Optimization of an eco-friendly dyeing process in both laboratory scale and pilot scale supercritical carbon dioxide unit for polypropylene fabrics with special new disperse dyes

A new synthetic route was developed to create azo based dispersed dyes which are derived from 3-(3-Chloropheney)-2-((4-substituted) diazenyl)-3-oxopropanenitrile and 3-substituted 5-amino-4-arylazopyrazoles. The new dyestuff was used to dye unmodified polypropylene fabrics under both aqueous and supercritical carbon dioxide mediums. A pilot scale experiment was performed on the dyestuff 3a to prove the potentiality of the dyestuff toward polypropylene fabric. The new dyes were characterized by MS, IR and NMR spectral data and found to be in good agreement with the proposed structures. The colour uptake expressed as colour strength (K/S) was assessed and the values obtained showed that the dyed polypropylene fabrics using scCO2 method was significantly better than the aqueous one. The colour fastness properties of all the dyed fabrics were evaluated and exhibited excellent results. Moreover, it is also a green approach for using industrial emissions of CO2 instead of water in the textile dyeing process.