Protection of lyocell fibres against fibrillation; mechanism for the poor crosslinking performance of reactive dyes on lyocell fibres and the influence of a colourless crosslinking agent as co‐applicant

Sandospace R and five multi‐functional reactive dyes have been applied to lyocell fibre, by exhaust methods. A comparison has been made of the number of mmoles of each species covalently bonded to the fibre, with cross‐linking efficiency (NSF values). None of the dyes studied was able to achieve levels of cross‐linking found in non‐fibrillating grades of lyocell, unless unrealistically high levels were applied. Sandospace R readily matched the NSF values found in commercially produced non‐fibrillating fibres. An explanatory mechanism based on differences in size between Sandospace R and the reactive dyes has been proposed. Fitting the experimental NSF data to an Arrhenius model confirmed the increasing gradient of the NSF curves with increasing millimolar concentration of species fixed. The chroma of the agent‐plus‐dye fibre samples remained relatively constant being either at the same level or above that of those fibre samples treated only with dye. Co‐application of Sandospace R with the reactive dyes has achieved levels of cross‐linking found in commercial non‐fibrillating lyocell fibres.