Polyester oligomer

Nearpon TO

Polyester oligomer dispersant to minimise deposition of oligomers

on the polyester fibre surface and on machinery

Typically polyester fibres contain between 1.5 and 3.5% by mass of low molecular weight esters, the principal oligomer being cyclic tris(ethylene terephthalate) with smaller quantities of a dimer, pentamer and traces of other compounds. These substances migrate from PET fibre duriing dyeing and steam setting and, to a lesser extent, during dry-heat setting. Migration of oligomer increases with increasing temperature. It has been shown that after 1 hour at 130° C in the presence of a dispersing agent, an average of 0.13% of cyclic trimer was deposited on the surface of both untexturised and texturised PET. Treatment in the presence of a carrier increased the surface deposition to an average of 0.18% showed that carriers can promote migration of the trimer to the surface of the fibre. A similar quantity (about 0.2%) of oligomer is believed to be present in the dyebath and, in part, deposited on the surfaces of the dyeing machine.Our results further demonstrate that HOY causes the highest oligomer migration, followed by DTY, and then POY. Importantly, the problem of oligomer dust deposits on fibre and machinery is getting worse as dyers attempt to meet contemporary environmental standards by dyeing at lower and lower liquor ratios.

Problems caused by oligomer deposits

Spinning characteristics impaired

Reduced liquor flow through package of yarn because spindle perforations become blocked, and deposits on pump cause improper pump pressure.

Presence can cause nucleation and growth of dye crystals or agglomeration of dye particles and hence dye spots, unlevelness, and poor fastness.

Deposits on machine guides at winding or twisting cause high tensions and increased friction on the yarn, leading to poor package build and end breaks.

White powdery deposits cause dulling of the yarn/fabric especially in dark shades, black, navy etc.

Variation in rate of temperature rise due to deposits on heat exchanger

Need for more frequent cleaning of dyeing and winding machines, hence increased down time and lower efficiency.

NEARPON TO has a unique ability to remove oligomers from the surface of the polyester fibre and hold them in dispersion so that they can be rinsed away.

The photomicrographs show a polyester yarn with which a customer was experiencing unusually severe problems with oligomers.

The following procedure has been applied:

SCOUR

2 g/l Nearpon 266 ECO1 g/l Nearchel TMC30 mins at 90° C

DYE

3 % Nearsper Black SR1 g/l Neargal DN1 g/l Neargal HP-MF New60 mins at 130° C

REDUCTION CLEAR

2 g/l Neariserve FBT3 g/l caustic soda 36° Bé2 g/l NEARPON TO30 mins at 80° C

Scanning electron microscope examination

untreated

after dye

after NEARPON TO