Chemical Agent
A synthetic polymeric additive increases the viscosity of the pad bath to prevent the movement of dye particles during fabric drying. Formulators add a polyacrylate antimigrant to the dye liquor to lock pigment particles in place before the thermal fixation phase. This agent remains active in the liquid phase and does not alter the chemical structure of the dye.
System Mechanism
The long-chain molecules of the polymer form a temporary three-dimensional network in the water. This network increases the resistance to flow, which prevents capillary forces from moving the suspended dye particles toward the evaporating surface. As the temperature rises in the pre-dryer, the polyacrylate antimigrant maintains its structure, keeping the dye distribution uniform.
Once the fabric is dried and the dye is thermally fixed, the polymer can be washed out easily during the final rinsing stage.
Operational Control
Measuring the viscosity of the pad bath at regular intervals ensures that the polymer concentration remains stable. When preparing the bath, adding the polyacrylate antimigrant slowly with continuous stirring prevents the formation of lumps. Operators monitor the shear rate in the padder, as high shear can temporarily lower the effective viscosity of the liquor.
Combining this additive with compatible wetting agents prevents precipitation in the pad trough.
Process Constraint
High concentrations of this chemical can make the fabric feel stiff if it is not completely washed out during the post-fixation rinse. This additive can also reduce the penetration of dye into highly twisted yarns.
