Influence of redox initiator component ratios on the emulsion copolymerisation of vinyl acetate and neodecanoic acid vinyl ester.

Abstract

Redox initiated emulsion polymerisation of vinyl acetate and neodecanoic acid vinyl ester was investigated at temperatures ranging from −1 °C to 87 °C (initiation temperature between −1 °C and 60 °C), using varying molar ratios of the following redox components: l-ascorbic acid, tert-butyl hydroperoxide and ammonium iron(iii) sulfate dodecahydrate as a catalyst. The high flexibility of redox initiators enables product properties, as well as space-time-yield, to be adjusted as required. Polymers being products by process, it was presumed that modifying the conversion rate would lead to a different product. However, it was shown that the reaction rate is adjustable by varying the catalyst amount without changing the product properties, such as molecular weight, particle size, glass transition temperature and polymer structure, while reducing the overall process time by 40–86% (at equimolar ratios of reducing and oxidising agent). In contrast, variation of the tert-butyl hydroperoxide content resulted in changes of the molecular weight. The influence of the initiation temperature and of the redox system on the reaction rate was determined, enabling control over the reaction rate in the whole temperature range. Meanwhile, overall process times of approximately 2–240 min and high conversions of 90–99% could be achieved. Statistical modelling confirmed the results and facilitated predictions, enabling the conversion rate to be adjusted to the desired properties. The possibility of being able to adjust the conversion rate and product properties independently of each other creates additional degrees of freedom in process design.