Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The study assesses dye impacts on PA66/wool recycling via selective PA66 dissolution in calcium chloride–ethanol–water and water reprecipitation. Acid dyes migrate into solvent, yielding color-free, melt-spinnable PA66 and reusable wool. Metal-complex dyes remain, altering PA66 melt viscosity and requiring extraction or repurposing. No polymer damage occurred.

ABSTRACT
The study examines how dyes affect fiber-to-fiber recycling of PA66/wool blends using selective dissolution of PA66 in a calcium chloride–ethanol–water (CEW) solvent and reprecipitation with water. Acid dyes migrated into the CEW solvent, freeing both PA66 and wool from colorants. The recovered PA66 could be directly melt-spun back into fibers, and wool remained reusable. In contrast, metal-complex dyes stayed bound to both fibers. While this did not hinder wool reuse, the retained dye in PA66 reprecipitates changed melt viscosity, undermining direct melt spinning. Consequently, additional steps to extract metal-complex dyes or repurpose the dyed polymer in other applications are needed. No evidence of polymer or fiber degradation was observed for either PA66 or wool due to dyes or solvent exposure. Observations suggest leached dyes formed calcium “lakes,” yielding pigment-like species in the solvent, which could be harvested for coloration of plastics or materials, offering routes to valorize waste-textile streams.