WHAT DO WE EXPECT FROM GCC PREFLOCCULATION? HOW CAN WE ACHIEVE THAT?

摘要

Filler preflocculation technology is to flocculate filler particles prior to their addition to pulp stock.This provides the most viable and practical solution to increase filler content while minimizing strength loss.The characteristics of filler flocs,such as the floc size and structure,have a strong influence on the pre-flocculation efficiency,which depends on the properties of the flocculants used.The influence of several polymeric retention systems on the flocculation of GCC fillers was examined using a real time floc size determination unit.Also the effect of shearing conditions on flocculation,deflocculation and reflocculation was investigated.It was shown that polymer type,addition rate and shearing conditions had a significant influence on flocculation phenomena of GCC.It was shown that employment of a dual polymeric retention system consisted of cationic PAM and anionic PAM,and a microparticle retention system,composed of cationic PAM and bentonite gave repetitive reflocculating effect after deflocculation.Their effects,however,differed depending upon the cationic polymer used.The influence of flocculant systems on the structural characteristics of filler flocs were examined by a mass fractal analysis method.C-PAM/micropolymer system gave the greatest improvement in tensile index,and the mass fractal analysis showed that this can be attributed to the formation of highly dense and spherical flocs by this flocculant.Results suggest that a better understanding of the characteristics of pre-flocculated fillers and their influence on the properties of paper can be gained based on a fractal analysis.Depending on the temperature and pH of the cationic PAM solutions the preflocculation of GCC particles was influenced and this was attributed to the hydrolysis and formation of carboxylated anions.