Process for producing cellulosic tubular films

Abstract

The invention relates to a device for the production of cellulosic tubular films by extruding a solution of cellulose in an aqueous tertiary amine oxide into a precipitant present below the device, which device comprises an extrusion die having a substantially annular extrusion gap, wherein a supply duct for precipitant and a discharge duct for used precipitant are provided in the interior of the ring formed by the extrusion gap, characterized in that the supply duct ( 3 ) for the precipitant terminates below the discharge duct ( 4 ) for the used precipitant.

What we claim is:  
     
         1 . In a device for producing cellulosic tubular films by extruding a solution of cellulose in an aqueous tertiary amine oxide into a precipitant provided below said device, of the type including 
 an extrusion die having a substantially annular extrusion gap constituting a ring,    a supply duct for said precipitant and a discharge duct for used precipitant each provided in the interior of said ring formed by said extrusion gap,    the improvement wherein said supply duct for said precipitant terminates below said discharge duct for used precipitant.    
     
     
         2 . A device as set forth in  claim 1 , further comprising a spacer provided below said extrusion gap.  
     
     
         3 . A device as set forth in  claim 2 , wherein said spacer is designed to have a substantially circular periphery.  
     
     
         4 . A device as set forth in  claim 2 , wherein said spacer has a cross sectional area larger than the area formed by said ring constituted by said extrusion gap.  
     
     
         5 . A device as set forth in  claim 2 , wherein said spacer is designed to have a cross sectional area capable of being changed.  
     
     
         6 . In a process for producing cellulosic tubular films, including the steps of 
 preparing a solution of cellulose in an aqueous tertiary amine oxide,    providing a device including an extrusion die having a substantially annular extrusion gap constituting a ring and a precipitant supply duct constructed to supply a precipitant as well as a used precipitant discharge duct constructed to discharge used precipitant each provided within said ring with said precipitant supply duct terminating below said used precipitant discharge duct,    extruding said solution of cellulose in an aqueous tertiary amine oxide through said substantially annular extrusion gap of said extrusion die so as to obtain a tubularly molded solution,    providing a precipitation bath containing said precipitant below said device, and    transporting said tubularly molded solution in a transport direction into said precipitation bath so as to be contacted by said precipitant both on its inner side and on its outer side thereby causing said cellulose to precipitate and a tubular film to be formed,    the improvement wherein said precipitant contacting said tubularly molded solution on its inner side contains dissolved tertiary amine oxide whose concentration decreases in said transport direction of said tubularly molded solution.    
     
     
         7 . A process as set forth in  claim 6 , wherein said tubularly molded solution is stretched in said transport direction.  
     
     
         8 . A process as set forth in  claim 6 , wherein said tubularly molded solution is stretched transverse to said transport direction.  
     
     
         9 . A process as set forth in  claim 8 , wherein said tubularly molded solution is stretched transverse to said transport direction by aid of hydrostatic pressure.  
     
     
         10 . A process as set forth in  claim 8 , wherein said tubularly molded solution is stretched transverse to said transport direction by aid of gas pressure.  
     
     
         11 . A process as set forth in  claim 8 , wherein a spacer is provided for stretching said tubularly molded solution transverse to said transport direction.  
     
     
         12 . A process as set forth in  claim 6 , further comprising drying said tubular film formed by precipitating said cellulose after transportation through said precipitation bath while keeping said tubular film under tension so as to prevent shrinking.  
     
     
         13 . A process as set forth in  claim 6 , wherein said tertiary amine oxide is N-methylmorpholine-N-oxide.