Lenzing Aktiengesellschaft

Chemiefaser Lenzing Aktiengesellschaft

Johann Kalleitner

Christian H Schlossnikl

Peter Gspaltl

Andreas Schweigart

Gerold Riedl

Heinrich Firgo

Klaus Weinrotter

Siegfried Baumann

Thomas Jeszenszky

The invention relates to a process for the manufacture of cellulosic flat films and cellulosic membranes in the form of flat membranes whereby a solution of cellulose in an aqueous tertiary amine oxide is moulded in film form using an extrusion nozzle which has an oblong extrusion gap and is led into a precipitation bath via an air gap whereby the cellulosic flat film is formed in the precipitation bath, characterized in that the cellulosic flat film is stretched in the transverse direction after entering the precipitation bath.

Process for the production of cellulosic moulded bodies

The invention relates to a process for the production of cellulosic moulded bodies in the form of flat or tubular films and cellulosic membranes in the form of flat or tubular films whereby a solution of cellulose in an aqueous tertiary amine oxide is extruded using an extrusion nozzle whereby the solution can as the case may be also contain additives such as stabilizing and softening agents, pore formers and so on whereby a moulded solution results which has two surfaces and the extruded moulded solution is led over a gap into a precipitation bath and drawn off from the precipitation bath. The process in accordance with the invention is characterized in that the two surfaces of the moulded solution in the gap are each exposed to at least one gaseous medium whereby the medium to which the first surface is exposed differs from the medium to which the second surface is exposed in composition, properties and/or the state of motion.

Non-flammable, high-temperature resistant polyimide fibers have irregularly lobed or serrated cross-sections, a wool-like smooth hand and high brightness. They are produced by a dry-spinning process which is carried out in a spinning column, wherein a 20 to 40% solution of the polyimide is spun from spinnerets having circular orifices, the orifice numbers ranging from 20 to 800 and the orifice diameters from 100 to 300 .mu.m. An extrusion speed of between 20 and 100 m/min, a take-up speed of between 100 and 800 m/min, an amount of spin gas between 40 and 100 m.sup.3 /h under standard conditions and a spin gas temperature of between 200.degree. and 350.degree. C. are applied. The tows leaving the spinning column, which contain residual solvent from 5 to 25% by weight--based on dry polymer--and have a single filament titer of between 3.5 and 35 dtex, are washed in hot water, then they are dried to a moisture content of less than 5%, subsequently are drawn at high temperatures and, if desired, are crimpled and cut into staple fibers.

Non-flammable, high-temperature resistant polyimide fibers made by a dry

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Schörfling, Austria

Johann Kalleitner