Acid Silk Dyes

It is used in the dispersed form as a dye for acetate silk, though it has no affinity for other fibres. It is also used as a starting point for alkyl- or acyl-aminoanlhraquinones which are used either as vat dyes or, after sulphona-tion, as acid wool dyes. 

Azo dyes with relatively low molecular masses and one to three sulfonic acid groups serve as acid azo dyes for dyeing and printing wool, polyamide, silk, and basic-modified acrylics and for dyeing leather, fur, paper, and food. The main area of application is the dyeing of wool and polyamide. 

Of great importance for the dyeing of natural silk are selected members of the class of acid wool dyes (see above). The occasionally inadequate wetfastness of these dyeings can be substantially improved by the proper aftertreatment (e.g., with potassium sodium tartrate and tannin). 

Selected acid 1 1 chrome complex dyes, because of their good wet- and lightfastness and their very good leveling power, and also 1 2 chrome complex and 1 2 cobalt complex dyes with hydrophilic groups, have successfully come into use as silk dyes. 

Textiles Acid dyes are characterized by the presence of one or more water soluble anionic groups which is typically a sulphonic acid. These dyes are applied to nitrogenous materials such as wool, silk, nylon or modified acrylics. They are not fast to cotton. 

The azo yellow prepared in this way is quite insensitive to dilute mineral acids, but is not satisfactory for certain purposes in silk dyeing. By using more nitric acid and more vigorous conditions, grades of azo yellow are produced which are more greenish in shade and completely fast to acids. 

Tropliolin 0 is a strong dyestuff, producing a fine golden-yellow shade on wool and silk, being dyed from an acid bath. It was formerly used in silk-dyeing. 

The ethyl ether, in form of its sodium or potassium salt, is extensively used in silk-dyeing as spirit eosin or primerose h kalcool/ For use, the commercial product is dissolved in spirit and gradually added to the dye-bath, which is acidified with acetic acid. 

The fluorescein derivatives containing chlorine are much bluer in shade than the corresponding derivatives of ordinary fluorescein. Their principal application is in silk-dyeing. Rose Bengal prepared from tetrachlorphthalic acid is the bluest of these dyestuffs, while Phloxin from dichlorphthalic acid is the yellowest. 

Archil is principally employed in wool and silk dyeing, less in calico-printing. It may be dyed on wool from acid, neutral, or alkaline baths. An addition of alum, stannous chloride, oxalic acid, or tartaric acid is made to the dyebath. 

To prepare carthamin, safflower is washed with water to remove the yellow dyestuff, and is then extracted with dilute soda solution, and filtered. Cotton yarn is immersed in the alkaline solution, and the liquid acidulated with citric acid. The cotton takes up the carthamin, which is removed with soda solution, and precipitated with citric acid. Obtained in this manner carthamin forms a lustrous green powder, sparingly soluble iu water and ether, readily in alcohol. It dissolves in alkalies with yellowish-green colour. On fusion with potash it gives oxalic acid and para-oxy-benzoic acid. Carthamin dyes animal fibres and unmordanted cotton from a slightly acid bath. It produces a beautiful pink colour on silk. 

Make a dye bath by dissolving 0.1 gram of malachite green in 500 cc. of water. Add to the bath a piece of boiled-out cotton which has not been mordanted, the piece of cotton mordanted with tannic acid from which most of the solution has been removed by pressure, the piece of cotton cloth on which the tannic acid was fixed by tartar emetic, a piece of wool, and a piece of silk. Dye for 15 minutes at a temperature just below boiling. Work the pieces over and over with a rod occasionally to obtain even dyeing. 

Langmuir type absorption isotherms are observed when only a limited number of dye sites are available inside the fibre. In this case the concentration of (fye in the polymer reaches a maximum limiting level as the concentration of dye in the dyebath is increased. This behaviour is typical of acid levelling dyes on wool and silk. " ... 

Mitsuishi M., Yaqi T, Jian X., Hamada K., Ishiwatari T. (1992), Silk Dyeing in Acid Dyes Results of Equilibrium and Kinetic Studies for the Mixture Dyeing of Silk with Acid Dyes Textile Asia 23,4, 92-5. 

Most xanthene dyes are classified as basic dyes by their method of appHcation acid dyes can be produced by introduction of sulfonic acid groups. The fluoresceins, which contain carboxy and hydroxy substituents, are also acid dyes for coloration of silk. Some of the fluoresceins in which the carboxy group has been esterified, are soluble in alcohol or other organic solvents and can be classified as solvent dyes. Mordant dyes can be produced by introducing o-dihydroxy or sahcyhc acid groups (2), which when metallised can have very good lightfastness. 

Picric Acid and Ammonium Picrate. Picric acid (PA) (2,4,6,-trinitrophenol) was the first modem high explosive to be used extensively as a burster ia gun projectiles. It was first obtained by nitration of iadigo, and used primarily as a fast dye for silk and wool. It offered many advantages when compressed, it was used as a booster for other explosives, and when cast (melting poiat 122.5°C) served as a burster ia shell it was stable, iasensitive, nonhygroscopic, relatively nontoxic, and of high density when cast, and could be made economically by simple nitration. 

Qiana, introduced by Du Pont in 1968 but later withdrawn from the market, was made from bis(4-aminocyclohexyl)methane and dodecanedioic acid. This diamine exists in several cis—trans and trans—trans isomeric forms that influence fiber properties such as shrinkage. The product offered silk-like hand and luster, dimensional stabiUty, and wrinkle resistance similar to polyester. The yam melted at 280°C, had a high wet glass-transition temperature of - 85° C and a density of 1.03 g/cm, the last was lower than that of nylon-6 and nylon-6,6. Qiana requited a carrier for effective dyeing (see Dye carriers). 

Because it is also a proteia, silk can be dyed as wool, but ia practice the dyes used are generally acid dyes ia view of the fiber not being treated to any severe washing ia its life. The main difference between wool and silk is ia the preparation of the fiber for dyeiag. 

Printing of wool or silk with acid dyes is of minor importance. For these fibers the print paste is made with dye solvent, humectant (glycerol and urea), a suitable thickener, and dilute organic acid. An oxidising agent is also added. Fixation follows the procedure for polyamide with fully saturated steam. 

T artrazine, 4,5-dihydro-5 -oxo-1 -(4-sulfophenyl)-4-[(4-sulfophenyl)azo]-1// -pyrazole-3-carboxylic acid trisodium salt was discovered by Ziegler in 1884 and is used as a dye for wool and silk. It is used as a colour additive in foods, drugs and cosmetics, and is an adsorption-elution indicator for chloride estimations in biochemistry (B-76MI40404). 

According to Urbanski (Ref 35. p 473) In the second half of the nineteenth century, Picric Acid was very widely used as a fast dye for silk and wool. The first definite suggestions as to the application of Picric Acid for the manufacture of explosives go back to the early second half of the nineteenth century. They referred... 

The practical route for oxidizing leuco diphenylmethanes 15 demands inital conversion to an imine salt 16. The imine salt is obtained by heating a mixture of diphenylmethane, sulfur, ammonium chloride, and sodium chloride at 175°C in a current of ammonia or by heating a mixture of diphenylmethane, urea, sulfamic acid, sulfur, and ammonia at 175°C (Scheme 3). Dyes 16 can be represented as the quinonoid resonance structure 17. Dyes of this class, known as auramines, are all yellow, with the only commercial representative being auramine O 16a. Due to its poor lightfastness and instability to hot acids and bases, its use has been restricted to dyeing and printing cotton, paper, silk, leather, and jute. 

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