Separation of toner particles by utilizing charging properties for material recovery and reuse

The shift in demand towards full color documents is changing the system of toner use. Unlike waste toner from monochrome xerographic machines, mixed color toner waste can not be recycled back into the manufacturing process. To address this problem, the current state of the conventional toner manufacturing process was examined. A life-cycle inventory (LCI) was performed on a specific type of black toner. The results from this analysis showed that the majority of the solid waste produced (95%) are associated with post-toner production processes. The LCI results also show a 29% reduction in virgin material use and a 24% reduction of solid waste production over the life-cycle when waste toner is recycled. Without a method of separation, full-color xerographic devices would lose these reductions.; To address this problem, the separation of particles based on their charging properties was investigated. Experimental work examined the separation of a mixture of magenta and black toner samples in a charge spectrograph. Allowing for a contamination level of 2.5%, the best results determined experimentally were for the mixed toners magenta without charge control additives and 8% carbon black. The tribocharge difference between the two toners was 22 muC/g and the distributions for both toners had minimal overlap, allowing for recovery of 99% of the black toner and 100% of the magenta toner. Overall, however, the recovery potential was on the order of 20-50% of each color toner.; In addition to the experimental work, a computational model of the charge spectrograph was developed in order to examine system and material properties that affect the separation. The charge spectrograph is an instrument used to measure the mobility and distribution of charged particles when placed in an electric field. The results from the model spectrograph determined that varying the toner particle properties such as particle size distribution, particle size, and tribocharge values would have a direct effect on the capacity to separate black and magenta toner particles. Reducing the overlap between the toners allows for maximum separation. The spread of the area of particle deposition could be reduced by reducing the toner particle size distribution. Increasing or decreasing the tribocharge of the particles results in a proportional shift in the particle deposition location. Changes in the particle size also shifted the location of particle deposition. Combinations of the above particle modifications were shown to improve the separation of model particles.