Textile Dyes » Dyes for Cellulose Fibers
The most common material in plant cell wall is cellulose. So, fibers derived from the different parts of the plants are known as cellulose fibers. Only in cotton fibers, it is found in almost pure form but it is present in other parts of the plants like wood, leaves etc., in a combined form with lignin and hemicellulose. Cellulose fibers are those fibers which are made of plant cell. But, the disadvantage of these fibers is that these are less stronger because there is a lack of strength of inter facial bonding among the cells of the plants. These fibers are natural fibers.
To get wide range of colors, cotton fibers are dyed with chemical dyes. The chemical dyeing of these cotton fibers requires a a large quantity of water but when this water is disposed then it may cause water pollution and soil pollution. Due to the negative impacts of this dyeing process, another process has been developed to obtain colored cotton and this is known as Gene Transplantation.
Genes of wild cotton varieties are crossed with the genes of cultivated white colored cotton and then the colored cotton are obtained. The research that had been followed for developing the Gene transplantation was conducted at The University of Agricultural Science, Dharwad (Karnataka). Many colors that have been developed are White, Yellow, Purple, Orange, Red, Blue and Black.
Vat Dyes are those dyes, applicable to the substrate in reduced, soluble form. After that, these are oxidized to the original insoluble pigment. Quinonic dyes, Anthraquinone dyes and Indigoid dyes are the three commonly used vat dyes. The inability of these vat dyes to dye the fibers directly is due to their insoluble nature in water.
Alkali metal salts of these dyes can be produced by reduction in alkaline liquids. These salts are soluble in water. This thing makes these dyes unpopular to the home dyers. Because in most of the cases, they don't have a reducing agent.
Through oxidation, Vat dyes are obtained. When vat dyes are bleached with other dyes then these result in more brightness. The bleaching process is very costly and therefore can be used on high-end products.
Fast washing can be done by Vat dyes. Today, several artificial dyes have come into existence. As these are cheap so the future of these artificial vat dyes is very bright. Both cotton and woolen clothes can be dyed by Vat dyes. Other fibers can also be dyed by Vat dyes.
Azonine (Direct) Dyes
Azonine Dyes are those direct dyes which are comparatively cheaper direct dyes. These dyes have good coloring property. These dyes are useful for those users who don't concern much about the fastness properties of the direct dyes.
Fiber Reactive Dyes
For dyeing cotton and any other cellulose fibers, Fiber Reactive Dyes are considered as the best dyes. These dyes are also used for dyeing protein fibers. These dyes form the original covalent bonds with the cellulose or protein molecules. Due to this fact, these dyes are the most permanent of all other types of dyes. The formation of covalent bonds allow these dyes to become an integrated part of the cellulose fiber molecule. This feature also allow the end-users to wash white cotton clothes along with colored clothes.
Vinyl Sulphone Fiber Reactive Dyes
One form of Fiber Reactive Dyes is Vinyl Sulphone Dyes. But, these dyes are less reactive as comparison to Fiber Reactive Dyes.
Vinyl Sulphone Fiber Reactive Dyes can be used very friendly with cotton, silk and wool. Cotton requires high pH scale and low heat but wool requires just the opposite elements. Vinyl Sulphone Fiber Reactive dyes need more heat and more time to remain in soluble form in water to react with the fibers. On the reactive part of its molecule, vinyl sulphone dye consists a masking group. This assists it to remain non-reactive till it is not removed from the dye water. This is also the reason for its longer lasting in the water.
Direct Dyes are commonly used on cotton fibers. These Dyes are mixed in All Purpose dyes along with the Acid Dyes. The color of Direct dyes on cotton fibers is not bright in respect to other dyes. The wash fastness of these dyes is not very good. The only advantage of these dyes is that the light fastness is little more better. Lightfastness means the resistant capacity against fading in light. But, this is also in few cases only. One more benefit of using Direct Dyes is that these can be used in the same dye bath with the Acid Dyes.
The main characteristics of Sulphur Dyes are these have lustrous grains, make a complete black shade having a slight reddish or greenish impact. These dyes are used for jigger, cotton and viscose rayon. Sulphur Dyes are mainly used for dying cellulose fibers. Apart the cellulose fibers, these can be also used for dyeing staple fibers and yarn.