Acid Dyes on Wool

Acid dyes (see Sections 3.4.2 and 3.9), are made water-soluble by the introduction of sulfonic acid groups. Dissociation gives rise to dye anions that interact with the ammonium groups of the fiber 

Dyes with similar absorptive behavior should be selected for combined application. The combination values for acid dyes established originally for polyamide were later transferred to wool [86, 87], 

In dyeing, addition of salt has a retarding and leveling effect. Higher concentrations of sulfate ions are assumed to compete with dye anions for ammonium groups of the fibers, and inorganic salts exert an aggregating effect on dye molecules. 

Addition Leveling dyes Milling dyes Super-milling dyes 

Trichromic dyeing (matching shades with a standard combination of three dyes) can be conducted with leveling dyes. In the case of milling dyes, the desired shade is better achieved by selection of a dye with a hue similar to the required and shading. 

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Table 3.31 Migration properties of phenylazonaphthol acid dyes on wool [115]... 

This versatile water-soluble reactant has been evaluated in wool and nylon dyeing. The nucleophilic aminoalkyl derivatives of orthodox aminochlorotriazine dyes behave like traditional acid dyes on wool owing to their zwitterionic character under neutral-dyeing conditions (Scheme 7.65). Improved wet fastness can be achieved using the reactant XLC... 

Table 4.3. Dyeing with acid dyes on wool...

Low foaming dispersing agent. Levelling agent for acid dyes on wool. 

Chromosol. [Ni]q>on Senka] Silicon complex fir g s ent for acid dyes on WOOL... 

Reflectance spectroscopy - Some acid dyes on wool and nylon [150]... 

Evolution of ammonia from a boiling dilute solution of diammonium phosphate gradually reduces the pH. This process is used commercially to control the precipitation of alkaH-soluble—acid-insoluble coUoidal dyes on wool. Other ammonium orthophosphate salts of interest are ammonium hemiphosphate [28537-48-6] NH4H2PO4 H3PO4, and its hydrate [28037-74-3], as well as the trihydrate [78436-07-4] of DAP. 

Sodium dichromate and various chromic salts are employed in the textile industry (195,196). The former is used as an oxidant and as a source of chromium, for example, to dye wool and synthetics with mordant acid dyes, oxidi2e vat dyes and indigosol dyes on wool, aftertreat direct dyes and sulfur dyes on cotton to improve washfastness, and oxidi2e dyed wool. Premera11i2ed dyes are also employed. These are hydroxya2o or a2omethine dyes in which chromium or other metals are combined in the dye (see Azine dyes DYES Azo dyes). 

The dye-fibre systems of obvious interest for approach (b) are milling acid and 1 2 metal-complex dyes on wool or nylon, basic dyes on acrylic fibres and disperse dyes on various fibres. With wool and nylon there is often some overlap with approach (c) (section 12.2). 

The kinetic behaviour of anionic dyes on amide fibres tends to be much more closely related to molecular size and hydrophilic-lipophilic balance. Thus within a related series of dye structures it is possible to discern more specific relationships. For example, in the series of p-substituted aniline—>R acid dyes (3.91 R = H, methyl, n-butyl or n-dodecyl) the logarithm of the rate of dyeing on wool is inversely proportional to the molecular volume [110]. 

Catalytic fading of certain mixtures of acid dyes on nylon, wool and their blends is a particularly significant problem of dye selection for carpets [165]. Xenotest ratings as low as 3-4 (much bluer) were found for green shades on nylon containing an azopyrazolone component such as Cl Acid Yellow 19 (3.150), which fades much more rapidly in the presence... 

Dibasic ammonium phosphate is used as a fertilizer as a fire extinguisher a flame retardant for plywood, papers, and fabrics to prevent afterglow in matches in purifying sugar as a flux for soldering tin, copper, zinc and brass and to control precipitation of alkah-soluble or acid-insoluble coUoidal dyes on wool. 

Dyes based on these compounds possess, in addition to good lightfastness, excellent wetfastness and are usually neutral-dyeing on wool. This, although of no importance for dyeing pure wool, plays an important role in dyeing blended spun yam and blended fabrics of wool and cotton or wool and viscose staple. The neutral-dyeing acid dye can be used in combination with direct dyes (union wool recipes). Examples are C.I. Acid Yellow 56, 24825 [6548-24-9] (17), and C.I. Acid Red 154, 24800 [6507-79-5] (18 R = CH3). 

The synthesis of the 1 1 complex 8 is an example of [10] demethylative chroma-tion. It is prepared by diazotization of 5-amino-2-chlorohydroquinone dimethyl ether and coupling onto 1-hydroxynaphthalene-5-sulfonic acid. The reaction product and Cr203 in formic acid are heated in an autoclave at 130 °C. The chromium complex 8 [80004-31-5] is obtained as a black powder that gives grayish blue dyeings on wool and leather. 

As an example of 1 2-chromation by the dichromate-glucose method [20], the azo dye obtained by coupling of diazotized l-amino-2-hydroxy-5-nitrobenzene with l-methylsulfonylamino-7-hydroxynaphthalene is dissolved in dilute NaOH and boiled after addition of K2Cr20r2H20 and glucose. Chromation is complete after a few minutes. The resulting 1 2 chromium complex 12 [83748-22-5] is precipitated with NaCl to give a black powder that imparts bluish olive dyeings on wool in a weakly acidic dyebath. 

Acid and Metal-Complex Dyes on Wool and Silk... 

Fastness Improvement. The wetfastnesses of dyeings on wool that has been chlorinated to prevent felting and has received a finish with synthetic resin (poly-amide-epichlorohydrin or polyurethane superwash wool) can be increased by means of methylol amide compounds. Both fastness and antifelting finish can be improved through the application of a polyquatemary compound [88]. Anionic condensation products such as aromatic sulfonic acids with formaldehyde can form a barrier at the surface of the fiber and thus diminish the bleeding of anionic dyes. 

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