Transferring the patent for the ultrasonic sealing process of uncoated paper will bring market gain

Syntegon has transferred the patent for sealing uncoated paper with ultrasonics to Herrmann Ultraschall for it to further develop this sustainable technology.

Until now, additional resources in the form of potentially environmentally unfriendly adhesives or staples have been needed to connect uncoated paper reliably. Now, paper can be joined much more sustainably using ultrasonics alone. The technology has been successful under laboratory conditions, but the new patent holder is working to establish it on an industrial scale for the first time.

To do this, Herrmann Ultraschall will test the process with customers in its ultrasonic laboratories on how to further optimise it in various applications.

“Previously, we needed at least a small amount of plastics in the material to seal the paper with ultrasonics – now we can do without it completely,” explains Thomas Herrmann, CEO at Herrmann Ultraschall. “This opens up new possibilities for the eco-friendly design of packaging and on the way to a functioning circular economy,” he says. “We are delighted that, together with Syntegon, we have created the conditions to bring this innovation to series production.”

“With the Herrmann Ultraschall Group, we have found a competent partner who will bring this promising technology to all packaging applications with fibre-based materials,” says Dr Johannes Rauschnabel, head of advanced development at Syntegon. “The ultrasonic expertise of our partner will create the conditions for a wide acceptance of the process in the market.”

Ultrasonic welding of paper works in a similar way to plastics but with one crucial difference: the material must be moistened before the welding process. The welding tool, the sonotrode, transmits ultrasonic vibrations to the paper, causing the fibres to separate and form new bonds at the point of contact between the paper layers.

The frictional heat generated between the materials causes the applied moisture to evaporate without damaging the paper. This produces a high-strength and visually flawless connection within a very short time.

The application areas for ultrasonic paper welding are diverse: from primary packaging, such as fruit trays made of thin cardboard, to secondary packaging, in the form of paper bags. Besides the savings in joining materials, the primary advantage for companies is the low energy input, fast process cycles, and shallow wear of the welding tools. In addition, uncoated paper can be recycled much more efficiently, further improving the sustainability balance of the packaging.

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