Chemical Distribution
Progression of basic reagent addition during reactive dyeing regulates the dye-fibre reaction rate to prevent uneven coloration on cellulosic fabrics. An alkali dosing profile dictates the rate and volume of sodium carbonate or sodium hydroxide introduced into the dye bath across a specific time interval. Dyehouses apply these parameters to transition the dye bath from a neutral migration phase to an alkaline fixation phase where covalent bonding occurs.
This gradual transition governs the uniformity of the final shade on cotton substrates.
Fixation Rate
Control of pH during reactive dyeing relies on the progressive ionization of cellulose hydroxyl groups. When the alkali dosing profile uses a linear progression, the rapid shift in bath acidity can cause premature dye aggregation. Implementing a progressive or quadratic dosing profile instead delays the pH spike, which maintains a uniform migration rate across the yarn package or fabric rope.
Graduated Feed
Automation systems in modern jet dyeing machines execute pre-programmed metering profiles through closed-loop feedback valves. These mechanical systems measure the pH at regular intervals to adjust the pump speed and maintain the desired chemical ramp. Continuous monitoring prevents chemical spikes that lead to patchy distribution across the batch.
Hydrolysis Avoidance
Over-dosing at early stages promotes the competing reaction of the reactive dye with water molecules rather than cellulose. This chemical loss reduces the final color yield and increases the washing-off burden after dyeing. Precise execution of the profile limits the formation of hydrolysed dye and ensures maximum dye utilisation.
