Roland Vandegaer, AkzoNobel Agro Chemicals

Akzo Nobel Surface Chemistry has developed Agrilan™ 752, a new polymeric stabilizer for aqueous suspensions in agro applications.

Complex aqueous dispersions, which contain either multiple active ingredients or built-in oils and non-ionic adjuvants, can now easily be formulated with the help of Agrilan™ 752. This water-soluble polymer ester has a unique double comb structure and acts as a steric dispersant, emulsifier and stabilizer.

Agrilan™ 752 features :

• Handling: low viscosity and easy to dilute.
• Strong adsorption to solid and liquid interfaces
• Tolerant towards salts and electrolytes
• High molecular weight
• Weakly anionic
• 70 % active in a high flash solvent

In water based suspension concentrates, Morwet D-425 (alkylnaphthalene sulfonate condensate) is commonly used as the wetting, dispersing and milling aid in the premix. However, in specific circumstances the strength of adsorption to particle surfaces can be insufficient to provide long-term stability for complex formulations, e.g.:
- when non-ionic adjuvants or oils are added to the SC
- when formulating high density actives
- in high-loading SCs.

In these cases, Agrilan™ 752 will provide the required stability to the formulation. Akzo Nobel Surface Chemistry advises the use of Agrilan 752 with Morwet D-425 as a unique stabilization system for aqueous dispersions in general.

Morwet D-425 is a ‘mobile’ surfactant and will act as an excellent wetting and dispersing agent in the SC premix. It will also assist in a better milling behaviour of the formulation. After the SC has been milled to the required particle size, Agrilan™ 752 is added and, in a short time, Morwet D-425 will partly be replaced by this polymeric stabiliser.

Agrilan™ 752 is a bulky molecule and as such it will take 24 hours or more until the migration process is complete. Therefore, it is recommended not to evaluate the physical properties of the SC (viscosity, particle size, etc) until 24 hours after its preparation.

As a general rule Akzo Nobel Surface Chemistry recommends the following surfactant concentrations in SC applications:
Morwet D-425 at 2.5 % w/w and Agrilan™ 752 at 1.0 % w/w.

Also, suspoemulsions will benefit from the use of combinations of Morwet D-425 with Agrilan™ 752.

A comparison between three different stabilsers in a typical SC formulation, containing 10 % of a built-in adjuvant:

Flutriafol 250 g/l Suspension Concentrate

Flutriafol 25.0 %
Morwet D-425 2.5 %
Berol 175 10 .0 %
Stabiliser: 1.0 %
- Agrilan™ 752
- Block copolymer (BC)
- Lignosulphonate (LS)

+ MPG, thickener, biocide and water as required

The presence of 10% of a built-in adjuvant, such as an ethoxylated alcohol (Berol 175), in this flutriafol SC leads to separation and viscosity increase. While surfactants like a block copolymer or a lignosulfonate increased the instability of the formulation further, adding Agrilan™ 752 at 1 % resulted in a low viscosity and stable suspension.