Modified polyglutamic acid for pesticide suspending agent and preparation method of modified polyglutamic acid

Abstract

The invention relates to the technical field of pesticide preparation, in particular to modified polyglutamic acid for a pesticide suspending agent and a preparation method thereof.The modified polyglutamic acid is prepared from a microcapsule A, a microcapsule B and a particle additive, and the microcapsule A is prepared from chitosan, gamma-polyglutamic acid and abamectin; the microcapsule B is prepared from gamma-polyglutamic acid, polyvinyl alcohol, nano silicon dioxide and abamectin; the particle additive is prepared from modified polyglutamic acid, sodium dodecyl benzene sulfonate, abamectin and carboxymethyl cellulose; the microcapsule A and the microcapsule B play a slow release role, the action time is prolonged while the pesticide suspending agent can take effect as soon as possible, the particle additive can increase repulsive force among particles and prevent flocculation and aggregation among the particles, the microcapsule A, the microcapsule B and the particle additive are synergistically promoted to jointly improve the performance of the pesticide suspending agent, and the microcapsule has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of pesticide preparation, in particular to a modified polyglutamic acid for pesticide suspension and a preparation method thereof. Background Art

[0002] γ-Polyglutamic acid is an anionic polymer carrier material produced by microbial fermentation. It has a large number of free side chain carboxyl groups, which can undergo chelation, cross-linking and derivatization reactions. It is easy to modify and can form a stable complex with drugs to release drugs slowly and reduce the amount of drugs used. It also has strong water solubility and adhesion, is easily degraded by microorganisms, and is environmentally friendly. Since there are a large number of free carboxyl groups on the γ-Polyglutamic acid molecular chain, the γ-Polyglutamic acid molecule has a large number of active sites that are easy to modify and can react with the active groups of cross-linking agents or other substances. In recent years, γ-polyglutamic acid has been produced on a large scale and the production technology has become increasingly mature. The excellent properties of γ-polyglutamic acid, such as easy availability of raw materials, low toxicity and easy decomposition, have also brought huge environmental and economic benefits and have been widely used in various fields. γ-polyglutamic acid can increase the effective water content of the soil and reduce the invalid water or excess water content. Its water extract has a certain water retention capacity in the soil and has drought resistance and seedling promotion effects. Therefore, it is often used as a water retaining agent. γ-polyglutamic acid has the ability to enhance the absorption capacity of crops for nutrients, thereby effectively improving the utilization rate of nutrients and achieving the purpose of increasing production and improving quality. Therefore, it is often used as a fertilizer enhancer.

[0003] Pesticide suspension is a kind of dosage form prepared by adding a certain amount of dispersant, thickener, wetting agent, etc. to the original drug. The advantage of suspension is that it uses water as the dispersion medium, so the preparation cost of suspension is low, and it can be mixed with water in any proportion, and will not be affected by water quality and water temperature, which is convenient for use in actual agricultural production. Compared with preparations using organic solvents as dispersion media, suspension has the characteristics of less impact on environmental pollution and low pesticide damage to crops. However, most of the surfactants used in the preparation of suspension are selected from emulsifiers, so the performance of suspension is not fully suitable for suspension requirements. In addition, these products are generally less stable, and often have phenomena such as stratification, precipitation, flocculation and agglomeration.

[0004] Patent technology document CN114586792A discloses a nano suspension containing benzovinflumizone and its preparation method and application, belonging to the field of pesticide preparation technology. The suspension is formed by coating or adsorbing benzovinflumizone with nanoparticles formed by γ-polyglutamic acid, chitosan and sodium tripolyphosphate, and then adding an auxiliary agent to mix. However, the prepared suspension has poor dispersibility and poor sustained release effect.

[0005] Therefore, according to the above-mentioned related technologies, it is urgent to develop a modified polyglutamic acid for pesticide suspension and a preparation method thereof. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a modified polyglutamic acid for pesticide suspension and a preparation method thereof, so as to solve the problem of poor sustained-release effect of suspension in the prior art.

[0007] Based on the above purpose, the present invention provides a modified polyglutamic acid for pesticide suspension and a preparation method thereof.

[0008] A modified polyglutamic acid for pesticide suspension and a preparation method thereof, comprising the following raw materials in parts by weight: 20-25 parts of microcapsules A, 42-48 parts of microcapsules B, and 10-13 parts of microparticle additives;

[0009] The microcapsule A is prepared from chitosan, γ-polyglutamic acid and avermectin;

[0010] The microcapsule B is prepared from γ-polyglutamic acid, polyvinyl alcohol, nano-silicon dioxide and avermectin;

[0011] The microparticle auxiliary agent is prepared from modified polyglutamic acid, sodium dodecylbenzene sulfonate, avermectin and carboxymethyl cellulose;

[0012] The modified polyglutamic acid is prepared from γ-polyglutamic acid, polyvinyl alcohol and nano-silicon dioxide;

[0013] The particle size of the microcapsule A is 2-4 mm;

[0014] The particle size of the microcapsule B is 5-8 mm;

[0015] The particle size of the microparticle auxiliary agent is 1-2 mm.

[0016] Preferably, the preparation method of the microcapsule A is as follows:

[0017] Step A1: dissolving avermectin in dichloromethane, adding γ-polyglutamic acid and stirring, and adding the mixture into palm oil to obtain a combined solution A;

[0018] Step A2: Add the γ-polyglutamic acid solution dropwise to the chitosan solution, add sodium dodecylbenzene sulfonate and avermectin, stir at 45-55°C for 1.5-3h, then cool to room temperature, add the combined liquid A dropwise thereto, stir for 25-35min, then add the sodium tripolyphosphate solution thereto, stir at room temperature for 1-3h, centrifuge at 7000-8000r / min for 8-10min, wash, freeze-dry, crush and sieve to obtain microcapsules A.

[0019] Preferably, the usage ratio of avermectin, dichloromethane, γ-polyglutamic acid and palm oil in step A1 is 3-5 g: 4-6 mL: 10-12 g: 15-18 mL.

[0020] Preferably, the dosage ratio of the γ-polyglutamic acid solution, chitosan solution, sodium dodecylbenzene sulfonate, avermectin, combined solution A and sodium tripolyphosphate solution in step A2 is 25-28 mL: 25-28 mL: 1-3 g: 3-5 g: 30-32 mL: 45-50 mL;

[0021] The γ-polyglutamic acid solution in step A2 is obtained by mixing γ-polyglutamic acid and water at a mass ratio of 10-12:400-450;

[0022] The chitosan solution in step A2 is obtained by mixing chitosan, acetic acid and water in a mass ratio of 3-5:15-18:400-450;

[0023] The sodium tripolyphosphate solution in step A2 is obtained by mixing sodium tripolyphosphate and water in a mass ratio of 0.8-1.2:8-10.

[0024] Preferably, the preparation method of the microcapsule B is as follows:

[0025] Step B1: dissolving avermectin in dichloromethane, and adding the mixture into palm oil to obtain a combined liquid B;

[0026] Step B2: deionized water and polyvinyl alcohol are added to a three-necked flask equipped with an electric stirrer and a condenser, and the mixture is kept at 60-70°C for 2-5 hours until the mixture is completely dissolved, and the mixture is cooled to 50°C, and γ-polyglutamic acid and glutaraldehyde are added to react for 2-4 hours, and nano-silicon dioxide and anhydrous ethanol are added thereto, and the mixture is stirred evenly, and ultrasonic dispersion treatment is performed for 1-3 hours and the bubbles are removed to obtain modified polyglutamic acid;

[0027] Step B3: Add the combined solution B dropwise into the modified polyglutamic acid, stir at room temperature for 1-3 hours, centrifuge at 7000-8000 r / min for 8-10 minutes, wash, freeze-dry, crush and sieve to obtain microcapsules B.

[0028] Preferably, the mass ratio of avermectin, dichloromethane and palm oil in step B1 is 8-10 g: 4-6 mL: 15-18 mL.

[0029] Preferably, the usage ratio of deionized water, polyvinyl alcohol, γ-polyglutamic acid, glutaraldehyde, nano-silicon dioxide and anhydrous ethanol in step B2 is 460-480 mL: 18-22 g: 6-10 g: 1-3 mL: 18-22 g: 5-8 mL;

[0030] The mass ratio of the combined solution B and the modified polyglutamic acid in step B3 is 45-48:25-28.

[0031] Preferably, the preparation method of the microparticle auxiliary agent is as follows:

[0032] Disperse modified polyglutamic acid, sodium dodecylbenzene sulfonate, avermectin and carboxymethyl cellulose in water, stir at 50-60°C for 1-3 hours, centrifuge at 7000-8000 r / min for 5-8 minutes, dry at 70-80°C, crush and sieve to obtain a microparticle additive.

[0033] Preferably, the mass ratio of the modified polyglutamic acid, sodium dodecylbenzene sulfonate, avermectin, carboxymethyl cellulose and water is 8-10: 1-3: 0.2-0.5: 1-3: 100-200.

[0034] A method for preparing modified polyglutamic acid for pesticide suspension, the method for preparing modified polyglutamic acid for pesticide suspension is as follows:

[0035] The microcapsule A, microcapsule B and microparticle auxiliary agent are uniformly mixed to obtain modified polyglutamic acid for pesticide suspension.

[0036] Beneficial effects of the present invention:

[0037] The invention provides a modified polyglutamic acid for pesticide suspension and a preparation method thereof. The microcapsule A prepared by the invention is made of avermectin and γ-polyglutamic acid as core materials, and the outer layer is coated with chitosan and γ-polyglutamic acid. The γ-polyglutamic acid has the ability to enhance nutrient absorption and can be used as a fertilizer synergist. Chitosan has amino and hydroxyl groups with high activity and can react with γ-polyglutamic acid through covalent and ionic crosslinking, thereby improving its dispersibility in the pesticide suspension. The inner layer and the outer layer of the microcapsule A are both coated with avermectin, which not only ensures that the pesticide suspension can take effect as soon as possible, but also prolongs the action time.

[0038] The microcapsule B provided by the present invention uses avermectin as the core material, and the outer layer is coated with nano-silicon dioxide, γ-polyglutamic acid and polyvinyl alcohol. The polyvinyl alcohol and γ-polyglutamic acid are physically cross-linked to improve the sustained-release performance of the pesticide suspension. The nano-silicon dioxide particles are small and have a large specific surface area. The cross-linking agent pentanediol promotes the cross-linking of the nano-silicon dioxide and the polyvinyl alcohol, thereby improving the sustained-release performance.

[0039] The microparticle additive provided by the present invention contains the active ingredients of the pesticide suspension. When dissolved in water, the active ingredients can be quickly dispersed in the water, so as to achieve the purpose of taking effect as soon as possible. At the same time, the microparticle additive can also increase the repulsion between particles, prevent flocculation and aggregation between particles, thereby maintaining the uniform dispersion of the active ingredients of the pesticide, while microcapsules A and microcapsules B play a sustained release role. The three promote synergistically and jointly improve the performance of the pesticide suspension, and have broad application prospects. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0041] The sources and properties of some of the raw materials used in the present invention are as follows:

[0042] γ-Polyglutamic acid was purchased from Zhengzhou Best Food Additive Co., Ltd.; chitosan was purchased from Shandong Haiyihua Biotechnology Co., Ltd.; sodium dodecylbenzenesulfonate was purchased from Nantong Runfeng Petrochemical Co., Ltd.; avermectin was purchased from Hebei Mojin Biotechnology Co., Ltd.; carboxymethyl cellulose was purchased from Jiangsu Weizhirun Biotechnology Co., Ltd.

[0043] Embodiment 1: A method for preparing modified polyglutamic acid for pesticide suspension, comprising the following steps:

[0044] S1: 3 g of avermectin was dissolved in 4 mL of dichloromethane, 10 g of γ-polyglutamic acid was added and stirred, and then the mixture was added into 15 mL of palm oil to obtain a combined solution A;

[0045] S2: 25 mL of γ-polyglutamic acid solution was added dropwise to 25 mL of chitosan solution, 1 g of sodium dodecylbenzene sulfonate and 3 g of avermectin were added, the mixture was stirred at 45°C for 1.5 h and then cooled to room temperature, 30 mL of combined liquid A was added dropwise thereto and stirred for 25 min, and then 45 mL of sodium tripolyphosphate solution was added thereto, the mixture was stirred at room temperature for 1 h, centrifuged at 7000 r / min for 8 min, and then freeze-dried after washing, and the mixture was crushed and sieved to obtain microcapsules A, wherein the particle size of microcapsules A was 2 mm, the γ-polyglutamic acid solution was obtained by mixing 10 g of γ-polyglutamic acid with 400 g of water, the chitosan solution was obtained by mixing 3 g of chitosan, 15 g of acetic acid with 400 g of water, and the sodium tripolyphosphate solution was obtained by mixing 0.8 g of sodium tripolyphosphate with 8 g of water.

[0046] S3: 8 g of avermectin was dissolved in 4 mL of dichloromethane and added to 15 mL of palm oil to obtain a combined solution B;

[0047] S4: 460 mL of deionized water and 18 g of polyvinyl alcohol were added to a three-necked flask equipped with an electric stirrer and a condenser, and the mixture was kept at 60°C for 2 h until it was completely dissolved, and then the temperature was lowered to 50°C, and 6 g of γ-polyglutamic acid and 1 mL of glutaraldehyde were added to react for 2 h, and then 18 g of nano-silicon dioxide and 5 mL of anhydrous ethanol were added thereto, and the mixture was stirred evenly, and ultrasonic dispersion treatment was performed for 1 h and the bubbles were removed to obtain modified polyglutamic acid;

[0048] S5: 45 g of the combined solution B was added dropwise to 25 g of modified polyglutamic acid, stirred at room temperature for 1 h, centrifuged at 7000 r / min for 8 min, washed, freeze-dried, crushed and sieved to obtain microcapsules B, wherein the particle size of the microcapsules B was 5 mm;

[0049] S6: 8 g of modified polyglutamic acid, 1 g of sodium dodecylbenzene sulfonate, 0.2 g of avermectin and 1 g of carboxymethyl cellulose were dispersed in 100 g of water, stirred at 50° C. for 1 h, centrifuged at 7000 r / min for 5 min, dried at 70° C., crushed and sieved to obtain a particulate additive, wherein the particle size of the particulate additive was 1 mm;

[0050] S7: 20 g of microcapsule A, 42 g of microcapsule B and 10 g of microparticle auxiliary agent were mixed evenly to obtain modified polyglutamic acid for pesticide suspension.

[0051] Embodiment 2: A method for preparing modified polyglutamic acid for pesticide suspension, comprising the following steps:

[0052] S1: 3.5 g of avermectin was dissolved in 4.5 mL of dichloromethane, 10.5 g of γ-polyglutamic acid was added and stirred, and then the mixture was added into 16 mL of palm oil to obtain a combined solution A;

[0053] S2: 26 mL of γ-polyglutamic acid solution was added dropwise to 26 mL of chitosan solution, 1.5 g of sodium dodecylbenzene sulfonate and 3.5 g of avermectin were added, the mixture was stirred at 48°C for 2 h and then cooled to room temperature, 30.5 mL of combined liquid A was added dropwise thereto and stirred for 28 min, and then 48 mL of sodium tripolyphosphate solution was added thereto, the mixture was stirred at room temperature for 1.5 h, centrifuged at 7200 r / min for 8.5 min, and then freeze-dried after washing, and crushed and sieved to obtain microcapsule A, wherein the particle size of microcapsule A is 3 mm, wherein the γ-polyglutamic acid solution is obtained by mixing 10.5 g of γ-polyglutamic acid with 420 g of water, the chitosan solution is obtained by mixing 3.5 g of chitosan, 16 g of acetic acid with 420 g of water, and the sodium tripolyphosphate solution is obtained by mixing 0.9 g of sodium tripolyphosphate with 8.5 g of water.

[0054] S3: 8.5 g of avermectin was dissolved in 4.5 mL of dichloromethane and added to 16 mL of palm oil to obtain a combined solution B;

[0055] S4: 465 mL of deionized water and 19 g of polyvinyl alcohol were added to a three-necked flask equipped with an electric stirrer and a condenser, and the mixture was kept at 62°C for 3 h until it was completely dissolved, and then the temperature was lowered to 50°C, 7 g of γ-polyglutamic acid and 1.5 mL of glutaraldehyde were added to react for 2.5 h, and then 19 g of nano-silicon dioxide and 6 mL of anhydrous ethanol were added thereto, and the mixture was stirred evenly, and ultrasonic dispersion treatment was performed for 1.5 h and the bubbles were removed to obtain modified polyglutamic acid;

[0056] S5: 46 g of the combined solution B was added dropwise to 26 g of modified polyglutamic acid, stirred at room temperature for 1.5 h, centrifuged at 7200 r / min for 8.5 min, washed, freeze-dried, crushed and sieved to obtain microcapsules B, wherein the particle size of the microcapsules B was 6 mm;

[0057] S6: 8.5 g of modified polyglutamic acid, 1.5 g of sodium dodecylbenzene sulfonate, 0.3 g of avermectin and 1.5 g of carboxymethyl cellulose were dispersed in 120 g of water, stirred at 52° C. for 1.5 h, centrifuged at 7200 r / min for 6 min, dried at 72° C., crushed and sieved to obtain a particulate additive, wherein the particle size of the particulate additive was 2 mm;

[0058] S7: 22 g of microcapsule A, 44 g of microcapsule B and 11 g of microparticle additive were mixed evenly to obtain modified polyglutamic acid for pesticide suspension.

[0059] Embodiment 3: A method for preparing modified polyglutamic acid for pesticide suspension, comprising the following steps:

[0060] S1: 4 g of avermectin was dissolved in 5 mL of dichloromethane, 11 g of γ-polyglutamic acid was added and stirred, and then the mixture was added into 17 mL of palm oil to obtain a combined solution A;

[0061] S2: 25-28 mL of γ-polyglutamic acid solution was added dropwise to 27 mL of chitosan solution, 2 g of sodium dodecylbenzene sulfonate and 4 g of avermectin were added, the mixture was stirred at 52°C for 2.5 h and then cooled to room temperature, 31 mL of combined liquid A was added dropwise thereto and stirred for 32 min, and then 48 mL of sodium tripolyphosphate solution was added thereto, the mixture was stirred at room temperature for 2 h, centrifuged at 7800 r / min for 9 min, washed and freeze-dried, and then crushed and sieved to obtain microcapsule A, wherein the particle size of microcapsule A was 3 mm, the γ-polyglutamic acid solution was obtained by mixing 11 g of γ-polyglutamic acid with 440 g of water, the chitosan solution was obtained by mixing 4 g of chitosan, 17 g of acetic acid and 440 g of water, and the sodium tripolyphosphate solution was obtained by mixing 1 g of sodium tripolyphosphate with 9 g of water.

[0062] S3: 9 g of avermectin was dissolved in 5 mL of dichloromethane and added to 17 mL of palm oil to obtain a combined solution B;

[0063] S4: 470 mL of deionized water and 20 g of polyvinyl alcohol were added to a three-necked flask equipped with an electric stirrer and a condenser, and the mixture was kept at 68°C for 4 h until it was completely dissolved, and then the temperature was lowered to 50°C, 9 g of γ-polyglutamic acid and 2 mL of glutaraldehyde were added to react for 3 h, and then 20 g of nano-silicon dioxide and 7 mL of anhydrous ethanol were added thereto, and the mixture was stirred evenly, and ultrasonic dispersion treatment was performed for 2 h and the bubbles were removed to obtain modified polyglutamic acid;

[0064] S5: 47 g of the combined solution B was added dropwise to 27 g of modified polyglutamic acid, stirred at room temperature for 2 h, centrifuged at 7800 r / min for 9 min, washed, freeze-dried, crushed and sieved to obtain microcapsules B, wherein the particle size of the microcapsules B was 7 mm;

[0065] S6: 9 g of modified polyglutamic acid, 2 g of sodium dodecylbenzene sulfonate, 0.4 g of avermectin and 2 g of carboxymethyl cellulose were dispersed in 180 g of water, stirred at 58° C. for 2 h, centrifuged at 7800 r / min for 7 min, dried at 78° C., crushed and sieved to obtain a particulate additive, wherein the particle size of the particulate additive was 2 mm;

[0066] S7: 24 g of microcapsule A, 46 g of microcapsule B and 12 g of microparticle auxiliary agent were mixed evenly to obtain modified polyglutamic acid for pesticide suspension.

[0067] Embodiment 4: A method for preparing modified polyglutamic acid for pesticide suspension, comprising the following steps:

[0068] S1: 5 g of avermectin was dissolved in 6 mL of dichloromethane, 12 g of γ-polyglutamic acid was added and stirred, and then the mixture was added into 18 mL of palm oil to obtain a combined solution A;

[0069] S2: 28 mL of γ-polyglutamic acid solution was added dropwise to 28 mL of chitosan solution, 3 g of sodium dodecylbenzene sulfonate and 5 g of avermectin were added, the mixture was stirred at 55° C. for 3 h and then cooled to room temperature, 32 mL of combined liquid A was added dropwise thereto and stirred for 35 min, and then 50 mL of sodium tripolyphosphate solution was added thereto, the mixture was stirred at room temperature for 3 h, centrifuged at 8000 r / min for 10 min, washed and freeze-dried, and then crushed and sieved to obtain microcapsule A, wherein the particle size of microcapsule A was 4 mm, the γ-polyglutamic acid solution was obtained by mixing 12 g of γ-polyglutamic acid with 450 g of water, the chitosan solution was obtained by mixing 5 g of chitosan, 18 g of acetic acid and 450 g of water, and the sodium tripolyphosphate solution was obtained by mixing 1.2 g of sodium tripolyphosphate with 10 g of water.

[0070] S3: Dissolve 10 g of avermectin in 6 mL of dichloromethane and add to 18 mL of palm oil to obtain a combined solution B;

[0071] S4: 480 mL of deionized water and 22 g of polyvinyl alcohol were added to a three-necked flask equipped with an electric stirrer and a condenser, and the mixture was kept at 70°C for 5 h until it was completely dissolved, and then the temperature was lowered to 50°C, 10 g of γ-polyglutamic acid and 3 mL of glutaraldehyde were added to react for 4 h, and then 22 g of nano-silicon dioxide and 8 mL of anhydrous ethanol were added thereto, and the mixture was stirred evenly, and ultrasonic dispersion treatment was performed for 3 h and the bubbles were removed to obtain modified polyglutamic acid;

[0072] S5: 48 g of the combined solution B was added dropwise to 28 g of modified polyglutamic acid, stirred at room temperature for 3 h, centrifuged at 8000 r / min for 10 min, washed, freeze-dried, crushed and sieved to obtain microcapsules B, wherein the particle size of the microcapsules B was 8 mm;

[0073] S6: 10 g of modified polyglutamic acid, 3 g of sodium dodecylbenzene sulfonate, 0.5 g of avermectin and 3 g of carboxymethyl cellulose were dispersed in 200 g of water, stirred at 60° C. for 3 h, centrifuged at 8000 r / min for 8 min, dried at 80° C., crushed and sieved to obtain a particulate additive, wherein the particle size of the particulate additive was 3 mm;

[0074] S7: 25 g of microcapsule A, 48 g of microcapsule B and 13 g of microparticle auxiliary agent were mixed evenly to obtain modified polyglutamic acid for pesticide suspension.

[0075] Comparative Example 1:

[0076] Compared with Example 1, this comparative example does not add particulate additives during the preparation of modified polyglutamic acid for pesticide suspension, and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, modified polyglutamic acid for pesticide suspension is obtained.

[0077] Comparative Example 2:

[0078] Compared with Example 1, this comparative example only replaces "modified polyglutamic acid" with "γ-polyglutamic acid" in the preparation process of the microparticle auxiliary agent, and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally modified polyglutamic acid for pesticide suspension is obtained.

[0079] Comparative Example 3:

[0080] Compared with Example 1, this comparative example only replaces "the particle size of microcapsule A is 2 mm, and the particle size of microcapsule B is 5 mm" with "the particle size of microcapsule A is 5 mm, and the particle size of microcapsule B is 2 mm", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally modified polyglutamic acid for pesticide suspension is obtained.

[0081] Comparative Example 4:

[0082] Compared with Example 1, this comparative example only replaces "20g microcapsule A, 42g microcapsule B" with "42g microcapsule A, 20g microcapsule B", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally modified polyglutamic acid for pesticide suspension is obtained.

[0083] Comparative Example 5:

[0084] Compared with Example 1, this comparative example does not add γ-polyglutamic acid during the preparation of the combined liquid A, and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, modified polyglutamic acid for pesticide suspension is obtained.

[0085] Comparative Example 6:

[0086] Compared with Example 1, chitosan was not added in the preparation process of microcapsule A in this comparative example, and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, modified polyglutamic acid for pesticide suspension was obtained.

[0087] Comparative Example 7:

[0088] Compared with Example 1, in this comparative example, nano-silicon dioxide was not added during the preparation of microcapsule B, and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, modified polyglutamic acid for pesticide suspension was obtained.

[0089] Comparative Example 8:

[0090] Compared with Example 1, glutaraldehyde was not added in the preparation process of microcapsule B in this comparative example, and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, modified polyglutamic acid for pesticide suspension was obtained.

[0091] Comparative Example 9:

[0092] Compared with Example 1, polyvinyl alcohol was not added in the preparation process of microcapsule B in this comparative example, and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, modified polyglutamic acid for pesticide suspension was obtained.

[0093] Performance Test:

[0094] Sustained release performance test:

[0095] The release capacity of the modified polyglutamic acid for pesticide suspension prepared in Examples 1 to 4 and Comparative Examples 1 to 9 was determined by the dialysis bag method. A dialysis bag with a specification of 1000Da was cut into small sections of 10cm, placed in a beaker filled with deionized water and boiled for 30min. After cooling, it was rinsed with deionized water several times. After 10mg of the modified polyglutamic acid for pesticide suspension prepared in Examples 1 to 4 and Comparative Examples 1 to 9 was added to 10mL of water to make a suspension, the dialysis bag was added, and it was placed in a beaker filled with 100mL of deionized water. After 10h, 40h, and 70h, 1mL of the solution was taken out, and 1mL of deionized water was added to the release system. The content of the active ingredient in the taken out solution was measured under a UV spectrophotometer at a wavelength of 245nm, and the cumulative release rate of the pesticide was calculated. At the same time, a control test was set up, and the cumulative release rate of the pesticide was tested for 10h, 40h, and 70h under the same conditions for a single dose of avermectin. The measured results were: the cumulative release rate of the pesticide was 45% in 10h, 64% in 40h, and 70h.

[0096]

[0097] Q n =C n Vn +(C1+C2+C3+…+C n-1 )×V

[0098] Q n is the cumulative mass of pesticide released at the nth sampling time point; Q0 is the initial mass of pesticide; C n is the concentration at the nth sampling time point; V0 is the volume of deionized water; V is the volume of each sampling.

[0099] Drug loading rate and encapsulation efficiency test:

[0100] 10 mg of the modified polyglutamic acid prepared in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 9 was weighed and completely dispersed in 3 mL of anhydrous ethanol solution, and ultrasonically crushed for 4 h under ultrasonic conditions to obtain free active ingredients. The supernatant was obtained at a centrifugal speed of 8000 r / mn, and the absorbance of the supernatant was measured. The concentration of the active ingredient can be calculated according to the standard curve.

[0101]

[0102]

[0103] Light degradation resistance test:

[0104] A quantitative amount of avermectin was weighed and dissolved in anhydrous ethanol to prepare a 0.1 mg / mL avermectin solution as a control group, and the modified polyglutamic acid for pesticide suspension prepared by Example 1-Example 4 and Comparative Example 1-Comparative Example 9 with the same avermectin content was also dispersed in anhydrous ethanol solution. 3 mL of the solution was accurately pipetted and added to a 5 mL centrifuge tube to prepare multiple groups of samples, and placed under an ultraviolet lamp (254 nm, 8 W) at the same time, with the lamp tube height being 15 cm from the liquid surface. After 35 hours, a group of centrifuge tubes was taken out, and the residual content of avermectin was measured using an ultraviolet spectrophotometer. The experiment found that the photodegradation rate of the control group at 35 hours was 86.9%.

[0105] Table 1 Summary of experimental data in Examples 1 to 4 and Comparative Examples 1 to 9

[0106]

[0107]

[0108] Data Analysis:

[0109] As can be seen from Table 1, the modified polyglutamic acid for pesticide suspension prepared by the present invention has higher sustained release performance and dispersibility;

[0110] In Comparative Example 1, since no particulate additive was added during the preparation of modified polyglutamic acid for pesticide suspension, and in Comparative Example 2, only "modified polyglutamic acid" was replaced with "γ-polyglutamic acid" during the preparation of the particulate additive, it can be seen from Table 1 that the drug loading rate and encapsulation rate of the pesticide decreased, and the suspension of the pesticide also decreased. This may be because the carboxymethyl cellulose in the particulate additive can increase the repulsion of the particles in the suspension through the charge effect and the spatial repulsion effect, and prevent the particles from flocculating and aggregating. Sodium dodecylbenzene sulfonate can also make the pesticide suspension more dispersed. The modified polyglutamic acid is wrapped with a layer of film on the outer layer of γ-polyglutamic acid, which can prevent the γ-polyglutamic acid from quickly overflowing when it encounters water, thereby improving the sustained release performance of the pesticide suspension.

[0111] In Comparative Example 3, only "the particle size of microcapsule A is 2 mm, and the particle size of microcapsule B is 5 mm" is replaced by "the particle size of microcapsule A is 5 mm, and the particle size of microcapsule B is 2 mm", and in Comparative Example 4, only "20 g microcapsule A, 42 g microcapsule B" is replaced by "42 g microcapsule A, 20 g microcapsule B". It can be seen from Table 1 that the sustained-release performance of the pesticide suspension is reduced, and the suspension of the pesticide is also reduced. This may be because the particle size of microcapsule A increases, and the particle size of microcapsule B decreases. The wall material of microcapsule B is nano-silicon dioxide and polyvinyl alcohol. The smaller the particle size, the easier it is to agglomerate. Polyvinyl alcohol is also more likely to absorb water, resulting in poor sustained-release performance. When the amount of microcapsule A and microcapsule B is exchanged, microcapsule B can better encapsulate the active ingredient due to polyvinyl alcohol and nano-silicon dioxide. When the content of microcapsule B decreases, the sustained-release performance is correspondingly reduced.

[0112] In Comparative Example 5, γ-polyglutamic acid was not added during the preparation of the combined liquid A, and in Comparative Example 6, chitosan was not added during the preparation of the microcapsule A. It can be seen from Table 1 that the sustained-release performance of the pesticide suspension concentrate decreased, and the suspension of the pesticide also decreased. This may be because γ-polyglutamic acid also acts as a fertilizer synergist. When it is wrapped as a core material, it can be released together with the active ingredients in the pesticide, thereby improving the utilization rate of the pesticide and reducing the cost. Chitosan has highly active amino and hydroxyl groups and can react with γ-polyglutamic acid through covalent and ionic crosslinking, thereby improving its dispersibility in the pesticide suspension concentrate.

[0113] In Comparative Example 7, nano silicon dioxide was not added during the preparation of microcapsule B, and in Comparative Example 8, glutaraldehyde was not added during the preparation of microcapsule B. In Comparative Example 9, polyvinyl alcohol was not added during the preparation of microcapsule B. It can be seen from Table 1 that the sustained-release performance of the pesticide suspension is reduced, and the suspension of the pesticide is also reduced. This may be because polyvinyl alcohol and γ-polyglutamic acid improve the sustained-release performance of the pesticide suspension through physical crosslinking. Nano silicon dioxide particles are small and have a large specific surface area. Introducing nano silicon dioxide into polyvinyl alcohol can improve the water absorption rate of the pesticide suspension. Adding crosslinking agent glutaraldehyde can also reduce the water absorption rate. The lower the water absorption rate, the better the sustained-release effect. By adjusting the dosage of nano silicon dioxide, glutaraldehyde and polyethylene glycol, a pesticide suspension with optimal performance can be prepared.

[0114] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0115] The present 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 the present invention should be included in the scope of protection of the present invention.

Claims

1. A modified polyglutamic acid for pesticide suspension, characterized in that: The method comprises the following raw materials in parts by weight: 20-25 parts of microcapsules A, 42-48 parts of microcapsules B, and 10-13 parts of microparticle additives; The microcapsule A is prepared from chitosan, γ-polyglutamic acid and avermectin; The microcapsule B is prepared from γ-polyglutamic acid, polyvinyl alcohol, nano-silicon dioxide and avermectin; The microparticle auxiliary agent is prepared from modified polyglutamic acid, sodium dodecylbenzene sulfonate, avermectin and carboxymethyl cellulose; The modified polyglutamic acid is prepared from γ-polyglutamic acid, polyvinyl alcohol and nano-silicon dioxide; The particle size of the microcapsule A is 2-4 mm; The particle size of the microcapsule B is 5-8 mm; The particle size of the microparticle auxiliary agent is 1-3 mm.

2. The modified polyglutamic acid for pesticide suspension according to claim 1, characterized in that: The preparation method of the microcapsule A is as follows: Step A1: dissolving avermectin in dichloromethane, adding γ-polyglutamic acid and stirring, and adding the mixture into palm oil to obtain a combined solution A; Step A2: Add the γ-polyglutamic acid solution dropwise to the chitosan solution, add sodium dodecylbenzene sulfonate and avermectin, stir at 45-55°C for 1.5-3h, then cool to room temperature, add the combined solution A dropwise thereto, stir for 25-35min, then add the sodium tripolyphosphate solution thereto, stir at room temperature for 1-3h, centrifuge at 7000-8000r / min for 8-10min, wash, freeze-dry, crush and sieve to obtain microcapsules A.

3. The modified polyglutamic acid for pesticide suspension according to claim 2, characterized in that: The usage ratio of avermectin, dichloromethane, γ-polyglutamic acid and palm oil in step A1 is 3-5 g: 4-6 mL: 10-12 g: 15-18 mL.

4. The modified polyglutamic acid for pesticide suspension according to claim 2, characterized in that: The usage ratio of the γ-polyglutamic acid solution, chitosan solution, sodium dodecylbenzene sulfonate, avermectin, combined solution A and sodium tripolyphosphate solution in step A2 is 25-28 mL: 25-28 mL: 1-3 g: 3-5 g: 30-32 mL: 45-50 mL; The γ-polyglutamic acid solution in step A2 is obtained by mixing γ-polyglutamic acid and water at a mass ratio of 10-12:400-450; The chitosan solution in step A2 is obtained by mixing chitosan, acetic acid and water in a mass ratio of 3-5:15-18:400-450; The sodium tripolyphosphate solution in step A2 is obtained by mixing sodium tripolyphosphate and water in a mass ratio of 0.8-1.2:8-10.

5. The modified polyglutamic acid for pesticide suspension according to claim 1, characterized in that: The preparation method of the microcapsule B is as follows: Step B1: dissolving avermectin in dichloromethane, and adding the mixture into palm oil to obtain a combined liquid B; Step B2: deionized water and polyvinyl alcohol are added to a three-necked flask equipped with an electric stirrer and a condenser, and the mixture is kept at 60-70°C for 2-5 hours until the mixture is completely dissolved, and the mixture is cooled to 50°C, and γ-polyglutamic acid and glutaraldehyde are added to react for 2-4 hours, and nano-silicon dioxide and anhydrous ethanol are added thereto, and the mixture is stirred evenly, and ultrasonic dispersion treatment is performed for 1-3 hours and the bubbles are removed to obtain modified polyglutamic acid; Step B3: Add the combined solution B dropwise into the modified polyglutamic acid, stir at room temperature for 1-3 hours, centrifuge at 7000-8000 r / min for 8-10 minutes, wash, freeze-dry, crush and sieve to obtain microcapsules B.

6. The modified polyglutamic acid for pesticide suspension according to claim 5, characterized in that: The mass ratio of avermectin, dichloromethane and palm oil in step B1 is 8-10 g: 4-6 mL: 15-18 mL.

7. The modified polyglutamic acid for pesticide suspension according to claim 5, characterized in that: The usage ratio of deionized water, polyvinyl alcohol, γ-polyglutamic acid, glutaraldehyde, nano-silicon dioxide and anhydrous ethanol in step B2 is 460-480 mL: 18-22 g: 6-10 g: 1-3 mL: 18-22 g: 5-8 mL; The mass ratio of the combined solution B and the modified polyglutamic acid in step B3 is 45-48:25-28.

8. The modified polyglutamic acid for pesticide suspension according to claim 1, characterized in that: The preparation method of the microparticle auxiliary agent is as follows: Disperse modified polyglutamic acid, sodium dodecylbenzene sulfonate, avermectin and carboxymethyl cellulose in water, stir at 50-60°C for 1-3 hours, centrifuge at 7000-8000 r / min for 5-8 minutes, dry at 70-80°C, crush and sieve to obtain a microparticle additive.

9. The modified polyglutamic acid for pesticide suspension according to claim 8, characterized in that: The mass ratio of the modified polyglutamic acid, sodium dodecylbenzene sulfonate, avermectin, carboxymethyl cellulose and water is 8-10:1-3:5-8:0.2-0.5:100-200.

10. A method for preparing modified polyglutamic acid for pesticide suspension according to any one of claims 1 to 9, characterized in that: The preparation method of the modified polyglutamic acid for the pesticide suspension is as follows: The microcapsule A, microcapsule B and microparticle auxiliary agent are uniformly mixed to obtain modified polyglutamic acid for pesticide suspension.

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