Alkali Dosing Profiles and Mass Transfer in Jet Dyeing
Controlled progressive alkali dosing matches jet fabric loop velocity to eliminate surface fixation spikes and secure level shade fixation on cellulosic cloth.
Dye Hydrolysis Rate
Reactive Inactivation
Chemical reaction speeds describing the decomposition of reactive dyes in the presence of water determine the efficiency of the fixation process on cellulosic fibres. A dye hydrolysis rate indicates that the dye molecules react with the liquor rather than the hydroxyl groups of the cotton, rendering them unable to form a covalent bond with the fabric. This process results in wasted colorant and increased rinsing requirements to remove the unattached chemicals.
Temperature Impact
Thermal conditions in the dye bath directly influence how quickly the inactivation occurs. As the temperature rises to accelerate the main dyeing reaction, the dye hydrolysis rate also increases, necessitating precise control of the pH levels. Modern dyestuffs are engineered to balance these competing reactions, ensuring that the maximum amount of pigment binds to the substrate before the chemical potential is lost.
Fixation Efficiency
Measuring the ratio of fixed dye to hydrolysed dye provides a metric for process sustainability. When the dye hydrolysis rate is excessive, the effluent contains a higher concentration of suspended solids and requires more intensive wastewater treatment. Reducing this rate involves optimising salt concentrations and alkali dosing sequences during the exhaust dyeing cycle.
Liquor Stability
Maintaining a stable liquor environment is necessary to prevent inconsistent shading across bulk production lots.