Hollow strandfoam and preparation thereof

Abstract

Prepare a foam structure that includes hollow coalesced foam strands and, optionally, solid coalesced foam strands using an extrusion die block equipped with apertures that promote forming the hollow strands and, optionally, the solid foam strands.

1 . An extrusion die for processing foamable polymer compositions, the die comprising a solid body having a first major planar surface and a spaced apart, substantially parallel second major planar surface, the body having defined therein a molten polymer receiving cavity having an open end where it intersects the second major planar surface and a closed end disposed between the first and second major planar surfaces, the first major planar surface having defined therein at least two sets of first apertures that are in fluid communication with the molten polymer receiving cavity and the first major planar surface, each first aperture set being spaced apart from other first aperture sets with each aperture of a set having a shape that forms a segment of a complete, hollow geometric shape and all apertures in a single set being spaced apart from each other, but arranged in a manner sufficient to approximate the complete geometric shape.  
   
   
       2 . The die of  claim 1 , further comprising at least two second apertures, the second apertures being defined in the first major planar surface and in fluid communication with the molten polymer receiving cavity, the second apertures also being spaced apart from the sets of first apertures.  
   
   
       3 . The die of  claim 2 , further comprising a plurality of third apertures, the third apertures being defined in the first major planar surface and in fluid communication with both a source of a fluid medium, blowing agent or other component and the first major planar surface, each third aperture being defined in said first major planar surface at a point within the complete hollow geometric shape formed by a first aperture set of the die embodied in  FIG. 2  or that end of the pin furthest from the closed end of the cavity defined in the first body segment, whichever is appropriate.  
   
   
       4 . A two piece extrusion die for processing foamable polymer compositions, the die comprising a first solid body segment and a second solid body segment; the first solid body segment having a first major planar surface and a spaced apart, substantially parallel second major planar surface, the first body segment having defined therein a foamable composition receiving and distribution cavity, the cavity having an open end where it intersects the second major planar surface and a closed end disposed between the first and second major planar surfaces, the first body segment also having attached thereto a plurality of pins that begin at the closed end of the cavity and extend beyond the open end of the cavity; the second body segment having a first major planar surface and a spaced apart, substantially parallel second major planar surface, the second body segment having defined therein a plurality of spaced apart first apertures that are in fluid communication with both the first and second major planar surfaces; the first and second solid body segments, when assembled with the second major planar surface of the first segment proximate to the first major planar surface of the second segment, cooperating to provide a plurality of die gaps, the die gaps being formed by combinations of pins from the first body segment and the first apertures of the second body segment, the die gaps providing a fluid flow path from the foamable composition receiving and distribution cavity to the second major planar surface of the second segment.  
   
   
       5 . The die of  claim 4 , further comprising at least two second apertures, the second apertures being defined in the second die segment and in fluid communication with both major planar surfaces of said second die segment, the second apertures being spaced apart from the first apertures.  
   
   
       6 . The die of  claim 4 , further comprising a plurality of third apertures, each third aperture being defined in a pin in such a manner as to be in fluid communication with both that end of the pin proximate to the second major planar surface of the second segment and a source of a fluid medium, blowing agent or other component and the first major planar surface.