By: H.D.Joshi, D.H. Joshi, M.G. Patel and S.R. Naik



'Application of Cationic Dyes toAnionically Modified Nylon and their Performance Evaluation with CationicDyeable Polyester with Special Reference to Fastness Properties'


Introduction


The production of multi-colour effects has been done by thehelp of differential-dyeingsystems. The term "differential-dyeing" is applied to fibres whichare of the same basic type, e.g., nylon but with different dyeing properties.To vary the dyeing properties of the fibre (nylon), chemical modifications areemployed.


In one case the substantivity of the fibre for anionic dyes is modified byaltering the amine end-group content.


This can be done by using a stabilizer during polymerisationwhich has one or two carboxyl groups that can react with the amino end groupsof nylon polymer. The stabilizer also has one or two sulphonate groups whichmake the polymer anionic.


An example of such a stabilizer is disodium 3,5- disulphobenzoic acid- C6H3(S03Na)2 COOH, i.e., Na2DSBA. The reaction of the nylon polymer with Na2DSBA isas follows:-


HOOC-Nylon Polymer-NH2 + HOOC C6H3(S03Na)2 ------->


HOOC-Nylon Polymer-NHCQ-C6H3 {S03Na)2 + H20

(Cationic dye dyeable nylon)


Other alkali metal salts, e.g., lithium salt can also beused. 5-sodium sulphoisophthalicacid is also used to introduce sulphonate groups in nylon 6 polymer. TheintrOduction of the sulphonate group increases the affinity for basic dyes while the affinity for aciddyes is very low.


In another modification, the amine endgroup content is varied which givesa differential dye pick-up of acid dyes on nylon making it regular,light-dyeable and deep-dyeable. The amine end group content has a predominanteffect on dye pick-up when dyed with acid dyes. The amino end groups are thefunctional sites in nylon for the adsorption of anionic dyes in acidicsolution; the polymer and acid dyes are ionically bonded in the acidic dyebath.



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Aboutthe Authors:


The authorsare associated with Man-Made Textiles Research Association (MANTRA), Surat.