Reactive dyes cold dyeing

Cold Exhaust Dyeings Fiber-Reactive Dyes. Start at 25—30°C optionally with a sequestrant and maintain. The dye is added over 5 min, then there is portionwise addition of salt every 10—15 min, increasing the size of the addition each time over 1 h. The amount of salt used (10—100 g/L) depends on the depth of shade. After the final addition of salt, wait 15 min, portionwise add soda ash (10—20 g/L) over 15 min, and continue dyeing for 30—45 min. Drop dyebath, cold water rinse, and use a sequence of hot washes to remove all loose "unfixed" dye. 

Other New Methods. Because the values obtained are dependent on the conditions of measurement, standard test procedures are under review by ISO for determination of cold-water solubiUty of water-soluble dyes (38) determination of the solubiUty and solution stabiUty of water-soluble dyes (39) and determination of the electrolyte stabiUty of reactive dyes (40). 

Fig. 3. Reactivity of various reactive dye groups. Hot dyeiag is done at 80°C, cold dyeing at 40°C.

Practically all the commercially important reactive dyes based on activated double bonds employ the vinyl sulfone reactive group (2.35), usually as the sulfatoethylsul-fone derivative (2.34), which converts into (2.35) in the dyebath under the influence of alkali at pH 11 to 12.5. They are usually applied onto the fibre by exhaustion from the dyebath at around 40-60 °C or by cold padding at 30 °C. The vinylsulfone group is most commonly attached to the dye chromophore via an aromatic ring, e.g. Cl Reactive Black 5 (2.2), but in a few cases a bridging aliphatic group is employed. ... 

Application Methods. There are many detailed application methods used for applying reactive dyes, and all have been described in detail. Examples of the main methods include cold exhaust dyeing fiber-reactive dyes, warm, hot exhaust dyeing dyes, migration exhaust technique for less than 0.5% depth of shade, all-in method, continuous dyeing, and cold pad-batch dyeing. 

Instead of a continuous procedure the dye can be fixed on the fiber after application by batching on a roll at a controlled temperature. For reactive dyes a cold batch process is widely used. 

POMOFIX G48 is a resinous aftertreating agent used to improve the wet fastness of direct, develop, and fiber reactive dyes on cotton and rayon. In addition to improving the washfastness, POMOFIX G48 also improves the fastness to cold water bleeding, perspiration, migration, and wet Ironing. 

When it is necessary to shade with reactive dyes of high substantivity it is desirable to run half of the liquor off and refill with cold water and then add the shading colour. When the additions are large the temperature should be raised again. 

The reactive dyes give colours of exceptionally good wet-fastness on natural silk and their application is comparatively simple. When using the cold method with dichlorotriazinyl colours the dyebath is made up with the dissolved dye and 10 lb of common salt or anhydrous Glauber s salt... 

Extremely good fastness on the cellulosic component can be obtained with reactive dyes. The cold dyeing members are preferable because the conditions of alkalinity and temperature necessary to fix the high-tempera-ture reactive dyestufiFs would be harmful to the wool. When Procion dyes are applied cold the protein fibre is left practically unstained, unless it has been chlorinated previously, and must be brought up to shade with neutral dyeing acid dyes such as those on page 575. The Procion dyes which have been found suitable are ... 

Khatri, Z., Memon, M.H., Khatri, A., Tanwari, A., 2011. Cold Pad-Batch dyeing method for cotton fabric dyeing with reactive dyes using ultrasonic energy. Ultrason. Sonochem. 18, 1301-1307. 

Khatri, Z., Ahmed, R, Jhatial, A., Abro, M., Mayakrishnan, G., Kim, I.-S., 2014. Cold pad-batch dyeing of cellulose nanofibers with reactive dyes. Cellulose 21, 3089-3095. 

In reactive dyeing, where ever possible you m try cold dyeing to save energy. Preconditioning method is one such procedure. 

The reactive dyes being anionic (negatively charged) in solution get attracted to the positive charges on the fibre which eliminates the salt requirements for satisfactory dye exhaustion. Trials were conducted for cold brand, hot brand and highly exhaustive reactive dyes. 

Features Reduces rate of dye strike as temp, rises in the dyeing process low foaming does not affect dyeablllty of direct or reactive dyes Properties Brn. limpid vise. Iiq. dissolves in cold water pH 7.5 UseLevei 0.5g/l... 

Warm- and cold-dyeing double-anchor dyes are prepared by incorporating halo-triazinyl and vinylsulfonyl reactive anchors. The bond between the triazine ring and a fiber is stable under basic conditions, whereas that to the vinylsulfonyl group is stable to acid. A combination of the two anchor systems therefore produces a dye with... 

In the exhaustion dyeing process, highly or moderately substantive dyes are usually employed. The optimum dyeing conditions depend on the reactivity of the dyes. Cold dyers are dyed at 30-50°C and a pH of 10-11 hot dyers at 70-90°C and a pH of 11-12. For pH control normally mixtures of sodium carbonate and sodium hydroxide are used. To enhance substantivity of the dye sodium sulfate or sodium chloride is added. For less than 0.5 % dye based on textile weight, salt concentrations of 10-30 g/L are recommended. For deep shades (more than 4%), ca. 50 g/L is used with vinylsulfone dyes having low substantivity, up to 80 g/L. 

BURCOFIX FR-30 is used to increase the wetfastness of direct, develop, reactive and acid dyestuffs on cotton, rayon, wool, and their blends. It also decidedly improves the fastness to cold water bleeding, sea water, perspiration, and prevents migration of the above mentioned dyes during drying. 

The instability of the solutions of the cold-dyeing Procion colours was a serious disadvantage in their application to textile printing. The stock solution for printing must be kept and used for several hours. The mono-chlorotriazinyl dyes of the general structure of formula (7) are less reactive. 

Polyamide fibres can be dyed with both cold- and hot-dyeing reactive colours in a liquor containing 4 per cent of the weight of the goods of acetic acid 80 per cent. The load is entered at 40°C (104°F) and the temperature brought up to 95°C (203°F), after which dyeing is continued for 1 hour, or more, if necessary. The reaetive dyes are satisfactory on staple yarns where differences in the affinity of the polyamide fibre are randomized. In continuous filaments any irregularities in the yarn are not covered. 

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