Dyeing procedure

Dyeing procedures vary according to the fiber content of the textile material and the equipment to be used. Examples of basic carrier dyeing procedures are as follows. 

Mordant dyes have hydroxy groups in their molecular stmcture that are capable of forming complexes with metals. Although a variety of metals such as iron, copper, aluminum, and cobalt have been used, chromium is most preferable as a mordant. Alizarin or Cl Mordant Red 11 [72 8-0] (1) (Cl 58000), the principal component of the natural dye obtained from madder root, is the most typical mordant dye (see Dyes, natural). The aluminum mordant of alizarin is a well-known dye by the name of Turkey Red and was used to dye cotton and wool with excellent fastness. However, as is the case with many other mordant dyes, it gave way to the vat or the azoic dyes, which are applied by much simpler dyeing procedures. 

Acid—mordant dyes have characteristics similar to those of acid dyes which have a relatively low molecular weight, anionic substituents, and an affinity to polyamide fibers and mordant dyes. In general, brilliant shades caimot be obtained by acid—mordant dyes because they are used as their chromium mordant by treatment with dichromate in the course of the dyeing procedure. However, because of their excellent fastness for light and wet treatment, they are predominandy used to dye wool in heavy shades (navy blue, brown, and black). In terms of chemical constitution, most of the acid—mordant dyes are azo dyes some are triphenyhnethane dyes and very few anthraquinone dyes are used in this area. Cl Mordant Black 13 [1324-21 -6] (183) (Cl 63615) is one of the few examples of currentiy produced anthraquinone acid—mordant dyes. It is prepared by condensation of purpurin with aniline in the presence of boric acid, followed by sulfonation and finally by conversion to the sodium salt (146,147). 

Very small quantities of acetate staple are dyed, however, large quantities of acetate filament are found in satin, taffeta, and tricot fabrics these are usually dyed open-width on a jig owing to thek inclination to crease or crack easily. A typical dyeing procedure on the jig involves addition of acetic acid and dispersing agent over two ends at 50°C. The disperse dye is added over two ends and the dyebath temperature is gradually raised to 80°C in 5°C increments with two passes at each temperature. The dyeing is completed after 30—60 min at 80°C. 

In the manufacture of colored papers, it is best to add the dyestuffs before addition of rosin size and alum. This is not always possible in continuous dyeing procedures where dyestuffs must be added to stock containing size and/or alum, and this may cause premature laking of the dyestuffs and subsequent loss of tinctorial strength and/or dullness of shade. The proper selection of dyestuffs can help to reduce these disadvantages. 

Redox behavior of anthraquinone is shown in Scheme 4. The quinone moiety may be reduced to the hydroquinone form and converted to a leuco salt under alkali conditions. In general, the leuco salt has a strong affinity for cellulose and is soluble in water. The hydroquinone form is insoluble in water and has low affinity to cellulose. The preferred dyeing procedure depends on the structure and properties of the vat dye. The variables that are used to control the process include, e.g., strength and amount of alkali, reduction temperature, and the presence of salts. During the process of reduction, some side reactions, such as overreduction, hydrolysis,... 

With the duplicate parathion-treated samples and one untreated sample, the benzene extracts were processed in the usual manner and subjected to the dyeing procedure. Their transmission-wave-length curves are shown in Figure 2 with a companion curve for dyed parathion. 

Denizot F, Lang R 1986 Rapid colorimetric assay for cell growth and survival. Modifications to the tetrazolium dye procedure giving improved sensitivity and reliability. J Immunol... 

Assay for the level of biotin incorporation using the HABA dye procedure (Chapter 23, Section 7). 

See also Disazo mordant dyes anthraquinone, 9 337 dyeing procedures, 9 399 metal complexes of, 9 394-399 soluble, 7 373t Mordenites... 

This problem has been confirmed recently in a study of the mechanism of covalent reaction between nylon 6.6 and the sulpha toe thylsulphone dye Cl Reactive Blue 19 (7.37). Acid hydrolysis of the dyed fibre and HPLC analysis of the hydrolysate yielded the 6-aminohexylaminoethylsulphonyl derivative of Blue 19. Even when the dyeing procedure was optimised to achieve maximal exhaustion and fixation to the fibre [128], only about 30% of the N-terminal amino groups in the nylon 6.6 were accessible because of mutual blocking effects between these bulky anionic dye molecules. 

The applied products are fixed on the textile by drying/curing, but similar to the pad batch dyeing procedures, the last filling of the padding unit needs additional attention. A release of such concentrated finishing baths can introduce a COD of up to 200,000 mg02/L of liquor [70]. 

With respect to fiber components that are dyed with completely different dye classes, the ability to use single-bath techniques (exhaust and continuous) depends on the interaction between the dyes and the compatibility of their dyeing procedures. 

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. 

Synthetic dyes may be isolated, purified, or concentrated from foods or from extracts by wool-dyeing procedures column chromatography with polyamide ion-pair or solvent extraction reverse-phase cartridges or ion-exchange resins (157,159,168). These techniques are discussed next. 

Naturally the dyeing procedure varies with the type of colour (basic, acid, mordant, substantive). In order, however, that valid conclusions may be drawn, the procedure should be that used industrially, this being usually indicated in the instructions supplied with the colouring matter. 

The dyeing procedure for paper can be described basically by two processes the penetration of the dye molecule into the capillary spaces of the cellulose and then its adsorption on the surface of the fiber. The bonding forces are due to the effects charge (ionic bonds), precipitation, and intermolecular forces. 

A second condition for a correct dyeing procedure is perfect rinsing of the dye out of the paper without loss of dye fixed to the protein. If rinsing is incomplete, a blank of the paper must be taken into account and this may be too high for accurate evaluation of small fractions here again standardized working conditions are essential. 

It is difficult to achieve a dyeing procedure perfect in all these respects, and even if this were realized, the problem of colorimetry itself would remain. Either after elution or on the paper itself, the dye must be evaluated. On paper, the so-called paper error is a very important factor although translucency agents or refleetometry are used to reduce this error to a minimum. 

Savings and Cost/Benefit Analysis. The bench scale experiments were successful Tn overcoming major technical problems while demonstrating that dyebath/auxiliary bath reuse is indeed feasible with reactive dyes on cotton-containing fabrics. In addition, a shortened-cycle dyeing procedure coupled with reuse for cotton/polyester blends was shown to further increase energy, mass, and time savings (Table XXX). 

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