MULTILAYER PACKAGING MATERIAL INCORPORATING A LAYER OF POST-CONSUMER, COMMINGLED PLASTICS
FIELD OF THE INVENTION
The present invention relates to a multilayer packaging material that uses commingled post-consumer plastics in at least one layer of the multilayer structure.
BACKGROUND OF THE INVENTION The use of plastics has grown substantially over the past few years, and will continue to increase as new ways are developed to replace conventional materials, such as metal and glass, with plastic. The increase in plastic usage has resulted in a corresponding increase in the generation of plastic waste.
There are generally three recognized manners of recycling plastics. In primary recycling, pre-consumer industrial scrap and salvage is collected by the plastics manufacturer at the site of manufacture. The collected scrap and salvage are re-used directly since dissimilar polymers are not collected in a commingled fashion. Secondary recycling involves sorting out choice post-consumer plastic waste, such as white polyethylene, and physically reprocessing the waste by grinding, melting, and/or reforming the plastic. Tertiary recycling, involves breaking a single-type
polymer down into monomers and oligomers. The monomers are then repolymerized.
In secondary recycling, only a small portion of the waste is removed for recycling since choice recyclables, such as white polyethylene, usually constitute only a small portion of the total amount of plastic waste. Sorting segregates the various polymer containers from one another based on the polymer material from which the container is composed. Thus, a container composed only of polyethylene is segregated from the commingled plastics and placed with other polyethylene containers for re-processing. Sorting is a generally costly and inefficient process. However, sorting is deemed necessary since the post-consumer waste comprises commingled plastics, including, for example, a mix of containers of polyethylene, polypropylene, polyethylene teraphthalate, polystyrene, polyamide, and polyvinyl chloride usually with some level of contaminant materials, such as pigments, thermoset materials, fiberglass, talc and adhesives. In manufacturing operations, commingled plastics give mixtures with poor physical properties. As such, the post-consumer, commingled plastics waste material is generally viewed as being unfit for re-processing to form containers and often finds its way into landfills.
SUMMARY OF THE INVENTION
A multilayer packaging material which provides an economical and ecologically responsible use of post-consumer, commingled plastics is set forth. The packaging material is formed as a multilayer material that comprises at least one layer formed from post-consumer, commingled plastics in such amount as to constitute either a fill material within the layer or a majority of the layer composition by weight. The post-consumer, commingled plastics layer may be compatibilized. Compatibilization may take place through: 1) chemical compatibilization treatment of the post-consumer, commingled plastics layer; 2) the addition of a compatibilizing agent to the post-consumer, commingled plastics layer; and/or 3) mechanical compatibilization of the post-consumer, commingled plastics layer. Such compatibilization allows the commingled plastics to form a layer with better physical properties than a similar uncompatibilized commingled plastics layer.
Additional polymer and structural substrate layers may be utilized depending on the particular use of the multilayer packaging material. Consumer appeal of the multilayer packaging material may be enhanced by using colorizing pigments in one or more of the polymer material layers, as well as in the post-consumer, commingled plastics layer. An oxygen barrier layer may be utilized when the multilayer packaging material is
used to store oxygen sensitive products. Tie layers may also be used to join otherwise incompatible layers to one another.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross-sectional elevation of one embodiment of the multilayer packaging material of the present invention. Fig. 2 is a cross-sectional elevation of a further embodiment of the multilayer packaging material of the present invention which includes an exterior polymer layer.
Fig. 3 is a cross-sectional elevation of an embodiment of the multilayer packaging material of the present invention which includes an oxygen barrier layer disposed between the post-consumer, commingled plastics layer and the product contact layer.
Fig. 4 is a cross-sectional elevation of an embodiment of the multilayer packaging material of the present invention which includes an oxygen barrier layer and illustrates potential placement of tie layers within the multilayer structure.
Fig. 5 is a cross-sectional elevation of an embodiment of the multilayer packaging material of the present invention which illustrates the use of colorizing pigments within the material layers.
Fig. 6 is a cross-sectional elevation of the embodiment of FIG. 5 with the addition of an oxygen barrier layer and associated tie layers.
Fig. 7 is a cross-sectional elevation of an embodiment of the multilayer packaging material of the present invention illustrating the use of a structural
substrate, such as paperboard, that assists in supporting a container formed from the packaging material.
Fig. 8 is a partial cross-sectional view of an extruder that has been modified to subject the post- consumer, commingled plastics to supercritical C0 2 as the plastics are extruded.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning first to Fig. 1, there is presented a cross-sectional elevation of one embodiment of a multilayer packaging material constructed in accordance with the teachings of the present invention. Multilayer packaging material 10 comprises a product contact layer 15 and a layer 20 of post-consumer, commingled plastics. Contact layer 15 comprises a heat sealable polymer material, preferably a polyolefin material, and more preferably polyethylene. Layer 20 comprises, for example, a post-consumer mixture of several of the following plastic materials: polyethylene, polypropylene, polyethylene teraphthalate, polystyrene, polyamide, and polyvinyl chloride usually with some level of contaminant materials, such as pigments, thermoset materials, fiberglass, talc and adhesives. It will be recognized that other post-consumer plastics mixtures may be utilized. The particular composition of layer 20 depends on the composition of the post- consumer, commingled plastics waste from which it is formed. In some instances, choicer recyclables have been removed from the waste, and layer 20 is formed from the remaining commingled plastics material. In other instances, it may be undesirable to perform any sorting operation on the plastics waste before it is used to form layer 20.
In one embodiment of the laminate, the layer 20 may comprise between about 50% to about 100%, by weight, of the post-consumer, commingled plastics. Alternatively, the post-consumer, commingled plastics may be used as a fill material in layer 20 and may constitute less than 50% by weight of the material of layer 20.
The post-consumer, commingled plastic layer 20 may further comprise from, for example, about 1% to about 20% by weight of a dark pigment, for example, carbon black, to cover-up the raw color of the post-consumer material. The raw color of the mixture may be unattractive due to the variety of pigmented materials of which the post-consumer material is typically composed. Layer 20 may be formed in any of the manners disclosed here in connection with secondary recycling methods. Layer 20 and layer 15 may, for example, be coextruded with one another to form the multilayer material 10. Depending upon the desired physical and chemical properties of the layer 20, the post-consumer, commingled plastics layer 20 may optionally be compatibilized through one or more of the following processes: 1) chemical treatment of the post-consumer, commingled plastics; 2) addition of a compatibilizing agent to the post-consumer, commingled plastics; 3) mechanical compatibilization of the post-consumer, commingled plastics.
In chemical treatment of the post-consumer, commingled plastics material, fluorine, chlorine, oxygen gas, etc., may be used to oxidize the polymer materials of the commingled plastics. When oxidized, the interstitial regions between the polymer materials provide sites at which the materials may bond to one another thereby providing a more cohesive layer.
Alternatively, or in addition to other compatibilization treatments, the post-consumer, commingled plastics layer 20 may include a compatibilizing agent of an ionomer, such as Surlyn ®, or a copolymer, such as ethylene acrylic acid (EAA) , etc. These compatibilizing agents assist in bonding the dissimilar plastic materials of layer 20 and, for example, may be coextruded with layer 20 during the manufacture of multilayer material 10. The compatibilizing agent may also comprise polyethylene, polypropylene, or any mixture thereof. Such readily available and inexpensive polymers are particularly well-suited for use in layer 20 when the post-consumer, commingled plastics of layer 20 are used as fill material.
Alternatively, or in addition to other compatibilization treatments, the post-consumer, commingled plastics layer may be mechanically compatibilized using, for example, a pulverization process. One such pulverization process suitable for use in the present context is described in Enikolopyan,
N. S., "Recycling of Materials by the Method of Elastic- Deformation Pulverization", Advances in Recovery and Recycling - Concepts and Technology, ISBN 87-89753-08-9 (1993) . Although not essential to an understanding of the disclosed multilayer material, the teachings of that reference are hereby incorporated by reference.
Post-consumer, commingled plastics layer 20 and contact layer 15 may be coextruded as a film in sheet or tubular form. If the multilayer material is extruded in a tubular form, then a package may be formed therefrom by transversely sealing the tube ends thereby creating a pouch-like package with layer 20 at the exterior and product contact layer 15 at the interior, as illustrated in FIG. 1. Fig. 2 illustrates a further embodiment of a multilayer packaging material 30 which incorporates an external layer 35 of printable polymer material. The packaging material 30 includes a post-consumer, commingled plastic layer 40 disposed between the exterior layer 35 and an interior, heat sealable product contact layer 45. Exterior layer 35 preferably comprises a polyolefin film material and, more preferably, a polyolefin material film capable of having printing affixed thereto. Most preferably, it is formed from the same heat sealable material as product contact layer 45. The three layers of Fig. 2 may be coextruded. External layer 35 is preferably used when a substrate for printing is desired. This is because the variety of
materials and contaminants present in the post-consumer, commingled plastics material generally prevent direct adhesion of the inks and dyes used for package printing. External layer 35 may further comprise a pigment, such as carbon black or Ti0 2 to prevent the raw color of layer 40 from being seen from the exterior of the container. The layers 35 and 45 may be formed from materials that are heat sealable to one another. In this manner, the multilayer packaging material 30 will be heat sealable exterior to exterior, exterior to interior, and interior to interior.
Fig. 3 illustrates a further embodiment of a multilayer packaging material 50 which is particularly well-suited for use in the containment of oxygen sensitive products. In the illustrated embodiment, the post-consumer, commingled plastics layer 55 is disposed between an exterior layer 60 and an oxygen barrier layer 65. A product contact layer 70 is disposed interior to oxygen barrier layer 65. Oxygen barrier layer 65 comprises any extrudable oxygen barrier material, for example, ethylene vinyl alcohol (EVOH) , polyvinyldichloride, polyester, polyamide, or other oxygen barrier materials. Depending on the desired physical properties of the multilayer material, it may be desirable to use an adhesive tie layer 75, such as ethylene acrylic acid (EAA) or the like, between the oxygen barrier layer 65 and the post-consumer, commingled plastics layer 55 (see Fig. 4) . Similarly,
an adhesive tie layer, for example, at 80, may be used between any of the illustrated adjacent layers to facilitate a bond between such layers. Flame or corona treatment of one or more of the illustrated layers may likewise be employed to facilitate joining of dissimilar layers.
Packaging material structures having additives for enhancing the appearance of the materials are illustrated in exemplary form in Figs. 5 and 6 at 90 and 95, respectively. In the embodiment of Fig. 5, a layer of post-consumer, commingled plastics 100 also includes carbon black as a colorizing material. Layer 100 is disposed between opposed layers 105, 110 of, for example, polyethylene, each containing Ti0 2 as a colorizing agent. The Ti0 2 gives the polyethylene layers a white appearance. A similarly colorized structure is illustrated in Fig. 6 wherein an exterior layer 115 of polyethylene and Ti0 2 is disposed exterior to a post- consumer, commingled plastics layer 120 having carbon black dispersed therein. A sandwich layer of adhesive tie layer 125/oxygen barrier (e.g., EVOH) 130/ adhesive tie layer 135 is disposed between the layer 120 and an interior product contact layer 140 of, for example, polyethylene. Depending on the thickness and/or materials used in the foregoing laminates, a flexible pouch or self- supporting structure may be formed using any of the foregoing layer sequences. Self-support of the
resulting package may be enhanced by using any of the foregoing embodiments of the packaging material in conjunction with a structural substrate. Fig. 7 illustrates one such multilayer packaging material 145 which incorporates a structural substrate 150, such as paperboard, which facilitates self-support of the packaging material. Depending on the thickness and/or the material used for the substrate 150, the structural substrate 150 may render the material suitable for use, for example, in forming a self-supporting gable-top container. In the illustrated embodiment, the multilayer material comprises an exterior sealing layer 155, such as polyethylene, the structural substrate 160, an adhesive tie layer 165, such as EAA or the like, a post-consumer, commingled plastics layer 170, and a product contact layer 175. The exterior sealing layer 155 and the product contact layer 175 may be made from heat sealable materials to render the packaging material 145 heat sealable interior to interior, exterior to interior, and exterior to exterior. It will be recognized that an adhesive tie layer may be used between any of the adjacent layers shown in Fig. 7 when bonding between otherwise incompatible polymer layers is desired, or it may be omitted. Flame or corona treatment of the layers may also be used for this purpose. Additionally, it will be recognized that one or more oxygen barrier layers may be disposed in the packaging material, or, alternatively, omitted. For
example, the product contact layer may be formed from an oxygen barrier material, or a separate oxygen barrier layer may be disposed as one of the layers between the structural substrate and the product contact layer. An oxygen barrier material may also be dispersed in the post consumer, commingled plastic layer and, for example, may function as a compatibilizing agent.
If any of the foregoing embodiments is used in connection with a food packaging container, the post- consumer, commingled plastics layer may be subject to treatment to remove and/or inactivate any undesirable chemicals present in the post-consumer mix. This can be done by extruding the layer in such a manner that the contaminants are removed. This can be achieved by heating or by a combined treatment with, for example, supercritical C0 2 . Additionally, or in the alternative, a material layer may be interposed between the post- consumer, commingled plastics layer and the food product. The interposed layer should be formed form a material that provides a barrier against migration of the contaminants from the commingled plastics layer and the food product.
Fig. 8 shows one embodiment of an extruder 180 modified to treat the post-consumer, commingled waste using a supercritical C0 2 process. As illustrated, the extruder 180 includes a hopper 185 containing the post- consumer, commingled plastics waste. Preferably, the waste has been washed in a solvent to assist in removing
unwanted contaminants from the plastics. The extruder 180 further includes a first passage 190 that communicates supercritical C0 2 to the interstitial region 195 between an extruder barrel 200 and an extruder screw 205 to place the supercritical C0 2 in contact with the commingled plastics as they pass through the extruder barrel 200. The supercritical C0 2 may then be allowed to exit a second passage 210 from the interstitial region 195. The supercritical C0 2 functions as a solvent and assists in removing unwanted contaminants from the post- consumer, commingled plastics. Such removal facilitates use of the resulting multilayer packaging material in food containers. It will be recognized that other configurations for introducing supercritical Cθ 2 to the commingled plastics may likewise be employed.
The foregoing multilayer packaging material structures provide packages which efficiently use what has heretofore been deemed waste materials. These material structures are thus environmentally friendly since they reduce the amount of plastic waste at, for example, landfills. Additionally, these material structures are economical since post-consumer, commingled plastics are generally readily available and inexpensive. While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications
may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore contemplated by the appended claims to cover such modifications as incorporate those features which come within the spirit and scope of the invention.
