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Different types of Dyeing process


Different types of Dyeing process
Basic dyes are ionic in nature. They ionize into coloured contains and colorless anions. First of all, Perkin invented this colour. The first member of this class according to his name was Perkin’s mauve. In these dyes the coloured portion (Present in the cotton) is derived from free or substituted amino group such as –NH2, –N(CH3)2, –N(C2H5)2 etc. These dyes are generally in soluble in water or sparingly soluble in water. The dye base becomes soluble in water when they from hydrochlorides, oxalates, acetates, sulphates etc. Since basic dyes are not easily soluble in water, the best way to dissolve them into paste with water, an equal weight of acetic acid (40%) and then pouring boiling water with constant stirring. If boiling water is directly poured over the dye powder, it forms a tarry mass. Pasting of the dye powders may be done with methylated spirit, in which they are suitable. The dye solution thus prepared should be filtered before adding to the dye bath.
 Application of Basic Dye on Jute
Amongst all the vegetable fibres, jute fibre has direct affinity for basic dyes. Since the jute fibres have lignocellulose and uric acid, they need not mordanting during dyeing with basic dyes but a small amount acetic acid is added in the dye bath so that the dye completely dissolves and penetrate within the fibre and removes the alkalinity of water. Acid dyes nearly all sodium salts of organic acid. Most of the acid dyes are sulphonic acid salts, but there are a few containing carboxylic acid groups. The anion is the active coloured component. The acid dyes have a direct affinity towards protein fibres and are used in wool and silk and polyamide dyeing. Most of them will not exhaust on cellulosic fibres. Since they resemble the direct dyes a few of them dye cellulose quite well.
Application of Basic Dye on wool
Wool is composed of millions of keratin macro molecules arranged in crystalline and amorphous regions, wool molecule is represent shortly as follows:      H2N – W – COOH (Wool) Each macro molecule has a carboxyl group (–COOH) at one end and an amino group (–NH2) at the other end. Under certain conditions, the hydrogen ion attached to the carboxylic ion is transferred to the amino group at the other end of the macro molecule so that, the two ends of the keratin molecular chain acquire opposite
The dye bath is fully prepared according to the above recipe. The scoured woolen material is washed and dipped into the dye bath. Temperature is slowly raised to boil within 30 minutes. First of all the dye stuff is pasted with cold water then H2SO4 is added slowly so that, the dyestuff completely dissolves. Then the volume of dye bath is increased by adding 20 times water. After 30 minutes of dyeing material is taken out from the dye bath and salt is added and stirred so that, the mixing is thorough. Then the material is again put into the dye bath and dyeing continued so that, the total time is 1 hour. The material is rinsed & dyeing is neutralized with addition of 1% NH3 solution and after treated with 1% soap solution for 10 – 15 minutes.
Application of Basic Dye on Silk
Soap solution is prepared by taking 75cc water and 25g soap which makes 25% soap solution. The silk is weighed and 30 times water on the weight of the dye is added into the dye bath & then acetic acid is mixed with the dye thoroughly with constant stirring and the temperature of the dye bath is raised slowly to 400C. then the silk material is entered into the dye bath and agitated until the dye is completely absorbed. The dyed material is then taken out from the dye bath, washed well and dried.
Application of Basic Dye on Nylon
The dyestuff pasted with T.R. oil and then hot (Boil) water is added to dissolve the dye completely so that a homogeneous solution is formed.30 times water is taken in another bath to which above prepared dye solution is added after brilliant and then ammonium acetate is also added. The material (Nylon) is immersed in the dye bath and temperature is slowly raised to 900C and dyeing continued for 45-60 minutes is then washed and dried. The dyed washed material may be after treated with 2-3% soap solution.

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