Pesticides by dosage form

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Pesticide formulations are products that are typically biologically active, or mixtures thereof, processed into products suitable for the desired environment and used to achieve optimal biological efficacy; adverse effects on the applicator and the environment, and harm to the crop are reduced To the minimum limit.

(1) The old formulation EC is the commonly used pesticide formulation. It contains a large amount of xylene and other organic solvents, which wastes oil resources and causes environmental pollution. Due to the flammability of solvents, they are transported and stored. The choice of container is also limited.

(2) Suspension Concentrate (SC) is an insoluble or slightly water-soluble solid prodrug. With some aids, it is uniformly dispersed in water by ultrafine pulverization to form a fine, highly suspended, flowable and stable material. Liquid solid state system. Suspending agents are usually composed of active ingredients, dispersants, thickeners, anti-precipitation agents, defoamers, anti-freeze agents, and water. The content of active ingredients is generally 5%-50%. The average particle size is generally about 3;m. The dispersion and spreading properties of the suspending agent are all relatively good. The suspension has a high suspension rate, a strong ability to adhere to the surface of the plant, and is resistant to rain erosion, so that the efficacy is significantly longer than that of the wettable powder. In the formulation of pesticide suspensions, attention should be paid to: (1) The selected active ingredient is relatively stable to water, and the size of the original drug does not change during storage; (2) the viscosity of the preparation is suitably low and does not change with the storage temperature. The change; (3) naturally dispersed in water, and the diluent is relatively stable. Since pesticide suspensions are always in the form of concentrated suspensions, chemical instability can occur during storage, especially for long-term storage. In addition, physical stability problems are more often present. This usually involves three aspects: (1) the phenomenon of flocculation and aggregation due to interactions between particles; (2) growth of austenitic crystals; (3) delamination and particle deposition due to gravity. To maintain the physical stability of pesticide suspensions during storage, it is necessary to control the accumulation, sedimentation, and crystal growth of suspended matter through formulations and processing techniques.

(3) Emulsion in water EW and Microemulsion ME have attracted people's attention. Water emulsions (emulsions) and microemulsions are prepared by dispersing liquid or semi-solid pesticide active ingredients in water, and the active ingredients must be stable in water for a long period of time. Under intense agitation, the original drug is dispersed in water by means of an appropriate emulsifier, and then a milky or transparent liquid prepared by adding a stabilizer, an antifreeze agent, etc., is a stable dispersion system. The difference between the water emulsion and the microemulsion is that the particle size of the active ingredient dispersed in water is different, the former is 0.1-50; m, the appearance is milky white; the latter particle is ultrafine, 0.01-0.1; m, the appearance is transparent or Nearly transparent. The amount of emulsifier needed to formulate the microemulsion is usually larger than that when formulating the emulsifiable concentrate or the water emulsion, and sometimes the amount is up to 30%. Therefore, microemulsions are currently only suitable for high value-added crops such as fruit trees and vegetables.

Suspension emulsion (SuspoemulsionSE) is a stable high-suspension milky system prepared from water-insoluble pesticide powders and crude oils, with the aid of various additives and formulated with water as the dispersion medium. It consists of an emulsion phase and a continuous phase, with one or more than one active ingredient in both phases, but the active ingredient in the continuous phase exists as a solid dispersion. Therefore, the advantages of the suspension agent and the water emulsion avoid the poisoning of the pesticide and the wet powder due to the organic solvent and the dust to the operator and the pollution to the environment. The storage and transportation are also relatively safe, and the performance is excellent and the biological activity is relatively high. The efficacy is also relatively long-lasting. Suspension agents will gradually replace the wettable powder and become the main formulation of pesticides, and will drive the development of pesticide formulations such as SE, EW and WDG.

(4) Wettable powder (WP)

(5) Water-based (also called water-based) dosage forms and water-dispersible granules (WDG).

Pesticide water-based dosage forms use water as the dispersion medium, and the pesticide original drug (solid or oily liquid) is suspended or emulsified and dispersed in water by the action of dispersants or emulsifiers and other auxiliary agents. Compared with emulsifiable concentrate, a large amount of organic solvent is reduced; compared with wettable powder, no dust is scattered; toxicity and irritation to humans and animals are low; and phytotoxicity to crops is reduced; organic solvents are not affected. In the storage and transportation process, combustion is caused and safety is high.

(6) Microcapsule Pesticides

Microcapsules and pesticides are micro-capsules formed by encapsulating solids, liquid pesticides, and other active substances in capsule wall materials using microcapsule technology. The so-called microcapsule technology uses a technology that coats dispersed solids, liquids, or gases with natural or synthetic high-molecular film-forming materials to form fine particles. Among them, the film-forming material is called a wall material, and the coated material is called a core material, and the particle size of the microcapsule is generally 1-800 μm. The technology separates the object from the surrounding environment through a hermetic or semi-permeable wall film, so as to achieve the purpose of protecting and stabilizing the core material, shielding the odor or color, controlling the release of the core material, and the like. These functions make microencapsulation an effective commercial method in many industrial fields.

The first to market microencapsulated pesticides to the market is the Pennwalt company in the United States. Its first product was the microencapsulated methyl parathion introduced in 1974. Since then, the sustained-release technology has received extensive attention in the pesticide industry. Every year, the United States holds an “International Conference on Controlled Release of Pesticides” in the United States; it summarizes the exchange of research results. The company subsequently introduced microencapsulated diazinon, microencapsulated permethrin, herbicide DDT, pyrethroid, and chlormequat, and it has been microencapsulated with various wall materials. By 1994, more than 50 commercial microcapsule pesticides had been commercialized.

Seed coating agent classification

First, according to the applicable crop classification: dry field crop seed coating agent, refers to the seed coating agent applied to dry land crops (including rice dry nursery). Paddy crop seed coating agent: Refers to the seed coating agent applicable to paddy field crops.

Second, according to the shape classification: dry powder seed coating agent, the active ingredients and inactive ingredients by airflow dry crushed, mixed, with seed dressing. Suspension seed coating agent: A suspension dispersion system in which the active ingredient and some of the inactive ingredients are wet-ground and mixed with other ingredients and coated by atomization or the like. This kind of seed coating agent is currently the mainstream type. Suspension seed coating agent: The suspension and dispersion system is prepared by mixing the active ingredient with an appropriate solvent and auxiliary agent and mixing it with the inactive ingredients.

Third, according to the purpose of the classification of physical type: contains a large number of filler materials and adhesives, but does not contain chemical active ingredients, mainly used for rapeseed, tobacco and vegetables and other small particle seed coating. Chemical type: It contains chemical active substances such as pesticides, fertilizers and hormones. It has a more comprehensive effect, but it is relatively prone to phytotoxicity. This kind of seed coating agent is currently the mainstream type, and it is also one of the main development directions of film coating agents in the future. Biotype: Microorganisms or secretions that contain potency against the crop. Special type: It includes seed coating agents with special purpose, such as water storage, drought resistance, oxygen supply, weeding, and regulation. Comprehensive type: It is a comprehensive application of the active ingredients of the above four kinds of coating agents.

Fourth, according to the use of time classification: now package type seed coating agent: seeds in a few hours or days before sowing with this kind of seed coating agent, such as the film curing immediately sowing, coating seeds should not be stored. Pre-packaged seed coating agent: Seeds can be sown at any time after being coated with such seed coating agents, or they can be stored for a certain period of time before sowing.

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