New Technologies Aim to Eliminate Adhesives in Recyclable Paper Packaging

It's quite literally a sticking point.

While paper or cardboard packaging might on its own be recyclable, the presence of a label, a seal or a coating can negate that.

That's because non-recyclable adhesives, or "stickies" as they are known as in the industry, can cause damage to recycling machinery, make the resulting batch of recycled paper inferior, or even cause a batch of paper to be recycled to be rejected, according to scientists at NC State University.

And that's a shame as paper is one of the most recycled materials in Europe - with around 74% of paper and board consumed in 2024 being recycled.

And European authorities are spurring firms to do better.

In August, a new Europe-wide packaging and packaging waste regulation (PPWR) kicks in ordering that all packaging should be minimum 70% recyclable by 2030, rising to 80% from 2038. In addition, German law will also require stricter reporting and licensing fees.

So, tackling stickies would be helpful. One solution has been to develop water soluble adhesives.

But what if you could skip the adhesive altogether?

That's the idea that three firms from Germany - Fraunhofer, Herrmann Ultraschall, and Henkel - have come up with.

It's no coincidence they are all German, as the country is known for its Packaging Valley, a hub for the packaging industry.

Their efforts to innovate are partly a bid to satisfy ever tightening regulation around commercial recycling, and rising fines for those who fall foul.

With that in mind, German research organisation Fraunhofer established the PAPURE project in 2023 to develop a laser-based heating process that can seal paper packaging without an adhesive at all.

From September, when the project is set to officially close, Fraunhofer hopes to find an industry partner to take the technology to market. Fraunhofer researchers exhibited their work at the Interpack packaging trade show in Dusseldorf in May, and are hopeful that the interest they attracted will come to fruition.

"There are not really many paper sealing technologies without any foreign materials, so it's a great technology and we feel it's likely that we can bring it to market," says researcher group leader Fabian Kayatz.

"If we are optimistic, we will have the first solution out in two years."

Also in 2023, engineering firm Hermann Ultraschall bought the rights to develop a patented ultrasonic paper sealing technology, a process which it likens to welding.

"We are really actively at the moment in discussion with several really big players in the market with the focus of bringing this technology into mass production," says Michael Baumann, the company's head of business development packaging.

"One customer told me this is an innovation they have never seen before."

Yet these seemingly simple solutions stem from complex technology, so naturally, there are challenges.

Firstly, it's not as simple as simply getting product manufacturers and packaging companies to swap out their old packaging for these new options. It requires updating, and in some cases, completely replacing, existing machinery, which can be costly and time consuming.

"The packaging industry has existing machines which are all designed for glue materials. Some kind of redesign is probably necessary, and this is our biggest challenge," says Hermann Ultraschall's Baumann.

Yet Volker Franke, also a research group leader at Fraunhofer, is confident that those existing machines can be modified by integrating the laser module that PAPURE has been developing.

They both acknowledge that the production rate is also currently much slower than that for paper packaging that uses adhesives, but Franke says a key benefit PAPURE is selling is fully automated production, which he believes can continue to be developed for speed.

The other issue is that the technologies don't work on all types of paper.

"It's not possible to bond every paper material," Baumann confirms. "But we are actively in discussion with paper manufacturers about how they can produce a raw material in a way that makes it easy to bond."

PAPURE has also yet to find a way to apply their laser sealing technology to food-grade packaging, which needs a coating to protect the item. This tends to be why plastic is often favoured for packaging food.

But this is something Henkel, with both a consumer brand division, and adhesive technologies division, has cracked.

In February, Henkel announced the launch of the first cold seal solution that works with barrier coated paper, which is both recyclable and suitable for food products.

Barrier paper can be a difficult surface to bond, and using heat isn't suitable for heat sensitive food products like ice cream or chocolate. Hence the cold seal solution, in which enough pressure is applied for the barrier coated paper to be bonded against itself.

Jamie Stone is a packaging expert at global innovation consultancy PA Consulting. He explains that there's a lot that can go wrong when trying to marry recyclable paper packaging with a compatible sealant.

"For example, take a yoghurt pot made from folded paper fibre. You need a barrier layer between the paper fibre and the yoghurt to protect the shelf life, and you also need a secure lid. So, you're immediately dealing with multiple surfaces that all have to work together," says London-based Stone.

"If the barrier layer is a liner, which is best for recycling, it needs to be very thin. It also needs to bond really well to the paper fibre part. If it doesn't stick well enough, you risk pulling out the lining with the lid still attached – leaving a messy, partially sealed pot of yoghurt, which is clearly not a good consumer experience."

But there's also a bigger problem at play than a little glue. When paper doesn't get recycled it's more likely to be because of poor collection and sorting methods, argues Ambarish Mitra, co-founder of Greyparrot, a waste analytics platform used by big waste collection companies, as well as local authorities.

"A lot of paper and card doesn't get recycled because it gets dirty or mixed in with other rubbish before it even reaches a recycling plant, not because of the glue holding it together," says Mitra.

PA Consulting's Stone agrees, though, that new paper sealing technologies are "a smart place to start."

"We'll see the real sustainability benefits start to scale as technologies like these mature and begin to handle more complex, high-barrier paper-based packaging, while matching the speed and cost of plastic packaging lines," he concludes.