Aftertreatment of disulfonated 1:2 pre-metallised acid dyeings on nylon 6,6 using a syntan in conjunction with a complexing agent

Nylon 6,6 was dyed using three commercial disulphonated 1:2 pre-metallised acid dyes. An aftertreatment with a commercial synthetic tanning agent was applied to the dyeings and the aftertreated dyeings were further treated with a metal salt in an attempt to improve wash fastness properties still further. Untreated, syntanned and syntanned/backtanned specimens were subjected five times to a repeated wash testing protocol. The fastness, to repeated wash testing, of nylon 6,6 which had been dyed with the three dyes was improved, as expected by an aftertreatment with the commercial syntan. Further, significant, improvement in wash fastness was secured by the subsequent treatment of the syntanned fibre with the metal salt. This two-stage, syntan/metal salt aftertreatment raised the level of wash fastness of the 2% omf dyeings to that more closely approaching that expected of the full backtan.