In-fibre formation of Fe(OH)3—a new approach to pigment coloration of cellulose fibres

Abstract In alkaline solution a ligand exchange reaction between dissolved Fe(III)– d -gluconate complexes and cellulose fibres occurs. This reaction can be used to insert Fe(III)-ions in cellulose fibres. During rinsing the complex stability of the Fe(III)–cellulose complex is lowered and precipitation of Fe(III)-hydroxide inside the cellulose fibre occurs. This process permits pigment dyeing of cellulose fibres with in-situ in-fibre formation of the pigment. The impregnation was performed as an exhaust method at 80 °C using solutions Fe(III)– d -gluconate complexes with c(Fe 3+ ) 0.25–3.75 mmol l −1 and c( d -gluconate) 0.5–7.5 mmol l −1 . Due to the higher complex stability of the fibres iron concentrations in the fibre were determined with 2.7–14.8 mmol Fe per kg of fibre. Excellent fastness properties of the dyeings were found with light fastness of 7–8 and wet fastness of 5.