A thiamethoxam complex insecticide and a preparation method thereof

Abstract

This application belongs to the field of insecticide technology, specifically providing a thiamethoxam compound insecticide and its preparation method. The preparation method of a thiamethoxam compound insecticide includes the following steps: cyclodextrin and water are mixed evenly, then an active ingredient and urea are added for inclusion. After inclusion, the mixture is spray-dried. The resulting cyclodextrin inclusion body is mixed with a starch coating solution, followed by the addition of glucomannan and a water-soluble metal salt. The mixture is stirred for a period of time and then dried to obtain the compound insecticide. The starch coating solution in this application is made from oxidized starch and water. The active ingredient used in this application includes thiamethoxam. The thiamethoxam compound insecticide prepared in this application has sustained-release properties, and the active ingredient can be released more completely, maintaining a high release rate of the active ingredient even in the later stages of sustained release.

Description

Technical Field

[0001] This application belongs to the field of insecticide technology, and in particular relates to a thiamethoxam compound insecticide and its preparation method. Background Technology

[0002] Thiamethoxam, as a second-generation neonicotinoid insecticide, occupies an important position in agricultural pest control due to its unique mechanism of action and excellent insecticidal performance. Its mechanism of action involves disrupting the nerve signal transmission of insects, ultimately leading to paralysis and death. It exhibits high selectivity, low toxicity to humans and animals, and no cross-resistance with first-generation neonicotinoid insecticides. It can effectively control a variety of piercing-sucking pests, while also having the auxiliary effects of activating crop stress resistance and promoting root growth. It has been widely used in pest control for various crops.

[0003] Traditional thiamethoxam formulations suffer from short duration of action and low utilization rate of active ingredients. Therefore, the research and application of sustained-release technology for thiamethoxam insecticides is of great significance. Sustained-release technology enables the slow and stable release of the active ingredient in thiamethoxam, prolonging the pesticide's duration of action, reducing the number of applications, lowering agricultural production costs and labor intensity, and minimizing pesticide runoff, resulting in excellent pest control. This represents an important direction for pesticide upgrading.

[0004] Currently, various slow-release materials and preparation processes are being applied in the research of thiamethoxam sustained-release formulations. However, some technical problems still exist, among which the slow release rate and incomplete release in the later stages of sustained release are urgent issues to be addressed. Existing sustained-release formulations can achieve reasonable release of the active ingredient in the early stages of release, meeting the initial pest control needs. However, in the later stages of sustained release, the release rate of the active ingredient decreases significantly due to factors such as the structure of the sustained-release material and the preparation process, making it difficult to maintain a suitable effective concentration. This makes it difficult to cope with the later occurrence of pests, resulting in a decline in control efficacy and limiting the widespread application of thiamethoxam sustained-release formulations. Therefore, optimizing the sustained-release performance of thiamethoxam insecticides has become a key breakthrough in the current research and development of thiamethoxam insecticides. Summary of the Invention

[0005] To address the aforementioned issues and further improve the sustained-release performance of thiamethoxam insecticides, this application provides a thiamethoxam compound insecticide and its preparation method.

[0006] This application first provides a method for preparing a thiamethoxam compound insecticide, comprising the following steps: after mixing cyclodextrin with water evenly, adding active ingredients and urea for inclusion, spray drying after inclusion, mixing the obtained cyclodextrin inclusion body with starch coating liquid, then adding glucomannan and water-soluble metal salt, stirring for a period of time, and drying to obtain the compound insecticide. The starch-encapsulating liquid is made from oxidized starch and water; The active ingredients include thiamethoxam and thiamethoxam.

[0007] Furthermore, the preparation method of the starch coating liquid includes the following steps: mixing glucomannan, oxidized starch, and water, and then heating and stirring.

[0008] Furthermore, the preparation of the oxidized starch includes the following steps: amylopectin is first mixed with deionized water, the pH is adjusted with alkali solution, and then sodium hypochlorite solution is added to carry out the oxidation reaction. After the reaction is completed, hydrochloric acid is added dropwise to adjust the pH. After filtration, washing, and drying, oxidized starch is obtained.

[0009] Furthermore, the molar ratio of the cyclodextrin, the active ingredient, and urea is 1:(0.75-0.82):(0.18-0.25).

[0010] Furthermore, the inlet air temperature of the spray dryer is 170-180℃, and the injection flow rate is 6-8 mL / min.

[0011] Furthermore, the water-soluble metal salt is a water-soluble zinc salt.

[0012] Furthermore, the temperature for heating and stirring is 90-95℃.

[0013] Furthermore, the mass ratio of the amylopectin to the sodium hypochlorite solution is 1:(0.38-0.42).

[0014] Furthermore, the pH of the alkaline solution is adjusted to 8.5-9.5.

[0015] This application also provides a thiamethoxam compound insecticide, prepared using the above-described preparation method.

[0016] Compared with the prior art, this application has the following beneficial effects: 1. A certain amount of carboxyl and hydroxyl groups on the oxidized starch molecular chain can undergo electrostatic adsorption, ionic cross-linking and coordination complexation with metal ions, thereby improving the structural stability, integrity and strength of the starch film system, reducing the loss of effective ingredients during later processing and storage, and reducing the release rate of pesticides.

[0017] 2. The addition of glucomannan is beneficial to the increase of entanglement sites between amylopectin molecular chains. The two interact through hydrogen bonds to form a more stable three-dimensional structure. At the same time, glucomannan can also coordinate and cross-link with metal ions, further increasing the density and stability of the network, so that the insecticide has a good sustained-release effect.

[0018] 3. During the operation of the insecticide, urea is also continuously released and gradually comes into contact with glucomannan and oxidized starch. The amino and carbonyl groups in urea disrupt the hydrogen bonds between glucomannan and oxidized starch. The breaking of hydrogen bonds further reduces the stability of the starch shell during the continuous action of the insecticide, which is conducive to the rapid release of active ingredients such as thiamethoxam in the later stage and ensures a relatively stable concentration of active ingredients. Attached Figure Description

[0019] Figure 1 The results are the active ingredient loading test results of the compound insecticides in Examples 1-3 and Comparative Examples 1-3 of this application.

[0020] Figure 2 The results are the test results of the cumulative release rate of the active ingredients of the compound insecticides in Examples 1-3 and Comparative Examples 1-3 of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] In this application, room temperature refers to 0-40°C, including but not limited to 10-40°C, or further to 20-30°C.

[0024] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0025] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0026] Example 1 The preparation method of the thiamethoxam compound insecticide in this embodiment is as follows: 1) Weigh 11.34g of β-cyclodextrin and add it to deionized water. After stirring continuously for 30min, add 1.53g of thiamethoxam, 0.57g of thiamethoxam and 0.15g of urea. Stir at room temperature for 2h and then spray dry. The inlet air temperature is 170℃ and the injection flow rate is 6mL / min to obtain cyclodextrin inclusion complex. 2) Weigh out 9.8g of amylopectin and mix it with 40g of deionized water. Add 5M sodium hydroxide dropwise to adjust the pH to 8.5. Then adjust the system temperature to 45℃. Add 3.72g of 5% (w / w) sodium hypochlorite solution dropwise while stirring. React for 2 hours. During the reaction, control the pH of the system to maintain at 8.5±0.2. After two hours of reaction, add sodium sulfite to terminate the reaction. Then add hydrochloric acid dropwise to adjust the pH to 6.8. After filtration, wash, dry and pulverize to obtain oxidized starch. 3) Mix 7g of oxidized starch and 260g of deionized water, heat to 90℃ while stirring, continue stirring for 40min, add 18g of cyclodextrin inclusion complex, stir for 10min, then add 0.35g of glucomannan, stir for 2min, then add 0.9g of a mixed solution composed of zinc sulfate heptahydrate and deionized water in a mass ratio of 1:8, stop heating and cool to room temperature, continue stirring for 20min, and finally spray dry with an inlet air temperature of 180℃ and an injection rate of 6mL / min to obtain a compound insecticide.

[0027] Example 2 The preparation method of the thiamethoxam compound insecticide in this embodiment is as follows: 1) Weigh 11.35g of β-cyclodextrin and add it to deionized water. After stirring continuously for 30min, add 1.67g of thiamethoxam, 0.62g of thiamethoxam and 0.11g of urea. Stir at room temperature for 2h and then spray dry. The inlet air temperature is 180℃ and the injection flow rate is 8mL / min to obtain cyclodextrin inclusion complex. 2) Weigh 10g of amylopectin and mix it with 40g of deionized water. Add 5M sodium hydroxide dropwise to adjust the pH to 9.5. Then adjust the system temperature to 45℃. Add 4.2g of 5% (w / w) sodium hypochlorite solution dropwise while stirring. React for 2 hours. During the reaction, control the pH of the system to maintain at 9.5±0.2. After two hours of reaction, add sodium sulfite to terminate the reaction. Then add hydrochloric acid dropwise to adjust the pH to 6.8. After filtration, wash, dry and pulverize to obtain oxidized starch. 3) Mix 10g of oxidized starch and 300g of deionized water, heat to 95℃ while stirring, continue stirring for 30min, add 24g of cyclodextrin inclusion complex, stir for 10min, then add 0.5g of glucomannan, stir for 2min, then add 0.98g of a mixed solution composed of zinc sulfate heptahydrate and deionized water in a mass ratio of 1:8, stop heating and cool to room temperature, continue stirring for 20min, and finally spray dry with an inlet air temperature of 180℃ and an injection rate of 6mL / min to obtain a compound insecticide.

[0028] Example 3 The preparation method of the thiamethoxam compound insecticide in this embodiment is as follows: 1) Weigh 11.35g of β-cyclodextrin and add it to deionized water. After stirring continuously for 30min, add 1.63g of thiamethoxam, 0.6g of thiamethoxam and 0.12g of urea. Stir at room temperature for 2h and then spray dry. The inlet air temperature is 178℃ and the injection flow rate is 7mL / min to obtain cyclodextrin inclusion complex. 2) Weigh 10g of amylopectin and mix it with 40g of deionized water. Add 5M sodium hydroxide dropwise to adjust the pH to 9. Then adjust the system temperature to 45℃. Add 4g of 5% (w / w) sodium hypochlorite solution dropwise while stirring. React for 2 hours. During the reaction, control the pH of the system to maintain at 9±0.2. After two hours of reaction, add sodium sulfite to terminate the reaction. Then add hydrochloric acid dropwise to adjust the pH to 6.8. After filtration, wash, dry and pulverize to obtain oxidized starch. 3) Mix 7g of oxidized starch and 250g of deionized water, heat to 92℃ while stirring, continue stirring for 35min, add 19g of cyclodextrin inclusion complex, stir for 10min, then add 0.35g of glucomannan, stir for 2min, then add 0.9g of a mixed solution composed of zinc sulfate heptahydrate and deionized water in a mass ratio of 1:8, stop heating and cool to room temperature, continue stirring for 20min, and finally spray dry with an inlet air temperature of 180℃ and an injection rate of 6mL / min to obtain a compound insecticide.

[0029] Comparative Example 1 The preparation method of the thiamethoxam compound insecticide in this comparative example is as follows: 11.34g of β-cyclodextrin was weighed and added to deionized water. After stirring continuously for 30min, 2.04g of thiamethoxam and 0.76g of thiamethoxam were added. After stirring at room temperature for 2h, spray drying was carried out with an air inlet temperature of 170℃ and an injection flow rate of 6mL / min to obtain the cyclodextrin inclusion complex.

[0030] The remaining steps are the same as in Example 1.

[0031] Comparative Example 2 The preparation method of the thiamethoxam compound insecticide in this comparative example differs from that in Example 1 in that glucomannan was not added during the preparation of the compound insecticide in step 3), while the remaining steps were the same as in Example 1.

[0032] Comparative Example 3 The preparation method of the thiamethoxam compound insecticide in this comparative example differs from that in Example 1 in that no water-soluble metal salt was added during the preparation of the compound insecticide in step 3), while the remaining steps were the same as in Example 1.

[0033] Performance testing 1. Determination of active ingredient loading Measure 30 mL of distilled water and pour it into a beaker. Add 0.1 g of the weighed compound insecticide, stir continuously, heat to 80 °C, stir for 20 min, cool to room temperature, add 10 mL of acetonitrile, centrifuge at 8000 r / min for 10 min, filter, and determine the mass of the active ingredient according to the formula. Calculate the loading of the active ingredient. The results are as follows: Figure 1 As shown.

[0034] 2. Determination of cumulative release rate Weigh 0.1g of the compound insecticide into a 100mL volumetric flask, add distilled water to bring the volume to 100mL, and place the volumetric flask in a 30℃ water bath for constant temperature. Take a 0.5mL sample at regular intervals, adding distilled water to bring the volume to 100mL after each sample. Measure the concentration of the active ingredient in the sample solution and apply the formula... Calculate the cumulative release rate of the active ingredient; where m0 is the total mass of the active ingredient in the compound insecticide, in mg, C i C represents the concentration of the active ingredient in the solution sampled in the i-th time, expressed in mg / mL. n This represents the concentration of the active ingredient in the solution during the nth (current) sampling, in mg / mL, where n is the total number of samplings. The test results are as follows: Figure 2 As shown.

[0035] according to Figure 1 and Figure 2 As can be seen, in the examples, when using starch to encapsulate the cyclodextrin inclusion complex, the addition of glucomannan and zinc salt can produce an insecticide with a higher loading of active ingredient, and from... Figure 2 It can be seen that their addition makes the sustained-release effect of the insecticide more obvious; compared with Comparative Example 1, the introduction of urea in the example makes the release of the active ingredient in the insecticide more complete. In addition, the release rate of the active ingredient in the insecticide of the example is still significantly increased in the later stage of sustained release (10-15h).

[0036] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a thiamethoxam compound insecticide, characterized in that: The process includes the following steps: After mixing cyclodextrin with water evenly, add the active ingredient and urea for inclusion. After the inclusion is completed, spray dry the cyclodextrin inclusion body and mix it with starch coating liquid. Then add glucomannan and water-soluble metal salt, stir for a period of time, and dry to obtain a compound insecticide. The starch-encapsulating liquid is made from oxidized starch and water; The preparation of the oxidized starch includes the following steps: amylopectin is first mixed with deionized water, the pH is adjusted with alkaline solution, and then sodium hypochlorite solution is added to carry out the oxidation reaction. After the reaction is completed, hydrochloric acid is added dropwise to adjust the pH. After filtration, washing and drying, oxidized starch is obtained. The active ingredients include thiamethoxam and thiamethoxam.

2. The method for preparing a thiamethoxam compound insecticide according to claim 1, characterized in that: The preparation method of the starch coating solution includes the following steps: mixing oxidized starch and water, heating and stirring.

3. The preparation method of the thiamethoxam compound insecticide according to claim 1, characterized in that: The molar ratio of the cyclodextrin, active ingredient, and urea is 1:(0.75-0.82):(0.18-0.25).

4. The preparation method of the thiamethoxam compound insecticide according to claim 1, characterized in that: The inlet air temperature for the spray drying is 170-180℃, and the injection flow rate is 6-8 mL / min.

5. The method for preparing a thiamethoxam compound insecticide according to claim 1, characterized in that: The water-soluble metal salt is a water-soluble zinc salt.

6. The method for preparing a thiamethoxam compound insecticide according to claim 2, characterized in that: The temperature for heating and stirring is 90-95℃.

7. The method for preparing a thiamethoxam compound insecticide according to claim 1, characterized in that: The mass ratio of the amylopectin to the sodium hypochlorite solution is 1:(0.38-0.42).

8. The method for preparing a thiamethoxam compound insecticide according to claim 1, characterized in that: The pH of the alkaline solution is adjusted to 8.5-9.

5.

9. A thiamethoxam compound insecticide, characterized in that: It is prepared by any one of the preparation methods described in claims 1-8.

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