Ampholytic Starch Wet‐End Additives

A series of starch polyampholytes, containing oppositely charged groups, was synthesized, characterized, and evaluated as wet‐end additives for strengthening unbleached kraft paper. In preparation of the polyampholytes, native corn starch was substituted first with quaternary ammonium groups and then with either phosphate, phosphonate, sulfate, sulfonate or carboxylate groups, by conventional etherification and esterification procedures. In no instance was the wet and dry strength of the paper appreciably greater than that of paper treated with the parent cationic starch. Although present work does not discount the possibility that polyionic crosslinked starch additives can develop wet strength, the work suggests that XSA polyampholytes undergo side reactions, which are believed to result in starch‐to‐starch and/or starch‐to‐cellulose covalent bonding.