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Reactive extrusion of fibers for paper making applications

The research project aimed at the use of extrusion technology in the field of fiber processing. The application of the ZSK 16Mc twin-screw extruder was investigated primarily for the preparation of pulp, whereby the processes in the extruder and their effects on the fiber properties were to be clarified. In addition to the purely mechanical fiber decomposition, the use of the extruder for the chemical surface modification of fibers should also be investigated with the aim of achieving thermoplastic fiber properties.

The mechanical and chemical pulp processing in the extruder should take place in the high-consistency range so that a utilization of the extrusion unit would be usable as a possible expansion of the pulp preparation, minimizing the otherwise comparatively high water / solvent demand.

It was necessary to produce modified / functionalized fibers with completely new property profiles, which should ideally have thermoplastic material properties alone or as a compound with thermoplastics. Furthermore, mechanical or barrier properties should be investigated. The fiber substances or resolved compounds were subsequently added to high-value papermaking applications.

It has been possible:

  • to mechanically isolate different fibers in the extruder and modify their morphological and mechanical properties in a targeted manner
  • to carry out chemical modifications on fibers in the extruder which lead to differently functionalized fiber materials depending on the reaction and the process chemicals used
  • to made compounds of modified fibers with thermoplastics, which can be dissolved in water
  • by using superficially modified fibers on a test paper machine, to produce papers which exhibit high strengths and improved barrier properties
  • to impregnate anisotropic machine paper with the dissolved thermoplastic compounds, which results in paper materials showing thermoplastic behavior

The results obtained in the project show that the extrusion process with regard to the mechanical and chemical modification of pulp can act as a promising new technique. The targeted use of these chemically altered fibers in the field of paper making results in improved fiber-based products (e.g., paper strength, air permeability), and offers the potential for the development of novel products (thermoplastic paper products, pulp reinforced composites).

The research project VF 140022 was funded by the German Federal Ministry of Economic Affairs and Energy BMWi in the programme for the "Promotion of Research, Development and Innovation in disadvantaged areas" based on the decision of the German Parliament and carried out under the umbrella of EuroNorm in Berlin. We would like to express our warm gratitude for this support. We would also like to express our thank to the involved German and Scandinavian companies for providing proper samples as well as for supporting project performance.