Microlayer extrusion coating and laminating for flexible packaging
The present development is a process for coating a substrate with a microlayered extrusion coating, or for producing a laminate from a first substrate, a microlayered extrudate and a second substrate. The present development also includes a microlayered extrusion coating used for laminating two or more plastic extrudates. The microlayered extrusion coating comprises a microlayer core comprising a plurality of layers of gas barrier material having a thickness of less than five microns per layer with alternating tie layers. The microlayer core is sandwiched between polymeric boundary layers which are further sandwiched between polymeric skin layers. The present microlayered extrudate surprisingly exhibits a gas barrier significantly better than conventional thicker single barrier layers and increased opacity in the extrudate using white pigmented LDPE enhances the printed graphics in a laminate structure using a printed substrate.
1. An extrudate for use in extrusion lamination or extrusion coating, said extrudate comprising a first microlayered core sandwiched between boundary layers and skin layers to form a structure comprising:
skin/boundary/microlayered core/boundary/skin
wherein said skin layer and said boundary layer is selected from the group consisting of low density polyethylene, maleic anhydride, and combinations thereof, and wherein said microlayered core comprises at least one barrier microlayer selected from the group consisting of ethylene vinyl alcohol copolymer (EVOH), polyvinylidene dichloride (PVDC), vinylidene chloride/methyl acrylate copolymer, polyamide, polyester, high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET), and combinations thereof, adhered to at least one tie microlayer selected from the group consisting of maleic anhydride, anhydride modified linear low density polyethylene, ethylene methacrylate, polyamide, and combinations thereof, and wherein the thickness of the barrier microlayer is less than about five microns and the thickness of the tie microlayer is less than about five microns.
2. The extrudate of claim 1 wherein the thickness of the barrier microlayer is less than about three microns.
3. The extrudate of claim 2 wherein the thickness of the barrier microlayer is less than about one micron.
4. The extrudate of claim 1 wherein a secondary polymeric layer is incorporated between the skin and boundary layers for a structure comprising:
skin/secondary/boundary/microlayered core/boundary/secondary/skin.
5. The extrudate of claim 1 wherein a second microlayered core and a third boundary layer is incorporated between the microlayered core and the boundary layer for a structure comprising:
skin/boundary/microlayered core/boundary/microlayered core/boundary/skin.
6. The extrudate of claim 5 wherein a secondary polymeric layer is incorporated between the skin and boundary layers for a structure comprising:
skin/secondary/boundary/microlayers/boundary/microlayers/boundary/secondary/skin.
7. The extrudate of claim 5 wherein and said first microlayered core comprises at least one barrier microlayer that serves as an oxygen barrier or as a moisture barrier or to deliver improved opacity, and said second microlayered core comprises at least one barrier microlayer that serves as an oxygen barrier or as a moisture barrier or to deliver improved opacity.
8. The extrudate of claim 7 wherein said first microlayered core is different than said second microlayered core.
9. The extrudate of claim 1 wherein the microlayered core comprises a plurality of barrier layers adhered to a plurality of tie layers in a repeating sequence of microlayers represented by the structure “E/T”, wherein “E” represents a barrier microlayer and “T” represents a tie microlayer.
10. The extrudate of claim 9 wherein the microlayered core comprises between 5 and 125 microlayers.
11. The extrudate of claim 10 wherein the microlayered core comprises at least six tie microlayers and at least five barrier microlayers, said microlayers ordered such that each boundary layer adheres to a tie microlayer.
12. The extrudate of claim 10 wherein the microlayered core comprises at least five tie microlayers and at least six barrier microlayers, said microlayers ordered such that each boundary layer adheres to a barrier microlayer.
13. The extrudate of claim 1 which is further sandwiched between two polymeric films to form an extrusion laminate comprising:
film/skin/boundary/microlayered core/boundary/skin/film
wherein the thickness of the film is from about 9 microns to about 125 microns.
14. The laminate of claim 13 wherein said film is selected from the group consisting of biaxially oriented film, machine direction oriented film, cast film and blown films, wherein said films comprise polypropylene (PP), polyethylene (PE), polyester (PET), nylon, poly lactic acid (PLA), cellophane, paper, or a combination thereof.
15. An extrusion laminate having a structure comprising:
film/skin/boundary/first microlayered core/boundary/second microlayered core/boundary/skin/film
wherein said first microlayered core and said second microlayered core comprises at least one barrier microlayer adhered to at least one tie microlayer, and wherein the thickness of the barrier microlayer is less than about five microns and the thickness of the tie microlayer is less than about five microns, and wherein said barrier microlayer is selected from the group consisting of ethylene vinyl alcohol copolymer (EVOH), polyvinylidene dichloride (PVDC), vinylidene chloride/methyl acrylate copolymer, polyamide, polyester, high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET), and combinations thereof; and wherein said tie microlayer is selected from the group consisting of maleic anhydride, anhydride modified linear low density polyethylene, ethylene methacrylate, polyamide, and combinations thereof.