Paper recycling optimized by bio-digestible barrier coatings, DS Smith and Aquapak-commissioned study finds

01 Nov 2021 --- DS Smith and Aquapak are highlighting a new study demonstrating Hydropol coatings increase paper recycling rates and fiber yield without compromising functionality. The Paper International Technology Association (PITA) study suggests bio-digestible barrier coatings provide a viable new packaging alternative to conventional plastic coatings.

Hydropol is a fully soluble, bio-digestible barrier polymer that can be adhesive or extrusion coated onto paper. The polymer can bring many benefits to fiber-based packaging, including oil and grease resistance together with a high gas barrier.

The coatings have also been shown to increase some paper strength properties, including tear, burst, puncture and tensile strength, allowing coated or laminated papers to be heat-sealed for form, fill and seal fiber packaging applications.

In the DS Smith and Aquapak-commissioned study, Hydropol was shown to provide “real improvement” against current regulations that allow the “recyclable” label to be used if there is up to 15% unrecyclable material in the product.

The independent research, “Considerations for process, product and environmental fate testing of soluble bio-digestible barriers for paper and board packaging,” found new barrier technologies like Hydropol improve paper fiber separation for recycling and reduce plastic coating dependency.

Solving paper recyclability
DS Smith and Aquapak have been working together to solve the non-recyclable paper packaging issue, the use of which has increased as the industry has moved to replace conventional, hard-to-recycle and single-use plastics.

Hydropol coatings have also been shown to increase paper strength properties.This transition has resulted in a wide va­riety of fiber-based packaging formats combined with alternative functional barriers being introduced into the recovered paper recycling streams. However, the materials currently being used to give paper the packaging functionality required for products such as food, drink and household goods are not easily recyclable.

The lack of recyclability means paperboard is rejected by paper mills that cannot process the paper and plastic combinations, and the materials end up in incineration or landfill.

Aquapak has developed Hydropol, a com­mercially available fully soluble, bio-digestible barrier polymer to overcome the recyclability issue. Hydropol can be adhesive- or extrusion coated onto paper and brings several benefits to fiber-based packaging, including oil and grease resistance together with a high gas barrier.

The coating is also non-toxic, marine-safe, dissolves in water but still provides the functionality required for food, drink and household product packaging. Dr. John Williams, Aquapak’s CTO, previously discussed Hydropol in detail with PackagingInsights.

Recycling mill compatibility
The PITA study tests show Hydropol is compatible with the processes used by high volume recycling mills and enables high fiber recovery while reducing insoluble single-use plastics, which are ejected and sent to landfill or waste-to-energy.

The results obtained in the study provide packaging designers with “a clear route” for meeting the Paper-based Packaging Recyclability Guidelines set out by Cepi, the European association representing the paper industry. The guidelines are:

• Ensure the paper fraction of the packaging breaks down into single fibers when pulped within a specified timeframe.
• Give preference to polymers and other sealing agents that can be dealt with efficiently by the paper mill process and effluent treatment systems and do not compromise the finished product, the production process or the environment while being recycled.
• A previous study shows Hydropol has also been shown to increase some paper strength properties (tear, burst, puncture and tensile strength), allowing coated or laminated papers to be heat-sealed for form, fill and seal fiber packaging applications.

“The new research is hugely important for the packaging industry as it proves they now have an alternative solution to existing plastics, which is commercially available and, crucially, does not compromise on functionality or the end-of-life of the materials,” notes Mark Lapping, Aquapak’s CEO.“It is now up to the industry to embrace the new technology,” says Mark Lapping, Aquapaks CEO.

“It is now up to the industry to embrace the new technology available to them and create a new generation of packaging which meet the needs of the circular economy.”

“Its clear materials used in paper-based packaging have to be designed into the packaging with recycling in mind from the start,” adds Nick Thompson, materials development director at DS Smith Group R&D. “This [recycling priority] is why DS Smith developed circular design principles; to ensure repulpability, recyclability and no negative impact on the end of life of the materials used.”

“It seems like the Aquapak Hydropol product during recycling has now been shown to help fiber separation and can itself be eliminated from the process with no negative impact and with no need for finding an outlet for unwanted waste material, such as difficult to recycle plastics.”

DS Smith recently used its Circular Design Metrics for the first time to design and manufacture fiber-based packaging for a limited edition beer collection brewed with surplus bread. The COP26 initiative led by Toast Ale highlights the damaging impact of food waste on climate change.

Edited by Joshua Poole