CN107136057A - A kind of highly effective and safe pyrethrin nanometer aqueous emulsion and preparation method thereof - Google Patents

Abstract

A kind of highly effective and safe pyrethrin nanometer aqueous emulsion and preparation method thereof, belong to nano-pesticide formulation production technical field, pyrethrosin primary medicine and emulsifying agent are dissolved in acetone and are used as oil phase, it regard water as aqueous phase, by aqueous phase and oil phase in microcavity body high speed jet mixing, 200 below nm pyrethrin water emulsion insecticide is obtained.Active component is that natural plant extracts do not develop immunity to drugs, and contained all compositions are almost non-toxic to people and animals, the degradable, noresidue in external environment, is a kind of efficient pesticides to environment, agricultural product, people and animals with high security.

Description

A kind of efficient and safe pyrethrin nano water emulsion and preparation method thereof

technical field

The invention belongs to the technical field of production of nanopesticide preparations, and in particular relates to the formula and production method of pyrethrin nanometer water emulsion.

Background technique

With the development of society and the expansion of agricultural scale, the demand for pesticides is increasing day by day, and some high-efficiency and high-residue chemical pesticide preparations are rapidly emerging. However, with the improvement of people's awareness of environmental protection and the advancement of technology in recent years, pesticides have begun to follow the principles of safety, economy, effectiveness, and convenience, and are developing in the direction of non-toxic, environmental protection, and low residue. Environmentally friendly pesticides are currently the focus of development.

Water emulsion is a very important pesticide dosage form in modern pesticides. Because of its good water dispersibility, less organic solvent usage, good wettability and spreading force, it is in line with the direction of modern pesticides towards low toxicity and high efficiency. development trend. However, the following defects are still common in water-in-water emulsions at present: 1) The droplet size is large, and it is easy to float or settle, resulting in stratification; 2) The particle size distribution is wide, which leads to Ostwald ripening; 3) In order to prevent the aggregation of the dispersion system Layering requires the addition of a large amount of emulsifier. In view of the above shortcomings, there is still room for improvement in the efficacy of pesticide emulsions in water, so as to achieve the purpose of greatly reducing application and increasing efficiency.

Contents of the invention

The purpose of the present invention is to provide a pyrethrin nano-water emulsion with stable droplet size, good monodispersity, safety and high efficiency.

The high-efficiency and safe pyrethrin nano water emulsion of the present invention is composed of pyrethrin, emulsifier, acetone and water.

The present invention also proposes a preparation method of the above pyrethrin nano-water emulsion: dissolving the pyrethrin technical substance and emulsifier in acetone as the oil phase, using water as the water phase, and mixing the water phase and the oil phase in a microcavity with a high-speed jet , to prepare pyrethrin nano-water emulsion.

In the present invention, the pyrethrin original drug, which is easy to degrade the environment and has no pollution, and the emulsifier PLGA- b -PEG are dissolved in acetone, a pollution-free organic solvent, mixed with water in the microcavity by high-speed jet flow, and then jet mixed in the microcavity Finally, a pyrethrin water-emulsion insecticide with stable droplet size below 200 nm was obtained. The emulsion droplets were small and stable, and could be kept for at least one month. The particle size dispersion was narrow, and the polydispersity index PDI was less than 0.3. When used, it can be further diluted with more water according to the specific application needs of crop disease control.

In the present invention, acetone is preferably selected as the water-soluble organic solvent in the process of the present invention, which can dissolve pyrethrins and PLGA- b -PEG, and can be miscible with water. According to the toxicity of acetone, it is a third or fourth class solvent, the daily intake is not more than at least 50mg/day, and it is harmless to the environment.

Further, the volume ratio of pyrethrin, emulsifier, water-soluble organic solvent and water is 1:0.018-0.2:9:10.

For the ratio of pyrethrin technical to emulsifier PLGA- b -PEG. If the emulsifier is too small and less than 1:0.018, the surface of the pyrethrin nano-droplets is covered by the emulsifier too low, and the nano-droplets will agglomerate and rapidly increase in size. Adding too much surfactant is greater than 1:0.2, the emulsifier cannot be completely dissolved in the organic solvent before mixing, and the micelle particles of the emulsifier will be pre-formed, which will affect the use efficiency of the emulsifier during mixing, and may make the liquid droplets diameter widened. Therefore, the ratio of pyrethrin original drug to emulsifier (amphiphilic block copolymer PLGA- b -PEG) was selected as 1:0.018-0.2.

The ratio of pyrethrins to acetone is determined by the solubility of pyrethrins. When the ratio is much smaller than 1:9, pyrethrins cannot be completely dissolved in acetone before mixing. And when it is far greater than 1:9, after the pyrethrin acetone solution is mixed with water, most of the pyrethrins cannot be separated out from the mixed solution. Therefore choose 1:9.

The amount of water should be equal to the sum of liquid pyrethrins and acetone, so that the two phases can be fully mixed in equal volumes. Therefore choose water as 10 parts. After mixing, according to the specific application needs of insecticide, it can be further diluted with more water.

The sum of the Reynolds numbers of the jet inlets in the microcavity is greater than 2200, ensuring that the energy is high enough to achieve sufficient turbulence in the mixing chamber, while the volume of the mixing chamber is less than 0.1 mL, ensuring concentrated dissipation of energy and efficient conversion into droplet surface energy , so that the prepared droplets have a small particle size and a narrow distribution.

The pyrethrin nanometer water emulsion of the invention can be used as insecticides for sanitary daily use, pets and plant protection. The nanoemulsion has the characteristics of small droplet size and narrow distribution, good stability, and high drug efficacy. The active ingredient is natural plant extracts that do not produce drug resistance. It is a high-efficiency spectrum insecticide with high safety to the environment, agricultural products, humans and animals, which is degradable and has no residue.

The technical pyrethrin used in the present invention is an oily hydrophobic mixture isolated from pyrethrum flowers. It can be used as a natural broad-spectrum insecticide without developing drug resistance. It can be decomposed into water and carbon dioxide under light conditions, and the pesticides formulated with it have no drug residue after use. Pyrethrins have extremely low toxicity to humans and animals and have no side effects. Tests have proved that its toxicity to warm-blooded animals is only equivalent to that of table salt (LD50, 3000mg/kg). The acute oral LD50 of rats is 2330 mg/kg (female) and 3160 mg/kg (male).

The emulsifier of the present invention is an FDA-approved medical and edible amphiphilic block copolymer PLGA- b -PEG. It has the advantages of non-toxic, non-pollution and easy environmental degradation, which can further guarantee the environmental protection and harmlessness of the prepared emulsifier.

Description of drawings

Figure 1 is a particle size distribution diagram of a nanoemulsion prepared using PLGA- b -PEG as an emulsifier.

Fig. 2 is the time stability curve of the particle size of the nano-aqueous emulsion prepared by using different amounts of PLGA- b -PEG as the emulsifier.

Fig. 3 is the time stability curve of the particle size of the nano-aqueous emulsion prepared by the drop stirring method and the high-speed jet mixing method respectively.

detailed description

In the following examples, the method and equipment requirements for high-speed jet mixing in the microcavity:

The method is: first inject the oil phase and the water phase into a cavity with a volume of 30 μL through two inlets with a diameter of 0.5 mm and mix them. and about 2700.

These mixing parameters can ensure fast high energy density dissipation of mixing, provide high surface energy of emulsion droplets, and make the formed nanoemulsions have the characteristics of small particle size, narrow distribution and high stability.

Example 1: Preparation of 10 mL pyrethrin nanoemulsion in water (containing 4.5, 9, 18, 36, 45 or 100 mg PLGA- b -PEG and 0.5 mL pyrethrin technical drug, respectively).

Dissolve 45 mg PLGA- b -PEG and 0.5 mL pyrethrins in 4.5 mL acetone to form an organic phase.

Take 5 mL of water as the aqueous phase.

The water phase and the organic phase are respectively injected into the microcavity of the high-speed jet mixing device through two inlets, and after mixing, the mixed solution flows out from the cavity outlet, and is collected by a container to obtain pyrethrin nanoemulsion.

Use the dynamic light scattering method to measure the particle size and distribution of the emulsion. The results are shown in Figure 1. The average diameter d _i is 81 nm, and the polydispersity coefficient PDI is 0.29. After a stability test of at least 1 week, the nanoemulsion It is stable below 100nm, and the droplet has no obvious coarsening and delamination.

Take 4.5, 9, 18, 36, 100 mg PLGA- b -PEG in the same way to repeat the above experiment, after the time stability test, as shown in Figure 2, it can be known that the use of more than 9 mg (ie 0.09 parts) of PLGA- b- PEG, the obtained nano-water emulsion can be stable below 200nm for at least 1 month.

Example 2: Comparative experiment of preparation methods of drop stirring and high-speed jet mixing in microcavity (pyrethrin nano-emulsion in water contains 45 mg PLGA-PEG and 0.5 mL pyrethrin original drug)

Adding and stirring comparison experiment: Dissolve 45 mg PLGA-PEG and 0.5 mL pyrethrins in 4.5 mL acetone, slowly drop 5 mL water into the organic solution, and finish the dropping within 2 hours under stirring at 800 rpm to prepare 10 mL pyrethrum Su nanoscale water emulsion.

The stability test of the suspending agent was carried out by the dynamic light scattering method for 1 week. As shown in Figure 3, the emulsion obtained by dripping and stirring, the initial particle size of the droplets was about 150nm, which was lower than that obtained by the method of high-speed jet mixing in the microcavity. It is much larger at 100nm, and increases to about 200nm after 1 day, with obvious particle size coarsening and poor stability.

Example 3: Comparison of the insecticidal effect of pyrethrin water emulsion obtained by different preparation methods (drop stirring and high-speed jet mixing in microcavity) and commercially available pyrethrin water emulsion

The pyrethrin water emulsion prepared by the high-speed jet mixing method in the microcavity of Example 2, the pyrethrin water emulsion prepared by the drop stirring method, and a commercially available pyrethrin water emulsion of a best-selling brand were diluted to 5000 ppm for each of the fruit flies. After spraying once, the death situation and time are listed in the table below.

The results show that the insecticidal onset speed of the pyrethrin nano-emulsion in water prepared by the present invention is much better than that of the pyrethrin in water emulsion prepared by the drop-stirring method, as well as a commercially available pyrethrin water emulsion of a certain best-selling brand.

Claims (7)

1. a kind of highly effective and safe pyrethrin nanometer aqueous emulsion, it is characterised in that：By pyrethrin, emulsifying agent, acetone and water group Into.

2. pyrethrin nanometer aqueous emulsion according to claim 1, it is characterised in that：The pyrethrin, emulsifying agent, third Ketone, the volume ratio of water are 1: 0.018~0.2: 9: 10.

3. pyrethrin nanometer aqueous emulsion according to claim 1, it is characterised in that：The emulsifying agent is amphipathic block Copolymer p LGA-b-PEG。

4. the preparation method of pyrethrin nanometer aqueous emulsion as claimed in claim 1, it is characterised in that：By pyrethrosin primary medicine It is dissolved in emulsifying agent in acetone as oil phase, using water as aqueous phase, by aqueous phase and oil phase in microcavity body high speed jet mixing, system Obtain pyrethrin nanometer aqueous emulsion.

5. the preparation method of pyrethrin nanometer aqueous emulsion according to claim 4, it is characterised in that：The Dalmatian chrysanthemum The volume ratio of element, emulsifying agent and acetone is 1: 0.018~0.2: 9: 10.

6. the preparation method of the pyrethrin nanometer aqueous emulsion according to claim 4 or 5, it is characterised in that：The microcavity The Reynolds number sum of each jet inlet is more than 2200 in body, and microcavity body volume is less than 0.1 mL.

7. the preparation method of pyrethrin nanometer aqueous emulsion according to claim 4, it is characterised in that：The emulsifying agent is Amphipathic nature block polymer PLGA-b-PEG。