The Effect of Chlorine on Dyed Nylon

After dry chlorination of wool, the chlorine retained by the fibres is present as hydrochloric acid (i.e. is extractable by alkaline solutions); whilst with nylon it is shown that the chlorine is more strongly combined, so that it is not completely extracted by sodium carbonate solution but can be removed by sodium bisulphite solution. Generally, absorption of chlorine by nylon is attended by an increase in fluidity of the nylon in m-cresol and a corresponding decrease in tensile strength; the degree of absorption of chlorine appears to vary with the type of dye used. The presence of wool has a “buffering” action on the uptake of chlorine by nylon and hence tends to protect the nylon from excessive damage. Of the groups of dyes examined (chrome, level-dyeing and neutral-dyeing acid dyes, together with a few soluble acetate-rayon dyes and direct cotton dyes), the chrome dyes were satisfactory in their fastness to chlorination. The lighter shades of neutral-dyeing acid dyes were useless and the other dyeings occupied intermediate positions. All these dyes, with a few exceptions, have a slightly higher fastness to wet chlorination. The above observations are illustrated in detail by tabulated and graphed data, together with colorimetric data for a representative selection of the dyes before and after dry chlorination.