Foam-paperboard laminates, articles incorporating same and methods of making the same

Abstract

The present invention relates to foam-paperboard laminates (foam-paperboard laminates) prepared using an in situ foaming process. The foam-paperboard laminates of the present invention are formed by extruding LDPE polymer onto a moisture containing paperboard to provide a LDPE-coated paperboard material. Upon heating of the LDPE-coated paperboard, the moisture in the paperboard causes steam to act as a blowing agent for the LDPE and a LDPE foam is obtained. The foam is adhered to the paperboard by way of physical adhesion of the polymer to the paperboard. The foam-paperboard laminates of the present invention exhibit insulating and cushioning properties. The foam-paperboard laminates are suitable for use, for example, in insulating beverage cups, food service containers, packaging material, and in other products where laminates can be useful.

1 ) A LDPE foam-paperboard laminate comprising: 
 a) a first layer comprising a foam prepared from LDPE having a melt index of from about 8.0 to about 20.0 g/10 min as measured by ASTM 1298;    b) a second layer comprising paperboard,    wherein the laminate is prepared in an in situ process.    
     
     
         2 ) The LDPE foam-paperboard laminate of  claim 1 , wherein the foam layer comprises foam cells, wherein at least about 90% of the foam cells have an aspect ratio of 2.0 or greater.  
     
     
         3 ) The foam-paperboard laminate of  claim 1 , wherein the laminate comprises a third layer comprising an occlusive layer disposed on a surface of the paperboard opposite to the foam layer.  
     
     
         4 ) The foam-paperboard laminate of  claim 1 , wherein the LDPE has a melt index of from about 10.0 to about 20.0 g/10 min.  
     
     
         5 ) The foam-paperboard laminate of  claim 1 , wherein the LDPE is present on the paperboard at less than about 30 pounds per ream of paperboard.  
     
     
         6 ) The foam-paperboard laminate of  claim 1 , wherein the LDPE is present on the paperboard at less than about 25 pounds per ream of paperboard.  
     
     
         7 ) The foam-paperboard laminate of  claim 2 , wherein the foam layer has a caliper of less than about 15 mils.  
     
     
         8 ) The foam-paperboard laminate of  claim 2 , wherein the foam layer has a caliper of less than about 10 mils.  
     
     
         9 ) The foam-paperboard laminate of  claim 2 , wherein at least about 95% of the foam cells have an aspect ratio of 2.0 or greater.  
     
     
         10 ) The foam-paperboard laminate of  claim 1 , wherein the foam layer comprises foam cells, wherein the foam cells have an average MD ratio of less than about 1.5.  
     
     
         11 ) An insulated container prepared from the foam-paperboard laminate of  claim 1 .  
     
     
         12 ) A packaging material prepared from the foam-paperboard laminate of  claim 1 .  
     
     
         13 ) A slip-resistant material prepared from the foam-paperboard laminate of  claim 1 .  
     
     
         14 ) A LDPE foam-paperboard laminate comprising: 
 a) a first layer comprising a foam prepared from LDPE having a melt index of from about 8.0 g/10 min to about 20.0 g/10 min as measured by ASTM 1298;    b) a second layer comprising paperboard,    wherein the foam layer comprises foam cells, wherein at least about 90% of the foam cells have an average MD ratio of less than about 1.5, and wherein the laminate is prepared in an in situ process.    
     
     
         15 ) A method of making a foam paperboard laminate comprising: 
 a) providing paperboard having an outer and an inner layer, wherein the paperboard has a moisture content of from about 4 to about 10%;    b) providing a melted LDPE having a melt index of at least about 8.0 g/10 min as measured by ASTM 1298;    c) applying the melted LDPE to the outer surface of the paperboard using an extruder, thereby providing a LDPE-coated paperboard material; and    d) heating the paperboard material at from about 220° F. to about 330° F. for at least about 30 seconds thereby resulting in release of the moisture from the paperboard in the form of steam, wherein the amount of steam is sufficient to provide a LDPE foam, and wherein the foam is adhered to the paperboard surface,    thereby providing a foam-paperboard laminate.    
     
     
         16 ) The method of  claim 15 , wherein an occlusive layer is applied to an inner surface of the paperboard material prior to heating of the paperboard material.  
     
     
         17 ) The method of  claim 16 , wherein the occlusive layer comprises a polyolefin.  
     
     
         18 ) The method of  claim 16 , wherein the occlusive layer comprises LDPE, HDPE or a blend thereof.  
     
     
         19 ) The method of  claim 15 , wherein the melted LDPE is applied to the paperboard at less than about 30 pounds per ream.  
     
     
         20 ) The method of  claim 15 , wherein the melted LDPE is applied to the paperboard at less than about 25 pounds per ream.  
     
     
         21 ) The method of  claim 15 , wherein the extruder has an air gap distance of from about 9 to about 20 inches.  
     
     
         22 ) The method of  claim 15 , wherein the extruder has a die gap distance of from about 10 to about 25 mils.  
     
     
         23 ) The method of  claim 15 , wherein the LDPE is melted at from about 575 to about 625° F.  
     
     
         24 ) The method of  claim 15 , wherein the extrusion step is conducted at a web speed of greater than about 325 feet per minute.  
     
     
         25 ) The method of  claim 15 , wherein the web speed is from about 350 feet per minute to about 900 feet per minute.  
     
     
         26 ) The method of  claim 15 , wherein the heating step is conducted for from about 45 to about 180 seconds.  
     
     
         27 ) The method of  claim 15 , wherein the heating step is conducted at from about 250 to about 325° F.  
     
     
         28 ) The method of  claim 15 , wherein the foam layer comprises foam cells, wherein at least about 90% of the foam cells have an aspect ratio of 2.0 or greater.  
     
     
         29 ) The method of  claim 15 , wherein the foam layer comprises foam cells, wherein at least about 95% of the foam cells have an aspect ratio of 2.0 or greater.  
     
     
         30 ) The method of  claim 15 , wherein the foam layer comprises foam cells and wherein at least about 90% of the foam cells have an MD ratio of greater than about 1.5.  
     
     
         31 ) The method of  claim 28 , wherein the foam layer has a caliper of about 15 mils or less.  
     
     
         32 ) The method of  claim 28 , wherein the foam layer has a caliper of about 10 mils or less.  
     
     
         33 ) The method of  claim 15 , wherein the LDPE is applied at a coat weight of from about 18 to about 27 pounds per ream.  
     
     
         34 ) A method of making a LDPE foam-paperboard laminate comprising: 
 a) providing paperboard having an inner and an outer surface, wherein the paperboard has a moisture content of from about 4 to about 10%;    b) providing a melted LDPE having a melt index of at least about 5.0 g/10 min as measured by ASTM 1298;    c) applying the melted LDPE to the outer surface of the paperboard using an extruder, wherein the LDPE is applied at a web speed of at least about 325 feet per minute, thereby providing a LDPE-coated paperboard material;    d) heating the LDPE-coated paperboard material at from about 220° F. to about 330° F. for at least about 30 seconds thereby providing moisture release from the paperboard in the form of steam, wherein the amount of steam is sufficient to result in foaming of the LDPE, and wherein the foam is adhered to the paperboard surface the paperboard material,    thereby providing a foam-paperboard laminate comprising foam cells, wherein at least about 90% of the foam cells have an aspect ratio of about 2.0 or greater.    
     
     
         35 ) The method of  claim 34 , wherein the LDPE has a MI of at least about 8.0 g/10 min as measured by ASTM 1298.  
     
     
         36 ) The method of  claim 34 , wherein an occlusive layer is applied to the inner surface of the paperboard prior to the heating step.  
     
     
         37 ) The method of  claim 36 , wherein the occlusive layer comprises a polyolefin.  
     
     
         38 ) The method of  claim 36 , wherein the occlusive layer comprises LDPE, HDPE or a blend thereof.  
     
     
         39 ) The method of  claim 34 , wherein the foam layer has a caliper of about 15 mils or less.  
     
     
         40 ) The method of  claim 34 , wherein the foam layer has a caliper of about 10 mils or less.  
     
     
         41 ) The method of  claim 34 , wherein the extruder has an air gap distance of from about 9 to about 20 inches.  
     
     
         42 ) The method of  claim 34 , wherein the extruder has a die gap distance of from about 10 to about 25 mils.  
     
     
         43 ) The method of  claim 34 , wherein the melt temperature of the LDPE is from about 575 to about 625° F.  
     
     
         44 ) The method of  claim 34 , wherein the LDPE is applied to the paperboard at from about 18 to about 27 pounds per ream.  
     
     
         45 ) The method of  claim 34 , wherein the web speed is from about 350 feet per minute to about 900 feet per minute.  
     
     
         46 ) The method of  claim 34 , wherein the heating is conducted for from about 45 to about 180 seconds.  
     
     
         47 ) The method of  claim 34 , wherein the heating is conducted at from about 250 to about 325° F.