Synthesis and application of the starch ethers with benzenesulfonic acid groups for dye dispersion

Disperse dyes are virtually insoluble in water, necessitating the addition of substantial quantities of dispersants and extensive grinding to produce commercially viable dyes suitable for polyester fabric dyeing. In this study, a series of 2,4-bis(4-sulfonylanilino)-1,3,5-triazin-6-yl starch ethers (BSATS) with varying molecular weights were prepared through non-directive sulfonation of acid-degraded starch in an aqueous medium for application as disperse dye dispersants. The dispersing performance and underlying mechanisms of these dispersants were analysed. The results showed that the BSATS series of dispersants exhibited superior dispersing ability for disperse dyes. Compared with the commercial dispersant NNO (dye filtration time 68 s after treatment, dispersibility rating C, particle size change 68% after high temperature treatment), the dispersants BSATS 3–7 with molecular weights ranging from 13.2 × 10 4 to 21.0 × 10 4 g-mol −1 showed superior dispersibility (dispersibility rating B) and thermal stability (particle size change only 12% after high temperature treatment). Additionally, the BSATS dispersants were employed to disperse C.I. Disperse Orange 30 primary dyes, yielding uniformly dispersed dye liquors for polyester fabric dyeing. In terms of dyeing performance, the dye suspension containing BSATS dispersant achieved a dye uptake of 90% and colour fastness grades of 4–5. This study presents a methodology for the preparation of starch-based high-performance dye dispersants, thereby expanding the efficient utilisation of biomass starch in the printing and dyeing industry.