George Weil helpfully says that pre-reduced indigo is used as “an alternative to Natural Indigo”. Note that there are several entirely different ways to reduce the vat dye, including using thiourea dioxide, sodium bisulfite, or sodium hydrosulfite (which is an old name for sodium dithionite). (source) In corroboration of this interpretation, they have a page on Lanaset dyes with this same webpage title, so it’s just a mistake. All the vat dyes examined did not satisfy the condition, although Pyr-Yellow may have some effects. This is of great interest, since, once attached, they are very difficult to remove. Interestingly, there IS no skeletal formula for the indigo dye-cellulose bond, because there is no bond. Name: Marc This is somewhat similar to the process that occurs during chromatography- the molecules with the strongest affinity for the substrate move the least distance from the point of origin whereas molecules with less affinity move much further. They normally undergo electrophilic addition reactions. Royce Product Name. Vat dyes with high photoreductivity showed the same colour change on dry cellulose by long exposure, implying that photo-oxidation occurs in the superficial part of fibre substrate and photo-reduction in the inner part. It should also be noted that the classification refers to the primary mechanism of staining. Here’s a piece I wrote a decade ago about the comparative safety of different types of indigo dye vats: “Safety of auxiliary chemicals for indigo”. The major fibre-reactive group which reacts this way contains six-membered, heterocyclic, aromatic rings, with halogen substituents. The vat dyes are naturally coloring matter and kept in wooden vat and make solubilise vat dyes by the process of formantation – so it is called vat dyes. Another useful property of Vat dyes is that most of them are less susceptible to fading than other types of dye. "Vat dyes" are a special class of dyes that work with a special chemistry. A specialized category of Vat dyes is light-sensitive pre-reduced Vat dye, which can be used to make single-color photographic prints on fabric. Their main use is the dyeing of polyesters, and they find minor use dyeing cellulose acetates and polyamides. Acid-milling dyes are larger than acid-leveling dyes, and show a much stronger affinity for wool fibres. If so, i would like to inquire about the pricing under the specifications mentioned above as i intend to use the VAT dyes on a small scale. If you find any additional information, I will be interested in learning about it! As a result, those vat dyes perform the highest lightfastness. It is important to avoid stirring the bath enough to introduce a large amount of air into the water. Procion dyes could also be applied in batches, or continuously. Color Index. A specialized category of Vat dyes is light-sensitive pre-reduced Vat dye, which can be used to make single-color photographic prints on fabric. These are termed natural dyes. It gives no information about the mechanism by which staining occurs. Unlike the usual oxidized form of indigo, pre-reduced indigo is soluble in water, saving you trouble when preparing it for dyeing. ( Log Out /  Create a free website or blog at WordPress.com. The volatility of the dye can cause loss of colour density, and staining of other materials at high temperatures. I suspect that there is no difference at all between pre-reduced indigos that are listed as being freeze-dried, dried, or instant, merely different ways of describing the same product. So, it’s very interesting that most of the denim product is colored by vat dyes. The fiber is immersed repeatedly in this oxygen-free dyebath, then exposed to the air, whereupon the water-soluble reduced form changes color as oxygen turns it to the water-insoluble form. This flies in the face of what I’ve also been told directly by an importer- if it comes from India it’s all synthetic. As a general principle, solvent dyes do not ionise. My main business is indenting. Once the vat dye is in its reduced “leuco” form, its solubility means it can enter or exit the fiber, along with the water it is dissolved in. Application of vat dyes is limited in practical life. Now our three chemical running on Tangail area like Kajibari, Rampur, Bolla, Chatihati , Pathrail and Shirajgonj .If you help me out we have a chance of good business here. The ring systems of the vat dyes help to strengthen the Van-der-Waals forces between dye and fibre. For example, vat blue 2 and 3 are halogenated or methylated derivatives and so are several violets. Vat dyeing is a process that refers to dyeing that takes place in a bucket or vat. The shape makes it easier for the dye to slide between the tightly-packed polymer chains, and the polar groups improve the water solubility, improve the dipolar bonding between dye and polymer and affect the colour of the dye. Disperse dyes have low solubility in water, but they can interact with the polyester chains by forming dispersed particles. I want same and if you can sent sample then very well. Each dye is named according to the pattern: – solvent + base colour + number. Three vat dyes may act as a filter of Pyr-Yellow but the other vat dyes. There are several ways for classification of dyes. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Photo-oxidation and -reduction of vat dyes on water-swollen cellulose and their lightfastness on dry cellulose. I expect that, as science students, you are already aware of such precautions. ( 880 ) 01711583944 North American dyesellers from which vat dyes can be ordered include Aljo Manufacturing, PRO Chemical & Dye, and Maiwa Handprints.