Polyester Dyeing

HT-HP-Softflow

Polyester Dyeing:

Exhaust dyeing
Dyeing 100% polyester
When dyeing with disperse dyes the levelness of the dyeing is determined by the
dispersion stability, rate of dyeing and migration. An increase in migration demands
longer dyeing times. The rate of dyeing and therefore the heating rate must be controlled
in such a way that the dyeing is level from the beginning by means of controlled
adsorption.
Pretreatment of the goods
The material usually contains small amounts of water-soluble or emulsifiable preparations
which can be readily washed off. With tops, loose fibres and smooth or textured yarns
rinsing for IO min with cold water is often sufficient. Depending on the degree of contamination of the substrate one-bath scouring and dyeing of grey, unset piece goods of textured yarns is possible.

At the start of the dyeing process rinse the grey goods for 5 min at 20-30°C, then drain
and add 1-2 ml/l Sandopan LFW Liquid to the fresh bath. On reaching 60°C add the other
chemicals and continue dyeing according to the programme shown below:

Dyeing under HT conditions (130°C)

Form of the goods
- loose fibres and tops
- yarn
- piece goods (jet, overflow and beam dyeing machine)

Dye selection : Foron RD or S, SE and E dyes depending on the fastness require-ments
for the subsequent operations or for the final article.

Funtion Addition Product and amount
pH control essential  
dispersant advisable; Exception: sometimes
with very deep shades (black)
 
Levelling agent if required (substrate/form,
machine, shade)
 
Carrier or dyeing accelerant if required (Substrate/form,
machine, shade)
 
Anticreasing agents recommended on jet and overflow
machines
 

Remarks on dyebath additions
- Dyeing on partially flooded HT dyeing machines
Foam formation during dyeing in these machines causes considerable problems so low foaming chemicals must be used.

Standard HT dyeing programme for 100% PES
- set dyebath at 60°C
- add dyebath additions and run for 10 min
- add dye and run for 10 min
- heat to 130°C at 1.5°C/min
- fix for x min at the dyeing temperature as shown in table below
- cool, drain, rinse, aftertreat.

Fixation times under HT conditions

The fixation times generally depend on the fixation temperature, depth and quality of the material. The Foron RD dyes exhaust on tone onto the fibre during the heating up phase and the dyebaths exhaust rapidly and completely on reaching the final temperature of 125-135°C.As a result the fixation times can be shortened compared to the Foron S, SE and E dyes.

Guide values for average dyeing PES qualities with Foron RD dyes:

Depth Fixation time @125 deg C Fixation time @130 deg C Fixation time @135 deg C
Pale 0-10 minutes 0-5 minutes 0 minutes
Medium 5-15 minutes 5-10 minutes 5 minutes
Dark 10-20 minutes 10-15 minutes 10 minutes
V.Dark 20-30 minutes 20 minutes 10-15 minutes

The Foron S, SE and E dyes usually require 20-40 min longer than the Foron RD dyes at
the same temperature.

Cooling and draining the dyebath
- Loose fibres, tops, yarn : After dyeing the bath should not be cooled below 90°C due to
crystallization of the oligomers, but drained hot
- Piece goods on jet and overflow machines : After dyeing cool slowly (1-3°C/min) to
80°C, then drain and rinse.