Dye demand/supply ratio as a predictor for the unlevelness of disperse‐dyed polyester

The ratio of the demand for dye by the fibre and the supply of dye by the dyebath is a useful indicator to predict unlevelness in the exhaust dyeing of polyester with disperse dyes, provided that dispersion breakage is small. The ratio can be calculated from the dye exhaustion curve, the dye solubility and the flow rate in the machine. The findings suggest that unlevelness can be successfully controlled by ensuring that dye demand never exceeds dye supply at any moment during the dyeing process.