Rope dyeing process using indigo derivative and dyed article thus obtained

Abstract From the Canadian patent

Disclosed is a dyeing process for rope dyeing denim cotton yarns a fashion blue color which comprises the steps of forming the yarns into a rop; repeatedly immersing the rope in a dye bath containing a reduced water soluble form of a halogenated indigo derivative which is air oxidizable squeezing the rope to remove dye bath liquid therefrom exposing the damp rope air to air to air oxidize the reduced form of the indigo derivative in the yarn; and then further oxidizing the incompletely oxidized reduced form of the indigo derivative in the yarn forming the rope in an oxidizing bath containing a chemical oxidant, e.g. sodium perborate.