Printing of polyester with disperse dye:
Polyester is a hydrophobic fibre, compact in structure and non-polar
fibre so water soluble or ionic dyes cannot be applied on polyester. Special
dyes called disperse dyes, which are insoluble in water, are the most suitable
dyes for printing polyester. Commercially available disperse dyes are coralene,
foron etc. They give good colour value with good fastness properties under
acidic pH. Excellent wet fastness properties are obtained, provided that the
fixation and after treatment processes are correctly carried out.
The selection of the thickening agent depends on fabric structure,
printing method, solid content of thickener and fixation method. High solid
content thickeners like crystal gum or british gum give optimum sharpness of
outlines, but form brittle films that crack and scatter dye by ‘dusting off’.
The lower solids content thickeners such as alginates and locust bean
(modified), form elastic films and are easily washed out. As they are costly
than high solid content thickeners, often mixture of both or mixture with
starch ethers is used.
Now-a-day, TKP is widely used as thickener in printing of polyester
due to cost factor and ease of availability. TKP also give good sharpness but
colour value as compared to guar gum is little less. A combination of guar gum
and TKP gum is also used for better result.
Emulsion thickening paste is used in case of prints to be fixed by
thermofixation method. Now a day use of synthetic thickeners is increases day
by day due to ease of availability and constant quality.
Disperse dyes on polyester applied in an acidic pH for that
non-volatile organic acid like tartaric acid or citric acid or acid liberating
agent like sodium acetate, ammonium sulphate or ammonium tartarate is used to
maintain pH 4.5-5.5.
A mild oxidizing agent like sodium chlorate is used to prevent
reduction of the dye during steaming.
Swelling agent like Noigen EL-40 is added in print paste where print
is going to fix by pressure steaming.
Glycerin or PEG 400 is added as lubricating agent in paste.
Printing
paste recipe:
The content of
the print paste will depend on the fixation method to be employed.
X parts
|
Disperse dyes
|
1 - 2 parts
|
Dispersing agent
|
20 parts
|
Boiling water
|
1 – 2 parts
|
Tartaric acid or Citric acid
|
1 parts
|
Sodium chlorate
|
1 parts
|
Non ionic swelling cum
penetrating agent
|
1 parts
|
Glycerin or PEG 400
|
Y parts
|
Thickening paste
|
100 parts
|
Total
|
For
fixation in super heated steaming or thermofixation, dyes fast to sublimation
are preferred. In case of fixation
by super heated steam, fixation accelerator like Levocol HTS is added in pace
of swelling agent. Fixation accelerator accelerates the rate of dye fixation
during short period at high temperature steaming. In case of fixation by thermofix
method, fixation accelerator along with hygroscopic agent like urea is used.
The well prepared polyester fabric is printed by suitable method
using above printing paste and dried. The fixation of disperse prints on
polyester can be carried out by following methods.
1. High Pressure Steaming
Pressure:
25 lbs/inch2 or 2.5-3 kg/cm2
Temperature: 125-130°C
Duration: 30 minutes
Machine:
pressure ager or star ager
Outcome: give full colour value
2. Super Heated Steaming
Pressure: atmospheric pressure
Temperature: 160-175°C
Duration: 8 minutes
Machine: loop ager
Outcome:
give very bright prints
3. Thermofixation
Pressure:
hot air
Temperature: 200-210°C
Duration: 1 minutes
Machine: curing, polymerizer or stenter
Outcome:
little dull shades produced with 10-15% less colour value
After
treatment:
The fabric is then rinsed first with cold water, then reduction
clearing treatment is given at 60°C for 15 minutes in a bath containing 2 gpl
hydros, 2 gpl sodium hydroxide and 2 gpl NID to improve washing and rubbing
fastness of the prints. The process is followed by rinse with hot water first
and then with cold water and finally with cold acidic water to neutralize
printed fabric.
very nicely done
ReplyDeleteIt's Nice!
ReplyDeleteKudos! Carry On!
very nice sir. carry on
ReplyDelete