Production of benzyl-based esters from used soybean cooking oil as renewable plasticizers for flexible PVC films: Exploring new applications for lipases in emerging technologies

The objective of this study was to produce new and renewable bio-based plasticizers from used soybean cooking oil (USCO). First, USCO was completely converted into free fatty acids (FFAs) using lipase from Candida rugosa. Next, these FFAs were enzymatically esterified with benzyl alcohol in solvent-free systems. During this stage, we assessed various factors that influenced the reaction, achieving a maximum FFA conversion of 94 % within 40 min using lipase Eversa® Transform 2.0 immobilized on poly(styrene-divinylbenzene) beads. This biocatalyst maintained full activity across eight consecutive esterification cycles. In the third step, epoxy groups were introduced into the chemical structure of the synthesized benzyl esters through an in situ epoxidation process. The performance of these benzyl esters as plasticizers for flexible PVC films was then evaluated and compared to the petroleum-based plasticizer dioctyl phthalate (DOP). Incorporating epoxy groups significantly improved the compatibility of the benzyl esters with PVC, resulting in films with superior properties compared to those plasticized with DOP. This study provides valuable insights into the development of bio-based plasticizers as potential alternatives to commercial plasticizers. Additionally, the proposed process offers useful technical information for emerging applications of lipases in oleochemical processes.