Some Experiments on the Dyeing of Nylon Yarn

Abstract

SummaryDirect dyes which remain in solution in an acidified dyebath, as most do, can be dyed on nylon yarn at rates comparable with those of the same dyes when dyed on viscose rayon yarn from a neutral bath. In the absence of acid, nylon yarn absorbs direct dyes much more slowly than does viscose rayon. The rate and equilibrium absorption of direct dyes by nylon yarn is dependent upon the pH of the dyebath.Increase of dyeing temperature increases the rate of absorption of both direct dyes and acid dyes and decreases the equilibrium absorption.With direct dyes, neutral salts raise the rate and degree of dyebath exhaustion from a neutral bath and decrease both in an acid bath; the latter behaviour is also shown by acid dyes on wool or nylon.Nylon, like wool, has an acid‐binding capacity which increases with the mol. wt. of the acid for a series of organic sulphonic acids, and is lower than that of wool.Nylon yarn dyed with direct dyes exhibits dichroism when examined in polarised light. Some acid dyes produce dichroism on nylon and some do not.All the above facts are accommodated if a dual behaviour is attributed to nylon, viz. that its union with dye may result from (a) the formation of a salt link as with wool and/or (b) the exertion of residual valency forces as with cellulose.SummaryThe fastness to washing and light of nylon yarn dyed with acid dyes, direct dyes, cellulose acetate rayon dyes and chrome dyes has been compared directly with that of viscose rayon, cellulose acetate rayon and wool. Recommendations as to the potential usefulness of different classes of dyes are made.Direct dyes do not cause appreciable degradation of nylon when the dyeings are exposed. Vat dyes cause extensive degradation, which takes place more rapidly than is the case with cellulosic fibres and is accompanied by similarly rapid fading of dye.Whereas fading of dyes occurs in the presence or absence of oxygen, an atmosphere containing oxygen is essential for photodegradation of the fibre.