Paper Joining without Foreign Materials – Through Laser-based Material Modification (PAPURE)

Process principle of paper joining without foreign substances as well as possible applications.
© Fraunhofer IVV
Process principle of paper joining without foreign substances as well as possible applications.

Recyclability of Paper Packaging Limited by Use of Plastics or Adhesives

In the European plastics production of 55 million tons (2020), 40 percent alone is accounted by the production of plastic packaging. At the same time, plastic packaging accounts for about 60 percent of global plastic waste. The reduction of plastic in packaging is therefore of central importance from an environmental and sustainability point of view and has reached the highest priority worldwide.

The urgently needed expansion of existing and the establishment of new recycling capacities and adequate closed-loop logistics is a challenging, time-consuming and cost-intensive undertaking. One important alternative is the substitution of plastics with environmentally friendly, recyclable, natural fiber-based materials such as paper.

The joints required for the production and sealing of paper packaging, which are subject to certain requirements in terms of mechanical resistance and impermeability, have so far required the addition of foreign substances, such as plastics or adhesives. These unavoidable material impurities lead either to complex and cost-intensive recycling processes, to a reduction in the quality of the recycled material or to the loss of the paper for further recycling.

Paper Joining without Impurities for the Increased Demand of Paper Packaging

The new approach pursued in the project is to generate re-fusible glycosidic cleavage products on the paper surface by irradiating paper with a CO laser and to use these instead of the otherwise required plastics or adhesives to join the paper with industrially established heat contact processes. The intended project result is a processing technology that enables the production of paper packaging without foreign substances and demonstrates its functionality in an industry-oriented demonstrator. This will enable companies in the packaging industry, such as packaging material and machine manufacturers, as well as packers (producers) and retailers, to make a significant contribution to increasing the recyclability of paper packaging and to making their material cycles more efficient and cost-effective.

Competencies of Fraunhofer IWS

On the one hand, Fraunhofer IWS contributes its expertise in laser system technology and laser material processing to the project and, on the other hand, can draw on many years of experience with the modification of natural materials. From 2019 to 2021, the researchers worked on a binder-free joining process of paper. They generated reaction products that were already capable of melting by irradiating papers with a carbon monoxide laser (CO laser). The research team then “glued“ two papers in a heat-sealing process.

Video: Decomposition of Paper into Meltable Reaction Product by CO Laser Irradiation

© Fraunhofer IWS