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

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.

Deflocculation of Cellulosic Suspensions with Anionic High Molecular Weight Polyelectrolytes

“…They also act as drag reducing additives in turbulent flow as they dampen the turbulence in flowing fiber suspensions. The drag reduction has been seen to correlate very well with improved formation (Svedberg 2012). Another possible explanation for the working mechanism of dispersants is that they prevent close contact between fibers due to their large physical size (Wasser 1978).…”

“…However, with the increasing molecular weight, these types of deflocculants usually have a detrimental effect on dewatering (Lee and Lindström 1989). In contrast, the charge density of deflocculants has only a small effect on deflocculation (Svedberg 2012). The physical structure of the deflocculant is also important (Svedberg 2012).…”

“…In contrast, the charge density of deflocculants has only a small effect on deflocculation (Svedberg 2012). The physical structure of the deflocculant is also important (Svedberg 2012). The most efficient structure is linear, but partially branched polymers can be used as deflocculants if high enough dosages are used.…”

“…The properties of non-adsorbing dispersants have been noticed to have a significant effect on deflocculation efficiency (Wasser 1978;Palonen and Jokinen 1986;Lee and Lindström 1989;Svedberg 2012). Usually the higher the molecular weight; the higher the deflocculation effect (Wasser 1978;Svedberg 2012).…”

“…Usually the higher the molecular weight; the higher the deflocculation effect (Wasser 1978;Svedberg 2012). However, with the increasing molecular weight, these types of deflocculants usually have a detrimental effect on dewatering (Lee and Lindström 1989).…”