Preparation method of surfactant containing tea saponin and application of surfactant in pesticide

Abstract

The invention discloses a preparation method of a surfactant containing tea saponin and application of the surfactant in pesticides, and belongs to the technical field of pesticide production.The tea saponin and chitosan polylactic acid core-shell microspheres are compounded through esterification reaction, the high water solubility of the tea saponin enables liquid medicine to be more easily spread on leaf surfaces, and the water solubility of the liquid medicine is higher than that of the chitosan polylactic acid core-shell microspheres; after the chitosan polylactic acid core-shell microspheres are subjected to fluorination treatment, the hydrophobicity provided by the chitosan polylactic acid core-shell microspheres can form a low-surface-energy layer, so that water drop infiltration can be prevented, and the chitosan polylactic acid core-shell microspheres are not easy to wash away by rainwater after being sprayed on the surfaces of crops; sulfonic groups contained in the chitosan polylactic acid core-shell microspheres can provide electrostatic repulsion, a dispersion system can be stabilized, and agglomeration of the chitosan polylactic acid core-shell microspheres is avoided; when the tea saponin is sprayed into soil as a pesticide, heavy metals in the soil can be chelated, amino groups and sulfonic acid groups on the surface of the chitosan can enhance the chelating effect on the heavy metals, and the polylactic acid is easily decomposed into lactic acid by microorganisms in the soil, so that dissolution of heavy metal carbonate can be promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pesticide production, and particularly relates to a preparation method of a surfactant containing tea saponin and application of the surfactant in pesticides. BACKGROUND

[0002] A chemical insecticide is a toxic chemical agent which can kill pests of crops and trees or has an important influence on the physiological activity of pests with a small amount. The chemical insecticide has the advantages of low use cost, quick effect, various types, wide prevention and treatment objects, and the disadvantages of causing environmental pollution, accumulation of residues of the pesticide in food through concentration of a food chain, enrichment of the pesticide in the human body after the food is eaten, and threat to the health and life of the human being, easy to cause major diseases such as cancer, and easy to cause drug resistance of pests.

[0003] The tea shoot moth is a lepidoptera and belongs to the family of oxycephalidae, and the host is tea, oil tea and camellia. The host is mainly damaged by the larva which eats the new shoot of the tea tree, causes the new shoot to die, and affects the yield of tea. At present, the drugs mainly used for the prevention and treatment of the tea shoot moth include 40% dimethoate, 80% dichlorvos emulsion 1500 times liquid, 2.5% Tianwangxing emulsion 3000 times liquid and 50% baidan powder 1500 times liquid.

[0004] Tea saponin, also known as tea saponin, is a plant insecticide extracted from seeds of plants in the theaceae family, such as tea seed cake and tea leaf seed cake after oil extraction. The effective component belongs to pentacyclic triterpenoids, tastes bitter and pungent, is easily soluble in water, alcohol and other organic solvents, has a touch-killing and antifeeding effect on pests. Tea saponin is also a natural non-ionic surfactant which has good emulsifying, dispersing, foaming, wetting and other functions.

[0005] A kind of insecticide containing tea saponin and its preparation method are disclosed in Chinese patent CN107484778B. The effective component of the insecticide in the scheme is extracted from oil tea seed cake and safflower, which is a plant source insecticide, has little environmental pollution and is environment-friendly. However, the natural tea saponin is easily washed away by rainwater due to its high water solubility when sprayed on the leaf surface of crops. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a surfactant containing tea saponin and application of the surfactant in pesticides. The tea saponin is compounded with chitosan polylactic acid core-shell microspheres through esterification reaction. The high water solubility of tea saponin makes the pesticide solution more easily spread on the leaf surface. The hydrophobicity provided by the fluorinated chitosan polylactic acid core-shell microspheres can form a low surface energy layer, which can prevent water droplets from wetting, so that the chitosan polylactic acid core-shell microspheres are not easily washed away by rainwater when sprayed on the surface of crops. In addition, the sulfonic acid group contained in the chitosan polylactic acid core-shell microspheres can provide electrostatic repulsion, which can stabilize the dispersion system and avoid agglomeration of the chitosan polylactic acid core-shell microspheres.

[0007] The object of the present application can be realized by the following technical solutions.

[0008] A preparation method of a surfactant containing tea saponin, comprising the following steps:

[0009] Step one: through the nucleophilic substitution reaction of the primary amino group in fluorinated hydroxy aniline and the ester group in polylactic acid microspheres, modified polylactic acid microspheres are obtained.

[0010] Step two: through the combination of the hydroxyl group in the modified polylactic acid microspheres and chlorosulfonic acid, sulfonic acid group / polylactic acid microspheres are obtained.

[0011] Step three: through the electrostatic interaction, chitosan is assembled on the surface of the sulfonic acid group / polylactic acid microspheres to obtain chitosan polylactic acid core-shell microspheres.

[0012] Step four: through the esterification reaction of the carboxyl group in tea saponin and the hydroxyl group on the surface of the chitosan polylactic acid core-shell microspheres, a surfactant containing tea saponin is obtained.

[0013] Further, the specific preparation steps of the modified polylactic acid microspheres are as follows:

[0014] The polylactic acid microspheres with a particle size of 50-60 μm, fluorinated hydroxy aniline and isopropyl alcohol are added to a reaction kettle, stirred at 50-60°C and 500-600 r / min for 1-2 h, filtered, and the filter cake is washed with deionized water for 2-4 times, vacuum dried at 60-70°C for 1-2 h to obtain modified polylactic acid microspheres.

[0015] Further, the amount ratio of the polylactic acid microspheres, fluorinated hydroxy aniline and isopropyl alcohol is 50-60 g:20-30 mL:500-600 mL.

[0016] Further, the specific preparation steps of the sulfonic acid group / polylactic acid microspheres are as follows:

[0017] The modified polylactic acid microspheres, dichloromethane and deionized water are added to a reaction kettle, stirred at 0-4°C and 500-600 r / min for 30-40 min, then chlorosulfonic acid is added, heated to 20-25°C, and continued to stir for 2-3 h, the generated chlorine is removed through a tail gas treatment device, the product is filtered, the filter cake is washed with methanol and deionized water for 2-4 times, and vacuum dried at 60-70°C for 1-2 h to obtain sulfonic acid group / polylactic acid microspheres.

[0018] Further, the amount ratio of the modified polylactic acid microspheres, dichloromethane, deionized water and chlorosulfonic acid is 20-30 g:90-100 mL:120-150 mL:5-6 g.

[0019] Further, the specific preparation steps of the chitosan polylactic acid core-shell microspheres are as follows:

[0020] The chitosan, the mass fraction of 30-40% acetic acid solution is added into the reaction kettle, and is stirred at 20-25 DEG C and 500-600r / min for 30-40min, then sodium hydroxide is added to adjust pH to 9-10, then sulfonic acid group / polylactic acid microspheres and dimethyl sulfoxide are added, and continue to stir for 3-4h, filter, and the filter cake is washed with PBS buffer and deionized water for 2-3 times, and is vacuum dried at 60-70 DEG C for 1-2h, to obtain chitosan polylactic acid core-shell microspheres.

[0021] Further, the amount ratio of chitosan, acetic acid solution, sodium hydroxide, sulfonic acid group / polylactic acid microspheres and dimethyl sulfoxide is 15-20g:80-90mL:0.3-0.5g:15-20g:80-90mL.

[0022] Further, the surfactant containing tea saponin is prepared according to the following steps:

[0023] The tea saponin and pyridine are added into the reaction kettle with water removal device, and are stirred at 20-25 DEG C and 500-600r / min for 30-40min, then chitosan polylactic acid core-shell microspheres, sodium fluoroborate and triethylamine are added, heated to 60-70 DEG C, and continue to stir for 16-18h, and the pyridine is removed by distillation under reduced pressure, and the concentrated solution is washed with deionized water for 2-3 times, centrifuged at 8000-9000r / min for 10-12min, filtered, and the filter cake is washed with deionized water and anhydrous ethanol for 2-3 times, and is vacuum dried at 60-80 DEG C for 1-2h, to obtain a surfactant containing tea saponin.

[0024] Further, the amount ratio of tea saponin, pyridine, chitosan polylactic acid core-shell microspheres, sodium fluoroborate and triethylamine is 80-90g:800-900mL:20-30g:0.5-0.7g:0.8-1g.

[0025] The application also provides the application of the surfactant containing tea saponin in pesticides.

[0026] The beneficial effects of the application are:

[0027] 1. The surfactant containing tea saponin prepared in the application has good long-acting insecticidal effect, is not easy to be washed away by rain, and has the effect of removing heavy metals in the soil.

[0028] 2.The tea saponin-containing surfactant of the present application, by esterification reaction, tea saponin is compounded with chitosan polylactic acid core-shell microspheres, and after fluorination treatment of the chitosan polylactic acid core-shell microspheres, the provided hydrophobicity can form a low surface energy layer, which can prevent water droplets from infiltrating, so that the liquid medicine can be more easily spread on the leaf surface, and it is not easy to be washed away by rainwater when sprayed on the surface of crops, the core-shell structure can buffer the impact force of raindrops, the elastic deformation of the shell layer dissipates the kinetic energy of water droplets, reduces the physical damage to the surface layer, and maintains long-term hydrophobicity; and the sulfonic acid group contained in the chitosan polylactic acid core-shell microspheres can provide electrostatic repulsion, which can stabilize the dispersion system and avoid the agglomeration of chitosan polylactic acid core-shell microspheres.

[0029] 3.In the tea saponin-containing surfactant of the present application, when tea saponin is sprayed on the leaf surface and soil of crops as a pesticide, it can chelate heavy metals in the soil, the amino groups and sulfonic acid groups on the surface of chitosan can enhance the chelation of heavy metals, and polylactic acid is easily decomposed by microorganisms in the soil into lactic acid, which can promote the dissolution of heavy metal carbonates.

[0030] 4.The raw materials of the tea saponin-containing surfactant of the present application all come from green and environmentally friendly materials, among which the degradation product lactic acid of polylactic acid can be metabolized by microorganisms into CO2 and H2O, chitosan can be decomposed by chitinase in the soil into glucosamine, and tea saponin can be hydrolyzed into glycoside, without the risk of secondary pollution. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] Embodiment 1: A preparation method of a tea saponin-containing surfactant, comprising the following steps:

[0033] S1: 50 g of polylactic acid microspheres with a particle size of 50-60 μm, 20 mL of fluorinated hydroxyaniline and 500 mL of isopropyl alcohol were added to a reaction kettle, stirred at 50 ℃ and 500 r / min for 1 h, filtered, and the filter cake was washed with deionized water for 2 times respectively, and vacuum dried at 60 ℃ for 1 h to obtain modified polylactic acid microspheres.

[0034] The ester group in the molecular chain of the polylactic acid microspheres undergoes nucleophilic substitution reaction with the primary amino group in the fluorinated hydroxyaniline to obtain modified polylactic acid microspheres.

[0035] S2: 20 g of modified polylactic acid microspheres, 90 mL of dichloromethane and 120 mL of deionized water were added to the reaction kettle, stirred at 0℃ and 500 r / min for 30 min, then 5 g of chlorosulfonic acid was added, heated to 20℃, and stirred for 2 h, the generated chlorine was removed by tail gas treatment device, the product was filtered, the filter cake was washed with methanol and deionized water for 2 times respectively, and vacuum dried at 60℃ for 1 h to obtain sulfonic acid group / poly lactic acid microspheres.

[0036] The hydroxyl group in the modified polylactic acid microspheres undergoes nucleophilic substitution reaction with chlorosulfonic acid to form sulfonate group, and then hydrolysis to obtain sulfonic acid group / poly lactic acid microspheres.

[0037] S3: 15 g of chitosan, 80 mL of 30% acetic acid solution were added to the reaction kettle, stirred at 20℃ and 500 r / min for 30 min, then 0.3 g of sodium hydroxide was added to adjust the pH value to 9, then 15 g of sulfonic acid group / poly lactic acid microspheres and 80 mL of dimethyl sulfoxide were added, and stirred for 3 h, filtered, the filter cake was washed with PBS buffer with pH value of 7 and deionized water for 2 times, and vacuum dried at 60℃ for 1 h to obtain chitosan polylactic acid core-shell microspheres.

[0038] The surface of the sulfonic acid group / poly lactic acid microspheres is rich in negatively charged sulfonic acid groups, which produces electrostatic interaction with positively charged chitosan, to obtain chitosan polylactic acid core-shell microspheres with sulfonic acid group / poly lactic acid microspheres as core and chitosan as shell.

[0039] S4: 80 g of tea saponin and 800 mL of pyridine with water removal device were added to the reaction kettle, stirred at 20℃ and 500 r / min for 30 min, then 20 g of chitosan polylactic acid core-shell microspheres, 0.5 g of sodium fluoroborate and 0.8 g of triethylamine were added, heated to 60℃, and stirred for 16 h, then the pyridine was removed by distillation under reduced pressure, the concentrated liquid was washed with deionized water for 2 times, centrifuged at 8000 r / min for 10 min, filtered, the filter cake was washed with deionized water and anhydrous ethanol for 2 times, and vacuum dried at 60℃ for 1 h to obtain a tea saponin-containing surfactant.

[0040] The carboxyl group in the tea saponin undergoes esterification reaction with the hydroxyl group contained in the chitosan in the chitosan polylactic acid core-shell microspheres structure to obtain a tea saponin-containing surfactant.

[0041] Example 2: A preparation method of a tea saponin-containing surfactant, comprising the following steps:

[0042] S1: 55 g of polylactic acid microspheres with a particle size of 50-60 μm, 25 mL of fluorinated hydroxyaniline, and 550 mL of isopropyl alcohol were added to a reaction kettle, stirred at 55°C and 550 r / min for 1.5 h, filtered, and the filter cake was washed with deionized water for 3 times, respectively, and vacuum dried at 65°C for 1.5 h to obtain modified polylactic acid microspheres.

[0043] S2: 25 g of modified polylactic acid microspheres, 95 mL of dichloromethane, and 135 mL of deionized water were added to a reaction kettle, stirred at 2°C and 550 r / min for 35 min, then 5.5 g of chlorosulfonic acid was added, heated to 22.5°C, and stirred for 2.5 h, the generated chlorine was removed by a tail gas treatment device, the product was filtered, the filter cake was washed with methanol and deionized water for 3 times, respectively, and vacuum dried at 65°C for 1.5 h to obtain sulfonic acid group / polylactic acid microspheres.

[0044] S3: 17.5 g of chitosan, 85 mL of 35% mass fraction acetic acid solution were added to a reaction kettle, stirred at 22.5°C and 550 r / min for 35 min, then 0.4 g of sodium hydroxide was added to adjust the pH value to 9.5, then 17.5 g of sulfonic acid group / polylactic acid microspheres and 85 mL of dimethyl sulfoxide were added, and the stirring was continued for 3.5 h, the filter cake was filtered, washed with PBS buffer with a pH value of 7.5 and deionized water for 2 times, and vacuum dried at 65°C for 1.5 h to obtain chitosan polylactic acid core-shell microspheres.

[0045] S4: 85 g of tea saponin and 850 mL of pyridine with a water removal device were added to a reaction kettle, stirred at 22.5°C and 550 r / min for 35 min, then 25 g of chitosan polylactic acid core-shell microspheres, 0.6 g of sodium fluoroborate, and 0.9 g of triethylamine were added, heated to 65°C, and stirred for 17 h, and the pyridine was removed by distillation under reduced pressure, the concentrated liquid was washed with deionized water for 2 times, centrifuged at 8500 r / min for 11 min, filtered, and the filter cake was washed with deionized water and anhydrous ethanol for 2 times, and vacuum dried at 70°C for 1.5 h to obtain a tea saponin-containing surfactant.

[0046] Example 3: A preparation method of a tea saponin-containing surfactant, comprising the following steps:

[0047] S1: 60 g of polylactic acid microspheres with a particle size of 50-60 μm, 30 mL of fluorinated hydroxyaniline, and 600 mL of isopropyl alcohol were added to a reaction kettle, stirred at 60°C and 600 r / min for 2 h, filtered, and the filter cake was washed with deionized water for 4 times, respectively, and vacuum dried at 70°C for 2 h to obtain modified polylactic acid microspheres.

[0048] S2: 30 g of modified polylactic acid microspheres, 100 mL of dichloromethane and 150 mL of deionized water were added to a reaction kettle, stirred at 4°C and 600 r / min for 40 min, then 6 g of chlorosulfonic acid was added, heated to 25°C, and stirred for 3 h, the generated chlorine was removed by a tail gas treatment device, the product was filtered, the filter cake was washed with methanol and deionized water for 4 times respectively, and vacuum dried at 70°C for 2 h to obtain sulfonic acid group / polylactic acid microspheres.

[0049] S3: 20 g of chitosan, 90 mL of 40% by mass acetic acid solution were added to a reaction kettle, stirred at 25°C and 600 r / min for 40 min, then 0.5 g of sodium hydroxide was added to adjust the pH value to 10, then 20 g of sulfonic acid group / polylactic acid microspheres and 90 mL of dimethyl sulfoxide were added, and stirred for 4 h, filtered, the filter cake was washed with PBS buffer with pH value of 8 and deionized water for 3 times, and vacuum dried at 70°C for 2 h to obtain chitosan polylactic acid core-shell microspheres.

[0050] S4: 90 g of tea saponin and 900 mL of pyridine with a water removal device were added to a reaction kettle, stirred at 25°C and 600 r / min for 40 min, then 30 g of chitosan polylactic acid core-shell microspheres, 0.7 g of sodium fluoroborate and 1 g of triethylamine were added, heated to 70°C, and stirred for 18 h, the pyridine was removed by distillation under reduced pressure, the concentrated liquid was washed with deionized water for 3 times, centrifuged at 9000 r / min for 12 min, filtered, the filter cake was washed with deionized water and anhydrous ethanol for 3 times, and vacuum dried at 80°C for 2 h to obtain a surfactant containing tea saponin.

[0051] Comparative Example 1: On the basis of Example 3, the fluorinated hydroxy aniline in step S1 was replaced by hydroxy aniline, and the remaining steps were unchanged, to prepare a surfactant containing tea saponin.

[0052] Comparative Example 2: On the basis of Example 3, without step S2 treatment, the sulfonic acid group / polylactic acid microspheres in step S3 were replaced by the modified polylactic acid microspheres prepared in step S1, and the remaining steps were unchanged, to prepare a surfactant containing tea saponin.

[0053] Comparative Example 3: On the basis of Example 3, without step S4 treatment, the tea saponin and sulfonic acid group / polylactic acid microspheres in step S4 were mixed according to a mass ratio of 3:1 to prepare a surfactant containing tea saponin.

[0054] The surfactants containing tea saponin prepared in Example 1-Example 3 and Comparative Example 1-Comparative Example 3 were tested for performance, 1.8 g of the surfactant containing tea saponin, 1 g of safflower extract and 96 g of a solution containing 10 wt% of ethyl acetate were mixed uniformly, then 1.1 g of C8-C10 fatty alcohol polyoxyethylene ether was added and mixed uniformly to obtain a pesticide preparation.

[0055] 1. Put 30 tea caterpillars in a culture dish, and put 15 tea tree sprout leaves, use point drop method, use micro drop to drop pesticide preparation on the back of tea caterpillars, observe the activity and feeding of tea caterpillars after using pesticide, count the number of deaths at 24h, 48h and 72h, and calculate the corrected mortality rate.

[0056] 2. Leaf surface contact angle test: the contact angle of the pesticide preparation on the tea tree sprout leaf is measured by an optical contact angle meter, fresh leaves of the same thickness and size are fixed on a glass slide for experiment, 5mL of pesticide preparation is sprayed on the tea tree sprout leaf at room temperature, when the droplet is stable, the contact angle value is recorded, each sample is measured at least 5 times at different positions, and the average value is taken.

[0057] 3. Select tea tree sprout leaves, dry at 60℃ to constant weight, spray 5mL of pesticide preparation, stand for 30min, weigh, use a rainfall simulator (rain intensity 50mm / h, time 30min) to flush the tea tree sprout leaves, quickly absorb the surface moisture after flushing, dry at 60℃, record the initial weight, and calculate the rainwater residual rate.

[0058] 4. Collect 4cm deep soil, dry naturally, grind through 1mm sieve, take 1.00g of soil sample and put it in a 100mL centrifuge tube, add 25mL of pesticide preparation, constant temperature oscillation, centrifuge at 4000r / min for 5min, collect the supernatant by filtration, measure the Cd 2+ concentration in the filtrate by atomic absorption spectrometry, and calculate the Cd 2+ removal rate.

[0059] The results are shown in Table 1:

[0060] Table 1 Performance test results of pesticide preparation

[0061] Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 24h Ectropis oblique death rate (%) 36.25 37.35 22.10 28.87 26.42 30.12 48h Ectropis oblique death rate (%) 53.21 54.60 55.80 46.21 43.35 48.56 72h Ectropis oblique death rate (%) 69.32 70.50 72.10 60.61 55.24 65.32 Ectropis oblique activity after treatment Significantly reduced Significantly reduced Significantly reduced Slightly reduced Partially reduced No change Ectropis oblique feeding behavior after treatment Significantly reduced Significantly reduced Significantly reduced Slightly reduced Slightly reduced No change Contact angle (°) 61.5 60.2 59.8 80.2 78.5 62.6 Rainwater residue rate (%) 82.2 83.6 84.9 60.2 65.2 50.2 Cd 2+ Removal (%)]] 92.2 93.2 94.2 90.8 82.1 90.2

[0062] As can be seen from Table 1, the pesticide preparation prepared from the tea saponin-containing surfactant prepared in Examples 1-5 has significantly better 24h, 48h and 72h mortality rate of tea caterpillars, activity and feeding of tea caterpillars after using pesticide than the comparative examples, and has significantly better rainwater residual rate and Cd 2+ removal rate than the comparative examples, and has significantly lower contact angle than the comparative examples, indicating that the tea saponin-containing surfactant prepared in the application has good long-acting insecticidal effect after being prepared into pesticide, is not easy to be washed away by rainwater, and has the effect of removing heavy metals in soil.

[0063] The fluorinated hydroxy aniline in step S1 is replaced by hydroxy aniline in Comparative Example 1, which does not contain fluorocarbon chain and cannot form a low surface energy layer, has poor leaf spreading property, and the pesticide solution is easy to gather into drops, and the anti-washing property is reduced. Because of the lack of hydrophobic barrier of fluorocarbon chain, water droplets are more likely to penetrate and wash, the pesticide release is ineffective, the unfluorinated microspheres have strong hydrophilicity, the release rate of tea saponin is accelerated, and the killing rate of tea shoot moth is reduced.

[0064] The sulfonic acid group / polylactic acid microspheres in step S3 are replaced by modified polylactic acid microspheres in Comparative Example 2. The sulfonic acid group provides electrostatic repulsion, and its absence leads to microsphere agglomeration. The agglomerated microspheres are difficult to penetrate into the hidden parts eaten by tea shoot moth, the tea saponin is unevenly distributed, the sulfonic acid group cooperates with the chitosan amino group to chelate heavy metals, and after the loss of sulfonic acid group, the overall performance is significantly reduced.

[0065] The tea saponin and sulfonic acid group / polylactic acid microspheres in step S4 are mixed in a mass ratio of 3:1 in Comparative Example 3. Physical mixing causes tea saponin to be adsorbed on the surface of the microspheres rather than covalently bonded, which is easily washed away by rain, resulting in a decrease in long-acting property.

[0066] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the present application.

Claims

1. A method for preparing a surfactant containing tea saponin, characterized in that, Includes the following steps: Step 1: Modified polylactic acid microspheres are obtained by nucleophilic substitution reaction between the primary amino group in fluorinated hydroxyaniline and the ester group in polylactic acid microspheres; Step 2: By combining the hydroxyl groups in the modified polylactic acid microspheres with chlorosulfonic acid, sulfonic acid-based / polylactic acid microspheres are obtained; Step 3: Chitosan is assembled on the surface of sulfonic acid / polylactic acid microspheres through electrostatic interaction to obtain chitosan-polylactic acid core-shell microspheres; Step 4: The carboxyl groups in tea saponin undergo an esterification reaction with the hydroxyl groups on the surface of chitosan polylactic acid core-shell microspheres to obtain a surfactant containing tea saponin.

2. The method for preparing a surfactant containing tea saponin according to claim 1, characterized in that, The specific preparation steps for the modified polylactic acid microspheres are as follows: Polylactic acid microspheres with a particle size of 50-60 μm, fluorinated hydroxyaniline and isopropanol were added to a reaction vessel and stirred for 1-2 h at 50-60 °C and 500-600 r / min. After filtration, the filter cake was washed 2-4 times with deionized water and dried under vacuum at 60-70 °C for 1-2 h to obtain modified polylactic acid microspheres.

3. The method for preparing a surfactant containing tea saponin according to claim 2, characterized in that, The ratio of polylactic acid microspheres, fluorinated hydroxyaniline, and isopropanol is 50-60g: 20-30mL: 500-600mL.

4. The method for preparing a surfactant containing tea saponin according to claim 1, characterized in that, The specific preparation steps for the sulfonic acid-based / polylactic acid microspheres are as follows: Modified polylactic acid microspheres, dichloromethane, and deionized water were added to a reaction vessel and stirred at 0-4℃ and 500-600 r / min for 30-40 min. Then, chlorosulfonic acid was added, and the mixture was heated to 20-25℃ and stirred for 2-3 h. The mixture was then filtered, washed, and vacuum dried to obtain sulfonic acid-based / polylactic acid microspheres.

5. The method for preparing a surfactant containing tea saponin according to claim 4, characterized in that, The ratio of the modified polylactic acid microspheres, dichloromethane, deionized water, and chlorosulfonic acid is 20-30g: 90-100mL: 120-150mL: 5-6g.

6. The method for preparing a surfactant containing tea saponin according to claim 1, characterized in that, The specific preparation steps for the chitosan-polylactic acid core-shell microspheres are as follows: Chitosan and 30-40 wt% acetic acid solution were added to a reaction vessel and stirred at 20-25℃ and 500-600 r / min for 30-40 min. Then sodium hydroxide was added to adjust the pH to 9-10. Sulfonic acid group / polylactic acid microspheres and dimethyl sulfoxide were added and stirred for 3-4 h. The mixture was then filtered, washed, and vacuum dried for 1-2 h to obtain chitosan-polylactic acid core-shell microspheres.

7. The method for preparing a surfactant containing tea saponin according to claim 6, characterized in that, The ratio of chitosan, acetic acid solution, sodium hydroxide, sulfonic acid / polylactic acid microspheres and dimethyl sulfoxide is 15-20g: 80-90mL: 0.3-0.5g: 15-20g: 80-90mL.

8. The method for preparing a surfactant containing tea saponin according to claim 1, characterized in that, The specific preparation steps of the surfactant containing tea saponin are as follows: Add tea saponin and pyridine to a reaction vessel, stir at 20-25℃ and 500-600 r / min for 30-40 min, then add chitosan polylactic acid core-shell microspheres, sodium fluoroborate and triethylamine, heat to 60-70℃, continue stirring for 16-18 h, remove pyridine by vacuum distillation, wash the concentrated solution 2-3 times with deionized water, centrifuge at 8000-9000 r / min for 10-12 min, filter, wash, and vacuum dry to obtain a surfactant containing tea saponin.

9. The method for preparing a surfactant containing tea saponin according to claim 8, characterized in that, The ratio of tea saponin, pyridine, chitosan polylactic acid core-shell microspheres, sodium fluoroborate and triethylamine is 80-90g: 800-900mL: 20-30g: 0.5-0.7g: 0.8-1g.

10. The application of a surfactant containing tea saponin in pesticides, characterized in that, The surfactant containing tea saponin is prepared by any one of the preparation methods according to claims 1-9.