Clean synthesis of epoxy plasticizer with quaternary ammonium phosphotungstate as catalyst from a byproduct of cashew nut processing

Abstract

The toxic petroleum-based phthalates account 80% of the total plasticizer consumption in China. Conventional methods for preparing epoxy plasticizers produces a large amount of waste water. Furthermore, cardanol (a byproduct of cashew nut processing) has the potential to be an economic alternative for producing fine chemical products. Here we reported a strategy for acid-free catalytic production of epoxy plasticizer using renewable waste material cardanol as starting material and quaternary ammonium phosphotungstate as catalyst. The optimum epoxidation reaction parameters were investigated and the epoxy value of epoxidized cardanol based plasticizer was 5.2% at optimal reaction conditions. Remarkably, the catalyst was recycled and the percent recovery in the first recycle was 89.0%. Performances of plasticized PVC films showed that epoxidized cardanol based plasticizer improved thermal stability and decreased the glass transition temperature of PVC. Plasticizing efficiency of epoxidized cardanol based plasticizer reached 82.2%. Epoxidized cardanol based plasticizer is biologically safe without acute toxicity and showed more excellent solvent resistance and lower volatilization than dioctyl phthalate. In conclusion, a cleaner environment-friendly plasticizer derived from a waste material was produced by acid-free catalysis. The strategy introduced renewable waste material cardanol into the environment-friendly plasticizer production to substitute dioctyl phthalate and had potential application value to reduce pollution and improve human health.