METHOD FOR PRODUCING A TYPE OF PULP

Before boiling, the starting material is steam-treated. The cellulose obtained by boiling is subjected to cold alkali extraction, during further treatment. Steam treatment takes place at 120[deg]C or more, at a P factor of 50 or less. Medium pressure steam at 150[deg]C - 180[deg]C is employed. Before boiling, the raw material is impregnated. Impregnation and steam treatment take place in the same boiler in a continuous batch boiling process. Part of the press lye arising during cold alkali extraction, is purified by membrane filtration, especially by nano- or ultrafiltration. Between the two separation stages, the retentate of the first stage is diluted with water. From part of the retentate of the membrane separation stage, the hemicelluloses contained, especially xylanes, are recovered. For precipitation reversal, mineral acids, CO 2 and mono- or multivalent alcohols are used. Recovered xylanes are further processed to xylo-oligosaccharides by hydro-thermolysis or enzymatic hydrolysis. The process is coupled with manufacture of paper cellulose. A fraction of the press lye recovered from cold alkali extraction and/or a fraction of the retentate of a membrane filtration process carried out on the press lye, is added to the boiling lye of a boiling process for paper cellulose manufacture. Cellulose from boiling is subjected to the common bleaching process and to a treatment adjusting the degree of polymerization. This comprises oxidative bleaching, acid hydrolysis and electron beam irradiation, for the latter of which, conditions are detailed. An alkali peroxide treatment is employed. Boiling is carried out in two stages, as claimed in , a closely-associated disclosure. Properties of fibers manufactured from the cellulose are quantified. An independent claim is included for lyocell- and viscose fibers produced by spinning the chemical cellulose material.