Dyes for Fiber Blends

Apart from cellulose, direct dyes have a strong affinity to wool and polyamide fibers. Blends of cellulose with wool ( half wool ) used to occupy a considerable segment of the market, but are today without any significance. However polyamide (PA) fibers are included in articles made of cellulose fibers to improve dimensional stability, ease of care, and durability, e.g., in sportswear and knitwear, corduroy fabrics, or plush articles, in which a PA pile is often anchored to a cellulose fabric base. Different dyeing methods are described in [50 pp. 433-4371, [6, p. 570], 

For direct dyes in blends of cellulose with acrylicflbers see Section 4.14.8. 

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When dyeing fiber blends it must be decided whether the fibers can be dyed simultaneously from the same dyebath, or separately and in what order from different dyebaths. The benefits of dyeing from separate dyebaths is that the conditions can be chosen to give the maximum dyeing efficiency for each dye—fiber combination. The disadvantage is that it is more time consuming. 

Gellulosic—Acrylic Fibers. Commonly this blend is used ia koitgoods, wovea fabrics for slacks, drapery, and upholstery fabrics. Siace anionic direct dyes are used for the ceUulosic fiber and cationic dyes for the acryHcs, a one-bath dyeiag process is only suitable for light to medium shades. Auxiliaries are needed to prevent precipitation of any dye complexes. 

Wool—Acrylic Fibers. This blend is being used for iadustrial and hand knitting yams. The acryHc fiber is aesthetically similar to wool, iacreases the strength of the yam, and adds bulk to the goods. Special precautions are necessary siace the two fibers are colored with dyes of opposite ionic type. Coprecipitation is prevented with the use of an antiprecipitant. Usually, level dyeing acid dyes are used for the wool portion in combination with the cationic dyes for acryHc fiber. 

Wool—Polyester Fibers. The 45/55 wool—polyester blend is the most common fiber combination in the worsted industry. Strength and exceUent dimensional stabiHty of the polyester fiber enable the creation of lightweight wear fabrics not obtainable before. Economy has modified the fiber ratio and 30/70 and 20/80 wool—polyester blends are as common as the classical 45/55 blend. Disperse dyes for polyester and acid or neutral premetaUized dyes for wool are employed in a one-bath process. Should cationic dyes be used for the wool portion, a one-bath procedure can only be employed for light to medium shades, whereas dark shades require a one-bath two-step process. Wool blends should not be dyed above 105°C in order to avoid deterioration of the fiber quaHty. 

Polyester Fiber Blends. Disperse dyeable and cationic dyeable polyester fibers are frequentiy combiaed ia apparel fabrics for styling purposes. Whereas the disperse dyes dye both fibers, but ia differeat depths, selected cationic dyes reserve the disperse dyeable fiber completely, resulting ia color/white effects. 

Polyester Fibei Acrylic Fiber Blends. This fiber blend is dyed ia a similar fashion to that of the blends of the different polyester fibers. The selection of cationic dyes is substantially larger for the acryhc blend. 

Dye Combinations. In certain cases it is desirable to print fiber blends with combiaations of the appropriate dye classes, rather than with pigments. Only polyester—ceUulose blends are of commercial importance and the foUowing dye systems have been developed for them. The dyes of the different classes are contained in the same print paste and, therefore, are appUed simultaneously in one print operation. 

The manufacturing processes for textile filament, staple and industrial filament yams have become so specialized that it is not possible to make one such class of fibers on the others equipment. Within these classes, there are production machines specialized for certain types of fibers for specific types of consumer products. Large machines designed to produce high volumes of commodity products (e.g. staple for cotton blending) at high efficiency and low cost are not well suited to the efficient production of specialty staple variants (e.g. fibers with special dyeing properties) and vice-versa. 

Cotton-acrylic fiber blends are also used for high quality upholstery pile fabrics. Besides the one-bath exhaust dyeing procedure involving a very high ratio of liquor to bath, a continuous pad-steam process is used to dye these fabrics. 

Wool-Polyester Fibers. The wool-polyester blend is the most common liber combination in the worsted industry Disperse dyes for polyester and acid or neutral premetallized dyes for wool are employed in a one-hulh process. 

For leuco esters of vat dyes on CEL-PES fiber blends, see Section 4.12.4. 

After the dyes are fixed, dyes and auxiliaries that adhere superficially must be washed out, if necessary, by an alkaline reductive treatment. In the case of PES-CEL fiber blends, this washing can be combined conveniendy with afterdyeing of the cellulose component, e.g., simply by overdyeing with vat dyes (see Section 4.4.3). For details of the thermosol process, see [85, pp. 122-131],... 

Since disperse dyes diffuse very slowly into PES fibers, efforts have been made to increase the rate of dye strike by chemical or physical alteration of the fiber. The fiber is also modified to reduce the pilling tendency, to increase shrinkage and elasticity, and to reduce flammability. Such modified fibers exhibit improved dye receptivity. Fibers with improved dyeability can be dyed with disperse dyes at boiling temperature without a carrier or with basic dyes when they are modified with acidic components (5-sulfoisophthalic acid). Fibers of this type are used if dyeing cannot be carried out easily above 100°C (e.g., in the case of floor coverings, articles made of PES-wool blends, stretch materials, and cord). Strongly crimped PES bicomponent fibers are produced for special purposes. These fibers are normally also dyeable at the boil and without a carrier [136, 137, 138],... 

In a two-bath, two-step dyeing process, other dyes suited to dye CEL fibers may also be used for PES-CEL blends. For instance, in spite of its tediousness, Naphtol AS dyeing is still employed (see Section 4.8), especially for wetfast red shades, and the Phthalogen process is used for turquoise (see Section 4.9.5). Pigment dyeing is also applied to PES-CEL blends. 

BORCODYE D-6-LF is multifunctional, eliminating the need for additional leveling agents when dyeing fiber blends. It as also an effective leveling agent for direct dyes on cellulosics. 

Is a strongly hydrophilic emulsifier, dispersant, solubilizer and detergent. It is used as a stabilizer and anticoagulant for natural and synthetic latices and dye pastes, as a dyeing assistant for wool/acrylic blends, and as a detergent and lubricant for fiber/fabric scouring. TRYCOL 5972 is also used as an emulsifier for waxes used in coating citrus fruits. HLB 15.8... 

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