Regeneration of CI Sulfur Black 1 dyed cellulose through the viscose process

The aim of investigations here was to examine whether cellulose fibers dyed with CI Sulfur Black 1 (SB1), either alone or in combination with indigo (CI Vat Blue 1), may be dissolved and regenerated into fresh fibers with the viscose process. Hence, dyed cellulosic fibers dyed were subjected to the viscose process of spin dope preparation and regeneration to determine whether the dyestuff(s) survived in the cellulose or leached out into the process liquors. Multiple levels of the process parameters, as reported in literature, were examined. The results indicate that the SB1 dye, both alone and in combination with the indigo, survived in the cellulose and did not leach out. However, a change of color appearance was observed in the regenerates from fibers containing both SB1 and indigo, which is attributed to rearrangement in the distribution of dyestuff molecules. The research is part of a fiber-to-fiber recycling effort, where fiber polymers are to be extracted from used textiles and respun into fresh fibers for the production of new textiles. If the dyestuff could be retained in the polymer through dissolution/regeneration it would eliminate the need both for prior dyestuff removal and later redyeing of the regenerated fibers.