A sustained-release thiamethoxam water dispersible granule and preparation method thereof

Abstract

The present invention relates to the technical field of pesticides and insecticides, and more specifically, to a sustained-release thiamethoxam water-dispersible granule and a preparation method thereof. The sustained-release thiamethoxam water-dispersible granule is composed of the following components: a thiamethoxam sustained-release drug carrier, an anti-loss agent, a dispersant, a disintegrant, a wetting agent and a binder. In the present invention, after thiamethoxam is loaded in attapulgite, the attapulgite is modified with a metal polyphenol complex using brown algae polyphenol and a copper ion coordination complex as a capping agent, so that a thiamethoxam sustained-release drug carrier with pH-responsive release capability can be obtained; the anti-loss agent utilizes the synergistic effect of LA-ε-PL copolymer and bentonite to fix the thiamethoxam sustained-release drug carrier on a complex formed by bentonite and LA-ε-PL copolymer, so that the anti-loss property of the water-sustainable thiamethoxam water-dispersible granule and the adhesion on the surface of leaves can be improved, the scouring loss of the water-dispersible granules by rainfall can be reduced, and the utilization rate of thiamethoxam can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticides and insecticides, and more specifically, to a sustained-release thiamethoxam water-dispersible granule and a preparation method thereof. Background Art

[0002] As a highly effective and broad-spectrum neonicotinoid insecticide, thiamethoxam is mainly used to control piercing-sucking mouthparts pests on various crops, such as aphids, thrips, planthoppers, whiteflies, etc. When using thiamethoxam water-dispersible granules, it is only necessary to dissolve the thiamethoxam water-dispersible granules in water and spray them evenly on the leaves of plants. However, most of the current thiamethoxam water-dispersible granules do not have a sustained-release function and anti-loss performance, resulting in thiamethoxam being easily lost with surface runoff, leached with the vertical movement of soil moisture, or washed away by rainwater after spraying thiamethoxam water-dispersible granules, reducing the utilization rate of thiamethoxam and causing the problem of polluting surface or groundwater bodies. Therefore, it is necessary to use sustained-release technology to reasonably adjust the release rate of thiamethoxam, improve the efficacy, prolong the effective period, and reduce the migration of pesticides in the environment, so as to control pesticide pollution from the source.

[0003] When the surface of a plant is attacked by aphids, aphids will secrete saliva during feeding. These saliva contain a variety of enzymes and organic acids, which can easily destroy the normal pH level of the plant surface, causing the pH value of the plant surface to drop, destroying the structure of the plant cell wall, and making the plant cell wall fragile. It is not only easy to increase the susceptibility of plants to pathogens and other pests, but also cause plant cell wall degradation, nutrient absorption disorders, photosynthesis obstruction, metabolic disorders, induction of plant defense response, water balance imbalance and plant hormone imbalance, and many other problems, affecting the normal growth and development of plants. If the thiamethoxam water dispersible granules can judge the degree of aphid attack on the plant surface according to the pH condition of the plant surface while having a slow-release performance, and then regulate the release capacity of thiamethoxam, it can effectively improve the intelligent response insecticidal effect of the thiamethoxam water dispersible granules, thereby further improving the utilization rate of thiamethoxam in the thiamethoxam water dispersible granules.

[0004] Therefore, it is of great significance to develop a sustained-release thiamethoxam water-dispersible granule with pH-responsive release capability and good anti-loss performance. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a sustained-release thiamethoxam water-dispersible granule and a preparation method thereof, which can achieve the purpose of sustained-release of thiamethoxam and has pH-responsive release capability and anti-loss performance, can effectively reduce the random loss of thiamethoxam or scouring by rainwater, and improve the utilization rate of thiamethoxam.

[0006] A sustained-release thiamethoxam water dispersible granule, comprising the following ingredients:

[0007] 15-60 parts by weight of thiamethoxam sustained-release drug carrier, 10-30 parts by weight of anti-loss agent, 1-9 parts by weight of dispersant, 3-20 parts by weight of disintegrant, 0.6-2 parts by weight of wetting agent and 0.2-1 parts by weight of binder;

[0008] The raw materials for preparing the thiamethoxam sustained-release drug carrier include: 6 to 30 parts by weight of thiamethoxam, 10 to 40 parts by weight of attapulgite, 80 to 160 parts by weight of deionized water, 0.3 to 1 part by weight of copper chloride and 0.9 to 2 parts by weight of brown algae polyphenols;

[0009] The anti-loss agent is prepared by mixing LA-ε-PL copolymer and bentonite in a mass ratio of (0.3-0.6):1;

[0010] The raw materials for preparing the LA-ε-PL copolymer include: 6-18 parts by weight of lipoic acid, 100-120 parts by weight of anhydrous ethanol solution, 1-8 parts by weight of an activator and 12-28 parts by weight of ε-polylysine.

[0011] A method for preparing a sustained-release thiamethoxam water dispersible granule comprises the following steps:

[0012] S1: Preparation of thiamethoxam sustained-release drug carrier, thiamethoxam, attapulgite and deionized water are stirred and mixed, copper chloride and brown algae polyphenols are added, and stirring is continued to obtain a mixed solution, and the mixed solution is centrifuged, the precipitate is collected and vacuum dried to obtain a thiamethoxam sustained-release drug carrier;

[0013] S2: Preparation of an anti-loss agent, dissolving lipoic acid in an anhydrous ethanol solution, adding an activator and stirring to react, obtaining a post-reaction solution, adding ε-polylysine to the post-reaction solution, reacting, centrifuging, washing and drying to obtain a LA-ε-PL copolymer, and uniformly mixing the LA-ε-PL copolymer with bentonite in proportion to obtain an anti-loss agent;

[0014] S3: Preparation of sustained-release thiamethoxam water-dispersible granules, mixing and crushing thiamethoxam sustained-release drug carrier, anti-loss agent, dispersant, disintegrant and wetting agent to obtain mixed powder, mixing the mixed powder with a binder aqueous solution obtained by mixing a binder and water, and then granulating and drying by extrusion to obtain sustained-release thiamethoxam water-dispersible granules.

[0015] As a further technical solution, step S1: preparation of thiamethoxam sustained-release drug carrier specifically comprises the following steps:

[0016] S1.1: 6 to 30 parts by weight of thiamethoxam and 10 to 40 parts by weight of attapulgite are added to 80 to 160 parts by weight of deionized water, and magnetically stirred for 6 to 12 hours. Subsequently, 0.3 to 1 part by weight of copper chloride is added, and magnetically stirred for 20 to 40 minutes. Then, 0.9 to 2 parts by weight of brown algae polyphenols are added, and magnetic stirring is continued for 5 to 10 minutes to obtain a mixed solution.

[0017] S1.2: The pH of the mixed solution is adjusted to 8.2-8.7, and the mixed solution after the pH adjustment is poured into a high-speed centrifuge for centrifugal separation, and the precipitate is taken, and the precipitate is vacuum dried to obtain a thiamethoxam sustained-release drug carrier.

[0018] As a further technical solution, step S2: preparation of an anti-loss agent specifically comprises the following steps:

[0019] S2.1: dissolving 6 to 18 parts by weight of lipoic acid in 100 to 120 parts by weight of anhydrous ethanol solution, then adding 1 to 8 parts by weight of an activator, stirring and reacting at 40 to 48° C. for 20 to 40 minutes to obtain a post-reaction solution;

[0020] S2.2: Add 12 to 28 parts by weight of ε-polylysine to the reaction solution, stir evenly, and react at 36 to 42° C. for 1 to 3 hours. After the reaction, centrifuge, wash and dry to obtain a LA-ε-PL copolymer;

[0021] S2.3: Mix LA-ε-PL copolymer and bentonite in a mass ratio of (0.3-0.6):1 and stir to obtain an anti-loss agent.

[0022] As a further technical solution, the activator is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

[0023] As a further technical solution, step S3: preparation of sustained-release thiamethoxam water dispersible granules specifically comprises the following steps:

[0024] S3.1: 15-60 parts by weight of thiamethoxam sustained-release drug carrier, 10-30 parts by weight of anti-loss agent, 1-9 parts by weight of dispersant, 3-20 parts by weight of disintegrant, and 0.6-2 parts by weight of wetting agent are mixed and air-flow-pulverized to obtain a mixed powder;

[0025] S3.2: 0.2 to 1 parts by weight of a binder and 60 to 100 parts by weight of water are uniformly stirred to obtain a binder aqueous solution;

[0026] S3.3: The mixed powder obtained in step S3.1 and the binder aqueous solution obtained in step S3.2 are stirred and mixed, and after mixing, granulated by extrusion and dried to obtain sustained-release thiamethoxam water-dispersible granules.

[0027] As a further technical solution, the dispersant is at least one of calcium lignin sulfonate, sodium lignin sulfonate, polyoxyethylene oxypropylene, sodium polyacrylate, and sodium tripolyphosphate.

[0028] As a further technical solution, the disintegrant is at least one of ammonium sulfate, sodium sulfate, sodium chloride, urea, microcrystalline cellulose, and sodium carboxymethyl starch.

[0029] As a further technical solution, the wetting agent is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium laurate, tea saponin, and polyethylene glycol.

[0030] As a further technical solution, the binder is at least one of sucrose, dextrin, xanthan gum, and carboxymethyl cellulose.

[0031] Due to the adoption of the above technical solution, the present invention has at least the following beneficial effects compared with the prior art:

[0032] 1. In the present invention, attapulgite is used as a drug-carrying raw material, thiamethoxam is adsorbed on the surface and pore structure of attapulgite, and brown algae polyphenol and copper ion coordination complex are used as capping agents. The phenolic hydroxyl groups in brown algae polyphenol can form coordination bonds with copper ions to generate stable chelates. The attapulgite is modified with a metal polyphenol complex to prepare a thiamethoxam sustained-release drug carrier with pH-responsive release capability. Under neutral and alkaline conditions, the copper in the thiamethoxam sustained-release drug carrier exists in the form of a bidentate complex with brown algae polyphenol, which can achieve a long-term slow release of thiamethoxam. Under acidic conditions, the phenolic hydroxyl groups of brown algae polyphenol in the thiamethoxam sustained-release drug carrier will be protonated to form proton hydrogen, and competitive chelation will be formed between the proton hydrogen and the copper ions, resulting in the overall structure of the thiamethoxam sustained-release drug carrier being unstable and gradually disintegrating, thereby accelerating the release of thiamethoxam.

[0033] 2. In the present invention, the carboxyl group of lipoic acid and the amino group of ε-polylysine are subjected to a condensation reaction, so that lipoic acid and ε-polylysine are copolymerized and connected through an amide bond to form a LA-ε-PL copolymer. The lipoic acid in the LA-ε-PL copolymer can form hydrogen bonds with functional groups such as hydroxyl and carboxyl groups on the surface of plant leaves through the sulfhydryl group, thereby enhancing the fixation ability of the copolymer on the leaf surface, thereby significantly improving the anti-loss effect of the pesticide and the retention effect on the leaf surface. The hydrophilicity and surface activity of ε-polylysine in the LA-ε-PL copolymer can assist in regulating the wettability of the water-dispersible granules, improve the spreadability of the water-dispersible granules sprayed on the leaf surface, make the water-dispersible granules more easily adhere to the leaf surface, thereby improving the utilization rate of thiamethoxam.

[0034] 3. In the present invention, the LA-ε-PL copolymer and bentonite are mixed to prepare an anti-loss agent, so that the cations of ε-polylysine in the LA-ε-PL copolymer molecules and the negative charges in the bentonite molecules generate electrostatic interactions and form stable complexes, and then the synergistic effect of the LA-ε-PL copolymer and the bentonite in the anti-loss agent is utilized to fix the thiamethoxam sustained-release drug carrier on the complex formed by the bentonite and the LA-ε-PL copolymer, which can effectively improve the anti-loss property of the sustained-release thiamethoxam water-dispersible granules, improve the adhesion of the sustained-release thiamethoxam water-dispersible granules on the leaf surface, resist the scouring of the sustained-release thiamethoxam water-dispersible granules by rainfall, and improve the utilization rate of thiamethoxam. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The flowchart of the preparation method of the sustained-release thiamethoxam water dispersible granules in the embodiment of the present invention is shown in FIG.

[0036] Figure 2 This is a graph showing the thiamethoxam release results of the sustained-release thiamethoxam water dispersible granules under different pH conditions in Example 1 of the present invention.

[0037] Figure 3 This is a graph showing the thiamethoxam release results of the sustained-release thiamethoxam water dispersible granules under different pH conditions in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing a sustained-release thiamethoxam water dispersible granule, such as Figure 1 As shown, the specific steps include:

[0041] S1: Preparation of thiamethoxam sustained-release drug carriers,

[0042] S1.1: 30 parts by weight of thiamethoxam and 40 parts by weight of attapulgite were added to 160 parts by weight of deionized water, and magnetically stirred for 12 hours. Subsequently, 1 part by weight of copper chloride was added, and magnetically stirred for 40 minutes. Then, 2 parts by weight of brown algae polyphenols were added, and magnetic stirring was continued for 10 minutes to obtain a mixed solution;

[0043] S1.2: adjusting the pH of the mixed solution to 8.5, pouring the pH-adjusted mixed solution into a high-speed centrifuge for centrifugal separation, taking the precipitate, and vacuum drying the precipitate to obtain a thiamethoxam sustained-release drug carrier;

[0044] S2: Preparation of anti-loss agent,

[0045] S2.1: 18 parts by weight of lipoic acid are dissolved in 120 parts by weight of anhydrous ethanol solution, and then 8 parts by weight of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride are added, and the mixture is stirred at 48° C. for 20 minutes to obtain a post-reaction solution;

[0046] S2.2: Add 25 parts by weight of ε-polylysine to the reaction solution, stir evenly, and react at 42° C. for 2 h. After the reaction, centrifuge, wash and dry to obtain a LA-ε-PL copolymer;

[0047] S2.3: mixing LA-ε-PL copolymer and bentonite in a mass ratio of 0.6:1 to obtain an anti-loss agent;

[0048] S3: Preparation of sustained-release thiamethoxam water dispersible granules,

[0049] S3.1: 60 parts by weight of thiamethoxam sustained-release drug carrier, 30 parts by weight of anti-loss agent, 9 parts by weight of calcium lignin sulfonate, 20 parts by weight of sodium carboxymethyl starch and 2 parts by weight of sodium lauryl sulfate are mixed and jet-milled to obtain a mixed powder;

[0050] S3.2: 1 part by weight of carboxymethyl cellulose and 100 parts by weight of water are stirred uniformly to obtain a binder aqueous solution;

[0051] S3.3: The mixed powder obtained in step S3.1 and the binder aqueous solution obtained in step S3.2 are stirred and mixed, and after mixing, granulated by extrusion and dried to obtain sustained-release thiamethoxam water-dispersible granules.

[0052] Example 2

[0053] A method for preparing a sustained-release thiamethoxam water dispersible granule, such as Figure 1 As shown, the specific steps include:

[0054] S1: Preparation of thiamethoxam sustained-release drug carriers,

[0055] S1.1: 30 parts by weight of thiamethoxam and 40 parts by weight of attapulgite were added to 160 parts by weight of deionized water, and magnetically stirred for 6 hours. Subsequently, 1 part by weight of copper chloride was added, and magnetically stirred for 20 minutes. Then, 2 parts by weight of brown algae polyphenols were added, and magnetic stirring was continued for 5 minutes to obtain a mixed solution.

[0056] S1.2: adjusting the pH of the mixed solution to 8.7, pouring the mixed solution after adjusting the pH into a high-speed centrifuge for centrifugal separation, taking the precipitate, and vacuum drying the precipitate to obtain a thiamethoxam sustained-release drug carrier;

[0057] S2: Preparation of anti-loss agent,

[0058] S2.1: dissolving 18 parts by weight of lipoic acid in 120 parts by weight of anhydrous ethanol solution, then adding 8 parts by weight of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, stirring and reacting at 40° C. for 40 minutes to obtain a post-reaction solution;

[0059] S2.2: Add 25 parts by weight of ε-polylysine to the reaction solution, stir evenly, and react at 36°C for 3 hours. After the reaction, centrifuge, wash and dry to obtain LA-ε-PL copolymer;

[0060] S2.3: mixing LA-ε-PL copolymer and bentonite in a mass ratio of 0.6:1 to obtain an anti-loss agent;

[0061] S3: Preparation of sustained-release thiamethoxam water dispersible granules,

[0062] S3.1: 60 parts by weight of thiamethoxam sustained-release drug carrier, 30 parts by weight of anti-loss agent, 9 parts by weight of calcium lignin sulfonate, 20 parts by weight of sodium carboxymethyl starch and 2 parts by weight of sodium lauryl sulfate are mixed and jet-milled to obtain a mixed powder;

[0063] S3.2: 1 part by weight of carboxymethyl cellulose and 100 parts by weight of water are stirred uniformly to obtain a binder aqueous solution;

[0064] S3.3: The mixed powder obtained in step S3.1 and the binder aqueous solution obtained in step S3.2 are stirred and mixed, and after mixing, granulated by extrusion and dried to obtain sustained-release thiamethoxam water-dispersible granules.

[0065] Example 3

[0066] A method for preparing a sustained-release thiamethoxam water dispersible granule, such as Figure 1 As shown, the specific steps include:

[0067] S1: Preparation of thiamethoxam sustained-release drug carriers,

[0068] S1.1: 30 parts by weight of thiamethoxam and 30 parts by weight of attapulgite were added to 100 parts by weight of deionized water, and magnetically stirred for 12 hours. Subsequently, 1 part by weight of copper chloride was added, and magnetically stirred for 40 minutes. Then, 1 part by weight of brown algae polyphenols was added, and magnetic stirring was continued for 10 minutes to obtain a mixed solution.

[0069] S1.2: adjusting the pH of the mixed solution to 8.5, pouring the pH-adjusted mixed solution into a high-speed centrifuge for centrifugal separation, taking the precipitate, and vacuum drying the precipitate to obtain a thiamethoxam sustained-release drug carrier;

[0070] S2: Preparation of anti-loss agent,

[0071] S2.1: 18 parts by weight of lipoic acid are dissolved in 120 parts by weight of anhydrous ethanol solution, and then 8 parts by weight of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride are added, and the mixture is stirred at 48° C. for 20 minutes to obtain a post-reaction solution;

[0072] S2.2: Add 18 parts by weight of ε-polylysine to the reaction solution, stir evenly, and react at 42° C. for 2 h. After the reaction, centrifuge, wash and dry to obtain a LA-ε-PL copolymer;

[0073] S2.3: mixing LA-ε-PL copolymer and bentonite in a mass ratio of 0.3:1 to obtain an anti-loss agent;

[0074] S3: Preparation of sustained-release thiamethoxam water dispersible granules,

[0075] S3.1: 60 parts by weight of thiamethoxam sustained-release drug carrier, 30 parts by weight of anti-loss agent, 9 parts by weight of calcium lignin sulfonate, 20 parts by weight of sodium carboxymethyl starch and 2 parts by weight of sodium lauryl sulfate are mixed and jet-milled to obtain a mixed powder;

[0076] S3.2: 1 part by weight of carboxymethyl cellulose and 100 parts by weight of water are stirred uniformly to obtain a binder aqueous solution;

[0077] S3.3: The mixed powder obtained in step S3.1 and the binder aqueous solution obtained in step S3.2 are stirred and mixed, and after mixing, granulated by extrusion and dried to obtain sustained-release thiamethoxam water-dispersible granules.

[0078] Comparative Example 1

[0079] Compared with Example 1, the difference of Comparative Example 1 is that step S1 is removed, and the thiamethoxam sustained-release drug carrier is prepared by magnetically stirring 30 parts by weight of thiamethoxam, 40 parts by weight of attapulgite and 160 parts by weight of deionized water for 12 hours and then vacuum drying. The other steps remain unchanged to prepare a sustained-release thiamethoxam water dispersible granule, which is recorded as Comparative Example 1.

[0080] Sustained release performance determination

[0081] The thiamethoxam drug loading of the sustained-release thiamethoxam water dispersible granules in Example 1 and Comparative Example 1 was respectively detected by high performance liquid chromatography, and recorded as M0. 3 g of each of the sustained-release thiamethoxam water dispersible granules in Example 1 and Comparative Example 1 was respectively dispersed in 300 mL of phosphate buffer (pH=7.2) as sample solutions. Each sample solution was equally divided into 5 test solutions at a rate of 60 mL / portion. The pH of the test solution of each sample solution was adjusted to 4, 5, 6, 7 and 8, respectively. Subsequently, all the test solutions of each sample solution were mixed. The samples were shaken in a constant temperature shaker at 25°C at a speed of 200 r / min for 48 hours. Different sampling time intervals were set during the shaking period. When the shaking time reached the set sampling time, 2 mL of supernatant was extracted from each test solution of each sample solution as the analysis object. The thiamethoxam content of each analysis object was detected by high performance liquid chromatography, recorded as M1, and the thiamethoxam release rate of each sample solution under different pH conditions and at different times was calculated. The release rate formula is: P (%) = M1 / M0 × 100%. Figure 2 The release rate of thiamethoxam under different pH conditions of the sustained-release thiamethoxam water dispersible granules of Example 1 is shown in FIG. Figure 3 The results are for the release rate of thiamethoxam from the sustained-release thiamethoxam water-dispersible granules of Comparative Example 1 under different pH conditions.

[0082] like Figure 2-3 It can be seen that in an environment of pH 4-6, the release rate of thiamethoxam in the sustained-release thiamethoxam water-dispersible granules of Example 1 is significantly greater than the release rate in an environment of pH 7-8, among which the release rate is most significant under the environmental condition of pH 4, indicating that the metal polyphenol complex modification of attapulgite by brown algae polyphenols and copper ions can make the thiamethoxam sustained-release drug carrier in the sustained-release thiamethoxam water-dispersible granules have pH-responsive release ability, so that the thiamethoxam sustained-release drug carrier in the sustained-release thiamethoxam water-dispersible granules is slowly released under neutral and alkaline environmental conditions, and quickly releases thiamethoxam under acidic conditions.

[0083] Comparative Example 2

[0084] Compared with Example 1, the difference of Comparative Example 2 is that steps S2.1-S2.2 are removed, the LA-ε-PL copolymer in step S2.3 is replaced with lipoic acid, and the other steps remain unchanged to prepare a sustained-release thiamethoxam water dispersible granule, which is recorded as Comparative Example 2.

[0085] Comparative Example 3

[0086] Compared with Example 1, the difference of Comparative Example 3 is that steps S2.1-S2.2 are removed, the LA-ε-PL copolymer in step S2.3 is replaced with ε-polylysine, and the other steps remain unchanged to prepare a sustained-release thiamethoxam water-dispersible granule, which is recorded as Comparative Example 3.

[0087] Comparative Example 4

[0088] Compared with Example 1, the difference of Comparative Example 4 is that step S2 is removed, the anti-loss agent in step S3.1 is replaced by an equal weight portion of bentonite, and the other steps remain unchanged to prepare a sustained-release thiamethoxam water dispersible granule, which is recorded as Comparative Example 4.

[0089] Comparative Example 5

[0090] Compared with Example 1, the difference of Comparative Example 5 is that step S2 is removed, the anti-loss agent in step S3.1 is replaced by an equal weight portion of LA-ε-PL copolymer, and the other steps remain unchanged to prepare a sustained-release thiamethoxam water dispersible granule, which is recorded as Comparative Example 5.

[0091] Leaf contact angle and anti-loss performance determination

[0092] Leaf contact angle: Select fresh cucumber leaves grown indoors, wash the leaf surfaces with deionized water to remove dust on the surface and ensure that the leaf surfaces are not damaged. After the washed leaves are dried at room temperature, they are cut into small leaflets with a side length of 1.5 cm, 7 small leaflets are taken, and the leaf surfaces of the 7 small leaflets are fixed on glass slides respectively. The sustained-release thiamethoxam water-dispersible granules in Examples 1-3 and Comparative Examples 2-5 are respectively formulated into test solutions with a concentration of 2 mg / L, and 2 μL of each test solution is respectively added dropwise to the 7 small leaflets, and then each small leaflet together with the glass slide is sequentially placed on the stage of the contact angle measuring instrument to obtain each droplet image, calculate the corresponding contact angle value, and obtain the contact angle results, as shown in Table 1.

[0093] Anti-loss performance: Select fresh cucumber leaves grown indoors, and wash the leaf surface with deionized water to remove surface dust and ensure that the leaf surface is not damaged. After the washed leaves are dried at room temperature, 7 leaves are taken as test objects, and the sustained-release thiamethoxam water-dispersible granules in Examples 1-3 and Comparative Examples 2-5 are respectively formulated into test solutions with a concentration of 2 mg / L, and each test solution is evenly sprayed on the surface of 7 different leaves with a spray gun, and dried naturally. Each leaf after spraying is divided into two parts along the main vein, one part of which is pressurized with 100 mL of deionized water to simulate rainfall and wash the leaves, and the other part is not washed. After the droplets on the surface of the leaves were dried, the two parts of each leaf were cut into pieces with scissors, and the content of thiamethoxam in the two parts of each leaf was detected by high performance liquid chromatography. The leaf retention rate of thiamethoxam was calculated. The calculation formula of the leaf retention rate was: leaf retention rate (%) = (content of pesticide active ingredients in the leaves without washing - content of pesticide active ingredients in the leaves with washing) / content of pesticide active ingredients in the leaves without washing × 100%. The leaf retention rate results were obtained. The anti-loss performance of each sustained-release thiamethoxam water-dispersible granule was reflected by the leaf retention rate results, as shown in Table 1.

[0094] Table 1:

[0095]

[0096] As shown in Table 1, from the results of the leaf contact angle measurement and the leaf retention rate results, it can be seen that the leaf contact angle of the sustained-release thiamethoxam water-dispersible granules in Examples 1-3 after being sprayed on the surface of cucumber leaves is less than the leaf contact angle results of Comparative Examples 2-5, and the leaf retention rate results are also better than the leaf retention rates of Comparative Examples 2-5, and the leaf retention rate can reach a level of more than 79%. At the same time, the leaf contact angle result value of Comparative Example 4 is the largest, and the liquid surface retention rate result of Comparative Example 5 is also relatively the worst, indicating that the addition of the anti-loss agent and the synergistic effect of the LA-ε-PL copolymer and bentonite can effectively improve the wetting, spreading and anti-loss properties of the sustained-release thiamethoxam water-dispersible granules after spraying, reduce the scouring loss of the sustained-release thiamethoxam water-dispersible granules due to rainfall, and thus improve the utilization rate of thiamethoxam.

[0097] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to allow people familiar with the technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. For ordinary technicians in the field, they can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the claims attached to the present invention. Parts not described in detail in this specification belong to the prior art known to professional and technical personnel in the field.

Claims

1. A sustained-release thiamethoxam water dispersible granule, characterized in that: It is composed of the following ingredients: 15-60 parts by weight of thiamethoxam sustained-release drug carrier, 10-30 parts by weight of anti-loss agent, 1-9 parts by weight of dispersant, 3-20 parts by weight of disintegrant, 0.6-2 parts by weight of wetting agent and 0.2-1 parts by weight of binder; The raw materials for preparing the thiamethoxam sustained-release drug carrier include: 6 to 30 parts by weight of thiamethoxam, 10 to 40 parts by weight of attapulgite, 80 to 160 parts by weight of deionized water, 0.3 to 1 part by weight of copper chloride and 0.9 to 2 parts by weight of brown algae polyphenols; The anti-loss agent is prepared by mixing LA-ε-PL copolymer and bentonite in a mass ratio of (0.3-0.6):1; The raw materials for preparing the LA-ε-PL copolymer include: 6-18 parts by weight of lipoic acid, 100-120 parts by weight of anhydrous ethanol solution, 1-8 parts by weight of an activator and 12-28 parts by weight of ε-polylysine.

2. A method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 1, characterized in that: The steps include: S1: Preparation of thiamethoxam sustained-release drug carrier, thiamethoxam, attapulgite and deionized water are stirred and mixed, copper chloride and brown algae polyphenols are added, and stirring is continued to obtain a mixed solution, and the mixed solution is centrifuged, the precipitate is collected and vacuum dried to obtain a thiamethoxam sustained-release drug carrier; S2: Preparation of an anti-loss agent, dissolving lipoic acid in an anhydrous ethanol solution, adding an activator and stirring to react, obtaining a post-reaction solution, adding ε-polylysine to the post-reaction solution, reacting, centrifuging, washing and drying to obtain a LA-ε-PL copolymer, and uniformly mixing the LA-ε-PL copolymer with bentonite in proportion to obtain an anti-loss agent; S3: Preparation of sustained-release thiamethoxam water-dispersible granules, mixing and crushing thiamethoxam sustained-release drug carrier, anti-loss agent, dispersant, disintegrant and wetting agent to obtain mixed powder, mixing the mixed powder with a binder aqueous solution obtained by mixing a binder and water, and then granulating and drying by extrusion to obtain sustained-release thiamethoxam water-dispersible granules.

3. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 2, characterized in that: Step S1: Preparation of thiamethoxam sustained-release drug carrier, specifically comprising the following steps: S1.1: 6 to 30 parts by weight of thiamethoxam and 10 to 40 parts by weight of attapulgite are added to 80 to 160 parts by weight of deionized water, and magnetically stirred for 6 to 12 hours. Subsequently, 0.3 to 1 part by weight of copper chloride is added, and magnetically stirred for 20 to 40 minutes. Then, 0.9 to 2 parts by weight of brown algae polyphenols are added, and magnetic stirring is continued for 5 to 10 minutes to obtain a mixed solution. S1.2: The pH of the mixed solution is adjusted to 8.2-8.7, and the mixed solution after the pH adjustment is poured into a high-speed centrifuge for centrifugal separation, and the precipitate is taken, and the precipitate is vacuum dried to obtain a thiamethoxam sustained-release drug carrier.

4. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 3, characterized in that: Step S2: Preparation of anti-loss agent, specifically comprising the following steps: S2.1: dissolving 6 to 18 parts by weight of lipoic acid in 100 to 120 parts by weight of anhydrous ethanol solution, then adding 1 to 8 parts by weight of an activator, stirring and reacting at 40 to 48° C. for 20 to 40 minutes to obtain a post-reaction solution; S2.2: Add 12 to 28 parts by weight of ε-polylysine to the reaction solution, stir evenly, and react at 36 to 42° C. for 1 to 3 hours. After the reaction, centrifuge, wash and dry to obtain a LA-ε-PL copolymer; S2.3: Mix LA-ε-PL copolymer and bentonite in a mass ratio of (0.3-0.6):1 and stir to obtain an anti-loss agent.

5. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 4, characterized in that: The activating agent is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

6. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 4, characterized in that: Step S3: Preparation of sustained-release thiamethoxam water dispersible granules, specifically comprising the following steps: S3.1: 15-60 parts by weight of thiamethoxam sustained-release drug carrier, 10-30 parts by weight of anti-loss agent, 1-9 parts by weight of dispersant, 3-20 parts by weight of disintegrant, and 0.6-2 parts by weight of wetting agent are mixed and air-flow-pulverized to obtain a mixed powder; S3.2: 0.2 to 1 parts by weight of a binder and 60 to 100 parts by weight of water are uniformly stirred to obtain a binder aqueous solution; S3.3: The mixed powder obtained in step S3.1 and the binder aqueous solution obtained in step S3.2 are stirred and mixed, and after mixing, granulated by extrusion and dried to obtain sustained-release thiamethoxam water-dispersible granules.

7. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 6, characterized in that: The dispersant is at least one of calcium lignin sulfonate, sodium lignin sulfonate, polyoxyethylene oxypropylene, sodium polyacrylate, and sodium tripolyphosphate.

8. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 7, characterized in that: The disintegrant is at least one of ammonium sulfate, sodium sulfate, sodium chloride, urea, microcrystalline cellulose, and sodium carboxymethyl starch.

9. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 8, characterized in that: The wetting agent is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium laurate, tea saponin and polyethylene glycol.

10. The method for preparing the sustained-release thiamethoxam water dispersible granules according to claim 9, characterized in that: The binder is at least one of sucrose, dextrin, xanthan gum and carboxymethyl cellulose.

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