Suspension concentrate is a coarse suspension system with water as the dispersing medium, which is evenly dispersed in water through grinding and crushing with the help of surfactants and other auxiliaries to form a uniform and stable suspension system with fine particles and high suspension and flow. Suspension not only has a small particle size, good dispersion, good fluidity, high suspension rate, high biological activity, the use of small doses, rainwater resistance, low residue, low toxicity to humans and animals, and other characteristics but also has good compatibility with the environment, safe to use, easy to administer and so on.
The ideal suspension product has the following physical properties:
(1) small particle size and narrow distribution, long-term placement stability, high suspension rate;
(2) good dispersion into the water, affected by water quality (water quality in different areas, different times when the water temperature sometimes varies greatly);
(3) good mobility, re-dispersion (placed at room temperature and hot storage samples) good, long-term placement of the upper part of the bottle wall and cover hanging on the material that is not easy to pour out Less.
The biological activity is as follows:
(1) excellent performance, good wetting and spreading/ or penetration of diluent on the target, large deposition of the drug on the target;
(2) high biological activity, small dosage, long duration of effect, and resistance to rain. Good compatibility with the environment, low residues, low toxicity to humans and animals, and safe to use.
The quality of pesticide formulations is a key factor in determining the effectiveness and value of pesticide products. How to improve the quality of existing formulations, improve their biological activity and physicochemical stability, or develop a better performance of the new compound formulation varieties, expand its application, so that it better play biological activity, extend the shelf life of new compounds, and do a good job of practical production and application of technical support. This requires not only a solid theoretical background of formulation researchers but also a clear understanding of the performance and practical application of the developed formulation.
This requires not only a solid theoretical background of formulation researchers but also a clear understanding of the performance and practical application of the developed formulation products. The suspension system consists of active components, additives system, and carrier water. Pesticide compounds themselves are a class of special chemicals with strong biological activity, if you want to give the best effectiveness of the active ingredient, on the one hand, to fully grasp the type of pesticide structure, mechanism of action, toxicity, physical and chemical properties, control targets; on the other hand, combined with the results of indoor biological activity measurement, screening, and determine the active ingredient with the matching additives.
and determine the matching active ingredient additives system and the added dose. A formulation with good physical stability, if the additives and the active component match poorly (including wettability, dispersion), its biological activity is not necessarily high; conversely, the initial biological activity is high, the long-term physical stability of the formulation is not necessarily good, such as particle size growth, particle aggregation, etc., will also cause a reduction in biological activity. Then how to screen the additives in the suspension formulation
The system, improve the refinement of the formulation, the maximum degree of biological activity of the active components, that is, how to deepen, refine and quantify the screening of the composition of pesticide formulations, which is also the key to improving the level of research and production of pesticide suspensions.
Whether it is an insecticide, acaricide, herbicide, or fungicide, whether it is a single agent or a mixture, simply put, as long as the active components meet the basic conditions for the preparation of suspensions [low solubility in water (usually less than 100 mg/L); melting point should be greater than 60 ℃; chemical stability in water], they can usually be processed into suspensions (special circumstances: if the melting point is less than 60 ℃, the active components with solubility in water greater than 100 mg/L, the auxiliary system is properly screened and the processing process is well controlled, they can also be processed into suspensions).
(Special cases: if the active component with a melting point less than 60 ℃ and solubility more than 100 mg/L in water, the auxiliary system is properly screened and the processing technology is well controlled, it can also be processed as a suspension agent, such as imidacloprid, ether permethrin, etc.). To develop a suspension formulation with its characteristics, it is not enough to know this.
This is because different structural categories of active components due to their active groups, different structures, and their matching additives system and dosage will also exist a large difference. Only a full understanding of the development of the active components, in the screening formulation additives system, will be more targeted, to develop a high biological activity, good stability of the suspension. In the process of formulation research of suspensions, usually need to understand the following aspects of the active component.
First, to understand the type of structure of the active component, impurity situation, physical form, melting point, solubility in water, volatility, stability (water, light, heat, etc.). For example, (1) the active material containing lone pair of electrons is easy to form hydrogen bonds and aquatic groups with water, paste; (2) hydrophobic, large surface area, difficult to wet; (3) as a solid pesticide active ingredients with a variety of crystalline state, a variety of different solubility between the crystalline state will also lead to
(3) Because a solid pesticide active ingredient has multiple crystalline forms, the different solubility between multiple crystalline forms can also lead to crystal growth, often accompanied by changes in crystal shape and characteristics.
The quality of the original drug and its content in the preparation directly affects the performance of the preparation, in general, for a particular original drug, the higher its content in the preparation, the more difficult it is to control the performance; the quality of the original drug is too poor, the proportion of impurities in the preparation is relatively high, and the impurity situation is more complex, it is difficult to prepare high-quality, high-content formulations. The same active component, using the original drug produced by different manufacturers to prepare samples according to the same formula, the performance of the preparations obtained can sometimes be very different.
Different types of active components have different modes of action. Some active components have internal absorption and conduction, some have penetration activity, some have a long shelf life and other characteristics, combined with the specific active component, screening, and active component matching the additive system, the purpose is to effectively improve the utilization of the active component through the role of the additive system, so that it's biological activity can be more fully played. At the same time, we must also consider the application method of the preparation, foliar spray, soil treatment, fly defense, and other different application methods
The requirements for the formulation of additives system are not the same, naturally, the physical characterization of the suspension agent requirements are different.
Different active components have different control effects. Fungicides can be divided into protection, treatment, and systemic fungicides; insecticides have stomach poisoning, touch, fumigation, lure, refusal, avoidance, and other effects; herbicides are divided into selective herbicides and insecticidal herbicides. Different objects, different crops, different duration, and different needs of active components for auxiliary systems. The role of additives is to give the best effectiveness of the active ingredient so that it
The spreading and adhesion of the drug solution on the surface of the plant body are stronger, resistant to rain, increase the retention of pesticides on the surface of the plant, prolong the retention time and improve the penetration ability of the plant epidermis, and promote the absorption of the agent by the organism. The amount of penetration into the organism is more and the holding period is longer, which can achieve the purpose of maximizing the biological activity, reducing the use dose, and reducing the pollution of the environment.
The formulation of suspension composition research and processing technology is relatively complex, involving pesticide chemistry, pesticide formulation science, physical chemistry, chemical machinery, and many other disciplines. At present, the domestic formulation of suspension development is still relatively crude, the development of its formulations is mostly empirical random screening, the lack of the necessary theoretical guidance and scientific selection of additives, the success rate of excellent formulations is relatively low. The main problems are low deposition of the drug on the target, poor resistance to rainwater erosion, biological activity, and the original drug differences are obvious, individual suspension products placed in long-term suspension rate is low, hanging serious, poor dispersion, hot storage after the particle size growth rate, stratification, etc.
The quality of pesticide formulations is a key factor in determining the effectiveness and value of pesticide products. Only the development of fine formulation products with characteristics, to better improve the physical stability of the preparation and the biological activity of the active component, to extend its market shelf life. This also applies to suspensions.
In short, the suspension is the current and future research and development of the hot spot and focus, but also the FAO recommended one of the environmentally friendly dosage forms. A suspension formulation development is successful, its formulation screening and composition play a crucial role. As the active component varies widely, so there is no fixed pattern of formulation screening, only to understand the mastery of more information, pesticide formulation screening to deepen, refine and quantify as much as possible, to develop a fine suspension formulation varieties with characteristics, which is also the key to enhance the level of research and production of pesticide suspensions.