Recyclable, high barrier sheet and tray
An improved sheet for making a three-dimensional article for holding food, such as a food tray, and a method of making a three-dimensional article. The sheet comprises a substrate and a laminate film. The laminate film may comprise a ceramic film and a copolymer layer. The copolymer layer can repair any cracks that occur due in the ceramic film when the sheet is thermoformed. The food tray is considered a single material that is recyclable.
1. A sheet for making a food tray or other article, the sheet comprising:
a polyolefin substrate; and
a coated film comprising a ceramic film and a copolymer layer; wherein
the ceramic film comprises a polyolefin film coated with a metal oxide, wherein
the copolymer layer comprises a blend of an aqueous polyvinyl alcohol (PVOH) copolymer and an aqueous polymeric adhesive.
2. The sheet of claim 1 wherein:
the polyolefin film comprises polypropylene (PP).
3. The sheet of claim 2 wherein:
the polyolefin film is approximately 50 microns thick.
4. The sheet of claim 1 wherein:
the metal oxide is selected from the group consisting of AlOx and SiOx.
5. The sheet of claim 1 wherein:
the polyolefin substrate comprises a polyolefin selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE) and polystyrene (PS).
6. The sheet of claim 1 wherein:
the substrate comprises at least about 98 wt % of the sheet.
7. The sheet of claim 6 wherein:
the copolymer layer also comprises a crosslinking additive.
8. A sheet for making a food tray or other article, the sheet comprising:
a dual barrier laminate film;
a polyolefin substrate; and
a cap layer; wherein
the dual barrier laminate film comprises a copolymer layer sandwiched between on outer ceramic film layer and an inner ceramic film layer, wherein the inner ceramic film layer is adjacent the substrate, wherein
the copolymer layer comprises a blend of an aqueous PVOH copolymer and an aqueous polymeric adhesive.
9. The sheet of claim 8 wherein:
the dual barrier laminate film is bonded to the substrate.
10. The sheet of claim 8 wherein:
the dual barrier laminate film is thermally welded to the substrate.
11. The sheet of claim 8 wherein;
each of the two ceramic film layers comprises polypropylene film coated with a metal oxide layer, wherein
each of the metal oxide layers is adjacent the copolymer layer.
12. The sheet of claim 11 wherein;
the metal oxide is AlOx.
13. The sheet of claim 11 wherein;
the metal oxide is SiOx.
14. The sheet of claim 11 wherein:
the polyolefin substrate is 1,000 microns thick; and
the polypropylene film is 50 microns thick.
15. A thermoformable sheet for making a food tray or other article, the sheet having an outer side and an inner (food contacting) side, the sheet comprising;
a dual barrier laminate film comprising a first polypropylene film layer defining the outer side of the sheet and having an inner facing side coated with a first metal oxide coating, a second polypropylene film layer having an outer facing side and coated with a second metal oxide coating, and a middle layer disposed between the first polypropylene film layer and the second polypropylene film layer and comprising a PVOH copolymer and adhesive blend;
a polyolefin substrate to provide the sheet with structural integrity; and
a cap layer defining the inner, food contacting, side of the sheet.
16. The thermoformable sheet of claim 15 wherein:
the polyolefin substrate comprises over 98% of the sheet's weight.
17. The thermoformable sheet of claim 15 wherein:
the polyolefin substrate comprises a polyolefin selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE) and polystyrene (PS).
18. The thermoformable sheet of claim 15 wherein:
the cap layer comprises virgin polypropylene.