Going Green

Inkjet De-Inking a Topic to Dye For

By Richard Romano on November 15th, 2011

Via Printweek, de-inking (or deinking, if you prefer) was the topic du jour at both the CTP’s Technical Conference on Deinking of Digital Prints in Grenoble and IMI’s 19th European Ink Jet Printing Conference in Lisbon. As commercial inkjet printing ramps up, one of the environmental issues it generates is that of de-inking paper for recycling. After all, when you recycle paper, you have to get rid of the ink.

One advantage that offset ink has for recycling is that what makes the lithographic process work (hydrophobic, or water-repellent ink) also helps the de-inking process because paper fibers are hydrophilic (water-absorbent). As a result, when you wet the paper fibers, it’s easy to shoo the ink off them. So the de-inking process that paper mills use in the recycling process has been developed for offset (and gravure) inks which comprise the vast majority of the papers out there. However, inkjet inks are typically water-based, and in current de-inking processes (particularly the flotation process), are hard to remove, can contaminate the system, and irremediably stain the paper fibers. The analogy is laundering bright colors with whites–we’ve all had a brand new red shirt turn white socks or underpants a lovely shade of pink, usually the day before gym class. (Some flexo inks have also provided de-inking difficulties.) So a lot of research is being done to try to develop a de-inking process that can handle inkjet. (Another problem is that the process will have to handle all kinds of printing inks–try getting consumers, recyclers, or paper mills to separate “offset” and “digital” printed papers.)

At present, inkjet accounts for a very small percentage of overall volume of reclaimed paper sent for recycling, but as WhatTheyThink and other industry publications have written at great length, that may very well change. Says the Printweek article:

Research body InfoTrends said it believed inkjet currently contributes around 7% of digital print volume in document printing, but the growth of production output is likely to increase the overall inkjet share to 13% by 2015. This could lead to a tenfold increase in the amount of inkjet print in the recycled waste stream, rising from 0.05% to 0.5% by 2015.

…

The DPDA-sponsored (the Digital Print Deinking Alliance) studies outlined how improvements can be made through changing deinking conditions; however, Fischer was sceptical about the feasibility of making changes to the current mill deinking model of flotation.

“Everything you do for inkjet will reduce the yield for offset,” he said, explaining that the current process has been developed for the hydrophobic ink properties of offset print, which makes up 90% of the waste stream going into these mills. Making changes to accommodate hydrophillic inkjet reduces the overall yield, and creates more waste because the fibres themselves are hydrophillic.

Turns out, though, that the solution may not lie in developing a new de-inking process, but rather develop inkjet inks that are more de-inking friendly. Other ideas include substrate coating that eases the de-inking process.

Two names to pay attention to are INGEDE (founded in 1989 by European paper manufacturers as the International Association of the Deinking Industry) and the Digital Print Deinking Alliance (DPDA, formed in April 2008 by Kodak Versamark, HP Inkjet, and Océ Inkjet), which earlier this year signed a letter of collaboration with INGEDE and are jointly conducting more research on de-inking processes. (The DPDA had some early success last year.) As Printweek reported, progress has been slow.