It is relatively common to have doubts about oligomer staining, which seriously affects product quality, and at the same time causes contamination to equipment, making it difficult to clean. Here is a summary of the problem:

Oligomer, also known as oligomer, oligomer, short polymer

It is a low-molecular substance with the same chemical structure as polyester fiber that exists inside polyester fiber. It is a by-product in the polyester spinning process. Generally, polyester contains 1% to 3% oligomers.

Oligomers are polymers composed of fewer repeating units, and their relative molecular mass is between small molecules and high molecules. Its English name "oligomer" prefix oligo comes from the Greek ολιγος, meaning "some". Most polyester oligomers are cyclic compounds formed by three ethyl terephthalates.

Influence

Color spots and stains on the cloth surface; white powder produced by yarn dyeing

When the temperature exceeds 120°C, the oligomer can dissolve in the dye bath and crystallize out of the solution, combining with the condensed dye. When it cools, it deposits on the surface of machinery or fabrics to form defects such as stains and spots. The disperse dyeing is generally kept at 130°C for about 30 minutes to ensure the depth and fastness of the dyeing. Therefore, as a solution, light colors can be kept at 120°C for 30 minutes, and dark colors must be pre-treated before dyeing. In addition, dyeing under alkaline conditions is also an effective method to solve oligomers.

Comprehensive measures

1) The gray cloth uses 100% NaOH3% before dyeing. Surface active detergent l%. Treated at 130°C for 60 minutes, bath ratio l:10~l:15, the pre-dyeing treatment method has a certain erosion effect on polyester fibers, but it is extremely beneficial to the removal of oligomers. For polyester filament fabrics, it can reduce "aurora", and for short and medium fibers, it can improve the pilling phenomenon.

2) Control the dyeing temperature below 120°C, and adopt appropriate carrier dyeing method to reduce the generation of oligomers and obtain the same dyeing depth.

3) Adding dispersing protective colloid additives during dyeing can not only produce level dyeing effect, but also prevent oligomers from precipitating on the fabric.

4) After dyeing, drain the dye solution out of the machine rapidly at high temperature, and the drainage time is at most 5 minutes. Because oligomers are evenly distributed in the dyeing solution at a temperature of 100-120°C, when the temperature is below 100°C, they are easy to accumulate and precipitate on the dyed matter, but some heavy fabrics are prone to wrinkles.

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

6) Wash with reducing agent after dyeing, add 32.5% (380Be) NaOH 3-5ml/L, sodium bicarbonate 3-4g/L, treat at 70°C for 30 min, then wash cold, hot, cold, and neutralize with acetic acid .

For yarn whitening

1) The thorough method is the high temperature drainage method

For example, after the constant temperature of 130°C, open the drain valve immediately to complete (120°C is also possible, but it cannot be lowered, because 120°C is the conversion point of polyester glass)

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

Wash the vat frequently after dyeing, and wash the vat once after about 5 vats of medium-dark color.