New green surfactants for emulsion polymerization

Nonylphenol ethoxylates (NPEOs) are widely used as surfactants for emulsion polymerization and for post adding stabilization for latex applications in formulations with high filler content. However, the current exposure situation of NPEOs in Europe gives rise to environmental concern, despite of the fact that some industry associations have already pro-actively taken measures to phase out these chemistry of their products, e.g. the European detergent industry (AISE) by a voluntary commitment. As a consequence, the EU Commission has recommended to implement a risk reduction strategy, which foresees the ban of all applications leading to direct emissions to waste water and strict emission controls for all other technical processes using NPEOs as surfactant. The effectiveness of the risk reduction measures will be monitored by the authorities. In case that the environmental concentrations of NPEOs and their metabolites do not decrease by at least 70 percent, additional risk reduction measures for technical applications are planned. In one of the major fields of application, alkyl phenol-free emulsifiers with a more favorable ecological profile are becoming key ingredients for eco-friendly emulsion polymers and polymer dispersions: the Disponil^® AFX-Series (Cognis) is a NPEO-free surfactant system for emulsion polymerization and polymer dispersant also as a supposition for getting the European eco-label for indoor paints and varnishes.

These new non-ionic surfactant system exhibits an effective performance during polymerization and as post reaction stabilizers. These products are environmentally compatible, mostly derived from natural renewable resources and readily biodegradable. The underlying chemistry is in compliance with relevant indirect food contact applications [BfR recommendations, respectively, FDA CFR 21 (federal drug administration)], and a dossier to register the surfactants in the positive list of the EU Directive 2002/72/EC for application in plastic has recently been submitted.

Clear, high solid liquids at room temperature, these surfactants are easy to handle and very effective with regard to controlling particle size, film properties and overall latex stability. This paper summarizes their chemical and surface properties, as well as their performance in model emulsion polymerization formulations for architectural coatings.