Potential of cold-soluble cationic swell flours by means of reactive extrusion
Cationic starches and flours are already used with success as wet strength increasing additives in the wet end of the paper machine. The positive charge of the starch molecules interacts with the negative charge centres of the cellulose fibres while forming further bond points and thus improves the paper properties significantly, e.g. by higher strengths. The current state of the art is to dissolve the cationic starches or flours in a jet cooker prior to their wet-end use in paper mills.
For this purpose, the papermaker needs both the equipment and the related knowledge, as well as steam energy. A ZIM cooperation project with the SME cersan Erfurt GmbH was designed to look for a new development approach for cationic flours to allow for a simple treatment process without energy- intensive equipment while ensuring the same or better strength values in the paper. The aim was to use and adapt the established technologies of extrusion and dry modification for this purpose, or, alternatively, look into the possibility of combining both technologies by way of reactive extrusion. The project resulted in the development of cold water-soluble cationic flours that showed almost identical strength increases in paper as compared with standard flours.
Fig. 1: Process for the manufacture of wet-end products
However, total energy consumption for generating the cold-solubility in the pilot extruder of the Technical Centre exceeded that of jet cooking. Basic research on reactive extrusion on the contrary suggests an energy-efficient and thus lower-cost production of a cold-soluble cationic flour after optimisation of the technology. So reactive extrusion of cereal flours provides a promising potential. We will stay together on this.The ZIM research project ZF4156905WZ8 was sponsored by funds of the Federal Ministry for Economic Affairs and Energy, BMWi.
Ceresan Erfurt GmbH is a medium-sized enterprise in Markranstädt, which uses a proprietary method for dry chemical modification of conventional cereal flours to make specific technical flour products for the paper and gypsum plasterboard industry. In contrast with conventional starch modification in suspension, the dry chemical method is characterized by high yield and low reaction temperatures. The secondary and by-products remain in the end product. This method produces no effluents and does without a drying step.
Dr. Alexander Feldner,
Dr. Franziska Mai,