A greener approach to cotton dyeings. Part 2: application of 1∶2 metal complex acid dyesPart 1 is ref. 1.

Further attempts were made to find a more environmentally friendly method of dyeing cotton as an alternative to standard reactive dyeing processes that require high levels of water, salt and alkali and produce high levels of effluent contamination.Pre-treatment with a polymeric cationic quaternary ammonium compound enabled dyeing of the fibre with 1∶2 (M∶L) metal complex acid dyes without salt at neutral/slightly acidic pH values. In comparison with standard reactive dyeing processes, both the time taken for the dyeing process to be completed and the volume of water required could be dramatically reduced. The dyeings secured using the pre-treatment method displayed high colour strength values, good to very good wash fastness and excellent light fastness.