Production of melt fused synthetic fibers using a spinneret

Abstract

A process and apparatus for the production of polyacrylontrile (PAN) polymer fibers from a polyacrylonitrile polymer, wherein a polyacrylonitrile polymer that comprises 90 weight percent or more polyacrylonitrile, optionally mixed with from about 30 to about 50 weight percent, based on the weight of the polymer, of a fugitive plasticizer, is heated, provided to an extruder in liquid form, extruded to form polyacrylonitrile fibers, and the fibers, immediately after the extrusion, are cooled, preferably in an air-cooled manifold, to a temperature of from about 110 to about 135° C. Fibers so produced have increased tensile strength, and thus are useful for more purposes, than typically produced polyacrylonitrile fibers.

What is claimed is:  
     
         1  In a process for the production of polyacrylonitrile fibers from a polyacrylonitrile polymer, wherein a polyacrylonitrile polymer that comprises 90 weight percent or more polyacrylonitrile, optionally mixed with from about 30 to about 50 weight percent, based on the weight of the polymer, of a fugitive plasticizer, is heated, provided to an extruder in liquid form, and extruded to form polyacrylonitrile fibers, the improvement comprising, 
 cooling the fibers, immediately after the extrusion, to a temperature of from about 110 to about 135° C.  
 
     
     
         2 . A process according to  claim 1  wherein the polyacrylonitrile polymer contains a chain extender-cross linking agent.  
     
     
         3 . A process according to  claim 1  wherein the fugitive plasticizer is ethylene carbonate.  
     
     
         4 . A process according to  claim 1  wherein the cooling is conducted at a temperature of about 120° C.  
     
     
         5 . A process according to claim to  claim 1 , further comprising carbonizing the polyacrylonitrile fibers.  
     
     
         6 . A process according to  claim 1  wherein the cooling is conducted in an air-cooled manifold that is attached to, and in flow connection with, the extruder.  
     
     
         7 . A process according to  claim 1  in which the cooling is conducted in a manifold that is attached to, and in flow connection with, the extrude, the manifold being cooled by a liquid cooling agent selected from water, oil, and specialty coolants.  
     
     
         8 . A process according to  claim 1  wherein the polyacrylonitrile polymer is produced by a melt fusion process.  
     
     
         9 . Apparatus for cooling polymeric fibers produced by extrusion, by indirect heat exchange with a cooling medium, comprising: 
 (a) a plurality of fiber inlet openings sized and arranged so as to match openings through which the fibers are extruded;    (b) a plurality of tubes connected to the plurality of fiber inlet openings, sized for passage of fibers therethrough;    (c) a shell surrounding the plurality of tubes;    (d) inlet and outlet means in the shell, for introducing thereto and removing therefrom a fluid heat exchange medium, whereby the fluid heat exchange medium is passed in indirect heat exchange with fibers passing through the plurality of tubes; and    (e) outlet means for removing fibers from the apparatus.    
     
     
         10 . Integrated apparatus for extruding fibers and for cooling the extruded fibers, comprising 
 (a) an extruding section wherein fibers are extruded from a liquid polymeric material introduced thereinto;    (b) a cooling section located directly below the extruding section for receiving and cooling the extruded fibers;    (c) inlet means in the cooling section for introducing extruded fibers thereinto;    (d) passage means for passing the fibers through the cooling section;    (e) a shell surrounding the passage means;    (f) inlet and outlet means in the shell, for introducing thereto and removing therefrom a fluid heat exchange medium, whereby the fluid heat exchange medium is passed in indirect heat exchange with fibers passing through the cooling section; and    (g) outlet means for removing the fibers from the cooling section.