Original scientific paper
https://doi.org/10.25027/agj2017.28.v29i3.163
Optical properties of deinked pulp containing thermochromic offset inks
Sonja Jamnicki Hanzer
orcid.org/0000-0002-1064-8578
; Faculty of Graphic Arts University of Zagreb, Zagreb, Croatia
Marina Vukoje
; Sveučilište u Zagrebu Grafički fakultet, Zagreb, Hrvatska
Matea Zadro Tovernić
; Faculty of Graphic Arts University of Zagreb, Zagreb, Croatia
Abstract
This paper evaluates the efficiency of thermochromic offset prints recycling using deinking flotation method. Since offset thermochromic inks differ in their composition from conventional offset inks, the aim of this re¬search was to determine how effectively they can be recycled. In the experimental part of the work, the labo¬ratory printing of two thermochromic inks was conducted. For both types of inks, white uncoated paper was used as a substrate. After accelerated aging, the prints were mixed in equal proportions and then recycled in laboratory conditions, by means of deinking flotation. During the recycling process, handsheets and filter pads were prepared from the pulp obtained before and after deinking flotation. Handsheets and filter pads were also prepared from unprinted paper that was used as printing substrate, in order to obtain reference samples. The deinking flotation efficiency was evaluated by calculating the flotation loss, ash elimination, pulp’s brightness and whiteness increase and determination of residual ink area. The obtained results indicate that thermochro¬mic prints are poorly deinkable. A small increase in deinked pulp’s brightness and whiteness (approx. 7% and 11%) is noticed. The image analysis shows that flotation deinking managed to eliminate around 40% of the to-tal dirt area of thermochromic ink.
Keywords
thermochromic ink; deinking flotation; optical properties; colour change
Hrčak ID:
227400
URI
Publication date:
5.11.2019.
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