Cotton Yarns in Continuous Wet Processing Engineering
Continuous wet processing of cotton yarns demands precise control of yarn structure, swelling draft, liquor application, and transport tension to assure performance.
Pad Steam Fixation
Colour Attachment
Continuous dyeing systems employ saturated steam to drive dye molecules from the surface into the interior of the fibre. After the fabric is saturated with a dye liquor, pad steam fixation provides the thermal energy needed to open the fibre structure and accelerate the chemical reaction. This method is particularly effective for reactive and vat dyes on cotton fabrics.
Thermal Activation
Saturated steam at atmospheric pressure creates a moist environment that prevents the fabric from drying out during the fixation phase. Because pad steam fixation occurs in a closed chamber, the temperature remains constant and provides uniform conditions for every centimetre of the fabric. This consistency is essential for achieving level shades in large production runs.
Chemical Penetration
Urea and other auxiliaries in the pad liquor assist in the dissolution of the dye as the steam condenses on the fabric surface. During pad steam fixation, the moisture film on the fibre surface acts as a medium for the dye to migrate into the amorphous regions of the cellulose lattice where it forms permanent bonds. The process typically takes between thirty and ninety seconds depending on the dye class and the depth of the shade required for the specific order.
Precise control of the steaming time ensures that the dye is fully fixed without wasting energy.
Automated Processing
High speed ranges allow for the treatment of thousands of metres of fabric in a single shift without the need for batching. Following pad steam fixation, the fabric passes directly into a wash range to remove unfixed dye and chemicals. This transition between stages reduces the total time required for fabric finishing.