Лако-красочные материалы — производство

Cotton fibres are based on cellulose, a polysaccharide, whose structure is given in Figure 7.4. Most reactive dyes for cotton utilise the ability of the many hydroxy (OH) groups present in the cellulose molecule to act as nucleophiles. The dyes are commonly induced to react with the cellulose in aqueous alkali under which conditions deprotonation of the hydroxy groups (Cell-OH) takes place. This produces the more powerfully nuc­leophilic cellulosate anions (Cell-O _) which are generally regarded as the active nucleophiles in the reactive dyeing of cellulose. In the reactive dyeing of protein fibres, such as wool or silk, the nucleophilic group on the fibre may be the amino (-NH2), hydroxy (-OH) or thiol (-SH) groups present in the amino side-chains of the polypeptide (see Figure 7.1). The most common types of fibre-reactive dyes for cellulosic fibres react either by aromatic nucleophilic substitution or by nucleophilic addition to alkenes.