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Siegwerk developing enhanced UV/LED offset inks

Printing inks provider Siegwerk has joined forces with INGEDE member Stora Enso, a provider of renewable solutions in packaging, biomaterials, wooden constructions and paper, to improve the deinkability of UV/LED cured prints.

First results of this cooperation have already marked a significant milestone towards more sustainable UV printing solutions in terms of deinkability in the paper recycling process, the parties explain. Based on these investigations Siegwerk has developed a new UV/LED offset ink system with “impressive” deinking properties on various paper grades comparable to the deinkability of conventional oil-based sheetfed offset inks, they say.

They explain paper that is printed with UV/LED inks shows poor deinkability as these inks form a solid, chemically and mechanically resistant layer after curing comparable with adhesive plastic layers. UV/LED inks are strongly attached to the paper fibre and therefore very hard to remove during the recycling process resulting in big colour spots in the recycled paper. It is important that the cured ink film is fragmented into hydrophobic particles as small as possible during recycling in order to become detached and more easily separated from the paper fibre.

“Present standard UV/LED inks often lead to large hydrophilic particles leaving visible traces on the recycled paper. That’s why we have focused our research resources on finding enhanced solutions for this problem and improving the recycling of UV cured prints,” says Thomas Glaser, Head of Technology Sheetfed at Siegwerk.

As low-energy curing UV inks (iron-doped UV, LED-UV) are gaining more and more market share, the problem has reached new dimensions and has increased the need for further advancements of UV inks and the UV printing process.

Since 2017, the partners have been investigated the deinkablilty of different ink formulations developed by Siegwerk and have examined the different inks’ behaviour with standard UV, LED-UV as well as iron-doped UV curing such as LE-UV, H-UV, HR-UV and LEC-UV.

“Our goal has been to develop UV/LED solutions for all UV technologies that show good deinkability similar to traditional offset and gravure inks without any loss in ink performance and printability,” adds Glaser. The deinkability has been checked using the INGEDE method 11 (01/2018) and the EPRC scorecard, the officially-approved industry standards for deinking testing and evaluation.

Based on their investigations, Siegwerk has succeeded in developing an enhanced UV/LED offset ink system with good deinking properties on both high- and low-weight coated paper as well as on uncoated virgin fiber-based newsprint (iNP).