Aftertreatment of Anionic Dyes on Nylon Fibres

Meeting of the Bradford Junior Section, held in Bradford Technical College, on 13 October 1969, Mr R. S. Stringer in the chair The wet fastness of dyed unbacktanned nylon fibres decreases slightly during dry‐heat setting under moderately severe conditions. This is attributed mainly to oxidative degradation of the fibre, which also results in considerable yellowing and loss in strength. The wet fastness and tensile strength decrease slowly during prolonged steam setting, but several hours are required to produce a similar decrease to that produced by treatment for a few minutes in hot air. Yellowing of the fibre during steam setting is very slight, even on prolonged treatment. The rapid decrease in the wet fastness of backtanned nylon during setting occurs mainly in the early stages of treatment and the fastness decreases ultimately to that of the untanned and postset fibre. The improvement in wet fastness on backtanning is less on dyed nylon 6 than on nylon 6.6, because less of the agent is taken up by nylon 6. However, the wet fastness of aftertreated nylon 6 decreases more rapidly during setting because this fibre is more prone to thermal degradation. The most important causes of the loss in wet fastness of backtanned dyeings on nylon fibres are ( a ) thermal oxidation of the backtanning agent, ( b ) thermal and hydrolytic attack of the nylon and ( c ) catalysis of degradation of the nylon by the backtanning agent or its decomposition products.