Regulation of symmetric polyfunctional reactive red dyes for ultra-high fixation on cellulose fibers in various dyeing and printing techniques

To achieve ultra-high dye fixation on cellulose fibers in various dyeing and printing techniques, the relationship between dye structure, physical properties, application techniques, and dyeing performances of nine symmetric polyfunctional reactive red dyes (MFB-1 to MFB-9) with different bridging groups was investigated. By altering the structure of the bridging group, the solubility of the nine dyes can be modulated within the range of 100–400 g/L, and their substantivity can be controlled from 20 to 90%. Using the pad dyeing technique, the fixations of MFB-1, MFB-3, and MFB-9 on cotton fabrics reached 97.16%, 96.82%, and 94.30%, respectively. The dyed cotton fabrics exhibited good levelness, with color difference values (ΔE) of less than 0.6. The dry rubbing fastness was grade 4 or 4–5, the wet rubbing fastness was grade 3 or 3–4, and the wash fastness was grade 4 or 4–5. MFB-2 and MFB-7 had the highest fixations on cotton fabrics using the exhaust dyeing technique, with values of 91.86% and 89.85%, respectively. The ΔE values for the dyed fabrics were 0.635 and 0.555, respectively. The dry rubbing fastness was grade 4, while the wet rubbing fastness was rated at either grade 2–3 or 3. The wash fastness was above grade 4. Additionally, MFB-4, MFB-5, and MFB-6 achieved ultra-high fixations of over 95% on cotton fabrics using both pad dyeing and printing techniques. The ΔE values for the dyed cotton fabrics from the pad dyeing technique ranged between 0.4 and 0.6, while the ΔE values for the printed fabrics were around 0.3. In both techniques, the dry rubbing fastness was grade 4 or 4–5, and the wet rubbing fastness was grade 3 or 3–4, with wash fastness rated at grade 4–5. MFB-8 achieved a fixation of 89.04% on cotton fabrics in cold pad-batch technique. The colored fabrics showed good levelness and color fastness, with a ΔE value of 0.365. The dry rubbing fastness was grade 4, the wet rubbing fastness was grade 3, and the wash fastness was grade 4 or 4–5. The results of the cross-sectional slice of fibers showed that all nine dyes can effectively penetrate the interior of cellulose fibers.