Abstract: The invention relates to a process for the manufacture of cellulosic flat films and of cellulosic membranes in the form of flat membranes whereby a solution of cellulose in an aqueous tertiary amine oxide is extruded by means of an extrusion nozzle, which has an extrusion gap, whereby the solution is shaped in the form of a film and the solution is led into a precipitation bath via an air gap and is characterized in that an extrusion nozzle is used which has an extrusion gap with a minimum length of 40 cm.

Abstract: The invention relates to a process for producing a strengthened fiber assembly containing cellulosic fibers with the cellulose being present in the crystalline structure of cellulose II, by contacting the fiber assembly with an aqueous solution of N-methylmorpholine-N-oxide (NMMO) at elevated temperature and subsequently washing the fiber assembly, characterized in that contacting is effected in a manner that from the relation-947+0.30.times.log.sub.(10) t+0.046.times.T-3.53.times.C +645.times.log.sub.(10) Cwherein t indicates the time in minutes during which the fiber assembly is contacted with the aqueous NMMO solution, T indicates the temperature of the aqueous NMMO solution in .degree.C. and C is the concentration of NMMO in % by mass, based on the aqueous NMMO solution, a number in the range of 0.30 to 1.70 results with the proviso that the temperature T is smaller than 130.degree. C. and the concentration C ranges between 70 and 84 % by mass.

Abstract: The invention is concerned with a cellulose sponge which may be produced by mixing a solution of cellulose in an aqueous tertiary amine-oxide with a pore forming agent and a sponging agent and subsequently exposing it to conditions which cause a decomposition of the sponging agent and a foaming of the cellulose solution, whereafter the foamed cellulose is contacted with water to precipitate the cellulose.