Use of surfactants to remove water based inks from plastic films

Direct reuse of plastic film with printing results in a colored polymer, wh ich is less stiff and weaker than the original plastic upon re-extrusion. T here is substantial economical and environmental incentive to remove the in k (deink) from heavily printed plastic film so that it can be reused to pro duce clear films. In this study, a commercial polyethylene film with water- based ink printing was deinked using different surfactants under a variety of conditions. At a pH of 12, water (containing no surfactant) can achieve about 90% deinking, but less basic solutions are less effective; at a pH 10 and below, insignificant-deinking occurs. Solutions of cationic surfactant are the most effective at deinking, showing high efficiency at surfactant concentrations both above and below the critical micelle concentration (CMC ) over a pH range of 5-12. Amphoteric surfactant is effective above the CMC over a wide pH range. Both anionic and nonionic surfactants are only effec tive at deinking above the CHIC at very basic conditions, with anionic surf actant being only slightly better than just water even at these high pH lev els. The cationic surfactant is most effective and the anionic surfactant i s least effective, possibly because the binder is an acidic acrylate with a negative charge. (C) 2001 Elsevier Science B.V. All rights reserved.