Dyeing of wool woven fabrics by using layer-by-layer method - part I: Results related to the process optimisation

Wool fibres are commonly dyed at boiling temperature by the exhaust method. However, conventional dyeing conditions damage various properties (handle, strength-elasticity, lustre, etc.) of these sensitive fibres. For this reason, there is a need to develop a dyeing method that will enable the fibres to be dyed under milder conditions without causing any negative effects on dyeing efficiency and fastness. A dyeing technique on which studies have been concentrated in recent years is the layer-by-layer (LbL) method. In the literature there is no studies on the dyeing of wool fibre by the LbL method. In this first part of a study, the results of the process development for dyeing woollen woven fabrics with the LbL technique are presented. The cationisation and/or ozonation treatment of the fabrics before LbL dyeing caused negligible decrease in fabric strength. However, these treatments significantly increased the colour yield obtained in dyeing and thus the number of layers required to obtain a certain colour yield was reduced. The optimum colour yield was obtained in 14 layers with levelling type acid dye and the washing and rubbing fastness values of this fabric sample were quite good. In LbL dyeing both polydiallyldimethylammonium chloride and polyethylenepolyamine compound (conventional cationising agent) were used as cationising agents and close colour yields were obtained with both. This is very important for the industrial applicability of the process since polydiallyldimethylammonium chloride is only available as a pure product and therefore it is quite expensive. In contrast, commercial cationising agents are cost-effective.