The abovementioned recipe and procedure of dyeing are standart and can be changed and specified according to type of the equipment and also kind of coloring material.

4.5. Direct dyes Direct dyes may be used for dyeing cotton and other cellulose fibers. Direct dyes simple in application, are suitable for dyeing on any equipment, well combined with each other.

Methyl Orange

Cotton

Some marks are suitable for dye­ing wool, kapron and natural silk. A direct dye forms a strong ionic bond with the fabric. I is important for dye­ing materials from mixes of fibers. The dye either contains or is capable of forming a positive or negative charge which is electrostatically attracted to a negative or positive charge on the fiber. For example, the direct dye picric acid is a strong acid and interacts with the basic side chains in wool to form a salt linkage between itself and the fiber. On the other hand, malachite green bonds to the acidic side chains in the wool fibers. Malachite green is a member of the important triphenylmethane structural class of dyes.

Direct dyes may be used as acid dyes.

Dyeing by fabrics is carried out by two methods:

1. In alkaline medium:

Composition of dyeing bath, %:

Dye. . . . . . . . . . . . . . . . . . . х

Sodium chloride. . . . . . . . 5-10

Soda. . . . . . . . . . . . . . . . . .2.0

Water. . . . . . . . . . . . . . . . .Y

2. In neutral medium:

Composition of dyeing bath, %:

Dye. . . . . . . . . . . . . . . х

Sodium chloride. . . . .5-10

Water. . . . . . . . . . . . . Y

Under periodic method of dyeing duration of dyeing at optimum temperature is 45-60 min. After dyeing coloration of middle and deep intensity is recommended to fix by fixing agents DTSU, DTSM and others.

4.6. Reactive dyes

Reactive dyes are used for cellulose materials dyeing such as cotton, flax and viscose.

Furthermore they dye natural silk, wool and polyamide fibers. The reactive dye assortment includes the whole gamut of colors ranging from yellow to black and is characterized by shade brightness and purity excelling other cellulose fiber dyes in these properties.

Reactive dyes have good leveling ability, they may be combined with each other thus extending the color gamut.

There is a variety of dyeing methods that are used for fibуr, yarn, fabric and knitwear dyeing applying both batch and continuous equipment.

The principle difference of these dyes is their ability to chemical interaction with cellulose fibуr.

The strong dye-fiber bond provides wet treatment resistant and lightfast dyeings.

Reactive dyes are produced as non-dusting powders well soluble in water.

Reactive dyes assortment of the JV Ltd. SC „Cation” соnsists of two groups:

— Reactive dyes with index „Kh”;

— Reactive dyes without any index.

These dye groups are differ in their reactivity and in the field of their application. Reactive dyes with the index „Kh”; possess the greatest reactivity. They are recommended for batch, semi-continuous and continuous methods of cellulose dyeing. The dye bath temperature of 20—40 °C is used in the batch methods of dyeing.

Alkaline solutions of reactive dyes with the index „Kh” are the least stable at storing. Reactive dyes without any index are characterised by the least reactivity. They are used primarily for semi-continuous and continuous methods of cellulose dуеing and printing.

Reactive dyes with the index „Kh” are dissolved at temperature under 50 °C, non-indexed reactive dyes are dissolved at temperature close to the boiling point. The dyes are mixed with a small amount of warm water to form a paste and then the warm or hot water is added until completely dye dissolving.