Disperse Polyester-Cellulose Blends

Disperse liquid brands of sulphur, vat or disperse dyes, including mixed formulations of disperse and vat dyes in matching hues for the dyeing of polyester/cellulosic blends, have been commercially available for many years. The proportion of reactive dyes marketed as aqueous solutions is expected to increase markedly [10] because of ... 

Considerable research effort has been devoted to developing a new generation of disperse dyes designed to optimise fastness to washing and minimise cross-staining of the cellulosic component of polyester/cellulosic blends [97,98]. Diester-containing monoazo disperse dye structures (4.91) that yield a dicarboxylic acid on hydrolysis and certain thienylazo blues... 

Dye Combinations. In certain cases it is desirable to print fiber blends with combinations of the appropriate dye classes, rather than with pigments. Only polyester-cellulose blends are of commercial importance and the following dye systems have been developed for them. The dyes of the different classes are contained in the same print paste and, therefore, are applied simultaneously in one print operation. They include disperse-reactive combinations, disperse-pigment combinations, and disperse-vat combinations. 

Uses Leveling agent, dispersant for dyeing polyester fibers with disperse dyestuffs, fluorescent whitening of polyester fibers with disperse FWAs and dyeing the polyester component of polyester/cellulosic blends by the HT process Features Prevents filtration of dyestuffs does not inc. the AOX content of waste-water pumpable resist, to acids, alkali, salts, hard water Properties YIsh.-brn. Iiq. readily sol. in water dens. 1.0 g/ml (20 C) pH 4,0 (10%)... 

If a padding process is used to brighten a polyester/cotton blend, both the disperse and anionic brighteners may be applied from the same pad bath, even when a resin finish is applied simultaneously to the cellulosic component of the blend. Similarly, both types of... 

Vat dyes are used to colour both components in pale depths on polyester/cellulosic fibre blends [44] but coloration of the polyester component in this case is more closely analogous to disperse dyeing (section 1.6.5). Anthraquinone disperse dyes resemble those vat dyes that are substituted anthraquinone derivatives and in both instances it is exclusively the virtually water-insoluble keto form that is absorbed by the polyester fibre. 

The sulfur dyes are widely used in piece dyeing of traditionally woven cotton goods such as drill and corduroy fabrics (see Textiles). The cellulosic portion of polyester—cotton and polyester—viscose blends is dyed with sulfur dyes. Their fastness matches that of the disperse dyes on the polyester portion, especially when it is taken into account that these fabrics are generally given a resin finish. 

Disperse dyes are relatively small molecules, with very low water solubility, which possess a high affinity for hydrophobic fibres such as cellulose acetate, polyester or blends thereof. The dyes are applied by transfer printing or high temperature steam fixation. Azo and anthraquinone dyes constitute the major portion of disperse dyes. 

Blends of polyester with cotton (qv) or viscose are first dyed with disperse dyes, then with sulfur dyes (see Fibers, polyester Fibers, regenerated CELLULOSics). Disperse and sulfur dyes can also be appHed simultaneously in a pad—dry—thermofix/chemical reduction pad—steam sequence. In this case, the sulfur dyes cannot be used in thein reduced form because of the effect of the sodium sulfide on the disperse dye. Therefore, this method is confined to the solubilized sulfur dyes or sulfur dyes in the dispersed form. 

The phosphonic acid reactive dyes were appHed to cellulose under slightly acid pH rather than alkaline pH required for other ceUulosic reactive dyes. This feature made them especially attractive for one bath appHcation with disperse dyes to cotton/polyester blends. A review of these dyes appears ia Refereace 5. 

Blends of polyesterand cellulosic fibers are printed with disperse and reactive dyes only in cases, when pigment printing is unsatisfactory. Dye selection follows basically the rules given for continuous dyeing polyester and cellulose fibers. 

The surface energy of fibres is closely related to the hydrophility of the fibre. Some investigations are concerned with methods to decrease hydrophility. The modification of wood-cellulose fibres with stearic acid [49] causes those fibres to become hydrophobic and improves their dispersion in PR As can be observed in jute reinforced unsaturated polyester resin composites, treatment with polyvinylacetate increases the mechanical properties [50] and moisture repellence. Silane coupling agents may contribute hydrophilic properties to the interface, especially when amino-functional silanes, such as epoxies and urethane silane are used as primers for reactive polymers. The primer may supply much more amine functionality than can possibly react with the resin at the interphase. Those amines, which could not react, are hydrophilic and therefore responsible for the poor water resistance of the bonds. An effective way to use hydrophilic silanes is to blend them with hydrophobic silanes such as phenyltrimethoxysilane. Mixed siloxane primers also have an improved thermal stability, which is typical for aromatic silicones [48]. 

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