The deinkable ink is already on the market
Siegwerk's cooperation with the research department of INGEDE member Stora Enso began as early as 2017. Mean-while, the deinkable LED UV colour is on the market. But the development continues: "We see even more potential," says Glaser, Head of Technology Sheetfed at Siegwerk. "We are working on other deinkable UV and LED UV products."
Other UV-curing inks rarely meet the criteria for good re-cyclability. Almost all previously studied colours leave signif-icantly too many ink particles in the recycled paper. Paper printed with UV-curing inks can thus impair the deinkability of entire recovered paper batches. Therefore, such UV prints must be collected and disposed of separately at the point of contact where they occur (for example, printers’ waste). How-ever, what once left the print shop can practically no longer be recognized and separated during collection and recycling.
Vegetable oil not always good: Inks to be tested carefully
Different inks behave differently in the deinking process. To-gether with INGEDE, colour manufacturers are therefore look-ing for ways to replace poorly deinkable inks with more recy-cling-friendly solutions. Cross-linked particles due to their size, flexibility or surface properties can neither be separated
mechanically (screens) nor by flotation. Also some vegeta-ble-oil based inks create problems, because they polymerise when drying and cling closely to the fibres – this again leads to dirt specks in the recycled paper.
Another cross-linked challenge is polyethylene liquid toner (HP Indigo), currently used for most of the photobooks. This is a thin plastic film rather than a conventional printing ink. During the recycling process, this film breaks into snippets, which cannot be removed sufficiently. These snippets have already led to significant damage in a paper mill, since then photobook (and other HP Indigo) printer waste must not be mixed with graphic paper for recycling and at best be used for corrugated board.
INGEDE (International Association of the Deinking Industry) is an association of leading European paper manu-facturers founded in 1989, celebrating 30 years of support for paper recycling and deinking in 2019. INGEDE aims at promoting utilisation of recovered graphic paper (newsprint, magazines and office paper) and improving the conditions for an extended use of recovered paper for the production of new graphic paper, hygiene paper, and white top liner and folding boxboard.
(https://www.ingede.com [1])
