Water-Dispersible Granules for Agriculture

Water-dispersible granules are solid, non-dusty, granular formulations of agrochemicals that dissolve and disintegrate readily into suspensions when added to water, making them especially useful for spray applications onto plants and crops.  Fertilizers, plant nutrients, herbicides, pesticides, fungicides, and insecticides are examples of formulas manufactured as water-dispersible granules.  Traditionally, these have been sold to crop farmers as wettable powders or liquids.   Water-dispersible granules, however, have several inherent advantages over wettable powders and liquids as they:  

 

  • Have a reduced cost to store, handle, and transport 
  • Minimize health hazards and risks to crop farmers
  • Provide easier measurement and mixing of dry formulas
  • Allow very high levels of loading for active ingredients 

 

When it comes to the logistics of agricultural formulations, liquid formulations will always be more costly to transport, given that active ingredients are pre-suspended in water.  Wettable powder formulations thus have an advantage.  However, from a safety standpoint, powdered agrochemical formulations present an inhalation hazard to crop farmers, as particle sizes can be extremely small.  Since water-dispersible granules do not readily erode into dust and smaller particles, they can be safely and easily measured and mixed into water on-site to make sprayable agrochemical formulas.  

Formulation of Agrochemical Water-Dispersible Granules

A typical water-dispersible granule formulation for agriculture may contain disintegration, binding, and wetting agents, stabilizers, fillers, and the active ingredient itself.  Granules may be formed via dry granulation or wet granulation techniques using an extruder, depending on if any agrochemical components of the granule are sensitive to heat or moisture.  In the case that these components are sensitive to heat and moisture, the dry granulation technique is preferred.  

To realize all the benefits of water-dispersible granules discussed in the previous section, one key property must be achieved when considering the formulation.  The water-dispersible granule must be readily and easily dissolved in water.  Thus, the right disintegration and dissolving agent must be selected.  

Accelerate® DS-813

Accelerate® DS-813 is an internally crosslinked carboxymethyl cellulose (sodium croscarmellose) that is specifically designed to promote rapid disintegration and dissolution of water dispersible granules in agricultural applications.  It is an aid added to granules at low percentages and is compatible with various granulation processes, including wet granulation.  When agrochemicals are dissolved using Accelerate® DS-813, the need for dispersants and formulation components such as emulsifiers may be reduced.  An SEM image of Accelerate® is seen below.

Accelerate® DS-813, resembled above, has long, fibrous particles that readily wick water and expand radially.  It has been engineered to the right molecular weight, particle size, degree of substitution, water absorption capacity and uptake rate for dissolving agricultural active ingredients.  Accelerate®, being a carboxymethyl cellulose, is naturally derived from wood pulp or other natural sources of cellulose.  It poses very low risks to human health and is practically non-toxic and non-bioaccumulative in the environment.

Results with Accelerate® DS-813 

To demonstrate the efficacy of Accelerate® DS-813, agrochemical water-dispersible granule formulations were compared for disintegration performance.  Two sets of granule formulations were made, using an agricultural active ingredient at a 50 wt% concentration with water solubility of ~14mg/mL at 25°C.  One set of granules was formulated using 2 wt% Accelerate® DS-813 and was compared to granules that were formulated without Accelerate® DS-813 (0 wt%).  Both granules were then added to water in graduated cylinders for a visual comparison of disintegration.


Initial, after 10 times inversion 

30 minutes standing

60 minutes standing

Additional 10 times inversion, after 60 minutes standing


The tests showed immediate disintegration of the granules that were formulated with 2 wt% Accelerate® DS-813 after mixing the graduated cylinder via inversion, while the control still contained undissolved granules, which settled at the bottom of the cylinder. Stability of the agrochemical suspension was also demonstrated over the next 60 minutes of the test.  Little visual change to the suspension containing Accelerate® DS-813 was observed, suggesting no significant flocculation or sedimentation of the dissolved formula in water.  At the end of the test, the cylinders were mixed again by inversion, showing how much additional mixing was necessary for the granules that did not use Accelerate® DS-813 to achieve even further disintegration.  

 

An additional test with Accelerate® DS-813 was made to demonstrate the effect of the added percentage of Accelerate® DS-813 on the disintegration of granules in the video below.  



While a more pronounced dissolution is observed with the higher addition percentage of Accelerate® DS-813, it is important to note that the formulations with 1 wt% and 2 wt% of Accelerate® DS-813 both spontaneously begin to dissolve into an aqueous suspension in water even before mixing.

These tests clearly demonstrate the advantages crop farmers will benefit from when their water-dispersible granules are manufactured using Accelerate® DS-813.  Farmers will be able to make agrochemical solutions from water-dispersible granules for spray applications more quickly and easily, saving time and avoiding frustration in the process. 

Water-Dispersible Granule Starter Formulation with Accelerate® DS-813

Ingredients % wt Functionality
Active Ingredient 50–95 Insecticide, herbicide, etc.
METHOCEL™ Binder 0–2 Improves granule strength
Accelerate® DS-813 0.5–2 Disintegration aid
Lattice® NT MCC 5–15 Granulation process aid 
Clay 0–40 Diluent
Dispersant 1–7  
Wetting Agent 0–2  

Summary

Agrochemicals continue to play a pivotal role in the agricultural market by increasing the productivity of crops and protecting their yield. When manufactured in the form of water-dispersible granules, agrochemical formulations like fertilizers, plant nutrients, insecticides, herbicides, fungicides, and pesticides will offer greater cost and safety benefits to crop farmers.  The best-performing water-dispersible granules allow crop farmers to create agrochemical suspensions in water that are easy to make.  Accelerate® DS-813 is the ideal disintegration and dissolution agent for manufacturers of water-dispersible granules to provide immediate dispersion and stabilization of agrochemicals in water.  To request a quote on Accelerate® DS-813, contact us below today.  

 

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