Stretchable Paper—Yes, Really! 

Paper that can stretch much like plastic opens up a whole new world of product opportunities for the industry.

MARK RUSHTON

It’s only when you see it right in front of your eyes that you realize just what an incredible transformation takes place with the Papermorphosis system—an inline innovation for papermakers being marketed by Italian company Gruppo X. Incredibly, and in a very short space of time, white, conventional papers transform into a stretchable, fabric-like material that acts like thin plastic.

This dramatic transformation of a reel of paper took place in front of Paper360° at Innventia’s FEX-paper machine pilot plant in Stockholm, Sweden, home to much R&D and many complex innovations going on in the forest products industry. Papermorphosis is a classic example of the mounting fervor for making everything possible out of renewable wood fiber and replacing fossil fuel-derived plastic products at every opportunity.

But what black art or chemical reaction could ever make conventional, easy-to-tear paper act this way? Turns out, no chemicals, and no black art—just a bit of imagination mixed with some genius applications of practical physics. The basic theory of the Papermorphosis technology is to micro-shrink the paper in the machine direction (MD) on one unit, and in the cross direction (CD) on a second unit, first using special cylinders after the forming section and before the drying section in a paper machine—and then presto! stretchable paper is delivered onto the reel.

Gruppo X inventors Giorgio Trani, Marion Sterner, and Federico Cariolaro (owner of an Italian paper mill), have already seen some success while developing fiber-based packaging for consumer products over the past 25 years. Initially starting out with work for major brand owners Unilever and Nestle, the company has also worked closely with TetraPak. Trani, inventor as well as general manager of Gruppo X, says: “Initially we were working as consultants for Unilever, trying to find ways of saving money in the packaging area for ice cream. We were working on packages that filled from the inside, ones where the ice cream itself could help shape the package.

“As our work continued, it was clear that the preferred substrate for the brand owners was paper, not plastic, and we continued our work in the development of paper molding,” adds Trani.

The culmination of all the research and innovation in paper and board molding led Gruppo X to develop Mould Paper for packaging papers, which is now licensed exclusively to BillerudKorsnäs in Europe under the tradename Fiber-Form. Again, a purely mechanical application retrofitted online, the technology results in up to 20 percent stretchability of paperboard, enabling entrance into the fast-growing fiber-based 3D packaging arena.

MANY MORE APPLICATIONS

But there is a lot more that can be done with stretchable paper, says Mikael Magnusson, senior research associate, paper physics, Innventia. “Paper sometimes comes up short due to its properties, but along comes an innovation such as Papermorphosis and suddenly it opens up a world of opportunity. The technology allows paper to be highly deformed in all directions, which in turn delivers a whole lot of other product possibilities.”

Highly Deformable (HD) or 3D paper is the result obtained by stretching the paper. Gruppo X has recently taken this technique to another level by enabling the stretching of paper in both directions in the papermaking process. Initially it could only be achieved in the direction of the paper grain; now it can be done across the grain as well, using its XXL and XXBelt technology, which are patents of Gruppo X.

GETTING TECHNICAL

When both the MD and CD techniques are applied to the paper after the former, and before the dryer, the final paper on the reel becomes up to 20 percent stretchable, and results in paper that has an increased strain and does not easily tear. In technical terms, the technology increases the tensile energy absorption (TEA). “In the past there has been technology available that stretches paper in the MD, for instance in sack paper production,” says Sterner, head of R&D at Gruppo X. “But to really increase the opportunities, and allowing for actual custom-made and tuned stretchability in all directions and a balanced TEA, MD and CD applications need to be combined.

“In the trials we have done, we aimed to push the technology to the limits and increase the stretchability and TEA of paper as far as we could, and actually 20 percent or more is probably too much stretch for most applications,” adds Sterner. “But it does allow all sorts of opportunities to be developed for other products.”

The ability to fine-tune and adjust to the exact amount of stretchability needed is an important factor, as it can allow for the use of differing fiber—for instance, short or long, or even recycled raw material. It also allows papermakers to deliver paper to converters and end users that are bespoke to the needs of the final application, such as paper that only needs to stretch by 2-5 percent, for wrapping around a shoe box.

“An interesting feature of the XXL-unit (working in CD) is not only to increase stretch, but also to pre-stretch/pre-extend a paper, just a few percentage points, but interesting to recover a bit from the loss of trim width due to drying. Or standard paper qualities could be produced with reduced costs on furnish or refining,” adds Sterner.

Other applications for the Papermorphosis innovation could be kraft paper, 3D formable paper for furniture and automotive applications, highly stretchable but also highly absorbing and fluffy tissue, and improved recycling paper. “Our studies at the moment are focussed on classical but extraordinary corrugated board,” says Trani.

“Ultimately, our goal is to help papermakers make the best possible paper out of the poorest quality fiber,” he concludes. “With our two units, the XXL and XXBelt technology with both MD and CD capability, we are continually trialling new paper grades. We would like to improve different papers, even where super-stretch is not needed—making small, significant adjustments that are not even visible to the final customer, but are of help for many papermakers.”

Mark Rushton is senior editor, Europe and Asia, for Paper360°. Reach him at mrushton@tappi.org

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Innventia and Gruppo X

Innventia has been working closely with Gruppo X since 2011, running production trials on fine-tuning of the technology, Mikael Magnusson, senior research associate, explains: “Our collaboration with Gruppo X began around five years ago when we at Innventia were on our usual mission to find and support interesting R&D going on in the

forest products industry. We discovered Gruppo X on a trip to Venice where they were initially carrying out trials on a hand-driven paper machine.

“When we installed the pilot machine in Stockholm in 2015, that was the perfect opportunity to put Papermorphosis to the test. It was not long before a big wooden box arrived with the XXL and XXBelt units on board.”

The pilot units owned by Gruppo X at the Innventia site are modular and can be used both separately or together with the FEX pilot paper machine, and are available for customer and supplier trials.