Generation and removal of oligomers

Defects in oligomers are common, which seriously affect product quality and contaminate equipment, making it difficult to clean. Here is a question summary:

definition

Oligomer (Oligomer) also known as oligomer, oligomer, short polymer

It is a low molecular substance with the same chemical structure as polyester fiber, which exists in the polyester fiber. It is a byproduct in the process of polyester spinning. General polyester contains l % ~ 3% oligomers.

Oligomers are polymers that consist of fewer repeating units and have a relative molecular weight between small molecules and macromolecules. The word "oligomer" is derived from the Greek word ολιγος, meaning "some." Most polyester oligomers are cyclic compounds of three ethyl terephthalate esters.

influence

Cloth surface produce color spots, color spots; The yarn is dyed to produce a white powder

When the temperature exceeds 120℃, the oligomer can be dissolved in the dye bath and crystallized out of the solution, and combined with the condensed dye. Blemishes, spots and other defects deposited on the surface of machinery or fabric during cooling. Disperse dye dyeing generally at 130℃ for about 30 minutes to ensure the depth and fastness of dyeing. Therefore, the solution, the light color can choose to be kept at 120℃ for 30min, the dark color must be stored before dyeing for pre-treatment. In addition, dyeing is also an effective method to solve oligomers under alkaline conditions.

Comprehensive measures

1) 100% NaOH3% was used for grey cloth before dyeing. Surface active detergent l %. At 130℃ for 60min bath ratio l: 10~l: 15, the pretreatment method has certain erosion effect on polyester fiber, but is very beneficial to the removal of oligomers. For polyester filament fabrics can reduce "aurora", for short and medium fibers can improve fuzz pilling phenomenon.

2) The production of oligomers can be reduced and the dyeing depth can be obtained by controlling the dyeing temperature below 120℃ and using appropriate carrier dyeing method.

3) Adding disperse protective gum additives during dyeing can not only produce even dyeing effect, but also prevent oligomers from settling on the fabric.

4) After dyeing, the dye solution should be quickly discharged from the machine at high temperature for a maximum of 5 min. Because oligomers are evenly distributed in the dye solution when the temperature is 100 ~ 120℃, it is easy to accumulate and precipitate on the dye when the temperature is below 100℃, but some heavy fabrics are easy to form folds in this way.

5) Dyeing under alkaline conditions can effectively reduce the formation of oligomers and remove the remaining oil agent on the cloth surface, but dyes suitable for dyeing under alkaline conditions must be selected.

6) After staining, it was cleaned with reducing agent, 32.5% (380Be)NaOH 3-5ml /L, insurance powder 3-4g /L, treated at 70℃ for 30 min, and then washed cold, hot, cold, and neutralized with acetic acid.

For yarn white powder

1) The thorough method is high temperature drainage method

For example, the drain valve can be opened immediately after 130℃ constant temperature (120℃ is acceptable, but not lower, because 120℃ is the polyester glass conversion point).

Having said that, it seems very simple, in fact, the most important thing is that the safety problem is the most difficult: the sound and vibration of the machinery at the moment of high temperature drainage are very surprising, the aging machinery is easy to crack or loose screws, the mechanical cracking and dyeing machinery will explode (special attention) :

It is best to refit to the original machinery factory to design refit, not to casually play with life

There are two ways to discharge liquid into the tank and to the outside of the atmosphere. It is necessary to pay attention to the backwash phenomenon after discharge (experienced dyeing VAT manufacturing company is very clear).

High temperature drainage has the advantage of shortening dyeing but poor reproducibility of the plant is very troublesome

2) For plants that cannot drain liquid at high temperature, Oligomer detergent can be used to replace detergent in reduction cleaning projects, but the effect is not 100%

Wash the cylinder diligently after dyeing, and wash the cylinder once after about 5 cylinders of medium dark color.

If the current flow dyeing machine has a lot of white powder dirt, the first task is to wash the cylinder.