CN111280167A - Chitosan-coated azoxystrobin microcapsule and preparation method thereof - Google Patents

Abstract

The invention relates to a chitosan coated azoxystrobin microcapsule and a preparation method thereof. The microcapsule comprises the following specific preparation steps: dissolving an azoxystrobin original drug, a surfactant and a cosurfactant in an organic solvent to obtain a solution A; dissolving chitosan in acetic acid solution to obtain solution B; slowly and dropwise adding the solution A into the solution B under the stirring condition, continuously stirring for 30min to obtain azoxystrobin emulsion, and preparing the chitosan-coated azoxystrobin microcapsule by spray drying. The grain diameter of the chitosan-coated azoxystrobin microcapsule prepared by the method is 0.5-20 mu m. The invention can solve the problems of poor stability, low utilization rate, short duration and the like of the traditional preparation.

Description

A kind of chitosan-coated azoxystrobin microcapsule and preparation method thereof

technical field

The invention relates to the field of pesticides, in particular to the technical field of pesticide formulation processing, in particular to a chitosan-coated azoxystrobin microcapsule and a preparation method thereof.

technical background

Azoxystrobin, English name: Azoxystrobin, CAS: 131860-33-8. It is a kind of fungicide that takes the natural antibiotics from mushrooms as the leading compounds, and is synthesized by artificial biomimetic. Mildew, rice blast, etc. have good activity. It can be used for stem and leaf spraying, seed treatment, and soil treatment, mainly for cereals, rice, peanuts, grapes, potatoes, fruit trees, vegetables, coffee, etc. At present, water suspension and water dispersible granules are mainly used in the market, and there are problems such as low effective utilization rate and short duration of effect.

Sustained release technology can effectively solve the problems of fast release speed and short effective action time of pesticide active preparations, reduce or avoid the adverse effects of pesticides, and prolong the service life of pesticides. Among the various sustained-release formulations of pesticides, microcapsules have the highest technical content. It embeds the active ingredient (core material) in the capsule wall material to form a microsphere preparation with a diameter of several micrometers to several hundreds of micrometers, and the core material material is slowly released through the capsule wall. It will become the development direction of new pesticide formulations in the future.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a chitosan-coated azoxystrobin microcapsule and a preparation method thereof. The present invention solves the problems of poor stability, low utilization rate and short duration of effect of traditional pesticide formulations.

The invention utilizes degradable chitosan as a wall material, and prepares chitosan-embedded azoxystrobin microcapsules by a spray drying method. The characterization results show that the prepared microcapsules are regular in shape and have good encapsulation efficiency, drug loading and sustained release properties.

The chitosan microcapsule of the present invention overcomes the shortcomings of the existing dosage forms such as low effective utilization rate, short duration of effect, and easy occurrence of phytotoxicity, and has the advantages of high stability, long duration of effect, and high utilization rate. The chitosan-coated azoxystrobin microcapsules of the present invention have the characteristics of improving the immunity of inducing plants, and have wide application value and market potential.

One aspect of the present invention provides a microcapsule, wherein the wall material of the microcapsule is chitosan, and the core material is azoxystrobin; the diameter of the microcapsule is 0.5-20 μm; the thickness of the wall material is 0.1-9.9 μm μm; in the microcapsules, the ratio of the wall material to the core material is 0.5-150.

Another aspect of the present invention provides a chitosan-coated azoxystrobin microcapsule and a preparation method thereof, the method comprising the following steps:

(1) Weigh the original azoxystrobin and the surfactant respectively and dissolve them in the organic solvent, and make the concentrations of the original azoxystrobin and the surfactant in the solution be 0.5-50 mg/ml and 0-40 mg/ml, respectively, Solution A was obtained; chitosan was weighed and dissolved in an acetic acid solution to prepare a solution of 0.5-20 mg/ml to obtain solution B.

(2) Under stirring conditions, solution A is slowly added dropwise to solution B in a ratio of 1:1-4 by volume to solution B, and stirring is continued for 30 min to obtain azoxystrobin emulsion.

(3) The azoxystrobin emulsion is sprayed, then dried in a spray dryer, the inlet air temperature is 180-200°C, and the outlet air temperature is controlled at 70-100°C to obtain microcapsule powder, and the powder is collected to obtain a chitosan package Azoxystrobin microencapsulated product.

Based on the above technical solutions, preferably, the organic solvent is methanol, acetone, dimethyl sulfoxide, dichloromethane, ethyl acetate, isopropanol, and isobutanol.

Based on the above technical solutions, preferably, the surfactant is Tween 20, Tween 40, Tween 60, Tween 80, lecithin, polyoxyethylene 400 monolaurate, polyoxyethylene 400 monostearic acid One or two or more of ester and polyoxyethylene 400 monooleate.

Based on the above technical solutions, preferably, the molecular weight of the chitosan is 100-500 kDa, and the degree of deacetylation is 60%-99%.

Based on the above technical solutions, preferably, the acetic acid solution is a mixture of glacial acetic acid and water, and the mass percentage of the glacial acetic acid mixture is 0.2%-2%.

beneficial effect

(1) the present invention uses the degradable natural polysaccharide chitosan as the coating material, the coating effect is good, and its degradation product does not pollute the environment;

(2) Azoxystrobin microcapsules coated with chitosan can significantly reduce the risk of azoxystrobin injury;

(3) Under the same dosage conditions, the azoxystrobin microcapsules coated with chitosan can maintain the efficacy for a longer time;

(4) In addition to coating azoxystrobin, chitosan itself also has the activity of inducing the improvement of plant immune activity.

Description of drawings

Fig. 1 is a graph showing the cumulative release amount of the microcapsules prepared in Example 1 and the powder of Comparative Example 1.

Detailed ways

Example 1

Weigh the original azoxystrobin and Tween 20 respectively and dissolve them in acetone, and make the concentration of the original azoxystrobin and surfactant in the solution to be 50mg/ml and 5mg/ml, respectively, to obtain solution A; weigh the molecular weight of 300kDa Chitosan was dissolved in 0.2% acetic acid solution, and prepared into a solution of 20 mg/ml to obtain solution B. With stirring, 1 volume of solution A was slowly added dropwise to 4 volumes of solution B, and stirring was continued for 30 min. The emulsion is spray-dried, the inlet air temperature is 190°C, and the outlet air temperature is controlled at 80°C to obtain microcapsule powder, and the powder is collected to obtain the chitosan-coated azoxystrobin microcapsule product. The particle size of the microcapsules is 0.5-20 μm.

Example 2

Weigh the original azoxystrobin and Tween 20 respectively and dissolve them in ethyl acetate, and make the concentrations of the original azoxystrobin and surfactant in the solution to be 20 mg/ml and 40 mg/ml, respectively, to obtain solution A; Chitosan with a molecular weight of 500 kDa was dissolved in 1% acetic acid solution, and prepared into a solution of 10 mg/ml to obtain solution B. Under stirring, 1 volume of solution A was slowly added dropwise to 1 volume of solution B, and stirring was continued for 30 min. The emulsion is spray-dried, the inlet air temperature is 185°C, and the outlet air temperature is controlled at 80°C to obtain microcapsule powder, and the powder is collected to obtain a chitosan-coated microcapsule product. The particle size of the microcapsules is 0.5-15 μm.

Example 3

Weigh the original azoxystrobin and lecithin and dissolve them in ethanol, respectively, and make the concentration of the original azoxystrobin and surfactant in the solution to be 0.5 mg/ml and 10 mg/ml, respectively, to obtain solution A; weigh the molecular weight of 100 kDa Chitosan was dissolved in 2% acetic acid solution, and prepared into a solution of 1 mg/ml to obtain solution B. Under stirring conditions, 1 volume of solution A was slowly added dropwise to 2 volumes of solution B, and stirring was continued for 30 min. The emulsion is spray-dried, the inlet air temperature is 200°C, and the outlet air temperature is controlled at 70°C to obtain microcapsule powder, and the powder is collected to obtain the chitosan-coated azoxystrobin microcapsule product. The particle size of the microcapsules is 1-10 μm.

Example 4

Weigh the original azoxystrobin and lecithin, respectively, and dissolve them in methanol, and make the concentrations of the original azoxystrobin and surfactant in the solution be 20 mg/ml and 40 mg/ml, respectively, to obtain solution A; The polysaccharide was dissolved in 0.5% acetic acid solution and prepared into a solution of 20 mg/ml to obtain solution B. Under stirring, 1 volume of solution A was slowly added dropwise to 1 volume of solution B, and stirring was continued for 30 min. The emulsion is spray-dried, the inlet air temperature is 190°C, and the outlet air temperature is controlled at 70°C to obtain microcapsule powder, and the powder is collected to obtain the chitosan-coated azoxystrobin microcapsule product. The particle size of the microcapsules is 0.5-20 μm.

Comparative Example 1

Azoxystrobin crystal powder was used as a comparative example.

Example 5

Disperse 0.1 g of chitosan-coated azoxystrobin microcapsules and 0.1 g of azoxystrobin crystal powder in Comparative Example 1 prepared in Examples 1 to 4 above, respectively, in 10 mL of deionized water, place them in a dialysis bag, and immerse them in Fill 200ml of deionized water containing 10% methanol, put it at room temperature, take liquid samples at regular intervals, and use high performance liquid chromatography to measure the concentration of azoxystrobin in the solution; The release amount was calculated by the following formula.

Cumulative release = total cumulative release of azoxystrobin for n days (1)

1 is a graph showing the release effect of azoxystrobin by chitosan-coated azoxystrobin microcapsules prepared in Example 1 of the present invention and comparative example 1 azoxystrobin powder, illustrating the effect of chitosan-coated azoxystrobin microcapsules. Controlled release effect is better.

Claims (6)

1. an azoxystrobin microcapsule, characterized in that the wall material of the microcapsule is chitosan, and the core material is azoxystrobin; the particle size of the microcapsule is 0.5-20 μm; The thickness is 0.1-9.9 μm; in the microcapsule, the weight ratio of the wall material to the core material is 0.5-150:1. 2. the preparation method of the described microcapsule of claim 1, is characterized in that: described comprises the following steps, (1) Weigh the original azoxystrobin and surfactant respectively and dissolve them in an organic solvent to obtain solution A. In the solution A, the concentrations of the original azoxystrobin and surfactant are 40mg/ml; Weigh chitosan and dissolve it in acetic acid solution to obtain solution B, in the solution B, the concentration of chitosan is 0.5-20mg/ml; (2) solution A is slowly added dropwise to solution B in a ratio of 1:1-4 by volume to solution B under stirring conditions, and continues stirring for 30min to obtain azoxystrobin emulsion; (3) spraying the azoxystrobin emulsion, then drying in a spray dryer to obtain microcapsule powder, and collecting the powder to obtain the chitosan-coated azoxystrobin microcapsule; The air temperature is 180-200°C, and the outlet air temperature is controlled at 70-100°C. 3. The preparation method according to claim 2, wherein the organic solvent is methanol, dimethyl sulfoxide, dichloromethane, ethyl acetate, isopropanol, and isobutanol. 4. according to the described preparation method of claim 2, it is characterized in that: surfactant is Tween 20, Tween 40, Tween 60, Tween 80, lecithin, polyoxyethylene 400 monolaurate, polyoxyethylene One or more of ethylene 400 monostearate and polyoxyethylene 400 monooleate. 5. The preparation method according to claim 2, wherein the molecular weight of the chitosan is 100-500 kDa, and the degree of deacetylation is 60%-99%. 6. The preparation method according to claim 2, wherein the acetic acid solution is a solution formed by dissolving glacial acetic acid in water, and the mass percentage of the glacial acetic acid is 0.2%-2%.

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