Alpaca fiber impregnated with alizarine and indigo dyes in a process using supercritical carbon dioxide

Abstract

Supercritical carbon dioxide (scCO2) is an alternative medium for a drastic reduction of water for the impregnation of synthetic and natural fibers, especially azoic dyes. In this study, we evaluated the impregnation of alpaca fibers with alizarine and indigo dyes in a process with scCO2, using DMSO as a cosolvent for the dyes. The scCO2 flow rate ranged from 8 to 17.0 g/min over 90 min through a 1000 mL impregnation autoclave, and the amounts of dye:Al2(SO4)3 loaded were 15%:55% of the fiber weight, respectively. Impregnation was evaluated between 308.15 −363.15 K and 22.40 −13.37 MPa, and the products were characterized by FTIR spectroscopy. The highest impregnation obtained was 142.05 mg alizarine/g fiber at 311.15 K and 17.9 MPa and 260.80 mg indigo/g fiber at 329.15 K and 17.5 MPa. Color fastness analysis revealed that the colored fibers were resistant to water washing in the range of 4–5, a commercially accepted level for the fiber.