Pickering emulsion system with stable ZnO particles as well as preparation method and application of Pickering emulsion system

Abstract

The invention relates to a Pickering emulsion system with stable ZnO particles as well as a preparation method and application of the Pickering emulsion system. The uniform and stable emulsion is prepared through synergistic compatibility of ZnO particles and an emulsifier EL-10 and screening of different oil-water ratios, and the obtained emulsion has the advantages of being large in viscosity, good in pouring fluidity, good in emulsion stability and the like. Wherein the ZnO solid particles have the characteristics of hydrophilicity and lipophilicity, a single-layer or multi-layer interface potential barrier is formed through irreversible adsorption on an oil-water interface, and coalescence between emulsion droplets is delayed or prevented. Meanwhile, the ZnO particles are also dispersed in a water phase, and a three-dimensional network is formed around the liquid drops, so that the liquid drops are prevented from coalescence. ZnO particles and an emulsifier EL-10 are adsorbed on an interface at the same time, the interfacial tension is greatly reduced, and a synergistic effect is achieved, so that the stability of the emulsion is improved. The stable emulsion prepared by taking ZnO particles as a stabilizer can be used as a pesticide emulsion in water and can be applied to the field of pesticides.

Description

Technical Field

[0001] The invention relates to the technical field of material preparation, in particular to a ZnO particle-stabilized Pickering emulsion system and a preparation method and application thereof. Background Art

[0002] Pickering emulsion is an emulsion stabilized by small solid particles of nanometer or micrometer scale. Since it takes a lot of energy to remove the adsorbed particles from the interface, the stability of Pickering emulsion is higher than that of traditional emulsion. At present, there are many studies on Pickering emulsions with solid stabilizers such as silicon dioxide and titanium dioxide. Pickering emulsions have attracted widespread attention due to their low cost, good biocompatibility and emulsion stability. As a special type of emulsion, solid particles can be adsorbed as stabilizers on two incompatible oil-water interfaces. As a stabilizer for Pickering emulsions, also known as Pickering emulsifiers, the choice of solid particles can determine the stability of the emulsion system.

[0003] In recent years, people have prepared flower-shaped, thorny ball-shaped and three-dimensional hollow polyhedral star-shaped ZnO particles through sol-gel method, uniform precipitation method, thermal decomposition method and hydrothermal method. At present, ZnO is mainly used in the fields of photocatalysis and sensors, while there are few studies on ZnO as a solid emulsifier. At the same time, the morphology of ZnO particles is very similar to the micro-nano structure of rice leaves. Therefore, this kind of bionic morphology particles have good application prospects in the field of pesticide formulation research and development.

[0004] At present, there are few studies on the preparation of Pickering emulsions using ZnO particles as stabilizers and their application in the field of pesticides. Summary of the invention

[0005] Based on the deficiencies of the prior art, the technical problem to be solved by the present invention is how to provide a ZnO particle-stabilized Pickering emulsion system and a preparation method and application thereof.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a ZnO particle-stabilized Pickering emulsion system, comprising the following steps:

[0008] (1) Preparation of ZnO particles:

[0009] (2) Preparation of Pickering emulsion:

[0010] 1) Prepare a solvent containing a bactericide as oil phase A for later use;

[0011] 2) Dissolve ZnO particles in water as the water phase for later use; add an emulsifier into the oil phase A as the oil phase B for later use; then drop the water phase into the oil phase B, treat with high shear, and cool to room temperature to obtain the product.

[0012] Preferably, in the step (1), the preparation method of ZnO particles is: 1) dissolving zinc acetate and L-phenylalanine in water to obtain a mixed solution; 2) adding an alkaline solution to the mixed solution under stirring to adjust the pH; 3) after the pH is adjusted to the target value, standing to react; 4) after the reaction, collecting the solid by centrifugation, washing and drying to obtain the ZnO particles.

[0013] Preferably, in step 1) of step (1), the molar ratio of zinc acetate to L-phenylalanine is 1:2; the concentration of zinc acetate in the mixed solution is 0.05 mol / L; and the concentration of L-phenylalanine in the mixed solution is 0.1 mol / L.

[0014] Preferably, in step 2) of step (1), the alkaline solution is a NaOH solution; the concentration of the alkaline solution is 1.0 mol / L; and the pH of the mixed solution is adjusted to 14.

[0015] Preferably, in step 3) of step (1), the temperature of the static reaction is room temperature and the reaction time is 2 hours; in step 4) of step (1), the centrifugal speed is 10000 rpm and the centrifugal time is 10 minutes; the drying temperature is 50°C and the drying time is 24 hours.

[0016] Preferably, in step 1) of step (2), the fungicide is prochloraz; the solvent is rosin-based vegetable oil ND-60; and the volume ratio of the mass of the fungicide to the solvent is 1 g:4 mL.

[0017] Preferably, in step 2) of step (2), the emulsifier is emulsifier EL-10; the mass of the emulsifier is 0.01-0.1% of the mass of the total system; the mass of the ZnO particles is 0.1-1% of the total system; the mass of the total system is the sum of the masses of the oil phase B and the water phase; the mass ratio of the oil phase B to the water phase is (2-8):(8-2).

[0018] Preferably, in step 2) of step (2), the rotation speed of the high shear treatment is 10000 rpm and the time is 10 min.

[0019] The invention provides a ZnO particle-stabilized Pickering emulsion system, and the Pickering emulsion system is prepared by the preparation method.

[0020] The invention provides application of the Pickering emulsion system in preparing pesticide preparations.

[0021] The technical solution of the present invention achieves the following beneficial technical effects:

[0022] The present invention utilizes the synergistic compatibility of ZnO particles and emulsifier EL-10, and prepares a uniform and stable emulsion by screening different oil-water ratios. The emulsion obtained by the present invention has the characteristics of high viscosity, good pouring fluidity, good emulsion stability, etc. Among them, the ZnO solid particles used in this article have the characteristics of hydrophilicity and lipophilicity, and the particle size is about 2μm. ZnO particles form a single layer or multilayer interface barrier through irreversible adsorption at the oil-water interface, delaying or preventing the coalescence between emulsion droplets. In addition to being adsorbed on the interface, ZnO particles are also dispersed in the aqueous phase, forming a three-dimensional network around the droplets to prevent the droplets from coalescing. ZnO particles and emulsifier EL-10 are adsorbed on the interface at the same time, which has a greater effect on reducing the interfacial tension and has a synergistic effect, thereby improving the stability of the emulsion. The present invention uses ZnO particles as a stabilizer to prepare a stable emulsion, which can be used as a pesticide water emulsion in the field of pesticides. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Scanning electron microscope image of ZnO particles obtained in Example 1 of the present invention;

[0024] Among them, (a) scale is 10μm; (b) scale is 2μm;

[0025] Figure 2 Optical microscope image of the emulsion obtained in Example 1 of the present invention;

[0026] Among them, (a) scale is 200μm; (b) scale is 100μm;

[0027] Figure 3 Laser confocal microscopy image of the emulsion obtained in Example 1 of the present invention;

[0028] Among them, (a) scale is 200μm; (b) scale is 100μm;

[0029] Figure 4 Stability analysis of the emulsion obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and technical effect of the invention of this application clearer, the technical scheme in the embodiment of this application will be clearly and completely described below in conjunction with the drawings in the embodiment of this application. Obviously, the described embodiment is a part of the embodiment of this application, not all the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] In view of the technical problems existing in the prior art, the present invention provides a method for preparing a ZnO particle-stabilized Pickering emulsion system, comprising the following steps:

[0032] (1) Preparation of ZnO particles:

[0033] (2) Preparation of Pickering emulsion:

[0034] 1) Prepare a solvent containing a bactericide as oil phase A for later use;

[0035] 2) Dissolve ZnO particles in water as the water phase for later use; add an emulsifier into the oil phase A as the oil phase B for later use; then drop the water phase into the oil phase B, treat with high shear, and cool to room temperature to obtain the product.

[0036] In the step (1), the preparation method of ZnO particles is as follows: 1) dissolving zinc acetate and L-phenylalanine in water to obtain a mixed solution; 2) adding an alkaline solution to the mixed solution under stirring to adjust the pH; 3) after the pH is adjusted to the target value, standing for reaction; 4) after the reaction, collecting the solid by centrifugation, washing and drying to obtain the ZnO particles.

[0037] In step 1) of step (1), the molar ratio of zinc acetate to L-phenylalanine is 1:2; the concentration of zinc acetate in the mixed solution is 0.05 mol / L; the concentration of L-phenylalanine in the mixed solution is 0.1 mol / L;

[0038] In step 2) of step (1), the alkaline solution is a NaOH solution; the concentration of the alkaline solution is 1.0 mol / L; the pH of the mixed solution is adjusted to 14;

[0039] In step 3) of step (1), the temperature of the static reaction is room temperature and the reaction time is 2 hours;

[0040] In step 4) of step (1), the centrifugal speed is 10000 rpm, the centrifugal time is 10 min; the drying temperature is 50° C., and the drying time is 24 h.

[0041] In step 1) of step (2), the fungicide is prochloraz; the solvent is rosin-based vegetable oil ND-60; the mass ratio of the fungicide to the volume of the solvent is 1 g: 4 mL;

[0042] In step (2) of step (2), the emulsifier is emulsifier EL-10; the mass of the emulsifier is 0.01-0.1% (for example, 0.01%, 0.03%, 0.05%, 0.07% or 0.1%) of the total system mass; the mass of the ZnO particles is 0.1-1% (for example, 0.1%, 0.3%, 0.5%, 0.7% or 1%) of the total system mass; the mass of the total system is the sum of the masses of the oil phase B and the water phase; the mass ratio of the oil phase B to the water phase is (2-8):(8-2);

[0043] In a preferred embodiment of the present invention, in step (2) of step (2), the mass of the emulsifier is 0.1% of the total system mass; the mass of the ZnO particles is 0.1-1% of the total system mass; the mass ratio of the oil phase B to the water phase is 3:7;

[0044] In a preferred embodiment of the present invention, in step (2) of step (2), the mass of the emulsifier is 0.05-0.1% of the total system mass; the mass of the ZnO particles is 0.5-1% of the total system mass; the mass ratio of the oil phase B to the water phase is 3:7;

[0045] In a preferred embodiment of the present invention, in step (2) of step 2), the rotation speed of the high shear treatment is 10000 rpm and the time is 10 min.

[0046] The invention also provides a ZnO particle-stabilized Pickering emulsion system, and the Pickering emulsion system is prepared by the preparation method.

[0047] The present invention also provides an application of the Pickering emulsion system in preparing pesticide preparations.

[0048] The following is a detailed description of a ZnO particle-stabilized Pickering emulsion system, a preparation method and an application thereof of the present invention through specific examples.

[0049] Raw materials used in the embodiments of the present invention:

[0050] 97% prochloraz technical: Ningxia Yifan Biotechnology Co., Ltd.;

[0051] Emulsifier EL-10: Jiangsu Haian Petrochemical Plant;

[0052] ND-60 solvent: Fujian Nord Biotechnology Co., Ltd.

[0053] Example 1

[0054] This embodiment provides a method for preparing a ZnO particle-stabilized Pickering emulsion system, comprising the following steps:

[0055] (1) Preparation of ZnO particles:

[0056] 5mmol zinc acetate and 10mmol L-phenylalanine were dissolved in 100mL ultrapure water to obtain a mixed solution; under the condition of magnetic stirring, 1.0mol / L NaOH solution was added to the mixed solution to adjust the pH to 14; after the pH was adjusted to the target value, the solution was allowed to stand for reaction at room temperature for 2h; after the reaction, the solution was centrifuged at 10000rpm for 10min, the solid was collected, and it was washed with ultrapure water and ethanol for 3 times respectively, and dried at 50℃ for 24h to obtain the obtained product;

[0057] The electron scanning microscopy image of the ZnO particles obtained in this example is as follows Figure 1 As shown, according to Figure 1 It can be seen that the obtained ZnO particles are evenly dispersed, uniform in particle size and regular in morphology. As a new type of stabilizer, it is beneficial to improve the stability of Pickering emulsion.

[0058] (2) Preparation of Pickering emulsion:

[0059] 1) Dissolve 5.0 g of 97% prochloraz technical drug in 20 mL of ND-60 solvent (Fujian Nord Biotechnology Co., Ltd.) as oil phase A for later use;

[0060] 2) Add emulsifier (EL-10) to oil phase A as oil phase B for later use; dissolve ZnO particles in water as water phase for later use;

[0061] The water phase is slowly added dropwise to the oil phase B (the mass ratio of the oil phase B to the water phase, i.e., the oil-water ratio is 3:7), wherein the mass of the ZnO particles in the water phase is 0.5% of the mass of the total system, and the mass of the emulsifier in the oil phase B is 0.1% of the mass of the total system; the mass of the total system is the sum of the masses of the oil phase B and the water phase;

[0062] The mixture was immediately subjected to high shearing at 10,000 rpm for 10 min and then cooled to room temperature to obtain a Pickering emulsion.

[0063] The optical microscope image of the Pickering emulsion obtained in this example is as follows: Figure 2 As shown in the laser confocal microscopy image Figure 3 As shown. Figure 2 , Figure 3 It can be seen that the average droplet size of the Pickering emulsion is about 50 μm. Figure 2 It can be clearly seen that a dense layer of particles covers the surface of the droplet. Figure 3 As shown, all the oil droplets in the emulsion are tightly arranged, and the droplets have a red ring layer, indicating that the dyed ZnO / EL-10 mixture is adsorbed on the oil-water interface to provide an interfacial barrier, thereby preventing the droplets from coalescing and maintaining the stability of the emulsion.

[0064] The backscattered light intensity value of the Pickering emulsion obtained in this example was observed by an emulsion stabilizer. The result is as follows: Figure 4 As shown, there is no water separation or stratification at the bottom and top of the emulsion, indicating that the emulsion has good stability.

[0065] Example 2

[0066] In order to clarify the effect of the oil-water ratio on the stability of the emulsion, this embodiment provides a method for preparing a Pickering emulsion system stabilized by ZnO particles. The difference from Example 1 is that in step (2), the mass of the ZnO particles is kept unchanged at 1% of the total system mass, the mass of the emulsifier EL-10 is set to 0% and 0.1% of the total system mass, respectively, and the oil-water ratio is changed to (2-8):(8-2), as shown in Table 1. The other steps and parameters are the same as those in Example 1.

[0067] The stability of the obtained emulsion was measured and the results are shown in Table 1.

[0068] Characterization of emulsion stability: Turbiscan Lab is used to analyze the stability of emulsions. Place the prepared samples in the sample pool, scan once every 10 minutes, set the multiple scan mode, and the temperature is 25±2℃.

[0069] Water separation rate: the ratio of the volume of precipitated water to the total volume;

[0070] Table 1 Effect of different oil-water ratios on emulsion stability

[0071]

[0072] According to Table 1, the selection of emulsifier can reduce the water separation rate of the emulsion and improve the stability of the emulsion. When the emulsifier is added, different oil-water ratios still have different degrees of influence on the water separation rate of the emulsion. The reason for the analysis is that the oil-water ratio affects the stability of the emulsion by affecting the average particle size, dispersion, interfacial film stability of the emulsion, and the distribution and action of the emulsifier. Therefore, controlling and adjusting the oil-water ratio is one of the key steps in preparing a stable emulsion.

[0073] Example 3

[0074] In order to clarify the effect of the addition amount of ZnO and EL-10 on the stability of the emulsion, this embodiment provides a method for preparing a Pickering emulsion system stabilized by ZnO particles. The difference from Example 1 is that in step (2), the oil-water ratio is kept unchanged at 3:7, the mass of the emulsifier EL-10 is set to 0.01%-0.1% of the total system mass, and the mass of the ZnO particles is set to 0.1%-1% of the total system mass, as shown in Table 2. The other steps and parameters are the same as those in Example 1.

[0075] The stability of the obtained emulsion was measured, and the results are shown in Table 2 below.

[0076] Table 2 Effect of adding different contents of ZnO and EL-10 on the stability of emulsion

[0077]

[0078] According to Table 2, the addition amount of emulsifier EL-10 and ZnO has different degrees of influence on the water separation rate of the emulsion. The reason for the analysis is that the emulsification process is essentially a process of using surfactants to reduce surface tension. If the amount of emulsifier is small, the emulsifier molecules are not enough to cover the entire oil-water interface, and they are loosely arranged on the interface, resulting in the interfacial tension not reaching the minimum and the emulsion system being unstable. If the amount of emulsifier is too large, although the interfacial tension is reduced to the minimum and a stable emulsion is obtained, it may cause an increase in foam and affect the quality of the emulsion, such as causing the emulsion to be too viscous, which brings inconvenience to use.

[0079] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing a ZnO particle-stabilized Pickering emulsion system, characterized in that: The following steps are involved: (1) Preparation of ZnO particles: (2) Preparation of Pickering emulsion: 1) Prepare a solvent containing a bactericide as oil phase A for later use; 2) Dissolve ZnO particles in water as the water phase for later use; add an emulsifier into the oil phase A as the oil phase B for later use; then drop the water phase into the oil phase B, treat with high shear, and cool to room temperature to obtain the product.

2. The preparation method according to claim 1, characterized in that In the step (1), the preparation method of ZnO particles is as follows: 1) dissolving zinc acetate and L-phenylalanine in water to obtain a mixed solution; 2) adding an alkaline solution to the mixed solution under stirring to adjust the pH; 3) after the pH is adjusted to the target value, standing for reaction; 4) after the reaction, collecting the solid by centrifugation, washing and drying to obtain the ZnO particles.

3. The preparation method according to claim 2, characterized in that: In step 1) of step (1), the molar ratio of zinc acetate to L-phenylalanine is 1:2; the concentration of zinc acetate in the mixed solution is 0.05 mol / L; and the concentration of L-phenylalanine in the mixed solution is 0.1 mol / L.

4. The preparation method according to claim 2, characterized in that: In step 2) of step (1), the alkaline solution is a NaOH solution; the concentration of the alkaline solution is 1.0 mol / L; and the pH of the mixed solution is adjusted to 14.

5. The preparation method according to claim 2, characterized in that: In step 3) of step (1), the static reaction temperature is room temperature and the reaction time is 2 hours; in step 4) of step (1), the centrifugal speed is 10000 rpm and the centrifugal time is 10 minutes; the drying temperature is 50°C and the drying time is 24 hours.

6. The preparation method according to claim 1, characterized in that: In step 1) of step (2), the fungicide is prochloraz; the solvent is rosin-based vegetable oil ND-60; and the volume ratio of the fungicide mass to the solvent is 1 g:4 mL.

7. The preparation method according to claim 1, characterized in that: In step 2) of step (2), the emulsifier is emulsifier EL-10; the mass of the emulsifier is 0.01-0.1% of the mass of the total system; the mass of the ZnO particles is 0.1-1% of the mass of the total system; the mass of the total system is the sum of the masses of the oil phase B and the water phase; the mass ratio of the oil phase B to the water phase is (2-8):(8-2).

8. The preparation method according to claim 1, characterized in that: In step 2) of step (2), the rotation speed of the high shear treatment is 10000 rpm and the time is 10 min.

9. A ZnO particle-stabilized Pickering emulsion system, characterized in that: The Pickering emulsion system is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Pickering emulsion system according to claim 9 in preparing pesticide formulations.

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