Crosslinking a hydroxyethylsulphonyl dye on cotton to achieve covalent fixation in a long‐liquor process

A heterobifunctional [dichlorotriazine and vinylsulphone (DCT‐VS)] reactive crosslinker, 2,4‐dichloro‐6‐{ρ‐[(2′‐sulphatoethyl)sulphonyl]phenylamino}‐1,3,5‐triazine (DC‐SES) was synthesised and coapplied with nicotinic acid to covalently fix hydrolysed Cl Reactive Black 5 (HBB) (hydroxyethylsulphonyl dye) to cotton in a long‐liquor process. It is suggested that a very active quaternised nicotinic acid ammonium salt of DC‐SES was generated in situ, which reacts readily with HBB and cellulose leading to dye fixation. Further dye fixation can be obtained by the addition of alkali at 60 °C; the final fixation value from this system is very good. Application of this system as an aftertreatment in the conventional Cl Reactive Black 5 dyeing bath, results in 10–15% higher exhaustion and fixation values compared to the usual dyeing procedure.