Development of Direct Entry Deinking Processes for Ledger and Printed Bleached Board, 1991 Papermakers Conference Proceedings

Many paper and board mills using virgin pulp, unprinted pulp substitutes, or lightly printed secondary fiber can considerably reduce their furnish costs through the use of more heavily printed furnish. Use of these more heavily printed furnishes generally involves a deinking process. Conventional deinking methods involve mechanical treatment (washing or flotation) following repulping for separating ink particles from fiber. Implementing these conventional deinking methods involves a large capital investment. Therefore, it is desirable to develop deinking processes which require little or no mechanical treatment beyond the pulper.

A small scale pulping apparatus was developed to simulate the mechanical action of the hydropulper in the laboratory. Experiments were performed to determine the effect of surfactants, dispersants, and solvents on the disperson or agglomeration of ink particles in the pulper. Furnishes studied included heavily and lightly printed bleached board and laser (xerographic) or non-laser (impact) printed ledger. Brightness measurements and particle size analysis were used to evaluate deinking efficiency.

A method of "direct entry" deinking was developed for the deinking of heavily or lightly printed bleached board and impact printed ledger. In this approach the inks are broken up and dispersed into small enough particle sizes ( < 10="" microns,)="" so="" that="" the="" ink="" particles="" remaining="" in="" the="" sheet="" do="" not="" affect="" sheet="" quality.="" for="" laser="" printed="" ledger,="" a="" method="" was="" developed="" in="" which="" the="" ink="" is="" agglomerated="" in="" the="" pulper="" and="" then="" removed="" by="" cleaning="" or="">