PH response type pesticide microcapsule and preparation method thereof

Abstract

The invention discloses a pH response type pesticide microcapsule and a preparation method thereof, and the preparation method comprises the following steps: mixing a pesticide raw material, an organic cosolvent and a diisocyanate monomer to obtain an oil phase; mixing a surfactant with water to obtain a water phase; adding the oil phase into the water phase, and carrying out shear emulsification to obtain O / W type emulsion; and mixing the O / W type emulsion with an aqueous solution of polyamine containing the vanillyl Schiff base structure, and carrying out an interfacial polymerization reaction to obtain the pH response type polyurethane pesticide microcapsule with the vanillyl Schiff base structure. According to the invention, the organic cosolvent and diisocyanate are used as oil phase components, can dissolve the raw pesticide and do not react with the raw pesticide, has good pH responsiveness, can realize stimulation response to an acid environment caused by pathogenic bacteria infected crops, improves the utilization rate of the pesticide, and reduces the usage amount of the pesticide.

Description

Technical Field

[0001] The invention relates to the technical field of pesticide nano-microcapsules, and in particular to a pH-responsive pesticide microcapsule and a preparation method thereof. Background Art

[0002] Pesticide microcapsules are microcapsules that encapsulate pesticide droplets with certain polymer compounds. They are made of pesticide originals, adjuvants, capsule walls, etc. The capsule wall is usually made of synthetic or natural polymer compounds, such as polyamide, polyester, animal and plant glue (such as alginate, gelatin, gum arabic), etc. It is a semi-permeable membrane that can control the release rate of pesticides. The preparation is a flowable suspension. When used, it is diluted with water and the microcapsules are suspended in water for foliar spraying or soil application. After application, the pesticide is gradually released from the capsule wall to achieve a control effect. For some pesticides with non-target biological toxicity, such as pyraclostrobin, tebuconazole and hexaconazole (with acute toxicity to aquatic invertebrates), the sustained release effect of microcapsules can reduce the amount of pesticides used and the number of applications, thereby reducing the toxicity of pesticides to non-target organisms.

[0003] Interfacial polymerization is a common process for preparing microcapsules, and emulsion preparation is the first step of interfacial polymerization. At present, the preparation of emulsion requires the use of a large amount of organic solvents, such as toluene and xylene, which can easily cause environmental pollution. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a pH-responsive pesticide microcapsule and a preparation method thereof. The preparation method provided by the present invention can reduce the use of organic solvents and is more environmentally friendly.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing pH-responsive pesticide nano-microcapsules, comprising the following steps:

[0007] The pesticide technical, the organic cosolvent and the diisocyanate monomer are mixed to obtain an oil phase;

[0008] mixing the surfactant with water to obtain an aqueous phase;

[0009] Adding the oil phase to the water phase for shear emulsification to obtain an O / W emulsion;

[0010] The O / W type emulsion is mixed with vanillyl Schiff base polyamine and water to carry out interfacial polymerization reaction to obtain pH responsive pesticide microcapsules;

[0011] Preferably, the raw materials for preparing the pH-responsive pesticide microcapsules include, by weight:

[0012]

[0013] Preferably, the pesticide technical is one or more of hexaconazole, emamectin benzoate, pyraclostrobin, avermectin, carbendazim, thiophanate-methyl, tebuconazole, difenoconazole, propiconazole, flutriafol, diniconazole, myclobutanil, triadimefon, epoxiconazole, triadimenol, bisoprolol and cyproconazole.

[0014] Preferably, the vanillyl Schiff base is a reaction product of vanillin and a polyamine, and the polyamine is one or more of triethylenetetramine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine and isophoronediamine.

[0015] Preferably, the organic co-solvent is one or more of dimethylacetamide, ethyl acetate, butyl acetate, amyl acetate, sec-butyl acetate, isoamyl citrate, butanone, trimethylbenzene and cyclohexanone;

[0016] The surfactant is one or more of polyvinyl alcohol, Tween-80, EL-40, Span-60, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0017] Preferably, the diisocyanate monomer is one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate;

[0018] Preferably, the emulsification rate is 5000-20000 rpm, and the time is 1-15 min;

[0019] Preferably, the temperature of the interfacial polymerization reaction is 30 to 90° C., and the time is 1 to 5 hours.

[0020] The present invention provides a pH-responsive pesticide microcapsule prepared by the above-mentioned preparation method, comprising a microcapsule material and an oil phase component encapsulated in the microcapsule material;

[0021] The microcapsule material is polyurethane;

[0022] The oil phase components include pesticide technical, organic cosolvent and diisocyanate.

[0023] The present invention provides a preparation method of a pH-responsive pesticide microcapsule, comprising the following steps: mixing a pesticide original drug, an organic cosolvent and an isocyanate monomer to obtain an oil phase; mixing a surfactant with water to obtain an aqueous phase; adding the oil phase to the aqueous phase, performing shear emulsification, and obtaining an O / W type emulsion; mixing the O / W type emulsion with a polyamine containing a vanillyl Schiff base structure and water, and performing an interfacial polymerization reaction to obtain a pH-responsive polyurethane pesticide microcapsule having a vanillyl Schiff base structure. The suspension has the characteristics of controlled release, resistance to photolysis, and low toxicity. The present invention uses an organic cosolvent and a diisocyanate as oil phase components, can dissolve the pesticide original drug and does not react with the pesticide original drug, can partially replace the organic solvent to participate in the interfacial polymerization reaction, thereby reducing the use of organic solvents in the preparation process of the pesticide microcapsule. In addition, the Schiff base structure has good pH responsiveness, can achieve a stimulus response to the acidic environment caused by pathogenic bacteria infecting crops, improves the utilization rate of pesticides and reduces the amount used. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a SEM image of the pH-responsive pesticide microcapsules obtained in Example 1;

[0025] Figure 2 The cumulative release rate of the pH-responsive pesticide microcapsules obtained in Example 1 at different pH values ​​varies with time;

[0026] Figure 3 The curves of the pesticide retention rate of the pH-responsive pesticide microcapsules, pyraclostrobin technical drug and pyraclostrobin commercial drug obtained in Example 1 under ultraviolet conditions over time are shown;

[0027] Figure 4 The inhibitory effects of the pH-responsive pyraclostrobin-loaded pesticide microcapsules, pyraclostrobin original drug and pyraclostrobin commercial drug on rice sheath blight obtained in Example 1 are shown;

[0028] Figure 5 The inhibitory effect of the pH-responsive pyraclostrobin-loaded pesticide microcapsules obtained in Example 1 on Rhizoctonia solani at different pH values;

[0029] Figure 6 The results show the inhibitory effects of the pH-responsive pyraclostrobin-loaded pesticide microcapsules, pyraclostrobin original drug and pyraclostrobin commercial drug on rice sheath blight under ultraviolet conditions obtained in Example 1. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing pH-responsive pesticide microcapsules, comprising the following steps:

[0031] The pesticide technical, the organic cosolvent and the diisocyanate monomer are mixed to obtain an oil phase;

[0032] mixing the surfactant with water to obtain an aqueous phase;

[0033] Adding the oil phase to the water phase for shear emulsification to obtain an O / W emulsion;

[0034] The O / W emulsion is mixed with a polyamine containing a vanillyl Schiff base and water to perform an interfacial polymerization reaction to obtain pH-responsive pesticide microcapsules;

[0035] In the present invention, the raw materials for preparing the pH-responsive pesticide microcapsules preferably include, by weight:

[0036]

[0037] Unless otherwise specified, the raw materials described in the present invention are all commercially available.

[0038] In terms of mass fraction, the raw materials for preparing the pH-responsive pesticide microcapsules of the present invention preferably include 4 to 6 parts of the pesticide original drug, and more preferably 5 parts. In the present invention, the pesticide original drug is preferably one or more of hexaconazole, pyraclostrobin, avermectin, carbendazim, thiophanate-methyl, tebuconazole, difenoconazole, propiconazole, flutriafol, diniconazole, myclobutanil, triadimefon, epoxiconazole, triadimenol, isoprenaline and cyproconazole.

[0039] Based on the mass fraction of the pesticide original drug, the raw materials for preparing the pH-responsive pesticide microcapsules of the present invention preferably include 6 to 8 parts of an organic cosolvent, more preferably 7 parts. In the present invention, the organic cosolvent is preferably one or more of dimethylacetamide, ethyl acetate, butyl acetate, amyl acetate, sec-butyl acetate, isoamyl citrate, butanone, trimethylbenzene and cyclohexanone.

[0040] Based on the mass fraction of the pesticide original drug, the raw materials for preparing the pH-responsive pesticide nano-microcapsules of the present invention preferably include 1 to 3 parts of diisocyanate monomers, and more preferably 1.5 parts. In the present invention, the diisocyanate monomers are preferably toluene diisocyanate, diphenylmethane diisocyanate, one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate, and more preferably diphenylmethane diisocyanate.

[0041] Based on the mass fraction of the pesticide original drug, the raw materials for preparing the pH-responsive pesticide microcapsules of the present invention preferably include 2 to 4 parts of a surfactant, more preferably 3 parts. In the present invention, the surfactant is preferably one or more of polyvinyl alcohol, Tween-80, EL-40, Span-60, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate, more preferably polyvinyl alcohol.

[0042] Based on the mass fraction of the pesticide original drug, the raw materials for preparing the pH-responsive pesticide microcapsules of the present invention preferably include 2 to 5 parts of polyamine, more preferably 3 to 4 parts. In the present invention, the polyamine is preferably one or more of triethylenetetramine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine and isophoronediamine, more preferably triethylenetetramine.

[0043] The present invention mixes the pesticide technical, the organic cosolvent and the diisocyanate monomer to obtain an oil phase. In the present invention, the mixing method is preferably: first dissolve the pesticide technical and the organic cosolvent, and then add the diisocyanate monomer to dissolve after the two are completely dissolved.

[0044] The present invention mixes the surfactant with water to obtain an aqueous phase. In the present invention, the mass ratio of the surfactant to water is preferably 1-3:50-100, more preferably 2:100.

[0045] The present invention adds the oil phase to the water phase and performs shear emulsification to obtain an O / W emulsion. In the present invention, the oil phase is preferably added to the water phase by dropwise addition. In the present invention, the emulsification is preferably performed under high-speed shear conditions, the emulsification rate is preferably 5000-20000rmp, more preferably 8000rmp, and the time is preferably 1-15min, more preferably 10min.

[0046] After obtaining the O / W emulsion, the present invention mixes the O / W emulsion with vanillin Schiff base polyamine and water to perform interfacial polymerization reaction to obtain pH-responsive pesticide microcapsules. In the present invention, the vanillin Schiff base polyamine and water are preferably added in the form of an aqueous dispersion of the polyamine. In the present invention, the mass ratio of the vanillin Schiff base polyamine to water is preferably 1 to 4:10 to 50, more preferably 1:10.

[0047] In the present invention, the temperature of the interfacial polymerization reaction is preferably 40 to 50° C., more preferably 55° C., and the time is preferably 2 to 3 hours.

[0048] In the present invention, after the interfacial polymerization reaction, the present invention preferably performs post-treatment on the obtained interfacial polymerization reaction solution, and the post-treatment preferably includes:

[0049] The interfacial polymerization reaction liquid is subjected to solid-liquid separation, and the obtained solid is washed and dried in sequence to obtain pH-responsive pesticide microcapsule solid.

[0050] In the present invention, the solid-liquid separation method is preferably centrifugation at a rate of 4000 rpm / min for 5 minutes. In the present invention, the washing detergent is preferably distilled water, and the number of washings is preferably 3 times.

[0051] In the present invention, the drying method is preferably freeze-drying. The present invention has no special requirements for the freeze-drying method, and the freeze-drying method well known to those skilled in the art can be used.

[0052] The present invention provides a pH-responsive pesticide microcapsule prepared by the above-mentioned preparation method, comprising a microcapsule material and an oil phase component encapsulated in the microcapsule material;

[0053] The microcapsule material is polyurethane;

[0054] The oil phase components include pesticide technical, organic cosolvent and diisocyanate.

[0055] In the present invention, the optional types of the pesticide technical, organic co-solvent and diisocyanate are the same as above and will not be described in detail here.

[0056] The pH-responsive pesticide microcapsules and the preparation method thereof provided by the present invention are described in detail below in conjunction with the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] (1) Add 4.5 g of the original drug pyraclostrobin to a 50 ml beaker and dissolve it with 6.9 g of the cosolvent butyl acetate. Then add 1.125 g of diphenylmethane diisocyanate and continue to dissolve to obtain an oil phase.

[0059] (2) Weigh 0.5 g of PVA and dissolve it in 20 g of deionized water by heating and ultrasonication to prepare an aqueous phase.

[0060] (3) Under the condition of high-speed shearing at 8000 rpm, the oil phase was added dropwise to the water phase and the emulsification was continued for 10 min. After a uniform and stable emulsion was obtained, the emulsion was transferred into a 250 ml four-necked flask with a stirrer and the stirring was maintained for 10 min at a speed of 450 rpm.

[0061] (4) 20 ml of vanillin Schiff base polyamine aqueous solution was added dropwise to the mixed emulsion through a constant flow pump within 30 min, and the mixture was cured at 50 °C for 3 h to obtain pH-responsive pesticide polyurethane microcapsules.

[0062] (5) Finally, the obtained microcapsules were centrifuged at a rate of 4000 rpm / min for 5 min, washed three times with distilled water, and then collected and freeze-dried.

[0063] (6) The antifungal activity of pyraclostrobin pesticide microcapsules, pyraclostrobin original drug and pyraclostrobin commercial drug at different concentrations was tested using the mycelium growth rate method. The culture medium containing the fungicide was poured into a sterile culture dish with a diameter of 9 cm. After cooling, the filter cake with a diameter of 5 mm was inoculated and incubated in an incubator at 27±1°C. The colony diameter was measured using the cross method, and DMSO was used as the control group. Each treatment was performed three times.

[0064] Test Example 1

[0065] The obtained pH-responsive loaded pyraclostrobin pesticide microcapsules, pyraclostrobin technical and pyraclostrobin commercial drugs were subjected to biological activity tests. The results are shown in Table 1. The pyraclostrobin pesticide microcapsules, pyraclostrobin technical and pyraclostrobin commercial drugs were tested for biological activity against Rhizoctonia solani, Phomopsis spp., Botrytis cinerea, Morchella fasciata, Morchella fusarifolia and Mucor rubrum at concentrations of 50 μg / mL and 1 μg / mL, and the inhibitory effects were good.

[0066] Table 1 Determination of the biological activity of pyraclostrobin pesticide microcapsules, pyraclostrobin technical and pyraclostrobin commercial products against Rhizoctonia solani, Phomopsis spp., Botrytis cinerea, Trichoderma spp., Fusarium spp. and Mucor spp.

[0067]

[0068] Test Example 2

[0069] EC50 of Rhizoctonia solani, Phomopsis oryzae, Botrytis cinerea, Trichoderma spp., Fusarium spp. and Mucor spp. was further determined. The results are shown in Table 2. Figure 4 As shown, its EC 50 The results are as follows: 0.1878μg / mL, 0.2063μg / mL, and 0.2416μg / mL, respectively. Among them, the pyraclostrobin pesticide microcapsules had the best inhibitory effect on rice sheath blight. 50 =0.1878 μg / mL. This indicates that the prepared pyraclostrobin pesticide microcapsules can enhance the activity of pesticides and improve the inhibitory effect.

[0070] Table 2 Bioactivity determination of pyraclostrobin pesticide microcapsules, pyraclostrobin technical and pyraclostrobin commercial products against Rhizoctonia solani, Phomopsis spp., Botrytis cinerea, Trichoderma spp., Fusarium spp. and Mucor spp.

[0071]

[0072] (7) The mycelium growth rate method was used to test the antifungal activity of pyraclostrobin pesticide microcapsules under different pH conditions. Culture media with pH = 4.5, 7.1, and 9.0 were prepared, and the culture media containing 2 μg / mL concentration of pyraclostrobin pesticide microcapsules, pyraclostrobin original drug, and pyraclostrobin commercial drug were poured into a culture dish. After cooling, the filter cake with a diameter of 5 mm was inoculated and incubated in an incubator at 27±1°C. The colony diameter was measured using the cross method, CK was used as the control group, and each treatment was performed three times.

[0073] The obtained pH-responsive pyraclostrobin pesticide-loaded microcapsules were subjected to biological activity tests at different pH values. The results are shown in Table 3. Figure 5 As shown in the figure, under the conditions of pH = 4.5, 7.0 and 9.0, the inhibition rates of 2 μg / mL pyraclostrobin pesticide microcapsules on rice sheath blight were 65.09±1.82%, 43.27±1.50% and 44.73±1.30%, respectively. Under the condition of no addition of pyraclostrobin pesticide microcapsules, the inhibition rates of different pH (4.5, 7.0 and 9.0) on rice sheath blight were 37.45±1.37%, 26.55±1.10% and 28.36±1.07%, respectively. Among them, the inhibition rate of rice sheath blight was the highest when pH = 4.5, which may be due to the fact that the Schiff base structure in the pyraclostrobin pesticide microcapsules broke under acidic conditions, releasing pesticides, thereby achieving the inhibitory effect, indicating that the prepared pH-responsive pyraclostrobin pesticide microcapsules have pH responsiveness, can achieve controlled release of pesticides, improve utilization and reduce usage.

[0074] Table 3 Determination of the biological activity of pyraclostrobin pesticide microcapsules against Rhizoctonia solani at different pH conditions

[0075]

[0076] (8) The mycelium growth rate method was used to test the antifungal activity of pyraclostrobin pesticide microcapsules, pyraclostrobin technical and pyraclostrobin commercial drugs under ultraviolet light irradiation conditions. Pyraclostrobin pesticide microcapsules, pyraclostrobin technical and pyraclostrobin commercial drugs at a concentration of 2 μg / ml were irradiated under a 6 W ultraviolet lamp for 10 h and then poured into the culture medium. After cooling, the filter cake with a diameter of 5 mm was inoculated and incubated in an incubator at 27 ± 1 °C. The colony diameter was measured using the cross method, DMSO was used as the control group, and each treatment was performed three times.

[0077] The obtained pH-responsive microcapsules loaded with pyraclostrobin pesticide, pyraclostrobin original drug and pyraclostrobin commercial drug were tested for biological activity against Rhizoctonia solani under ultraviolet conditions. The results are shown in Table 4. Figure 6As shown in the figure, the inhibition rates of 2μg / mL pyraclostrobin pesticide microcapsules, pyraclostrobin technical and pyraclostrobin commercial drugs on rice sheath blight under ultraviolet irradiation were 26.56±1.39%, 16.88±1.02% and 24.06±0.95%, respectively. Among them, the inhibition rate of pyraclostrobin pesticide microcapsules was 26.56±1.39%, and the inhibition effect was better than that of pyraclostrobin technical and pyraclostrobin commercial drugs, indicating that pyraclostrobin pesticide microcapsules have the effect of alleviating the degradation of pesticides by ultraviolet and can improve the utilization rate of pesticides.

[0078] Table 4 Determination of the biological activity of pyraclostrobin pesticide microcapsules, pyraclostrobin original drug and pyraclostrobin commercial drug against Rhizoctonia solani under ultraviolet light conditions

[0079]

[0080] The cumulative release rate of the obtained pH-responsive pesticide microcapsules at different pH values ​​varies with time. Figure 2 shown.

[0081] The change curves of the pesticide retention rate of the obtained pH-responsive pesticide microcapsules, pyraclostrobin original drug and pyraclostrobin commercial drug under ultraviolet conditions are shown in Figure 2. Figure 3 shown.

[0082] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing pH-responsive pesticide microcapsules, comprising the following steps: The pesticide technical, the organic cosolvent and the diisocyanate monomer are mixed to obtain an oil phase; mixing the surfactant with water to obtain an aqueous phase; Adding the oil phase to the water phase for shear emulsification to obtain an O / W emulsion; The O / W type emulsion is mixed with vanillyl Schiff base polyamine and water to carry out interfacial polymerization reaction to obtain pH responsive pesticide microcapsules.

2. The preparation method according to claim 1, characterized in that: The raw materials for preparing the pesticide microcapsules include, by weight:

3. The preparation method according to claim 1 or 2, characterized in that: The pesticide technical is one or more of hexaconazole, pyraclostrobin, avermectin, carbendazim, thiophanate-methyl, tebuconazole, difenoconazole, propiconazole, flutriafol, diniconazole, myclobutanil, triadimefon, epoxiconazole, triadimenol, bisbenzimidazole and cyproconazole.

4. The preparation method according to claim 1 or 2, characterized in that: The vanillyl Schiff base is the reaction of vanillin and polyamine, and the polyamine is one or more of triethylenetetramine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine and isophoronediamine.

5. The preparation method according to claim 1 or 2, characterized in that: The organic co-solvent is one or more of dimethylacetamide, ethyl acetate, butyl acetate, amyl acetate, sec-butyl acetate, isoamyl citrate, butanone, trimethylbenzene and cyclohexanone; The surfactant is one or more of polyvinyl alcohol, Tween-80, EL-40, Span-60, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

6. The preparation method according to claim 1 or 2, characterized in that: The diisocyanate monomer is one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate.

7. The preparation method according to claim 1, characterized in that: The emulsification rate is 5000-20000 rpm, and the time is 1-15 minutes.

8. The preparation method according to claim 1, characterized in that: The temperature of the interfacial polymerization reaction is 30-90° C. and the time is 1-5 hours.

9. The pH-responsive pesticide microcapsules prepared by the preparation method according to any one of claims 1 to 8, comprising microcapsule materials and oil phase components encapsulated in the microcapsule materials; The microcapsule material is polyurethane; The oil phase components include pesticide technical, organic cosolvent and vanillyl Schiff base polyamine.

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