NC State
Kemppainen, K., Körkkö, M., and Niinimäki, J. (2011). "Fractional pulping of toner and pigment-based inkjet ink printed papers - Ink and dirt behavior," BioRes. 6(3), 2977-2989.


Large visible dirt specks and microscopic ink particles are released from the surface of recycled paper when pulping toner and pigment-based inkjet ink printed papers. The applicability of pulp fractionation during laboratory scale pulping was investigated without chemicals to prevent the redeposition of small ink particles to fibers, and furthermore to break down the large toner fragments. Reference pulping was performed without fractionation stages, and the two pulping procedures were compared in terms of bound ink and dirt speck content. The results show that while the microscopic ink particles redeposit to the fibers at the very beginning of conventional pulping, the redeposition can be minimized by removing the detached ink particles from the vicinity of the fibers as soon as they have been detached. Thus, it is recommended to remove the ink from the pulp before a substantial defiberization level is achieved. In addition, the dirt specks broke down more efficiently in fractional pulping than in reference pulping at the same pulping consistency.
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