Direct printing: 100 percent rPET, 100 percent adhesion

“Direct printing and recycling? No way do they go together!” This is something that Zsolt Rozsnyai, who as product manager deals with digital decoration technology, keeps on hearing. But Krones is now rebutting this charge – twice over.

Printing on recycled containers ...

An EU law states that from 2025 all PET containers must contain on average 25 per cent recycled material, known as rPET. This regulation does not present a challenge for our stretch blow moulders. The Contiform 3 Pro, for instance, can even handle preforms that are made up entirely of recycled PET.

Things get tricky when it comes to direct printing, though: “The critical factor is the interplay between the material, the ink and the process parameters. That’s because these parameters affect how well the ink adheres to the surface of the packaging, for instance,” Zsolt Rozsnyai explains. And it’s precisely when it comes to material quality that the addition of recycled PET brings some unknowns into the equation: “With virgin PET, the material properties are easier to control because the quality is stable. With rPET, on the other hand, you are dependent first and foremost on what quality it is. That’s why we conduct tests with the recycling experts from Krones in order to specify the input material we need, so we can then configure the print settings on that basis,” says Rozsnyai.

It was just such tests that occupied a team of direct printing, recycling and container design experts this summer. That’s because Krones has set itself the goal of not just meeting the EU’s requirement, but actually exceeding it – by printing 100 percent rPET containers at the K trade fair in October. To that end container designer Timo Janssen created a special cylindrical 0.5 litre bottle for carbonated soft drinks that then had to be printed and subjected to rigorous testing. “After all, nothing could be worse than if the ink were to come off or it could be scratched off with a fingernail,” Zsolt Rozsnyai adds. The bottle celebrates its premiere at K 2019 in Düsseldorf, where the rPET container is printed live by a laboratory machine of our subsidiary Dekron.

… and recycling printed containers

When it comes to recycling the directly printed containers, the tables are turned: “In recycling, you see, it is of course essential to be able to remove the ink from the PET again without leaving any residue,” says Rozsnyai. And that is precisely what the US Association of Plastic Recyclers, or APR for short, certified for Krones back last year.

“That means beverage producers no longer have to worry about having a separate reusable materials cycle. The combination of material, ink and print application with the DecoType Select has demonstrated that these PET containers can flow into the recycling process,” Zsolt Rozsnyai explains.