Dyeing processes are highly important for differentiation of textile products, and in general, they use a huge amount of water and chemical additives, generating a great environmental impact. In the last years, the interest in finding alternative environmentally friendly solvents for these processes has increased, with a double aim: to decrease the quantity of water used and to improve the dyeing quality. In this work, we analyze an alternative procedure to dye cotton fabrics with only two dyeing agents, a polyfunctional reactive dye and a protic ionic liquid (PIL) as an alternative solvent, avoiding the need for common chemical additives into the conventional process, thus reducing the amount and concentration of pollutants. The proposed procedure allows PIL recycling with no appreciable loss of efficiency, since after dyeing, the unfixed dye remains active in the bath, following the known exhaustion dyeing method. A collection of 13 PILs were studied with the aim of analyzing their effectiveness as dyeing solvents in terms of different standard dyeing quality parameters such as absorption color, tensile strength, and surface morphology of the cotton dyed. The results obtained using PIL as dyeing solvents in the absence of any auxiliary agent showed an outstanding effect when compared with the aqueous process under the same operational conditions.

This paper reports on the synthesis of five protic ionic liquids namely 2‐hydroxy ethylammonium acetate, 2‐hydroxy diethylammonium acetate, 2‐hydroxy ethylammonium propionate, 2‐hydroxy ethylammonium lactate, and 2‐hydroxy diethylammonium lactate and the study of shear and temperature dependency of the viscosity at the range 313.15–343.15 K. 1H nuclear magnetic resonance and Fourier transform infrared spectroscopy spectra establish the simple ionic salt structure of these compounds. Because of their polar character, these protic ionic liquids are able to dissolve polar solvents and inorganic salts, all of them showing high tolerance into hydroxylic media. The experimental results showed that the viscosity of these fluids decreases strongly with increasing temperature, being of non‐Newtonian trend over a range of shear rate. The parameters enthalpy of activation (ΔH*), free energy of activation (ΔG*), entropy of activation (ΔS*), and change in heat capacity of activation (ΔCp*) for their viscous flow were evaluated. The temperature dependence of viscosities was fitted using the power law, Litovitz, Vogel–Fulcher–Tammann, and Ghatee equations. Copyright © 2016 John Wiley & Sons, Ltd.

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The lower toxicological profile of the studied protic ionic liquids should guide their use as solvents for safe human use.