Principles Exhaustion dyeing

Peri-heterocycles serve as dyes, luminophores, energochromophores, organic conductors, and bioactive compounds. Since the aim of this review is the illustration of major construction principles of the peri-heterocyclic nucleus, the authors do not claim an exhaustive review of all syntheses. 

A different principle is used in the exhaust process, where the fabric or garments are first introduced into a closed vessel, such as a dyeing apparatus, with an initial quantity of water. The microcapsule dispersion, the binder, the auxiliaries, and possibly acids/bases for pH adjustment are then metered into the vessel at defined times, speeds, temperatures, and pH in such a way that the microcapsules and the binder ultimately end up distributed as evenly and completely as possible on the textiles. The process is generally a combination of exhaustion and controlled precipitation, which is a sophisticated version of the way softeners work in the domestic washing machine. 

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