Flash hydrolysis deinking of laser print using degradable toner resin

The choice of vinyl polymers as the plastic matrix for the pigment in xerographic toner did not anticipate the deinking thrust which has swept the paper industry. The hydrolytic stability of the carbon-carbon bond in vinyl and diene copolymers has prevented the use of a plastic degradation strategy for toner removal. New toner resins based on alkali degradable plastics have been shown to allow up to 97% toner removal. Based on polyimide and polyesterimide toners (either magnetic or non-magnetic) developed by Xerox, this study uses flash hydrolysis in the presence of 0.5% alkali to repulp. The process operates on 200-300 second batches at 190−210°C. The best results were obtained using alkaline repulping and magnetic deinking coupled with washing. The alkali also inhibits the hydrolytic degradation of cellulose although it negatively impacts the brightness. Thus the use of a polymer resin containing a chemically sensitive function allows conversion of the toner to pigment fragments and water soluble oligomers. The former is best separated by magnetic deinking while the latter is removed by washing.