Process for the production of cellulosic flat films

Abstract

The invention relates to a process for the production of cellulosic flat films whereby a solution of cellulose is extruded in an aqueous tertiary amine oxide by means of an extrusion die which has an extrusion gap whereby the solution is moulded in the shape of a film and the extruded solution is led via an air gap to a precipitation bath. The process in accordance with the invention is characterised in that an extrusion die is used which has an extrusion gap b of 220 μm≦b≦280 μm. Moreover, the invention relates to flat films, obtainable by the amine oxide process with a thickness d of less than 20 μm, a width B of more than 30 cm, and a factor f of 65 or less, whereby f is defined as f=d*(MD/TD), d is used in μm and whereby MD stands for the tenacity of the film in the longitudinal direction (N/mm 2 ) and TD for the tenacity of the film in the transverse direction (N/mm 2 ).

1 . Process for the production of cellulosic flat films whereby a solution of cellulose in an aqueous tertiary amine oxide is extruded by means of an extrusion die, which has an extrusion gap, whereby the solution is shaped in the form of a film, and the extruded solution is led via an air gap into a precipitation bath characterised in that an extrusion die is used which has an extrusion gap with a width b of 220 μm≦b≦280 μm.  
     
     
         2 . Process according to  claim 1 , characterised in that the width b of the extrusion gap is 240 μm≦b≦260 μm.  
     
     
         3 . Process according to  claim 1  or  2 , characterised in that the extrusion gap has a length l of 40 cm≦1.  
     
     
         4 . Monoaxially stretched cellulosic flat film obtainable by the amine oxide process with a thickness d of less than 20 μm, a width B of more than 30 cm, and a factor f of 65 or less whereby f is defined as f=d*(MD/TD), d is used in μm and whereby MD stands for the tenacity of the film in the longitudinal direction (N/mm 2 ) and TD stands for the tenacity of the film in the transverse direction (N/mm 2 ).