Improving Granule Activity Through Smaller Particle Size

Changing regulations required our client to reformulate an agrochemical fungicide to achieve lower dose rates. In order to reduce the dose rate to fit in with proposed new regulatory limits, our client needed to increase the performance of the active ingredient in their fungicide granule (WG). At the same time, they needed the reformulated product to keep the same general spray-dried manufacturing process and recipe used in their factory. Meeting both of these goals would require significantly reducing the particle size of the fungicide in their product to increase bioavailability.

The challenge was clear, but the approach was not until, Battelle developed a lab-scale process that mimicked their existing factory process. This allowed us to predict which modifications would meet their criteria. To arrive at our conclusion, Battelle chemists first tested the effect of significantly reducing the fungicide particle size in the bead-milled slurry used to make the final product. Then the team investigated a series of formulations to accommodate the reduced particle size and still give good WG dispersibility and storage stability. The team determined two things: reducing particle size required a) the addition of a small amount of a new surfactant and b) a slight reduction in the fungicide concentration. Ultimately, we created a number of spray-dried granules of different concentrations, containing much finer particle size of the active ingredient with minimal changes to the inerts in the formulation.

The new sub-micron WG formulations resulted in increased biological activity from the smaller particle size of the fungicide, resulting in a >30% reduction in dose rates used in the field. With good results in our lab trials, Battelle recommended a scale-up test in the customer’s factory that successfully reproduced the small-scale outcomes. The client’s preferred new product met the new regulatory limits with no sacrifice of product quality and efficacy—even after accelerated storage – and a new formulation is now in production and commercial use.