ANALYSIS AND RETENTION BEHAVIOR OF CATIONIC AND AMPHOTERIC STARCHES ON HANDSHEETS

Chemical structures of substituents in cationic and amphoteric starche s were analyzed by nuclear magnetic resonance (NMR), and retention beh aviour of these starch derivatives at wet-end of papermaking was studi ed in terms of their chemical structures. Degrees of substitution (DS) of cationic or anionic groups and amylose/ amylopectin ratios in star ch derivatives were obtained from their NaOD/D2O solutions by NMR. Con tents of starch derivatives in handsheets were determined: using a glu cose :sensor after enzymatic hydrolysis of starch components in the ha ndsheets. Experiments using a carboxyl-group-blocked pulp revealed tha t cationic and amphoteric starches were retained in the sheet, primari ly forming ionic bonds between cationic groups in the starch derivativ es and carboxyl groups in pulp fibres or fines. On the other hand, par t of the starch derivatives retained in the handsheets were trapped in the pulp mat by nonionic interactions.