Oligomer is a smaller chain length of polyester made up of two or more molecules of basic ethylene terephthlate i.e. dimer or trimer, produced as a side reaction during the manufacture of polyester. The Oligoester because of its smaller chain length is in the form of a fine powder which is entrapped is basic polymer and migrates to the surface during high temperature polyester dyeing.

cyclic tris (ethylene terephthalate)

Higher the depth more is the

displacement of Oligomer to the fibre

surface. Typically polyester fibres

contain between 1.5-3.5% by mass of

low molecular esters, the principal

oligomer being cyclic tris (ethylene

terephthalate) with smaller quantities of

dimer, pentamer & other compounds.

Approximately 0.1 % to 1.0 % of

Oligomer is produced as a side reaction

in the manufacture of basic polyester.cyclic tris (ethylene terephthalate)

Spinning characteristics impaired. Filtration effect (inside – out variation) due to build up of

Oligomers in package. Reduced liquor flow through package of yarn because

spindle perforations are choked & improper pump pressure due to deposits on pump.

Variation in rate of rise of temperature due to deposits on heating elements

Dusting during coning & white particle deposits cause dulling of the yarn/ fabric especially in dark shades i.e. black & navy etc.

Higher energy costs Presence can cause nucleation & growth of dye crystals

or agglomeration of dye particles & hence dye spots, Duller shades, unlevelness & poor fastness.

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

Those skilled in the art have therefore tried to remove oligomers from polyester by means of various after-treatment methods.

For example, it is known that oligomers may partly be eliminated by rinsing the polyester with hot water or by subjecting the polyester to an alkaline reductive after-treatment in the presence of a tenside, for example a fatty acid polyglycol ester, at elevated temperatures.

However, cyclic oligomers may be difficult to remove and resistant to such an alkaline post treatment. Therefore, to be effective, alkaline treatment must be severe, which results in a significant loss of polyester fiber material.

 

Organic solvents have also been used to try to remove oligomers from polyester but it is difficult to find one that is compatible with and non-injurious to the textile material.

Chlorinated hydrocarbons, fluorinated hydrocarbons and hydrocarbons themselves have also been used in the art to remove oligomer deposits.

All of the before-mentioned treatments used in the art pose production problems along with time and cost issues.

Accordingly, there is a need in the art for removing oligomer deposits that results in minimal interruptions in production and poses little threat to the quality of the polyester or polyester textile product.

Cyclic tris (ethylene terephthalate) is insoluble in water. Solubility is increased in presence of carriers like Dylev-EC, Dylev-CB , Dylev-DIF promotes migration of the trimer to the surface of fibre. But a dispersing agent like Dytec-DAN should be present to prevent crystallization & deposition of the oligomers.The longer the dyeing time the more oligomers will be released. Dark shades may produce more oligomer than paler shades because the dyeing time is longer.

When oligomers are released from polyester fibre, after some time at 130ºC, there will not be an efficient dispersing agent in the bath to prevent crystillization of the oligomers, and to prevent small particles of oligomers coming together to form agglomerates, & depositing on the yarn & the machine. Altrasperse-OLG liquid will maintain the oligomers in fine dispersion form & prevent redepositing of the trimers on the fabric so that when the machine is drained more oligomer goes down the drain.

Receipe during dyeing:In the case of dark shades and/ or long dyeing times, the following formulation is recommended :0.5 – 2 g/l Altrasperse-OLG liquid0.5-1.0g/l Dylev DIF / Dylev-CB0.5 g/l Dytec-DAN

Receipe during alkaline weight reduction of polyester:During alkaline weight reduction of polyester terephthalic acid is generated & to keep it in dispersion form Altranol-OR is very effective. Altranol-OR act as a effective micronizer & disperser of terephthalic acid.

Altranol-OR 1-2 g/l 75-80ºC for 20-30 mins

100-130ºC Warm rinsing

Weight reductionNeutralization

Altranol-OR(75-80ºC)

The dyeing machine to be cleaned is filled with water and the following is added:3-5 g/l Altranol-ORM4-6 ml/l Caustic soda solution 50%1-2g/l Sodium hydrosulphite

 Then heated upto 135ºC and treated for 20-40 mins. If possible, drain immediately and rinse. Otherwise, cool to approx. 90ºC, drain and rinse. On dyeing machines such as jets and overflows the additional use of a CO back cloth has proved of advantage to increase the cleaning effect further.

Pot After Dyeing

Pot After cleaning with Altranol-ORM

In order to assess dispersion performance of oligomer remover , the degree of dispersion is to be compared with and without Altranol-OR/Altrasperse OLG in the black filter paper

(A filter paper is soaked in the black direct dyes for 24 hrs & dried)Extracting the oligomer in Dioxane:

Dioxane 100% 100-250 ccPolyester cloth 5-20 gmTreatment 130ºC x 60 min

Oligomer dissolves in dioxane

Take 5-20 gms of undyed polyester fabric & to it add 20 times the weight of fabric Dioxane & treat the bath at 130ºC for 60 mins, cool & collect the solution. This is the solution of oligomer in Dioxane.

Oligomer dispersion test (Contd)Test on dispersion in acidic solution

Take 10 cc of the above collected oligomer solution & to it add 200cc of water & keep it aside for 15-20 mins, white precipitates of oligomer will start settling.

Bath-1(Blank)Oligomer solution 10 cc/200 ccAcetic acid pH=5 Bath-2(With oligomer remover)Oligomer solution 10 cc/200 ccAltrasperse-OLG/Altranol-OR 1-2 g/lAcetic acid pH=5 The above bath with & without oligomer remover is kept for 60 minutes & the filter through the black dyed filter paper & observed for the residual oligomer or white precipitates against blank.

2. Test on dispersion during weight reduction 　 　 　Test Purpose: Dispersion of terephthalic acid generated by weight

reductionSpecimen: Liquor after weight reductionTest items: Vacuum filter(Using black coloured filter paperTest condition

Products Blank 1 Test No-1 Blank-2 Test No-2

Liquor　after　weight　reduction

20%　solution

20%　solution

5%　solution

5%　solution

Altranol-OR

--- 2　g/l --- 2　g/l

Acetic　acidpH

4.5-5.5 4.5　-　5.5 4.5　–　5.5　 4.5　–　5.5

Blank

20%　liquid　of　caustic　treatment

20%　liquid　of　caustic　treatment

Altranol-OR(2　g/l)

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