Reactive dyes overflow dyeing machine, in order to promote dyeing, a lot of salt (sodium sulfate, table salt) is needed, a lot of sodium carbonate is needed for the sake of fixation, dyeing dark varieties such as black, navy blue, etc. the usage of sodium sulfate is up to 90% - l00 % (o.w.f), the usage of sodium carbonate is up to 20% to 25% (o.w.f) salt, alkali consumption amount is huge, if the amount of dark color product is about 20% at home, and calculate by 2 million tons of production per year, the salt consumption would be 2 million tons, the consumption of sodium carbonate would be a half million tons, add 80% dyeing products, the total consumption of salt, alkali are a surprising bigness, after dyeing a lot of water is needed for flushing, per ton cloth’s water consumption is l: 7-1:10, dyeing degree of reactive dyes is only 70% - 85%, large amount of sewage and high colority increased the difficulty and fees of sewage disposal.
The improvement of reactive dyes dyeing process that is been pushed at present, one is to use the substitution alkali (compound with high concentration of mixed alkali) instead of sodium carbonate, the amount is 1/5-1/6, it is easy cleaning after dyeing, the second is to use acid bifunctional soap detergent, combined the acid neutralization with soaping of the original process, after dyeing and three times washes, using acid neutralization and soaping directly, eliminating the separate acid neutralization, this process improvement can reduce 80% sodium carbonate, saving 10% water, saving electricity and time and is worth promoting and is worth of being generalized.
After the short liquor dyeing machine with excellent performance is been introduced, the liquor ratio of reactive dyes dyeing process can reach 1:4-1:5, which obviously reduces the consumption of dye and energy. The knitted fabric reactive dyes dyeing process and cold pad-batch dyeing which use no salt at all has already put into production in some factories in Guangdong province.
The present situation of the knitted fabric dyeing process is there exist differences between regions, and enterprises, some powerful dye house from the Pearl River Delta, Yangtze River Delta, Shandong province are well equipped with dyeing machine, advanced testing instruments, they use high quality dyestuff, the process design is reasonable, the success rate of one-off dyeing can reach more than 98%, some foreign knitting brand products are made orders processing production in those factories.
Some small and medium scale knitting dye houses in the north, Midwest are relatively backward due to the shortage of hardware and software, re-work rate is high, bath ratio is high up to1: 10, process time is long, the water consumption of per ton cloth can reach up to 1:150 -1:200, the products processed are low in grade, every year, there are some companies loss out.