Continuous dyeing of cotton with reactive dyes using infrared heat

Fabrics containing cotton fibers were dyed in a continuous process by impregnating the fabric with an alkaline solution of reactive dyes and then drying and heating it using electrically generated infrared radiation followed by hot air. Optimal fixation of the dyes required a strongly alkaline dye solution and heating the fabric to as high a temperature as possible consistent with avoiding thermal damage to the fibers. Color consistency and quality were well-controlled along the fabric length during both pilot- and industrial-scale continuous dyeing and the color differences, relative to commercial products obtained by batch dyeing procedures with the same recipes, were small. The infrared process offers reduced pollution loads in the washing liquors from reactive dyeing because fixation yields were greater than those for the cold pad-batch dyeing procedure, and no electrolytes or urea were needed in the initial dye solutions.