Wet fastness

Dye for polyacrvlonilrilc liber light and wet fast yellow shade... 

Other disazo dyes with good substantivity and high wet-fastness properties on polyamides are Acid Red 114 (40), made by coupling o-toHdine to phenol which is then coupled to G-acid, followed by reaction of the phenoHc hydroxyl group with -toluenesulfonyl chloride, and Acid Blue 113 (41) (metanilic acid — 1-naphthylamine — 8-anilino-1-naphthalenesulfonic acid). 

Dyes for cellulose fiber include the direct, sulfur, vat, a2oic, and reactive dyes. R D activities of world dye manufacturers have been focused on the area of reactive dyes, because reactive dyes offer brighter shades and excellent wet-fastness and have been increasingly used for dyeing cotton. 

Traditional syntan treatments are rather ineffective for improving the wet fastness of anionic dyes on wool, mainly because of weakness of the interaction between syntan and fibre. It is therefore not surprising that covalent reactive systems have been explored to find more effective aftertreatments and dye-resist treatments for this fibre. In an initial study... 

The fact that the aftertreatment of direct dyes has a long history is not surprising since wet fastness within this class is not particularly good. Their prime advantages are ease of application and economy compared with dyes of higher fastness (reactive, sulphur or vat) -hence the continued search for highly effective aftertreatments that improve wet fastness... 

Only the products associated with acid and premetallised dyes are dealt with in this section. The auxiliaries used with mordant dyes are covered in section 5.8. Anionic acid dyes, applied principally to wool and nylon, vary widely in their fastness and level-dyeing properties (section 3.2.2) in general, the higher the wet fastness of a dye the more difficult it is to apply evenly. Hence it is not surprising that the use of auxiliaries with acid dyes is related mainly to level-dyeing properties. There are two basic aspects ... 

Levelling acid dyes and particularly 1 1 metal-complex types generally require an exceptionally low pH in order to promote exhaustion and levelling up to 3% o.w.f. sulphuric acid is most commonly used for levelling acid dyes, although hydrochloric, formic and phosphoric acids are also effective. In the case of conventional 1 1 metal-complex dyes it is essential to use a sufficient excess of acid over and above the typical 4% o.w.f. sulphuric acid normally absorbed by the wool, otherwise there may be a tendency towards tippy dyeings and lower wet fastness. The actual excess required depends on applied depth and liquor ratio [2] typical recommendations are given in Table 12.2. 

The washing-off of prints is best carried out with anionic polycondensation products of arylsulphonic acids [29] since these can improve the wet fastness of anionic dyes. 

Direct dyes are of limited interest for printing because of their restricted wet fastness, resulting in cross-staining of whites or pastel-dyed grounds when the prints are subsequently washed. Somewhat better results can be achieved by treating the prints after steam fixation... 

Disulphonated dyes of relative molecular mass (Mr) about 400-600 that are somewhat sensitive to dyeability differences in the substrate and show the lowest wet fastness of all dye classes used on wool... 

Monosulphonated dyes of lower Mr (300-500) and slightly higher wet fastness that migrate more readily and cover dyeing faults (such as carbonising damage) more effectively. 

Monosulphonated dyes of Mr 500-600 are somewhat more hydrophobic than the monosulphonated levelling acid dyes. They also migrate and cover well but they are a little inferior to disulphonated milling dyes in wet fastness and thus have sometimes been described as half-milling dyes ... 

Disulphonated dyes of Mr 600-900 diffuse much more slowly than typical levelling acid dyes. Thus they exhibit correspondingly higher wet fastness but their migration and coverage properties are inferior ... 

The increase in affinity for wool imparted to acid dye structures by the inclusion of long-chain alkyl groups has a noteworthy effect on wet fastness. Thus the incorporation of such a group into the levelling acid dye Cl Acid Red 1 (3.129 R = H) to form the super-milling acid dye Red 138 (3.129 R = n-dodecyl) raises the fastness to washing at 50 °C (effect on pattern) from 2-3 to 4-5. Similar effects for a series of alkylated phenylazo-2-naphthol-6-sulphonate dyes are recorded in Table 3.41. 

Table 3.42 Wet fastness of substituted phenylazo J acid dyes on silk [156]...

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