Epoxy Methyl Soyate as Bio-Plasticizer: Two Different Preparation Strategies

Due to the recent rise in production costs of biodiesel and considering the necessity to use environmentally friend production way, bio-plasticizers obtained from vegetable oils were developed. Bio-plasticizer are essentially constituted by epoxidized vegetable oils (EVO) (rich in unsaturated compounds as soybean, sunflower and rapeseed oils). These kind of products have got good plasticizer properties and are easily biodegraded by microbial agents. The main advantages of these additives are their low diffusion coefficients in the polymeric matrix and a very low volatility. In recent years epoxidised fatty acid methyl esters (EME) have been developed, because they are more soluble and confers better flexibility to the plastic even at low temperatures. The main problem associated with these products lies in their content of satured methyl esters. This fraction cannot be epoxydised and has got a very low affinity with the polymeric matrix, so that tends to migrate at the plastic surface giving not desired properties to the final products. The aim of this work is to find the best reaction conditions in terms of epoxide yield, using acetic acid and hydrogen peroxide, and to apply these condition either to 1) a fractionated biodiesel (i.e. without satured esters) or 2) to soybean biodiesel in order to obtain EME and then distillate it to remove the unreacted esters. Both the strategies were studied by experimental batch epoxidation test and vacuum distillation runs. A better bio-plasticer was obtained (epoxide number of about five) using the first strategy, i.e. by a distillation of starting biodiesel, perfomed at 0.5 torr using a two equilibrium stage batch distillation apparatus, followed by the epoxidation reaction.