Starch polyampholytes with amine and xanthate substituents: Characterization and application

Starch polyampholytes (xanthated starch amines) that contained either diethylaminoethyl or 2-hydroxypropyltrimethylammonium ether and xanthate substituents were prepared, characterized, and evaluated as wet- and dry-strength agents in paper handsheets. In aqueous solutions, these xanthated starch amines (XSA), which had degrees of substitutions (D.S.) of 0.023–0.33 amine and 0.005–0.165 xanthate, underwent intra- and interionic bonding at their isoelectric points to form soft flocculent precipitates. Properties of XSA resembled those of “complex coacervates.” Paper that was prepared from an unbleached kraft furnish treated with XSA (amine/xanthate molar ratios, from 1.5 to 4.0) had significantly stronger wet and dry strengths than paper treated with cationic starch amines typically used in commercial papermaking.