Polylactic acid blown film and method of manufacturing same

Abstract

The invention provides polylactic acid (PLA) films substantially free of plasticizers and methods of manufacturing same by blown film process are provided. PLA films are environmentally degradable and have applications in, at least, packaging and labeling.

1 . A method of making a polylactic acid (PLA) blown film comprising (a) providing dry pellets of PLA, (b) melting the pellets to form a molten mass at a first desired viscosity value or range of values, (c) increasing the viscosity of the molten mass to a second desired viscosity value or range of values, (d) forming a bubble from the resulting molten mass, and (e) collapsing the bubble to form a film, in which the PLA blown film is substantially free of plasticizer. 
   
   
       2 . The method of  claim 1  in which the pellets are dried in a dehumidifying hopper. 
   
   
       3 . The method of  claim 1  in which the melting step is carried out at a temperature range of about 325° F. to about 485° F. 
   
   
       4 . The method of  claim 3  in which the melting step is carried out at a temperature range of about 375° F. to about 425° F. 
   
   
       5 . The method of  claim 4  in which the melting step is carried out at a temperature of about 400° F. 
   
   
       6 - 11 . (canceled) 
   
   
       12 . The method of  claim 1  in which the viscosity increasing step is carried out in a polymer cooling unit. 
   
   
       13 . The method of  claim 1  in which the step of forming a heated bubble includes a stretching step, which orients the film. 
   
   
       14 . The method of  claim 13  in which the stretching step is carried out using a blown film orientation process. 
   
   
       15 . The method of  claim 1  which further includes annealing the film. 
   
   
       16 . The method  claim 15  in which the annealing step is carried out at a temperature ranging from about 120° F. to about 285° F. 
   
   
       17 . The method of  claim 15  in which the annealing step is carried out at a temperature ranging from about 140° F. to about 250° F. 
   
   
       18 . The method of  claim 1  in which the bubble is heated at a temperature greater than about 100° F. 
   
   
       19 . The method of  claim 18  in which the heating step is carried out at a temperature ranging from about 100° F. to about 175° F. 
   
   
       20 . The method of  claim 19  in which the heating step is carried out at a temperature ranging from about 100° F. to about 160° F. 
   
   
       21 . The method of  claim 20  in which the heating step is carried out at a temperature ranging from about 100° F. to about 140° F. 
   
   
       22 . (canceled) 
   
   
       23 . A packaged good comprising a consumable item and a PLA blown film wrapped around at least a portion of the consumable item, in which the PLA blown film is substantially free of plasticizer. 
   
   
       24 . An envelope having a front wall and a rear wall, one of said walls being provided with at least one window, in which the window comprises a blown film comprising a polylactic acid polymer and substantially free of plasticizer. 
   
   
       25 . A blown film comprising a polylactic acid (PLA) polymer and substantially free of plasticizer. 
   
   
       26 . The blown film of  claim 25  in which the PLA polymer has a molecular weight average of about 100,000 to about 400,000. 
   
   
       27 . The blown film of  claim 25  in which the PLA polymer is greater than about 90 percent by weight polylactide. 
   
   
       28 . The blown film of  claim 25  in which the blown film further comprises a second PLA polymer. 
   
   
       29 . The blown film of  claim 25  in which the PLA polymer has a mesolactide level of about 10 percent to about 20 percent. 
   
   
       30 . The blown film of  claim 25  in which the film further comprises a colorant. 
   
   
       31 . The blown film of  claim 30  in which the colorant is present at a concentration between about 1 to about 20 percent by weight. 
   
   
       32 . The blown film of  claim 31  in which the colorant is TiO 2 . 
   
   
       33 . A blown film comprising a polylactic acid (PLA) polymer and less than about 2 weight percent plasticizer. 
   
   
       34 . A blown film comprising a polylactic acid (PLA) polymer and less than about 10 weight percent of a lactide selected from the group consisting of D-lactide, L-lactide, meso D,L-lactide and racemic D,L-lactide. 
   
   
       35 . A blown film according to  claim 34  in which the weigh percent of a lactide is less than about 5 percent. 
   
   
       36 . A blown film according to  claim 35  in which the weigh percent of a lactide is less than about 2 percent.