| 摘要 |
Cellulose fibres are bleached by treating the fibres with active chlorine in aqueous solution followed by optional rising and centrifuging, and then subjecting them to the action of a calcium and magnesium sequestering agent, whereupon the fibres are again treated with chlorine, e.g. in a bath containing less active chlorine than the first. A "calcium and magnesium sequestering agent" is defined as an agent which gives rise to formation of complex negative ions including those metals so as to prevent precipitation of their salts from baths containing compounds which otherwise would insolubilise the alkaline earth metals present, e.g. alkali hexametaphosphates or sulphamates. The fibres may be bleached by treating them with active chlorine at a pH under 3, then with aqueous alkali hexametaphosphate or sulphamate to which sodium carbonate is added to bring the pH between 10.5 and 11.5, followed by aqueous active chlorine at a pH under 3, and are finally declorinated with aqueous sodium bisulphite at a pH of 8.5. The preferred temperature range at which all steps may be carried out is 15 DEG to 25 DEG C. |
