Light fastness dye

The use of 2-aminothiazole derivatives as dyeing compounds is direct related to the development of synthetic fibers. Some typical examples are given in Table VI-14. The importance of these dyes lies in their performance on acetate fibers. They have excellent fastness to gas fumes, produce a bright blue shade, and have a high tinctorial strength. Their only disadvantage is their relatively low light fastness, which does limit their application. 

Pyrazolone derivatives have found many applications as cotton azo dyes because, even if they were more expensive intermediates, they improved qualities such as brightness and light fastness. Rosanthrene Orange (727) and Pyrazol Orange (728) are two representative examples. 

Amination A/-Methylolacrylamide in presence of Lewis acid catalyst. Further modifications possible by addition to double bond (Scheme 10.61) Amines with durable press resins Improved dyeability with dichlorotriazine dyes at pH 5 without salt, giving 99% fixation Some improvements in dyeability, especially with direct dyes, but light fastness can be a problem... 

Enhanced dyeability with anionic and reactive dyes, the latter applied under neutral or slightly acidic conditions. Reduced light fastness and marked dulling with some dyes... 

Dyeable neutral without salt good results with some high-reactivity dyes (dichlorotriazine and difluoropyrimidine) but not with some other types (monochlorotriazine and dichloroquinoxaline). Washing fastness very good but light fastness lower... 

Ethylenediamine derivative of Hercosett Scheme 10.64 About 95% fixation of low- or high-reactivity dyes under slightly acidic conditions without salt, but light fastness still inferior... 

Polyepichlorohydrin and dimethylamine Polymerisation of epichlorohydrin in carbon tetrachloride with boron trifluoride/ether catalyst, then reaction with dimethylamine. Applied to cotton by exhaust method or pad-dry. Scheme 10.65 Good yields with direct dyes using only 2 g/l salt. Excellent build-up with most reactive dyes only 10% of normal salt usage needed for low-reactivity dyes and none for highly reactive types. Washing fastness very good but light fastness impaired. 

A third approach utilised copper salts, especially copper(II) sulphate, in conjunction with dyes containing chelatable groupings such as salicylic acid or o,o -dihydroxyazo moieties. Indeed, special ranges of copperable direct dyes, for which the treatment with copper(II) sulphate was really part of the dyeing process rather than an optional aftertreatment, were introduced. In the past the main use of this chelation treatment was to enhance light fastness, but it is little used for this purpose nowadays. 

Antimicrobial agents may adversely affect the light fastness of nylon dyeings or cause yellowing of the fibre. The six antimicrobial treatments listed in Table 10.51 have been... 

For the synthesis of these pigments the dye molecules must possess a high light fastness. The colors are not very bright, and because of the thin dye layer these pigments are more susceptible to an oxidative photo degradation than normal pigments. 

Most of these products are azo or anthraquinone types, often with a localised quaternary ammonium group isolated from the chromogen by a saturated alkyl chain, as in Cl Basic Red 18 (1.52). Such products often exhibit higher light fastness than the traditional delocalised types. Improved azomethine, methine and polymethine basic dyes of good light fastness are also available. In contrast to the more specialised traditional classes, the azo and methine dyes have contributed to the basic dye range across the entire spectrum of hues (see Table 1.6) and now account for a clear majority of all basic dyes listed in the Colour Index. 

Other dyes that were extensively precipitated for use in printing inks were erioglaucine (2.1) and eosine (2.2) but their light fastness is too low to be acceptable nowadays. The process was called laking and the products were termed lakes . 

Many other dyes, including tartrazines and eosines, have been made into pigments in the past for use in printing inks, in which their soft texture and bright hues were much valued. Their light fastness was generally only 1 on the ISO scale and they are now obsolete. 

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