Flonicamid suspension and a preparation method thereof

Abstract

The present application relates to the technical field of pesticide preparation, and specifically discloses a flonicamid suspension concentrate and a preparation method thereof.The flonicamid suspension concentrate comprises the following components in percentage by mass: 5-15% of flonicamid, 3% of wetting agent, 3-9% of dispersant, 0.8-1.2% of thickening agent, 4-8% of antifreezing agent, 0.05-0.15% of preservative, and the rest is deionized water to make up 100%.The present application is aimed at the inherent defects of flonicamid, such as high water solubility, easy precipitation of crystals under temperature change conditions, and deterioration of physical stability of the suspension concentrate, and the synergistic cooperation between the components in the formula system, such as specific compounding of acrylic copolymer dispersant PD3315 and styrene polymer dispersant SP-SC3288, significantly inhibits the particle size growth of the raw material particles during normal temperature storage, high-temperature heat storage and low-temperature cold storage, prolongs the shelf life of the product, and has extremely high industrial application value.

Description

Technical Field

[0001] This invention relates to the technical field of pesticide formulations, and specifically discloses a flonicamid suspension concentrate and its preparation method. Background Technology

[0002] Flunicamid is a pyridine amide insecticide developed by Ishihara Sangyo Co., Ltd. of Japan. It belongs to the class of nicotinamide enzyme inhibitors in the insect nervous system and is classified as a Category 29 selective feeding repellent by the International Resistant Pesticides Action Committee (IRAC). This agent possesses excellent feeding repellent activity and neurotoxicity, effectively inhibiting the feeding behavior of more than 20 species of piercing-sucking pests, including aphids, planthoppers, whiteflies, leafhoppers, and thrips. It is widely used on nearly 100 crops, including fruit trees, grains, potatoes, and rice. Flunicamid has advantages such as strong systemic conductivity, good penetration, resistance to rain washout, and a long residual effect (up to 15 days or more). It is also low in toxicity to bees, environmentally friendly, and shows no cross-resistance with organophosphates, carbamates, pyrethroids, and neonicotinoids, thus possessing significant application value in integrated pest management.

[0003] Suspension concentrates are among the most widely used water-based formulations of pesticides, offering advantages such as good dispersibility, ease of use, and low environmental pollution. However, suspension concentrates are thermodynamically unstable systems, prone to maturation and particle agglomeration during storage, leading to problems such as particle size increase, sedimentation and stratification, and even bottom formation, severely impacting product shelf life and efficacy. This is particularly true for flonicamid, whose relatively high water solubility presents a greater challenge to stability control during suspension processing and storage. Specifically, under varying storage temperatures (e.g., cooling to room temperature after 14 days of heat storage at 54±2℃ as specified in enterprise standards), some active ingredient crystals precipitate due to decreased solubility as the temperature drops, leading to crystal growth, significantly increased particle size, and formulation stratification—a series of physical stability issues. Currently, there are no reports on effective solutions to the problems of active ingredient crystallization and particle size instability caused by temperature changes in flonicamid suspension concentrates; therefore, there is an urgent need to develop a flonicamid suspension concentrate formulation system with excellent long-term stability. Summary of the Invention

[0004] Currently, some patent documents disclose aqueous suspension formulations of flonicamid. For example, CN102696582A discloses an aqueous suspension of flonicamid, which is milled to a particle size ≤5μm using a sand mill. CN117694348A discloses a nano-aqueous suspension of flonicamid and its preparation method, with a particle size reaching D98 of 600-900nm. However, the above-mentioned prior art focuses on improving the pest control efficacy of flonicamid suspensions, and does not address how to improve the physical stability of flonicamid suspensions during processing and storage, especially the stability problems such as the high water solubility of flonicamid and its tendency to crystallize under temperature changes, leading to particle size growth and stratification.

[0005] Commercially available flonicamid suspension concentrates and existing technical literature have not recognized the crucial impact of storage stability on efficacy in practical applications. In fact, if the active ingredient crystallizes and significantly enlarges in particle size during storage, it directly leads to several deteriorations in efficacy: Firstly, the large and irregularly shaped crystals reduce the uniformity and coverage density of the pesticide on the target crop surface, resulting in insufficient effective deposition per unit area of ​​leaves; secondly, the coarsened active ingredient particles are difficult for the plant epidermis to absorb effectively. Flunicillin relies on systemic conductivity for its long-lasting insecticidal effect; increased particle size significantly reduces its ability to penetrate the cuticle and cell wall, leading to reduced systemic conductivity, a drastically shortened duration of action, and ultimately, actual field efficacy far below theoretical expectations. Furthermore, sedimentation, stratification, and crusting during storage can lead to uneven pesticide concentrations during application. Excessive local dosage can cause phytotoxicity, while insufficient dosage results in inadequate efficacy. This not only increases the frequency and cost of application but also risks accelerating the development of pesticide resistance in pests due to overdose exposure, negatively impacting the long-term sustainable application of flonicamid. Current technologies have not offered an effective solution. Therefore, addressing the storage stability issue of flonicamid suspension concentrates is not only a matter of improving formulation processing technology but also a crucial prerequisite for ensuring its effectiveness in field applications and extending its product lifespan. To address the problem of poor storage stability in existing flonicamid suspension products, this invention provides a flonicamid suspension and its preparation method.

[0006] On one hand, this invention discloses a flonicamid suspension concentrate, which adopts the following technical solution: A flonicamid suspension concentrate, by mass percentage, comprises the following components: flonicamid 5-15%, wetting agent 3%, dispersant 3-9%, thickener 0.8-1.2%, antifreeze agent 4-8%, preservative 0.05-0.15%, with the remainder being deionized water to make up 100%.

[0007] In some embodiments, the dispersant is selected from one or more of acrylic copolymer dispersants, carboxylate polymer dispersants, benzenesulfonate dispersants, or styrene polymer dispersants; the acrylic copolymer dispersant is selected from one or more of PD3315, N-600, SUNPOL-GR13A, or ATLOX 4917-LQ-(MV); the carboxylate polymer dispersant is selected from one or more of GERPON K30D, D1500, or SP-SC3288; the benzenesulfonate dispersant is selected from one or more of TXC or PHENYLSULFONAT CAL; and the styrene polymer dispersant is selected from one or more of DA675, TRSA, or CY-8.

[0008] Preferably, the dispersant is PD3315 and SP-SC3288; or, the dispersant is PD3315 and SP-SC3288, and one or more of N-600, SUNPOL-GR13A, ATLOX 4917-LQ-(MV), GERPON K30D, D1500, TXC, PHENYLSULFONAT CAL, DA675 or TRSA, CY-8.

[0009] Specifically, the dispersant is PD3315, SP-SC3288, and CY-8; or, the dispersant is PD3315, SP-SC3288, and ATLOX 4917-LQ-(MV); or, the dispersant is PD3315, SP-SC3288, and DA675; or, the dispersant is PD3315, SP-SC3288, and TXC; or, the dispersant is PD3315, SP-SC3288, and PHENYLSULFONAT CAL.

[0010] In some embodiments, the wetting agent is selected from one or more of the following: phosphate ester wetting agent DS505, isooctanol alkoxylate EH-6, and block polyether wetting agent AILASG-5000-S0-(AP).

[0011] In some embodiments, the thickener is selected from one or more of FG or xanthan gum.

[0012] In some embodiments, the antifreeze is selected from one or more of ethylene glycol, propylene glycol, or glycerol.

[0013] In some embodiments, the preservative is selected from one or more of sodium benzoate or BIT.

[0014] On the other hand, this invention discloses a method for preparing flonicamid suspension, which adopts the following technical solution: A method for preparing a flonicamid suspension includes the following steps: S1. Add the dispersant, wetting agent and antifreeze to deionized water in sequence according to the formula design ratio and stir evenly. S2. Add flonicamid and thickener to the above solution and use a homogenizer for shear dispersion; S3. Grind using a sand mill, with the grinding time ending when the material particle size D98≤6μm.

[0015] In some embodiments, taking into account the effect of the pH value of different preservatives on the thickener, when the preservative is sodium benzoate, the preservative is added together with flonicamid and the thickener in step S2; when the preservative is BIT, the preservative is added together with flonicamid and the thickener in step S1.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention addresses the inherent defects of flonicamid, such as its high water solubility and tendency to crystallize under temperature changes, leading to deterioration of the physical stability of the suspension. Through the synergistic effect of the components in the formulation system, it significantly inhibits the particle size growth of the technical grade pesticide during storage at room temperature, high temperature, and low temperature. This effectively overcomes the technical problems of poor stability and easy stratification of existing flonicamid suspension products during storage, ensuring the uniformity of the pesticide solution and systemic conduction efficiency during actual application, thereby ensuring stable field efficacy and extending the shelf life of the product. It has extremely high industrial application value. 2. The present invention uses acrylic copolymer dispersant PD3315 and styrene polymer dispersant SP-SC3288 in a specific compounding process. The two form a dense isolation layer with synergistic adsorption on the surface of flonicamid particles, which effectively prevents particle aggregation and maturation. 3. The present invention preferably combines the rod-shaped magnesium aluminum silicate thickener FG with xanthan gum to construct a three-dimensional network structure with strong spatial support capabilities. The system can still maintain uniformity and stability when the temperature changes, effectively preventing the original drug from precipitating and crystallizing due to changes in solubility. 4. This invention has found that precise control of the amount of wetting agent plays a key role in maintaining the long-term stability of the formulation. The specific amount of 3wt% can achieve saturated adsorption on the surface of the active ingredient particles without interfering with the steric hindrance effect of the dispersant, and the particle size increase is significantly smaller after both normal storage and heat storage. Detailed Implementation

[0017] To make the above-mentioned objectives, features and advantages of the invention more apparent and understandable, the invention will be further described in detail below with reference to specific embodiments.

[0018] The raw materials used in the following examples are all commercially available products, and their specific sources are shown in the table below:

[0019] Examples 1-6: A flonicamid suspension concentrate and its preparation method The formula and dosage are shown in Table 1, and the preparation method is as follows: S1. Add the dispersant, wetting agent, antifreeze and preservative to the deionized water in sequence according to the formula design ratio and stir evenly. Add deionized water to make up the total sample mass 100g. S2. Add flonicamid and thickener to the above solution and use a homogenizer for shear dispersion at a speed of 10000 r / min for 3 min; S3. Grind using a vertical sand mill until the particle size D98 ≤ 6μm.

[0020] Table 1 Formulations and dosages for Examples 1-6

[0021] Particle size was measured for Examples 1-6 under four scenarios: initial, normal storage, hot storage, and cold storage. The D98 value was measured using a Bettersize 2600 laser particle size analyzer for all scenarios. Normal storage conditions were room temperature in a cool, shaded place. Hot storage conditions involved placing the particles in a DHP-9162 electric thermostatic incubator at 54±2℃ for 14 days, then removing them and allowing them to cool to room temperature. Cold storage conditions involved placing the particles in a HYC-340S medical refrigerator at 0±1℃ for 7 days, then removing them and allowing them to return to room temperature. The test results for Examples 1-6 are shown in Table 2.

[0022] Table 2. Particle size detection results of Examples 1-6

[0023] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that the thickener FG was replaced with an equal amount of SFO4. The preparation method of this comparative example is the same as that of the example.

[0024] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that the dispersants used are PD3315 and ATLOX 4917-LQ-(MV), and SP-SC3288 is not used. The preparation method of this comparative example is the same as that of the examples.

[0025] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that the dispersants used in Comparative Example 3 are SP-SC3288 and ATLOX 4917-LQ-(MV), and PD3315 is not used. The preparation method of this comparative example is the same as that of the example.

[0026] Comparative Example 4 The difference between Comparative Example 4 and Example 3 is that the dispersant used is ATLOX 4917-LQ-(MV), and SP-SC3288 and PD3315 are not used. The preparation method of this comparative example is the same as that of the examples.

[0027] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that an equal amount of GERPON K30D was used instead of dispersant SP-SC3288. The preparation method of this comparative example is the same as that of the examples.

[0028] Comparative Example 6 The difference between Comparative Example 6 and Example 3 is that an equal amount of N-600 was used instead of dispersant PD3315. The preparation method of this comparative example is the same as that of the examples.

[0029] Comparative Example 7 The difference between Comparative Example 7 and Example 5 is that the amount of wetting agent DS505 is reduced to 2g. The preparation method of this comparative example is the same as that of the examples.

[0030] Comparative Example 8 The difference between Comparative Example 8 and Example 5 is that the amount of wetting agent DS505 is increased to 4g. The preparation method of this comparative example is the same as that of the examples.

[0031] The formulations and dosages of Comparative Examples 1-8 are shown in Table 3.

[0032] Table 3. Formulations and dosages of Comparative Examples 1-8

[0033] Particle size was measured for Comparative Examples 1-8, including four scenarios: initial, normal storage, hot storage, and cold storage. The measurement method was the same as described above. The measurement results for Comparative Examples 1-8 are shown in Table 4.

[0034] Table 4. Particle size detection results of Comparative Examples 1-8

[0035] Results analysis: (1) Comparing Comparative Example 1 and Example 2, the thickener FG was replaced with an equal amount of SF04 in Example 2. The results showed that the particle size of the collected samples after grinding could reach D98 ≤ 6 micrometers in both Comparative Example 1 and Example 2. During normal storage, the D98 particle size of Example 2 was more stable than that of Comparative Example 1. The D98 particle size of Comparative Example 1 increased by more than 0.6 micrometers from the initial particle size during normal storage. After being heated at 54℃ for 14 days and then transferred to room temperature, the particle size of Example 2 increased by 2.226 micrometers and then stabilized. The D98 particle size of Comparative Example 1 increased by 3.419 micrometers after being heated to room temperature. It can be seen that although SF04 and FG are both magnesium aluminum silicate thickeners, FG has a rod-shaped structure and stronger spatial support, which makes the suspending agent more stable under different temperature conditions.

[0036] (2) Comparing Comparative Examples 2, 3, and 4 with Example 3, it was found that PD3315 and SP-SC3288 have a synergistic effect on controlling particle size D98. The sum of the improvement in the effect of Comparative Example 4 compared with Comparative Example 2 and Comparative Example 3 alone is far less than the improvement in the effect of Comparative Example 4 compared with Example 3. That is, neither PD3315 nor SP-SC3288 alone can achieve good particle size control effect, while the simultaneous use of PD3315 and SP-SC328 shows excellent particle size stability under normal storage, hot storage, and cold storage. In addition, the study found that this synergistic effect cannot be achieved by simply combining any acrylic copolymer dispersant with a carboxylate polymer dispersant. Compared with Example 3, Comparative Examples 5 and 6, although using different types of dispersants of the same class, failed to achieve the excellent effect of Example 3. This further proves that the special combination synergistic effect of PD3315 and SP-SC3288 may be that the two adjuvants bind more tightly to the drug after synergy, and the drug particles form a tight isolation layer, making it difficult to aggregate, thus maintaining good stability.

[0037] (3) Comparing Comparative Examples 7 and 8 with Example 5, the amount of wetting agent DS505 was reduced to 2 wt% and increased to 4 wt% respectively, based on Example 5, to investigate the effect of the amount of wetting agent deviating from the optimal range on the stability of the formulation. The results showed that the particle size of Comparative Example 7 (2 wt%) increased significantly after both normal and hot storage; the particle size of Comparative Example 8 (4 wt%) also increased after hot storage, which was better than Comparative Example 7, but still significantly worse than Example 5. The above results indicate that there is an optimal range (3 wt%) for the dosage of wetting agent DS505. When the dosage is too low, the phosphate groups (hydrophilic portion) and alkyl chains (hydrophobic portion) cannot saturate the adsorption of the active ingredient and excipient, failing to form a dense polymer barrier layer. Consequently, the active ingredient particles cannot maintain an effective safe distance when approaching each other due to Brownian motion, leading to aggregation and increased particle size. Conversely, when the dosage is too high, excessive wetting agent molecules may form multilayer adsorption on the particle surface or compete with the dispersant for adsorption, disrupting the dense adsorption layer structure synergistically formed by PD3315 and SP-SC3288, thus weakening the stabilizing effect of the dispersant. Therefore, the addition of wetting agent DS505 is not necessarily better the more the better. The specific dosage of 3 wt% precisely achieves saturated adsorption on the surface of the active ingredient particles without interfering with the steric hindrance effect of the dispersant, making it one of the key factors in maintaining the long-term particle size stability of the formulation.

[0038] The technical solution provided by the invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the invention. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A flonicamid suspension concentrate, characterized in that, By mass percentage, it includes the following components: 5-15% flonicamid, 3% wetting agent, 3-9% dispersant, 0.8-1.2% thickener, 4-8% antifreeze, 0.05-0.15% preservative, with the remainder being deionized water to make up 100%.

2. The flonicamid suspension concentrate according to claim 1, characterized in that, The dispersant is selected from one or more of acrylic copolymer dispersants, carboxylate polymer dispersants, benzenesulfonate dispersants, or styrene polymer dispersants; The acrylic copolymer dispersant is selected from one or more of PD3315, N-600, SUNPOL-GR13A or ATLOX 4917-LQ-(MV); the carboxylate polymer dispersant is selected from one or more of GERPON K30D, D1500 or SP-SC3288; the benzenesulfonate dispersant is selected from one or more of TXC or PHENYLSULFONAT CAL; and the styrene polymer dispersant is selected from one or more of DA675, TRSA or CY-8.

3. The flonicamid suspension concentrate according to claim 2, characterized in that, The dispersant is PD3315 and SP-SC3288; or, the dispersant is PD3315 and SP-SC3288, and one or more of N-600, SUNPOL-GR13A, ATLOX 4917-LQ-(MV), GERPON K30D, D1500, TXC, PHENYLSULFONAT CAL, DA675, TRSA or CY-8.

4. The flonicamid suspension concentrate according to claim 3, characterized in that, The dispersant is PD3315, SP-SC3288 and CY-8; or, the dispersant is PD3315, SP-SC3288 and ATLOX 4917-LQ-(MV); or, the dispersant is PD3315, SP-SC3288 and DA675; or, the dispersant is PD3315, SP-SC3288 and TXC; or, the dispersant is PD3315, SP-SC3288 and PHENYLSULFONAT CAL.

5. The flonicamid suspension concentrate according to claim 1, characterized in that, The wetting agent is selected from one or more of the following: phosphate ester wetting agent DS505, isooctanol alkoxylate EH-6, or block polyether wetting agent AILASG-5000-S0-(AP).

6. The flonicamid suspension concentrate according to claim 1, characterized in that, The thickener is selected from one or more of FG or xanthan gum.

7. The flonicamid suspension concentrate according to claim 1, characterized in that, The antifreeze is selected from one or more of ethylene glycol, propylene glycol, or glycerol.

8. The flonicamid suspension concentrate according to claim 1, characterized in that, The preservative is selected from one or more of sodium benzoate and BIT.

9. A method for preparing a flonicamid suspension concentrate according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Add the dispersant, wetting agent and antifreeze to deionized water in sequence according to the formula design ratio and stir evenly. S2. Add flonicamid and thickener to the above solution and use a homogenizer for shear dispersion; S3. Grind using a sand mill, with the grinding time ending when the material particle size D98≤6μm.

10. The method for preparing flonicamid suspension according to claim 9, characterized in that, When the preservative is sodium benzoate, it is added together with flonicamid and thickener in step S2; when the preservative is BIT, it is added together with flonicamid and thickener in step S1.

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