Energy with disperse dyes

Acetate fibers are dyed usually with disperse dyes specially synthesized for these fibers. They tend to have lower molecular size (low and medium energy dyes) and contain polar groups presumably to enhance the forces of attraction by hydrogen bonding with the numerous potential sites in the cellulose acetate polymer (see Fibers cellulose esters). Other dyes can be appHed to acetates such as acid dyes with selected solvents, and azoic or ingrain dyes can be apphed especially for black colorants. However thek use is very limited. 

Much of the available published data on the aqueous solubility of disperse dyes was accumulated during the 1960s in the course of studies of the mechanism of dyeing cellulose acetate with disperse dyes. Most of the dyes examined were low-energy types for dyeing acetate (Table 3.5). Particular attention was given to monoazo dyes derived from aniline or... 

Table IX. Energy Savings for Pilot-Scale Dyeings Nylon with Disperse Dyes (5 Cycles)...

FiaaHy, ia method (4) the fabric is padded with a mixture of medium energy disperse dyes, carehiUy selected higher reactivity, and rapid diffusiag fiber-reactive dyes, up to 10 g/L sodium bicarbonate depending on depth of shade, and proprietary auxiHary agents. 

Brightener structures of only moderate molecular size are of interest for white grounds in the transfer printing of polyester fabrics. Derivatives of 6-acetamidoquinoxaline with an electron-donating substituent (X) in the 2-position (11.48) were prepared by converting quinoxalin-2-one to 2-chloro-6-nitroquinoxaline and condensation with amines (X = RNH), alcohols (X = RO) or phenols (X = PhO), followed by reduction and acetylation (Scheme 11.19). The nitro intermediates (11.49) are also of interest as low-energy disperse dyes for polyester [61]. 

Conversation with the dye manufacturer revealed a mistake had been made in recommendation of the disperse dye to be used in conjunction with the high-energy reactive dye. The recommended dye was an azo-based dye that was not stable to base at high temperatures, and degradation caused the purplish shade shift observed in the research. For future investigations, an anthraquinone-based disperse dye that is base-stable at 170°C has been recommended by the manufacturer for use with the high-energy reactive dye. 

Good lot-to-lot shade correlations were also obtained with reuse of low-temperature reactive dyebaths and fixation baths on 100% cotton, and with reuse of combined high-energy reactive/disperse dyebaths and fixation baths on cotton/polyester knit fabrics. Further computer program development is required, however, before industrial shades can be matched with the reactive dye reuse system. 

Table 4.22 Decrease in the interaction energy (AC/dy -PLA) between various disperse dyes with a diphenyl monoazo or tetrahydrothiophenyl phenyl monoazo parent structure and PLA after a given substituent is removed (group removed) fi-om the dye and replaced with an —...

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