LABORATORY-TO-BULK REPRODUCIBILITY IN EXHAUST DYEING PROCESSES

Dyeing costs depend to a large extent on the degree of laboratory-to-b ulk reproducibility. Costs of lab, mid-scale and bulk dyeings are comp ared. Since lab dyeings are relatively inexpensive compared with corre ctions in bulk dyeing, the use of lab dyeings is stressed and a system atic approach to a blind dyeing technique is proposed. Dye selection i s very important. Criteria for different dye classes are formulated wh ich include dye-dye interactions and the influence of leveling agents. Reactive dyes for cellulosic fibers are particularly sensitive to var iations in the dyeing conditions between lab and production units. If variations in the liquor-to-goods ratios cannot be avoided, a computer program with dye specific correction factors can be used to adjust th e dye formulas appropriately. The program is also useful for calculati ng corrections for different types of alkali. It is quite difficult to take into account the differences between lab and bulk dyeing with re gard to liquor flow and movement of the goods. Therefore dyeings in sa mple jets or package dyeing units can be helpful as an intermediate st ep between laboratory and production.