Syntheses Of Cationic Natural Polymers With High Degree Of Substitution And Their Application In Controlling Waste Pulp Stickies

In order to investigate the feasibility of using high substituted cationic starch (HCS) and high substituted cationic guar gum (HCG) in controlling stickies problems in waste pulps, a series of HCS and HCG were synthesized by half-dry process. The effects of factors such as the dosage of etherifying agent, the dosage of alkali, water content of the system, reaction temperature and reaction time were studied. Under the optimum process conditions, cationic starches with degree of substitution (DS) above 0.9 and cationic guar gums with DS above 0.24 were prepared, and their structures characterized by Fourier transform infrared spectroscopy (FTIR).In studying the effects of stickies controlling, single systems using HCS (DS 0.94) and HCG (DS 0.30) were compared with polyamine (PA);then the effects of dual systems with the combination of PA and HCS or HCG, triple systems with the combination of PA, HCS or HCG, and a cationic polyacrylamide(CPAM) retention agent in stickies controlling were also studied, together with their effects on pulp overall retention and handsheets physical properties.The results showed that single systems were not good enough, dual systems were much better and triple systems were excellent in stickies control. In the dual systems, when the dosage of PA was 1000ppm and the dosage of HCS or HCG 500ppm, the stickies removal ratios were 74.30% and 84.51%. In the triple systems, when the dosage of PA was 1000ppm, the dosage of HCS or HCG 500ppm and the dosage of CPAM 500ppm, the removal ratios were 80.28% and 92.60%. It also showed that the overall retentions of pulp were improved, the densities of handsheets increased while paper strengthes changed only slightly.