Bleaching cellulose material esp. cotton with peracetic acid in acid soln. - without activator to increase whiteness and reduce waste liquor pollution

摘要

Bleaching cellulosic materials or cellulose, esp. cotton, is carried out with peracetic acid (I) soln. with pH 1-4, without using activators. Pref. bleaching is carried out at pH 2-3.5 and 30-60, esp. 45-55 deg. C for 15-120, esp. 30-60 min.. An aq. soln. contg. 0.5-10, esp. 2-8 (wt.)% (I) is used. Bleaching pref. is accompanied by ultrasonic treatment at 20-50, esp. ca. 35 kHz with a power of 0.2-4, esp.0.5-2 W/cm2. The goods/liquor ratio is ca. 1:8 to 1:50. Bleaching may also be carried out by slop padding with 80-180% pick-up, using liquor contg. 0.05-2% (I), followed by a dwell of 2-8 h at room temp., 15-120 min. at 30-60, esp. 45-55 deg C or 2-15 min. at 80-160 deg. C, pref. in satd. steam. The bleached material is treated in an alkaline liquor, esp. with pH 8-11, and then dyed or treated with alkali and dyed in the same liquor. USE/ADVANTAGE - The deg. of whiteness is much better than that obtd. with (I) at pH 5-7 and no activators, stabilisers, complexing agents or corrosion inhibitors are needed. The spent bleach contains few impurities and has a much higher pH, so that it can easily be neutralised with spent alkaline liquor from cotton finishing, which also decomposes the residual peroxide, with O2 formation