| 摘要 |
339,550. I. G. Farbenindustrie Akt.- Ges. March 16, 1929. [Convention date]. Bleaching, processes and materials for.-Bast fibres, either in the form of crude fibre, spun yarn, or finished goods, are bleached by employing peroxide and hypochlorite baths in the following serial order :-1, peroxide; 2, chlorine (acid); 3, intermediate washing by infusion with sodium carbonate solution; 4, chlorine (alkaline or neutral); 5, peroxide. The first chlorine bath may consist of a bath containing free hypochlorous acid, preferably corresponding to PH < 5 , the second chlorine bath being of lower concentration in active chlorine and higher PH value. The first peroxide bath may consist of the spent peroxide of a previous fifth stage to which sodium carbonate has been added. As a modification in the case of fibres difficult to bleach, the second chlorine treatment is again performed in acid solution, and infusion with sodium carbonate is repeated before proceeding to the chlorine (alkaline or neutral) bath and the second peroxide bath. In an example, bath 1 contains 6 per cent sodium carbonate and a little waterglass, the temperature being maintained at 70‹ C., and bath 5 also contains a little waterglass, the temperature ranging from 40-80‹ C., rinsing being performed between the various stages. |
