The effect of refining intensity and surfactant addition on dewatering, and wet and dry web properties

In this study, the effects of refining intensity, alteration of fibre properties and fines content, on wet and dry web properties were determined. Refining, both at low and high intensity, as well as high content of fines improved the mechanical properties of the wet web but decreased the dry content after wet pressing. High intensity refining with much fibre cutting resulted in lower dry content after wet pressing and higher density of dry sheets than low intensity refining with much external/internal fibrillation of the fibres. The fibre properties contributed more to the residual tension, while the fines content was more important for the wet web tensile strength. Additions of a non-ionic surfactant to the original pulp lead to shorter dewatering times and higher solids content after wet pressing. Addition of the surfactant to refined pulp shortened the dewatering time without deteriorating the mechanical properties. By tailoring the refining conditions and adding surfactants, the mechanical properties of the wet web could be improved without prolonging the dewatering time.