Deinking of water-based ink printing from plastic film using nonionic surfactants

When plastic film packaging is processed for reuse, residual ink colors the polymer and makes the polymer less stiff, weaker, and denser than the original material. These problems can be avoided if the printing is removed from the plastic film surface. In this study, a commercial polyethylene film with water-based ink printing was deinked (the ink was removed) using nonionic surfactants under a variety of conditions, and the effect of some parameters related to the deinking process were quantified and optimized. Nonylphenol polyethoxylate, ethoxylated alcohol at a pH of 10, and ethoxylated amine at either acidic, neutral, or basic pH level were identified to be effective at deinking. The hydrophiliclipophilic balance (HLB) value and the cloud point are useful parameters for characterizing the effectiveness of nonionic surfactants. For optimal deinking, the HLB of the nonionic surfactants should be as small as possible or the cloud point as low as possible without the deinking temperature substantially exceeding the cloud point. Information related to scaleup of the process was also developed. Soaking plastic film in surfactant solution prior to mechanical agitation significantly decreased the needed agitation time to achieve a given level of deinking. Deinking decreases as the plastic/solution ratio (consistency) increases, and cutting plastic film into smaller pieces improves the deinking at moderate consistency. Increasing agitation speed also enhances the deinking. Experiments performed with pilot-sized paper deinking apparatuses demonstrated that deinking of plastic film using surfactants is technically feasible.