Fixation of printing
All textile material is require dye fixing after dye and printing
printing fixation following type there are given below
Type of printing fixation
1. Steam Fixation
2. Dry Heat Fixation
3. Wet Fixation
4. High Temperature and High Pressure
Steam Fixation
This method is suitable for all class of dyestuffs. In the steamer, fibre
and thickener absorb a certain amount of moisture. As a result, swelling of the
fibre and of the film of thickener takes place.
The dyes and chemicals
incorporated in the printing paste pass into the solution and thus enter into the
reaction. During this phase, the dye commences to penetrate the swollen fibre.
Depending upon the class of dyestuff and the kind of fibre, chemical or
physical combination of the dyestuff takes place with the fibre molecule.
In
order to accelerate the process of fibre swelling and dyestuff penetration. The
printing paste may contain swelling agents, such as urea, thiourea, glycols,
carriers, etc. In case of synthetic fibres, the fibre swelling takes place only
under high pressure or high temperature steaming.
Vat, indigosol, azoic,
reactive and aniline black can be fixed by normal steaming. Disperse dyes on
synthetic fibres are fixed under high pressure or high temperature stemming.
Dry Heat Fixation
Usually pigment, reactive and
disperse ayes are fixed by this process Baking chember or hot-air stenter having
high temperature tones is use for this purpose. Fixation takes place 130°-150°C
within 5 to 3 minutes pigments, 150 C for 5 minutes for reactive: and 180°-200
C for to 30 seconds for disperse dyes
Wet Fixation
The methods of wet fixation for the different types of dyes are :
Nitrite process for indigosols: oxidation of vat dyes, aniline black and metal
complex formation in phthalogen blue, alkali fixation of reactive dyes and
two-phase printing of vat dyes and reactive dyes
High Temperature and High Pressure
Steaming In a print house, the steaming operation required to fixation dye on the fabric has been often a bottleneck and also it is a relatively expensive process as far as steam consumption is concerned. In order to overcome this problem two processes viz.,high temperature steaming (Flash aging) and high pressure steaming process and mchines have been developed. In the case of synthetic fibres, disperse dyes do not fix spite of long steaming at 100-102°C
in pressure steaming they can be fixed within 20 to 30 minutes at .5 to 2 atmosphere pressure similarly. in high temperature steaming these colours are fixed at 180°-200°C in 30 to 50 seconds only.
Pressure steaming is a discontinuous process and is not suitable for high rates of production.
High temperature steaming fixes reactive dyes on cotton and reactive/disperse or metal complex dyes on synthetic fibres in 30 to 60 seconds only. Reactive dyes fixed by high temperature steaming give better yields than thermofixation process.
