Dyeing process control principles

The general concept of the synthesis of sandwich materials is illustrated in Figure 1.15. In our first report on this [22], we first inserted a neutral dyel from the gas phase, filling the channels to the desired degree. It was possible to find conditions to insert a cationic dye2 from an aqueous suspension, despite the fact that neutral dyes are usually displaced by water molecules. This process can be well controlled so that a specific desired space is left for the third dye3 to be inserted. It is also possible to insert first a cationic dye and then a neutral one or to use other combinations. The principle can be extended to more than three different dyes. 

Despite the evident success of PDT in the medical field, the application of the principles of PDT to control pathogens in the enviromnent and during food processing and handling was practically scarce. Only recently, several articles have been published on the use of PS dyes in combination with light for the removal of pathogens from contact surfaces... 

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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