High-temperature aqueous dyeing:- (Part 1)
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High-temperature aqueous dyeing :
The bath is set at 500C with a suitable surface-active agent. The well-dispersed dye is added to the bath and the temperature is raised to 85-900C. After working the material for 15 min. the pH of the bath is adjusted to 6 with acetic acid. The machine is then sealed and the temperature is raised to 1000C at the rate of 10C per min. Dyeing is carried out under pressure for 1.5 hr. The machine is cooled carefully to 95-1000C before opening, then the material is scoured and rinsed well.
When dyeing yarn in the package machine, preshrinking may be necessary. The yarn is wound on collapsible paper tubes and treated for 1 hour at 1100C. The yarn is then rewound onto dye tubes for dyeing. Preshrinking may be avoided by winding the yarn onto dye tube containing a sponge-core or a base of cotton yarn 6mm thick.
