The performances of carboxymethyl chitosan in wash-off reactive dyeings

Carboxymethyl chitosan (NOCC) with different molecular weight (Mw) and degree of substitution (DS) was synthesized under heterogeneous conditions. The synthesized NOCC was employed as builders in removing unfixed dyes from reactive cotton dyeings. The factors influencing wash-off effectiveness, including the achievable Mw and DS of NOCC and the initial pH value of washing liquor, were investigated. NOCC with the Mw of 25.0 kDa and the DS of approximately 1.0 has achieved the best wash-off effectiveness at the same wash-off conditions. The wash-off effectiveness of NOCC increases with the increase of pH values of washing liquor. The wash-off mechanism was also discussed by spectroscopic study. This study concludes that NOCC is a potential candidate for removing the unfixed reactive dyes on cotton fabrics. (C) 2008 Published by Elsevier Ltd.