Substantially biodegradable and compostable high-barrier packaging material and methods for production
Bio-degradable, high-barrier packaging materials and methods for production are provided. The present high-barrier packaging materials include a substrate having a print side and a back side, a coating having nano pigments on the print side and a metalized film applied to the back side with a binding layer. Preferably, at least one of the metalized film and the binding layer includes polylactic acid. Moreover, the back side preferably also includes a polylactic acid heat seal layer.
1. A bio-degradable packaging material having a water vapor transmission rate of less than 0.3 grams per 100 square inches per day at tropical conditions comprising:
a paper substrate having a print side and a back side, wherein said substrate comprises a combination of separately refined softwood and hardwood pulps, said substrate having a permeability of less than about 0.25 nm 2 and a total porosity of less than about 30%, the print side having a machine glaze;
a coating layer on said print side of said substrate, the coating comprising one or more pigments and at least one binder, wherein at least 25% by dry weight of said one or more pigments are nano pigments of clay, talc or a mixture thereof having a particle size no greater than 90 nanometers and an aspect ratio of 90:1 or greater, and wherein the at least one binder is a protein and polyvinyl alcohol; a latex and polyvinyl alcohol; ethylene acrylic acid and polyvinyl alcohol; or ethylene acrylic acid and a latex;
a metalized film layer laminated to the back side of said substrate, wherein said metalized film layer is a metalized polylactic acid film or a metalized cellophane film;
a bonding layer between said substrate and said metalized film layer wherein said bonding layer is an adhesive, a polylactic acid resin layer, an extruded tie layer, or combinations thereof; and
a polylactic acid heat seal layer over said metalized film layer.
2. The bio-degradable packaging material of claim 1 further comprising a PET emulsion top coat layer applied over said nano pigment coating layer.
3. The bio-degradable packaging material of claim 1 further comprising a print receptive top coat applied over said nano pigment coating layer.
4. The bio-degradable packaging material of claim 1 wherein said metalized film layer is adhesive laminated to the substrate and the adhesive comprises polylactic acid resin.
5. The bio-degradable packaging material of claim 1 further comprising a PET emulsion coating between the back side of said substrate and said metalized film layer.
6. The bio-degradable packaging material of claim 1 wherein said substrate comprises about 40% softwood pulp, about 56% hardwood pulp, and about 4% base ash.
7. The bio-degradable packaging material of claim 1 wherein the at least one binder comprises the protein and polyvinyl alcohol or the ethylene acrylic acid and polyvinyl alcohol, and wherein the polyvinyl alcohol has a molecular weight of about 26,000 to 34,000 and a degree of polymerization of about 260-340.
8. The bio-degradable packaging material of claim 1 wherein the softwood pulp is refined using a low intensity refining plate specific edge load of about 2.2 W-sec/m, and wherein the hardwood pulp is refined using a low intensity refining plate specific edge load of about 1.54 W-sec/m.