water cooling temperature is 12-18℃; most preferably, the screw speed is 10 Hz, the screw mesh size is 0.8 mm, and the water cooling temperature is 15℃; resulting in wet granules.

[0030] b. Mix the emetic, odorant, tracking agent, and water-soluble filler (for the outer layer) in the multifunctional outer coating (mixing paddle speed 200-1000 r / min, cutter speed 1000-3000 r / min, mixing time 1-5 min) for later use; preferably, the mixing paddle speed is 400-600 r / min, the cutter speed is 1800-2200 r / min, and the mixing time is 2-3 min; most preferably, the mixing paddle speed is 500 r / min, the cutter speed is 2000 r / min, and the mixing time is 2 min.

[0031] c. Using the wet granules obtained in step a as the core, feed them into a centrifugal granulator. While spraying deionized water, sprinkle dry powder onto the outer multifunctional coating mixture prepared in step b (rotary speed 100-500 r / min, powder-to-liquid ratio 10:1-5:1 (w / w), spraying rate 5-15 g / min); preferably, the rotary speed is 250-350 r / min, the powder-to-liquid ratio is 9:1-7:1 (w / w), and the spraying rate is 8-12 g / min; most preferably, the rotary speed is 300 r / min, the powder-to-liquid ratio is 8:1 (w / w), and the spraying rate is 10 g / min; to obtain paraquat granules.

[0032] d. Feed the wet paraquat granules into a vacuum belt dryer, controlling the vacuum degree to -0.07MPa to -0.09MPa, the drying temperature to 30–40℃, and the conveyor belt speed to 0.1–0.5 m / min (corresponding to a drying time of 0.5–2.5 h), and dehydrate until the granule moisture content is ≤2 wt%. Preferably, the vacuum degree is -0.075MPa to -0.085MPa, the drying temperature to 32–38℃, and the conveyor belt speed to 0.2–0.4 m / min (corresponding to a drying time of 1–2 h). Most preferably, the vacuum degree is -0.08MPa, the drying temperature to 35℃, and the conveyor belt speed to 0.3 m / min (corresponding to a drying time of 1.5 h), and finally dehydrate until the granule moisture content is ≤2%; obtain paraquat granules.

[0033] Thirdly, the present invention also provides another preparation method, the specific steps of which are as follows:

[0034] a. Mix paraquat salt mother liquor with layered double hydroxide carrier, disintegrant, microcrystalline cellulose and water-soluble filler (for inner layer), feed into a fluidized bed, and spray in deionized water to obtain pellet core a (airflow rate 3-20 m³ / h, airflow temperature 45-75℃, spraying speed 5-15 Hz, spraying atomization pressure 0.1-0.5 MPa); preferably, airflow rate 8-15 m³ / h, airflow temperature 55-65℃, spraying speed 8-12 Hz, and spraying atomization pressure 0.2-0.4 MPa;

[0035] b. Dissolve the emetic, odorant, tracing agent, and water-soluble filler (for the outer layer) in deionized water to prepare a solution b with a mass concentration of 5-15%; preferably a solution b with a mass concentration of 8-12%.

[0036] c. Connect solution b to a fluidized bed, and simultaneously dry the pellet core a while spraying solution b into it (airflow rate 3-20 m³ / h, airflow temperature 45-75℃, spraying speed 5-15 Hz, spraying atomization pressure 0.1-0.5 MPa, and continue drying for 5-30 min after spraying); preferably, the airflow rate is 8-15 m³ / h, the airflow temperature is 55-65℃, the spraying speed is 8-12 Hz, the spraying atomization pressure is 0.2-0.4 MPa, and continue drying for 10 min after spraying; the final granules have a moisture content ≤2%; and paraquat granules are obtained.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] 1. Greatly improves the convenience of medication use, adapting to the needs of large-scale, modern agricultural operations.

[0039] This invention achieves complete disintegration of granules within 60 seconds after they are added to the water tank of a spraying machine, with a stable suspension rate of ≥90%. The uniformity of the pesticide solution fully meets the requirements of "low sedimentation and high atomization" for drone spraying. It is also compatible with the high-speed operation process of large sprayers, greatly improving the application efficiency of large-scale planting and perfectly meeting the needs of modern agriculture for efficient, convenient and stable pesticide products.

[0040] 2. The particles have excellent physical properties, meeting the requirements of industrial production and long-distance transportation.

[0041] Existing granules often suffer from insufficient hardness and high abrasion rates, generating dust during production, packaging, and long-distance export transportation. This results in the loss of active ingredients and environmental pollution. This invention utilizes the binding and stabilizing effect of microcrystalline cellulose to achieve granules with high hardness, low abrasion rate, and physical strength sufficient to withstand the bumps and collisions during long-distance transportation by sea and land, thus reducing product loss during distribution.

[0042] 3. The formula and process are flexible and adjustable, precisely matching the needs of different overseas markets.

[0043] To cater to different crop types, climate conditions, and pesticide use regulations in various overseas regions, the paraquat salt content of this invention is significantly increased (45-65wt%). The carrier type and coating layer composition can be adjusted within a reasonable range. For example, the amount of disintegrant can be appropriately increased for tropical regions to adapt to high-temperature water environments, and the ratio of emetic to odorant can be optimized for regions with strict safety regulations, thereby enhancing the product's competitiveness in overseas markets. Attached Figure Description

[0044] Figure 1 This is a typical HPLC chromatogram of the sample content in Example 1;

[0045] Figure 2 This is a typical HPLC chromatogram of the sample content in Example 7;

[0046] Figure 3 The typical HPLC chromatogram of the sample content in Comparative Example 1 is shown.

[0047] Figure 4 This is a typical HPLC chromatogram of a reference standard used in content detection. Detailed Implementation

[0048] The high-content paraquat granules and their preparation method involved in this invention are only for export and sale to countries or regions where paraquat registration has been approved, and are not for sale or use within China.

[0049] Example 1 (Extrusion Centrifugal Granulation - Vacuum Belt Drying)

[0050] I. Formula Composition

[0051]

[0052] II. Process Steps

[0053] a. Mix paraquat dichloride mother liquor with citrate-intercalated hydrotalcite, cross-linked sodium carboxymethyl cellulose, microcrystalline cellulose and ammonium sulfate / mannitol (1:1) (for the inner layer) (mixing paddle speed 500 r / min, cutter speed 2000 r / min, mixing time 2 min), and granulate by screw extruder (screw speed 10 Hz, screw mesh diameter 0.8 mm, water cooling temperature 15 ℃) to obtain wet granules;

[0054] b. Mix the aminopropyltriazolylpyrimidinone, tert-butyritin, potassium p-nitrobenzoate, and ammonium sulfate (for the outer layer) in the multifunctional outer coating (mixing paddle speed 500 r / min, cutter speed 2000 r / min, mixing time 2 min) and set aside.

[0055] c. The wet granules prepared in step a are used as the core and fed into a centrifugal granulator. Deionized water is sprayed in while dry powder is sprinkled into the outer multi-functional coating mixture prepared in step b (rotary speed 300 r / min, deionized water is sprayed at a rate of 10 g / min, and the premixed powder in step 2 is sprinkled in at a uniform speed, powder: spray liquid mass ratio = 8:1), and wet granules of paraquat granules with outer coating are obtained.

[0056] d. Vacuum feed the wet paraquat granules and spread them evenly in a vacuum belt dryer. The vacuum degree is −0.08 MPa, the drying belt temperature is 35 ℃, and the conveyor belt speed is 0.3 m / min (total drying time is 1.5 h). Dehydrate until the granule moisture content is ≤2 wt% to obtain paraquat granules.

[0057] Examples 2-3 (Effects of using different active ingredients)

[0058] I. Formula Composition

[0059] Except for replacing paraquat dichloride in Example 1 with the active ingredient in each embodiment, the other ingredients and dosages are the same as in Example 1.

[0060] Example 2: The active ingredient is paraquat dibromide;

[0061] Example 3: The active ingredient is paraquat dimethyl sulfonate;

[0062] II. Process Steps

[0063] Same as in Example 1.

[0064] Example 4 (Effects of implementing different layered double hydroxide carriers)

[0065] I. Formula Composition

[0066] Except that the layered double hydroxide carrier in this embodiment is selected as chloride ion intercalated hydrotalcite instead of citrate intercalated hydrotalcite in Example 1, the other components and amounts are the same as in Example 1.

[0067] II. Process Steps

[0068] Same as in Example 1.

[0069] Examples 5-6 (Effects of implementing high and low drug loading)

[0070] I. Formula Composition

[0071]

[0072] II. Process Steps

[0073] Same as in Example 1.

[0074] Example 7 (One-step granulation with fluidized bed liquid phase loading)

[0075] I. Formula Composition

[0076] Same as in Example 1.

[0077] II. Process Steps

[0078] a. Preparation of pellet core: Paraquat dichloride, citrate-intercalated hydrotalcite, cross-linked sodium carboxymethyl cellulose, microcrystalline cellulose, and ammonium sulfate / mannitol (1:1) (for the inner layer) are mixed and fed into a fluidized bed for top spray granulation, followed by spraying deionized water; the air inlet volume is set to 12 m³ / h, the air inlet temperature to 60℃, the spraying speed to 10 Hz, and the spraying atomization pressure to 0.3 MPa to obtain pellet core a.

[0079] b. Preparation of coating solution: Dissolve the aminopropyltriazolylpyrimidinone, tert-butyritin, potassium p-nitrobenzoate, and ammonium sulfate (for the outer layer) in deionized water to prepare a 10% (w / w) solution.

[0080] c. Coating and drying: Connect solution b to the fluidized bed, perform bottom spray coating, spray solution b into pellet core a and dry simultaneously; set the air inlet volume to 12 m³ / h, air inlet temperature to 60℃, spraying speed to 10 Hz, and spraying atomization pressure to 0.3 MPa. After spraying, continue drying for 10 minutes to obtain paraquat granules.

[0081] Example 8 (One-step granulation of drug delivery in fluidized bed, without outer packing layer)

[0082] I. Formula Composition

[0083]

[0084] II. Process Steps

[0085] a. Preparation of pellet core: Paraquat dichloride, citrate-intercalated hydrotalcite, cross-linked sodium carboxymethyl cellulose, microcrystalline cellulose, and ammonium sulfate / mannitol (1:1) (for the inner layer) are mixed and fed into a fluidized bed for top spray granulation, followed by spraying deionized water; the air inlet volume is set to 12 m³ / h, the air inlet temperature to 60℃, the spraying speed to 10 Hz, and the spraying atomization pressure to 0.3 MPa to obtain pellet core a.

[0086] b. Preparation of coating solution: Dissolve the aminopropyltriazolylpyrimidinone, tert-butyritin, and potassium p-nitrobenzoate in the outer multifunctional coating into deionized water to prepare a 10% (w / w) solution.

[0087] c. Coating and drying: Connect solution b to the fluidized bed, perform bottom spray coating, spray solution b into pellet core a and dry simultaneously; set the air inlet volume to 12 m³ / h, air inlet temperature to 60℃, spraying speed to 10 Hz, and spraying atomization pressure to 0.3 MPa. After spraying, continue drying for 0.5 h to obtain paraquat granules.

[0088] Note: No need to dissolve the outer layer of ammonium sulfate, the total mass of the coating solution is reduced, the spraying time is shortened accordingly, and the overall process efficiency is significantly improved.

[0089] Example 9

[0090] I. Formula Composition

[0091] Except for the following two adjustments, the remaining components and dosages are completely consistent with Example 1 (extrusion centrifugal granulation route):

[0092]

[0093] II. Process steps: Same as Example 1 (extrusion centrifugal granulation - vacuum belt drying):

[0094] a. Mix paraquat dichloride mother liquor with citrate-intercalated hydrotalcite, sodium carboxymethyl starch, microcrystalline cellulose and ammonium sulfate / mannitol (1:1) (mixing paddle speed 500 r / min, cutter speed 2000 r / min, mixing time 2 min), and granulate by screw extruder (screw speed 10 Hz, screw mesh aperture 0.8 mm, water cooling temperature 15 ℃) to obtain wet granules;

[0095] b. Mix the aminopropyltriazolylpyrimidinone, tert-butyritin, sodium 2,4-dinitrophenolate and ammonium sulfate in the outer multifunctional coating (mixing paddle speed 500 r / min, cutter speed 2000 r / min, mixing time 2 min) for later use;

[0096] c. Same as step c in Example 1;

[0097] d. Same as step d in Example 1.

[0098] Example 10

[0099] I. Formula Composition

[0100]

[0101] II. Process Steps: Microcrystalline cellulose pretreatment: Drying is carried out by vacuum drying in an oven or by fluidized bed drying at a temperature of 70℃-90℃ for 2-3 hours, with moisture content controlled at <2%; or commercially available low-moisture microcrystalline cellulose that meets the standards (specific surface area 1.0-1.2 m² / g, average particle size 60-70μm, weight loss at 105℃ for 2h ≤2wt%) can be purchased directly for later use.

[0102] a. Mix paraquat dichloride mother liquor with citrate-intercalated hydrotalcite, cross-linked sodium carboxymethyl cellulose, low-moisture microcrystalline cellulose and ammonium sulfate / mannitol (1:1) (for the inner layer) (mixing paddle speed 500 r / min, cutter speed 2000 r / min, mixing time 2 min), and granulate by screw extruder (screw speed 10 Hz, screw mesh diameter 0.8 mm, water cooling temperature 15 ℃) to obtain wet granules;

[0103] b. Mix the aminopropyltriazolylpyrimidinone, tert-butyritin, potassium p-nitrobenzoate, and ammonium sulfate (for the outer layer) in the multifunctional outer coating (mixing paddle speed 500 r / min, cutter speed 2000 r / min, mixing time 2 min) and set aside.

[0104] c. The wet granules prepared in step a were used as the core and fed into a centrifugal granulator. Deionized water was sprayed in while dry powder was sprinkled into the outer multi-functional coating mixture prepared in step b (rotary speed 300 r / min, deionized water was sprayed in at a rate of 10 g / min, and the premixed powder in step 2 was sprinkled in at a uniform speed, with the powder-to-spray mass ratio = 8:1), and wet granules of paraquat were obtained.

[0105] d. Vacuum feed the wet paraquat granules and spread them evenly in a vacuum belt dryer. The vacuum degree is −0.08 MPa, the drying belt temperature is 35 ℃, and the conveyor belt speed is 0.3 m / min (total drying time is 1.5 h). Dehydrate until the granule moisture content is ≤2 wt% to obtain paraquat granules.

[0106] Comparative Example 1 (Refer to Example 1 of CN104222088B)

[0107] I. Formula Composition

[0108]

[0109] II. Process steps: a. Concentration of mother liquor: Take 158.4 kg of paraquat dichloride mother liquor (water content 58wt%), distill and dehydrate it under a pressure of -0.085 MPa until the water content of the concentrate is 30wt%, and obtain 83 kg of concentrate (equivalent to 58.1 kg of dry paraquat dichloride).

[0110] b. Material mixing: Transfer the concentrate to a closed mixing device, first add the adsorbent (6.4 kg sucrose + 1.6 kg sodium ethylenediaminetetraacetate), mix for 0.5 h; then add the surfactant (5 kg tallow amine polyoxyethylene ether) and binder (4 kg polyvinylpyrrolidone), continue mixing for 0.5 h to obtain the raw material mixture.

[0111] c. Extrusion granulation: The mixture is granulated using a twin-screw front extrusion granulation method at a granulation temperature of 45℃ (screw speed is set at the conventional 15HZ).

[0112] d. High-temperature drying: Place the wet granules in a hot air drying device and dry at 70℃ for 2 hours until the moisture content of the granules is ≤3wt%, to obtain paraquat water-soluble granules.

[0113] Test Example 1: Quality Testing of Representative Samples

[0114] According to relevant national standards or the inventor's internal standards, samples from relevant representative batches and embodiments were tested, and the specific test results are as follows.

[0115] Particle moisture content: (Internal control standard) Infrared rapid drying instrument, 105℃-5min, 2-3g of material.

[0116] Particle abrasion rate: Tested according to GB / T 33031-2016 "Test Method for Abrasion Resistance of Pesticides".

[0117] Disintegration: (Internal control standard) Under standard hard water conditions at 25℃, weigh 1g of particle size into a 250mL graduated cylinder for testing and record the time to complete disintegration.

[0118] Suspension rate: Tested according to GB / T 14825-2023 "Determination of Suspension Rate of Pesticides".

[0119] (25 ℃, n=3, average value)

[0120]

[0121] The samples from Examples 1 and 10 were sealed in commercially available packaging and placed in a sample box at a high temperature of 40°C and a high humidity of 75% ± 5%. The results were measured after 3 months.

[0122]

[0123] The above results show that:

[0124] The particle wear rate, disintegration, and suspension rate of the various embodiments of the present invention are significantly better than those of Comparative Example 1. In particular, the sample prepared by low-moisture microcrystalline cellulose in Example 10 showed no change in various test indicators when placed in a high temperature and high humidity environment, exhibiting excellent stability and performance, which is more conducive to long-distance transportation and export to tropical regions.

[0125] Experimental Example 2: Effect of different processes on the retention rate of paraquat dichloride

[0126] 1. Instruments and Reagents

[0127] Instruments: High-performance liquid chromatograph (UV detector), ultrasonic cleaner, 0.45μm aqueous filter membrane, agate mortar and pestle

[0128] Reagents: Paraquat dichloride standard (purity ≥99%), ammonium formate (analytical grade), acetonitrile (chromatographic grade), ultrapure water

[0129] 2 Chromatographic conditions

[0130] Chromatographic column: Cation exchange column (Whatman Partisil-10 SCX 250×4.6mm)

[0131] Mobile phase: 0.1 mol / L ammonium formate (pH 2.8) - acetonitrile = 85:15 (v / v), ultrasonic degassing for 10 min.

[0132] Flow rate: 1.0 mL / min

[0133] Detection wavelength: 254nm

[0134] Column temperature: room temperature

[0135] Injection volume: 10 μL

[0136] 3 Sample processing

[0137] Sampling: Take an appropriate amount of paraquat granules sample, grind and mix them, then weigh a sample containing a certain amount of paraquat ions (accurate to 0.0001g) and place it in a volumetric flask of appropriate specifications;

[0138] Dissolution: Add an appropriate amount of mobile phase and sonicate for a period of time (to ensure that the sample is fully dissolved), shaking as needed during the process;

[0139] Volumetric filtration: Add the mobile phase to the mark, shake well, and filter through a 0.45 μm aqueous filter membrane. Collect the filtrate for analysis.

[0140] 4. Preparation of standard solutions

[0141] Weigh out the paraquat dichloride standard, dissolve, dilute to volume, and filter it in the same way as in "3 Sample Processing" to obtain the standard solution.

[0142] 5. Measurement and Calculation

[0143] Determination: Inject the standard solution and sample solution into the chromatograph respectively, and record the chromatographic peak areas;

[0144] Calculation: The paraquat ion content in the sample was calculated using the external standard method, and the paraquat dichloride content was obtained through the conversion factor.

[0145] Specific test results:

[0146]

[0147] The above results show that the samples prepared using the preparation process provided by this invention have a low content reduction rate, and the best results are obtained by using extrusion centrifugal granulation-vacuum belt drying.

[0148] Experimental Example 3: Validation of Beagle Urine Observation and Tracking Agent

[0149] By directly observing the color of urine, the identifiability of the tracer in the outer coating of this invention can be verified, ensuring rapid traceability in case of accidental ingestion.

[0150] Test materials

[0151] Experimental animals: 6 healthy beagle dogs (10-12kg, half male and half female), acclimatized to cages for 1 week in advance; Experimental samples: Paraquat granules from Example 1 (containing potassium p-nitrobenzoate) and Example 9 (containing sodium 2,4-dinitrophenolate), directly ground into fine powder;

[0152] Control sample: Paraquat granules from Comparative Example 1, ground using the same method;

[0153] Tools: Disposable urine cup, white enamel plate (for easy observation of color).

[0154] Test methods

[0155] Grouping: 6 dogs divided into 3 groups (2 dogs in each group);

[0156] Dosage: Administer 2g of granules / powder per dog per group (below the acute oral LD50 for dogs). 50 Take it with a small amount of warm water afterward.

[0157] Observation: After administration, urine was collected, poured into a white enamel dish, and the color change was observed and recorded directly; Observation duration: Observation continued for 24 hours after administration.

[0158] Experimental results:

[0159] in conclusion:

[0160] The tracking agents in Examples 1 and 9 can cause beagle urine to exhibit distinct characteristic colors (orange-red due to potassium p-nitrobenzoate and bright yellow due to sodium 2,4-dinitrophenol) within 24 hours, allowing for direct observation and identification without instruments, fully meeting the safety protection requirements for rapid traceability after accidental ingestion.

[0161] The inventors would like to specifically point out that, based on the duration of abnormal canine behavior, the paraquat granules of this invention may have even stronger biological activity.

Claims

1. A paraquat granule, characterized in that, It consists of the following components: a) Paraquat salt 45–65 wt%; b) Layered double hydroxide carrier 10–25 wt%; c) Disintegrant 2–8 wt%; d) Microcrystalline cellulose 2–5 wt%; e) The outer multifunctional coating layer contains: emetic, odorant, and tracer, accounting for 1-5 wt%; f) The remainder consists of water-soluble fillers and additives.

2. The paraquat granules according to claim 1, characterized in that, The paraquat salt mentioned is one or more of paraquat dichloride, paraquat dibromide, paraquat dimethylsulfonate, and paraquat disulfate.

3. The paraquat granules according to claim 1, characterized in that, The layered double hydroxide carrier is lactate or citrate intercalated hydrotalcite, chloride intercalated hydrotalcite, nitrate intercalated hydrotalcite, phosphate intercalated hydrotalcite, or sulfonate intercalated hydrotalcite.

4. The paraquat granules according to claim 1, characterized in that, The disintegrants are sodium carboxymethyl starch, croscarmellose sodium, croscarmellose polyvinylpyrrolidone, and low-substituted hydroxypropyl cellulose.

5. The paraquat granules according to claim 1, characterized in that, The microcrystalline cellulose has a specific surface area of ​​0.8-1.3 m² / g, an average particle size of 45-90 μm, and a moisture content of ≤7 wt%.

6. The paraquat granules according to claim 1, characterized in that, The emetic agents in the multifunctional coating layer are aminopropyltriazolylpyrimidinone and 2-methyl-5-hydroxytryptamine; The malodorous agents are 2-methyl-2-propen-1-thiol, cyclohexanethiol, tert-butylthiol, dimethyl sulfide, dipropylene disulfide, isovaleric acid, hexanoic acid, 2-methylpyridine, and 3-ethylpyridine. The tracking agents are potassium p-nitrobenzoate, sodium o-nitrobenzoate, sodium 2,4-dinitrophenolate, and sodium fluorescein.

7. The paraquat granules according to claim 1, characterized in that, The water-soluble filler and additives are one or more of the following: ammonium sulfate, sodium sulfate, sodium chloride, sodium bicarbonate, mannitol, sorbitol, sucrose, sodium citrate, and sodium acetate.

8. The paraquat granules according to claim 1, characterized in that, The water-soluble filler and additives account for 0–60% of the coating layer.

9. The method for preparing paraquat granules according to any one of claims 1-7, characterized in that, Includes the following steps: a. Mix the paraquat salt mother liquor with the layered double hydroxide carrier, disintegrant, microcrystalline cellulose and water-soluble filler (for the inner layer), and granulate by screw extruder to obtain wet granules; b. Mix the emetic, odorant, tracking agent, and water-soluble filler in the outer multifunctional coating for later use; c. The wet granules prepared in step a were used as the core and fed into a centrifugal granulator. Deionized water was sprayed in while dry powder was sprinkled into the outer multifunctional coating mixture prepared in step b, and wet granules of paraquat granules were obtained. d. Feed the wet granules of paraquat into a vacuum belt dryer, control the vacuum degree to -0.07 MPa to -0.09 MPa, the drying temperature to 30–40℃, and the conveyor belt speed to 0.1–0.5 m / min, and dehydrate until the granules contain ≤2 wt% water to obtain paraquat granules. Furthermore, the resulting granules exhibit a wear rate of ≤2%, disintegration of ≤60s, and suspension rate of ≥90%.

10. The method for preparing paraquat granules according to any one of claims 1-7, characterized in that, Includes the following steps: a. Mix the paraquat salt mother liquor with layered double hydroxide carrier, disintegrant, microcrystalline cellulose and water-soluble filler (for inner layer), feed it into a fluidized bed, and spray deionized water to obtain pellet core a (air inlet volume 3-20 m³ / h, air inlet temperature 45-75℃, spraying speed 5-15 Hz, spraying atomization pressure 0.1-0.5 MPa). b. Dissolve the emetic, odorant, tracing agent, and water-soluble filler (for the outer layer) in deionized water to prepare a solution with a mass concentration of 5-15%; c. Connect solution b to a fluidized bed, and simultaneously dry the pellet core a while spraying solution b into it to obtain paraquat granules. Furthermore, the resulting granules exhibit a wear rate of ≤2%, disintegration of ≤60s, and suspension rate of ≥90%.

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