Dyes

We offer a range of salt free dyes that are extremely eco -friendly and have excellent fastness properties. These dyes exhibit excellent dye exhaustion and have improved dye fixation properties. Our range of salt free dyes are manufactured using membrane technology and find utility in Inkjet Industry. Salt and other impurities are removed from the dyes, which improves product solubility. Our array of Salt Free Dyes include:

Reactive dyes are a group of colored organic substances that are primarily used for tinting textiles. They attach themselves to their substrates by a chemical reaction, forming a covalent bond between the molecule of dye and that of the fiber. Hence, the dyestuff becomes a part of the fiber and has low possibility to be removed by washing than the dyestuffs that adhere by adsorption.

The reactive dyes were designed for cellulose fibers for the very first time, and are still used in this way in most cases. Fiber Reactive Dyes are also commercially available for protein and polyamide fibers. Theoretically, these dyes have been developed for other fibers, but practically they are not yet commercial. The reactive dyes contain a reactive group, which when applied to a fiber in a weak alkaline dye bath, formulates a chemical bond with it. These dyes can also be used to dye wool and nylon. In the case of nylon, they are applied under weakly acidic conditions.

The vital characteristic of the reactive dyes, is the formulation of covalent bonds with the substrate to be colored. These dyes form a chemical bond with cellulose, which is the main component of cotton fibers.

These fiber reactive dyes are the most permanent of all types of dyes. Unlike other dyes, these reactive dyes form a covalent bond with the cellulose or protein molecule. Once this bond is formed, a whole molecule is formed, as the dye molecule has become a part of the cellulose fiber molecule. Hence, garments that have been dyed in bright fiber reactive colors, can be safely washed with white clothing, a number of times, without damaging the whites. In comparison to all the other dyes, these reactive dyes chemically bind to the textile fibers, which significantly improves the product's colour stability and wash ability. Thus, reactive dying of cotton is presently the most widely used textile dying process in the world.

Acid dyes are water soluble anionic, which are applied to fibers such as nylon, silk, wool and modified acrylic fibers using neutral to acid dye baths. Fastness to the fiber can partly be attributed to salt formation between anionic groups that are present in the dyes and cationic groups in the fiber. These water soluble acid dyes are not substantive to cellulose fibers. Acid dyes find application both commercially as well as by the studio dyer to dye protein or animal fibers such as wool, silk, mohair etc., and some nylons and synthetics. Application of acid such as vinegar, acetic or sulphuric acid is required by the acid dyes to set the colour.

These dyes are non-caustic and in many cases non-toxic as well. They can be used in dyeing process where mild acid such as vinegar is used and for the various types of bonds they form with the fiber. Some acid dyes are significantly more toxic than fiber reactive dyes, while some are even safe enough to eat and are available as food colors.

Acid dyes fall into several classes:
1. Leveling acid or strong acid dye
2. Milling or weak acid dyes
3. Super milling or fast acid or neutral acid dyes

Difficult to categorize these dyes in different classes, Acid Dyes are sold under the trade names of Kiton, Erio, Intracid, Sandolan, and Amacid. These are the acid dye component, used for all purpose or union dyes such as Rit and Tintex, says Knutson.

Histological dyes are mainly classified either as acid or as basic dyes. An acid dye exhibit the property of a union (negatively charged) in solution, while a basic dye exhibit a cation (positive charge) properties. For example, in the hematoxylin-eosin stain (H&E), the hematoxylin-metal complex is positively charged or a cation on the other hand eosin acts as an acid dye. Dyes which are a part of the acidic groups, like the sodium salts of sulfonic acids or phenolic groups are soluble and have very less tinctorial value but they have greater light fastness than other basic dyes. These dyes do not form lakes with tannin. Acid dyes are mainly used for dyeing leather, paper, etc., and they are preferred as they have the ability to produce brighter and more uniform colors. Normally applied using an acid dye liquor (acetic, formic, or sulphuric acid); unless applied from a neutral or only slightly acid dyebath, with a pH of 6.0 to 7.0. The use of acid dye is most likely to result in acid degradation of the material dyed.

Direct dyes are yet another class of dyes, one of the two dyes that are mixed in 'all purpose' dyes such as Rit. (The other type dye present in the mixture is an acid dye, which does not have long presence in any cellulose fiber for long.) The colors of the direct dyes are comparatively duller than those of fiber reactive dyes. The wash fastness is also poor - anything dyed with them will 'bleed' forever. One advantage direct dyes is that they are light fast, i.e., resistant to fading in the light when compared with fiber reactive dyes. The "Direct Dye" classification in the color index system mainly refers to the various planar and highly conjugated molecular structures. These structures also contain one or more than one anionic sulfonate group.

Owing to these sulfonate groups, the molecules are soluble in water. Though most direct dyes can be obtained in powder form, receiving them as liquid concentrates is becoming extremely popular. The concentrates are advantageous as they are easy to handle and meter. Their main disadvantage is that the surfactants and co-solvents that are required to keep the dye concentrates stable might interfere with retention and sizing in the case of very deeply colored grades.

Direct dyes find utility on cellulose fibers such as cotton, rayon, and linen. They are not permanent as the cold water fiber reactive dyes, which most serious dyers prefer for use on cellulose fibers. But in cases it is advantageous to use direct dyes as they may be more light fast than the similar shades of fiber reactive dyes. These dyes require an appropriate after-treatment, as they will bleed with every washing, losing their brightness other clothes washed in the same load may also be damaged. However, after special treatments this problem may be solved. A product called Retayne, an ionic bulking agent which mainly "glues" the dye into the fiber, is a very effective after treatment given to the fabrics that have been dyed with direct dyes. Despite claims vinegar cannot be used as a color fastener, in fact vinegar cannot be used to set any dye on cotton or other cellulose materials.

The name 'direct dye' implies that they do not require any form of 'fixing'. They are almost always azo dyes, which have some similarities to the acid dyes. The acid dyes also have sulphonate functionality, but in such cases it is only to improve solubility, as the negative charges present on dye and fiber will repel each other. Their flat shape and length enables dyes to lie along the side of cellulose fibers and maximize the Van-der-Waals, dipole and hydrogen bonds. Below is a diagram of a typical direct dye.

Note : The Sulphonate groups are spread evenly along the molecule of the opposite side to the hydrogen bonding -OH groups, to minimize any repulsive effects.