Patent Application
20140377512
This invention relates to the field of packages comprising a foamed film layer, and more specifically, to the field of packages that comprise a printed foamed film layer made at least in part of renewable, recyclable and/or biodegradable materials.
Polyolefin plastic film is used to construct a wide variety of packages such as bags, pouches, labels and wraps that hold consumer goods. For example, bags holding stacks of disposable diapers or hygiene articles, pouches for wet wipes, and bags containing granular laundry detergent are often made from plastic film. The plastic film that forms a package may be a single layer of film (called a monofilm), a combination of layers that are co-extruded, or a laminate of separately produced layers that are adhered to one another, or an extrusion lamination whereas one layer is extruded onto another previously formed layer(s). In virtually all packages, some sort of indicia is printed on the plastic film.
Two types of printing that are often utilized to imprint plastic film are flexographic printing and rotogravure printing. Flexographic printing employs a flexible printing plate made of a flexible, elastomeric material. A raised relief image of the indicia to be printed on the package is present on the flexible printer plate. The relief image is coated with ink and then pressed onto the plastic film. Often, one or more flexographic printer plates are positioned on a rotating print cylinder that prints on a sheet of film as the film moves beneath the print wheel. Each plate may carry a different type or color ink. Rotogravure printing uses a printer plate that has an engraved relief image. The printer plate is usually made of metal and is often formed into a cylindrical print roll. Ink is drawn into the engraved image and transferred to the plastic film. Because both flexographic and rotogravure printing involve contacting the surface of the plastic film with a relief image to transfer the ink to the film, variations in surface texture of the plastic film will impact print quality. Rotogravure presses may have multiple print rolls whereas each print roll can carry a different type or color ink.
Much of the cost associated with plastic film packages is the cost of the plastic resin that is used to make the film. Recent technological developments have made it feasible to produce foamed polyolefin film of suitable thickness (10-250 microns) and strength for the types of packages described above. Several exemplary foamed polyolefin films that are suitable for packages are described in European Patent No. 1 646 677. The use of foamed thin film allows for replacement of part of the resin (e.g., 5-50% by weight) with gaseous bubbles that are formed or incorporated in the film during a foaming process. Because the voids or cells left by the bubbles occupy volume that was formerly filled with resin, foamed film allows for a reduction in resin without a corresponding reduction in film thickness, commonly referred to as the film's caliper.
One notable feature of foamed thin films is that they have a rough surface texture as compared to a non-foamed film of the same caliper. The rough texture, caused by the presence of the voids in the film, makes it difficult to print directly on the foamed thin film using flexographic or rotogravure printing. The rough texture tends to cause voids in ink coverage due to the recesses in the surface not contacting the print plate. In addition to detracting from the appearance of a package and its graphics and text, these voids in ink coverage may degrade an image of a bar code to such a degree that a bar code reader could not decode the bar code.
Most of the materials used in fabrication of consumer packaging applications are derived from non-renewable resources, such as petroleum. Often, the components of consumer packages are made from polyolefins, such as polyethylene, polypropylene, and polyethylene terephthalate. These polymers are derived from monomers, such as ethylene, propylene, and terephalic acid, which are typically obtained directly from petroleum, coal and/or natural gas via cracking and refining processes. The price and availability of the petroleum/coal/natural gas feedstock therefore has a significant impact on the price of consumer packages which utilize materials derived from petrochemicals. As the worldwide price of petroleum escalates, so does the price of polyolefin based packaging. Moreover, many consumers display an aversion to purchasing products that are packaged in materials derived from petrochemicals. Other consumers may have adverse perceptions about products derived from petrochemicals being “unnatural” or not environmentally friendly.
Accordingly, it is of continued interest to provide consumer packages which are at least partially fabricated from renewable or recycled resources. It may also be desirable to provide renewable and/or recyclable packaging that is also biodegradable.
In one aspect, a method of constructing a package having printed indicia of acceptable quality includes providing at least one layer of foamed thin film and printing the indicia on the printed surface by applying ink to a printer surface and contacting the printed surface with the inked printer surface to coat the printed surface with ink. The layer of foamed thin film comprises a bio-based content of between about 10% and about 100%, a caliper of between 10 and 250 microns, and between 5% to 50% density reduction as compared to a non-foamed thin film of substantially the same caliper and composition, wherein a first surface of the at least one layer of foamed thin film is the printed surface of the package. The printer surface comprises a plurality of raised dots, the raised dots having top surfaces configured to contact the printed surface to imprint the indicia on the printed surface, and wherein the raised dots have a dot percentage of no greater than approximately 70%.
In another aspect, a method of constructing a package having printed indicia of acceptable quality includes providing at least one layer of foamed thin film and printing the indicia on the printed surface by applying ink to a printer surface and contacting the printed surface with the inked printer surface to coat the printed surface with ink. The layer of foamed thin film comprises a bio-based content of between about 10% and about 100%, a caliper of between 10 and 250 microns, and between 5% to 50% density reduction as compared to a non-foamed thin film of substantially the same caliper and composition, wherein a first surface of the at least one layer of foamed thin film is the printed surface of the package. The printer surface comprises a half tone rotogravure print cylinder configured to contact the printed surface to imprint the indicia on the printed surface, the print cylinder having a dot percentage of no greater than approximately 70%.
In yet another aspect, a package includes at least one layer of foamed thin film and printed indicia of acceptable quality that is printed on a printed surface of the package, wherein a first surface of the at least one layer of foamed thin film is the printed surface of the package. The layer of foamed thin film includes a bio-based content of between about 10% and about 100%, a caliper of between 10 and 250 microns, and between 5% to 50% density reduction as compared to a non-foamed thin film of substantially the same caliper and composition, wherein a first surface of the at least one layer of foamed thin film is the printed surface of the package.
As used herein, the following terms have the following meanings:
“Agricultural product” refers to a renewable resource resulting from the cultivation of land (e.g., a crop) or the husbandry of animals (including fish).
“Bio-based content” refers to the amount of carbon from a renewable resource in a material as a percent of the mass of the total organic carbon in the material, as determined by ASTM D6866-10, Method B. Note that any carbon from inorganic sources such as calcium carbonate is not included in determining the bio-based content of the material.
“Biodegradation” refers to a process of chemical dissolution of materials by microorganisms or other biological means.
“Bio-identical polymer” refers to polymers that are made from monomers where at least one monomer is derived from renewable resources. For instance, a bio-identical polyolefin is made from olefins that are derived from renewable resources, whereas a petro-based polyolefin is made from olefins typically derived from non renewable oil or gas.
“Bio-new polymer” refers to polymers that are directly derived (i.e., no intermediate compound in the derivation process) from renewable resources. Such renewable resources include cellulose (e.g. pulp fibers), starch, chitin, polypeptides, poly(lactic acid), polyhydroxyalkanoates, and the like.
“Microorganism” is defined as an organism that is too small to see with the naked eye, such as bacteria, fungi, archaea, and protists.
“Monomeric compound” refers to an intermediate compound that may be polymerized to yield a polymer.
“Petrochemical” refers to an organic compound derived from petroleum, natural gas, or coal.
“Petroleum” refers to crude oil and its components of paraffinic, cycloparaffinic, and aromatic hydrocarbons. Crude oil may be obtained from tar sands, bitumen fields, and oil shale.
“Polymer” refers to a macromolecule comprising repeat units where the macromolecule has a molecular weight of at least 1000 Daltons. The polymer may be a homopolymer, copolymer, terpoymer, etc. The polymer may be produced via fee-radical, condensation, anionic, cationic, Ziegler-Natta, metallocene, or ring-opening mechanisms. The polymer may be linear, branched and/or cross-linked.
“Polyethylene” and “polypropylene” refer to polymers prepared from ethylene and propylene, respectively. The polymer may be a homopolymer, or may contain up to about 10 mol % of repeat units from a co-monomer.
“Polymers derived directly from renewable resources” refer to polymers obtained from a renewable resource without intermediates.
“Post-consumer recycled polymers” refer to synthetic polymers recovered after consumer usage and includes recycled polymers from plastic bottles (e.g., laundry, milk, and soda bottles).
“Printed indicia of acceptable quality” means indicia such as, for example, characters, graphics, and regions of color that meet industry standards for clarity and density of print on consumer packaging. One informal way of determining whether the indicia are of acceptable quality is whether voids in the ink in the region through which the underlying foamed film can be seen with the naked eye. Two industry known tests used to measure whether bar code indicia are of acceptable quality are ISO/IEC 15415 Bar Code Print Quality Test Specification and ISO/IEC 15416 that grades readability of bar codes from “4A” (best) to “OF” (worst). A bar code readability of 2C as measure by ISO/IEC 15416 is generally considered as acceptable quality in the industry. Another exemplary way of determining whether graphics and regions of color are of acceptable quality is to measure the density of the printed area with a densitometer. In many instances, specific test patterns can be printed and measured using ASTM F 2036. A density of 1.1 to 1.8 Density Units for a solid black region printed on white paper is generally considered to be of acceptable quality in the industry.
“Renewable resource” refers to a natural resource that can be replenished within a 100 year time frame. The resource may be replenished naturally, or via agricultural techniques. Renewable resources include plants, animals, fish, bugs, insects, bacteria, fungi, and forestry products. They may be naturally occurring, hybrids, or genetically engineered organisms. Natural resources such as crude oil, coal, and peat which take longer than 100 years to form are not considered to be renewable resources.
“Synthetic polymer” refers to a polymer which is produced from at least one monomer by a chemical process. A synthetic polymer is not produced directly by a living organism.
“Thin film” is defined as a film having a caliper that is suitable for use in packages such as bags, pouches, labels and wraps for consumer goods, such as, for example, film calipers from about 10 to about 250 microns. As used herein, the term “foamed thin film” designates a film containing at least one layer having a caliper from about 10 microns to about 250 microns and that comprises gaseous bubbles, void volumes, or cells wherein that the at least one layer exhibits a density reduction of at least about 5% by yield (as determined by ASTM D4321) versus a film of the same thickness that does not comprise gaseous bubbles, void volumes, or cells.
A package and a method of constructing a package that includes at least one layer of printed foamed thin film which comprise at least one polymer that is at least partially derived from renewable or recycled resources is provided herein. The foamed thin film has a caliper of from about 10 microns to about 250 microns thick. The foamed thin film comprises from about 5% to about 50% density reduction as compared to a non-foamed thin film of substantially the same composition and caliper.
The package may comprise a monolayer foamed film, or multiple layers where at least one layer is foamed. A package may include a foamed thin film co-extrusion that includes at least one foamed thin film layer. A package may include a foamed thin film laminate that includes at least one foamed thin film layer. The foamed thin film layer may be, for example, blown, cast, biaxially oriented cast, post film formation process oriented (i.e., stretched, drawn or tentered) in the cross or machine orientated direction, foamed polyethylene or foamed polypropylene.
A package may include at least one layer of foamed thin film made of a plastic resin and a whitening or coloring additive that is added to the plastic resin. The resin could be a traditional petro-based polyolefin, or it could be a renewable based polyolefin, or a blend thereof. Alternatively it could be a blend comprising a petro-based or renewable based polyolefin blend mixed with a renewable “bio-new” material that is chemically different to traditional petro-based polyolefins. The film could be comprised of a material or mixture of materials having a total bio-based content of about 10% to about 100% using ASTM D6866-10, method B.
In one embodiment, the package comprises from about 5% to about 99% by weight of a polymer (A). Polymer (A) comprises at least one or possibly more of a low density polyethylene (LDPE), a polar copolymer of polyethylene such as ethylene vinyl acetate (EVA), a linear low density polyethylene (LLDPE), a high density polyethylene homopolymer/high density polyethylene copolymer, a medium density polyethylene, a very low density polyethylene (VLDPE), a plastomer, a polypropylene/copolypropylene/heterophasic polypropylene, polyethylene terephthalate (PET), PLA (e.g., from Natureworks), polyhydroxyalkanoate (PHA), poly(ethylene-2,5-furandicarboxylate) (PEF), cellulose (available from, for example, Innovia), NYLON 11 (i.e., Rilsan® from Arkema), starch (either thermoplastic starch or starch fillers bio-polyesters, (e.g., those made from bio-glycerol, organic acid, and anhydride, as described in U.S. Patent Application No. 2008/0200591, incorporated herein by reference), polybutylene succinate, polyglycolic acid (PGA), and polyvinyl chloride (PVC). At least one of the constituents of polymer (A) is at least partially derived from a renewable resource. Recycled materials may also be in added. In specific cases, materials that are biodegradable may be utilized. The whitening or coloring additive is selected to produce a foamed thin film having an opacity value of from about 35% to about 99%. The whitening agent is of substantially the same composition and is present in substantially the same amount as would be selected to produce substantially the same light reflectivity in a non-foamed thin film of substantially the same caliper and substantially the same composition. Some of the “bio-new” materials may further contribute to increasing the opacity of the film, as the presence of this additional material within the film structure can lead to additional light reflectivity, due to their typical incompatibility with the polyolefin matrix. In addition to introducing renewable content and opacity (depending on the exact blend), the addition of a “bio-new” material in particular may modify the performance of the “easy open” feature, depending on the exact type and % of “bio-new” content.
As can be seen best in
NaHCO3(Sodium Hydro Carbonate Powder)+H+(Acidifier)→Na−+CO2+H2O
Some of the carbon dioxide bubbles 14 escape the molten resin 12 while others are trapped in the resin 12 during cooling to form voids that remain after solidification of the resin. An alternative to the use of chemical blowing agents that react in the resin to produce bubbles 14 is to inject a gas such as, for example, carbon dioxide or nitrogen into the molten plastic within the extruder prior to it leaving the die, during film manufacture (such as practices in the Mucell process by the Trexel Corporation). The bubbles 14 shown in
The monofilm 10 may also be a top, or printed, layer of foamed thin film co-extrusion (not shown) or a foamed thin film laminate (not shown). Many film packages use thin film co-extrusions or laminates because the composition of each layer may be selected to contribute a desired quality to the resulting package. To produce a foamed thin film co-extrusion, resins for each layer are co-extruded while molten and cooled together to form a layered thin film co-extrusion. Thus, the foamed thin film co-extrusion includes layers of each type of resin directly adjacent one another. Foamed thin film co-extrusions may include layers that are selected to provide, for example, strength, opacity, print quality, and moisture resistance.
Foamed thin film laminates are similar to thin film co-extrusions because both include layers of different types that are selected to contribute a desired quality to the resulting package. However, rather than being combined in a molten form, the layers of a thin film laminate are separately formed and cooled. Laminates are often used when one or more of the layers is not well suitable for co-extrusion, such as, for example, metallized layers that require significantly different processing techniques as compared to plastic layers. The separate layers are then fixed to one another, such as, for example, using adhesive. According to the present invention, foamed thin film co-extrusions and laminates have a top layer that is foamed. Package indicia are printed on this top layer. Further contemplated are coat-extruded laminates where at least one layer is a foamed layer which can be either the previously formed substrate that is later coat-extruded with a different layer, or the foamed layer can be the coat-extruded layer. In the case of the foamed layer being a previously foamed substrate that is later coat-extruded with a different layer, the foamed layer can be printed before, during, or after the coat-extrusion process. In the case of the foamed layer being the coat extruded layer, it is printed after the coat extrusion process at any time when the layer is sufficiently cooled for printing.
Regardless of whether the printed foamed layer is a monofilm, or a layer in a multi-layer structure, a foamed film layer can be printed at any convenient time. It can be printed on one or both sides, and the sides may be printed concurrently or in sequence. The foamed thin film or foamed film layer can receive printing by one or both of flexographic and rotogravure printing processes.
Flexographic printing is a method of direct rotary printing that uses a resilient relief image in a plate of rubber or photopolymer to print indicia on plastic film used to make packages. In many instances, the plate or plates are installed on a rotatable print cylinder that prints on a continuous sheet of plastic film as it passes beneath the print cylinder.
It has been discovered that using a flat flexographic printer surface such as the printer surface 112 to print on foamed thin films (e.g., foamed thin film 10) produces less than printed indicia of acceptable quality. Voids in the ink are visible to the naked eye, making the print quality unacceptable for many packaging applications. Various adjustments to the flexographic print process used with non-foamed thin films have been made in an attempt to achieve an acceptable level of ink coverage on foamed thin films. For example, the pressure with which the printer surface 112 contacts the printed surface on the foamed thin film has been increased and the viscosity of the ink has been decreased in an effort to better fill the sunken contours of the rough surface of the foamed thin film 10. Neither of these two approaches was able to produce printed indicia of acceptable quality on the foamed thin film.
In light of the difficulties with achieving acceptable print quality on foamed thin films, one way to produce printed packages with foamed thin film would be to cover the foamed thin film with a printable non-foamed layer, such as, for example, a co-extruded or laminated layer. However, inclusion of a specialized print layer on the foamed thin film would cancel out much of the cost savings realized by the use of foamed thin film. Therefore, it is desirable to develop a method for printing directly on a foamed thin film whether the foamed thin film later comprises a monofilm or is used as a layer in a multi-layer structure.
Surprisingly, print quality appears to drop off at dot percentages greater than 70% as voids in the ink become visible. One reason that dotted print plates may work better than solid print plates on foamed thin film 10 may be that the flexible raised dots 32 are able to move and conform to the rough surface, such as into the recessed areas of the rough printed surface 16 of the foamed thin film 10. Also surprisingly, increased viscosity ink, such as, for example, a 20 second increase in viscosity over the viscosity of ink used on non-foamed thin films also enhances the quality of ink coverage when used in addition to the dotted print plate 30. In some circumstances, it may be advantageous to also increase the pressure with which the printer surface 31 contacts the printed surface 16. Another measure that has been observed to improve print quality on foamed thin films is use of a softer durometer material on the print plate 30.
For example, in one test, a dotted printer plate 30 having a dot percentage between about 50% to about 60% was used to produce printed indicia of acceptable quality on a 40 μm foamed thin film with approximately 20% resin reduction. The pressure on the print cylinder was increased by 20μ and the pressure on the anilox roller was increased by 10μ as compared to the pressures that would be used with non-foamed thin film of the same caliper. An ink having a 20 second increase in ink viscosity as compared to inks used with non-foamed thin films was used. This configuration produced a satisfactory level of ink coverage on foamed thin films. In order to compensate for the use of the dotted printer plate, it may be advantageous to increase the intensity of the ink by approximately 30-50%. Intensity of an ink is an indication of the strength of color of the ink. The following chart summarizes printing parameters for direct flexographic printing on foamed films as compared to printing parameters for printing on non-foamed films.
It is believed that using dotted or halftone rotogravure print plates having a dot percentage of no more than 70% will also be effective to print regions of full coverage of ink 15 on foamed thin film 10. It is also expected that increasing the viscosity and intensity of the ink will have a beneficial effect on the print quality of the indicia on foamed thin films.
Polymers Derived from Renewable & Sustainable Resources
A number of renewable resources contain polymers that are suitable for use in consumer packages (i.e., the polymer that is obtained from the renewable resource without intermediates). Suitable extraction and/or purification steps may be necessary, but no intermediate compound is required. Such polymers that are derived directly from renewable resources include cellulose (e.g. pulp fibers), starch, chitin, polypeptides, poly(lactic acid), polyhydroxyalkanoates, and the like. We typically describe such polymers as “bio-new” polymers. These polymers may be subsequently chemically modified to improve end use characteristics (e.g., conversion of cellulose to yield carboxycellulose or conversion of chitin to yield chitosan). However, in such cases, the resulting polymer is a structural analog of the starting polymer. Any polymers derived directly from renewable resources with no intermediate compounds (and their derivatives) that are known in the art may be useful herein. All of these materials are within the scope of the present disclosure.
Synthetic polymers of the present disclosure can be derived from a renewable resource via an indirect route involving one or more intermediate compounds. Suitable intermediate compounds derived from renewable resources include sugars, such as, for example, monosaccharides, disaccharides, trisaccharides, and oligosaccharides. Sugars such as sucrose, glucose, fructose and maltose may be readily produced from renewable resources such as sugar cane and sugar beets. Sugars may also be derived (e.g., via enzymatic cleavage) from other agricultural products such as starch or cellulose. For example, glucose may be prepared on a commercial scale by enzymatic hydrolysis of corn starch. While corn is a renewable resource in North America, other common agricultural crops may be used as the base starch for conversion into glucose. Wheat, buckwheat, arracaha, potato, barley, kudzu, cassava, sorghum, sweet potato, yam, arrowroot, sago, and other similar starchy fruit, seeds, or tubers may also be used in the preparation of glucose.
Other suitable intermediate compounds derived from renewable resources include monofunctional alcohols such as methanol or ethanol and polyfunctional alcohols such as glycerol. Ethanol may be derived from many of the same renewable resources as glucose. For example, cornstarch may be enzymatically hydrolyzed to yield glucose and/or other sugars. The resultant sugars can be converted into ethanol by fermentation. As with glucose production, corn is an ideal renewable resource in North America; however, other crops may be substituted. Methanol may be produced from fermentation of biomass. Glycerol is commonly derived via hydrolysis of triglycerides present in natural fats or oils, which may be obtained from renewable resources such as animals or plants.
Other intermediate compounds derived from renewable resources include organic acids (e.g., citric acid, lactic acid, alginic acid, amino acids etc.), aldehydes (e.g., acetaldehyde), and esters (e.g., cetyl palmitate, methyl stearate, methyl oleate, etc.). Additional intermediate compounds such as methane and carbon monoxide may also be derived from renewable resources by fermentation and/or oxidation processes.
Intermediate compounds derived from renewable resources may be converted into polymers (e.g., glycerol to polyglycerol) or they may be converted into other intermediate compounds in a reaction pathway which ultimately leads to a polymer useful in a consumer package. An intermediate compound may be capable of producing more than one secondary intermediate compound. Similarly, a specific intermediate compound may be derived from a number of different precursors, depending upon the reaction pathways utilized.
Particularly desirable intermediates include olefins. Olefins such as ethylene and propylene may also be derived from renewable resources. For example, methanol derived from fermentation of biomass may be converted to ethylene and or propylene, which are both suitable monomeric compounds, as described in U.S. Pat. Nos. 4,296,266 and 4,083,889. Ethanol derived from fermentation of a renewable resource may be converted into the monomeric compound ethylene via dehydration as described in U.S. Pat. No. 4,423,270. Similarly, propanol or isopropanol derived from a renewable resource can be dehydrated to yield the monomeric compound of propylene as exemplified in U.S. Pat. No. 5,475,183. Propanol is a major constituent of fusel oil, a by-product formed from certain amino acids when potatoes or grains are fermented to produce ethanol.
Charcoal derived from biomass can be used to create syngas (i.e., CO+H2) from which hydrocarbons such as ethane and propane can be prepared (Fischer-Tropsch Process). Ethane and propane can be dehydrogenated to yield the monomeric compounds of ethylene and propylene.
Other sources of materials to form polymers derived from renewable or sustainable resources include post-consumer recycled materials. Sources of synthetic post-consumer recycled materials can include plastic bottles (e.g., soda bottles), plastic films, plastic packaging materials, plastic bags and other similar materials which contain synthetic materials which can be recovered.
In one aspect, the present disclosure is directed to films having at least one layer of a composition comprising an intimate admixture of a thermoplastic polymer and a wax having a melting point greater than 25° C. The wax can have a melting point that is lower than the melting temperature of the thermoplastic polymer. The wax can be present in the composition in an amount of about 5 wt % to about 40 wt %, about 8 wt % to about 30 wt %, or about 10 wt % to about 20 wt %, based upon the total weight of the composition. The wax can comprise a lipid, which can be selected from the group consisting of a monoglyceride, diglyceride, triglyceride, fatty acid, fatty alcohol, esterified fatty acid, epoxidized lipid, maleated lipid, hydrogenated lipid, alkyd resin derived from a lipid, sucrose polyester, or combinations thereof. The wax can comprise a mineral wax, such as a linear alkane, a branched alkane, or combinations thereof. Specific examples of mineral wax are paraffin and petrolatum. The wax can be selected from the group consisting of hydrogenated soy bean oil, partially hydrogenated soy bean oil, epoxidized soy bean oil, maleated soy bean oil, tristearin, tripalmitin, 1,2-dipalmitoolein, 1,3-dipalmitoolein, 1-palmito-3-stearo-2-olein, 1-palmito-2-stearo-3-olein, 2-palmito-1-stearo-3-olein, 1,2-dipalmitolinolein, 1,2-distearo-olein, 1,3-distearo-olein, trimyristin, trilaurin, capric acid, caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and combinations thereof. The wax can be selected from the group consisting of: a hydrogenated plant oil, a partially hydrogenated plant oil, an epoxidized plant oil, a maleated plant oil. Specific examples of such plant oils include soy bean oil, corn oil, canola oil, and palm kernel oil. The wax can be dispersed within the thermoplastic polymer such that the wax has a droplet size of less than 10 μm, less than 5 μm, less than 1 μm, or less than 500 nm within the thermoplastic polymer. The wax can be a renewable material.
In one aspect, the present disclosure is directed to films having at least one layer of a composition comprising an intimate admixture of a thermoplastic polymer and about 5 wt % to about 40 wt % of an oil, based upon the total weight of the composition, wherein the oil has a melting point of 25° C. or less and a boiling point greater than 160° C. The oil can comprise a lipid, which can be selected from the group consisting of a monoglyceride, diglyceride, triglyceride, fatty acid, fatty alcohol, esterified fatty acid, epoxidized lipid, maleated lipid, hydrogenated lipid, alkyd resin derived from a lipid, sucrose polyester, or combinations thereof. The oil can comprise a mineral oil, such as a linear alkane, a branched alkane, or combinations thereof. The oil can be selected from the group consisting of soy bean oil, epoxidized soy bean oil, maleated soy bean oil, corn oil, cottonseed oil, canola oil, castor oil, coconut oil, coconut seed oil, corn germ oil, fish oil, linseed oil, olive oil, oiticica oil, palm kernel oil, palm oil, palm seed oil, peanut oil, rapeseed oil, safflower oil, sperm oil, sunflower seed oil, tall oil, tung oil, whale oil, triolein, trilinolein, 1-stearo-dilinolein, 1-palmito-dilinolein, lauroleic acid, linoleic acid, linolenic acid, myristoleic acid, oleic acid, palmitoleic acid, 1,2-diacetopalmitin, and combinations thereof. The oil can be dispersed within the thermoplastic polymer such that the oil has a droplet size of less than 10 μm, less than 5 μm, less than 1 μm, or less than 500 nm within the thermoplastic polymer. The oil can be a renewable material.
In one aspect, the present disclosure is directed to films having at least one layer of a composition comprising an intimate admixture of a thermoplastic starch (TPS), a thermoplastic polymer and an oil, wax, or combination thereof present in an amount of about 5 wt % to about 40 wt %, based upon the total weight of the composition.
Some or all of the above detailed materials may also be bio-degradable.
Olefins derived from renewable resources may be polymerized to yield polyolefins. Such polymers are typically referred to as “bio-identical” polymers. Ethylene and propylene derived from renewable resources may be polymerized under the appropriate conditions to prepare polyethylene and/or polypropylene having desired characteristics for use in consumer packages. The polyethylene and/or polypropylene may be high density, medium density, low density, or linear-low density. Further, polypropylene can include homopolymer-polypropylene or co-polymer polypropylene. Polyethylene and/or polypropylene may be produced via free-radical polymerization techniques, or by using Ziegler-Natta (ZN) catalysis or Metallocene catalysts. Examples of such bio-sourced polyethylenes and polypropylenes are described in U.S. Publication Nos. 2010/0069691, 2010/0069589, 2009/0326293, and 2008/0312485; PCT Application Nos. WO2010063947 and WO2009098267; and European Patent No. 1102569. Other olefins that can be derived from renewable resources include butadiene and isoprene. Examples of such olefins are described in U.S. Publication Nos. 2010/0216958 and 2010/0036173.
Such polyolefins being derived from renewable resources can also be reacted to form various copolymers, including for example, random block copolymers, such as ethylene-propylene random block copolymers (e.g., Borpact™ BC918CF manufactured by Borealis). Such copolymers and methods of forming the same are contemplated and described for example in European Patent No. 2121318. In addition, the polyolefin derived from a renewable resource may be processed according to methods known in the art into a form suitable for the end use of the polymer. The polyolefin may comprise mixtures or blends with other polymers such as polyolefins derived from petrochemicals.
Bio-polyethylene terephthalate is available from Teijin Fibers Ltd. It also can be produced from the polymerization of bio-ethylene glycol with bio-terephthalic acid. Bio-ethylene glycol can be derived from renewable resources via a number of suitable routes, such as, for example, those described in WO/2009/155086 and U.S. Pat. No. 4,536,584, each incorporated herein by reference. Bio-terephthalic acid can be derived from renewable alcohols through renewable p-xylene, as described in WO/2009/079213, which is incorporated herein by reference. In some embodiments, a renewable alcohol (e.g., isobutanol) is dehydrated over an acidic catalyst in a reactor to form isobutylene. The isobutylene is recovered and reacted under the appropriate high heat and pressure conditions in a second reactor containing a catalyst known to aromatize aliphatic hydrocarbons to form renewable p-xylene. In another embodiment, a renewable alcohol (e.g., isobutanol) is dehydrated and dimerized over an acid catalyst. The resulting diisobutylene is recovered and reacted in a second reactor to form renewable p-xylene. In yet another embodiment, a renewable alcohol (e.g., isobutanol) containing up to 15 wt. % water is dehydrated, or dehydrated and oligomerized, and the resulting oligomers are aromatized to form renewable p-xylene. Renewable phthalic acid or phthalate esters can be produced by oxidizing p-xylene over a transition metal catalyst (see, e.g., Ind. Eng. Chem. Res., 39:3958-3997 (2000)), optionally in the presence of one or more alcohols.
Bio-poly(ethylene-2,5-furandicarboxylate), a.k.a., bio-PEF, can be produced according to the route disclosed in Werpy and Petersen, “Top Value Added Chemicals from Biomass. Volume I—Results of Screening for Potential Candidates from Sugars and Synthesis Gas, produced by the Staff at Pacific Northwest National Laboratory (PNNL): National Renewable Energy Laboratory (NREL), Office of Biomass Program (EERE),” 2004 and PCT Application No. WO 2010/077133, which are both incorporated herein by reference.
It should be recognized that any of the aforementioned synthetic polymers (e.g., copolymers) may be formed by using a combination of monomers derived from renewable resources and monomers derived from non-renewable (e.g., petroleum) resources. For example, the copolymer can comprise propylene repeat units derived from a renewable resource and isobutylene repeat units derived from a petroleum source.
In addition to being formed from the synthetic polymers described herein, the consumer packages can further include additional additives. For example, opacifying agents can be added. Such opacifying agents can include iron oxides, carbon black, aluminum, aluminum oxide, titanium dioxide, talc and combinations thereof. These opacifying agents can comprise about 0.1% to about 5% by weight of the packages; and in certain embodiments, the opacifying agents can comprise about 0.3% to about 3% of the packages. It will be appreciated that other suitable opacifying agents may be employed and in various concentrations. Examples of opacifying agents are described in U.S. Pat. No. 6,653,523.
Furthermore, the consumer packages may comprise other additives, such as other polymers (e.g., a polypropylene, a polyethylene, a ethylene vinyl acetate, a polyethyelene terephthalate, a polymethylpentene, any combination thereof, or the like—whether derived from a renewable resource or petro-based source), a filler (e.g., glass, talc, calcium carbonate, or the like), a mold release agent, a flame retardant, an electrically conductive agent, an anti-static agent, a pigment (inorganic or organic), an antioxidant, an impact modifier, a stabilizer (e.g., a UV absorber), wetting agents, dyes, or any combination thereof.
Some materials used in the structures described herein may be a blend comprising a petro-based or renewable based “bio-identical” polyolefin blend mixed with a renewable “bio-new” material. Typically the “bio-new” material would be added to the petro-based or renewable based “bio-identical” polyolefin in the range 5-50 wt %, as higher than that would typically be difficult to process. The blend could also contain some recycled materials, typically up to around 50%—higher than that level could typically cause gels to form in the film which act as imperfections.
Validation of Polymers Derived from Renewable Resources
A suitable validation technique is through 14C analysis. A small amount of the carbon dioxide in the atmosphere is radioactive. 14C carbon dioxide is created when nitrogen is struck by an ultra-violet light produced neutron, causing the nitrogen to lose a proton and form carbon of molecular weight 14 which is immediately oxidized to carbon dioxide. This radioactive isotope represents a small but measurable fraction of atmospheric carbon. Atmospheric carbon dioxide is cycled by green plants to make organic molecules during photosynthesis. The cycle is completed when the green plants or other forms of life metabolize the organic molecules, thereby producing carbon dioxide which is released back to the atmosphere. Virtually all forms of life on Earth depend on this green plant production of organic molecules to grow and reproduce. Therefore, the 14C that exists in the atmosphere becomes part of all life forms, and their biological products. In contrast, fossil fuel based carbon does not have the signature radiocarbon ratio of atmospheric carbon dioxide.
Assessment of the renewably based carbon in a material can be performed through standard test methods. Using radiocarbon and isotope ratio mass spectrometry analysis, the bio-based content of materials can be determined. ASTM International, formally known as the American Society for Testing and Materials, has established a standard method for assessing the bio-based content of materials. The ASTM method is designated ASTM D6866-10.
The application of ASTM D6866-10 to derive a “bio-based content” is built on the same concepts as radiocarbon dating, but without use of the age equations. The analysis is performed by deriving a ratio of the amount of organic radiocarbon (14C) in an unknown sample to that of a modern reference standard. The ratio is reported as a percentage with the units “pMC” (percent modern carbon).
The modern reference standard used in radiocarbon dating is a NIST (National Institute of Standards and Technology) standard with a known radiocarbon content equivalent approximately to the year AD 1950. AD 1950 was chosen since it represented a time prior to thermo-nuclear weapons testing which introduced large amounts of excess radiocarbon into the atmosphere with each explosion (termed “bomb carbon”). The AD 1950 reference represents 100 pMC.
“Bomb carbon” in the atmosphere reached almost twice normal levels in 1963 at the peak of testing and prior to the treaty halting the testing. Its distribution within the atmosphere has been approximated since its appearance, showing values that are greater than 100 pMC for plants and animals living since AD 1950. It's gradually decreased over time with today's value being near 107.5 pMC. This means that a fresh biomass material such as corn could give a radiocarbon signature near 107.5 pMC.
Combining fossil carbon with present day carbon into a material will result in a dilution of the present day pMC content. By presuming 107.5 pMC represents present day biomass materials and 0 pMC represents petroleum derivatives, the measured pMC value for that material will reflect the proportions of the two component types. A material derived 100% from present day soybeans would give a radiocarbon signature near 107.5 pMC. If that material was diluted with 50% petroleum derivatives, for example, it would give a radiocarbon signature near 54 pMC (assuming the petroleum derivatives have the same percentage of carbon as the soybeans).
A biomass content result is derived by assigning 100% equal to 107.5 pMC and 0% equal to 0 pMC. In this regard, a sample measuring 99 pMC will give an equivalent bio-based content value of 92%.
Assessment of the materials described herein was done in accordance with ASTM D6866. The mean values encompass an absolute range of 6% (plus and minus 3% on either side of the bio-based content value) to account for variations in end-component radiocarbon signatures. It is presumed that all materials are present day or fossil in origin and that the desired result is the amount of bio-based component “present” in the material, not the amount of bio-based material “used” in the manufacturing process.
In one embodiment, a mono-layer film comprises a bio-based content value from about 10% to about 100% using ASTM D6866-10, method B. In another embodiment, a mono-layer film comprises a bio-based content value from about 20% to about 100% using ASTM D6866-10, method B. In yet another embodiment, a mono-layer film comprises a bio-based content value from about 50% to about 100% using ASTM D6866-10, method B.
In one embodiment, a multi-layer film comprises a bio-based content value from about 10% to about 100% using ASTM D6866-10, method B. In another embodiment, a multi-layer film comprises a bio-based content value from about 20% to about 100% using ASTM D6866-10, method B. In yet another embodiment, a multi-layer film comprises a bio-based content value from about 50% to about 100% using ASTM D6866-10, method B.
In order to apply the methodology of ASTM D6866-10 to determine the bio-based content of a package, a representative sample of the component must be obtained for testing. In one embodiment, a representative portion of the package can be ground into particulates less than about 20 mesh using known grinding methods (e.g., Wiley® mill), and a representative sample of suitable mass taken from the randomly mixed particles.
The consumer packages disclosed herein can optionally include a colorant masterbatch. As used herein, a “colorant masterbatch” refers to a mixture in which pigments are dispersed at high concentration in a carrier material. The colorant masterbatch is used to impart color to the final product. In some embodiments, the carrier is a bio-based plastic or a petroleum-based plastic, while in alternative embodiments, the carrier is a bio-based oil or a petroleum-based oil. The colorant masterbatch can be derived wholly or partly from a petroleum resource, wholly or partly from a renewable resource, or wholly or partly from a recycled resource. Non-limiting examples of the carrier include bio-derived or oil derived polyethylene (e.g., linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE)), bio-derived oil (e.g., olive oil, rapeseed oil, peanut oil, soybean oil, or hydrogenated plant-derived oils), petroleum-derived oil, recycled oil, bio-derived or petroleum derived polyethylene terephthalate, polypropylene, and a mixture thereof. The pigment of the carrier, which can be derived from either a renewable resource or a non-renewable resource, can include, for example, an inorganic pigment, an organic pigment, a polymeric resin, or a mixture thereof. Non-limiting examples of pigments include titanium dioxide (e.g., rutile, anatase), copper phthalocyanine, antimony oxide, zinc oxide, calcium carbonate, fumed silica, phthalocyamine (e.g., phthalocyamine blue), ultramarine blue, cobalt blue, monoazo pigments, diazo pigments, acid dye, base dye, quinacridone, and a mixture thereof. In some embodiments, the colorant masterbatch can further include one or more additives, which can either be derived from a renewable resource or a non-renewable resource. Nonlimiting examples of additives include slip agents, UV absorbers, nucleating agents, UV stabilizers, heat stabilizers, clarifying agents, fillers, brighteners, process aids, perfumes, flavors, and a mixture thereof.
In some embodiments, color can be imparted to the films of the present invention in any of the aspects by using direct compounding (i.e., in-line compounding). In these embodiments, a twin screw compounder is placed at the beginning of the injection molding, blow molding, or film line and additives, such as pigments, are blended into the resin just before article formation.
Additional materials may be incorporated into the packages of the present invention in any of the aspects to improve the strength or other physical characteristics of the plastic. Such additional materials include an inorganic salt, such as calcium carbonate, calcium sulfate, talcs, clays (e.g., nanoclays), aluminum hydroxide, CaSiO3, glass fibers, glass spheres, crystalline silicas (e.g., quartz, novacite, crystallobite), magnesium hydroxide, mica, sodium sulfate, lithopone, magnesium carbonate, iron oxide, or a mixture thereof.
In some alternative embodiments to any of the embodiments described herein, elements of the package, including the sealant, barrier material, tie layers, or mixtures thereof, include recycled material in place of, or in addition to, the bio-based material in an amount of up to 100% of the bio-based material. As used herein, “recycled” materials encompass post-consumer recycled (PCR) materials, post-industrial recycled (PIR) materials, and a mixture thereof.
In some embodiments, the structure described above may incorporate a barrier layer. The barrier material is selected from the group consisting of aluminum, metallized polyolefin substrate, metallized polyethylene terephthalate substrate, metallised cellulose, PVDC, PCTFE, sol-gel coating. Instead of a metallized coating on polyolefins or polyethylene terephthalate, the following coatings could be used—metal oxide, a nanoclay, an aluminum oxide, a silicon oxide, diamond-like carbon (DLC), and mixtures thereof. Other barrier substrates (used with or without a coating) could include EVOH, PVOH, Nylon, PVC, liquid crystal polymer. The substrates could include within their structure, an additional barrier additive (not in coating form but embedded within the polymer matrix)—one example of such additives could include nanoclays). The total barrier layer including the substrate typically has a thickness of about 6 [mu]m to about 200 [mu]m. Typically the substrate underneath the coating is cast biaxially oriented, although it could be a blown or cast film too. In some preferred embodiments, the metal is vacuum metallized aluminum. In some embodiments when the barrier material is a nanoclay, the nanoclay is selected from the group consisting of montmorillonites, vermiculite platelets, and mixtures thereof.
In embodiments of the consumer packages described herein, the ink that is deposited can be either solvent-based or water-based. In some embodiments, the ink is high abrasive resistant. For example, the high abrasive resistant ink can include coatings cured by ultraviolet radiation (UV) or electron beams (EB). In some embodiments, the ink is derived from a petroleum source. In some embodiments, the ink is derived from a renewable resource, such as soy, a plant, or a mixture thereof. Non-limiting examples of inks include ECO-SURE!™ from Gans Ink & Supply Co. and the solvent-based VUTEk(R) and BioVu™ inks from EFI, which are derived completely from renewable resources (e.g., corn). The ink is present in a thickness of about 0.5 [mu]m to about 20 [mu]m, preferably about 1 [mu]m to about 10 [mu]m, more preferably about 2.5 [mu]m to about 3.5 [mu]m.
In general, bio-new materials are often found to be more polar than current petroleum based materials. So the use of bio-new material in the printed layer may also enhance the printing process.
In embodiments of the consumer packages described herein, an optional lacquer functions to protect the ink layer from its physical and chemical environment, when reverse printing has not been used. In some embodiments, the lacquer is selected from the group consisting of resin, additive, and solvent/water. In some preferred embodiments, the lacquer is nitrocellulose-based lacquer. The lacquer is formulated to optimize durability and provide a glossy or matte finish. The lacquer is present in a thickness of up to about 25 [mu]m, preferably up to about 5 [mu]m. The lacquer could be renewable.
Non-limiting examples of the adhesive can include acrylic, polyvinyl acetate, and other commonly used adhesive tie layers suitable for polar materials. In some embodiments, the adhesive is a renewable adhesive, such as BioTAK(R) by Berkshire Labels.
In some embodiments, particular material combinations that enable the film structure to be biodegradable or degradable may be selected.
In some embodiments, the consumer packages described herein are substantially free of oxo-biodegradable additives (i.e., less than about 1 wt. %, based on the total weight of the package or article) but in some embodiments oxo-biodegradable additives may be used. Oxo-biodegradable additives consist of transition metals that theoretically foster oxidation and chain scission in plastics when exposed to heat, air, light, or a mixture thereof. Although the shortened polymer chains theoretically can be consumed by microorganisms found in the disposal environment and used as a food source, there is no data to support how long these plastic fragments will persist in the soils or marine environments, or if biodegradation of these fragments occurs at all. However, in some specific material blends, such materials may enable faster biodegradation.
In addition embodiments where a biodegradable package is desired, certain additives may be added to tune the degradability of polymers to meet a specific degradability. For example, numerous additives are known to tune the degradation of polymers with or without being triggered by some external stimulus (e.g., exposure to light) as disclosed in US 2010/0222454 A1, US 2004/0010051 A1, US2009/0286060 A1 and references therein. Additionally, the article “Photodegradation, Photooxidation, and Photostabilization of Polymers,” by Ranby and Rabek describe photodegradant materials. While not wishing to be bound by theory, one example of these additives (photo acid or photobase generators) tune the local pH in response to exposure to certain wavelengths of light, which results in hydrolysis of a polyester. Once these polymers are hydrolyzed to a lower molecular weight, they are truly biodegraded by microorganisms.
While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore the invention, in its broader aspects, is not limited to the specific details, the representative system, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
