Floatability of model offset ink

Model studies on the floatability of an offset ink suspension (without fibres) have been performed using a Hallimond tube and a standard calcium chloride-sodium oleate collector system. The average ink particle site was 1 mu m indicating poor floatability of untreated primary ink particles. This suspension was mixed with deinking chemicals, coating components and dissolved paper chemicals to evaluate their effects on flotation performance. The results were combined with data on agglomeration kinetics to determine important factors in the flotation deinking process. The importance of agglomeration was confirmed. The particles remaining after flotation were discrete primary ink particles. An interesting result was that no upper particle size limit for flotation was observed when ink particles were flotated without fibres, although particles larger than 200 mu m were present indicating the role of a fibre network for the retention of large particles. Parameters that influence the agglomeration and flotation rate are discussed as well as reasons why some particles do not agglomerate and flotate.