Improvement of the retention-formation relationship using three-component retention aid systems

Abstract

Abstract 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.