Polymer processing system including compression chamber and method for using same

Abstract

Polymer processing systems are provided including an extrusion assembly, a specially configured decompression chamber assembly, and a die assembly. Such systems are effective to provide shaped polymer products having reduced extrusion markings. Methods of using such systems are also provided.

1 . A decompression chamber assembly comprising: 
 an entrance block including a through aperture structured to pass a flowable extruded polymeric material;    a decompression chamber in communication with the entrance block and positioned to receive the flowable extruded polymeric material passed from the through aperture, the chamber having an outer wall defining a hollow space including an entrance zone generally adjacent the entrance block, a generally oppositely located exit zone and a central zone located therebetween, the hollow space having an increased cross-sectional area perpendicular to a central longitudinal axis of the hollow space at the central zone relative to at at least one of the entrance zone and the exit zone, the outer wall includes a first region defining increasing cross-sectional areas perpendicular to the central longitudinal axis of the hollow space and a second region, spaced apart from the first region, defining decreasing cross-sectional areas perpendicular to the central longitudinal axis of the hollow space, wherein at least a portion of each of the first region and the second region is oriented at an angle in a range of about 10° to about 40° relative to the central longitudinal axis of the hollow space; and    an exit block positioned to receive the flowable extruded polymeric material from the exit zone of the decompression chamber.    
   
   
       2 . The decompression chamber assembly of  claim 1  wherein the hollow space has an increased cross-sectional area perpendicular to the central longitudinal axis of the hollow space at the central zone relative to at both the entrance zone and the exit zone.  
   
   
       3 . The decompression chamber assembly of  claim 1  wherein the decompression chamber is structured to pass substantially all of the flowable extruded polymeric material entering the entrance zone out of the exit zone.  
   
   
       4 . The decompression chamber assembly of  claim 1  where the decompression chamber is free of any rotatable component.  
   
   
       5 . The decompression chamber assembly of  claim 1  wherein the decompression chamber is structured to cause the flowable extruded polymeric material to be under reduced strain and/or stress as the flowable extruded polymeric material passes through the decompression chamber.  
   
   
       6 . The decompression chamber assembly of  claim 1  wherein the decompression chamber is structured to reduce extrusion markings present in the flowable extruded polymeric material entering the decompression chamber.  
   
   
       7 . The decompression chamber assembly of  claim 1  wherein the outer wall is substantially smooth.  
   
   
       8 . The decompression chamber assembly of  claim 1  wherein the decompression chamber is in communication with no substantial source of suction.  
   
   
       9 . The decompression chamber assembly of  claim 2  wherein the cross-sectional area perpendicular to the central axis of the hollow space defined by the outer wall varies substantially continuously across the entire central zone.  
   
   
       10 . The decompression chamber assembly of  claim 1  wherein the decompression chamber includes no inner wall.  
   
   
       11 . A method of processing a polymeric material, which method comprises: 
 passing a flowable extruded polymeric material through a decompression chamber having an outer wall defining a hollow space, the hollow space including an entrance zone through which the flowable extruded polymeric material passes in entering the decompression chamber, a generally oppositely located exit zone through which the flowable extruded polymeric material passes in exiting the decompression chamber and a central zone located therebetween, the hollow space having an increased cross-sectional area perpendicular to a central longitudinal axis of the hollow space at the central zone relative to at at least one of the entrance zone or the exit zone.    
   
   
       12 . The method of  claim 11  wherein the passing step is effective to pass substantially all of the flowable extruded polymeric material entering the decompression chamber out of the decompression chamber.  
   
   
       13 . The method of  claim 12  wherein the cross-sectional area of the outer wall is varied so as to facilitate substantially all of the flowable extruded polymeric material entering the decompression chamber passing out of the decompression chamber.  
   
   
       14 . The method of  claim 11  wherein the hollow space has an increased cross-sectional area perpendicular a central longitudinal axis of the hollow space at the central zone relative to at both the entrance zone and the exit zone.  
   
   
       15 . The method of  claim 11  wherein the passing step is effective to relax the flowable extruded polymeric material in the decompression chamber.  
   
   
       16 . The method of  claim 11  wherein the passing step is effective to reduce extrusion markings present in the flowable extruded polymeric material entering the decompression chamber.  
   
   
       17 . The method of  claim 11  which further comprises: 
 extruding a polymeric material to form the flowable extruded polymeric material.    
   
   
       18 . The method of  claim 17  wherein the extruding step occurs in at least one screw extruder.  
   
   
       19 . The method of  claim 17  wherein the extruding step occurs in two or more screw extruders.  
   
   
       20 . The method of  claim 19  herein each screw extruder produces a ribbon of extruded polymeric material and the method further comprises combining the ribbons of extruded polymeric material into a combined ribbon of polymeric material.  
   
   
       21 . The method of  claim 11  which further comprises, after passing the flowable extruded polymeric material through the decompression chamber, passing the flowable extruded polymeric material through a die to form the flowable extruded polymeric material into a desired shape.  
   
   
       22 . The method of  claim 21  wherein the desired shape is a sheet.