Pesticide nanogel suspending agent and preparation method thereof

Abstract

The invention discloses a pesticide nanogel suspending agent and a preparation method thereof, in the preparation process, a core material is firstly prepared, i.e., pesticide active ingredients are loaded on nano diatomite through negative pressure, then a single-layer coated core material is prepared, i.e., the nano diatomite loaded with the pesticide is coated with modified chitosan, and the single-layer coated core material is prepared. The preparation method comprises the following steps: preparing a single-layer coated core material, then preparing a double-layer coated core material, namely, curing and coating the single-layer coated core material with sodium alginate to obtain a double-layer coated product, and then dispersing the double-layer coated product in a system to obtain the pesticide nanogel suspending agent. According to the technical scheme, the wall material of the core-shell structure is combined with the carrier of the porous structure, so that the pesticide achieves the optimal slow-release effect and the optimal extension effect, and the preparation method is simple in condition, simple and convenient in technological process, low in cost, environmentally friendly in material and wide in application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of pesticide preparation, and more particularly to a pesticide nano gel suspension and a preparation method thereof. Background Art

[0002] In the field of pesticide formulations, traditional pesticide suspensions mainly disperse the active ingredients of pesticides in water or organic solvents to form suspensions to improve the application efficiency and bioavailability of pesticides. Among them, some advanced existing technologies have begun to explore the use of gel systems to stabilize pesticide particles, such as microgel suspensions. This type of product forms a tiny gel network structure to wrap pesticide particles, thereby improving the stability and persistence of pesticides to a certain extent.

[0003] However, existing microgel suspensions still have some significant disadvantages. The size of some microgel particles is relatively large, usually at the micron level, which limits their ability to penetrate into plant tissues and their ability to accurately strike target pests. Secondly, traditional gel materials have poor biodegradability and are easily accumulated in the environment, posing potential risks to the environment. It is important to note that although the existing encapsulated core-shell structured pesticide suspensions can disperse pesticides evenly and effectively improve the effect, they are difficult to act for a long time, which also limits the development of this technology.

[0004] Therefore, how to provide an environmentally friendly, effective, and simple-to-prepare pesticide gel suspension with a long-acting sustained-release effect is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] In view of this, the present invention provides a pesticide nano gel suspension and a preparation method thereof, which adopts the design of nano core-shell structure, optimizes material selection, and cooperates with other additives to prepare a product with excellent performance and environmental friendliness.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing a pesticide nanogel suspension comprises the following steps:

[0008] Step 1: Preparation of core material

[0009] The nano-diatomaceous earth is dispersed in deionized water, and then the target pesticide is added to the dispersion system, and then the entire dispersion system is stirred under negative pressure conditions to obtain a core material;

[0010] Step 2: Preparation of single-layer wrapped core material

[0011] The core material suspension prepared in step 1, the modified chitosan and the emulsifier are fully mixed to obtain a homogeneous mixed solution, and then the homogeneous mixed solution is added to the cross-linking agent, the pH is adjusted to 7.5-8.5, and the cross-linking reaction is stirred at room temperature for 8-10 hours. After the reaction is completed, a single-layer wrapped core material is obtained;

[0012] Step 3: Preparation of double-layer wrapped core material

[0013] Add sodium alginate to the single-layer wrapped core material prepared in step 2, heat to 40-50° C., stir and dissolve, then drop the mixture into a calcium chloride solution, stir and solidify at 100-200 r / min for 30-60 min, to obtain a double-layer wrapped core material;

[0014] Step 4: Preparation of suspension

[0015] The double-layer wrapped core material prepared in step 3 is evenly dispersed in deionized water with an emulsifier, a dispersant and a pH adjuster, and the mixture is stirred at 1000-5000 r / min and heated to 40-45° C. for emulsification treatment for 10-30 minutes to obtain a pesticide nanogel suspension.

[0016] Preferably, the mass ratio of the pesticide to the nano-diatomaceous earth in step 1 is 1:(1-6).

[0017] Preferably, the stirring treatment under negative pressure conditions in step 1 is specifically as follows: placing the dispersed system in a closed container, placing a magnetic stirrer, and starting stirring after evacuating the container at a speed of 100-300 r / min for 3-5 h.

[0018] Preferably, in steps one to three, the mass ratio of pesticide: modified chitosan: sodium alginate = (1-4): (0.5-2): (0.5-2).

[0019] Preferably, the modified chitosan in step 2 is modified chitosan grafted with β-cyclodextrin, and the β-cyclodextrin is grafted with one or more carboxyl groups.

[0020] Preferably, the mass ratio of the emulsifier to the modified chitosan in step 2 is 1:40.

[0021] Preferably, in step 2, the emulsifier is Tween-20, and the cross-linking agent is vanillin.

[0022] Preferably, the mass concentration of the calcium chloride solution in step three is 1%-2%.

[0023] Preferably, the emulsifier in step 4 is one or more of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether phosphate, and sodium dodecylbenzene sulfonate, the dispersant is at least one of dispersant NNO, dispersant MF, and sodium lignin sulfonate, and the pH adjuster is sodium hydroxide or hydrochloric acid; the mass ratio of double-layer wrapped core material: emulsifier: dispersant: pH adjuster: deionized water = (20-30): (3-5): (1-3): (0.1-0.5): (100-150).

[0024] The present invention also provides a pesticide nano gel suspension prepared by the method described in the above technical solution.

[0025] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a pesticide nanogel suspension and a preparation method thereof, which has the following beneficial effects:

[0026] In the technical scheme of the present invention, the active ingredients of the pesticide are first loaded on the porous nano-diatomaceous earth, which preliminarily lays the foundation for the sustained release and effectively ensures the storage stability of the pesticide; then the nano-diatomaceous earth loaded with the active ingredients of the pesticide is respectively wrapped with modified chitosan and sodium alginate to form a core-shell-shell structure, which can improve the stability of the pesticide on the one hand, and on the other hand, can also improve the drug loading and encapsulation rate, and can also prolong the release time of the pesticide and the effective action time, and at the same time, the loss of the pesticide components is avoided to the greatest extent, and the pollution to the environment is avoided.

[0027] In addition, nano-diatomite is a natural material, and both modified chitosan and alginate gel have the advantage of being naturally degradable, and their degradation products are non-toxic and have no impact on the environment. The reaction using modified chitosan and alginate gel as wall materials can be carried out at room temperature, and the reaction process is short, easy to operate, and will not affect the structure and activity of the active ingredients of the pesticide. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The modified chitosan described in the embodiment is prepared by the following method:

[0030] Weigh 4 g of β-cyclodextrin, dissolve it in 25 mL of 25% sodium hydroxide solution by mass, accurately weigh 6 g of chloroacetic acid, dissolve it in 10 mL of deionized water, add the chloroacetic acid solution dropwise to the β-cyclodextrin solution, react overnight at room temperature, then adjust the pH of the solution to 9.0 with dilute hydrochloric acid, then add methanol until the solution no longer generates precipitation, let stand for 10 hours, filter the product, add water to dissolve, then add methanol to precipitate, until the solution no longer generates precipitation, filter the product, and repeatedly wash the obtained product with ethanol aqueous solution until the chloroacetic acid is washed clean, and dry to obtain a white product, carboxymethyl-β-cyclodextrin;

[0031] 0.8 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 6 g of carboxymethyl-β-cyclodextrin were dissolved in 50 mL of water and reacted at low temperature for half an hour. 1 g of chitosan was dissolved in 30 mL of 1% acetic acid solution, and then the carboxymethyl-β-cyclodextrin solution was added dropwise, and reacted at low temperature of 5-10° C. for 24 hours. The product was dialyzed in deionized water for 3 days, with the water changed 18 times. The dialyzate was precipitated with a large amount of acetone, washed with anhydrous ethanol for many times, and dried to obtain a white product, i.e., carboxymethyl-β-cyclodextrin modified chitosan.

[0032] Example 1

[0033] A method for preparing a pesticide nanogel suspension comprises the following steps:

[0034] Step 1: Preparation of core material

[0035] The nano-diatomaceous earth was dispersed in deionized water, and then the target pesticide was added to the dispersion system. After that, the entire dispersion system was placed in a closed container, a magnetic stirrer was put in, and the stirring was started after vacuuming at a speed of 200 r / min for 4 hours to obtain a core material, and the mass ratio of the pesticide to the nano-diatomaceous earth was 1:1;

[0036] Step 2: Preparation of single-layer wrapped core material

[0037] The core material suspension prepared in step 1, carboxymethyl-β-cyclodextrin modified chitosan and Tween-20 are fully mixed to obtain a homogeneous mixed solution (mass ratio of Tween-20: carboxymethyl-β-cyclodextrin modified chitosan = 1:40), and then the homogeneous mixed solution is added to 20% vanillin by mass, and the pH is adjusted to 7.5-8.5 with sodium hydroxide or hydrochloric acid, and the cross-linking reaction is stirred at room temperature for 8 hours. After the reaction is completed, a single-layer wrapped core material is obtained;

[0038] Step 3: Preparation of double-layer wrapped core material

[0039] Add sodium alginate to the single-layer wrapped core material prepared in step 2, heat to 50°C, stir and dissolve, then drop the mixture into a 2% calcium chloride solution and stir and solidify at 200 r / min for 50 minutes to obtain a double-layer wrapped core material;

[0040] Step 4: Preparation of suspension

[0041] The double-layer wrapped core material prepared in step 3, alkylphenol polyoxyethylene ether, dispersant NNO and pH regulator are uniformly dispersed in deionized water, stirred at 3000 r / min and heated to 45° C. for emulsification treatment for 20 minutes to obtain a nano-sized pesticide gel suspension with a drug loading of 39.3% and an encapsulation efficiency of 95.7%.

[0042] Steps 1 to 3: mass ratio of pesticide: carboxymethyl-β-cyclodextrin modified chitosan: sodium alginate = 1:0.5:0.5.

[0043] In step 4, the pH adjuster is sodium hydroxide or hydrochloric acid; the mass ratio of double-layer wrapped core material: alkylphenol polyoxyethylene ether: dispersant NNO: pH adjuster: deionized water = 20:3:1:0.1:100.

[0044] Example 2

[0045] A method for preparing a pesticide nanogel suspension comprises the following steps:

[0046] Step 1: Preparation of core material

[0047] The nano-diatomaceous earth was dispersed in deionized water, and then the target pesticide was added to the dispersion system. After that, the entire dispersion system was placed in a closed container, a magnetic stirrer was placed in it, and the stirring was started after vacuuming at a speed of 200 r / min for 4 hours to obtain a core material, and the mass ratio of the pesticide to the nano-diatomaceous earth was 1:4;

[0048] Step 2: Preparation of single-layer wrapped core material

[0049] The core material suspension prepared in step 1, carboxymethyl-β-cyclodextrin modified chitosan and Tween-20 are fully mixed to obtain a homogeneous mixed solution (mass ratio of Tween-20: carboxymethyl-β-cyclodextrin modified chitosan = 1:40), and then the homogeneous mixed solution is added to 20% vanillin by mass, and the pH is adjusted to 7.5-8.5 with sodium hydroxide or hydrochloric acid, and the cross-linking reaction is stirred at room temperature for 9 hours. After the reaction is completed, a single-layer wrapped core material is obtained;

[0050] Step 3: Preparation of double-layer wrapped core material

[0051] Add sodium alginate to the single-layer wrapped core material prepared in step 2, heat to 45°C, stir and dissolve, then drop the mixture into a 2% calcium chloride solution, stir and solidify at 200 r / min for 40 minutes, and obtain a double-layer wrapped core material;

[0052] Step 4: Preparation of suspension

[0053] The double-layer wrapped core material prepared in step 3, nonylphenol polyoxyethylene ether phosphate, dispersant MF and pH regulator are uniformly dispersed in deionized water, stirred at 4000 r / min and heated to 40° C. for emulsification treatment for 25 minutes to obtain a nano-sized pesticide gel suspension with a drug loading of 38.2% and an encapsulation efficiency of 95.7%.

[0054] Steps 1 to 3: mass ratio of pesticide: carboxymethyl-β-cyclodextrin modified chitosan: sodium alginate = 3:1:1.

[0055] In step 4, the pH adjuster is sodium hydroxide or hydrochloric acid; the mass ratio of double-layer wrapped core material: nonylphenol polyoxyethylene ether phosphate: dispersant MF: pH adjuster: deionized water = 25:4:2:0.3:130.

[0056] Example 3

[0057] A method for preparing a pesticide nanogel suspension comprises the following steps:

[0058] Step 1: Preparation of core material

[0059] The nano-diatomaceous earth was dispersed in deionized water, and then the target pesticide was added to the dispersion system. After that, the entire dispersion system was placed in a closed container, a magnetic stirrer was placed in it, and after vacuuming, stirring was started at a speed of 100 r / min for 5 hours to obtain a core material, and the mass ratio of the pesticide to the nano-diatomaceous earth was 1:6;

[0060] Step 2: Preparation of single-layer wrapped core material

[0061] The core material suspension prepared in step 1, carboxymethyl-β-cyclodextrin modified chitosan and Tween-20 are fully mixed to obtain a homogeneous mixed solution (mass ratio of Tween-20: carboxymethyl-β-cyclodextrin modified chitosan = 1:40), and then the homogeneous mixed solution is added to 20% vanillin by mass, and the pH is adjusted to 7.5-8.5 with sodium hydroxide or hydrochloric acid, and the cross-linking reaction is stirred at room temperature for 10 hours. After the reaction is completed, a single-layer wrapped core material is obtained;

[0062] Step 3: Preparation of double-layer wrapped core material

[0063] Add sodium alginate to the single-layer wrapped core material prepared in step 2, heat to 50°C, stir and dissolve, then drop the mixture into a 1% calcium chloride solution and stir and solidify at 200r / min for 30min to obtain a double-layer wrapped core material;

[0064] Step 4: Preparation of suspension

[0065] The double-layer wrapped core material prepared in step 3, sodium dodecylbenzene sulfonate, sodium lignin sulfonate and pH regulator are uniformly dispersed in deionized water, stirred at 5000 r / min and heated to 40° C. for emulsification treatment for 15 minutes to obtain a nano-sized pesticide gel suspension with a drug loading of 36.9% and an encapsulation efficiency of 95.5%.

[0066] Steps 1 to 3: mass ratio of pesticide: carboxymethyl-β-cyclodextrin modified chitosan: sodium alginate = 4:2:1.

[0067] In step 4, the pH regulator is sodium hydroxide or hydrochloric acid; the mass ratio of double-layer wrapped core material: sodium dodecylbenzene sulfonate: sodium lignin sulfonate: pH regulator: deionized water = 30:5:3:0.5:150.

[0068] Comparative Example 1

[0069] The difference from Example 3 is that nano-diatomaceous earth is not used as a carrier, and the active ingredients of the pesticide are directly encapsulated by modified chitosan + sodium alginate. The drug loading is 23.9% and the encapsulation rate is 85.5%.

[0070] Comparative Example 2

[0071] The difference from Example 3 is that modified chitosan is not used for encapsulation, but sodium alginate is directly used for single-layer encapsulation. The drug loading is 25.7% and the encapsulation efficiency is 80.3%.

[0072] Comparative Example 3

[0073] The difference from Example 3 is that sodium alginate is not used for encapsulation, but only modified chitosan is used for encapsulation. The drug loading is 22.7% and the encapsulation efficiency is 81.2%.

[0074] Comparative Example 4

[0075] The difference from Example 3 is that the modified chitosan is replaced by ordinary chitosan. The drug loading is 18.9% and the encapsulation efficiency is 82.5%.

[0076] Comparative Example 5

[0077] The difference from Example 3 is that modified chitosan and sodium alginate are not used for encapsulation. The drug loading is 15.2% and the encapsulation efficiency is 0.

[0078] The above-mentioned embodiments and comparative examples show that the nanomaterial loading + double-layer shell structure encapsulation of the present invention is far superior to the comparative example in terms of drug loading and encapsulation efficiency.

[0079] And there is no doubt that the present invention adopts a combination of double-layer shell structure + porous nano material carrier loading, which is bound to have a more excellent sustained-release effect.

[0080] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will comply with the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a pesticide nanogel suspension, characterized in that: The following steps are involved: Step 1: Preparation of core material The nano-diatomaceous earth is dispersed in deionized water, and then the target pesticide is added to the dispersion system, and then the entire dispersion system is stirred under negative pressure conditions to obtain a core material; Step 2: Preparation of single-layer wrapped core material The core material suspension prepared in step 1, the modified chitosan and the emulsifier are fully mixed to obtain a homogeneous mixed solution, and then the homogeneous mixed solution is added to the cross-linking agent, the pH is adjusted to 7.5-8.5, and the cross-linking reaction is stirred at room temperature for 8-10 hours. After the reaction is completed, a single-layer wrapped core material is obtained; Step 3: Preparation of double-layer wrapped core material Add sodium alginate to the single-layer wrapped core material prepared in step 2, heat to 40-50° C., stir and dissolve, then drop the mixture into a calcium chloride solution, stir and solidify at 100-200 r / min for 30-60 min, to obtain a double-layer wrapped core material; Step 4: Preparation of suspension The double-layer wrapped core material prepared in step 3 is evenly dispersed in deionized water with an emulsifier, a dispersant and a pH adjuster, and the mixture is stirred at 1000-5000 r / min and heated to 40-45° C. for emulsification treatment for 10-30 minutes to obtain a pesticide nanogel suspension.

2. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: The mass ratio of the pesticide to the nano-diatomaceous earth in step 1 is 1:(1-6).

3. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: The stirring treatment under negative pressure conditions in step 1 is specifically as follows: placing the dispersed system in a closed container, placing a magnetic stirrer, and starting stirring after vacuuming at a speed of 100-300 r / min for 3-5 h.

4. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: Step 1-3: mass ratio of pesticide: modified chitosan: sodium alginate = (1-4): (0.5-2): (0.5-2).

5. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: The modified chitosan in step 2 is modified chitosan grafted with β-cyclodextrin, and the β-cyclodextrin is grafted with one or more carboxyl groups.

6. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: The mass ratio of the emulsifier to the modified chitosan in step 2 is 1:

40.

7. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: In step 2, the emulsifier is Tween-20, and the cross-linking agent is vanillin.

8. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: The mass concentration of the calcium chloride solution in step 3 is 1%-2%.

9. The method for preparing a pesticide nanogel suspension according to claim 1, characterized in that: The emulsifier in step 4 is one or more of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether phosphate, and sodium dodecylbenzene sulfonate, the dispersant is at least one of dispersant NNO, dispersant MF, and sodium lignin sulfonate, and the pH adjuster is sodium hydroxide or hydrochloric acid; the mass ratio of double-layer wrapped core material: emulsifier: dispersant: pH adjuster: deionized water = (20-30): (3-5): (1-3): (0.1-0.5): (100-150).

10. A pesticide nanogel suspension prepared by the method according to any one of claims 1 to 9.