Example of removing printing ink from plastic surface using quaternary ammonium-modified waste cooking oil.

The printing ink on the plastic surface greatly reduces the quality of recycled plastic products. In this work, quaternary ammonium-modified waste cooking oil (WCOQE) was fabricated, using waste cooking oil, epichlorohydrin and trimethylamine aqueous solution as raw materials, by ring-opening esterification and quaternary amination reaction. The synthesis conditions of WCOQE were optimized, and the structure and properties of WCOQE were characterized by FTIR, zeta potential and 1H NMR. Furthermore, WCOQE had excellent emulsifying performance, low kraft point, low CMC value, good foaming and stability, which could effectively reduce the surface tension of water, showing application potential in the field of plastic deinking. Importantly, compared with the waste cooking oil without deinking effect, the WCOQE had an excellent deinking performance on the ink on plastic surface, and the deinking efficiency could be improved by increasing the concentration of deinking agent, the deinking temperature, and prolonging the pre-soaking and stirring time. The results of AFM, EDS, optical photos and Leica microscope showed that the roughness changed significantly, and the ink molecules were gradually peeling off. This work highlighted the excellent potential of quaternary ammonium-modified waste cooking oil for the removal of printing inks on the plastic surface.