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/cm³ and the foam is compostable, as determined by ASTM D6400.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is based upon and claims benefit of copending and co-owned U.S. Provisional Patent Application Ser. No. 61 / 362,009 entitled “Biodegradable Foams”, filed with the U.S. Patent and Trademark Office on Jul. 7, 2010 by the inventors herein, the specification of which is incorporated herein by reference.BACKGROUND[0002]1. Field of the Invention[0003]This invention relates generally to compostable or biobased material compositions and to novel methods for producing lightweight, compostable or biobased foams and, in particular, to methods for producing foams using melt processing techniques to blend compostable or biobased materials and blowing agents that do not contain any volatile organic components (VOCs) such as pentane. The compositions and processes are useful for the production of a variety of products.[0004]2. Description of the Background[0005]Polymeric foams include a plurality of voids, also called cells, in a polymer ...

AI Technical Summary

Benefits of technology

[0029]“Nucleating agent” means a material that is added to a polymer melt that provide sites for crystal formation. For example, a higher degree of crystallinity and more uniform crystalline structure may be obtained by adding a nucleating agent.

[0030]“Chain Extender” means a material that when melt processed with a polymer, increases the molecular weight by reactively coupling chain ends.

Problems solved by technology

Pre-expanded beads that are not properly matured are sensitive to physical and thermal shock.

Molding of such beads before maturation may cause the cells within the particles to rupture, thereby producing an undesirable molded foam part.

Difficulties have been encountered in producing starch based polymers particularly by hot melt extrusion.

The molecular structure of the starch is adversely affected by the shear stresses and temperature conditions needed to plasticize the starch and pass it through an extrusion die.

Yet, while higher blowing agent levels can lead to smaller cells (a generally desirable result in the field of microcellular foams), according to conventional thought, higher blowing agent levels also can cause cell interconnection (which by definition increases cell size and can compromise structural and other material properties) and less-than-optimal surface properties (compromised surface properties at higher gas levels can result from the natural tendency of the blowing agent to diffuse out of the material).

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