PHOTOFADING OF VINYLSULFONYL REACTIVE DYES ON CELLULOSE UNDER WET CONDITIONS

The fading on cellulose of six vinylsulfonyl (VS) reactive dyes, an aminopyrazolinyl azo dye (1). C.I. Reactive Red 22 (2), a copper-complex azo dye (3), a copper phthalocyanine dye (4), C.I. Reactive Blue 19 (5) and Black 5(6) was investigated under wet conditions. The rate of fading for VS dyes on cellulose, except for dye 2, decreased with increase in the concentration; that for dye 2 increased. The rate of fading for the VS dyes examined was in the following order: 2 > 1 > 3 > 6 > 4 > 5. This order was similar to that for the rate of fading for VS dyes on cellulose on which Rose Bengal was adsorbed, except for the reversal between dyes 1 and 2. The photosensitivity of VS dyes was confirmed by exposing films dyed with a mixture ofl with the other dyes and by shielding dye 1 by the use of a filter (5̌10nm). No fading of these dyes on cellulose in deaerated water occurs under a nitrogen atmosphere. These results suggest a singlet oxygen mechanism for the fading of VS dyes on cellulose under wet conditions. The rate of fading for a VS dye was dependent mainly on the ease with which it was oxidized and secondly on its efficiency and that of the partner dye to generate singlet oxygen. © 1990.