At present, there are about 600 types of dyes produced in China, which can meet more than 90% of the domestic market demand. Among various dyes, the top three in terms of production volume are dispersed dyes, reactive dyes, and sulfurized dyes, accounting for 46%, 32%, and 11% of the total output, respectively. In the second half of 2013, domestic dye prices skyrocketed, with an average price of 24000 yuan per ton for dispersed dyes and nearly 30000 yuan per ton for reactive dyes. This is mainly due to years of environmental governance, which has given domestic large enterprises more market discourse power.
During the production and processing of knitted fabric printing and dyeing, bubbles can cause the fabric to float on the water surface, and in severe cases, there may be fabric blockage (overflow jet dyeing machine). At this time, people often hope to use low foaming surfactants to meet the needs of various fast and efficient processes, so defoamers have become the preferred additives for technicians.
Defoamer is used to immerse organic compounds such as alcohol, ether and silicone oil into the surfactant foam and extend it to all directions, making the foam thinner and destroying gas— The directional molecular adsorption layer formed on the liquid surface (interface) until the foam bursts.
Previously, many printing and dyeing companies found irregular shaped oily substances on the surface of the fabric when it was taken out of the vat due to a lack of understanding of the dosage and performance of defoamers during operation. When encountering this phenomenon for the first time, it is difficult to figure out where so much oily substance comes from, because this oily substance (stained with what color, i.e. stained with what color of oily substance) adheres to the surface of the fabric very brightly, and when touched by hand, it penetrates into the fabric, but when taken, there are stains that cannot be completely removed. After multiple investigations, it was analyzed that the oil was caused by the demulsification of defoamers. Once the fabric is contaminated with this dirt, it is difficult to remove it completely. After multiple experiments, it was found that the larger the amount of defoamer used, the more severe this phenomenon becomes. Polyester cotton, pure polyester and other synthetic fabrics are more pronounced (while machines without defoamers do not exhibit this phenomenon). At the same time, it is also noted that the water quality in our factory is relatively hard, with a high concentration of metal ions such as Ca2+, Mg2+, Fe2+, etc. When the defoamer breaks the emulsion, the result will be oil separation, causing the oil to float in the dye solution and combine with the floating slag and dirt generated by metal ions, fibers, additives, and impurities in the dye, resulting in irregular color spots, color blocks, and oil stains adhering to the fabric. Therefore, while eliminating the foam, it also brings many adverse factors and negative effects, even economic losses.
