Single-step synthesis and energy-efficient coloration of wool textiles with poly(amino naphthalene sulfonic acid)-based dyes by oxidation polymerization

In the context of sustainability, energy-efficient low-temperature dyeing with non-toxic polymeric dyes is attractive. In this work, a single-step method of simultaneous synthesis of polymeric dyes from non-toxic amino-naphthalene sulfonic acids (ANSAs) by the oxidation polymerization and energy-efficient coloration of wool fabric was developed. The studied monomers are 7-amino-1,3-naphthalene monopotassium disulfonate (ANSA-1), 4-amino-1-naphthalene sulfonic acid (ANSA-2), and 5-amino-2-naphthalene sulfonic acid (ANSA-3). The prepared polymeric dyes were characterized by UV–vis, Fourier transform infrared (FT-IR), and mass spectrometry, and gel permeation chromatography (GPC). The mass spectra suggest that oxidation treatment of ANSA-1 formed only dimers but the other two ANSAs formed polymers, whereas the GPC data demonstrated successful polymerization of all three ANSAs. The treated fabrics were characterized by thermogravimetric analysis, and FTIR and reflectance spectroscopies. The treatment parameters, including the monomer and oxidant concentrations, treatment pH, temperature, and time, affected the shade of the color produced and its intensity. The optimum conditions for dyeing with ANSAs were 50 °C, 120 min, and a 1:1 monomer to oxidant ratio. The treatment with these ANSAs produced various colors in the fabric including tonal changes. The colorfastness to washing increased with an increase in the treatment temperature and time. The shade of color produced and the color intensity were dependent on the position of the substituent sulfonate groups in the amino-naphthalene compounds. This developed treatment can be used for the energy-efficient dyeing of wool and other polyamide fibers with good colorfastness to washing.