FAS BLEACHING
The invention relates to lignin-preserving bleaching of lignocellulosic primary fibres produced by the action of sulfites, by means of formamidine sulfinic acid (FAS). The invention also relates to a bleached primary fibrous material consisting of lignocellulosic material produced by the action of sulfites. Primary fibrous material consisting of coniferous wood has a lignin content of at least 15 % in relation to other fibrous materials and a breaking length of at least 7 km at 20°SR, and primary fibrous material consisting of deciduous wood has a lignin content of at least 15% in relation to other fibrous materials and a breaking length of at least 6 km at 30°SR.