Studies on the Relationship between the Chemical Structure and the Lightfastness for Disperse and Reactive Dyes with High Lightfatness.

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Reactivity of an aminopyrazolinyl azo reactive dye, used for the estimation of photosensitivity of many reactive dyes, was examined by PM3 semi-empirical molecular orbital method to show the position of reaction with singlet molecular oxygen, the reaction paths, and the relative reactivity of typical monoazo dyes.The photofading behavior of six monoazo disperse dyes on poly(ethylene terephthalate)(PET)and nylon 6 films and fabrics was examined under aerobic and anaerobic conditions. The dyes underwent reductive fading even under aerobic conditions, with a few exceptions. Exposing nylon films dyed with the disperse dyes in combination with a vinylsulfonyl copper-phthalocyanine dye(CuPc), when immersed in aerated or O_2-saturated water, showed a decrease in the rate of reductive fading compared with exposures involving disperse dyes without CuPc. Singlet oxygen generated by the photosensitization of CuPc suppressed the reductive fading of disperse dyes. Nylon has stronger influence to un … More dergo photo-reduction and photo-oxidation on disperse dyes than PET has, depending upon the potential properties of dye itself. High lightfastness in disperse dyes requires ^1O_2-suppressed photo-reduction due to their self-photosensitization during exposures involving aerobic conditions.Monomer-dimer equilibriums of triphenodioxazine reactive dyes with vinylsulfone anchors(PVS-TPDO)and monochlorotriazine anchors(MCT-TPDO)were investigated in water, in aqueous organic solvent, and on a cellulosic substrate. The aggregation tendency of PVS-TPDO in water was promoted by the addition of neutral electrolyte and suppressed by that of 1-methyl-2-pyrrolidone(MP). PVS-TPDO showed also aggregation on a cellulosic substrate. The apparent value of K on dry cellulose was two orders of magnitude smaller than that in water, and was increased by about ten times by water. Four TPDO dyes examined showed the same order of aggregation tendency on cellulosic and nylon substrates as that in aqueous solution.The reaction of four triphenodioxazine(TPDO)reactive dyes on cellulosic films with bleaching agents, hypochlorite and hydrogen peroxide(HP), was examined in the aqueous solutions and redox potentials for two dyes were measured by cyclic voltammetry. The reaction of TPDO dyes on cellulosic films with HP at different pHs implied a nucleophilic reaction with HP anions, while the reaction with hypochlorite an electrophilic one with undissociated species of hypochlorite and a nucleophilic one with hypochlorite anion, although the relative reactivity among TPDO dyes was attributed mainly to the electrophilic one. The rates of hypochlorite bleaching for 4, 11-bis(vinylsulfonyl)TPDO dyes on cellulosic film were smaller than those for 3, 10-bis(disubstituted triazinyliminoethylimino)TPDO dyes, while the rates of HP bleaching showed the reverse relation. Less