Chakraborty, in Handbook of Textile and Industrial Dyeing, 2011. However, the reduction or dyeing process has to be the same as the vat dyeing process. This last step is considered a very important step in vat dyeing. Excessive quantity of reducing agent and alkali decrease the exhaustion rate of the dyeing. Dye manufacturers are now putting more effort into reducing the amount of metals present as impurities.

one essentially disperse dye and another from vat, reactive etc.

Vatting is carried out in strong alkali condition.

Range of shade is limited to blue, orange, purple, pink, yellow, green, and golden – all in light shades. The dyes are applied to the textile materials in this form and after the completion of dyeing, the soluble form of the dye is oxidised back to the parent insoluble form.

Urea should be substituted as a dye-solution assistant as much as possible. 3. one-bath two-step or two-bath two-step methods are popular. Many studies have been carried out on the application of enzymes on natural fibres, including cotton surface modification to enhance the handle and appearance (Ibrahim et al., 2005), removal of undesirable by-products from unscoured cotton (Thiagarajan and Selvakumar, 2008), desizing through enzymatic hydrolysis on starch (Hanson and Gilbert, 1974), enzymatic treatment of bleaching effluent (Auterinen and Anna-Liisa, 2006), softening woody fibres during retting (Dutta et al., 2000), softening (Dhurai and Natrajan, 2007), improving dyeability and pilling behaviour of wool (Heine and Hocker, 1995), silk degumming (Chopra and Gulrajani, 1994), printing (Abd E1 et al., 2008) and finishing (Lenin et al., 2009), specifically in softening of wool (Ascensión and Remedios, 2006), etc.

some addition of salt is needed during dyeing to aid exhaustion; IK dyes (I = Indanthren, K = cold) have low affinity, only need a low concentration of NaOH with. for slasher continuous dyeing with indigo and other dyes of denim fabric warps. The structure of indigo was first proposed by von Baeyer. This technology consists of special pad troughs with an optimised shape and efficient double flow bath circulation. After the completion of dyeing, the dyes are oxidised back to the original insoluble form. Decomposition of hydros occours rapidly in acidic solution .so during dyeing material should not be over exposed to air.

There are basic  4 steps for vat dyeing. Selective vat dyes can be applied on polyester through thermosol treatment and light to medium shades can be produced with single class of dye. S.R. In a polar solvent it is blue while in a non-polar solvent it is violet. The presence of the metal in the metallised dyes can be regarded as a less relevant problem compared to the presence of free metal impurities, provided that high exhaustion and fixation levels are achieved and that measures are taken to minimise losses from handling, weighing, drum cleaning, etc. Hydrolytic reactions are not important because if the dye survives the rigours of biological treatment processes, it is unlikely to degrade rapidly in the environment. Vat dye is one of the oldest types of dye. 13. • To get uniform level dyeing results, the concentration of sodium hydrosulfite and caustic soda must be in exact quantity to reduce the dye bath during the whole process. During finishing at high temperature, a part of the dye is sublimised-off, is condensed on polyester phase and diffused inside, lowering the final shade depth. Some important treatment is required for improving solubility in water. Soumyadeep Saha holds a Master's Degree in Fashion Technology from NIFT, New Delhi. In view of the environmental concern about possible harm from the use of aldehyde (formaldehyde or acetaldehyde-forming sulphoxylate), stabilisers and toxic metallic salts (Ni cyanides) or borohydrides for release of the reducing agent, such systems, if used, should be replaced by either mechanical methods or high molecular weight polymeric auxiliaries. Vat dye are insoluble in  water  but  with  the  help  of  vatting process vat dye is easily  soluble  in  water. Furnishing requiring high fastness to light. These are applied to the fiber in a weakly acid or neutral pH. Vatting is done in alkaline condition. Enzymes have been found to be effective in dyeing of textiles too.

Reserve shade: Polyester is dyed with disperse dye and cellulosic part is left undyed or vice versa. Now you have to know that alkali carried forward by the substrate does not allow oxidizing agents to release free oxygen, so shades produced in this way will lack desired fastness. The BOD load of auxiliary chemicals added to the dye bath varies between moderate and high. However, little information is available on this. Subsequent soaping is carried out in open width washing machines. Exhaust dyeing creates more trouble as commencing of the succeeding step requires a vacant trough within shortest possible time. These dyes boast excellent fastness properties. One component of these is hydrophobic (D-part) and non-polar fibre while the other is hydrophilic and polar (A-part). Dyeing is carried out at lower temperature. 5. uniforms. This converted, water soluble pigment is called leuco from & they have substantivity for cotton. This is a machine based on the indigo flow technology. Your email address will not be published.

That is because the rest of the process is more or less identical for all vat dyes. The enzymes mainly applied in textile processing are amylases, cellulases, proteases, esterases, nitrilases, catalases, peroxidases, laccases, lipases and pectinases. Vat / Vessel. Vat dyes are substantive towards the fibre only when they are converted to soluble leuco compounds, which are obtained as a result of treatment with sodium hydrosulphite (reducing agent) in presence of caustic soda solution. 6. For slasher continuous dyeing, Master S.r.l.


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