Generation and removal of oligomers

It is common to question that the oligomer produces dyeing defects, which seriously affects the quality of the product, at the same time, it will contaminate the equipment and is difficult to clean. Here’s a summary of the problem:

1  Definition

Oligomer is also called Oligomer, oligomer and short polymer

It is a low-molecular compound with the same chemical structure as polyester fiber, which is a by-product in the spinning process of polyester fiber. THE GENERAL POLYESTER CONTAINED L% ~ 3% oligomer.

Oligomer is a kind of polymer which is composed of fewer repeating units and its relative molecular mass is between small molecule and high molecule. The English word “Oligo”comes from the Greek Mark Mark Mark II γοοgue, which means “Some”. Most polyester oligomers are cyclic compound of 3 ethyl terephthalate.

2 Influence


The surface of the cloth produces spots and spots of color, and the yarn dyeing produces white powder.


When the temperature exceeds 120 °c, the oligomer can dissolve in the dyeing bath and crystallize out from the solution, and combine with the condensed dye. Cooling deposited on the surface of machinery or fabric into red spots, spots and other defects. Disperse dyes generally keep at 130 °C for about 30 minutes to ensure the depth and fastness of dyeing. Therefore, the solution, light color can choose to keep at 120 °C for 30 minutes, dark color must be stored before dyeing pre-treatment. In addition, the basic condition of dyeing is also an effective way to solve the oligomer.

3  Comprehensive measure

01. The grey fabric was dyed with 100% NAOH3% before dyeing. Surface active detergent L% . Treatment at 130 °C for 60 MIN WITH BATH RATIO L: 10 ~ L: 15, the pretreatment before dyeing had some erosion effect on polyester fiber, but it was very favorable for removing oligomers. For Polyester filament fabric can reduce the “Aurora Borealis”, in the short fiber can improve the pilling phenomenon.

02. Controlling the dyeing temperature below 120 °C, using carrier dyeing method can reduce the production of oligomer and obtain the same dyeing depth.

03. Adding dispersing and protecting colloid assistant during dyeing can not only produce level dyeing effect, but also prevent oligomer from depositing on the fabric.

04. After dyeing, the Dye Solution was rapidly discharged from the machine at high temperature for a maximum of 5 minutes. Because the oligomer is uniformly distributed in the dye solution at 100 ~ 120 °C, it is easy to accumulate and deposit on the dye below 100 °C.

05. The formation of oligomer can be effectively reduced and the residual oil can be removed by alkaline dyeing, but the dyes suitable for alkaline dyeing must be selected.

06. After dyeing, the samples were cleaned with reducing agent, added 32.5% (380Be) NaOH 3 as 5ml/l, insurance powder 3 ~ 4g/l, treated at 70 °C for 30 Min, then washed cold, Hot and cold, and neutralized with acetic acid.


4 For the yarn, the white powder,

1) the thorough method is high temperature drainage

For example, a drain valve can be opened immediately after a constant temperature of 130 °c (120 °C is fine, but not lower, because 120 °c is the polyester glass transition point) , the most important thing is safety, which is the most difficult: the sound of a sudden discharge at high temperature and the vibration of machinery are alarming, and aged machinery tends to crack or loosen screws, machine Crack Dyeing Machine will explode (special attention) : If you want to refit, you’d better come to the original machine factory to design the refit, pay attention to the backwash phenomenon after discharge (experienced dye tank manufacturing company is very clear) high-temperature discharge has the advantage of shortening dyeing but poor reproducibility of the plant is very troubled

2) in plants that can not drain liquids at high temperatures, the use of Oligomer detergents can replace detergents in reductive cleaning processes, but the effect is not 100%
After dyeing, wash the cylinder frequently. After 5 cylinders of medium dark color, wash the cylinder once.

If the current flow dyeing machine has a lot of white dirt, the first priority is to wash the tank.


Post time: Jun-02-2022