Flow Chart of Reduction Cleaning in Polyester Dyeing

Reduction Cleaning:

Reduction cleaning is used for destroying and removing the dispersed dye deposited on polyester fiber. Because of large wastage of water, energy, and time due to the rinses necessary to remove the reducing agent. Highly polluting due to the high conductivity and COD values produced. Reduction clearing is done in polyester fabric dyeing. Here flowchart of reduction cleaning or clearing in polyester dyeing is given below.

Reduction Cleaning in Polyester Dyeing
Flow Chart of Reduction Cleaning/Clearing in Polyester Dyeing

Reduction clearing chemical is added at 800C & run for 30 min.


Water filling

Acetic Acid is added at 800C & run for 30 min


Washing is done

Unload the fabric 

In the conventional process reduction clearing process is done separately after polyester part dyeing which consumes a substantial volume of water, chemicals, process time. Thus requiring expanded production cost. Nowadays dyers and producers and remarkably well concerned regarding the eco-friendly and efficient technical processes due to increased pressure and demand claimed by the buyers and end-users. As the adequate water resources are gradually diminishing alarmingly, all manufacturing plants including textile wet processing industries are trying to best use the water by imparting process modifications due to environmental and commercial concerns as well.

Reduction clearing is done after polyester part dyeing to remove the unfixed dyes and auxiliaries from the fabric surface required for quality assurance. For medium to dark shade, reduction clearing is done using a commercially available reducing agent in 2 gm /ltr at 800C for 30 minutes typically. In case of dark to extra dark shade reduction clearing may need to be done twice. Hence reduction clearing process takes 1-2 hrs. approximately. NaOH and Na2S2O4 are also extensively used as a reducing agent after polyester part dyeing. As mentioned earlier that NaOH and H2O2 are used as scouring and bleaching agents respectively can play the role of reduction clearing as well if the pre-treatment process is done after polyester part dyeing keeping all quality parameters maintained.

Author of this Article:
 Rana Sohel 
Executive Engineer 
Sunman Textile Mills Ltd. Chittagong 
Cell: +8801912-420118 
Email: [email protected]

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