Remedies:

• Proper viscosity of print paste. Guar gum and its percentage with proper cooking method will eliminate the splashing problem. A gum paste having higher solid content and certain plasticity is recommended
• Fabric should be free from auxiliaries like size, coning oil, non-ionic emulsifiers and cotton impurities, to eliminate the problem of yellowing and uneven prints of printed fabric
• Selecting suitable thickener, moderate strength of the dyestuffs, appropriate dosage and small motifs in printing excludes bleeding. Low viscosity of paste may cause bleeding
• Tone change can be eliminated by uniform heating and quick drying. Auxiliaries, like print developer TX, have a synergistic action on the different types of dyes used in mixing and brings about synchronization of diffusion rates of individual dyes
• Hallowing/ mark off can be negated by selecting proper dyes and good quality wrapper (cotton wrapper) for pressure aging
• Colour value change can be barred by maintaining appropriate pH of 5-6. Compatibility of dyes i.e. having diffusion temperature in the same range is selected. Use of sequestering agent in print paste is important or else usage of soft water is emphasized
• After-treatment staining is reduced by following the sequence of: Cold wash Reduction Hot water Soaping ClearingRinsing
• Using a good auxiliary like catalyst PC helps in removal and destroying unfixed superfluous disperse dyes and also helps in breaking baked-dried film of printing gum faster

Washing

Good printing can be spoiled by bad or improper washing techniques. Essentially, the best washing sequence has to follow the following steps:

• Soak the printed fabric well to swell the gum of the print paste for easy removal
• Remove the swollen gum by an efficient washing arrangement in the open soaper or winches
• Continue washing in 2-3 compartments in cold and agitating conditions, till the wash water is free from contaminated colours
• Add 2-3gpl of good quality detergent with dispersing functions-0.5-1gpl caustic soda, 1-2gpl sodium hydrosulphite-to remove all unfixed dyestuffs efficiently
• Treatment with 2-3gpl detergent and 1-2gpl of soda ash at boil, in two compartments followed by drying in drying ranges after hot wash.

References

1. ND Iyer, 'Polyester the most versatile synthetic fibre', Colourage, September '01 to February '04 (series of 26 articles)
2. AK Samnta, 'Road map for wet processing of micro denier polyester fabric and relevant studies on its dyeability', Man Made Textiles, October '03
3. Dr Bharat Desai, 'Oligomer control in polyester fibre processing', Colourage June 05
4. Prof VA Shenai, 'Technology of dyeing'
5. Mr CN Sivaramkrishnan, 'Dispersing Agent', Colourage, September '05
6. AD Sule, 'Practical Problems in dyeing of polyester off shades', Man Made Textiles, December 03
7. Search engine "google.com"

The author is associated with Resil Chemicals, Ahmedabad

Problems and Their Remedies in Polyester Processing-Part III