Control of a Batch Dyeing Process with Three Acid Dyes

Abstract

The process of dyeing of nylon with tertiary acid dye mixtures is controlled by automatic metering of dyes and chemicals. Closed-loop control is achieved 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 mixture combinations. Computerized dosing pumps control the pH, the dyebath concentrations of the individual dyes, and the total sorption of each dye during the process. Photographs of yarn cross sections examined under the polarizing microscope reveal uniform penetration of dye in the individual fibers of the yarns. Color matching of samples dyed under identical dyeing conditions shows good shade reproducibility. It is also possible to re-use a dyebath of residual dyes and chemicals from a previous dyeing. Thus, good shade reproducibility and uniform shade build-up can be achieved in a laboratory dyeing machine by adopting real-time closed-loop control.