Pesticide microcapsules based on bio-based raw materials and methods for their preparation

Abstract

The present application relates to the technical field of pesticide microcapsule, and discloses a pesticide microcapsule based on bio-based raw materials and a preparation method thereof.The bio-based castor oil is selected to construct the capsule wall of the pesticide microcapsule, and the capsule shell has flexibility, rigidity and porosity by crosslinking of the castor oil, a modifier, polyvinyl alcohol and isophorone diisocyanate, so that the balance of crosslinking density and drug diffusion channel is achieved, the continuous controllable release is realized, and the problems of short effective period and easy photolysis are solved.The modifier is prepared by introducing a butyl flexible chain and a diphenyl ether structure into the castor oil polyoxyethylene ether.The polyoxyethylene ether improves the wetting performance and enhances the adhesion stability of the capsule shell to the leaf surface and the body surface, so that the effect rate is improved through feeding and body surface contact;the butyl flexible chain increases the flexibility of the capsule shell, which is easy to adhere to the soil surface and not easy to infiltrate;and the rigid structure of the diphenyl ether improves the high temperature resistance and solves the softening problem in the storage process.

Description

Technical Field

[0001] This invention relates to the field of pesticide microcapsule technology, specifically to a pesticide microcapsule based on bio-based raw materials and its preparation method. Background Technology

[0002] In modern agriculture, pesticides are indispensable production materials for ensuring crop yields and controlling pests and diseases. However, traditional pesticide formulations generally suffer from problems such as short effective duration of active ingredients, easy photodegradation, easy erosion by rainwater, and excessive leaching in the soil. This not only leads to low pesticide utilization but also poses a serious threat to non-target organisms and the ecological environment. Therefore, developing intelligent controlled-release formulations that can precisely and on-demand deliver active ingredients has become a current research hotspot. Existing studies have shown that microencapsulation technology can significantly reduce pesticide decomposition and is easy to implement. Among the many microcapsule preparation technologies, interfacial polymerization has attracted much attention due to its relatively simple process, mild reaction conditions, and suitability for continuous production. By selecting appropriate oil-phase and aqueous-phase monomers, capsules with different chemical compositions and microstructures, such as polyurea and polyurethane, can be constructed. However, microcapsules prepared by traditional interfacial polymerization usually pursue continuous, dense, and mechanically strong shells to achieve long-term release, which means that the structure and material of the shell play a decisive role in the overall performance of the microcapsule.

[0003] Against this backdrop, pesticide microcapsule technology offers a feasible system solution by encapsulating active ingredients in tiny vesicles formed from polymer wall materials. By selecting different wall materials and processing techniques, microcapsules with functions such as slow-release / controlled-release, photoprotection, enhanced leaf adhesion, or soil retention regulation can be designed, significantly overcoming the four major defects of traditional formulations and achieving simultaneous reduction in pesticide dosage and increased efficacy while simultaneously reducing environmental risks. Therefore, developing novel controlled-release pesticide formulations based on microcapsule technology has clear application value and urgent market demand. Patent application CN202411612666.2 discloses a pesticide microcapsule and its application, using polylactic acid and polyvinyl alcohol as wall materials, which are biodegradable. Encapsulating the active pesticide ingredients in microcapsules protects the active ingredients from degradation by environmental factors such as light and temperature, providing effective protection, especially against the photosensitivity of piperine. Microcapsules can control the release rate of pesticides, achieving a slow-release effect, extending the duration of efficacy, and reducing the number of applications. However, although polylactic acid can be partially removed through evaporation and drying, the problem of controlling organic solvent residues still exists. Based on this, the present invention provides a biodegradable bio-based pesticide microcapsule, which fundamentally solves the problem of the difficulty in degrading traditional polyurethane wall materials. Summary of the Invention

[0004] The purpose of this invention is to provide a pesticide microcapsule based on bio-based raw materials and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A pesticide microcapsule based on bio-based raw materials, comprising the following raw materials in parts by weight: 44-88 parts polyvinyl alcohol, 0.6-1.2 parts castor oil, 0.4-0.8 parts isophorone diisocyanate, 5-10 parts high-efficiency cypermethrin, and 0.1-0.3 parts modifier.

[0006] Furthermore, the preparation method of the modifier includes the following steps: A1. Add 1.5-2.4g of castor oil polyoxyethylene ether to a reaction vessel, then add 0.08-0.13g of alkaline catalyst and 1.2-2.2g of 4-hydroxybutylacrylate glycidyl ether. Heat to 40-60℃, stir evenly, continue to heat to the target temperature, and continue stirring for 2-5 hours. After the reaction is completed, cool to 60-80℃, then add 0.05g-0.08g of neutralizing agent, stir for 20-30 minutes, then heat to 100-120℃ to remove water, filter, and obtain the modified intermediate. A2. Take 0.9-1.5g of 4,4'-diaminodiphenyl ether and add it to 20ml of N,N-dimethylformamide. Stir until homogeneous to obtain a 4,4'-diaminodiphenyl ether solution. Take 1.3-1.9g of the modified intermediate and add it to 20ml of N,N-dimethylformamide. Stir until homogeneous. Add 0.07-0.1g of catalyst and then add the 4,4'-diaminodiphenyl ether solution dropwise. Heat to 60-80℃ and continue stirring the reaction. After the reaction is complete, extract and wash to obtain the modifier.

[0007] Furthermore, in A1, the castor oil polyoxyethylene ether is designated as castor oil polyoxyethylene ether EL40.

[0008] Furthermore, in A1, the target temperature is 120-140℃.

[0009] Furthermore, in A1, the neutralizing agent is phosphoric acid.

[0010] Furthermore, in A1, the alkaline catalyst is potassium hydroxide.

[0011] Furthermore, in A2, the catalyst is silver tetrafluoroborate or scandium trifluoromethanesulfonate.

[0012] Furthermore, in A2, the stirring reaction time ranges from 10 to 12 hours.

[0013] According to the above scheme, castor oil polyoxyethylene ether and 4-hydroxybutyl acrylate glycidyl ether are used as raw materials. Under alkaline catalyst and heating conditions, the hydroxyl groups of castor oil polyoxyethylene ether and the epoxy groups of 4-hydroxybutyl acrylate glycidyl ether react to graft the alkenyl group into the castor oil polyoxyethylene ether molecular chain, obtaining a modified intermediate. Then, using the modified intermediate and 4,4'-diaminodiphenyl ether as raw materials, under the action of a reaction promoter and heating, the alkenyl group of the modified intermediate and the amino group of 4,4'-diaminodiphenyl ether react to introduce the diphenyl ether structure into the castor oil polyoxyethylene ether molecular chain, obtaining a modifier.

[0014] A method for preparing pesticide microcapsules based on bio-based raw materials includes the following steps: Step 1: Add castor oil, modifier and isophorone diisocyanate to the reactor, heat to 80-90℃, react for 30-40 minutes, then add dibutyltin dilaurate, and continue to react at 80-90℃ for 3-5 hours to obtain the prepolymer. Step 2: Melt the high-efficiency cypermethrin and mix it with the prepolymer to obtain a mixed oil phase; heat the polyvinyl alcohol solution to 50-60℃ and quickly disperse it into the mixed oil phase; use a high-shear homogenizer for initial emulsification; then homogenize under high pressure at 450-550 Bar for 6-8 minutes to form a uniform emulsion. Step 3: Maintain the temperature at 50-60℃ and stir the emulsion at 450-550 rpm for 4-6 hours to carry out the interfacial polymerization reaction. After the reaction is completed, pesticide microcapsules are obtained.

[0015] The beneficial effects of this invention are: (1) The pesticide microcapsules prepared in this invention use biodegradable bio-based raw material castor oil to construct the capsule wall. Through cross-linking between castor oil, modifier, polyvinyl alcohol and isophorone diisocyanate, the capsule shell of the pesticide microcapsule retains a certain degree of flexibility, rigidity and porosity, effectively balancing the cross-linking density, flexibility and drug diffusion channels of the wall material, so that the drug can be released continuously and in a controllable manner, solving the problems of short effective period and easy photodegradation of active ingredients caused by premature large-volume release.

[0016] (2) The modifier is prepared by introducing a butyl flexible chain and a diphenyl ether structure into the castor oil polyoxyethylene ether molecular chain. The castor oil polyoxyethylene ether molecular chain contains castor oil structure, which can be well integrated into the matrix. The ether bond in the polyoxyethylene ether can form hydrogen bonds with water molecules, which can greatly improve the hydrophilicity of the matrix and enhance the wetting performance of the pesticide microcapsule shell. This improves the adhesion stability of the pesticide microcapsules to the leaf surface and insect body. It can be absorbed into the body by pests through ingestion and released by digestive enzymes, and can also promote the penetration of active ingredients through contact with the body surface. The onset rate is greatly improved under the dual action of epidermal contact and gastric enzyme degradation. The introduced butyl flexible chain can improve the flexibility and elasticity of the matrix and increase the flexibility of the shell. When in contact with soil, it can adapt to the uneven and rough surface of the soil. The interfacial adsorption is strong and it is not easy to seep down with water. The surface retention effect is outstanding. The diphenyl ether structure is a rigid group with excellent thermal stability. Introducing it into the wall material of pesticide microcapsules can effectively improve the high temperature resistance of the capsules, thereby improving the phenomenon of softening during storage.

[0017] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The image shows the infrared analysis test result of the modifier in Example 1. Detailed Implementation

[0020] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 A pesticide microcapsule based on bio-based raw materials, comprising the following raw materials in parts by weight: 44 parts polyvinyl alcohol, 0.6 parts castor oil, 0.4 parts isophorone diisocyanate, 5 parts high-efficiency cypermethrin, and 0.1 parts modifier.

[0022] The preparation method of pesticide microcapsules includes the following steps: Step 1: Add castor oil, modifier and isophorone diisocyanate to the reactor, heat to 80°C, react for 30 min, then add dibutyltin dilaurate, and continue to react at 80°C for 3 h to obtain the prepolymer; Step 2: Melt the high-efficiency cypermethrin and mix it with the prepolymer to obtain a mixed oil phase; heat the polyvinyl alcohol solution to 50°C and quickly disperse it into the mixed oil phase; use a high-shear homogenizer for initial emulsification; then homogenize it under high pressure at 450 Bar for 6 minutes to form a uniform emulsion. Step 3: Maintain the temperature at 50℃ and stir the emulsion at 450 rpm for 4 hours to carry out the interfacial polymerization reaction. After the reaction is completed, pesticide microcapsules are obtained.

[0023] The preparation method of the modifier includes the following steps: A1. Add 1.5g of castor oil polyoxyethylene ether EL40 to the reaction vessel, then add 0.08g of potassium hydroxide and 1.2g of 4-hydroxybutyl acrylate glycidyl ether. Heat to 40℃, stir evenly, continue to heat to 120℃, and continue stirring for 2 hours. After the reaction is completed, cool to 60℃, then add 0.05g of phosphoric acid, stir for 20 minutes, and then heat to 120℃ to remove water. Filter to obtain the modified intermediate. A2. Take 0.9 g of 4,4'-diaminodiphenyl ether and add it to 20 ml of N,N-dimethylformamide. Stir well to obtain a 4,4'-diaminodiphenyl ether solution. Take 1.3 g of the modified intermediate and add it to 20 ml of N,N-dimethylformamide. Stir well. Add 0.07 g of silver tetrafluoroborate and then add the 4,4'-diaminodiphenyl ether solution dropwise. Heat to 80℃ and continue stirring for 10 h. After the reaction is complete, extract and wash to obtain the modifier.

[0024] Figure 1 The infrared spectrum of this modifier is shown at 3387 cm⁻¹. -1 The characteristic absorption peak at 1118 cm⁻¹ is attributed to the -OH characteristic peak. -1 The characteristic absorption peak at 3000 cm⁻¹ is attributed to the characteristic peak of ether bonds. -1 The characteristic absorption peak at 1720 cm⁻¹ belongs to the CH characteristic peak of C=C. -1 The characteristic absorption peak at 1591 cm⁻¹ is attributed to the C=O characteristic peak of the ester bond. -1 The characteristic absorption peak at 1194 cm⁻¹ belongs to the characteristic peak of the benzene ring skeleton. -1 The characteristic absorption peak at that location belongs to the CN characteristic peak.

[0025] Example 2 A pesticide microcapsule based on bio-based raw materials, comprising the following raw materials in parts by weight: 50 parts polyvinyl alcohol, 0.8 parts castor oil, 0.5 parts isophorone diisocyanate, 6 parts high-efficiency cypermethrin, and 0.3 parts modifier.

[0026] The preparation method of pesticide microcapsules includes the following steps: Step 1: Add castor oil, modifier and isophorone diisocyanate to the reactor, heat to 85°C, react for 35 min, then add dibutyltin dilaurate, and continue to react at 85°C for 4 h to obtain the prepolymer; Step 2: Melt the high-efficiency cypermethrin and mix it with the prepolymer to obtain a mixed oil phase; heat the polyvinyl alcohol solution to 55°C and quickly disperse it into the mixed oil phase; use a high-shear homogenizer for initial emulsification; then homogenize it under high pressure at 500 Bar for 7 minutes to form a uniform emulsion. Step 3: Maintain the temperature at 55℃ and stir the emulsion at 500 rpm for 5 hours to carry out the interfacial polymerization reaction. After the reaction is completed, pesticide microcapsules are obtained.

[0027] The preparation method of the modifier is the same as that in Example 1.

[0028] Example 3 A pesticide microcapsule based on bio-based raw materials, comprising the following raw materials in parts by weight: 88 parts polyvinyl alcohol, 1.2 parts castor oil, 0.8 parts isophorone diisocyanate, 10 parts high-efficiency cypermethrin, and 0.3 parts modifier.

[0029] The preparation method of pesticide microcapsules includes the following steps: Step 1: Add castor oil, modifier and isophorone diisocyanate to the reactor, heat to 90°C, react for 40 min, then add dibutyltin dilaurate, and continue to react at 90°C for 5 h to obtain the prepolymer; Step 2: Melt the high-efficiency cypermethrin and mix it with the prepolymer to obtain a mixed oil phase; heat the polyvinyl alcohol solution to 60°C and quickly disperse it into the mixed oil phase; use a high-shear homogenizer for initial emulsification; then homogenize under high pressure at 550 Bar for 8 minutes to form a uniform emulsion. Step 3: Maintain the temperature at 60℃ and stir the emulsion at 550 rpm for 6 hours to carry out the interfacial polymerization reaction. After the reaction is completed, pesticide microcapsules are obtained.

[0030] The preparation method of the modifier is the same as that in Example 1.

[0031] Comparative Example 1 A pesticide microcapsule based on bio-based raw materials, comprising the following raw materials in parts by weight: 50 parts polyvinyl alcohol, 0.8 parts castor oil, 0.5 parts isophorone diisocyanate, and 6 parts high-efficiency cypermethrin.

[0032] The preparation method of pesticide microcapsules includes the following steps: Step 1: Add castor oil and isophorone diisocyanate to the reactor, heat to 85°C, react for 35 min, then add dibutyltin dilaurate, and continue to react at 85°C for 4 h to obtain the prepolymer. Step 2: Melt the high-efficiency cypermethrin and mix it with the prepolymer to obtain a mixed oil phase; heat the polyvinyl alcohol solution to 55°C and quickly disperse it into the mixed oil phase; use a high-shear homogenizer for initial emulsification; then homogenize it under high pressure at 500 Bar for 7 minutes to form a uniform emulsion. Step 3: Maintain the temperature at 55℃ and stir the emulsion at 500 rpm for 5 hours to carry out the interfacial polymerization reaction. After the reaction is completed, pesticide microcapsules are obtained.

[0033] The preparation method of the modifier is the same as that in Example 1.

[0034] Performance testing ① Add pesticide microcapsules to a dialysis bag, then add a 60% methanol aqueous solution. Immerse the dialysis bag in a brown reagent bottle containing 390 mL of the 60% methanol aqueous solution. Place the reagent bottle in a constant temperature shaker and shake at 125 rpm at room temperature. Determine the residue of lambda-cyhalothrin at 245 nm using a UV-2700 UV-Vis spectrophotometer and calculate the cumulative release rate (CR) (%).

[0035] Where M t M0 represents the mass of highly efficient cypermethrin released from the pesticide microcapsules at the sampling time point; M0 represents the total mass of highly efficient cypermethrin in the pesticide microcapsules.

[0036] ② The pesticide microcapsules were applied mainly by foliar spraying to kill insects. The effect of controlling soil longitudinal leaching migration was investigated by measuring the concentration of high-efficiency cypermethrin in the soil layer below 5 cm and conducting soil leaching tests.

[0037] ③ After storing the pesticide microcapsules at 54℃ for 14 days, observe their morphological stability and whether they exhibit adhesion and aggregation. Conduct high-temperature resistance tests.

[0038] ④ After the dried pesticide microcapsule powder is pressed into tablets on a tablet press, it is dried for 24 hours. Approximately 2 μL of water is dropped onto the sample surface, and the contact angle is observed to conduct a wetting performance test.

[0039] The results are shown in the table below.

[0040] The release rate data shows that the pesticide microcapsules prepared by this invention have excellent release rates. This is because the cross-linking between castor oil, modifier, polyvinyl alcohol and isophorone diisocyanate allows the capsule shell of the pesticide microcapsule to retain a certain degree of flexibility, rigidity and porosity, effectively balancing the cross-linking density, flexibility and drug diffusion channels of the wall material, so that the drug can be released continuously and in a controllable manner, solving the problems of short effective period and easy photodegradation of active ingredients caused by premature large-volume release.

[0041] Based on the concentration data of high-efficiency cypermethrin in the soil layer below 5cm, combined with Examples 1-3 and Comparative Example 1, it can be seen that the modifier effectively improves the flexibility of pesticide microcapsules. This is because the butyl flexible chain introduced by the modifier can improve the flexibility and elasticity of the matrix, increase the flexibility of the capsule shell, and adapt to the uneven and rough surface of the soil when in contact with the soil. It has strong interfacial adsorption, is not easy to seep into the soil with water, and has a prominent surface retention effect.

[0042] Based on the data on whether adhesion and agglomeration occurred, combined with Examples 1-3 and Comparative Example 1, it can be seen that the modifier effectively improves the high-temperature resistance of pesticide microcapsules. This is because the diphenyl ether structure contained in the modifier is a rigid group with excellent thermal stability. Introducing it into the wall material of pesticide microcapsules can effectively improve the high-temperature resistance of the capsules, thereby improving the phenomenon that they are prone to softening during storage.

[0043] Based on the contact angle data, combined with Examples 1-3 and Comparative Example 1, it can be seen that the modifier effectively improves the wetting performance of pesticide microcapsules. This is because the ether bonds in the polyoxyethylene ether contained in the modifier can form hydrogen bonds with water molecules, which can greatly improve the hydrophilicity of the matrix, enhance the wetting performance of the pesticide microcapsule shell, and better improve the adhesion stability of pesticide microcapsules and leaves to insects. It can not only enter the body of pests through ingestion and release the efficacy through digestive enzyme decomposition, but also promote the penetration of active ingredients through body surface contact. Under the dual action of epidermal contact and gastric enzyme degradation, the onset rate is greatly improved.

[0044] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A pesticide microcapsule based on bio-based raw materials, characterized in that, Including the following parts by weight of raw materials: 44-88 parts polyvinyl alcohol, 0.6-1.2 parts castor oil, 0.4-0.8 parts isophorone diisocyanate, 5-10 parts high-efficiency cypermethrin, and 0.1-0.3 parts modifier.

2. The pesticide microcapsule based on bio-based raw materials according to claim 1, characterized in that, The preparation method of the modifier includes the following steps: A1. Add castor oil polyoxyethylene ether to a reaction vessel, then add an alkaline catalyst and 4-hydroxybutyl acrylate glycidyl ether. Heat to 40-60℃, stir evenly, continue to heat to the target temperature, and continue stirring for 2-5 hours. After the reaction is completed, cool to 60-80℃, then add a neutralizing agent, stir for 20-30 minutes, then heat to 100-120℃ to remove water, filter, and obtain the modified intermediate. A2. Add 4,4'-diaminodiphenyl ether to N,N-dimethylformamide and stir until homogeneous to obtain a 4,4'-diaminodiphenyl ether solution. Add the modified intermediate to N,N-dimethylformamide and stir until homogeneous. After adding the catalyst, add the 4,4'-diaminodiphenyl ether solution dropwise. Heat to 60-80℃ and continue stirring the reaction. After the reaction is complete, extract and wash to obtain the modifier.

3. The pesticide microcapsule based on bio-based raw materials according to claim 2, characterized in that, In A1, the type of castor oil polyoxyethylene ether is castor oil polyoxyethylene ether EL40.

4. The pesticide microcapsule based on bio-based raw materials according to claim 2, characterized in that, In A1, the target temperature is 120-140℃.

5. A pesticide microcapsule based on bio-based raw materials according to claim 2, characterized in that, In A1, the neutralizing agent is phosphoric acid.

6. A pesticide microcapsule based on bio-based raw materials according to claim 2, characterized in that, In A1, the alkaline catalyst is potassium hydroxide.

7. A pesticide microcapsule based on bio-based raw materials according to claim 2, characterized in that, In A2, the catalyst is silver tetrafluoroborate or scandium trifluoromethanesulfonate.

8. A pesticide microcapsule based on bio-based raw materials according to claim 2, characterized in that, In A2, the stirring reaction time ranges from 10 to 12 hours.

9. A method for preparing pesticide microcapsules based on bio-based raw materials as described in claim 1, characterized in that, Includes the following steps: Step 1: Add castor oil, modifier and isophorone diisocyanate to the reactor, heat to 80-90℃, react for 30-40 minutes, then add dibutyltin dilaurate, and continue to react at 80-90℃ for 3-5 hours to obtain the prepolymer. Step 2: Melt the high-efficiency cypermethrin and mix it with the prepolymer to obtain a mixed oil phase; heat the polyvinyl alcohol solution to 50-60℃ and quickly disperse it into the mixed oil phase; use a high-shear homogenizer for initial emulsification; then homogenize under high pressure at 450-550 Bar for 6-8 minutes to form a uniform emulsion. Step 3: Maintain the temperature at 50-60℃ and stir the emulsion at 450-550 rpm for 4-6 hours to carry out the interfacial polymerization reaction. After the reaction is completed, pesticide microcapsules are obtained.

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