When it comes to choosing a dye for industrial that provides not only high quality color fastness but also great resistance to weathering and light, a Vat dye is an obvious choice. Generally, Vat dyes exhibit qualities of a speedy effect and a good degree of exhaustion besides which they diffusion within the fiber at a very slow pace. These dyes have a fairly equal particle size when produced commercially as a large particle size results in poor stability besides causing a reduced color yield in some dyes.
Vat dyes are divided into four main categories depending on the temperature, and the quantity of caustic soda hydrosulfite and salt used for dyeing. The first category is the IN dyes which require high temperature as well as large quantities of caustic soda and hydrosulfite. The IW dyes form the second category and they require medium temperature and medium quantity of caustic soda and hydrosulfite plus salt. The next category is of IK dyes which require low temperature and a small amount of caustic soda and hydrosulfite plus salt. The fourth category is of IN Special dyes which require a greater amount of caustic soda and higher temperature than IN dyes.
A number of methods for using Vat dyes have been designed and used. Various factors determine the rate of reduction of Vat dyes, including temperature, time and pH as well as the concentration of the reducing agent. The most common type of reducing agent used for coloring with Vat dyes is sodium hydrosulphite, which is also known by the name of hydros. It is important to understand that only a part of hydros is actually used up in the reduction of Vat dyes while, a major percentage of the compound is destroyed by its reaction with atmospheric oxygen.
The coloring of cellulosic fibers using a dye is completed in various stages. In the first stage the insoluble vat pigment is converted into soluble sodium leuco-vat anions, which in turn is diffused into the cellulosic fibers. The next stage involves the remomal of all the alkalis and reducing agents from the fiber by washing them off. In the next stage, the soluble dye contained within the colored fiber is converted back into insoluble pigments through oxidation. The final stage is the soaping of the fiber which helps in re-orientating and associating the isolated vat pigment molecules to create a more crystalline form.
Vat dyes are divided into four main categories depending on the temperature, and the quantity of caustic soda hydrosulfite and salt used for dyeing. The first category is the IN dyes which require high temperature as well as large quantities of caustic soda and hydrosulfite. The IW dyes form the second category and they require medium temperature and medium quantity of caustic soda and hydrosulfite plus salt. The next category is of IK dyes which require low temperature and a small amount of caustic soda and hydrosulfite plus salt. The fourth category is of IN Special dyes which require a greater amount of caustic soda and higher temperature than IN dyes.
A number of methods for using Vat dyes have been designed and used. Various factors determine the rate of reduction of Vat dyes, including temperature, time and pH as well as the concentration of the reducing agent. The most common type of reducing agent used for coloring with Vat dyes is sodium hydrosulphite, which is also known by the name of hydros. It is important to understand that only a part of hydros is actually used up in the reduction of Vat dyes while, a major percentage of the compound is destroyed by its reaction with atmospheric oxygen.
The coloring of cellulosic fibers using a dye is completed in various stages. In the first stage the insoluble vat pigment is converted into soluble sodium leuco-vat anions, which in turn is diffused into the cellulosic fibers. The next stage involves the remomal of all the alkalis and reducing agents from the fiber by washing them off. In the next stage, the soluble dye contained within the colored fiber is converted back into insoluble pigments through oxidation. The final stage is the soaping of the fiber which helps in re-orientating and associating the isolated vat pigment molecules to create a more crystalline form.
