Low seal initiation lid for rigid substrates

Abstract

A polyolefin-based heat sealable and peelable lidding film. The peelable seal films comprise from 5 to 95 percent by weight of a polyolefin based plastomer or elastomer and from 5 to 95 percent by weight of a second plastomer or elastomer. The invention also relates to methods of making and using the heat sealable, peelable seal films, having improved low seal initiation temperature.

1 . A lidding film comprising:
 a heat sealable and peelable layer comprising 5 to 95 wt % of a first polyolefin based plastomer or elastomer and from 5 to 95 wt % of a second plastomer or elastomer, wherein the second plastomer or elastomer has a different density and melt index than the first polyolefin based plastomer or elastomer.   
     
     
         2 . The lidding film of  claim 1 , wherein the film has a seal strength of 1-3 lbs/, measured at 275° F., 30 psia, and 0.5 seconds dwell, when sealed to polypropylene or crystalline polyester trays. 
     
     
         3 . The lidding film of  claim 1 , wherein the thickness of the heat sealable and peelable layer is between 2-100 microns. 
     
     
         4 . The lidding film of  claim 1 , wherein the first polyolefin based plastomer or elastomer is a polyolefin-based plastomer with a density of between 0.84 and 0.91 gm/cubic cm based on ASTM D792 and a melt index between 3 and 10 gm/10 min, based on ASTM D1238. 
     
     
         5 . The lidding film of  claim 1 , wherein the first polyolefin based plastomer or elastomer has a vicat softening point of 40-60 degree C. based on ASTM D1525. 
     
     
         6 . The lidding film of  claim 1 , wherein the second polyolefin based plastomer or elastomer has a density of between 0.880 and 0.92 gm/cubic cm based on ASTM D792 and a melt index between 6 and 10 gm/10 min based on ASTM D1238. 
     
     
         7 . The lidding film of  claim 1 , wherein the second propylene based plastomer or elastomer has a vicat softening point of 60-90 ° C. based on ASTM D1525. 
     
     
         8 . The lidding film of  claim 1 , further comprising a base layer comprising polyester. 
     
     
         9 . The lidding film of  claim 8 , wherein the base layer has a thickness of 9-75 microns. 
     
     
         10 . The lidding film of  claim 8 , wherein the base layer is biaxially oriented. 
     
     
         11 . A sealed rigid substrate comprising a rigid substrate and the lidding film of  claim 1 . 
     
     
         12 . The sealed rigid substrate of  claim 11 , wherein the substrate comprises polypropylene, polyester, coated paperboard, or coated aluminum. 
     
     
         13 . A method of making a lidding film comprising:
 extruding a heat sealable and peelable layer comprising 5 to 95 wt % of a first polyolefin based plastomer or elastomer and from 5 to 95 wt % of a second plastomer or elastomer onto a polyester base layer to form a lidding film, wherein the second plastomer or elastomer has a different density and melt index than the first polyolefin based plastomer or elastomer.   
     
     
         14 . The method of  claim 13 , wherein the heat sealable and peelable layer and the base layer are coextruded. 
     
     
         15 . The method of  claim 13 , wherein the heat sealable and peelable layer is extrusion coated onto a preformed base layer. 
     
     
         16 . The method of  claim 15 , wherein the heat sealable and peelable layer is extrusion coated onto the preformed base layer at a melt temperature between 225-350° C. 
     
     
         17 . The method of  claim 13 , wherein the film has a seal strength of 1-3 lbs/, measured at 275° F., 30 psia, and 0.5 seconds dwell, when sealed to polypropylene or crystalline polyester trays. 
     
     
         18 . The method of  claim 13 , wherein the thickness of the heat sealable and peelable layer is between 2-100 microns. 
     
     
         19 . The method of  claim 13 , wherein the first polyolefin based plastomer or elastomer is a polyolefin-based plastomer with a density of between 0.84 and 0.91 gm/cubic cm based on ASTM D792 and a melt index between 3 and 10 gm/10 min, based on ASTM D1238. 
     
     
         20 . The method of  claim 13 , wherein the first polyolefin based plastomer or elastomer has a vicat softening point of 40-60 degree C. based on ASTM D1525. 
     
     
         21 . The method of  claim 13 , wherein the second polyolefin based plastomer or elastomer has a density of between 0.880 and 0.92 gm/cubic cm based on ASTM D792 and a melt index between 6 and 10 gm/10 min based on ASTM D1238. 
     
     
         22 . The method of  claim 13 , wherein the second propylene based plastomer or elastomer has a vicat softening point of 60-90° C. based on ASTM D1525. 
     
     
         23 . The method of  claim 13 , wherein the base layer has a thickness of 9-75 microns. 
     
     
         24 . The method of  claim 13 , wherein the base layer is biaxially oriented.