A microcapsule suspension of allosamidin and a method for preparing the same

Abstract

This invention relates to the field of sanitary insecticide technology, specifically to a chlorpyrifos microcapsule suspension and its preparation method. Using chlorpyrifos, isopropyl diisocyanate, a nanocrystalline composition, dibutyltin dilaurate, and deionized water as raw materials, this invention employs interfacial polymerization and emulsion template methods to prepare a chlorpyrifos microcapsule suspension that is easy to handle, allows for controlled release, has high utilization, high encapsulation efficiency, and low toxicity. In the nanocrystalline composition, the hydroxyl groups of starch and cellulose nanocrystals undergo esterification with octenyl succinic acid, enhancing electrostatic stability by increasing interparticle repulsion. The emulsifying ability and amphiphilicity of the starch and cellulose nanocrystals are enhanced, playing a crucial role in the formation and stability improvement of the microcapsule suspension. Compared with existing technologies, this invention has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of sanitary insecticide technology, and in particular to a chlorpyrifos microcapsule suspension and its preparation method. Background Technology

[0002] In the field of pest control, protecting people's living environment from pest infestation is of paramount importance. Chlorpyrifos, as a highly effective and low-toxicity pyrethroid insecticide, occupies an important position in this field due to its powerful fumigation, contact killing, and repellent effects against various pests such as mosquitoes, flies, and cockroaches, as well as its rapid knockdown and strong killing power.

[0003] In existing applications, chlorpyrifos is widely used in sanitary insecticide products such as electric mosquito coils, mosquito repellent discs, liquid mosquito repellents, and aerosols. In electric mosquito coils, each coil contains 250mg of the agent, achieving an 80% kill rate against Culex pipiens pallens when heated to 150℃. In mosquito repellent discs, the commonly used content is 0.5%-1.2%, providing good control of houseflies and mosquitoes. Liquid mosquito repellents are stable, leave no residue, and are suitable for long-term household use. When using aerosols for housefly control, the recommended dosage is 5.8-10mg / m³. Chlorpyrifos is not only suitable for household pest control but also has potential applications in areas such as grain storage pest control.

[0004] Microencapsulated suspensions, as an advanced pesticide formulation, exhibit significant advantages over other formulations in several aspects. Firstly, in terms of prolonged efficacy, they encapsulate the active ingredient within a polymeric capsule wall, forming a stable microcapsule structure. This structure effectively protects the active ingredient from external environmental factors, allowing for slow and sustained release. For example, microencapsulated suspensions of lambda-cyhalothrin extend the effective period by 30%-50% compared to conventional formulations when controlling cotton bollworm, reducing the number of applications by two per season. Secondly, in terms of reduced toxicity, microencapsulated suspensions can mask some of the irritant and odor of chemical agents, improving safety. For instance, when lambda-cyhalothrin, which is irritating to human skin, is formulated as a microencapsulated suspension, the active ingredient is encapsulated, reducing direct contact with human skin and lowering the risk of allergies or poisoning. Thirdly, in terms of reducing environmental pollution, the slow release of the active ingredient in microencapsulated suspensions reduces the dosage and frequency of application, thereby reducing pesticide residue pollution to soil, water, and air. Meanwhile, its water-based formulation avoids the extensive use of organic solvents, reducing harm to the atmospheric environment and making it more environmentally friendly.

[0005] In the prior art, patent document CN111374147A discloses a sanitary insecticide composition containing chlorpyrifos and propoxur. The active ingredients of the compound insecticide are chlorpyrifos and propoxur, and the weight ratio of chlorpyrifos to propoxur is 1:20-1:1, preferably 1:10-1:5. It has the advantages of high efficiency, low toxicity and environmental friendliness. However, chlorpyrifos is unstable in light and air, easily decomposes, has high volatility, and has a certain irritating odor. At present, the microencapsulation methods mainly include interfacial polymerization, in-situ polymerization, solvent evaporation and complex coagulation, but they often face the problems of low encapsulation rate and cumbersome steps.

[0006] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a chlorpyrifos microcapsule suspension and its preparation method. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a chlorpyrifos microcapsule suspension and its preparation method, so as to solve the problems of low encapsulation rate, high utilization rate and complicated operation of chlorpyrifos microcapsule suspension in the prior art.

[0008] To achieve the above objectives, the present invention provides a chlorpyrifos microcapsule suspension and its preparation method.

[0009] A chlorpyrifos microcapsule suspension, wherein the chlorpyrifos microcapsule suspension is prepared from chlorpyrifos, isopropyl diisocyanate, nanocrystal composition, dibutyltin dilaurate and deionized water;

[0010] The nanocrystal composition was prepared from starch nanocrystals, cellulose nanocrystals and octenyl succinic anhydride.

[0011] Preferably, the preparation method of the nanocrystal composition is as follows:

[0012] Step A1. Add starch nanocrystals and cellulose nanocrystals to deionized water, sonicate for 30-50 min, add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 8-9, and obtain suspension A;

[0013] Step A2. Add octenyl succinic anhydride to ethanol and dissolve it completely. Then, add it dropwise to suspension A within 1 hour while stirring. Keep the pH of the system at 8-9 and react for 2-3 hours. Then, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze dry to obtain the nanocrystalline composition.

[0014] Preferably, the ratio of starch nanocrystals, cellulose nanocrystals and deionized water in step A1 is 18-25g: 5-12g: 400-600mL.

[0015] Preferably, the method for preparing the starch nanocrystals in step A1 is as follows:

[0016] Add sulfuric acid solution to corn starch and stir at 38-43℃ for 3-4 days. After centrifugation at 9000-11000 rpm for 10-15 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable. After freeze-drying, starch nanocrystals are obtained.

[0017] Preferably, the ratio of corn starch to sulfuric acid solution is 170-188g:1000-1200mL;

[0018] The corn starch has a number-average molecular weight of 180-200 kDa and an amylose content of 27% wt%.

[0019] The concentration of the sulfuric acid solution is 3.16 mol / L.

[0020] A method for preparing a chlorpyrifos microcapsule suspension includes the following steps:

[0021] Step S1. Place chlorpyrifos, isopropyl diisocyanate and dibutyltin dilaurate in a water bath at 55-62℃, mix them evenly, and obtain the oil phase;

[0022] Step S2. Mix the nanocrystal composition with deionized water, sonicate for 30-50 min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 10000-11000 rpm for 2-3 min, then transfer to a high-pressure homogenizer, solidify, and cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0023] Preferably, the mass ratio of chlorpyrifos, isopropyl diisocyanate and dibutyltin dilaurate in step S1 is 10-17:1-1.5:0.05-0.13.

[0024] Preferably, the ratio of the nanocrystal composition to deionized water in step S2 is 0.05-0.062g:100-125mL.

[0025] Preferably, the curing temperature in step S2 is 58-63°C and the curing time is 6-7 hours.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a chlorpyrifos microcapsule suspension and its preparation method. Using chlorpyrifos, isopropyl diisocyanate, a nanocrystalline composition, dibutyltin dilaurate, and deionized water as raw materials, this invention employs interfacial polymerization and emulsion template methods to prepare a chlorpyrifos microcapsule suspension that is easy to handle, allows for controlled release, has high utilization, high encapsulation efficiency, and low toxicity. In the nanocrystalline composition, the hydroxyl groups of starch and cellulose nanocrystals undergo esterification with octenyl succinic acid, enhancing electrostatic stability by increasing interparticle repulsion. The emulsifying ability and amphiphilicity of the starch and cellulose nanocrystals are enhanced, playing a crucial role in the formation and stability improvement of the microcapsule suspension. Compared with existing technologies, this invention has broad application prospects. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0029] The sources and properties of some of the raw materials used in this invention are as follows:

[0030] Corn starch was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; sulfuric acid was purchased from China National Pharmaceutical Group Co., Ltd.; octenyl succinic acid was purchased from Shanghai Maclean Biochemical Co., Ltd.; isopropyl diisocyanate was purchased from Qiangjian Science Co., Ltd.; dibutyltin dilaurate was purchased from Qiangjian Science Co., Ltd.; and chlorpyrifos was purchased from Hubei Bojie Biotechnology Co., Ltd.

[0031] Example 1: A method for preparing a chlorpyrifos microcapsule suspension, comprising the following steps:

[0032] S1. Add 1000 mL of sulfuric acid solution with a concentration of 3.16 mol / L to 170 g of corn starch, stir at 38 °C for 3 days, centrifuge at 9000 rpm for 10 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable, freeze dry to obtain starch nanocrystals;

[0033] S2. Add 18g of starch nanocrystals and 5g of cellulose nanocrystals to 400mL of deionized water, sonicate for 30min, and add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 8 to obtain suspension A;

[0034] S3. Add 1g of octenyl succinic anhydride to 5mL of ethanol. After it is completely dissolved, add it dropwise to suspension A within 1h while stirring. Keep the pH of the system at 8. After reacting for 2h, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze dry to obtain the nanocrystalline composition.

[0035] S4. Place 10g of chlorpyrifos, 1g of isopropyl diisocyanate and 0.05g of dibutyltin dilaurate in a 55℃ water bath, mix well, and obtain the oil phase;

[0036] S5. Mix 0.05g of nanocrystal composition with 100mL of deionized water, sonicate for 30min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 10000rpm for 2min, then transfer to a high-pressure homogenizer and cure at 58℃ for 6h. Cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0037] Example 2: A method for preparing a chlorpyrifos microcapsule suspension, comprising the following steps:

[0038] S1. Add 1030 mL of sulfuric acid solution with a concentration of 3.16 mol / L to 173 g of corn starch, stir at 38 °C for 3 days, centrifuge at 9000 rpm for 10 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable, freeze dry to obtain starch nanocrystals;

[0039] S2. Add 19g of starch nanocrystals and 6g of cellulose nanocrystals to 440mL of deionized water, sonicate for 33min, and add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 8 to obtain suspension A;

[0040] S3. Add 1.1g of octenyl succinic anhydride to 5.5mL of ethanol. After complete dissolution, add it dropwise to suspension A within 1h while stirring. Keep the pH of the system at 8. After reacting for 2h, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze-dry to obtain the nanocrystalline composition.

[0041] S4. Place 11g of chlorpyrifos, 1.1g of isopropyl diisocyanate and 0.06g of dibutyltin dilaurate in a water bath at 55℃, mix them evenly, and obtain the oil phase;

[0042] S5. Mix 0.052g of nanocrystal composition with 104mL of deionized water, sonicate for 33min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 10000rpm for 2min, then transfer to a high-pressure homogenizer, stir at 58℃ for 6h, and cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0043] Example 3: A method for preparing a chlorpyrifos microcapsule suspension, comprising the following steps:

[0044] S1. Add 1060 mL of sulfuric acid solution with a concentration of 3.16 mol / L to 176 g of corn starch, stir at 38 °C for 3 days, centrifuge at 9000 rpm for 12 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable, freeze dry to obtain starch nanocrystals;

[0045] S2. Add 20g of starch nanocrystals and 7g of cellulose nanocrystals to 480mL of deionized water, sonicate for 36min, and add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 8 to obtain suspension A;

[0046] S3. Add 1.2g of octenyl succinic anhydride to 6mL of ethanol. After it is completely dissolved, add it dropwise to suspension A within 1h while stirring. Keep the pH of the system at 8. After reacting for 2h, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze dry to obtain the nanocrystalline composition.

[0047] S4. Place 12g of chlorpyrifos, 1.2g of isopropyl diisocyanate and 0.07g of dibutyltin dilaurate in a water bath at 58℃, mix thoroughly, and obtain the oil phase;

[0048] S5. Mix 0.054g of nanocrystal composition with 108mL of deionized water, sonicate for 36min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 10000rpm for 2min, then transfer to a high-pressure homogenizer, cure at 60℃ for 6h, and cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0049] Example 4: A method for preparing a chlorpyrifos microcapsule suspension, comprising the following steps:

[0050] S1. Add 1120 mL of sulfuric acid solution with a concentration of 3.16 mol / L to 179 g of corn starch, stir at 40 °C for 3 days, centrifuge at 10000 rpm for 12 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable, freeze dry to obtain starch nanocrystals;

[0051] S2. Add 21g of starch nanocrystals and 8g of cellulose nanocrystals to 520mL of deionized water, sonicate for 40min, and add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 9 to obtain suspension A;

[0052] S3. Add 1.3g of octenyl succinic anhydride to 6.5mL of ethanol. After complete dissolution, add it dropwise to suspension A within 1h while stirring. Keep the pH of the system at 9. After reacting for 3h, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze-dry to obtain the nanocrystalline composition.

[0053] S4. Place 13g of chlorpyrifos, 1.3g of isopropyl diisocyanate and 0.08g of dibutyltin dilaurate in a water bath at 58℃, mix thoroughly, and obtain the oil phase;

[0054] S5. Mix 0.056g of nanocrystal composition with 113mL of deionized water, sonicate for 40min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 10000rpm for 3min, then transfer to a high-pressure homogenizer and cure at 60℃ for 7h. Cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0055] Example 5: A method for preparing a chlorpyrifos microcapsule suspension, comprising the following steps:

[0056] S1. Add 1150 mL of sulfuric acid solution with a concentration of 3.16 mol / L to 182 g of corn starch, stir at 40 °C for 4 days, centrifuge at 10000 rpm for 15 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable, freeze dry to obtain starch nanocrystals;

[0057] S2. Add 22g of starch nanocrystals and 9g of cellulose nanocrystals to 520mL of deionized water, sonicate for 44min, and add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 9 to obtain suspension A;

[0058] S3. Add 1.4g of octenyl succinic anhydride to 7mL of ethanol. After complete dissolution, add it dropwise to suspension A within 1h while stirring. Keep the pH of the system at 9. After reacting for 3h, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze-dry to obtain the nanocrystalline composition.

[0059] S4. Place 15g of chlorpyrifos, 1.4g of isopropyl diisocyanate and 0.09g of dibutyltin dilaurate in a 60℃ water bath, mix well, and obtain the oil phase;

[0060] S5. Mix 0.058g of the nanocrystal composition with 117mL of deionized water, sonicate for 44min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 11000rpm for 3min, then transfer to a high-pressure homogenizer and cure at 58℃ for 7h. Cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0061] Example 6: A method for preparing a chlorpyrifos microcapsule suspension, comprising the following steps:

[0062] S1. Add 1170 mL of sulfuric acid solution with a concentration of 3.16 mol / L to 185 g of corn starch, stir at 43 °C for 3 days, centrifuge at 11000 rpm for 15 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable, freeze dry to obtain starch nanocrystals;

[0063] S2. Add 24g of starch nanocrystals and 10g of cellulose nanocrystals to 570mL of deionized water, sonicate for 47min, and add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 9 to obtain suspension A;

[0064] S3. Add 1.5g of octenyl succinic anhydride to 7.5mL of ethanol. After complete dissolution, add it dropwise to suspension A within 1h while stirring. Keep the pH of the system at 8. After reacting for 2h, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze-dry to obtain the nanocrystalline composition.

[0065] S4. Place 16g of chlorpyrifos, 1.5g of isopropyl diisocyanate and 0.1g of dibutyltin dilaurate in a water bath at 62℃, mix thoroughly, and obtain the oil phase;

[0066] S5. Mix 0.06g of nanocrystal composition with 120mL of deionized water, sonicate for 47min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 11000rpm for 3min, then transfer to a high-pressure homogenizer and cure at 63℃ for 6h. Cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0067] Example 7: A method for preparing a chlorpyrifos microcapsule suspension, comprising the following steps:

[0068] S1. Add 1200 mL of sulfuric acid solution with a concentration of 3.16 mol / L to 188 g of corn starch, stir at 43 °C for 4 days, centrifuge at 11000 rpm for 15 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable, freeze dry to obtain starch nanocrystals;

[0069] S2. Add 25g starch nanocrystals and 12g cellulose nanocrystals to 600mL of deionized water, sonicate for 50min, and add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 9 to obtain suspension A;

[0070] S3. Add 1.6g of octenyl succinic anhydride to 8mL of ethanol. After complete dissolution, add it dropwise to suspension A within 1h while stirring. Keep the pH of the system at 9. After reacting for 3h, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze-dry to obtain the nanocrystalline composition.

[0071] S4. Place 17g of chlorpyrifos, 1.5g of isopropyl diisocyanate and 0.13g of dibutyltin dilaurate in a water bath at 62℃, mix thoroughly, and obtain the oil phase;

[0072] S5. Mix 0.062g of nanocrystal composition with 125mL of deionized water, sonicate for 50min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 11000rpm for 3min, then transfer to a high-pressure homogenizer and cure at 63℃ for 7h. Cool to room temperature to obtain chlorpyrifos microcapsule suspension.

[0073] Comparative Example 1:

[0074] Compared with Example 1, this comparative example did not add starch nanocrystals during the preparation of the nanocrystal composition. All other steps and parameters were the same, and will not be repeated here. Finally, chlorpyrifos microcapsule suspension was obtained.

[0075] Comparative Example 2:

[0076] Compared with Example 1, this comparative example did not add cellulose nanocrystals during the preparation of the nanocrystal composition. All other steps and parameters were the same, and will not be repeated here. Finally, chlorpyrifos microcapsule suspension was obtained.

[0077] Comparative Example 3:

[0078] This comparative example differs from Example 1 only in that the "nanocrystalline composition" is replaced with "starch nanocrystals". All other steps and parameters are the same, and will not be repeated here. The final product is chlorpyrifos microcapsule suspension.

[0079] Comparative Example 4:

[0080] This comparative example differs from Example 1 only in that the "nanocrystalline composition" is replaced with "cellulose nanocrystals". All other steps and parameters are the same, and will not be repeated here. The final product is chlorpyrifos microcapsule suspension.

[0081] Comparative Example 5:

[0082] Compared with Example 1, this comparative example only replaces "nanocrystalline composition" with "18g starch nanocrystals and 5g cellulose nanocrystals". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, chlorpyrifos microcapsule suspension is obtained.

[0083] Performance testing:

[0084] 1. Indoor efficacy test for controlling mosquitoes and flies:

[0085] Experimental target: Culex pipiens pallens, female adult mosquitoes that did not feed on blood on days 3-5 after emergence;

[0086] Houseflies, adults on the 3rd or 4th day after emergence, half male and half female;

[0087] Test method: Refer to GB / T13917.1-2009, forced contact method;

[0088] Experimental treatment: The chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5 were diluted 100 times respectively;

[0089] 2. Efficacy test of pesticides for controlling cockroaches:

[0090] Experimental target: German cockroach, 10-15 day old adults, half male and half female;

[0091] Test method: Refer to GB / T13917.1-2009, forced contact method;

[0092] Experimental treatment: The chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5 were diluted 100 times respectively;

[0093] 3. Determination of encapsulation rate: The content of free chlorpyrifos in the chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5 was determined by high performance liquid chromatography, and the encapsulation rate was calculated.

[0094] Determination of total pesticide content: Accurately weigh 1.0 g each of the chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5, add 10 mL of methanol, and then place the mixture in an ultrasonic cell disruptor for ultrasonic cell disruption. The disruption is performed with an ultrasonic time of 30 s, an interval of 20 s, and 10 cycles at an ultrasonic power of 200 Ω. After ultrasonic disruption, transfer the mixture to a 50 mL volumetric flask, dilute to the mark with ethanol, and shake well. Filter the mixture, and then filter the filtrate through a 0.45 μm filter membrane to obtain the sample. The pesticide concentration in the sample is determined by HPLC.

[0095] Determination of free pesticide content: Accurately weigh 1.0 g each of the chlorpyrifos microcapsule suspension prepared in Examples 1-7 and Comparative Examples 1-5, dissolve in 25 ml of ethanol solution, shake well, then transfer to a 50 ml volumetric flask, add ethanol to dilute to the mark and shake well, filter, filter the filtrate through a 0.45 μm filter membrane to obtain the sample, and detect the pesticide concentration in the sample by HPLC.

[0096] 4. Encapsulation ratio calculation formula:

[0097] .

[0098] Suspension rate determination: The suspension rate of the chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5 was determined according to the national standard GB / T14825-2006.

[0099] 5. Determination of microcapsule size and distribution:

[0100] The particle size of the microcapsules in the chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5 was determined using a laser particle size analyzer. 10 D 50 and D 90 And calculate the dispersion index (Span). The formula for calculating the dispersion index (Span) is as follows:

[0101]

[0102] In the formula, D 10 The cumulative distribution of particle size at 10% indicates that 10% of the particles have a diameter less than or equal to this value. (D) 50 The particle size at which the cumulative distribution is 50% indicates that 50% of the particles have a diameter less than or equal to this value, D. 90 The particle size at which the cumulative distribution is 90% indicates that 90% of the particles have a diameter less than or equal to this value.

[0103] Formula meaning: Numerator D90−D10: represents the range of particle distribution (from 10% to 90% of the particle size span), denominator D50: represents the median particle size, used to standardize the distribution range, and the dispersion index (Span) measures the relative width of the distribution range with respect to the median. The smaller the value, the more concentrated the particle distribution and the higher the uniformity.

[0104] 6. Low temperature stability: The suspension rate of the chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5 was determined according to the national standard GB / T19136-2003.

[0105] 7. Thermal storage stability: The suspension rate of the chlorpyrifos microcapsule suspensions prepared in Examples 1-7 and Comparative Examples 1-5 was determined according to the national standard GB / T19136-2003.

[0106] Table 1. Summary of experimental data from Examples 1-7 and Comparative Examples 1-5

[0107]

[0108] Table 2 Summary of experimental data from Examples 1-7 and Comparative Examples 1-5

[0109]

[0110] Table 3 Summary of experimental data from Examples 1-7 and Comparative Examples 1-5

[0111]

[0112] Data Analysis:

[0113] As can be seen from Tables 1-3, the chlorpyrifos microcapsule suspension prepared by this invention has a higher encapsulation rate and a higher utilization rate. This may be because this invention uses chlorpyrifos, isopropyl diisocyanate, nanocrystalline composition, dibutyltin dilaurate, and deionized water as raw materials, and adopts interfacial polymerization and emulsion template method to prepare a chlorpyrifos microcapsule suspension that is easy to operate and control release, has a high utilization rate, a high encapsulation rate, and low toxicity. In the nanocrystalline composition, starch nanocrystals and cellulose nanocrystals have good emulsifying ability and are easy to biodegrade. The hydroxyl groups in the molecules undergo esterification reaction with octenyl succinic acid, which improves electrostatic stability by enhancing the repulsive force between particles. The enhanced emulsifying ability and improved amphiphilicity of starch nanocrystals and cellulose nanocrystals play an important role in the formation and stability improvement of the microcapsule suspension.

[0114] Comparative Example 1, which did not add starch nanocrystals during the preparation of the nanocrystal composition, and Comparative Example 2, which did not add cellulose nanocrystals during the preparation of the nanocrystal composition, showed worse encapsulation efficiency and utilization rate of their chlorpyrifos microcapsule suspensions compared to Example 1. This may be because the cellulose nanocrystals modified with octenyl succinic acid and the starch nanocrystals formed a composite particle layer during the preparation of the microcapsule suspension, creating a denser physical barrier at the oil-water interface. The surface charges in their molecules generate synergistic electrostatic repulsion, inhibiting particle aggregation and maintaining emulsion stability. Furthermore, the hydroxyl groups may react with isocyanate groups, participating in the polyurethane shell layer. The formation of these components enhances the chemical stability of the microcapsule suspension and improves the encapsulation efficiency. In Comparative Example 3, the "nanocrystalline composition" was replaced with "starch nanocrystals," in Comparative Example 4, the "nanocrystalline composition" was replaced with "cellulose nanocrystals," and in Comparative Example 5, the "nanocrystalline composition" was replaced with "18g of starch nanocrystals and 5g of cellulose nanocrystals." The encapsulation efficiency and utilization rate of the chlorpyrifos microcapsule suspension were worse than those of Example 1. This may be because the esterification reaction with octenyl succinic acid did not occur. Cellulose nanocrystals and starch nanocrystals have strong hydrophilicity and poor amphiphilicity and emulsifying properties, which limits their application in microcapsule suspensions, resulting in poor encapsulation efficiency and bioavailability.

[0115] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0116] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A chlorpyrifos microcapsule suspension, characterized in that, The chlorpyrifos microcapsule suspension was prepared from chlorpyrifos, isopropyl diisocyanate, nanocrystal composition, dibutyltin dilaurate and deionized water; The nanocrystal composition was prepared from starch nanocrystals, cellulose nanocrystals and octenyl succinic anhydride; The preparation method of the nanocrystal composition is as follows: Step A1. Add starch nanocrystals and cellulose nanocrystals to deionized water, sonicate for 30-50 min, add 3% sodium hydroxide aqueous solution to adjust the pH of the system to 8-9, and obtain suspension A; Step A2. Add octenyl succinic anhydride to ethanol and dissolve it completely. Then, add it dropwise to suspension A within 1 hour while stirring. Keep the pH of the system at 8-9 and react for 2-3 hours. Then, add 3% hydrochloric acid aqueous solution to adjust the pH of the system to 6.

5. After centrifugation, wash twice with 70% ethanol aqueous solution, wash once with anhydrous ethanol, and freeze dry to obtain the nanocrystalline composition. The ratio of starch nanocrystals, cellulose nanocrystals and deionized water used in step A1 is 18-25g: 5-12g: 400-600mL; The preparation method of starch nanocrystals in step A1 is as follows: Add sulfuric acid solution to corn starch and stir at 38-43℃ for 3-4 days. After centrifugation at 9000-11000 rpm for 10-15 min, add deionized water and repeat centrifugation until the pH of the supernatant is stable. After freeze-drying, starch nanocrystals are obtained. The ratio of corn starch to sulfuric acid solution is 170-188g:1000-1200mL; The corn starch has a number-average molecular weight of 180-200 kDa and an amylose content of 27% wt%. The concentration of the sulfuric acid solution is 3.16 mol / L; The ratio of octenyl succinic anhydride to ethanol in step A2 is 1-1.6 g: 5-8 mL; The preparation method of the chlorpyrifos microcapsule suspension includes the following steps: Step S1. Place chlorpyrifos, isopropyl diisocyanate and dibutyltin dilaurate in a water bath at 55-62℃, mix them evenly, and obtain the oil phase; Step S2. Mix the nanocrystal composition with deionized water, sonicate for 30-50 min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 10000-11000 rpm for 2-3 min, then transfer to a high-pressure homogenizer, solidify, and cool to room temperature to obtain chlorpyrifos microcapsule suspension. The mass ratio of chlorpyrifos, isopropyl diisocyanate and dibutyltin dilaurate in step S1 is 10-17:1-1.5:0.05-0.13; In step S2, the ratio of the nanocrystal composition to deionized water is 0.05-0.062 g: 100-125 mL.

2. The method for preparing the chlorpyrifos microcapsule suspension according to claim 1, characterized in that, Includes the following steps: Step S1. Place chlorpyrifos, isopropyl diisocyanate and dibutyltin dilaurate in a water bath at 55-62℃, mix them evenly, and obtain the oil phase; Step S2. Mix the nanocrystal composition with deionized water, sonicate for 30-50 min to obtain an aqueous phase, add the oil phase to the aqueous phase, emulsify at 10000-11000 rpm for 2-3 min, then transfer to a high-pressure homogenizer, solidify, and cool to room temperature to obtain chlorpyrifos microcapsule suspension.

3. The method for preparing the chlorpyrifos microcapsule suspension according to claim 2, characterized in that, The curing temperature in step S2 is 58-63℃ and the curing time is 6-7h.

Images