Two hands holding an open cardboard package.

Especially cardboard packaging held together at the sides or on the bottom by clips or adhesives can benefit from ultrasound technology. Image: AdobeStock

Ultrasonic welding of uncoated paper

Ultrasonic welding of uncoated paper is an innovative joining procedure that is friendly to the environment, and with which packaging companies can save large amounts of energy and resources. Syntegon, who own the patent, have recently transferred exclusive rights to the process to Herrmann Ultraschall. The company wants to make the process fit for market and to become established in the packaging industry.

In order to reliably join uncoated paper, there was until now always a need for additional resources like adhesives or clips. Joining paper using ultrasound alone will be significantly more sustainable in the future. What has been successfully proven under laboratory conditions is now to be established at an industrial scale for the first time. For this purpose, Herrmann Ultraschall and their customers will test and continue to improve applications in the company’s ultrasound laboratories.

„Until now we have always needed a small amount of adhesive in the material in order to join paper using ultrasound – and we now can completely dispense with it. This opens up wholly new options for the environmentally friendly design of packaging. On the way to a functioning circular economy, this is a large milestone. We are happy that together with Syntegon we were able to create the supporting conditions which make this innovation ready for series-production.“

Thomas Herrmann, CEO at Herrmann Ultraschall

The managing directors of Herrmann Ultraschall, CSO André Deponte (left) and CEO Thomas Herrmann (2nd fr. l.) receiving exclusive rights to the process from Syntegon, represented by then CEO Dr. Michael Grosse (2nd fr. r.) and Stefan Brandstetter, patent agent (right). Image: Syntegon

Highly stable and visually perfect

Ultrasonic welding of paper works similar to welding plastics, but there is one critical difference: The material needs to be damp before welding. The welding tool, the sonotrode, transfers the ultrasonic vibrations to the paper, which separates the fibres in each layer of paper at the point of contact and creates new fibre connections. The friction heat generated between the materials vaporises the applied humidity during the process without damaging the paper. This creates a highly stable and visually perfect joining in a very short time.

„With the Herrmann Ultraschall group we have found a competent partner who will introduce this promising technology into all packaging applications using fibre based materials. The competence of our partner in ultrasound creates the conditions for a broad acceptance of the process in the market.“

Dr. Johannes Rauschnabel, head of pre-development at Syntegon

The application areas for ultrasound welding of paper cover a large scope: from primary packaging like fruit bowls made of thin cardboard to secondary packaging in the form of paper bags. The great advantage for companies, other than saving on joining compound, lies in the low energy requirement, the rapid processing times and the extremely small amount of wear suffered by the welding tools. Uncoated paper is also significantly easier to recycle, which further improves the sustainability balance of packaging.