Wet Grinding of Suspension Agents

Suspension agents are mixtures of active ingredients, carriers, and dispersants, which are subjected to wet grinding to produce a viscous, flowable suspension that forms a stable liquid-solid system. These suspensions are created by uniformly dispersing solid active ingredients, which are insoluble or poorly soluble in water, with the aid of certain additives, resulting in small particles within a high-suspension, flowable system.

Classification of Suspension Agents by Product TypeSuspension agents can be categorized by product type into herbicides (such as phenoxyacetic acid, benzoic acid, and phenoxylpropionic acid derivatives), insecticides (organic and inorganic insecticides), and agents (inorganic agents, sulfur agents, etc.).

Within these categories, herbicides typically require a simple D90 particle size below 5 micrometers, insecticides usually aim for a D90 below 2 to 3 micrometers under normal circumstances, while agents demand a finer particle size. Some manufacturers even require submicron particle sizes.

Finer particle sizes with narrower size distributions result in higher efficiency in application, reducing the impact on operators during spraying and environmental pollution. Smaller particle sizes also enhance the efficiency of application during spraying, ultimately reducing the cost of use and increasing profitability.

Wet Grinding of Suspension AgentsIn the preparation of herbicides and insecticides, a disc sand mill is primarily used. Depending on the active ingredient content and a production capacity ranging from 500 to 900 kilograms, a coarse grinding step with 1.2-1.4mm-sized zirconia beads is followed by fine grinding using beads sized 0.8-1.0mm. This process can achieve the required fineness with a D90 below 5 micrometers in one pass.

For the production of agents, the requirements for particle size are even higher. Exceptional temperature control is necessary. Therefore, a combination of disc and pin-type sand mills is recommended, with zirconia beads of sizes 1.0-1.2-1.4mm used for coarse grinding, and sizes 0.6-0.8mm for fine grinding. The use of silicon carbide as the chamber material in the pin-type sand mill effectively controls the material temperature at below 30°C.

Advantages of Wet Grinding of Suspension Agents

1. No dust hazards for operators and the environment.

2. Uses water as a dispersing medium, eliminating flammability and toxicity issues associated with solvents.

3. Allows for the use of active ingredients with different particle sizes, optimizing the biological effectiveness and physical stability of the formulation compared to wettable powders.

4. Liquid suspension agents disperse well in water and can be directly prepared as spray liquids.

5. Higher density with smaller packaging volume.

6. Good dispersibility and adhesion to plant surfaces, resistance to rainwash, resulting in a more significant and longer-lasting effectiveness compared to wettable powders.

7. Features small particle size, high surface activity, strong adhesive properties, no dust generation during formulation, cost-effectiveness, and high efficacy. It combines the advantages of wettable powders and emulsions and can be wetted with water, offering excellent suspension after dilution.