Resilient biodegradable packaging materials

Abstract

Biodegradable starch-based extruded products and methods of manufacturing those products are provided. In particular, extruded starch products processed by compression, stretching or compression and stretching provide excellent flexibility, pliability, dimensional stability, resiliency, abrasion resistance and other properties making them attractive for use as packaging materials.

We claim:  
     
         1 . A method for producing a shaped expanded starch article which comprises the steps of: 
 a. introducing an extruder feed composition comprising from about 70% to about 97% by weight starch into a twin-screw extruder;    b. extruding said composition through a die to generate an extrudate having cells; and    c. applying pressure to said extrudate to substantially compress the cells in said extrudate.    
     
     
         2 . The method of    claim 1    wherein pressure is applied by rolling said extrudate.  
     
     
         3 . The method of    claim 2    further comprising the step of shaping said rolled extruded starch by pressure molding.  
     
     
         4 . The method of    claim 3    wherein said shaped article is a tray.  
     
     
         5 . The method of    claim 1    wherein pressure is applied by rolling and said rolled extrudate is also stretched.  
     
     
         6 . The method of    claim 5    further comprising the step of shaping said rolled, stretched starch extrudate by pressure molding.  
     
     
         7 . The method of    claim 6    wherein said article is a tray.  
     
     
         8 . The method of    claim 1    wherein pressure is applied to said extrudate while it is hot.  
     
     
         9 . The method of    claim 1    wherein said starch is predominately non-modified starch.  
     
     
         10 . The method of    claim 1    wherein said starch is non-modified starch.  
     
     
         11 . The method of    claim 1    wherein said extruder feed composition comprises less than 5% by weight of a polyol plasticizer.  
     
     
         12 . The method of    claim 11    wherein said extruder feed composition comprises less than about 2.5% by weight of a polyol plasticizer.  
     
     
         13 . The method of    claim 11    wherein said extruder feed comprises less than 5% by weight of polyvinyl alcohol.  
     
     
         14 . The method of    claim 1    wherein said extruder feed further comprises a nucleating agent.  
     
     
         15 . The method of    claim 14    wherein said extruder feed further comprises a lubricant.  
     
     
         16 . The method of    claim 15    wherein said extruder feed further comprises a humectant.  
     
     
         17 . The method of    claim 15    wherein said extruder feed further comprises a blowing agent.  
     
     
         18 . The method of    claim 1    wherein said extruder feed further comprises proteinaceous grain meal.  
     
     
         19 . The method of    claim 1    wherein said extruder feed comprises one or more different types of starch.  
     
     
         20 . The method of    claim 1    wherein said extruder feed further comprises glycerin monostearate.  
     
     
         21 . The method of    claim 1    wherein said extruder feed comprises rice flour.  
     
     
         22 . The method of    claim 21    wherein said extruder feed comprises a mixture of starch and rice flour.  
     
     
         23 . The method of    claim 1    wherein said extruder feed comprises recycled expanded compressed starch.  
     
     
         24 . The method of    claim 1    wherein said the starch in said extruder feed is 20% or less by weight recycled expanded compressed starch.  
     
     
         25 . The method of    claim 23    wherein said starch in said extruder feed is 10% or less by weight recycled expanded compressed starch.  
     
     
         26 . The method of    claim 1    wherein said extruder composition further comprises talc.  
     
     
         27 . The method of    claim 1    wherein sufficient pressure is applied to said extrudate to substantially crush the cells in said extrudate.  
     
     
         28 . The method of    claim 1    further comprising a step of stretching said extrudate before, after or at the same time it is compressed.  
     
     
         29 . The method of    claim 28    wherein said extrudate is compressed and stretched at the same time.  
     
     
         30 . A method for producing a shaped expanded starch article which comprises the steps of: 
 a. introducing an extruder feed composition comprising about 70% to about 95% by weight starch into a twin-screw extruder;    b. extruding said composition through a die to generate an extrudate having cells; and    c. stretching said extrudate as it emerges from said die.    
     
     
         31 . The method of    claim 30    wherein said extrudate stretched by pulling it from said die at a rated faster than the rate of extrusion.  
     
     
         32 . The method of    claim 31    wherein said extrudate is stretched at a rate up to about 1.5.  
     
     
         33 . The method of    claim 31    wherein said extrudate is stretched at rate ranging from about 1.1 to about 1.2.  
     
     
         34 . The method of    claim 30    wherein said starch is predominantly non-modified starch.  
     
     
         35 . The method of    claim 30    wherein said starch is non-modified starch.  
     
     
         36 . A method of pressure molding a shaped expanded starch article which comprises the steps of: 
 a. introducing an extruder feed composition comprising from about 70% to about 97% by weight starch into a twin-screw extruder;    b. extruding said composition through a die to generate an extrudate having cells;    c. applying sufficient pressure to substantially compress the cells in said extrudate; and    d. introducing said compressed extrudate into a pressure mold and thereafter applying sufficient pressure thereto to form said shaped expanded starch article.    
     
     
         37 . The method of    claim 36    wherein said compressed extrudate is formed into a sheet.  
     
     
         38 . The method of    claim 37    wherein said compressed extrudate sheet is produced by rolling said extrudate.  
     
     
         39 . The method of    claim 36    wherein said article is a tray.  
     
     
         40 . The method of    claim 37    wherein said compressed extrudate sheet is produced by rolling and stretching said extrudate.  
     
     
         41 . An extruder feed composition consisting essentially of the following components: 
 non-modified starch in an amount ranging from about 70% to about 97% by weight;    proteinaceous grain meal in an amount ranging from 0% up to about 10% by weight;    talc in an amount ranging from 0% up to about 10% by weight; and    a blowing agent in an amount ranging from 0% up to about 1.5% by weight, with the proviso that the extruder feed composition must contain a nucleating agent.    
     
     
         42 . The extruder feed of    claim 41    wherein talc is present in an amount ranging from about 1% up to about 10% by weight.  
     
     
         43 . The extruder feed composition of    claim 41    wherein talc is present in an amount ranging from about 1% to about 5% by weight.  
     
     
         44 . The extruder feed of    claim 41    which contains no proteinaceous grain meal.  
     
     
         45 . The extruder feed composition of    claim 41    wherein the proteinaceous grain meal is corn meal.  
     
     
         46 . The extruder feed composition of    claim 41    wherein said starch is a mixture of starches from different plant sources.  
     
     
         47 . The extruder feed composition of    claim 41    wherein said non-modified starch is cornstarch.  
     
     
         48 . The extruder feed composition of    claim 41    wherein said starch comprises rice flour.  
     
     
         49 . A shaped expanded starch article produced by the method of    claim 1   .  
     
     
         50 . An expanded starch sheet produced by the method of    claim 1   .  
     
     
         51 . A molded expanded starch article produced by pressure molding of the expanded starch sheet of    claim 50   .  
     
     
         52 . A shaped expanded starch product produced by the method of    claim 28   .  
     
     
         53 . A shaped expanded starch article produced by the method of    claim 30   .