Process for bleaching organic peroxyacid cooked material with an alkaline solution of hydrogen peroxide

摘要

PCT No. PCT/FI86/00028 Sec. 371 Date Nov. 17, 1986 Sec. 102(e) Date Nov. 17, 1986 PCT Filed Mar. 24, 1986 PCT Pub. No. WO86/05529 PCT Pub. Date Sep. 25, 1986.A lignocellulosic raw material is pulped with a cooking liquor containing organic peroxyacids, such as peroxyformic acid or peroxyacetic acid, and the defibered pulp is bleached with an alkaline solution containing hydrogen peroxide, the pH of which is at least 10 in the beginning of the treatment, and which is provided by adding to a sodium hydroxide solution, hydrogen peroxide in an amount which if calculated as a percent of the dry weight of the material coming to the treatment corresponds to from 0.20 to 0.80, preferably from 0.25 to 0.70 and most preferably from 0.45 to 0.65 times the kappa number of the pulp obtained from the previous stage of the process.