Thermal and Photochemical Crosslinking of Paper Fibers for Generation of Paper Substrates Providing a High Wet Strength and Multiple Chemical Fucntions

• Applicants: Professor Dr. Markus Biesalski; Professor Dr. Jürgen Rühe
• Subject Area: Synthesis and Properties of Functional Materials
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405422473

If paper comes into contact with water, the mechanical strength decreases considerably and under certain circumstances only reaches a few percent of the initial strength. For this reason, when producing papers that are intended for use in which they can get wet, significant amounts of a so-called wet strength agents - mostly cationic polymers - are added. These wet strength agents are attached to paper fibers, are partially chemically cross-linked and strengthen the paper fibers and their cohesion, although the details of this reinforcement mechanism have not been clarified down to the last detail. The commonly used wet strength agents are, however, not without problems in terms of their environmental behavior. In the current funding phase, it has been possible to use C,H insertion crosslinking processes (CHic process) to generate papers that have a wet strength that is 50 times better than that of unmodified paper. For this purpose, photochemical and thermally induced crosslinking processes have been developed or further developed. Furthermore, the first results to elucidate the reinforcement mechanism of the paper fibers could be obtained. The aim of the continuation of the research project is to further continue our investigations into wet-strength development of functionalized papers. The focus will be on studies that will further improve our understanding of the reinforcement mechanism in wet papers. For this purpose, the distribution of the polymers in the paper is to be analyzed in more detail and individual fiber experiments are to be continued. To investigate the polymer immobilization (CHic method), the topology of the cellulose fibers is to be stained with the help of specific binding enzymes that contain the carbohydrate binding motif. Furthermore, changes are to be made in the chemical structure of the wet strength agent, which allow rapid bonding and reinforcement of the paper even at temperatures below 100 ° C, so that the papers do not have to be completely dry for the wet-strength finish, which would result in considerable energy savings. In addition, the concept is to be expanded so that even paper fibers and incomplete papers can be modified and the concentration of polymers used can be significantly reduced. In addition, the concept is to be expanded so that paper fibers can already be modified before paper production and the use concentration of the polymers can be significantly reduced. Furthermore, first concepts for the design of multifunctional wet strength agents will be investigated, in which the improvement of wet strength is combined with further functionalities.

• DFG Programme: Research Grants