Dyeing textile fibers natural

Phthalocyanine Dyes. In addition to their use as pigments, the phthalocyanines have found widespread appHcation as dyestuffs, eg, direct and reactive dyes, water-soluble dyes with physical or chemical binding, solvent-soluble dyes with physical or chemical binding, a2o reactive dyes, a2o nonreactive dyes, sulfur dyes, and wet dyes. The first phthalocyanine dyes were used in the early 1930s to dye textiles like cotton (qv). The water-soluble forms Hke sodium salts of copper phthalocyanine disulfonic acid. Direct Blue 86 [1330-38-7] (Cl 74180), Direct Blue 87 [1330-39-8] (Cl 74200), Acid Blue 249 [36485-85-5] (Cl 74220), and their derivatives are used to dye natural and synthetic textiles (qv), paper, and leather (qv). The sodium salt of cobalt phthalocyanine, ie. Vat Blue 29 [1328-50-3] (Cl 74140) is mostly appHed to ceUulose fibers (qv). 

Mordant Dyes. This group includes many natural as well as synthetic dyes. They have no or low substantivity for textile fibers and are therefore appHed to ceUulosic or protein fibers that have been treated (mordanted) with metallic oxides to give points of attraction for the dye. The dye... 

The most economically important materials with respect to ozone damage are paint, elastomers (rubbers), and textile fiber-dye systems. Damage to polyethylene by ozone is considered to be negligible. The 1970 ozone damage to materials has been estimated as follows paint, 540 million elastomers, 569 million and textile fibers and dyes, 84 million—for a total of over 1 billion. Thus, the total combined material and crop damage falls between 1.5 and 2 billion per year. Estimates of damage to natural ecosystems are not available. 

Because of its pronounced interfacial activity, HOSTAPUR CX Hi. Conc. can be employed very successfully in the dyeing and finishing of textiles of natural and regenerated cellulose, wool, or synthetic fibers. 

The world textile industry is one of the largest consumers of dyestuffs. An understanding of the chemistry of textile fibers is necessary to select an appropriate dye from each of the several dye classes so that the textile product requirements for proper shade, fastness, and economics are achieved. The properties of some of the more commercially important natural and synthetic fibers are briefly discussed in this section. The natural fibers may be from plant sources (such as cotton and flax), animal sources (such as wool and silk), or chemically modified natural materials (such as rayon and acetate fibers). The synthetic fibers include nylon, polyester, acrylics, polyolefins, and spindex. The various types of fiber along with the type of dye needed are summarized in Table 8.2. 

The nature of substrate selects the type of dye needed, and methods of dye application. The development of new substrates led to new dyes and dyeing methods and influenced the dyeing technology in a fundamental manner. The dyeing of any substance (e.g., textile fiber) is based on a physico-chemical equilibrium process, namely diffusion and sorption of dye molecules or ions. These processes may be followed by chemical reactions in the substrate, for example, in the application of vat, reactive, azoic, and chrome dyes [9]. 

Camille and Henry Dreyfus developed the first commercial process to manufacture cellulose acetate in 1905 and commercialized the spinning of cellulose acetate fibers in 1924 in the United States. At that time, the only other human-made fiber was viscose rayon, which was still in its early stages of commercialization. The main textile fibers were natural fibers cotton, wool, silk, and flax. Cellulose triacetate textile fiber was commercialized later in the 1950s. The tremendous technical effort by the Dreyfus Brothers resulted in more than 300 patents describing such significant inventions as the dry-spinning process and disperse dyeing. 

Polyolefin textile fibers are usually produced through the melt spinning process with good mechanical properties and chemical and abrasion resistance. One of the main drawbacks in this industry is the fact that they are difficult to dye unless additives are used. One of the major applications of PP is the use in carpet which replaced natural fibers. Other apphcations include bags, sportswear, and knitwear. 

The popularity and widespread use of azo dyes is due to several factors [1]. As a group, th are colour-fast and encompass the entire visible spectrum, and many are easily S3mthesized from inexpensive and easily obtained starting materials. Azo dyes are also typically amenable to structural modification, and representative azo dyes can be made to bind most synthetic and natural textile fibers. 

Polyvinylpyrrolidone is thus utilized as either aqueous or organic solutions in a multitude of applications. Many of these applications are also related to the chelating properties of this polymer. Thus, it forms complexes with molecular iodine (I2) and can thus be used as a reservoir of this molecule whose disinfecting properties are well known. It also gives strong interactions with natural and synthetic dyes and thus facilitates their anchoring on textile fibers by complexation with the corresponding polymers. 

The applications of chitosan for improving dyeability of cotton fabric has been widely studied [73, 177, 48], In the textile area, the higher the active site of chitosan favors the higher the dye adsorption (including natural dye) as well as film formation on fiber surface [92]. Chitosan can easily adsorb anionic dyes, such as direct, acid and reactive dyes, by electrostatic attraction due to its cationic nature in an acidic condition. It is postulated that the affinity of chitosan to cotton would be by Van der Waals forces between them because of the similar structures of chitosan and cotton. 

Textile dyes were, until the nineteenth century invention of aniline dyes, derived from biological sources plants or animals, eg, insects or, as in the case of the highly prized classical dyestuff Tyrian purple, a shellfish. Some of these natural dyes are so-caUed vat dyes, eg, indigo and Tyrian purple, in which a chemical modification after binding to the fiber results in the intended color. Some others are direct dyes, eg, walnut sheU and safflower, that can be apphed directly to the fiber. The majority, however, are mordant dyes a metal salt precipitated onto the fiber facUitates the binding of the dyestuff Aluminum, iron, and tin salts ate the most common historical mordants. The color of the dyed textile depends on the mordant used for example, cochineal is crimson when mordanted with aluminum, purple with iron, and scarlet with tin (see Dyes AND DYE INTERMEDIATES). 

Deterioration. The causes of degradation phenomena in textiles (155—158, 164) are many and include pollution, bleaches, acids, alkaUes, and, of course, wear. The single most important effect, however, is that of photodegradation. Both ceUulosic and proteinaceous fibers are highly photosensitive. The natural sensitivity of the fibers are enhanced by impurities, remainders of finishing processes, and mordants for dyes. Depolymerization and oxidation lead to decreased fiber strength and to embrittlement. 

Textile finishing includes various efforts to improve the properties of textile fabrics, whether for apparel, home, or other end uses. In particular, these processes are directed toward modifying either the fiber characteristics themselves or the gross textile end properties. Such modifications may be chemical or mechanical in nature. One modification that is not covered in this article relates to the dyeing of textiles and the dyestuffs employed for fibers however, areas that involve chemical finishing designed to modify the normal dye receptivity and the growing use of enzyme treatments are included. 

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