Standard Salt Dosing Schedules for Reactive Dyeing Heavy Cotton Canvas
Progressive exponential salt dosing prevents surface strike spikes and forces reactive dye penetration into heavy cotton duck yarn cores.
bis-MCT Dyes
Molecular Architecture
Reactive colourants containing two monochlorotriazine functional groups provide multiple covalent bonding sites on cellulosic polymer chains. These bis-MCT dyes exhibit moderate substantivity and high exhaustion efficiency during exhaust dyeing cycles. Each reactive anchor undergoes nucleophilic substitution with cellulosic hydroxyl groups under hot alkaline conditions around eighty degrees Celsius.
The twin reactive groups ensure high fixation yields exceeding eighty percent, reducing residual colourant volume in dyehouse effluent.
Processing Behaviour
High thermal energy drives diffusion through tightly packed yarn packages or dense woven goods. Dyeing cycles require prolonged migration periods prior to alkali addition because the twin reactive anchors restrict mobility once covalent bonding begins. Dyebaths demand sodium chloride or sodium sulfate concentrations between fifty and eighty grams per litre to overcome negative surface charges on cotton.
Performance Benchmark
Commercial wash fastness under standard ISO 105-C08 testing demonstrates superior colour retention compared to monofunctional analogues. Wet rubbing fastness routinely achieves grade four or better on commercial single jersey fabrics when soaping procedures remove surface-held hydrolysate.
Application Boundary
Processing parameters restrict bis-MCT dyes to high temperature exhaust operations, making them unsuitable for cold pad batch processes that require ambient reactivity. Printers avoid these dyes due to stiff paste requirements and slow fixation kinetics during short steaming intervals.