Control of a batch dyeing process with three acid dyes

The process of dyeing of nylon with tertiary acid dye mixtures is controlle d by automatic metering of dyes and chemicals. Closed-loop control is achie ved by real-time data acquisition of the dyebath conditions coupled with a feedback control strategy. The objective of controlled dyeing is to obtain an on-tone build-up of shade using three monosulfonated acid dyes in mixtur e combinations. Computerized dosing pumps control the pH, the dyebath conce ntrations of the individual dyes, and the total sorption of each dye during the process. photographs of yarn cross sections examined under the polariz ing microscope reveal uniform penetration of dye in the individual fibers o f the yarns. Color matching of samples dyed under identical dyeing conditio ns shows good shade reproducibility. It is also possible to re-use a dyebat h of residual dyes and chemicals from a previous dyeing. Thus, good shade r eproducibility and uniform shade build-up can be achieved in laboratory dye ing machine by adopting real-time closed-loop control.