Dyeing Properties of a Polyamide–Epichlorohydrin Resin

Abstract

The dyeing behaviour of cured films prepared from a polyamide–epichlorohydrin resin (Hercosett) was examined in orderto obtain a better understanding of the dyeing beha viour of Hercosett–treated wool. The polymer films swell by 500–1000%. The swelling decreases with increasing dye content in the polymer and with increasing temperature. The diffusion of acid dyes into the polymer is extremely fast (D =10‐7 cm2/s), and can be accelerated by the addition of salt. The sorption of the dye is described in terms of a Langmuir isotherm, indicating that an ion–exchange mechanism is operative. The concentration of cationic groups in the polymer is very high (2. 4mo//kg) and does not depend on the curing conditions. The addition of salt reduces the exhaustion of the dyebath. Reactive dyes were found to be bound covalently to the resin. During industrial resin treatment it has been shown that the molecular weight distribution of the Hercosett in the resin bath changes markedly, molecular weight increasing with running time and the spread of values being much narrower. This may explain the variation in the dyeing behaviour of wool fibres that have been treated at different times in the same resin bath.