Economic analysis of cotton textile finishing processes
Textile mills have available to them treatments which eliminate the problem of neps not receiving dyes. These treatments come in many forms, from pretreatments to aftertreatments, using a variety of different products. Textile manufacturers must choose between the many treatments available based on how well it works, cost effectiveness, how easily it is incorporated into their current processes, and whether the new treatment requires equipment which they do not own at the time.
One treatment which may be used to cover neps uses submercerization strength sodium hydroxide. Sodium hydroxide is used in many wet processes in the textile industry. When using submercerization, the surface fibers of the nep swell in order to allow the dye to penetrate the nep while retaining overall fiber compactness (Cheek, Wilcock, and Hsu, 1987). This process improves nep coverage by up to 86 percent.
Another treatment used for the coverage of neps involves the use of a cationic polymer pretreatment by the pad/dry process (Mehta, Salame, and Combs, 1990). This treatment is effective in covering neps after dyeing with direct, reactive and acid dyes. However, because these treatments are based on the pad/dry method, the fabric must be dried after scouring and/or bleaching prior to the chemical application. An altemative to the pad/dry treatment is the exhaust process. This altemative process eliminates drying and could be easily incorporated into the fabric preparation sequence currently being used by most textile mills (Mehta and Combs, 1990). One treatment which uses the exhaust method involves the use of a derivative of chitin.