Use of cationic surfactant to remove solvent-based ink from high density polyethylene surfaces

Abstract

Increasing space limitations for disposal of solid waste and shortages of raw materials for plastic have increased the need for recycling. However, printed plastic surfaces cannot be effectively recycled unless the inks are removed. The use of surfactants for deinking rather than organic solvents or chlorine bleaches is environmentally attractive. In this study, the effect of cationic surfactant concentration, pH level, process temperature, pre-soaking time, shaking time, and abrasion were investigated for blue solvent-based ink on rigid high density polyethylene surfaces. The cationic surfactant (cetyl trimethyl ammonium bromide) was effective only at concentrations above the critical micelle concentration (CMC) and at high pH levels (11.75 and above). Both below and above the CMC, ink removal was promoted by increasing temperature, pre-soaking time, and shaking time. The presence of an abrasive also helped to detach the loosened ink from the plastic surface. Solubilization appears to be an important mechanism aiding deinking.