What are the common problems encountered when fabric softening?

1. Alkaline problem

The pre-treatment of cotton fabrics usually requires a higher concentration of alkali treatment to remove fabric impurities (especially a larger amount of mercerizing alkali). It is not easy to wash the alkali into the fiber. When dyeing (reactive vat dyes), alkali should also be added. The cloth surface may be alkaline during finishing. Chemical fiber fabrics must undergo reduction cleaning after dyeing. At present, printing and dyeing factories are still using sodium hydroxide and caustic soda for cleaning. If the subsequent cleaning is not clean, it will also cause alkali on the cloth surface before softening. Ordinary silicone oil is not alkali resistant and will break under alkaline conditions. This is the reason why the factory sticks to the roll after passing several kilometers when it is soft. Therefore, the cloth surface must be cleaned with alkaline agent or added with acetic acid in the working fluid before softening to maintain the PH5-6 of the rolling tank.

Most of the dyes and brighteners used in cotton are anionic, while the whitening of cotton is basically done on the setting machine. In addition, when the color of the dyed fabric is not correct, the color needs to be fine-tuned. The color correction is usually added with a small amount of dye or paint when applying the soft finishing agent. The factory generally uses ordinary silicone oil (weak cation) to cause anion and cation charge attraction reaction, causing condensation and sticking to the roller , And the softness of the anionic silicone oil does not meet the requirements, causing confusion in the factory. The charge uniformity must be considered during processing.

2. Temperature problem

The cloth dyed by the long cotton car must be dried in a drying cylinder, and then packed in a large package or stacked in a cloth box. If it is not sufficiently cooled, especially the cloth in a large package, the surface temperature of the fabric may be higher when it is soft. This causes the temperature of the working fluid in the rolling groove to rise (especially in summer), sometimes reaching above 60°C, and when the heat resistance of ordinary silicone oil is not good, it can also cause sticking of the roll. It is better that the temperature in the rolling groove does not exceed 40 ℃.

3. Yellowing problem

A long time of shutdown during operation causes the fabric to stay yellow and the amino hydrogen of the amino silicone oil is easily oxidized by air to form a chromophore, which turns yellow. The product turns brown, and brown makes the white fabric look like it has lost its most basic white or simply turned yellow. The pH is too high, and the temperature is too high during drying, and the accompanying substances of the cotton fabric turn yellow. Strengthen process control. Storage is yellowing. Caused by contaminated gas in storage.