Pre-treatment of cellulosics: An insight review - Part 2

摘要

1.Preparation processes are a most critical stage of textile finishing activities. 2. The quality of cotton has consistently changed within the last few years, a fact which has increased the problems with which finishers are confronted. The content of alkaline earths, for instance, has doubled. 3. Upto 20% of impurities, including sizing agents and fibre admixtures, have to be removed during the stage of preparation. 4. The first preparation process is desizing which is usually achieved with the assistance of enzymes. 5. It is possible to continuously desize the goods, followed by a reaction time, or by a pad-steam process. 6. The pad-batch process permits complete removal of the sizing agents, whereas comparatively long reaction times are required. 7. The pad-steam process, on the other hand, gives rise to a certain amount of swelling, imparting the good absorbency ratings already at this stage. The drawback of this option is to be seen in relatively high investments. 8. If oxidative desizing agents are employed, desizing can be combined with the alkaline processing stage. 9. Mill-integrated finishing divisions have recently shown an increased tendency to recycle water-soluble sizing agents (polyvinyl alcohols, carboxymethylcellulose). Yields of 50% can only be achieved by washing out with a volume of water that can be used for subsequent sizing processes. In the case of higher water volumes, and if the liquor is subsequently subjected to ultrafiltration, the yield can be increased to over 90%. 10. The stage of alkali treatment is an important swelling and extraction process for the removal of fibre admixtures with optional results of 4%. 11. Most effective boiling off auxiliaries are sufficiently stable surfactants, if required combined with oxidative desizing agents.