Continuous processes, coloration textile

The most popular coloration method is to apply the dyes continuously, usually by padding, but printing, spray jet, and droplet appHcations are used. In order to obtain patterned effects, chemical or physical resisting agents can be appHed first, and deep and normal dyeing nylon and basic dyeable nylon blends can be used. In the latter case the basic dyeable nylon is dyed with cationic dyes. Carpets can be printed in an analogous method to other textiles and this process is more popular in Europe than the continuous appHcation techniques used in the United States. 

In continuous dyeing there are many variables and the rapidity of the dyeing process requites many adjustments during the period in which several thousand meters of textile are dyed. Instmmental science has continued to advance rapidly so that continuous ranges are available which are entirely computer-controUed except for the makeup of the dye mix. These units feature computer control and closed-cincuit television and continuous color measurement techniques. 

These are defined as anionic dyes with substantivity for cellulosic fibres applied from an aqueous dyebath containing an electrolyte. The forces that operate between a direct dye and cellulose include hydrogen bonding, dipolar forces and non-specific hydrophobic interaction, depending on the chemical structure and polarity of the dye. Apparently multiple attachments are important, since linearity and coplanarity of molecular structure seem to be desirable features (section 3.2.1). The sorption process is reversible and numerous attempts have been made to minimise desorption by suitable aftertreatments (section 10.9.5). The two most significant non-textile outlets for direct dyes are the batchwise dyeing of leather and the continuous coloration of paper. 

The objective of this paper Is to describe the United Merchants and Manufacturers continuous foam processing method for the finishing and coloring of textiles. The term "continuous Is used to distinguish It from the batch foam dyeing process known as the Sancowad process developed and commercialized by the Sandoz Colors and Chemicals Co. (j6). 

Decolorization of aqueous solutions of dyes used in the textile industry may be accomplished via the use of ozone. Y.-C. Hsu, J.-T. Chen, H.-C. Yang, and J.-H. Chen [AIChE J 47, 169-176 (2001)] investigated the kinetics of the oxidation of C.I. Mordant Black and other dyes in a well-agitated reactor to which a gas containing ozone was fed continnonsly. Initially, decolorization occurs rapidly, but as the process continues, colored intermediates are formed. These intermediates are more recalcitrant to oxidation, but are destroyed as ozonation proceeds. These authors indicate that the concentration of dissolved ozone remains substantially constant so that the kinetics of this process can be treated as involving two consecutive pseudo first-order reactions ... 

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