Development And Application Of Water Saving And Emission Reduction New Dyeing Technology For Polyester Fiber

Polyester fiber is the largest produced and the most widely used synthetic fiber.As the characteristics of tight structure, high hydrophobicity and so on, the strong hydrophobicity and low molecular weight disperse dyes was the only choice for dyeing of this fiber. As the strong hydrophobicity of the disperse dyes, after treatment including reduction clearing and washing were needed in order to remove the floating color adsorbed on the fiber surface after dyeing. Therefore, color fastness of the dyed product can meet the requirements. Water consumption of dyeing polyester fiber products was serious, and the emission of caustic soda and sodium hydrosulfite used in reduction clearing caused big trouble to the effluent treatment and environmental protection. Therefore, it is of great practical significance to develop a new process that possess the characteristic of no reduction clearing, low energy consumption and pollution emission for dyeing of polyester fiber with disperse dyes.In this investigation, without changing the original dyeing method and no transforming of the enterprise equipment, the water saving after treatment process of dyeing polyester fiber was investigated. This process was carried out as follow: the self-made special catalyst XBD and hydrogen peroxide（H₂O₂） was added to the dyeing bath directly after dyeing（dyeing bath was not released）, thus situ mineralization reaction among XBD, H₂O₂ and the residual dyes and dyeing auxiliaries in the dyeing bath was conducted, the organic composite was degraded to carbon dioxide（CO2） and water. The special catalyst XBD possesses the characteristic of certain hydrophobicity and it can adsorb on the surface of disperse dyes that in the dyeing bath or on the fiber surface. It has positive effect on catalyzing the hydrogen peroxide（H₂O₂） decomposition, thus degrading the dyes and dyeing auxiliaries. Therefore no reduction clearing and no washing can be reached and the water consumption of dyeing polyester fiber with disperse dyes can be reduced heavily. In this article, the mechanism of situ mineralization, influence factors of mineralization effect and properties of mineralized samples were investigated. The key factors such as the mineralization p H value, auxiliaries dosage, temperature and time was investigated and analyzed. And the optimum mineralization process parameters were set as follow: the dosage of mineralization accelerant A was 1.2%（owf）, the dosage of special catalyst XBD was 0.4×dyes amount（owf）, hydrogen peroxide（H₂O₂, the concentration of it was 30%） was 6.4×dyes amount（owf）（that is the moss ratio between H₂O₂ and XBDwas 16:1）, the mineralization p H value was 4-4.5, mineralization temperature was 80℃,and mineralization time was 40 min.The laboratory results show that: the color depth, color light and color fastness of the mineralized samples of polyester fiber dyed with disperse dyes was almost the same with the conventional after treatment process（reduction clearing, washing） samples. Thus the mineralization process was practicable. The production and application test of PET yarns,polyester knitted fabric and polyester top situ mineralization process was conducted at Saintyear holding group Co.,Ltd, Mingzhou Textile Co.,Ltd and Shandong Nanshan Fabrics & Garments Co., Ltd, respectively. The production results show that:the color（color depth and light） and fastness of the mineralized sample of polyester fiber products dyed with disperse dyes of the three different factory was almost the same with its corresponding conventional dyeing samples. When taking the mineralization process,water, steam and electricity consumption can be reduced 83.00%, 53.40% and24.00%,reapectively. And the efficiency can be improve 33.33%. At the same time, effluent chroma, CODcr of the effluent, BOD5 of the effluent, and suspended solids of the effluent were respectively reduced by88.05%, 51.65%, 27.42% and 40.74%. The production test showed that mineralization process of polyester fiber dyeing with disperse dyes possesses the characteristic of significant water saving and emission reduction, and it is a new technology that can be used for dyeing of polyester fiber in practical production.