Oxygen bleaching of pulp in the presence of high-silica protector
Реферат: 1519072 Oxygen bleaching silicate protected wood pulp POTLATCH CORP 9 Jan 1976 [18 Feb 1975] 00784/76 Heading D1P Cellulosic pulp is bleached by oxygen gas at elevated temperature and pressure in the presence of alkali and a cellulose protection comprising an alkali metal colloidal silicate having a molar ratio of silica to alkali metal oxide of at least 1.6 to 1. Preferably the silicate is sodium silicate and may be a water glass having a silica: sodium oxide molar ratio of 2:1 to 4:1 or a surface hydroxylated silica sol with a ratio of up to 100:1. Potassium silicate is also specified. The semi bleached product may be subject to one or more additional bleaching steps using chlorine, chlorine dioxide hypochlorite or peroxide. Preferably 0.1 to 0.4% by weight of the silicate, calculated as SiO 2 , is applied to a sulphate (kraft) soda or sulphite pulp of hard or soft wood. and consistency 8 to 30% by weight. Spent liquor may be recycled to reduce the amount of silicate to be added. The pulp is oxygen bleached for 10 to 80 minutes at 95 to 135‹C and 70 to 225 p.s.i. The pH at the end of this bleaching is 9 to 11. Brightness, viscosity deligrification and yield of the pulp are reported.
Oxygen bleaching of pulp in presence of high-silica protector
Номер патента: CA1062858A. Автор: James C. M. Hou. Владелец: Potlatch Corp. Дата публикации: 1979-09-25.