Relationship between photochemical properties and colourfastness due to light-related effects on monoazo reactive dyes derived from H-acid,gamma-acid,and related naphthalene sulfonic acids

摘要

Photofading of 15 reactive azo dyes derived from H-(seven),J-,L-,R-,2R-,gamma-acids (three),pyrazoline and reactive copper-complex dye on cellophane under wet conditions was examined to estimate the essential properties:photooxidisability (k_0:the reativity with moleuclar singlet oxygen),photosensitising ability (f)and photo-reductivity.The relationships between the essential properties of these dyes and the lightfastness (LF)as well as the perspiration-light-fastness (PLF)on cotton fabrics are discussed.A linear correlation between the logarithmic product,log (f k_0),and the LF ratings of dyes on dry cotton fabric was found when plots of reactive dyes with low LF and those of the vat dyes examined in a previous paper were added because the ratings of 11 red dyes out of 15 dyes examined had a narrow range.It showed that LF of monoazo red reactive dyes on dry cotton fabric is very dependent on photo-oxidative fading.A linear correlation was also found between logarithms of f-values and the relative initial rates of photoreductive fading,except for dyes with very high photosensitising ability.A conicting relationship between the k_0-values and the photo-reductivity could be shown for dyes derived from H-and gamma-acids,an unsolved restriction on synthesis of azo dyes with excellent LF as well as PLF.Azo dyes derived from gamma-and 2R-acids possess smalle f but larger k_0 values than those derived from H-acids.The photofading of dyes on cotton fabrics in the presence of artificial perspiration was explained in terms of the essential ropertis.The substrates promoted photo-reduction adn suppressed photo-oxidation.