Eco-Friendly Sulfur Dyeing of Cellulosic Woven Fabrics

Abstract

This work demonstrated that conventional sulfur dyeing, which poses environmental problems, can be modified by using safer chemicals. The results indicate that: i) using reducing sugars as eco-friendly reductants results in an improvement in the extent of coloration; ii) the extent of improvement is determined by the reductant type; i.e., liquid glucose (LG) > thiourea dioxide (TUD) > glucose (G) > molass (M), dye/reductant ratio, as well as type of woven cellulosic fabric; i.e., viscose > cotton > linen; iii) raising the dyeing temperature to 80°C for 45 min, increasing NaCl concentration to 30 g/L, and/or minimizing the material-to-liquor ratio to 1/10 brings about an improvement in the extent of coloration; iv) efficiency of dye fixation is determined by the nature of the oxidant and follows the descending order (NH₄)₂ S₂O₈ > Na-perborate > H₂O₂ > none; and v) post-softening has positive impacts on the softness degree and washing fastness, as well as rubbing fastness properties, especially in the case of using the cationic softener, regardless of the sulfur dye used.

Keywords:

• Cellulose
• Ecology
• Reducing sugars
• Sulfur dyeing
• Woven fabric

Notes

Hydron® Blue R (4% owf); NaOH (5 g/L); wetting agent (2 g/L); NaCl (45 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: H₂O₂ (2 g/L; 35%); acetic acid (2ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Hydron® Blue R (4% owf); dye/reductant ratio (1:1 in case of using G, LG, or TUD, and 1:6 in case of using M); NaOH (5 g/L); NaCL (45 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 70–90°C/45 min.

Oxidation: H₂O₂ (2 g/L; 35%); acetic acid (2 ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Hydron® Blue R (4% owf); dye/reductant ratio (1:1 in case of using G, LG, or TUD, and 1:6 in case of using M); NaOH (5 g/L); NaCl (0–45 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: H₂O₂ (2 g/L; 35%); acetic acid (2 ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Hydron® Blue R (4% owf); dye/reductant ratio (1:1 in case of using G, LG, or TUD, and 1:6 in case of using M); NaOH (5 g/L); NaCl (30 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: H₂O₂ (2 g/L; 35%); acetic acid (2 ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Hydron® Blue R (4% owf); dye/reductant ratio (1:1 in case of using G, LG, or TUD, and 1:6 in case of using M); NaOH (5 g/L); NaCl (30 g/L); non-ionic wetting agent (2 g/L).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: H₂O₂ (2 g/L; 35%); acetic acid (2 ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Hydron® Blue R (1–6% owf); dye/reductant ratio (1:1 in case of using G, LG, or TUD, and 1:6 in case of using M); NaOH (5 g/L); NaCl (30 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: H₂O₂ (2 g/L; 35%); acetic acid (2 ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Sulfur dye (4% owf); dye/reductant ratio (1:1 in case of using G, LG, or TUD, and 1:6 in case of using M); NaOH (5 g/L); NaCl (30 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: H₂O₂ (2 g/L; 35%); acetic acid (2 ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Dye (4% owf); dye/reductant ratio (1:1); NaOH (5 g/L); NaCl (30 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: H₂O₂ (2 g/L, 35%); acetic acid (2 ml/L); at 70°C/20 min.

LG: liquid glucose; TUD: thiourea dioxide; WF: wash fastness; RF: rubbing fastness; LF: light fastness; A: alteration; St.: staining on white cotton; D: dry; W: wet.

Sulphur dye (4% owf); dye/reductant ratio (1:1 in case of using G, LG, or TUD, and 1:6 in case of using M); NaOH (5 g/L); NaCl (30 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: (2 g/L); acetic acid (2 ml/L); at 70°C/20 min.

K/S: color strength; G: glucose powder; LG: liquid glucose; TUD: thiourea dioxide; M: molass.

Sulfur dye (4% owf); dye/reductant ratio (1:1); NaOH (5 g/L); NaCl (30 g/L); non-ionic wetting agent (2 g/L); LR (20:1).

Reduction at 70°C/15 min.; Dyeing at 80°C/45 min.

Oxidation: (NH₄)₂S₂O₈ (2 g/L); acetic acid (2 ml/L); at 70°C/20 min.

Softening: softener (3% owf); LR (20:1); pH 5; at 50°C/20 min.

LG: liquid glucose; TUD: thiourea dioxide; K/S: color strength; SR: softness rating; WF: wash fastness; RF: rubbing fastness; LF: light fastness.