EFFECTS OF CARBOXYL GROUPS IN PULP ON RETENTION OF ALKYLKETENE DIMER

The mechanisms of retention of alkylketene dimer (AKD) in laboratory e xperiments were studied in terms of the roles of carboxyl groups in pu lp. Nonionic and cationic pulps were prepared from beaten pulp by amid ations of carboxyl groups in pulp, and AKD-sized handsheets prepared f rom these pulps under Various conditions were subjected to sizing test s and determination of AKD contents. The handsheets prepared from the nonionic pulp had nearly no sizing degrees and tow AKD contents at the usual addition levels of AKD. Handsheets made from cationic pulp had sizing degrees and AKD contents similar to those obtained with the non ionic pulp. All the results obtained in this study showed that carboxy l groups in pulp act as retention sites for cationic wet-end additives such as AKD emulsion, cationic polymers and alum, forming ionic linka ges. When carboxyl contents were increased, sizing degrees and AKD con tents of the handsheets increased to some extent under certain conditi ons.