Synthetic colorants wool dyeing

Semisynthetic and synthetic fibers introduced from the 1920s made new demands on the ingenuity of dye-makers. The commercial value of new polymers relied entirely on the ease of coloration. Normal dyeing is accomplished in aqueous solution, often in the presence of a fixing agent, or mordant. This is ideal for cotton, silk and wool, but not for synthetic fibers such as nylon and polyester, that are plastic in nature. They require... 

There is a wide diversity of chemical structures of anthraquinone colorants. Many anthraquinone dyes are found in nature, perhaps the best known being alizarin, 1,2-dihydroxyanthraquinone, the principal constituent of madder (see Chapter 1). These natural anthraquinone dyes are no longer of significant commercial importance. Many of the current commercial range of synthetic anthraquinone dyes are simply substituted derivatives of the anthraquinone system. For example, a number of the most important red and blue disperse dyes for application to polyester fibres are simple non-ionic anthraquinone molecules, containing substituents such as amino, hydroxy and methoxy, and a number of sul-fonated derivatives are commonly used as acid dyes for wool. 

There is as yet no agreed international list of permitted food colours. Thus a food dye that is permitted in one country may be considered unacceptable in another. The synthetic food colorants permitted in the European Union are listed in Table 1.8 [60]. All were originally introduced as acid dyes for wool many years ago. Furthermore, more than thirty colorants of natural origin are permitted in most countries. The natural carotenoid dyes are of outstanding importance for colouring edible fats and oils. These yellow to red methine dye structures occur in many families of plants and animals, including vegetables, berries,... 

The structure of kermisic acid is l,3,4,5-tetrahydroxy-7-carboxy-8-mcrhylanthraquinone. Carminic acid (Cl Natural Red 4 Cl 75470). is a red dye occurring as a glycoside in the body of the cochineal insect Dactylopius coccus of the order Homoptera. family Coecidae, Until the advent of synthetic dyes, the principal use for carminic acid was for dyeing tin-mordanted wool or silk. Its aluminum lake, carmine, finds use in Lhe coloring of foods. The structural formula of carminic acid is (2). 

Basic dyes of the azo class were among the earliest known synthetic dyes. They were used originally for dyeing cotton mordanted with tannin and potassium antimonyl tartrate and wool from neutral solution. They continue to have minor importance for dyeing leather, paper, plastics, and waxes, and as constituents of graphic arts colors. 

A large number of naphthoquinone and benzoquinone dyes occur naturally as plant constituents, and in the past many of these have found use as colorants. The chemistry of synthetic analogues began with the discovery of naphthazarin (1) [475-38-7] by Roussin in 1861. Naphthazarin and its derivatives first found use as black chrome mordant dyes for wool and silk. In contrast to the naphthoquinones, synthetic benzoquinone dyes are few in number and are generally of the... 

A nonionic dye leveling agent designed for use with wool, synthetics, and blends to give full color value and even level dyeings. 

Ecco Leveler. [Eastern Color Chem.] Anionic dye leveling agent fm wool, synthetics, and blends. 

In certain cases, identifying the specific garment or textile product and the allergen it contains will be an important undertaking. The fiber content of the fabric will narrow the possible dyes, as certain dyes are used to color certain fibers. Cotton, rayon, and linen fabrics are dyed with direct, fiber-reactive, mordant, azoic, sulfur, and vat dyes. Wool fabrics are dyed with acid, mordant, and fiber-reactive dyes. Polyester fabrics are dyed with disperse dyes unless the polyester is modified to accept basic dyes. Nylon fabrics are colored with acid and disperse dyes unless modified to accept basic dyes. Acrylic fabrics are dyed with basic and disperse dyes. Acetate fabrics are dyed with disperse dyes. Other synthetic fibers are dyed with disperse dyes. 

The process was discovered and patented in 1856 by William Henry Perkin, at a time when the wool and cotton industries were enjoying a trade boom and the demand for colorants threatened to outstrip the supplies of natural dyes, mostly vegetable, then available. Crude benzol from the well-established coal-gas and coal-tar distillation industries was commercially available, as were mineral acids, alkalis, bichromates, saltpetre and other materials. Mauveine followed by other synthetic dyes from Perkin Sons, soon became a success. Other, rival pioneers built factories in the UK and Europe and introduced new dyes, the result of their own research work. 

Another very interesting and less explored field is the color changes observed when anthocyanins are in contact with colorless substances, which are not necessarily copigments, for instance, surfactants, emulsions, gels, proteins, DNA, cotton, wool, hair and so on (Bicard, 1999). For hair coloring, anthocyanins could be alternatives to existing synthetic systems and generate new direct dyes for hair (cationic dyes). 

Howard L. Needles is presently Professor of Textiles and Materials Science at the University of Cal ifomia, Davis. After receiving his doctorate in organic chemistry from the University of Missouri in 1963, he began his career conducting research on wool and related model systems. His research was then extended to include synthetic fibers and the effect of chemical modification on the dyeing and color properties of these fibers. He has also continued his studies at North Carolina State University and at the University of Leeds, England, and is also Program Chairman of the Cellulose, Paper and Textile Division of the American Chemical Society. 

Basic dyes were the first dye class made synthetically mauve was a basic bye. The basic dyes first were used to dye silk and wool, but they had poor fastness properties. Today basic dyes dyed on acrylics or cationic dyeable polyester have high tinctorial value they are the brightest dyes available and have unlimited color range and good fastness properties. 

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