抄録
Using 25 kinds of cationic polyacrylamides (C-PAMs) prepared by Hofmann reaction with PAMs having 5 different degrees of polymerization (DP: 610-49000) in such a way that 5 levels of charge density (1.4-8.6 meq/g) are produced for each DP, effects on drainage and retention of unbleached softwood kraft pulp (CSF: 375 ml), bleached hardwood kraft pulp (CSF: 425 ml) and thermomechanical pulp (CSF: 168 ml) have been studied. Results obtained are as follows:
(1) When an addition level of C-PAM was low, as indicated by 0.05% on pulp, the higher both DP and charge density, the greater were Canadian standard freenesses (CSF) of all pulps. As CSF became greater, lower CSF tester white water consistency, that is, higher retention was achieved.
(2) The characteristics of C-PAM showing the highest CSF and retention were gradually shifted to lower DP and/or lower charge density, as the addition level of C-PAM on pulp increased.
(3) These phenomena were explained on the basis of the balance between the bridging effect and the electrostatic repulsion of C-PAM. With an increase in DP of C-PAM, the bridging effect became greater, though the electrostatic repulsion developed at a lower addition level of C-PAM.
