Synthetic fibres dyeing

S.M. Burkinshaw, Chemical Principles of Synthetic Fibre Dyeing, Blackie, London, 1995. 

M.V. Kazankov, Dyes for synthetic fibres dyeing. Journal of All-Union chemical society named after D.I. Mendeleev (1974), v. 19, No 1, 64-71 (in Russian). 

There are many references in the patent literature to azo dyes prepared from 4- and 5-aminoisothiazoles, 3-, 5- and 7-amino-1,2-benzisothiazoles, and their quaternized derivatives. These are particularly useful in the dyeing of synthetic fibres. Isothiazole compounds have also been suggested for other industrial purposes, such as corrosion inhibitors, fireproofing agents, additives in rubber vulcanization, photographic chemicals and fluorescent whiteners in detergents. 

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. 

In view of the immense commercial importance of phthalocyanines as pigments, it is perhaps surprising that only a few are of importance as textile dyes. This is primarily due to the size of the molecules they are too large to allow penetration into many fibres, especially the synthetic fibres polyester and polyacrylonitrile. An example of a phthalocyanine dye which may be used to dye cellulosic substrates such as cotton and paper is C. I. Direct Blue 86 (96), a disulfonated copper phthalocyanine. In addition, a few blue reactive dyes for cotton incorporate the copper phthalocyanine system as the chromophoric unit (Chapter 8). 

The three most important types of synthetic fibres used commonly as textiles are polyester, polyamides (nylon) and acrylic fibres. Polyester and the semi-synthetic fibre cellulose acetate are dyed almost exclusively with the use of disperse dyes. Polyamide fibres may be coloured using either acid dyes, the principles of which have been discussed in the section on protein fibres, or with disperse dyes. Acrylic fibres are dyed mainly using basic (cationic) dyes. 

In the pretreatment and dyeing of synthetic fibres, the aminopolyphosphonates can assist in the removal of oligomers. 

When scouring synthetic fibres that are to be dyed with disperse dyes, nonionic scouring agents are best avoided unless they are formulated to have a high cloud point and are known not to adversely affect the dispersion properties of the dyes. Conversely, when scouring acrylic fibres, anionic surfactants should be avoided [156] because they are liable to interfere with the subsequent application of basic dyes. These fibres are usually scoured with an ethoxylated alcohol, either alone or with a mild alkali such as sodium carbonate or a phosphate. 

Many other properties have to be considered, especially for apparel fibres, e.g., moisture absorption, ability to dye, drape, texture, weaving characteristics, etc. Many of the properties are influenced by the cross-section profile of the fibre. Thus cotton and some rayons (an artificial synthetic fibre derived from cellulose) are a hollow round fibre silk has a triangular shape giving it a fine lustre and drape. 

These dyes have affinity for one or, usually, more types of hydrophobic fibre and they are normally applied by exhaustion from fine aqueous dispersion. Although pure disperse dyes have extremely low solubility in cold water, such dyes nevertheless do dissolve to a limited extent in aqueous surfactant solutions at typical dyeing temperatures. The fibre is believed to sorb dye from this dilute aqueous solution phase, which is continuously replenished by rapid dissolution of particles from suspension. Alternatively, hydrophobic fibres can absorb disperse dyes from the vapour phase. This mechanism is the basis of many continuous dyeing and printing methods of application of these dyes. The requirements and limitations of disperse dyes on cellulose acetate, triacetate, polyester, nylon and other synthetic fibres will be discussed more fully in Chapter 3. Similar products have been employed in the surface coloration of certain thermoplastics, including cellulose acetate, poly(methyl methacrylate) and polystyrene. 

The main use of fluorescent dyes is in the coloration of synthetic fibres, especially polyester, polyamide and acrylics in conjunction with elastane fibres, for fashion, leisure and especially sportswear uses. The fluorescent textiles offer not only high design options but also a large degree of safety in use, for instance increasing the visibility of cyclists and runners in busy urban areas. 

Interestingly, complexes of the type (189) were prepared by the interaction of o-aminophenols and arylazomalondialdehydes in the presence of copper(II) or nickel(II) salts. Replacement of the o-aminophenol by an acyl hydrazide resulted in the formation of complexes of the type (190), which are reported134 to be suitable for dyeing synthetic fibres. 

Nitric acid has a number of other industrial applications. It is used for pickling stainless steels, steel refining, and in the manufacture of dyes, plastics and synthetic fibres. Most of the methods used for the recovery of uranium, such as ion exchange and solvent extraction, use nitric acid. A full breakdown of the uses and applications of nitric acid is included in Ref. G6. 

A series of dyestuffs have been reported which contain the pyrido[2,3-p]-l,2,4-triazine and pyrido[4,3-e]-1,2,4-triazine nuclei. These compounds have been used to dye a number of fibres fluorescent yellow shades <74GEP(0)2417916>. Another series of polyheterocyclic dyestuffs which contain a pyridotriazine moiety have been patented as fast yellow dyes especially for synthetic fibres <75GEP(0)2355967>. Amongst a number of the compounds prepared as dyestuffs were several 1H-pyrido-l,3,4-thiadiazines. The compounds were used to dye polyester fibres fast shades of yellow <77USP4025510>. 

Adhesives Organic and inorganic bases Coolants Cleaners colorants (pigments and dyes) Fragrances Inks Paints Plasticisers (e.g., in plastics) Polymers (rubbers and plastics) Sealants Solvents Stabilisers Synthetic fibres Varnishes Biocides Detergents Fertilisers Fuels Foodstuff additives and flavourings to foodstuffs Medicinal products (for humans and animals) Plant protection products Radioactive substances... 

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