Sustainable adhesive alternative

Reactive hot-melt adhesives (RHM) based on isocyanate are increasingly being used due to their exceptional properties, from packaging to automotive construction and technical textiles. However, the composition of these urethane-based adhesives also involves risks, e.g. the release of hazardous isocyanate. In the “BioRUHM” project, Fraunhofer IFAM is working with project partners to develop a urethane-free concept.

Available alternative RHMs are far behind in the performance spectrum

The main component of polyurethane-based reactive hotmelt adhesives is a moisture-curing PU prepolymer that hardens by reacting with the ambient moisture. The main raw materials for the production of the prepolymer are polyols and diisocyanates.

This is associated with a major disadvantage of this class of adhesive: the release of hazardous isocyanate (NCO) from residues of monomers used in excess or as a result of the back-splitting of urethane groups at elevated temperatures, as is often the case during processing. The highly reactive NCO group poses a risk of sensitization, among other things. Therefore, there is a labeling requirement for this substance class. Some of the alternative RHMs currently available are far behind the PU-based ones in terms of their performance spectrum and have therefore not been able to establish themselves on the market.

The “BioRUHM” project aims to develop a reactive hot-melt adhesive concept on a urethane-free basis. Prepolymers with reactive end groups are to be developed for this purpose.

The project partners and the role of Fraunhofer IFAM

The “BioRUHM” team is divided according to expertise. Adtracon GmbH coordinates the project and contributes relevant application examples and their specifications, product references and formulation work, and carries out the necessary tests to qualify the concept for specific applications.

As a partner on the raw materials side, Hobum is contributing its expertise in bio-based building blocks and is working with the Fraunhofer IFAM on the synthesis of prepolymers and the development of a database on bio-based polyester polyols.

At Fraunhofer IFAM, the analyses of the polyester polyols are supplemented, combined and evaluated for the design of the targeted prepolymers. Finally, the reactive prepolymers are tested at Fraunhofer IFAM for their biocompatibility and safety.

Project partners

• Adtracon GmbH, Hilden (Coordinator)
• HOBUM Oleochemicals GmbH, Hamburg
• Fraunhofer IFAM, Bremen

Funding

Funded by the Federal Ministry of Food and Agriculture on the basis of a resolution of the German Bundestag; the project sponsor of this project is the FNR

Funding code: 2220NR187

Duration: 01.11.2022 – 31.10.2025