AbstractThe hypothesis is that it should be possible to modify papermaking conditions in line with the softening properties of high yield pulp fibres and achieve similar strength properties to conventional chemical pulp based paper. We therefore investigated the rheological and physical properties of high yield pulp based papers during hot-pressing. Our results confirm that increased temperature combined with sufficient pressure enables permanent densification by softening of lignin, producing very high tensile strength. This treatment also significantly improved the wet tensile strength in comparison to bleached kraft pulp without using wet strength agents. The high yield pulps used here were spruce based thermomechanical pulp, chemi-thermomechanical pulp, and high temperature chemi-thermomechanical pulp, and birch-aspen based neutral sulphite semi chemical pulp, with spruce-pine based bleached kraft pulp as reference. Rapid Köhten sheets of 150\hspace{0.1667em}\text{g}/{\text{m}^{2}} and 50 % dryness were hot-pressed in a cylinder-press at 20–200 °C, 7 MPa, and 1 m/min. The mechanical properties showed great improvements in these high yield pulp papers, with tensile index increased to 75 kNm/kg and compression strength index to 45 kNm/kg; levels close to and better than bleached kraft. Wet strength increased to 16 Nm/g compared to 5 Nm/g for bleached kraft.

Functionally active membranes made of cellulosic microfibers (CMF) have emerged as promising sorbents for the removal of nano-sized pollutants from water. The adsorption efficiency of these membranes has been increased...

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The effects of retention on formation and drainage by using three-component retention aid systems were examined using a pilot web former. The purpose was to examine whether the relationship between retention and formation could be improved by using systems based on cationic polyacrylamide, structurally different high molecular weight anionic polymers and montmorillonite clay. The structure of the anionic polymer was varied from linear to fully crosslinked and added from a small amount up to such a level where papermaking fibres in suspension become dispersed. The pilot web former experiments were performed using an R-F (Retention and Formation)-machine employing a fine paper stock (90 % hardwood and 10 % softwood kraft pulp) with an addition of 25 % precipitated calcium carbonate (PCC) (based on total solids content). It was found that the paper formation could be significantly improved, at a given level of retention by using a micro-particulate retention aid system (cationic polyacrylamide and montmorillonite clay) in combination with an anionic polyacrylamide. Most important, it was found, that with such three-component systems, the impairment of the drainage could be avoided and, hence, that the improved formation was not provided by worsened drainage on the wire section.