Лако-красочные материалы — производство

There is no doubt that the major weakness of the reactive dyeing process is the hydrolysis reaction and the consequent need for a wash-off process. The extent to which dye hydrolysis takes place in competition with dye-fibre reaction varies quite markedly within the range 10-40% de­pending upon the system in question. A considerable amount of research has therefore been devoted to the search for reactive dyes with improved fixation. The most successful approach to addressing this issue has in­volved the development of dyes with more than one fibre-reactive group in the molecule, which statistically improves the chances of dye-fibre bond formation. Examples of products of this type are the Procion H-E

range which contain two monochlorotriazinyl reactive groups, for example as represented by general structure 195 and some dyes of the Remazol range which contain two ^-sulfatoethylsulfone groups. These are examples of homo-bisfunctional dyes. Another approach utilises two different types of reactive groups, the so-called hetero-bisfunctional dyes, as for example structure 196 which contains both a monochlorotriazinyl and a ^-sulfatoethylsulfone group. This particular class of reactive dye, because of the differing reactivities of the two groups, can offer greater flexibility in performance, for example reducing sensitivity to tempera­ture and to pH variation. Although these bifunctional reactive dyes offer a significantly improved degree of fixation, the development of a practical reactive dye system which is completely free of the problems associated with hydrolysis or incomplete dye-fibre reaction remains an important target for dye chemists, and one which so far has proved elusive in spite of many years of research effort.