Suspoemulsions formulation

The main purpose of pesticide formulation is to manufacture a product that has optimum biological efficiency, is convenient to use, and minimizes environmental impacts. The active ingredients are mixed with solvents, adjuvants (boosters), and fillers as necessary to achieve the desired formulation. The types of formulations include wettable powders, soluble concentrates, emulsion concentrates, oil-in-water emulsions, suspension concentrates, suspoemulsions, water-dispersible granules, dry granules, and controlled release, in which the active ingredient is released into the environment from a polymeric carrier, binder, absorbent, or encapsulant at a slow and effective rate. The formulation steps may generate air emissions, liquid effluents, and solid wastes. 

Suspoemulsions Key Technology for Tailor-Made Ready-Mix Formulations... 

In this quest suspoemulsions (SE s) offer a valuable and in many cases the only practicable tool to combine a.i. s with the above properties in one formulation. Thus from the beginning SE s were used to combine actives with contrasting physical properties, -insoluble in water and oil, high melting on one side and - oil soluble, low melting on the other side. 

The com market in the US and the cereal market in Europe are good examples of how suspoemulsion formulations quickly penetrated a market by combining essential a.i s required in a crop system as a ready mix product. 

Due to the physical properties of the morpholines and the need to coformulate with other, mostly solid a.i s, suspoemulsions were again the formulation form of choice found in many sales products. 

With the turn of the century, new products with broad-spectrum activity comparable to the best azoles are entering the market (trifloxystrobin, pyraclostrobin). To find their share in the already highly sophisticated application schemes and developed markets, they need to be presented to the customer as complete, broad-spectrum products, preferably incorporating anti resistance tools. In many instances suspoemulsion formulations will be a cornerstone to combine all required pieces of today s fimgicidal armory in one product. 

Su oemulsions are defined as a mixture of a dispersed solid phase and an emulsified oil phase in water as the continuous or bulk phase. The solid phase is a solid, water insoluble active ingredient, the oil phase a liquid pesticide in pure form or dissolved in a water insoluble solvent. The oil phase can sometimes also be an oil or adjuvant. Suspoemulsions are a relatively new formulation type as becomes evident by the fact that a FAO specification was established only as late as 1997. At the same time specific evaluation methods were officially published (CIPAC MT 180) [2]. 

Another well documented, but less widely used method for formulation development is the measurement of electrokinetic properties [14]. These tests require more disdnc-tive/elaborate sample preparation and are mosdy restricted to use during development. Also widely used and relied on are rheological measurements. The scope of rheological measurements ranges from viscosity measurements to the determination of yield points or oscillatory properties, such as the G and G -modules [15]. Since suspoemulsions are not ideal viscous but mostly viscoelastic or dilatant, a wide range of characterization techniques exists. Instrumentation required for this are simple rotary viscosimeters (Brookfield) or more sophisticated stress or shear controlled rotational viscosimeters. 

Suspoemulsions have proven to be valuable tools to formulate ready mix products of various important active ingredients. Many of these have previously not been accessible due to their contrasting physiochemical characteristics. Examples of their impact can be seen in the US com herbicide market and the European fungicide market. SB s have proven to be particularly flexible tools to enable formulators to tailor make a constantly increasing number of difficult new product combinations and adjusting their product ranges to a changing industrial environment. 

Several classes of formulations of disperse systems are encountered in the chemical industry, including suspensions, emulsions, suspoemulsions (mixtures of suspensions and emulsions), nanoemulsions, multiple emulsions, microemulsions, latexes, pigment formulations, and ceramics. For the rational preparation of these multiphase systems it is necessary to understand the interaction forces that occur between the particles or droplets. Control of the long-term physical stability of these formulations requires the application of various surfactants and dispersants. It is also necessary to assess and predict the stability of these systems, and this requires the application of various physical techniques. 

A schematic representation of suspoemulsions is shown in Figure 11.1, where two main types can be distinguished (i) a system whereby the solid particles and emulsion droplets remain as separate entities and (ii) a system whereby the solid particles are dispersed in the oil droplets. Of these two systems, the first is the most commonly appHed when preparing formulations [1]. 

The formulation of suspoemulsions is not an easy task although it is quite easy to produce a stable suspension and an emulsion separately, when the two are mixed they become unstable due to the following interactions [1] ... 

In this chapter, the creation of suspoemulsions using three different formulation, namely paints, sunscreens/colour cosmetics and agrochemicals, will be described. 

The formulation of suspoemulsions for sunscreens and colour cosmetics remains a challenge for the chemist due to the complex interactions between the particles and droplets that may result in heteroflocculation [4]. One of the main challenges here is to ensure that the small submicron particles remain individually dispersed in the formulation in order to achieve maximum UV protection for sunscreens and optimum colour properties for make-up products. To achieve maximum dispersion... 

When colour cosmetic pigments are added to O/W or W/O emulsions, the resulting system is referred to as a suspoemulsion. The particles can be in either the internal or external phases, or both, as illustrated in Figure 11.12. An understanding of competitive interactions is also important when optimising the formulation stability and performance of these materials. 

With suspoemulsions, two active ingredients are formulated together, which not only offers convenience to the farmer but also may result in synergistic biological efficacy. As a consequence, a wider spectrum of disease control may be achieved, particularly when using many fungicides and herbicides. For many suspoemulsions an adjuvant is also added that enhances biological efficacy. 

The formulations of agrochemicals cover a wide range of systems which range from simple aqueous solutions (for water-soluble actives) and self-emulsifiable oils to disperse systems of suspensions, emulsions and microemulsions. More complex formulations such as multiple emulsions and suspoemulsions (mixtures of suspensions and emulsions) are also applied in some cases. Microencapsulation of active ingredients for controlled and sustained release represents a more sophisticated approach to the formulation of agrochemicals. Solid formulations of wettable powders, grains, granules and tablets are also used in many applications. 

---