Is Inkjet Still a Challenge for the Paper Recycling Process?

Axel Fischer, INGEDE

Everybody wants to go green, also the printers. Producer responsibility in France: Printers are advised to establish a separate collection system for HP Indigo prints that disrupt recycling.

Inkjet sounds good, printing with water and some dye or colorant, but is that automatically green?

Paper recycling has a different role in Europe and in the US – in Europe, about half of the paper collected goes into printing and writing grades, into new white papers. In the US, almost all of it goes either into packaging or is exported to China. But now even China changed the rules and has set up some quality standards für paper for recycling.

Deinking is the key process in paper recycling for white paper, and it becomes increasingly important also in the production of packaging – for the production of the white top layer that more packaging material need to be printed to advertise the content.

So there are two steps, the removal of the ink from the fiber, and then the removal of the ink from the aqueous system, to leave only the clean fibers.

Offset and gravure inks perform well here, under the mechanical stress in the pulper or drum the ink layer breaks into particles of just the right size and hydrophobicity to separate from hydrophilic fibers.

Inkjet inks are different – in the beginning there was just water with some soluble dyes, staining all the paper fibers, even small amounts of inkjet printed papers had the potential to ruin a whole load of paper for recycling, just like the red sock in the washing machine with white underwear.

Some ink and inkjet manufacturers have learned the lesson. It goes hand in hand with increasing quality demands for inkjet prints. You don’t want the ink to bleed into the fibers, you don’t want two droplets of different color to merge indistinctively. So what can you do? You prevent the ink from bleeding into the fiber by letting pigments coagulate with neighboring particles right after jetting. There are different ways to do that (and they will be presented). As a result, you have a larger particle sitting on top of the fiber. And this particle is much more likely to be removable in the recycling process. So here is a windfall profit. Not every development leading to better deinkable inkjet ink was meant to improve the environmental properties.

But there are also developments that have been discontinued or encouraged in close cooperation with the deinking paper industry after looking into the deinkability in a very early stage of the development.

The World Beyond Inkjet, a Quick Look

The world is not only inkjet, a few thoughts about other printing technologies and their properties from the view of the recycling industry. What is the Landa technology? There is inkjet involved, but it is also based on Benny Landa’s earlier liquid toner technology. There are somwe differences and some things in common.

What about UV curable inkjet? There are severe problems in recycling UV curable offset inks, especially the new LE- and LED-UV inks that are frequently greenwashed just because the lamps consume a little less power. But there are also some interesting (and completely unexpected) developments when combining inkjet and UV.

And a few words about INGEDE: This organization of the deinking paper mills has developed methods to evaluate the recyclability of printed products, reliable and reproducible methods, that have become part of several ecolabelling processes in Europe and even some Asian countries.