Stabilizers for Agrochemical Suspensions

Suspension Concentrates

Suspension concentrates consist of a water insoluble, solid agrochemical active ingredient suspended in water.  These water-based suspensions of solid pesticides, herbicides, and insecticides have risen in popularity for crop protection over the last decade due to their ease of application when compared to other agrochemical application types.  Additional benefits include improved safety as there is no dust or flammable liquid as well as a reduced environmental impact when compared to other crop protection products. 

Formulating Suspension Concentrates

The production of these agrochemical formulations requires special attention as it can be difficult to stabilize water insoluble active agricultural chemicals in suspension.  Often times crystallization of active ingredients can be a problem that results in syneresis and poor shelf life.  Stabilizing additives and rheology modifiers are required to keep the active solids from crystallizing and falling out of suspension.

Stabilizing Additives

As mentioned above, stabilizing agents are used in agrochemical suspensions to prevent the active agrochemicals from crystallizing.  When selecting a stabilizer for an agrochemical suspension it is important to not only consider how well it can stabilize the active ingredients but also how economically efficient it is and how it will affect the other properties of the suspension.  Magnesium aluminum silicate and xanthan gum are commonly used and provide a decent level of stability to agrochemical suspension formulations, however, new data shows that these stabilizing additives can be improved upon or even sometimes replaced by microcrystalline cellulose.

Lattice® Microcrystalline Cellulose

Microcrystalline cellulose (MCC) is produced by hydrolyzing cellulose in wood pulp with acid to remove the para-crystalline region of the cellulose fibers.  MCC that is used as for suspension stability are further treated with carboxymethyl cellulose to produce what is known as colloidal MCC.  These products are known commercially by the Lattice® trade name.  Recently, IFF, the manufacturer of Lattice® tested the efficiency of Lattice® versus magnesium aluminum silicate and xanthan gum as a stabilizing agent for agrochemical suspension applications.

Formulation Viscosity

The viscosity and rheology of the herbicide suspension listed below was tested using both xanthan gum and Lattice® as a stabilizing agent.  
 

• 500 g/L Isoproturon (Solid)
• 10 g/L Herbicide (Liquid)
• 0.3% Stabilizer: Lattice® NTC vs Xanthan
• Balance
  • Antifoam
  • Propylene Glycol
  • Surfactants
  • Preservatives
  • Water

The viscosity and stability of the suspensions is listed in the table below.

Lattice® NTC offers suspension stability at a much lower viscosity than xanthan gum.  In addition, it produces a much less sticky suspension which equates to less waste when using the suspension.
 

Xanthan	Lattice® NTC

Replacing Magnesium Aluminum Silicate

Lattice® was evaluated as a stabilizing agent versus magnesium aluminum silicate in the insecticide suspension listed below.

• 400 g/L Bifenthrin
• 0.3 - 0.5% Stabilizer
• Balance
  • Xanthan Gum
  • Antifoam
  • Glycerol
  • Surfactant
  • Preservatives
  • Water

The suspensions were compared after 2 weeks of storage at room temperature and 54°C. 

Visual assessment showed that the insecticide suspension containing Lattice® NTC-90 is more stable than the suspension containing magnesium aluminum silicate, at half the usage level.  The suspensions were further evaluated on a TurbiScan. 

The TurbiScan results confirmed the long term stability trend found in the visual assessment.

Stabilizing Pesticide-Fertilizer Blends

Pesticide formulators are increasingly seeking ways to blend their products in fertilizers to provide farmers better convenience at lower cost. Typically, fertilizers contain high levels of electrolytes because of the nitrogen, phosphorous, and potassium typically present. In most cases, pesticides cannot be blended into fertilizers because of these electrolytes, which typically destabilize these blends. Thus, a solution to stabilize these formulation blends is required.

Detergent solutions containing high amounts of electrolytes and surfactants were prepared to simulate pesticide-fertilizer blends, as seen below. Lattice® and xanthan gum were added to these solutions to investigate their ability to stabilize these solutions. It was found that only solutions containing Lattice® NTC-50 or a mixture of Lattice® NTC-50 and xanthan gum provided long-term stability. Thus, formulators may incorporate Lattice® NTC-50 to increase stabilization of pesticide-fertilizer blends to overcome the challenge of destabilization that electrolytes present during blending.

Summary and Conclusions

Lattice® MCC improves the stabilization of water-based pesticide, herbicide, and insecticide suspensions particularly for challenging active ingredients.  In addition, it allows for agrochemical stabilization with a minimum increase in viscosity and provide a user-friendly method to control formulation rheology.  Lattice® can be used to completely or partially replace other components like xanthan, magnesium aluminum silicate, and other emulsifiers.  This allows for improved suspension stability at a lower cost.  Contact us today to request your sample of Lattice® NTC.