Patent Application
20210371631
The present disclosure relates to a thin, microlayer film having a pigment composition characterized by small particle sizes for use in a multilayer, heat-shrinkable film.
Heat-shrinkable films have the ability, upon being exposed to a certain temperature, to shrink or to generate shrink tension when used in a packaging application. Conventionally, heat-shrinkable films are extruded (single layer film) or coextruded (multi-layer films) from thermoplastic based materials that have been heated to their flow or melting point at an extrusion or a coextrusion die. Following extrusion, the film is subjected to a post-extrusion quench to cool the film. The film may then be reheated to a temperature in it orientation temperature range in order to stretch the film to physically orient or align the crystallites and/or the molecules of the film.
Frequently, the film is irradiated following extrusion but prior to undergoing stretch orientation. Typically the film is irradiated using electron beams to induce cross-linking between the polymer chains that make up the film.
Once a product is enclosed in the heat-shrinkable film, the packaged product is subjected to an elevated temperature by subjecting the packaged product to hot air or hot water. This causes the film to shrink forming a tight wrap surrounding the enclosed packaged product.
It has been discovered that the use of microlayers in films allows the microlayer to be adhered to other layers without the need for use of a tie especially between polar and nonpolar layers. Thus, a film formed from one or more microlayers may provide for a thinner film while still providing the needed functional properties of the film. Multiple layers, in particular, multiple microlayers may be included in the film to provide certain needed functionality to the film. Examples of particular functionalities that may be imparted to the film can include a peelable seal layer, odor-causing barrier properties, oxygen barrier, etc. However, additional functionality that remains includes a film with a color and a high opacity as well as a film having relatively good strength. In particular, these types of properties are amiss in conventional heat-shrinkable films, particularly, those heat-shrinkable films that include a microlayer.
There remains a need in the art for a microlayer that when included in a film imparts to the film a color and certain required opacity, preferably, at least about 90% opacity. There remains a further need in the art for a microlayer that, when included in a film, imparts to the film a high degree of strength allowing such films to be used in rigorous packaging applications among other uses as well where such a film is required.
Various embodiments disclosed herein relate to a microlayer and a film constructed from such a microlayer having high opacity and good strength. Without intending to be bound by theory, a microlayer and techniques described herein result in a heat-shrinkable film suitable for packaging and enduring rigorous treatment in the transport of such packaged goods.
In one embodiment, a microlayer comprises about 55 wt % to about 80 wt % of a polyethylene; about 2.5 wt % to about 20 wt % of an elastomeric copolymer; and, optionally, about 5 wt % to about 25 wt % of a pigment comprising submicron particles. Preferably, a thickness of the microlayer is no greater than about 1.5 mils. In certain embodiments where the microlayer comprises a pigment, an opacity of the microlayer is at least about 90%.
In an embodiment, the pigment comprises a carbon black. In certain embodiments, the carbon black comprises particles ranging from about 25 nm to about 200 nm in diameter. Further pursuant to these embodiments, the carbon black particles have a median diameter ranging from about 57.2 nm to about 72.4 nm.
In other embodiments, the pigment comprises a titanium dioxide (TiO2). In certain embodiments, the TiO2 comprises particles ranging from about 54 nm to about 390 nm in diameter. Further pursuant to these embodiments, the TiO2 particles have a median diameter of from about 137.5 nm to about 169.2 nm.
In certain embodiments, the polyethylene comprises about 30 wt % to about 60 wt % linear low density polyethylene; about 0 wt % to about 20 wt % low density polyethylene; and about 10 wt % to about 30 wt % medium density polyethylene. In other embodiments, the elastomeric copolymer preferably includes an ethylene octene copolymer having less than 10% by weight of an octene.
In other embodiments, a film comprises an outer layer; a substrate layer adjacent to the outer layer; and a core layer adjacent to the substrate layer, the core layer optionally comprising a pigment having submicron particles. In an embodiment, the one or more first microlayers having at least one of carbon black particles ranging from about 25 nm to about 200 nm in diameter and titanium dioxide (TiO2) particles ranging from about 54 nm to about 390 nm in diameter. In certain embodiments, a thickness of the one or more first microlayers is no greater than about 1.5 mils and an opacity of the film is at least about 90%.
In an embodiment, the one or more first microlayers may include an elastomeric copolymer. In certain embodiments, the elastomeric copolymer includes an ethylene octene copolymer, the ethylene octene copolymer having less than about 10% by weight of an octene in a preferred embodiment.
The core layer of the film may additionally include one or more second microlayers having at least one of carbon black and TiO2. In certain embodiments, the carbon black comprises particles ranging from about 25 nm to about 200 nm in diameter. In certain other embodiments, the TiO2 comprises particles ranging from about 54 nm to about 390 nm in diameter.
In an embodiment, each of the one or more second microlayers individually separates each of the one or more first microlayers. Further pursuant to this embodiment, the core layer comprises thirteen one or more first microlayers and twelve one or more second microlayers. Such a film is characterized by an Elmendorff tear strength of at least about 27.9 g.
Yet another embodiment provides a method for the manufacture of a film including the steps of passing a fluid through a plurality of microlayer assemblies to form film-like structures, the fluid comprising a pigment having one or more particulate compounds having diameters that are less than about 390 nm; aligning the plurality of microlayers to form a core layer; extruding a substrate layer that is placed adjacent to the core layer; and extruding an outer layer that is placed adjacent to the substrate layer. In an embodiment, the thickness of the microlayer is no greater than about 1.5 mils and an opacity of the film is at least about 90%.
Other aspects and embodiments will become apparent upon review of the following description taken in conjunction with the accompanying drawings. The claimed subject matter, though, is pointed out with particularity by the included claims.
The foregoing aspects and many of the attendant advantages of the disclosed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Various embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. While some preferred embodiments may be described, other embodiments may take many different forms and the claimed subject matter should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the claimed subject matter to those skilled in the art. The embodiments described herein are not to be interpreted in any way as limiting the scope of the claimed subject matter.
As used in the specification and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly indicates otherwise. For example, reference to “a film” includes a plurality of such films.
It will be understood that relative terms, such as “preceding” or “followed by” or the like, may be used herein to describe one element's relationship to another element as, for example, may be illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the elements in addition to the orientation of elements as illustrated in the Figures. It will be understood that such terms can be used to describe the relative positions of the element or elements and are not intended, unless the context clearly indicates otherwise, to be limiting.
Embodiments are described herein with reference to various perspectives, including, for example, perspective views that are representations of idealized version of the embodiments. As a person having ordinary skill in the art would appreciate, variations from or modifications to the shapes as illustrated in the Figures or the described perspectives are to be expected in practicing the disclosed subject matter. Such variations and/or modifications can be the result of manufacturing techniques, design considerations, and the like, and such variations are intended to be included herein within the scope of the presently disclosed subject matter and as further set forth in the claims that follow. The articles disclosed herein and their respective components described or illustrated in the Figures are not intended to reflect a precise description or shape of the component of an article and are not intended to limit the scope of the claimed subject matter.
Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. All terms, including technical and scientific terms, as used herein, have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed subject matter belongs unless a term has been otherwise defined. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning as commonly understood by a person having ordinary skill in the art to which the disclosed subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure. Such commonly used terms will not be interpreted in an idealized or overly formal sense unless the disclosure herein expressly so defines otherwise.
The embodiments described herein relate to a heat-shrinkable opaque film or a microlayer. In certain embodiments, the microlayer comprises a pigment. In preferred embodiments, the pigments comprise submicron particles having particle sizes in the nanometer range. In certain embodiments, the opacity of the microlayer is greater than about 90%. In certain embodiments, the thickness of the microlayer is less than about 1.5 mils. In an embodiment, the pigment may comprises one of carbon black or titanium dioxide for forming a black and white colored film, respectively. In certain embodiments, a combination of carbon black and titanium dioxide may be used to achieve a desired gray-scale color level for the film.
As used herein, the term “submicron particles” refers to particles having an average diameter of less than 1 micron.
In an embodiment, the multilayers described herein may be extruded using a micro-layering process as further described herein. Without intending to be bound by the theory, the multilayers of the embodiments described herein generally provide films having improved resistance for product protection and leads to packing integrity of wrapped products. The smaller size of the CRYOVAC® CT films also results in a more sustainable packaging solution including a reduced carbon footprint as a result of reduced material usage to achieve the needed packaging effect, a reduction in the amount of waste materials from packaging operations, and an energy saving as a result of lower tunnel and sealing temperature required in the packaging operation.
The microlayers described herein have been found to be of particular importance in the CRYOVAC CT series of films. The CRYOVAC CT series of films provides a relatively new technological capability within the packing industry by incorporated discrete microlayers within the film leading to films having good strength properties and enhanced performance capability in comparison to thicker conventional shrink films. When used in the CRYOVAC CT films, the multilayers described herein provide improved resistance for product protection and leads to packing integrity of wrapped products. The smaller size of the CRYOVAC CT films also results in a more sustainable packaging solution including a reduced carbon footprint as a result of reduced material usage to achieve the needed packaging effect, a reduction in the amount of waste materials from packaging operations, and an energy saving as a result of lower tunnel and sealing temperature required in the packaging operation.
A plurality of layers may be coextruded with the use of a die and one or more extruders in fluid communication with the die. The one or more extruders are configured to supply one or more fluidized polymers to the die. The one or more extruders are maintained at a temperature sufficient to keep the contents of each extruder in a molten state. Internal screws within the extruder may act to move the molten polymer into and through the die via tubes or pipes. The die converts the molten contents received from each of the one or more extruders into thin film layers with each layer being superimposed, combined together and then expelled through the discharge of the die to a coextruded. Upon exiting the die, the coextruded film is subjected to cooling causing the film to transform into a solid state. Such cooling may be achieved by subjecting the film to ambient air and/or quenching the film in a liquid quench bath.
A die is generally configured to have any number of distribution plates that function as a fluid inlet and a fluid outlet that deposits the existing formed film from the fluid outlet onto a primary forming stem. The fluid is directed through a channel of the distribution plate that progressively become more shallow causing the fluid to assume a thinner formed profile.
The fluid layers received from the distribution plates may be deposited on the primary forming stem either directly or indirectly disposed on already deposited films. The formed film emerges from the die at a discharge end or through what is also known as the “die lip.” The thickness of the formed films may be further decreased through an annular passage as the film exits the die.
A microlayer assembly comprises a microlayer forming stem along with a plurality of microlayer distribution plates. Each of the microlayer plates has a fluid inlet and a fluid outlet whereby the fluid inlet is in fluid communication with a microlayer forming stem and is configured to deposit a microlayer of fluid onto the microlayer forming stem.
The channel of the microlayer plates may be spiral-shaped, for example; however, other channel configurations may be employed including, but not limited to, a toroid-shaped channel, an asymmetrical toroid channel, a heart-shaped channel, and a helical-shaped channel. The channel may have a semi-circular or semi-oval cross-section or may have a fuller shape such as an oval or circular cross-sectional shape.
A fluid flow passing through the microlayer assembly is converted from a generally stream-like, axial flow to a generally film-like, convergent radial flow as it progresses to the microlayer forming stem. This may be accomplished, for example, by a channel that spirals towards the center of the plate thus directing fluid from the fluid inlet located at the periphery of a microlayer plate to an outlet that is proximate to the center of the plate. Alternatively, the channel may have a progressively shallower depth as the channel forms to the fluid outlet effectively causing a portion of the fluid flowing through the channel to overflow the channel through overflow regions and then proceeding radial-inward toward the fluid outlet in a relatively flat, film-like flow. The fluid outlet provides a relatively narrow fluid-flow passage, which influences the thickness of the formed microlayer flowing from the microlayer plate.
The microlayer assembly may be located relative to the distribution plates to provide for the needed location of the one or more microlayers in the formed film. For example, the microlayer assembly may be positioned between one or more upstream distribution plates. In other embodiments, a plurality of microlayers may be deposited throughout a finished film by using a plurality of microlayer assemblies.
A more detailed description of coextrusion techniques can be found in U.S. Pat. No. 8,012,572 entitled “Multilayer, Heat-Shrinkable Film Comprising a Plurality of Microlayers,” the contents of which are incorporated herein by reference in their entirety.
In an embodiment, the multilayer film includes microlayers substantially free of pigments, which results in a multilayer film that is substantially free of any opacity or substantially free of any color. In another embodiments, the multilayer film includes microlayers having pigments allowing the multilayer film to become opaque and/or allowing a color to be imparted to the multilayer film.
In an embodiment, either or both of the inner layer and/or the outer layer may comprise from about 30 wt % to about 60 wt % linear low density polyethylene, form about 15 wt % to about 30 wt % medium density polyethylene, from about 15 wt % to about 40 wt % ethylene vinyl acetate copolymer (including up to about 2.5% vinyl acetate in one embodiment, up to about 5% vinyl acetate in another embodiment, or up to about 10% vinyl acetate in yet another embodiment), from about 2 wt % to about 20 wt % of an ethylene octene copolymer (having less than a 10% octene, less than about 6% octene or less than about 2.5% octene in varying embodiments), and from about 0.5 wt % to about 2.5 wt % additives, or about 1 wt %+/−0.1 wt % additives in a preferred embodiment. In certain embodiments, the additives comprise an antiblock agent, a slip agent, an antiblock/slip agent, and any combination thereof.
In an embodiment, a substrate comprises a resin having from about 30 wt % to about 60 wt % linear low density polyethylene, from about 15 wt % to about 30 wt % medium density polyethylene, from about 15 wt % to about 40 wt % ethylene vinyl acetate copolymer (including up to about 2.5% vinyl acetate in one embodiment, up to about 5% vinyl acetate in another embodiment, or up to about 10% vinyl acetate in yet another embodiment), and from about 2 wt % to about 20 wt % ethylene octene copolymer (having less than a 10% octene, less than about 6% octene or less than about 2.5% octene in varying embodiments).
In an embodiment, the microlayer comprises a resin and a pigment. In certain embodiments, the microlayer is constructed to provide a film that is black in color. Further pursuant to this embodiment, the pigment comprises from about the resin comprises from about 5 wt % to about 25 wt % of carbon black. Even further pursuant to this embodiment, the resins comprise from about 30 wt % to about 60 wt % linear low density polyethylene, from about 0 wt % to about 20 wt % low density polyethylene, from about 10 wt % to about 30 wt % medium density polyethylene, and from about 2.5 wt % to about 20 wt % ethylene octene copolymer (having less than a 10% octene), less than about 6% octene or less than about 2.5% octene in varying embodiments).
According to the embodiments where the microlayer is constructed to provide a film that is white in color, the pigment comprises from about 5 wt % to about 25 wt % of titanium dioxide. In embodiments wherein the microlayer is constructed to provide a film that is gray in color, the pigment comprises a combination of from about 5 wt % to about 20 wt % carbon black and about 5 wt % to about 20 wt % titanium dioxide.
Without intending to be bound by theory, ethylene vinyl acetate (EVA) is an elastomeric polymer that, in the proper concentration, provides a softness and flexibility to the film in which it appears. Similarly, ethylene octene copolymer may function as an elastomeric material. Thus, there combination may be referred to as an elastomeric polymer. More generally, in an embodiment, the microlayer may comprise from about 55 wt % to about 80 wt % of a polyethylene, from about 2.5 wt % to about 20 wt % of an elastomeric copolymer, and from about 5 wt % to about 25 wt % of a pigment.
In some embodiments, microlayers may comprise a pigment used for the manufacture of opaque films. In one embodiment, the microlayer comprises a pigment that provides a black color to the finished film. Further pursuant to this embodiment, the pigment comprises a carbon black. Yet even further pursuant to this embodiment, the carbon black includes particles having particle sizes ranging from about 25 nanometers to about 200 nanometers in diameter. In still other embodiments, the carbon black particles have an average particle size ranging from about 25 nanometers to about 200 nanometers in diameter. The selected sizes of the particles are such that they are smaller than the thickness of the microlayer allowing for homogeneous dispersion as well as improved film properties. In certain embodiments, the D50 or median value of the carbon blank particles ranges from about 57.2 nm to about 72.4 nm or from about 63.6 nm to about 65.8 nm, a mean value of the carbon black particles ranges from about 60.0 nm to about 78.7 nm or from about 66.7 nm to about 71.0 nm, and a standard deviation ranging from about 25.8 nm to about 32.1 nm. The concentration of carbon block having particle sizes in these nanometer ranges is from about to about 2 wt % to about 25 wt %, from about 5 wt % to about 20 wt %, from about 9 wt % to about 16 wt %, or from about 10 wt % to about 15 wt % in the microlayer.
In another embodiment, the microlayer comprises a pigment that provides a white color to the finished film. Further pursuant to this embodiment, the pigment comprises titanium dioxide (TiO2). Yet even further pursuant to this embodiment, the TiO2 includes particles having particle sizes ranging from about 54 nanometers to about 390 nanometers in diameter. In still other embodiments, the TiO2 particles have an average particle size ranging from about 54 nanometers to about 390 nanometers in diameter. The selected sizes of the particles are such that they are smaller than the thickness of the microlayer allowing for homogeneous dispersion as well as improved film properties. In certain embodiments, the D50 or median value of the TiO2 particles ranges from about 137.5 nm to about 169.2 nm or from about 152.8 nm to about 153.9 nm, a mean value of the TiO2 particles ranges from about 154.0 nm to about 177.9 nm or from about 160.1 nm to about 161.7 nm, and a standard deviation ranging from about 68.1 nm to about 68.5 nm. The concentration of TiO2 having particle sizes in these nanometer ranges is from about to about 5 wt % to about 30 wt %, from about 10 wt % to about 25 wt %, or from about 15 wt % to about 20 wt % in the microlayer.
In yet another embodiment, the microlayer comprises a pigment that provides a gray color to the finished film. Further pursuant to this embodiment, the pigment comprises a carbon black and TiO2. Yet even further pursuant to this embodiment, the carbon black includes particles having particle sizes ranging from about 25 nanometers to about 200 nanometers in diameter and the TiO2 includes particles having particle sizes ranging from about 54 nanometers to about 390 nanometers in diameter. In still other embodiments, the carbon black particles have an average particle size ranging from about 25 nanometers to about 200 nanometers in diameter and the TiO2 particles have an average particle size ranging from about 54 nanometers to about 390 nanometers in diameter. The selected sizes of the particles are such that they are smaller than the thickness of the microlayer allowing for homogeneous dispersion as well as improved film properties. In an embodiment, the weight ratio of the carbon black to the TiO2 is from about 1:4 to about 4:1, from about 1:3 to about 3:1, or from about 1:2 to about 2:1. In an embodiment, the preferred weight ration of the carbon black to the TiO2 is about 1:2.
While carbon black and TiO2 are shown to be the pigments in these representations, these are only exemplary in nature. Rather, any type of pigment that may impart any color to the finished film may be used. Pigment, in non-limiting examples, may comprise azo compounds having the function group of RN═NR′, and quinacridones-C20H12N2O2. For example, the pigment may comprise one or more compounds that provide a purple hue including, but not limited to, a silicate of sodium and aluminum containing sulfur, BaCuSi2O6, cobaltous orthophosphate, manganic ammonium phosphate-NH4MnP2O7, iron(III) oxide-Fe2O3, and dioxazine family of heterocyclic compounds.
The pigment may comprise one or more compounds that provide a blue hue including, but not limited to, a sulfur containing sodium-silicate-Na6-10Al6Si6O24S2-4, calcium copper silicate-CaCuSi4O10, barium copper silicate-BaCuSi4O10, ferric hexacyanoferrate-Fe7(CN)18, the general formula YIn1-xMnxO3, indigo-C16H10N2O2., and copper phthalocyanine.
The pigment may comprise one or more compounds that provide a green hue including, but not limited to, cupric carbonate hydroxide-Cu3(CO3)2(OH)2, cupric carbonate hydroxide-Cu2CO3(OH)2, cupric acetoarsenite-Cu(C2H3O2)2.3Cu(AsO2)2, cupric arsenite-CuHAsO3, cupric acetate-Cu(CH3CO2)2, malachite-Cu2CO3(OH)2, chromic oxide-Cr2O3, combination of CdS and chromic oxide, and hydrated chromic oxide-Cr2O3.H2O.
The pigment may comprise one or more compounds that provide a yellow hue including, but not limited to, monoclinic arsenic sulfide-As2S3, cadmium sulfide-CdS, plumbous chromate-PbCrO4, potassium cobaltnitrite-Na3Co(NO2)6, monohydrated ferric oxide-Fe2O3.H2O, lead stannate-Pb2SnO4, silicate of lead tin oxide-Pb(SnSi)O3, titanium-based pigments providing a yellow coloration-NiO.Sb2O3.20TiO2, stannic sulfide-SnS2, compounds produced through the azo coupling of aniline, acetoacetanilide or derivatives thereof, diarylide pigment, euxanthic acid-C19H16O10, monoazopyrazolone-C16H12Cl2N4O, derivative of isoindoline-C16H9N5O6, and bisacetoacetarylide-C34H28Cl4N6O4.
The pigment may comprise one or more compounds that provide an orange hue including, but not limited to, cadmium sulfoseleniode-CdSe, a combination of lead(II)chromate and lead(II) oxide-PbCrO4 and PbO, and dibromoanthanthrone-C22H8BR2O2 (provides a redish-orange hue).
The pigment may comprise one or more compounds that provide a red hue including, but not limited to, cadmium selenide-CdSe, anhydrous iron oxide-Fe2O3, lead tetroxide-Pb3O4, mercuric sulfide-HgS, 1,2-dihydroxyanthraquinone-C14H8O4, naphthol red-C26H22, N4O4, and perinone-C26H12N4O2.
The pigment may comprise one or more compounds that provide a brown hue including, but not limited to, the combination of iron oxide, manganese oxide and aluminum oxide-Fe2O3 and MnO2 and AlO3, limonite clay, and bistre brown.
The pigment may comprise one or more compounds that provide a black hue including, but not limited to, carbon based pigments including carbon black, ivory black, vine black, lamp black; iron oxide-Fe3O4, and titanium(III) oxide-Ti2O3.
The pigment may comprise one or more compounds that provide a white hue including, but not limited to, stibous oxide-Sb2O3, barium sulfate-BaSO2, plumbous carbonate-(PbCO3)2.Pb(OH)2, titanium oxide-TiO2, and zinc oxide-ZnO.
Various naturally occurring pigments may also be use including, but not limited to, anthoxanthin (pigments from plants), gamboge (resin from certain evergreen trees), and madder lake (extract from madder plants).
Chapter 11 entitled “Colorants, Part I: Pigments and Dyes” written by Dr. E. Herrmann and Dr. W. Damm in the book entitled Plastics Additives Handbook, 4th ed., edited by R. Gachter and H. Muller, Hanser/Gardner Publications, Inc., published in Cincinnati in 1996, which is included by reference in its entirety herein, identifies pigments in Tables 4-7.
Of course, as a person of ordinary skill in the art would understand having the benefit of this disclosure, any combination of these compounds may be used to provide a desired color hue. Preferably, any of these compounds used in the microlayer will be in particle form having small diameters relatively similar to those disclosed herein for carbon black and/or TiO2. The pigment comprises a submicron silica pigment in certain embodiments. For example the SYLOJET® A-Series or C-Series comprise such submicron particles.
The identified particle sizes of the particles making up the pigment provide a finished film having a good opacity—greater than about 80%, preferably, greater than about 90%—and a high Elmendorf tear strength. Indeed, the use of particle sizes of the pigment in the specified ranges has been demonstrated to provide a finished film opacity that is uniform and consistent across the film.
In yet even another embodiment, the microlayer comprises a pigment that provides any color other than black, white or gray to the finished film. Further pursuant to this embodiment, the pigment comprises particles having a smaller size within the nanometer range that provides a high degree of opacity—greater than about 80%, preferably, greater than about 90%—and provide a good Elmendorf tear strength to the finished film.
While a thickness of the finished film is dependent upon the number of layers, in particular, the number of microlayers included in the film, a film characterized by an inner skin and an outer skin with each having a substrate layer in which a core layer having about 25 microlayers disposed will have a thickness ranging from about 40 gauge to about 300 gauge, from about 50 gauge to about 250 gauge, from about 60 gauge to about 200 gauge, or from about 70 gauge to about 150 gauge. In preferred embodiments, the film thickness is 90 gauge or higher. A 90 gauge film, for example, without intending to be bound by theory, offers a good carbon footprint in balance with certain physical properties of the film.
In some embodiments, finished films comprising a microlayer have a clarity ranging from about 0% to about 20%, from about 0% to about 10%, from about 0% to about 5%, from about 0% to about 1%, or from about 0% to about 0.2%. In some embodiments, the finished films comprising a microlayer have a gloss ranging from about 25% to about 75%, from about 40% to about 60%, or from about 47% to about 52%.
In some embodiments, finished films comprising a microlayer have a coefficient ranging from about 0.100 to about 0.200, from about 0.110 to about 0.180, or from about 0.116 to about 0.163. In some embodiments, finished films comprising a microlayer have a moisture vapor transmission rate (MVTR) ranging from about 0.30 g/100 in2/day/atm to about 1.4 g/100 in2/day/atm, from about 0.40 g/100 in2/day/atm to about 1.3 g/100 in2/day/atm, from about 0.51 g/100 in2/day/atm to about 1.1 g/100 in2/day/atm, or from about 0.70 g/100 in2/day/atm to about 1.1 g/100 in2/day/atm
In some embodiments, finished films comprising a microlayer have an oxygen transmission rate (OTR) ranging from about 2,000 cc/100 in2/day/atm to about 10,000 cc/100 in2/day/atm, ranging from about 3,000 cc/100 in2/day/atm to about 9,000 cc/100 in2/day/atm, ranging from about 3,085 cc/100 in2/day/atm to about 8,000 cc/100 in2/day/atm, or ranging from about 4,355 cc/100 in2/day/atm to about 8,000 cc/100 in2/day/atm
In some embodiments, finished films comprising a microlayer have a longitudinal direction (LD) tensile strength ranging from about 10,000 psi to about 25,000 psi, ranging from about 12,500 psi to about 22,500 psi, ranging from about 14,900 psi to about 19,800 psi, or ranging from about 15,700 psi to about 19,800 psi. In some embodiments, finished films comprising a microlayer have a transverse direction (TD) tensile strength ranging from about 10,000 psi to about 25,000 psi, ranging from about 12,500 psi to about 22,500 psi, ranging from about 13,900 psi to about 20,300 psi, or ranging from about 15,100 psi to about 20,300 psi.
In some embodiments, finished films comprising a microlayer have a LD elongation at break ranging from about 80% to about 250%, ranging from about 100% to about 200%, ranging from about 120% to about 180%, or ranging from about 150% to about 180%. In some embodiments, finished films comprising a microlayer have a TD elongation at break ranging from about 75% to about 225%, ranging from about 100% to about 200%, ranging from about 99% to about 180%, or ranging from about 140% to about 160%.
In some embodiments, finished films comprising a microlayer have a LD modulus ranging from about 40,000 psi to about 100,000 psi, ranging from about 50,000 psi to about 90,000 psi, ranging from about 43,600 psi to about 77,100 psi, or ranging from about 60,600 psi to about 77,100 psi. In some embodiments, finished films comprising a microlayer have a TD modulus ranging from about 40,000 psi to about 100,000 psi, ranging from about 45,000 psi to about 95,000 psi, ranging from about 47,500 psi to about 88,600 psi, or ranging from about 66,800 psi to about 88,600 psi.
In some embodiments, finished films comprising a microlayer have a LD Elmendorf tear ranging from about 5.0 g to about 50.0 g, ranging from about 10.0 g to about 45.0 g, ranging from about 11.6 g to about 35.0 g, or ranging from about 28.3 g to about 35.0 g. In some embodiments, finished films comprising a microlayer have a TD Elmendorf tear ranging from about 5.0 g to about 50.0 g, ranging from about 10.0 g to about 40.0 g, ranging from about 13.1 g to about 33.3 g, or ranging from about 27.9 g to about 33.3 g. In certain embodiments, the films described herein have a Elmendorf tear greater than about 10 g.
In some embodiments, finished films comprising a microlayer have a LD shrink tension @ 200° F. ranging from about 200 psi to about 400 psi, ranging from about 225 psi to about 375 psi, ranging from about 246 psi to about 340 psi, or ranging from about 283 psi to about 340 psi. In some embodiments, finished films comprising a microlayer have a TD shrink tension @ 350° F. ranging from about 300 psi to about 650 psi, ranging from about 350 psi to about 600 psi, ranging from about 410 psi to about 572 psi, or ranging from about 536 psi to about 572 psi.
In some embodiments, finished films comprising a microlayer have a LD free shrink @ 200° F. ranging from about 5% to about 20%, ranging from about 7% to about 17%, from about 9% to about 14%, or ranging from about 11% to about 14%. In some embodiments, finished films comprising a microlayer have a TD free shrink @ 200° F. ranging from about 10% to about 25%, ranging from about 12% to about 23%, ranging from about 15% to about 21%, or ranging from about 16% to about 21%.
Test Methods:
The peak load measured in lbs is reflective of the impact strength. Impact strength is measured according to ASTM D3763 the “Standard Test Method for High Speed Puncture Properties of Plastics.”
Clarity is the optical distinctness through which an object can be seen when viewed through a film. Clarity depends upon the linearity of the passage of light rays through the material of the film. Small deflections of light caused by scattering regions of the material cause a deterioration of the image quality. Clarity is measured according to ASTM D1746 the “Standard Test Method for Transparency of Plastic Sheeting” using a Zebedee Model CL 100 clarity meter. This instrument is design to measure the extent of transparency whenever distinctiveness of image is an important attribute.
Gloss is a visual impression resulting from an evaluation of the surface of the film. The more direct light is reflected from the surface, the more obvious the impression of gloss will be. Smooth and highly polished surfaces more readily reflect images. If a surface is rough, the light is diffusely scattered in all directions causing the image forming qualities to be diminished. Gloss is measured according to ASTM D2457 the “Standard Test Method for Specular Gloss of Plastics Films and Solid Plastics” using a BYK-Gardner model 4535 gloss meter.
The transparency of a product is influenced by the absorption and scattering behavior of the film. Visual transparency is described by clarity as further disclosed herein and haze. Optical haze is related to the ratio of transmitted light that deviates from the normal direction by more than about 4 degrees relative to the total transmitted light. Haze & total transmission is measured according to ASTM D1003 the “Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics” using the BYK-Gardner model 4725 Haze-Gard Plus instrument.
Opacity measures the degree to which a film obscures a pattern passing through it. An opaque material will have 100% opacity, while a near-opaque film is typically above 80% opacity and often above 90% opacity. Color/opacity is measured according to ASTM D6290 the “Standard Test Method for Color Determination of Plastic Pellets”. For example, a Hunter Lab spectrophotometer may be used to measure the degree of color and the extent of opacity of a film. Alternatively, opacity may indirectly be calculated as 100−% Total Transmission.
Particle sizes of pigments are measured using a scanning electron microscope (SEM) at very high magnifications of up to 100,000× of the pellets.
Various examples of the subject matter include a microlayer and films comprising such a microlayer. Specific examples of the concept will now be described. The examples that follow are provided only for illustrative purposes only.
The film structure for the test samples includes 29 layers with layers 1 and 29 being the outer skins, layers 2 and 28 being the substrates. Table 1 identifies the general film structure for the test samples of the examples.
Layers 3-27 is a 25 layer core structure having alternating microlayer A (13 of the 25 layers) and microlayer B (12 of the 25 layers)
A black masterbatch having codename CHAR with 50 wt % polymer/copolymer resin and 50 wt % carbon black was used in the test samples of the example. The carbon black particles of CHAR had diameters in the range of 25 to 200 nanometers. The size of the particles can be determined from a scanning electron microscope image.
A white masterbatch having codename ZODI having 50 wt % polymer/copolymer resin and 50 wt % titanium dioxide (TiO2) was used in the test samples of the example. The TiO2 particles of ZODI had diameters in the range of 54 to 390 nanometers.
Table 2 provides an extensive sampling of the particle sizes for the carbon black in
Table 3 provides an extensive sampling of the particle sizes for the TiO2 in
Antiblock and slip agents of the outer skin includes a proprietary combination of amorphous silicon, N,N′ ethylene-bis-stearamide, oleamide wax, and erucamide wax. The antiblock agent of the outer skin, in particular, is alkali-alumino-silicate ceramic spheres. x % is the percentage of CHAR used in the microlayers of the core, and y % is the percentage of ZODI used in the microlayers of the core. The antiblock agent of the substrate is anhydrous aluminum silicate. The slip1 agent of the substrate layer comprises N,N′ ethylene-bis-stearamide, while the slip2 agent is erucamide wax and the slip3 agent is oleamide.
Table 4 provides exemplary compositions of the layers of a film according to an embodiment using a carbon black pigment to provide a black film.
In constructing the sample films of these examples, EF437AA from Westlake Chemical was used to for the ethylene vinyl acetate copolymer having 2.5% vinyl acetate. DOWLEX™ 2037 masterbatch resin from Dow Chemical Company was used for the medium density polyethylene having ethylene octene copolymer. The copolymer of this masterbatch has about 2.5% comonomer content, a density of about 0.935 g/cm3, and about a 124.7° C. melting point. DOWLEX 2045.05 masterbatch resin from Dow Chemical Company was used to provide the linear low density polyethylene having ethylene octene copolymer. The copolymer of this masterbatch has about 6.5% comonomer content, a density of about 0.920 g/cm3, and about a 124° C. melting point.
Table 5 provides exemplary compositions of the layers of a film according to another embodiment using a titanium dioxide pigment to provide a white film.
Table 6 provides exemplary compositions of the layers of a film according to yet another embodiment using both a carbon black and titanium dioxide pigments to provide a gray film.
The sample films prepared using the carbon black-based masterbatch (CHAR) in the microlayers are listed in Table 7.
Notably, the opacity of all of the films having between about 20 wt % and about 30 wt % of the masterbatch having carbon black (from about 10 wt % to about 15 wt % carbon black) has an opacity of about 100%. As shown in Example 5, even films having a combination of about 10 wt % of the masterbatch containing carbon black and 20 wt % of the masterbatch with the white-based pigment—e.g., titanium dioxide—still demonstrate an opacity of about 100%. The total combination of pigments in Example 5 is about 5 wt % carbon black and about 10 wt % of titanium dioxide.
Other properties of the films having the carbon black-based masterbatch in the microlayers as shown in Table 7 are identified in Table 8.
The sample films prepared using the TiO2-based masterbatch (ZODI) in the microlayers are listed in Table 9.
As shown in Table 9, the masterbatch having the white-based pigment—TiO2 in this case—results in opacities that are on the order of from about 57% to about 67%. While the microlayers of Example 8 have 40 wt % of the TiO2-based pigment, as shown in Example 7, even if Microlayer B includes 40 wt % of the masterbatch having the carbon black pigment, the opacity only slightly increases from 57% to 67% when Microlayer A includes 40 wt % of the masterbatch having the TiO2-based pigment.
Generally, the 90 gauge film appears to offer suitable coefficient of friction, moisture vapor transmission rate (MVTR), oxygen transmission rate (OTR), tensile strength, % elongation at break, modulus and shrink tension and free shrink numbers when balanced against the film thickness. This somewhat excellent performance at a much thinner film reduces the amount of required polymers/plastic and improves the carbon footprint of the film.
Other properties of the films having the TiO2-based masterbatch in the microlayers as shown in Table 9 are identified in Table 10.
In order to see if the opacities would improve by stacking a film having a high opacity to a film having a lower capacity, the sample stacked films prepared as shown in Table 11 were tested.
As shown in Table 11, the opacity of a stacked film significantly improves to on the order of 99% or more by including one of the films having microlayers that include the masterbatch having the carbon black-based pigment even though the other film has microlayers that include the masterbatch having the TiO2-based pigment.
The variation in clarity relative to the concentration of the masterbatch having the carbon black pigment in the microlayer was determined.
The results of these tests are provided in Table 12 with a graphical representation shown in
Variations in film thickness will dictate the amount of masterbatch required in the microlayers to achieve 100% opacity. The concentration of the masterbatch having the carbon black pigment in the microlayer required to achieve 100% opacity based upon the thickness of the film was determined. The results of these tests are provided in Table 13 with a graphical representation shown in
Ship tests were performed on various films using the core layer microlayer technology. In these sets of tests, the microlayers were substantially free of any pigment resulting in a substantially clear film lacking any color.
Film type, bag type and product type test factors were each evaluated in these tests. Four film types were tested including the CORTUFF® high-abuse shrink film manufactured using a coextrusion process and three films using the microlayer including CT308, a 150 gauge film; CT306, a 90 gauge film, and CT304, a 55 gauge film. It should be noted that while the CORTUFF film was opaque, the microlayer based films of these tests were clear for comparative purposes. The bag types included full shrink (film contacts 100% of surface of packaged product), partial shrink (double speed through shrink tunnel) and no shrink (loose bag having 1″ between edge of packaged product and outside edge of film bag) bag types while the packaged product type included rigid (12″×11″×¾″ wood pine block), semi-rigid (14″×14″×2″ chipboard apparel box), and soft (15″×¼″ folded dunnage paper).
The test included four replicates resulting in 144 total test packs to encompass each combination of the test factors. The packs were shipped out of one location and sent to two distant locations, and, once received, returned to the originating location. Handling of the packages as well as the number and types of hubs they passed through affected the package condition once it was received at the final destination. Nineteen of the 144 test packs were lost in transit, which may have been due, at least in part, to the packaging from the labeled shipped item being accidentally removed from the item.
An overall film performance factor was calculated based upon the evaluated conditions of the wrapped corners (36.4% contribution), the wrapped seals (27.3% contribution), and the wrapped face (36.4% contribution), while an overall packaging performance factor was calculated based upon the evaluated condition of the product crush (40% contribution), product tear (30% contribution), and product scuff (30% contribution). A score of five (5) is the best score available. Anything less indicates there were performance problems with either the film or problems encountered with the packaged product. Table 14 provides the average responses for each of the packages received back in the test—typically four, but some with three, and a few having two due to lost packages (the latter typically have lower average responses anyway indicating it is likely the packaging on the missing samples were damaged while in shipment).
The following general observations were made based upon the results of this testing: (i) while the CORTUFF film performed well in comparison to the films including a microlayer they are limited from the standpoint that the film is 2 mils or greater in thickness leading to more difficulty in processing and requires mechanical folding; (ii) full shrunk bags offer only slight compression protection since the product has a more difficult time expanding upon application of a crushing force; (iii) full shrunk bags are more prone to wholes due to scuffing since the film remains in the same position at all times during transport; (iv) the films offer opaque films allowing for product concealment; (v) 100% opacity is achieved in all films having thickness greater than or equal to 70 gauge; (vi) the films offer good sealability and shrink film properties; (vii) overall, CT304, the 55 gauge film, did not perform as well as the thicker films; and (viii) in terms of overall properties and packaging effectiveness, the minimum film thickness for packaging applications is about 90 gauge.
Ship tests were performed on various films using the core layer microlayer technology. In these sets of test, the microlayers were comprised a pigment resulting in a in an opaque film having a black color.
Film type, bag type and product type test factors were each evaluated in these tests. Two film types were tested including a 90 gauge film and an 115 gauge film. All bags were full shrink (film contacts 100% of surface of packaged product). The packaged product type included a tall cardboard shoebox and a short cardboard shoe box.
Performance factors were calculated in the same way as explained in Example 6. Table 15 provides the average responses for each of the packages received back in the test (four for each film type and packaged box size).
Films have a thickness of 90 gauge or greater are expected to perform reasonably well. While the 115 gauge film performed better than the 90 gauge film, the performance of the 90 gauge film was deemed acceptable.
Many modifications and other embodiments of the embodiments set forth herein will come to mind to one skilled in the art to which the disclosed subject matter pertains having the benefit of the teachings presented in the descriptions herein and the associated drawings. It will be appreciated by those skilled in the art that changes could be made to the embodiments described herein without departing from the broad inventive concepts thereof. Therefore, it is understood that this claimed subject matter is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present disclosure as defined by the included claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/045215 | 8/3/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62370258 | Aug 2016 | US |
