Compostable or Biobased Foams

Abstract

The present invention describes compostable or biobased foams that are useful for fabricating foamed articles. The foams are produced using a compound comprising a compostable or biobased polyester and a blowing agent. Additives including plasticizers and chain extenders are optionally included in the compostable or biobased composition. These foams can be produced using conventional melt processing techniques, such as single and twin-screw extrusion processes. In one embodiment, foamed strand profiles are cooled and cut using conventional strand pelletizing equipment. In another embodiment, foamed beads are produced by cutting the foamed strand at the face of the extrusion die and the foamed bead or strand is subsequently cooled. The resulting compostable or biobased foamed bead has a specific gravity less than 0.15 g/cm 3 and the foam is compostable, as determined by ASTM D6400.

1 . A composition of matter, comprising:
 a compostable or biobased polymer melt processed with at least one blowing agent into an admixture wherein the blowing agent is injected into the melt and the admixture is extruded into foamed beads.   
     
     
         2 . The composition of  claim 1 , wherein said foamed beads have a density less than 0.3 g/cm 3 . 
     
     
         3 . The composition of  claim 1 , wherein said blowing agent comprises a physical blowing agent. 
     
     
         4 . The composition of  claim 1 , wherein said blowing agent comprises super critical CO 2 . 
     
     
         5 . The composition of  claim 1 , said compostable polymer comprising a polymer of polylactic acid. 
     
     
         6 . The composition of  claim 5 , wherein content of D-isomer in said polylactic acid polymer is less than 6%. 
     
     
         7 . The composition of  claim 5 , wherein content of D-isomer in said polylactic acid polymer is less than 2%. 
     
     
         8 . The composition of  claim 1 , further comprising a nucleating agent. 
     
     
         9 . The composition of  claim 1 , further comprising additives to improve melt rheology and viscosity. 
     
     
         10 . The composition of  claim 1 , further comprising additives selected from the group consisting of:
 antioxidants;   light stabilizers;   fibers;   foaming additives;   electrically conductive additives;   antiblocking agents;   antistatic agents;   heat stabilizers;   impact modifiers;   biocides;   compatibilizers;   tackifiers;   colorants;   coupling agents; and   pigments.   
     
     
         11 . The composition of  claim 1 , wherein the composition is produced from more than 50% compostable materials. 
     
     
         12 . The composition of  claim 1 , wherein the composition is produced from more than 80% compostable materials. 
     
     
         13 . The composition of  claim 1 , wherein the polymer is more than 50% biobased. 
     
     
         14 . The composition of  claim 1 , wherein the polymer is more than 80% biobased. 
     
     
         15 . The composition of  claim 1 , wherein said foamed bead has a substantially closed cell structure after pelletization of extrudate at the face of an extrusion die. 
     
     
         16 . The composition of  claim 14 , wherein said foamed bead has an average diameter of less than 10 mm. 
     
     
         17 . The composition of  claim 14 , wherein said foamed bead has an average diameter of less than 3 mm. 
     
     
         18 . The composition of  claim 14 , wherein said foamed bead has a spherical or nearly spherical shape. 
     
     
         19 . A composition of matter, comprising:
 an extrudate of a biobased or compostable polymer containing a blowing agent wherein the extrudate is of a viscosity and density suitable for forming a bead with a substantially closed cell structure.   
     
     
         20 . The composition of  claim 19 , wherein said foamed beads have a density less than 0.3 g/cm 3 . 
     
     
         21 . The composition of  claim 19 , wherein said blowing agent comprises a physical blowing agent. 
     
     
         22 . The composition of  claim 19 , wherein said blowing agent comprises super critical CO 2 . 
     
     
         23 . The composition of  claim 19 , said compostable polymer comprising a polymer of polylactic acid. 
     
     
         24 . The composition of  claim 19 , wherein said bead has an average diameter of less than 10 mm. 
     
     
         25 . The composition of  claim 19 , wherein said bead has an average diameter of less than 3 mm. 
     
     
         26 . The composition of  claim 19 , wherein said bead has a spherical or nearly spherical shape. 
     
     
         27 . The composition of  claim 19 , wherein said bead is capable of holding an internal pressure of gas in excess of ambient conditions within the closed cell structure of the foam.