FILLER RETENTION INDUCED BY CATIONIC MICROPARTICLES IN THE PRESENCE OF NON-WOOD FIBRES

摘要

Although much research has been done into retention systems, involving anionic microparticles, few systematic investigations employing cationic polymer microparticles (CPM) have been reported. In the present work, emulsifier-free polymerisation was conducted via co-polymerisation of styrene with cationic monomer or cationic monomer/acrylamide to prepare" cationic polymer microparticles with well-defined structures. The particle size and charge density of CPM have been characterised using a Zetasizer 3000 and a Mutek PCD03. Dynamic flocculation experiments, conducted with a photometric dispersion analyser (PDA 2000), showed that the effectiveness of CPM as a retention aid for fine clay particles or precipitated calcium carbonate (PCC) is a function of the particle size and the charge density of CPM. In conjunction with an anionic polyacrylamide based copolymer, the flocculation was significantly improved. It was found that the anionic polymer with low charge density and high molecular weight possessed the best synergy with CPM. This also significantly reduced the dosage of polymer flocculant required for an effective retention. The best flocculation occurred at a low value of the anionic polymer:CPM ratio (1:12), with anionic polymer dosage approximately 0.04 % (wt on fillers) The work has been extended to the retention of PCC with the non-wood fibres consisting of Hemp (Cannabis saliva) and Flax (Linum usitatissimum). In comparison to a commercial microparticle, i.e., anionic silica, CPM achieved the same level of retention but meanwhile maintained bonding strength, which implied the functionality of CPM as a bonding agent in non-wood fibres.