Fundamental of textile chemical processing

1. Fundamental of Textile
Chemical Processing
Lecture 16
1

2. Content
 Flow chart of wet processing
 Pre-Treatment
 Dyeing or Colouration
 Printing
 Finishing

3. Process layout in pretreatment section
Grey section
Fabric
receiving &
recording
Inspection
Grey store
Lot making
Singeing
Bleaching
Scouring
Desizing
Mercerizing/
causticizing

4. Process layout in pretreatment section
Pretreatment
Dyeing
Printing
Finishing

5.  Basic dyes are salts of organic bases. They are also known as cationic dyes because of
the presence of positive charge in the dye molecules under dyeing conditions
 The basic dyestuff are most commonly used for dyeing polyacrylonitrile or acrylic
materials
 Negatively charged acrylic fiber attracts the positively charged dye cations for ionic
bonding
 Due to high attraction between the oppositely charged fiber and dye molecules, there
is risk of unlevel dyeing because of high rate of dyeing
 This risk may be reduced by careful control of dyeing temperature and used of
suitable retarding agents
Dyeing with Basic dyes:

6.  The dye is generally used to produce bright and deep shades with superior light and
wash fastness
 Its application is similar to that of direct dyes but requires different and more precise
controls with auxiliaries and temperature
 Negatively charged acrylic fiber attracts the positively charged dye cations for ionic
bonding
 These dyes exhibit an unlimited shade range with high tinctorial strength, brightness
and many colours are having fluorescent properties
 These dyes have a very high strike rate, therefore levelling is poor. So, we need
levelling agent during dyeing to promote shade evenness.
Dyeing with Basic dyes:

7. Mechanism of Basic dyes:
http://dyeingworld1.blogspot.com/2010/01/basic-dyes.html

8.  Basic dyes can also be applied to silk and wool
 These dyes are generally applied in the presence of acids like citric acid, acetic or
formic acid to neutral pH bath to obtain 4-5.5 pH
 Relatively economical in usage and shows good brightness
 Basic dyes are sensitive to temperature, so that both temperature of the dissolution-
dilution and dye-bath should not be too high. Ranges from 80°C to 100°C.
 These dye has excellent light fastness because of their resistance to destructive effect
of ultraviolet radiations in sunlight
 Rubbing and washing fastness properties of basic dyes fall in average to good range
Properties of Acid dyes:

9. Questions