Sometimes the fabric surface of the finished product of the vat dyed fabric will have some stains or spots. The main reasons are the following aspects:
1. The chemical raw materials are not uniform enough: like the paint for painting, if the temperature is low in winter, it will be simple to condense and not simply scratch. Therefore, it must be stirred evenly at a certain temperature, and it is better to filter out large particles of impurities.
2. The problem of natural-color cotton: If there is no problem with the coloring, but the natural-color cotton has a problem, it will also cause stains. For example: if there are impurities on the cloth surface, it will cause uneven coloring if it is not cleaned. If the natural-colored cotton cloth itself has colored yarn, it is useless to color evenly. It is very much a matter of the pH of the cloth surface. Pay attention to the amount of caustic soda in the pre-treatment, too much or too little will damage the natural cotton cloth. If the part is over-treated with caustic soda, the color may become darker. The amount used will depend on the specific fabric.
3. Water used for coloring: Water is very important. The quality of water and the content of metal ions have a considerable influence on printing and dyeing, and the influence of iron ions in metal ions is greater.
4. Coloring heating speed control: the speed of coloring heating rising too fast will also cause stains on the fabric.
5. Improper use of coloring auxiliaries: The more auxiliaries are not the better, but the proper amount. A simple example: some softeners are not resistant to high temperatures. If used at high temperatures, they will inevitably cause demulsification and agglomeration to form color stains, which appear as oily spots and uneven color patches. In addition, the low temperature (not exceeding 40°C) silicone oil added in the vat dyeing, or the cationic softener is not cleaned, will also affect the color of the next vat.
6. The compatibility of dyestuffs.
7. The quality of dyes is poor. Some manufacturers are blindly pursuing cost reduction and use dyes with weak dispersibility or do not use levelling agents with good dispersing power. The quality cannot be guaranteed.