Dye printing not only increases the added value of printed products, but also serves as a primary means of expanding into international markets. However, the most effective way to treat printing wastewater in China is still stuck
The lack of fundamental solutions in reducing emissions and improving sewage treatment technology has greatly hindered the sustainable development of China's printing industry. Many countries are gradually switching to pigment printing in order to reduce the pollution of printing and dyeing wastewater on the environment and ecology. But there is still a significant difference in the final effect of the fabric after pigment printing and dye printing. From the perspective of visual aesthetics in pattern design alone, the color beauty and material beauty presented by dye printing in the interaction with fabrics, as well as the spatial color mixing and spirituality presented by clothing and decorations placed in different environments, are incomparable to the colors of pigments in pigment printing. Therefore, it is particularly necessary to research and develop environmentally friendly dye printing technology.
This article will compare the advantages and disadvantages of the conventional dispersed dye printing process used by Chinese printing enterprises to this day, and explore the non steam washing process of dispersed dye printing and the shortcomings that still exist in its implementation. The aim is to inspire experts who are interested in the printing industry to work together to overcome difficulties and create new achievements for China's printing industry.
Advantages and disadvantages of conventional dispersed dye printing
The advantages of using dispersed dyes for printing products in printing enterprises now are: mature screen printing technology, easy operation, and low cost. Especially for printed products, their colors are bright, transparent, elegant, and luxurious. Deep and light colors can be freely matched according to the design requirements of the pattern designer, with complete color spectrum and soft and smooth feel. And a series of auxiliary processes around dispersed dye printing have become quite mature and very stable.
The disadvantage is that during the printing process, the dispersed dye paste needs to be steamed to produce color, and the dispersed dye and paste that have not entered the fabric fibers are washed away through the washing process. Therefore, a large amount of dye color water and wastewater containing paste and additives will be discharged during the washing process, which will cause serious damage to the ecological environment. According to authoritative data released by the Ministry of Industry and Information Technology of the People's Republic of China, the comprehensive water consumption during the processing of cotton, linen, synthetic fibers, and blended fabrics in existing printing and dyeing enterprises is 250 tons for every 10000 meters of processing. 100% of the wastewater must undergo sewage treatment to meet the standards before being discharged. This number is shocking. However, the current effective measures are only limited to emission reduction and post-treatment of sewage, and the problem has not been effectively eradicated.
2. The origin of non steamed printing ink
The conventional process for coloring dispersed dyes involves steaming at a temperature of 170-178 ℃ and steaming for 7-8 minutes. A large number of experiments have shown that when using dispersed dyes and environmentally friendly printing non steam washing slurry in proportion, printing can be completed directly in the setting without the need for steaming. The coloring effect is the same as the color after steaming. Directly producing color from the shaping machine is called non steaming. By using this printing method, the color fastness of dispersed dyes on synthetic fabrics can meet the requirements of conventional printing. There is no floating color overflow during water washing. Even if the style of the printed fabric needs to be changed through deep processing to improve the hand feel, there will be no floating color overflow during subsequent immersion and soaking, which can be exempted from water washing. Therefore, the printing ink made by compounding dispersed dyes with the above-mentioned specialized paste is called non steam washing ink.
3 Disperse dye non steam wash printing
The printing of dispersed dyes using non steam washing paste simplifies the process that printing factories have been following to this day, which involves "pre shaping the printed fabric, screen printing, steaming, washing, shaping, finishing, packaging, and printing finished products", into the process of "screen printing, steaming, shaping, finishing, packaging, and printing finished products". On thick fabrics, the screen printing paste has good fluidity, clear pattern edges, no clogging, good color development, and easy operation, greatly improving the printing quality rate. After printing with non steam washing paste, there is no need to steam the color, as long as the color is synchronized with the fabric setting. The significant feature of printing with non steam washing slurry is that there will be no color water overflow of dispersed dyes during water washing. Thus, it truly achieves the blockage of the discharge of colored water and sewage from the source. As stated in the report on the non steaming and washing project, "dye printing can eliminate steaming and washing steps, reduce fabric defects, fundamentally solve environmental problems, and eliminate the pollution of wastewater to the environment. From this, it can be seen that this move not only simplifies the complex traditional printing process, but also saves a lot of capital investment and daily expenses such as maintenance and repair of related equipment.
4 Disadvantages of Non Steam Wash Printing with Disperse Dyes
Although the dispersed dye non steam washing printing technology currently has good printing effects on thick synthetic fabrics and thick blended fabrics, especially for single color printing on white and light colored backgrounds, there is still a problem of hard hand feel on thin fabrics (such as chiffon). There is still a long way to go to truly overcome and solve the hand feel problem after printing on lightweight synthetic fabrics using non steam wash pulp printing with dispersed dyes. It is necessary to conduct extensive research and repeated experiments in conjunction with universities, professional research institutions, printing materials, and printing enterprises. However, the author firmly believes that with the advancement of China's scientific and technological level, the problem will be effectively solved.
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