WO2020139499A1

WO2020139499A1 - Multilayer metallized cast polypropylene films doped with hydrocarbon resin

Info

Publication number: WO2020139499A1
Application number: PCT/US2019/062996
Authority: WO
Inventors: Lanya Cheng; Etienne R. LERNOUX
Original assignee: Exxonmobil Chemical Patents Inc.
Priority date: 2018-12-26
Filing date: 2019-11-25
Publication date: 2020-07-02

Abstract

A multilayer metallized cast polypropylene films can include a doped metallization layer comprising about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin; and a metal layer on a first surface of the doped metallization layer. The film can further include a sealant layer; and a core layer between the doped metallization layer and the sealant layer, wherein the core layer is on a second surface of the doped metallization layer that opposes the first surface of the doped metallization layer.

Description

MULTILAYER METALLIZED CAST POLYPROPYLENE FILMS DOPED WITH

HYDROCARBON RESIN

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S.S.N. 62/784,873, filed December 26, 2018, herein incorporated by reference.

FIELD

[0002] This disclosure relates generally to multilayer metallized polypropylene films doped with hydrocarbon resin.

BACKGROUND

[0003] Metallization is often used in the flexible packaging application, in order to enhance the barrier of packaging to the permeation of gas such as oxygen, nitrogen, or water vapor. The metallization of a film is typically performed by vacuum deposition in a metallizing unit, and the metal coating is typically aluminum. The main polymeric films that are commercially available in metallized form are bi-oriented polyester (BOPET), bi-oriented polypropylene (BOPP), and cast polypropylene (cPP).

[0004] The gas barrier improvement from the metal layer is particularly useful for food packaging because it slows down the degradation of the food caused by interactions with external gases that would otherwise permeate into the packaging. Further, the metal layer can also protect the food by keeping a modified atmosphere, for instance nitrogen, inside the packaging for a longer time. Decreasing gas permeation of packaging is vital for any food producer and packer to mitigate the loss of product freshness and to extend its shelf-life.

[0005] The effectiveness of a metal layer to enhance the barrier performance is a very complex phenomenon that depends on several parameters including the smoothness of the layer receiving the metal coating, the level of treatment of the layer, the chemical composition of the layer, and the amount of metal applied to the layer. The ability of the metallized film to preserve its barrier performance while going through the different steps of the supply chain, such as lamination and packaging, is also highly critical.

[0006] In summary, limiting the gas permeation of film is very important for many flexible packaging applications and the industry of metallized films has been continuously working on improving the barrier performance to further extend packaging shelf-life.

[0007] Another concern often raised with metallized films is the fact that the surface of the metal layer, over time, loses some of its receptivity to additional coatings such as inks, primers, or adhesives. Accordingly, manufacturers often have limited time between metallizing and packaging, which reduces manufacturing timeline flexibility. SUMMARY

[0008] This disclosure relates generally to multilayer metallized cast polypropylene films where the layer that is metallized comprises a hydrocarbon resin blended with a propylene copolymer.

[0009] An example embodiment of the present invention is a multilayer metallized cast polypropylene films comprising: a doped metallization layer comprising about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin; and a metal layer on a first surface of the doped metallization layer. The film can further comprise: a sealant layer; and a core layer between the doped metallization layer and the sealant layer, wherein the core layer is on a second surface of the doped metallization layer that opposes the first surface of the doped metallization layer.

[0010] Another example embodiment is a method comprising: casting a doped metallization polymer melt to form a doped metallization layer, wherein the doped metallization polymer melt comprises about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin; and metallizing a first surface of the doped metallization layer to form a multilayer film. The method can comprise: casting a core polymer melt and a sealant polymer melt with the doped metallization polymer melt to form a film with a core polymer layer between the doped metallization layer and a sealant polymer layer, wherein after metallizing the core layer is on a second surface of the doped metallization layer that opposes the first surface of the doped metallization layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following figures are included to illustrate certain aspects of the embodiments, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.

[0012] FIG. 1 is a first example of a metallized cast multilayer polypropylene film of the present invention.

[0013] FIG. 2 is a second example of a metallized cast multilayer polypropylene film of the present invention.

[0014] FIG. 3 illustrates the surface tension changes over time for example metallized cast multilayer polypropylene films according to the structure of FIG. 2.

DETAILED DESCRIPTION

[0015] This disclosure relates generally to multilayer films comprising a doped metallization layer with a metal layer thereon, wherein the doped metallization layer comprises polypropylene copolymer doped with a hydrocarbon resin. Such films may be used for packaging (e.g., food packaging) applications.

Definitions

[0016] The term“polymer” as used herein includes, but is not limited to, homopolymers, copolymers, etc., and alloys and blends thereof. The term“polymer” as used herein also includes impact, block, graft, random, and alternating copolymers. The term“polymer” shall further include all possible geometrical configurations unless otherwise specifically stated. Such configurations may include isotactic, syndiotactic, and random symmetries.

[0017] As used herein, unless specified otherwise, the term“copolymer(s)” refers to polymers formed by the polymerization of at least two different monomers. For example, the term“copolymer” includes the copolymerization reaction product of propylene and an alpha- olefin, such as ethylene, 1 -hexene. However, the term“copolymer” is also inclusive of, for example, the copolymerization of a mixture of propylene, ethylene, 1-hexene, and 1-octene. Another example propylene copolymer includes monomer units derived from propylene, ethylene, and butene.

[0018] As used herein, when a polymer is referred to as“comprising a monomer,” the monomer is present in the polymer in the polymerized form of the monomer or in the derivative form of the monomer.

[0019] As used herein, “molecular weight” means weight average molecular weight (“Mw”). Molecular Weight Distribution (“MWD”) means Mw divided by number average molecular weight (“Mn”). (For more information, see U.S. Patent No. 4,540,753 to Cozewith et al. and references cited therein, and in Verstrate et ak, 21 Macromolecules 3360 (1998)). The“Mz” value is the high average molecular weight value, calculated as discussed by A. R. Cooper in Concise Encyclopedia of Polymer Science and Engineering 638-39 (J. I. Kroschwitz, ed. John Wiley & Sons 1990). As used herein, Mn, Mw, and Mz are measured by Size Exclusion Chromatography using a Waters 150 Gel Permeation Chromatograph equipped with a differential refractive index detector and calibrated using polystyrene standards. Samples are mn in tetrahydrofuran (THF) (45 °C). Molecular weights are reported as polystyrene-equivalent molecular weights and are generally measured in g/mol.

[0020] As used herein, weight percent (“wt%”), unless noted otherwise, means a percent by weight of a particular component based on the total weight of the mixture containing the component. For example, if a mixture contains three pounds of sand and one pound of sugar, then the sand comprises 75 wt% (3 lbs. sand/4 lbs. total mixture) of the mixture and the sugar 25 wt%. [0021] For purposes of the invention, unless otherwise specified heat of fusion and melting point (TM) values are determined by differential scanning calorimetry (DSC) in accordance with the following procedure. From about 6 mg to about 10 mg of a sheet of the polymer pressed at approximately 200°C to 230°C is removed with a punch die. This is annealed at room temperature for at least 2 weeks. At the end of this period, the sample is placed in a Differential Scanning calorimeter (TA Instruments Model 2920 DSC) and cooled to about - 50°C to about -70°C. The sample is heated at 10°C/min to attain a final temperature of about 200°C to about 220°C. The thermal output during this heating is recorded. The melting peak of the sample is typically peaked at 30°C to 175°C and occurs between the temperatures of 0°C and 200°C. The area under the thermal output curve, measured in Joules, is a measure of the heat of fusion. The melting point is recorded as the temperature of the greatest heat absorption within the range of melting of the sample.

Multilayer Films and Properties Thereof

[0022] This disclosure relates generally to multilayer films comprising a doped metallization layer with a metal layer thereon, wherein the doped metallization layer comprises polypropylene copolymer doped with a hydrocarbon resin. Such films may be used for food packaging applications.

[0023] FIG. 1 is a first example of a metallized cast multilayer polypropylene film 100 of the present invention. The film 100 includes a doped metallization layer 102 and a metal layer 104 deposited on a first surface 106 of the doped metallization layer 102. In the current example, a second surface 108 of the doped metallization layer 102 that opposes the first surface 106 of the doped metallization layer 102 does not have another layer thereon. However, in other embodiments, a layer may be present at the second surface 108 of the doped metallization layer 102. Optionally, that additional layer may be one of many additional layers in a multilayer film, for example, forming a multilayer film with four or more layers.

[0024] FIG. 2 is a second example of a metallized cast multilayer polypropylene film 200 of the present invention. The film 200 includes a core layer 210 between a sealant layer 212 and a doped metallization layer 202. The film 200 further includes a metal layer 204 deposited on a first surface 206 of the doped metallization layer 202 that opposes a second surface 208 of the doped metallization layer 202, where the second surface 208 is in contact with the core layer 210.

[0025] Referring now to FIGS. 1 and 2, the doped metallization layer 102, 202 can comprise or be formed of about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin. The metal layer 104, 204 can comprise or be formed of a metal including, but not limited to, aluminum, silver, chromium, and mixtures thereof. The core layer 210 can comprise or be formed of polypropylene (a polypropylene homopolymer and/or a polypropylene copolymer). The sealant layer 212 can comprise or be formed of a propylene-based elastomer.

[0026] The metal layer 106, 206 can be deposited on the doped metallization layer 102, 202 by conventional method including those described in International Publication No. WO/2002/081206, U.S. Patent Nos. 4,865,908, 5,057,177, 6,077,602, and 6,013,353, each of which is incorporated by reference. The metal layer 106, 206 can be about 10 nm to about 100 nm thick, preferably about 25 nm to about 60 nm.

[0027] The relative thickness of the core layer 210 to the sealant layer 212 can be from about 1:1 to about 5:1, preferably about 3:1. The relative thickness of the core layer 210 to the doped metallization layer 202 can be from about 1:1 to about 5:1, preferably about 3:1. The relative thickness of the sealant layer 212 to the doped metallization layer 202 can be from about 1:2 to about 2:1, preferably about 1:1. Examples of relative thicknesses of the sealant layer 212 to the core layer 210 to the doped metallization layer 202 include, but are not limited to, 2:5: 1, 1:5:2, 1:3:1, 1.5:3:1.5, 1:4:2, 2:4:1, 1:3:2, and 2:3:1.

[0028] An overall thickness of the film can be about 15 microns to about 50 microns, preferably about 20 microns to about 30 microns.

[0029] Wetting tension solutions (dyne solutions) are an easy and common tool to evaluate the surface energy of film surfaces. It is a current practice in the industry to also use these dyne solutions on metallized surfaces, to give an indication of the ability of the metal surface to offer good wetting to coatings applied thereon. The testing of the wetting tension on metallized surfaces followed an ExxonMobil method based on ASTM D-2578. A series of mixtures of formamide and ethylene glycolmonoethyl ether were used, with surface tensions ranging from 30 dyne/cm to 58 dyne/cm. The metallized film samples were cut out of rolls stored at 23±2°C and 50+10% relative humidity and tested immediately. Care was taken not to touch the film surface at the place of testing. The tips of cotton swabs were wet with just enough of a wetting tension solution to coat one square inch of a film sample. As little pressure as possible was applied with the cotton swab on the metallized surface tested and the solution was spread evenly over one square inch. The dyne/cm level of the solution showing the wetting time coming nearest to wetting the surface for exactly 2 seconds was assigned to the sample. A minimum of three sample points was tested at the positions 1/4, 1/2, and 3/4 across the film transverse direction. [0030] The metallized films of the present invention can have a surface tension measured at the surface of the metal layer of greater than about 36 dyne/cm, preferably greater than about 38 dyne/cm. The films of the present invention can have a surface tension measured at the surface of the metal layer of greater than about 36 dyne/cm, preferably greater than about 38 dyne/cm, at least about 20 days after metallization, preferably at least about 40 days after metallization, and more preferably at least about 60 days after metallization. These surface tension values (especially greater than about 38 dyne/cm) provide for a longer shelf-life of the films of the present invention as compared to comparable films without hydrocarbon resin in the doped metallization layer.

[0031] The surface tension (ST) can also be compared to an improvement over a reference film. The percent surface tension increase is calculated as the ST of the inventive film (ST_mv) minus the ST of the identical multilayer film without hydrocarbon resin in the doped metallization layer (ST_ref) where the subtraction result is then divided by the ST_ref and multiplied by 100 or (ST_mv - ST_ref)/ST_ref*100. Positive values are reported as an increase in surface tension while negative values are reported as a decrease or reduction in surface tension. The ST_mv can be up to a 20% surface tension increase (e.g., 3% to 20%) as compared to the ST_ref, or 5% to 20% surface tension increase as compared to the ST_ref, or a 5% to 15% surface tension increase as compared to the ST_ref. Further, the films of the present invention can maintain a surface tension increase over time as compared to the reference film. When films are compared over time, the aging of the inventive and reference films is the same. For example, after aging for 40 days at 23±2°C and 50%±10% humidity, the STi_nv can be up to a 20% surface tension increase (e.g., 3% to 20%) as compared to the ST_ref, or 5% to 20% surface tension increase as compared to the ST_ref, or a 5% to 15% surface tension increase as compared to the ST_ref. For example, after aging for 80 days at 23±2°C and 50%±10% humidity, the STi_nv can be up to a 20% surface tension increase (e.g., 3% to 20%) as compared to the ST_ref, or 5% to 20% surface tension increase as compared to the ST_ref, or a 5% to 15% surface tension increase as compared to the ST_ref.

[0032] Without being limited by any theory, the hydrocarbon resin in the metallization layer may limit the migration of narrow molecular weight species from the film to the surface of the metal, which, consequently, may lead to a maintaining the higher wettability over time.

[0033] Oxygen transmission rate is measured at standard pressure, 23°C, and 0% relative humidity per ASTM D3985-17. After metallization, the films of the present invention can have an oxygen transmission rate (OTR) of about 150 cm³/m²/d or less (e.g., about 5 cm³/m²/d to about 150 cm³/m²/d), preferably about 10 cm³/m²/d to about 100 cm³/m²/d, and more preferably about 5 cm³/m²/d to about 20 cm³/m²/d. For food packaging applications, a metallized cPP with an oxygen transmission rate of about 30 cm³/m²/d or less is good and a generally accepted standard. However, an oxygen transmission rate of less than about 15 cm³/m²/d or less is very good and difficult to attain.

[0034] The OTR of an inventive film can also be compared to the OTR a reference film. The percent permeability reduction is calculated as the OTR of the identical multilayer film without hydrocarbon resin in the doped metallization layer (OTR_ref) minus the OTR of the inventive film (OTRi_nv) where the subtraction result is then divided by the OTR_ref and multiplied by 100 or (OTR_ref - OTRi_nv)/OTR_ref*100. Negative values for OTR_ref - OTRi_nv are reported as an increase in oxygen transmission rate while positive values for OTR_ref - OTRi_nv are reported as a decrease or reduction in oxygen transmission rate. The OTRi_nv can be at least a 25% permeability reduction (e.g., 25% to 50%) as compared to the OTR_ref, or 25% to 45% permeability reduction as compared to the OTR_ref, or a 30% to 40% permeability reduction as compared to the OTR_ref.

[0035] After metallization, the films of the present invention can have a water vapor transmission rate of about 0.5 g/m²/d or less (e.g., about 0.1 g/m²/d to about 0.5 g/m²/d), preferably about 0.1 g/m²/d to about 0.3 g/m²/d, and more preferably about 0.1 g/m²/d to about 0.2 g/m²»d. Water transmission rate is measured at standard pressure, 38°C, and 90% relative humidity per ASTM F1249-13. For food packaging applications a water vapor transmission rate of less than about 0.5 g/m²/d or less is good and a generally accepted standard.

Polypropylene Polymers

[0036] The doped metallization layer 102, 202 of FIGS. 1 and 2 or a doped metallization layer of any other suitable multilayer film can comprise or be formed of about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin. The core layer 210 of FIG. 2 or a core layer of any other suitable multilayer film can comprise or be formed of polypropylene (a polypropylene homopolymer and/or a polypropylene copolymer).

[0037] The following description and/or limitation to“propylene polymers” is applicable to any propylene polymer that is useful in any of these multiple layers, unless expressly indicated otherwise. Also, as described herein, the term “propylene polymer” and “polypropylene” is interchangeable.

[0038] Suitable propylene polymers useful in the present multilayer films have a melting point above about 115°C, or above about 120°C, or above about 130°C. Suitable propylene polymers may be propylene homopolymer (or “homopolypropylene”) or copolymers of propylene and at least one comonomer selected from ethylene and C4 - C20 alpha-olefins (or “polypropylene copolymer”).

[0039] The propylene polymers useful in the present invention may have some level of isotacticity. Thus, in any embodiment, the propylene polymer may comprise isotactic polypropylene. As used herein,“isotactic” is defined as having at least 60% isotactic pentads according to analysis by ¹³C-NMR. Alternatively, the propylene polymer may include atactic sequences or syndiotactic sequences. For example, a suitable homopolypropylene can have at least 85% syndiotacticity, and alternatively at least 90% syndiotacticity. As used herein, “syndiotactic” is defined as having at least 60% syndiotactic pentads according to analysis by ¹³C-NMR. Atactic polypropylene is defined to be less than 10% isotactic or syndiotactic pentads. Preferred atactic polypropylenes typically have an Mw of 20,000 up to 1,000,000.

[0040] Often, the propylene polymer is or comprises homopolypropylene. Preferably, the homopolypropylene has a melt flow rate (MFR) (ASTM D1238-13, 230°C, 2.16 kg) in the range from 0.1 dg/min to 500 dg/min, or from 0.5 dg/min to 200 dg/min, or from 0.5 dg/min to 100 dg/min, or from 1 dg/min to 50 dg/min, or from and from 1.5 dg/min to 20 dg/min, or from 2 dg/min to 10 dg/min. Preferably, the homopolypropylene has a 1% secant flexural modulus ranging from 100 MPa to 2300 MPa, preferably 300 MPa to 2100 MPa, and more preferably from 500 MPa to 2000 MPa. Preferably, the homopolypropylene has a molecular weight distribution (Mw/Mn) of up to 40, preferably ranging from 1.5 to 10, or from 1.8 to 7, or from 1.9 to 5, or from 2.0 to 4.

[0041] Preferably, homopolypropylene has at least 85% isotacticity, more preferably at least 90% isotacticity. Suitable isotactic polypropylene has a melt temperature (T_m) ranging from a low of about 130°C, or about 140°C, 150°C, or 160°C to a high of about 160°C, 170°C, or 175°C, such as from 150°C to 170°C. The isotactic polypropylene preferably has a glass transition temperature (T_g) ranging from a low of about -5°C, -3°C, or 0°C to a high of about 2°C, 5°C, or 10°C, such as from -3°C to 5°C. The crystallization temperature (T_c) of the isotactic polypropylene preferably ranges from a low of about 95°C, 100°C, or 105°C to a high of about 110°C, 120°C or 130°C, such as 100°C to 120°C, as measured by differential scanning calorimetry (DSC) at 10°C/min. Furthermore, the isotactic polypropylene preferably has a crystallinity of at least 25 percent as measured by DSC at 10 °C/min. Generally, the isotactic polypropylene has a melt flow rate of less than about 10 dg/min, often less than about 5 dg/min, and often less than about 3 dg/min. Often, the isotactic polypropylene has a melt flow rate ranging from about 2 dg/min to about 5 dg/min. A preferred isotactic polypropylene has a heat of fusion of greater than 75 J/g, or greater than 80 J/g, or greater than 90 J/g to a high of about 150 J/g, such as from about 80 J/g to about 120 J/g. In any embodiment, the isotactic polypropylene may have a density of from about 0.85 g/cc to about 0.93 g/cc. Preferably, the isotactic polypropylene has a density of from about 0.88 g/cc to about 0.92 g/cc, more preferably from about 0.90 g/cc to about 0.91 g/cc.

[0042] An illustrative isotactic polypropylene has a weight average molecular weight (Mw) from about 200,000 to about 600,000 g/mole, and a number average molecular weight (Mn) from about 80,000 to about 200,000 g/mole. A more preferable isotactic polypropylene has an Mw from about 300,000 to about 500,000 g/mole, and an Mn from about 90,000 to about 150,000 g/mole. In any embodiment, the isotactic polypropylene may have an MWD within a range having a low of 1.5, 1.8, or 2.0 and a high of 4.5, 5, 10, 20, or 40, such as from 1.5 to 4.0.

[0043] Alternatively, the propylene polymer is a polypropylene copolymer having a propylene content in an amount greater than about 80 wt%, ideally greater than about 90 wt%, such as from about 93 wt% to about 99.5 wt%, and a comonomer content in an amount ranging from a low of about 0.1, 0.25, 0.5, 1, 2, 3, 4, or 6 wt% to a high of about 1, 3, 5, 7, 8, 9, 15, or 20 wt%, such as from about 0.5 wt% to about 7 wt% based on the weight of the copolymer.

[0044] Suitable comonomer(s) can be selected from the group consisting of ethylene and C4 to C20 linear, branched or cyclic monomers, preferably C4 to C12 linear or branched alpha- olefins. Suitable comonomers cumulatively may be present at up to 20 wt%, preferably from 0 wt% to 20 wt%, more preferably from 0.1 wt% to 10 wt%, more preferably from 0.5 wt% to 8 wt% by weight of the propylene -based copolymer.

[0045] Preferred linear alpha-olefins useful as comonomers include C₃ to Cx alpha-olefins, more preferably 1 -butene, 1 -hexene, and 1-octene, even more preferably 1 -butene. Preferred branched alpha-olefins include 4-methyl- 1-pentene, 3 -methyl- 1-pentene, and 3,5,5-trimethyl- 1-hexene, and 5-ethyl- 1-nonene. An example propylene copolymer includes monomer units derived from propylene, ethylene, and butene.

[0046] Optionally, aromatic-group-containing comonomers, non-aromatic cyclic group containing comonomers, or diolefin comonomers can be comprised in the propylene polymers. These comonomers can contain up to 30 carbon atoms, e.g., from 4 to 20 carbon atoms. Examples of preferred dienes include butadiene, pentadiene, hexadiene, heptadiene, octadiene, nonadiene, decadiene, undecadiene, dodecadiene, tridecadiene, tetradecadiene, pentadecadiene, hexadecadiene, heptadecadiene, octadecadiene, nonadecadiene, icosadiene, heneicosadiene, docosadiene, tricosadiene, tetracosadiene, pentacosadiene, hexacosadiene, heptacosadiene, octacosadiene, nonacosadiene, triacontadiene, particularly preferred dienes include 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,10-undecadiene, 1,11- dodecadiene, 1,12-tridecadiene, 1,13-tetradecadiene, and low molecular weight polybutadienes (Mw less than 1000 g/mol). Preferred cyclic dienes include cyclopentadiene, vinylnorbornene, norbomadiene, ethylidene norbomene, divinylbenzene, dicyclopentadiene or higher ring containing diolefins with or without substituents at various ring positions. Often, one or more dienes are present in the propylene-based copolymer at up to 10 wt%, preferably from 0.1 to 5.0 wt%, more preferably from 0.1 to 3 wt% based upon the total weight of the copolymer.

[0047] Preferably, the polypropylene copolymer can be selected from random copolymers (RCP), block copolymers, impact copolymers (ICP) (e.g., an intimate blend of polypropylene homopolymer and an ethylene-propylene elastomer, also known in the art as heterophasic copolymers), and terpolymers. Preferred RCPs include single phase polypropylene copolymers having up to about 9 wt%, preferably about 2 wt% to about 8 wt%, of an alpha olefin comonomer, preferably ethylene.

[0048] Preferably, useful propylene-based copolymers have a weight average molecular weight greater than 8,000 g/mol, alternatively greater than 10,000 g/mol, alternatively greater than 12,000 g/mol, and alternatively than 20,000 g/mol. Preferably, useful propylene-based copolymers have a weight average molecular weight less than 1,000,000 g/mol, and alternatively less than 800,000. A desirable propylene-based copolymer may comprise any upper molecular weight limit with any lower molecular weight limit described herein.

[0049] Useful propylene-based copolymers have an Mw/Mn ranging from 1.5 to 10, preferably from 1.6 to 7, more preferably from 1.7 to 5, and most preferably from 1.8 to 4. Often, suitable propylene-based copolymers have a 1 % secant flexural modulus ranging from 100 MPa to 2300 MPa, preferably from 200 MPa to 2100 MPa, and more preferably from 300 MPa to 2000 MPa. Often, suitable propylene-based polymers have an MFR ranging from 0.1 dg/min to 2500 dg/min, preferably from 0.3 dg/min to 500 dg/min.

[0050] Often, the propylene polymers are or comprise a“tailored crystallinity resin” (“TCR”). Suitable TCRs include any modified polypropylene comprising an in situ reactor blend of a higher molecular weight propylene/ethylene random copolymer and a lower molecular weight substantially isotactic homopolypropylene, such as those described in U.S. Patent No. 4,950,720, which is incorporated by reference.

[0051] Often, the propylene polymers useful in the invention can be nucleated with one or more nucleating agents prior to the use in the present multilayer film, e.g., prior to incorporation in the multilayer film and/or prior to the addition of the hydrocarbon resin. Alternatively, the polypropylene can be non- nucleated, i.e., nucleating agents are absent. In any embodiment, suitable nucleating agents may be selected from the group consisting of sodium benzoate, talc, glycerol alkoxide salts, cyclic carboxylic acid salts, bicyclic carboxylic acid salts, glycerolates, and hexahydrophtalic acid salts. Nucleating agents include HYPERFORM™ additives, such as HPN-68, HPN-68L, HPN-20, HPN-20E, MILLAD™ additives (e.g., MILLAD™ 3988) (Milliken Chemicals, Spartanburg, SC) and organophosphates such as NA-11 and NA-21 (Amfine Chemicals, Allendale, NJ). In any embodiment, suitable nucleating agents may comprise at least one bicyclic carboxylic acid salt. In any embodiment, suitable nucleating agents may comprise bicycloheptane dicarboxylic acid, disodium salt such as bicyclo [2.2.1] heptane dicarboxylate. In any embodiment, suitable nucleating agents may be a blend of components comprising bicyclo [2.2.1] heptane dicarboxylate, disodium salt, 13- docosenamide, and amorphous silicon dioxide. In any embodiment, suitable nucleating agents may be cyclohexanedicarboxylic acid, calcium salt or a blend of cyclohexanedicarboxylic acid, calcium salt, and zinc stearate. In any embodiment, suitable nucleating agents include clarifying agents.

[0052] The method of making the propylene polymers is not critical. Illustrative polymerization methods include, but are not limited to, slurry, bulk phase, solution phase, and any combination thereof. Any catalyst system appropriate for the polymerization of polyolefins may be used, such as Ziegler-Natta-type catalysts, metallocene-type catalysts, or combinations thereof. Such catalysts are well known in the art, and are described in, for example, ZIEGLER CATALYSTS (Gerhard Fink, Rolf Miilhaupt and Hans H. Brintzinger, eds., Springer-Verlag 1995); Resconi et ak, Selectivity in Propene Polymerization with Metallocene Catalysts, 100 CHEM. REV. 1253-1345 (2000); and I, II METALLOCENE-BASED POLYOLEFINS (Wiley & Sons 2000).

[0053] Preferably, the propylene polymers are made by the catalysts, activators and processes described in U.S. Patent Nos. 6,342,566, 6,384,142, International Publication Nos. WO 03/040201, WO 97/19991 and U.S. Patent No. 5,741,563. Impact copolymers may be prepared by the process described in U.S. Patent Nos. 6,342,566 and 6,384,142.

[0054] Examples of particularly suitable propylene polymers include homopolypropylenes commercially available from ExxonMobil Chemical Company under the names of PP4712, and PP4612, from Total Petrochemical under the names of 3371, 3270, 3576X; random copolymers of polypropylene commercially available from ExxonMobil Chemical Company under the names of PP9513, from INEOS Olefins & Polymers under the name of ELTEX™ P KS407, from Basell under the name of ADSYL™ 3C30FHP, and from Borealis under the name of BORPURE™ RD208CF; and terpolymers of propylene such as commercially available from INEOS Olefins & Polymer under the names of ELTEX™ P KS357.

[0055] In a doped metallization layer 102, 202 of FIGS. 1 and 2 or a doped metallization layer of any other suitable multilayer film, the polypropylene copolymer can be present at about 75 wt% to about 99 wt % relative to the composition of the doped metallization layer, preferably about 80 wt % to about 99 wt% relative to the composition of the doped metallization layer, preferably about 85 wt% to about 99 wt% relative to the composition of the doped metallization layer, preferably about 90 wt% to about 99 wt% relative to the composition of the doped metallization layer, preferably about 95 wt% to about 99 wt% relative to the composition of the doped metallization layer, and most preferably about 80 wt% to about 90 wt% relative to the composition of the doped metallization layer.

[0056] In a core layer 210 of FIG. 2 or a core layer any other suitable multilayer film, the polypropylene (a polypropylene homopolymer and/or a polypropylene copolymer) can be present at about 90 wt% to about 100 wt% relative to the composition of the core layer, preferably about 95 wt% to about 100 wt% relative to the composition of the core layer, and preferably about 90 wt% to about 95 wt% relative to the composition of the core layer.

Hydrocarbon Resin

[0057] Suitable hydrocarbon resins for use in compositions and methods of the present invention may include, but are not limited to, aliphatic hydrocarbon resins, hydrogenated aliphatic hydrocarbon resins, aliphatic/aromatic hydrocarbon resins, hydrogenated aliphatic aromatic hydrocarbon resins, cycloaliphatic hydrocarbon resins, hydrogenated cycloaliphatic resins, cycloaliphatic/aromatic hydrocarbon resins, hydrogenated cycloaliphatic/aromatic hydrocarbon resins, hydrogenated aromatic hydrocarbon resins, polyterpene resins, terpene- phenol resins, rosins and mixtures of two or more thereof. As used herein, rosin includes rosin esters and rosin acids, which may also be hydrogenated.

[0058] Examples of commercially available hydrocarbon resins may include, but are not limited to, OPPERA™ PR 100, 101, 102, 103, 104, 105, 106, 111, 112, 115, 120, ECR-373, and ESCOREZ® 1000, 2000, and 5000 series hydrocarbon resins available from ExxonMobil Chemical Company; ARKON™ M90, M100, Ml 15 and M135 and SUPER ESTER™ rosin esters available from Arakawa Chemical Company of Japan; SYLVARES™ phenol modified styrene-a methyl styrene resins available from Kraton Corporation; styrenated terpene resins ZONATAC™ available from Kraton Corporation; terpene phenolic resins available from Kraton Corporation; NORSOLENE™ aliphatic aromatic resins available from Cray Valley of France; DERTOPHENE™ terpene phenolic resins available from DRT Chemical Company of Landes, France; EASTOTAC™ resins, PICCOTAC™ C5/C9 resins, REGALITE™ and REGALREZ™ aromatic and REGALITE™ cycloaliphatic/aromatic resins available from Eastman Chemical Company; WINGTACK™ ET and EXTRA available from Goodyear Chemical Company; FORAL™, PENTALYN™, AND PERMALYN™ rosins and rosin esters available from Eastman Chemical Company; QUINTONE™ acid modified C5 resins, C5/C9 resins, and acid modified C5/C9 resins available from Nippon Zeon of Japan; LX™ mixed aromatic/cycloaliphatic resins available from Neville Chemical Company; and CLEARON™ hydrogenated terpene aromatic resins available from Yasuhara.

[0059] The hydrocarbon resin used in compositions and methods of the present invention are not modified or reacted with an unsaturated acid or anhydride or derivative thereof.

[0060] The hydrocarbon resins preferably have a molecular weight (Mw) of about 10,000 g/mol or less (e.g., about 1000 g/mol to about 10,000 g/mol), more preferably about 5000 g/mol or less, more preferably about 2500 g/mol or less, and more preferably about 2000 g/mol or less.

[0061] In a doped metallization layer 102, 202 of FIGS. 1 and 2 or a doped metallization layer of any other suitable multilayer film, the hydrocarbon resin can be present at about 1 wt% to about 25 wt% relative to the composition of the doped metallization layer, preferably about 1 wt% to about 20 wt% relative to the composition of the doped metallization layer, preferably about 1 wt% to about 15 wt% relative to the composition of the doped metallization layer, preferably about 1 wt% to about 10 wt% relative to the composition of the doped metallization layer 106, preferably about 1 wt% to about 5 wt% relative to the composition of the doped metallization layer, preferably about 5 wt% to about 20 wt% relative to the composition of the doped metallization layer, and preferably about 10 wt% to about 20 wt% relative to the composition of the doped metallization layer.

Propylene-Based Elastomer

[0062] The sealant layer 212 of FIG. 2 or a sealant layer of any other suitable multilayer film can comprise or be formed of a propylene-based elastomer.

[0063] As used herein, the term“propylene-based elastomer” means a polymer having a melt flow rate in the range of 0.5 dg/min to 50 dg/min, a heat of fusion of less than 75 J/g and comprising 65 wt% to 99 wt% of polymer units derived from propylene and 1 wt% to 35 wt% of polymer units derived from ethylene, a C4 to C20 alpha-olefin comonomer, a diene, or mixtures thereof, based upon total weight of the propylene-based elastomer.

[0064] Particularly suitable propylene-based elastomers include copolymers of propylene and at least one comonomer selected from ethylene and C4-C10 alpha-olefins. The propylene- based elastomer may have limited crystallinity due to adjacent isotactic propylene units and a melting point as described herein. The crystallinity and the melting point of the propylene- based elastomer can be reduced compared to highly isotactic polypropylene by the introduction of errors in the insertion of propylene. The propylene-based elastomer is generally devoid of any substantial intermolecular heterogeneity in tacticity and comonomer composition, and also generally devoid of any substantial heterogeneity in intramolecular composition distribution.

[0065] Preferably, the propylene content of the propylene-based elastomer may range from an upper limit of about 99 wt%, about 97 wt%, about 95 wt%, about 94 wt%, about 92 wt%, about 90 wt%, or about 85 wt%, to a lower limit of about 75 wt%, about 80 wt%, about 82 wt%, about 85 wt%, or about 90 wt%, for example, from about 75 wt% to about 99%, from about 80 wt% to about 99 wt%, or from about 90 wt% to about 97 wt%, based on the weight of the propylene-based elastomer. Preferably, the comonomer content of the propylene -based elastomer may range from about 1 wt% to about 25 wt%, or about 3 wt% to about 25 wt%, or about 3 wt% to about 20 wt%, or about 3 wt% to about 18 wt%, or from about 3 wt% to about 11 wt%, of the propylene-based elastomer. The comonomer content may be adjusted so that the propylene-based elastomer has a heat of fusion of less than about 80 J/g, a melting point of about 115°C or less, and a crystallinity of about 2% to about 65% of the crystallinity of isotactic polypropylene, and a fractional melt mass-flow rate of about 0.5 g/min. to about 20 g/min.

[0066] Preferably, the comonomer is ethylene and/or butene. Where the propylene -based elastomer comprises ethylene-derived units, the propylene-based elastomer may comprise an ethylene content from about 3 wt% to about 25 wt%, or about 4 wt% to about 20 wt%, or about 9 wt% to about 18 wt%. Often, the propylene-based elastomer consists essentially of units derived from propylene and ethylene, i.e., the propylene-based elastomer does not contain any other comonomer in an amount other than that typically present as impurities in the ethylene and/or propylene feedstreams used during polymerization, or in an amount that would materially affect the heat of fusion, melting point, crystallinity, or fractional melt mass-flow rate of the propylene-based elastomer, or in an amount such that any other comonomer is intentionally added to the polymerization process.

[0067] Often, the propylene-based elastomer may comprise more than one comonomer. Preferred propylene-based elastomers having more than one comonomer include propylene- ethylene-octene, propylene-ethylene-hexene, and propylene-ethylene-butene polymers, with the most preferred being propylene-ethylene-butene polymers. Where more than one comonomer is present, a single comonomer may be present at a concentration of less than about 5 wt% of the propylene-based elastomer, but the total comonomer content of the propylene- based elastomer is generally about 5 wt % or greater.

[0068] The propylene-based elastomer may have an mm triad tacticity index as measured by ¹³C NMR, of at least about 75%, at least about 80%, at least about 82%, at least about 85%, or at least about 90%. Preferably, the propylene-based elastomer has an mm triad tacticity of about 75% to about 99%, or about 80% to about 99%. In some embodiments, the propylene- based elastomer may have an mm triad tacticity of about 75% to 97%. The“mm triad tacticity index” of a polymer is a measure of the relative isotacticity of a sequence of three adjacent propylene units connected in a head-to-tail configuration. More specifically, in the present invention, the mm triad tacticity index (also referred to as the “mm Fraction”) of a polypropylene homopolymer or copolymer is expressed as the ratio of the number of units of meso tacticity to all of the propylene triads in the copolymer:

PPP(mm)

mm Fraction

PPP(mm) + PPP(mr) + PPP(rr) where PPP(mm), PPP(mr) and PPP(rr) denote peak areas derived from the methyl groups of the second units in the possible triad configurations for three head-to-tail propylene units, shown below in Fischer projection diagrams:

[0069] The calculation of the mm Fraction of a propylene polymer is described in U.S. Patent 5,504,172 (homopolymer: column 25, line 49 to column 27, line 26; copolymer: column 28, line 38 to column 29, line 67). For further information on how the mm triad tacticity can be determined from a ¹³C-NMR spectrum, see 1) J. A. Ewen, CATALYTIC POLYMERIZATION OF OLEFINS: PROCEEDINGS OF THE INTERNATIONAL SYMPOSIUM ON FUTURE ASPECTS OF OLEFIN POLYMERIZATION, T. Keii and K. Soga, Eds. (Elsevier, 1986), pp. 271-292; and 2) U.S. Patent Application US2004/054086 (paragraphs [0043] to [0054]).

[0070] The propylene-based elastomer generally has a heat of fusion of about 65 J/g or less, or about 60 J/g or less, or about 50 J/g or less, or about 40 J/g or less. The propylene -based elastomer may have a lower limit H_f of about 0.5 J/g, or about 1 J/g, or about 5 J/g. For example, the H_f value may range from a lower limit of about 1.0 J/g, 1.5 J/g, 3.0 J/g, 4.0 J/g, 6.0 J/g, or 7.0 J/g, to an upper limit of about 35 J/g, 40 J/g, 50 J/g, 60 J/g, or 65 J/g.

[0071] The propylene-based elastomer may have a percent crystallinity, as determined according to ASTM D3418-03 with a 10°C/min heating/cooling rate, of about 2% to about 65%, or about 0.5% to about 40%, or about 1% to about 30%, or about 5% to about 35%, of the crystallinity of isotactic polypropylene. The thermal energy for the highest order of propylene (i.e., 100% crystallinity) is estimated at 189 J/g. In some embodiments, the copolymer has crystallinity less than 40%, or in the range of about 0.25% to about 25%, or in the range of about 0.5% to about 22%, of the crystallinity of isotactic polypropylene.

[0072] In any embodiment, the propylene-based elastomer may have a tacticity index [m/r] from a lower limit of about 4, or about 6, to an upper limit of about 8, or about 10, or about 12. Often, the propylene-based elastomer has an isotacticity index greater than 0%, or within the range having an upper limit of about 50%, or about 25%, and a lower limit of about 3%, or about 10%. The tacticity index is calculated as defined in H.N. Cheng, Macromolecules, 17, 1950 (1984). When [m/r] is 0 to less than 1.0, the polymer is generally described as syndiotactic, when [m r] is 1.0 the polymer is atactic, and when [m/r] is greater than 1.0 the polymer is generally described as isotactic.

[0073] Often, the propylene-based elastomer may further comprise diene-derived units (as used herein,“diene”). The optional diene may be any hydrocarbon structure having at least two unsaturated bonds wherein at least one of the unsaturated bonds is readily incorporated into a polymer. For example, the optional diene may be selected from straight chain acyclic olefins, such as 1,4-hexadiene and 1,6-octadiene; branched chain acyclic olefins, such as 5-methyl-l,4- hexadiene, 3,7-dimethyl-l,6-octadiene, and 3,7-dimethyl-l,7-octadiene; single ring alicyclic olefins, such as 1,4-cyclohexadiene, 1,5-cyclooctadiene, and 1,7-cyclododecadiene; multi-ring alicyclic fused and bridged ring olefins, such as tetrahydroindene, norbornadiene, methyl- tetrahydroindene, dicyclopentadiene, bicyclo-(2.2.1)-hepta-2, 5-diene, norbornadiene, alkenyl norbomenes, alkylidene norbornenes, e.g., ethylidiene norbomene (“ENB”), cycloalkenyl norbomenes, and cycloalkylene norbomenes (such as 5-methylene-2-norbomene, 5- ethylidene-2-norbomene, 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene, 5-(4- cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbomene); and cycloalkenyl-substituted alkenes, such as vinyl cyclohexene, allyl cyclohexene, vinyl cyclooctene, 4- vinyl cyclohexene, allyl cyclodecene, vinyl cyclododecene, and tetracyclo (A- ll,12)-5,8-dodecene. The amount of diene-derived units present in the propylene-based elastomer may range from an upper limit of about 15%, about 10%, about 7%, about 5%, about 4.5%, about 3%, about 2.5%, or about 1.5%, to a lower limit of about 0%, about 0.1%, about 0.2%, about 0.3%, about 0.5%, about 1%, about 3%, or about 5%, based on the total weight of the propylene-based elastomer.

[0074] The propylene-based elastomer may have a single peak melting transition as determined by DSC. In some embodiments, the copolymer has a primary peak transition of about 90°C or less, with a broad end-of-melt transition of about 110°C or greater. The peak “melting point” (“T_m”) is defined as the temperature of the greatest heat absorption within the range of melting of the sample. However, the copolymer may show secondary melting peaks adjacent to the principal peak, and/or at the end-of-melt transition. For the purposes of this disclosure, such secondary melting peaks are considered together as a single melting point, with the highest of these peaks being considered the T_m of the propylene -based elastomer. The propylene-based elastomer may have a T_m of about 115°C or less, about 110°C or less , about 105°C or less, about 100°C or less, about 90°C or less, about 80°C or less, or about 70°C or less. In some embodiments, the propylene -based elastomer has a T_m of about 25°C to about 115°C, or about 40°C to about 110°C, or about 60°C to about 105 °C. T_m of the propylene-based elastomer can be determined by ASTM D3418-03 with a 10°C/min heating/cooling rate.

[0075] The propylene -based elastomer may have a density of about 0.850 g/cm³ to about 0.900 g/cm³, or about 0.860 g/cm³ to about 0.880 g/cm³, at room temperature as measured based on ASTM D1505-18.

[0076] The propylene-based elastomer may have a fractional melt mass-flow rate (MFR), as measured based on ASTM D1238-13, 2.16 kg at 230°C, of at least about 0.5 g/10 min. In some embodiments, the propylene-based elastomer may have a fractional MFR of about 0.5 g/10 min. to about 50 g/10 min, or about 2 g/10 min. to about 18 g/10 min. The propylene- based elastomer may have an Elongation at Break of less than about 2000%, less than about 1800%, less than about 1500%, or less than about 1000%, as measured based on ASTM D638- 14.

[0077] The propylene-based elastomer may have an Mw of about 5,000 g/mol to about 5,000,000 g/mol, or about 10,000 g/mol to about 1,000,000 g/mol, or about 50,000 g/mol to about 400,000 g/mol. The propylene -based elastomer may have an Mn of about 2,500 g/mol to about 250,000 g/mol, or about 10,000 g/mol to about 250,000 g/mol, or about 25,000 g/mol to about 250,000 g/mol. The propylene-based elastomer may have a Mz of about 10,000 g/mol to about 7,000,000 g/mol, or about 80,000 g/mol to about 700,000 g/mol, or about 100,000 g/mol to about 500,000 g/mol. The propylene-based elastomer may have a Mw/Mn of about 1.5 to about 20, or about 1.5 to about 15, or about 1.5 to about 5, or about 1.8 to about 3, or about 1.8 to about 2.5.

[0078] In a sealant layer 212 of FIG. 2 or a sealant layer of any other suitable multilayer film, the propylene-based elastomer can be present at about 90 wt% to about 100 wt% relative to the composition of the sealant layer, preferably about 95 wt% to about 100 wt% relative to the composition of the sealant layer, and preferably about 90 wt% to about 95 wt% relative to the composition of the sealant layer.

Additives

[0079] Optionally, additional additives may be present in each of the layers of the multilayer films described herein. Such additives include those known in the art for modifying the polymer composition to provide particular physical characteristics or effects. The use of appropriate additives is well within the skill of one in the art. Examples of such additives include, but are not limited to, slip additive, antiblocking additive (e.g., silica), colored pigments, UV stabilizers, antioxidants, light stabilizers, flame retardants, antistatic agents, biocides, viscosity-breaking agents, impact modifiers, plasticizers, fillers, reinforcing agents, lubricants, mold release agents, blowing agents, pearlizers, and the like. Such additives may comprise from about 0.01% to about 10% by weight based on the total weight of the composition of the layer. Alternatively, additives may be absent or substantially absent from the polymer composition of any layer. For instance, additives may comprise less than 1.0%, or less than 0.5%, or less than 0.1% by weight based on the total weight of the composition of the layer.

Methods

[0080] The multilayer films of the present invention may be manufactured by any conventional process, including simple bubble extrusion, biaxial orientation processes (e.g., tenter frames, trapped bubble, or double bubble processes), simple cast/sheet extrusion- lamination, co-extrusion, lamination, extrusion coating, and co-extrusion coating, blowing and casting, and the like. For example, the film can be coextruded and casted on a cast line. The resultant film can then be metallized with A1 vapor under high vacuum condition. Usually, such metallized cast films are subsequently laminated to another film though techniques such as adhesive lamination or extrusion lamination, so that the metallized layer is protected from scratches.

[0081] In one example method, melts of the polymer/polymer blends for each of the layers (e.g., a homopolymer of polypropylene optionally with additives for the core layer, a polypropylene copolymer and a hydrocarbon resin optionally with additives for the doped metallization layer, and a propylene -based elastomer optionally with additives for the sealant layer) can be coextruded through a die and cooled (e.g., by quenching) to form a multilayer film of the present invention.

[0082] The metallized multilayer film of the present invention can be used in food packaging after lamination to another material. The other materials can include, but is not limited to, BOPP, BOPET, paper, wood, cardboard, fabric, non-woven material, polyvinyl chloride, plastic, polyamide, metal, and any combination thereof. The resultant laminate can be used on a packaging machine, in order to package a product, most often food. Often, such manufacturing subjects the laminate, especially the metallization layer therein, to significant stresses, which can result in a decrease of barrier performance.

Example Embodiments

[0083] An example embodiment of the present invention is a multilayer metallized cast polypropylene films comprising: a doped metallization layer comprising about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin; and a metal layer on a first surface of the doped metallization layer. Further embodiments can include one or more of the following: Element 1: the film further comprising: a sealant layer; and a core layer between the doped metallization layer and the sealant layer, wherein the core layer is on a second surface of the doped metallization layer that opposes the first surface of the doped metallization layer; Element 2: Element 1 and wherein the core layer comprises polypropylene at about 90 wt% to about 100 wt%, and wherein the sealant layer comprises a propylene-based elastomer at about 90 wt% to about 100 wt%; Element 3: wherein the doped metallization layer comprises about 90 wt% to about 99 wt% of the polypropylene copolymer and about 1 wt% to about 10 wt% of the hydrocarbon resin; Element 4: wherein the multilayer film has an oxygen transmission rate that is at least 20% less than an oxygen transmission rate of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer; Element 5 : wherein the doped metallization layer comprises about 80 wt% to about 90 wt% of the polypropylene copolymer and about 10 wt% to about 20 wt% of the hydrocarbon resin, wherein the polypropylene copolymer is the random propylene copolymer; Element 6: wherein the metal layer of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metal layer of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer, wherein both films have aged under same conditions; Element 7: wherein the metal layer of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metal layer of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 40 days at 23±2 °C and 50%±10% humidity; Element 8: wherein the metal layer of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metal layer of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 80 days at 23±2°C and 50%±10% humidity. Examples of combinations include, but are not limited to, Element 1 and optionally Element 2 in combination with one or more of Elements 3-8, Element 3 in combination with Element 4; and Element 5 in combination with one or more of Elements 6- 8.

[0084] Another example embodiment is a method comprising: casting a doped metallization polymer melt to form a doped metallization layer, wherein the doped metallization polymer melt comprises about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin; and metallizing a first surface of the doped metallization layer to form a multilayer film. Further embodiments can include one or more of the following: Element 9: the method further comprising: casting a core polymer melt and a sealant polymer melt with the doped metallization polymer melt to form a film with a core polymer layer between the doped metallization layer and a sealant polymer layer, wherein after metallizing the core layer is on a second surface of the doped metallization layer that opposes the first surface of the doped metallization layer; Element 10: Element 9 and wherein the core polymer melt comprises polypropylene at about 90 wt% to about 100 wt%, and wherein the sealant polymer melt comprises a propylene-based elastomer at about 90 wt% to about 100 wt%; Element 11: wherein doped metallization melt comprises about 90 wt% to about 99 wt% of the polypropylene copolymer and about 1 wt% to about 10 wt% of the hydrocarbon resin; Element 12: wherein the multilayer film has an oxygen transmission rate that is at least 25% less than an oxygen transmission rate of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer; Element 13: wherein the doped metallization layer comprises about 80 wt% to about 90 wt% of the polypropylene copolymer and about 10 wt % to about 20 wt % of the hydrocarbon resin, wherein the polypropylene copolymer is the random propylene copolymer; Element 14: wherein the metallized surface of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metallized surface of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer, wherein both films have aged under same conditions; Element 15: wherein the metallized surface of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metallized surface of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 40 days at 23±2°C and 50%±10% humidity; and Element 16: wherein the metallized surface of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metallized surface of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 80 days at 23±2°C and 50%±10% humidity. Examples of combinations include, but are not limited to, Element 9 and optionally Element 10 in combination with one or more of Elements 11-16, Element 11 in combination with Element 12; and Element 13 in combination with one or more of Elements 14-16.

[0085] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0086] One or more illustrative embodiments incorporating the invention embodiments disclosed herein are presented herein. Not all features of a physical implementation are described or shown in this application for the sake of clarity. It is understood that in the development of a physical embodiment incorporating the embodiments of the present invention, numerous implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government- related and other constraints, which vary by implementation and from time to time. While a developer's efforts might be time-consuming, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill in the art and having benefit of this disclosure.

[0087] While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methods can also“consist essentially of’ or“consist of’ the various components and steps.

[0088] To facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.

EXAMPLES

[0089] Example I. Several films according to FIG. 2 were prepared according to Table 1, where I-R is the reference sample not doped with hydrocarbon resin. The I-R, I- 1, 1-2, 1-3, and 1-4 samples were firstly coextruded and casted on a 3-layer industrial scale Shicheng cast line (die width 4 m) using the materials in Table 1 to form transparent cast polypropylene (CPP) films. The first chill roll temperature was 26°C, and second chill roll temperature was 25°C. The line speed was 160 m/min. All films were corona-treated in line with film making. The film rolls were collected for each sample and kept in a 40°C warm room for 1 day for further stabilization. They were then slit to a proper size and put into a metallizer to deposit 99.99% aluminum (Al) on the surface of the doped metallization layer 202 with a line speed of 360 m/min and a chill roll temperature of -15°C. A high vacuum condition, which was pumped for 0.5 hour, was applied in the metallization procedure. The Al feeding speed was 7 kg Al per ton material. Selected film properties are reported in FIG. 3 and Table 2.

Table 1. Layer compositions of films according to FIG. 2

Table 1. Layer compositions of films according to FIG. 2

(Continued)

** A propylene homopolymer available from LyondellBasell.

*** A propylene terpolymer available from The Polyolefin Company.

**** An antiblocking polypropylene master batch available from CONSTAB, Germany. ***** A masterbatch available from Giriraj, containing 60% hydrocarbon resin.

Table 2. Properties of example I samples

* WVTR (38°C, 90% RH) g/ (m²-d)]

** OTR[(23°C, 0% RH) cm3(STP)/(m²-d)] [0090] The films I-R, I- 1, 1-2, 1-3 and 1-4 contain about 0%, 5%, 10%, 15%, and 20% of hydrocarbon resin, respectively. The films were prepared with about 1:3:1 relative thickness of metallization layercore layersealant layer and a total thickness of about 25 microns.

[0091] The surface tension on the metallized side of films I-R, 1-1, 1-2, 1-3 and 1-4 was measured over time according to an ExxonMobil method based on ASTM D2578 as described above. The metallized films were stored all the time under controlled environment at a temperature of 23±2°C and a humidity of 50+10%. FIG. 2 illustrates the surface tension changes over time for the samples. It shows that, for more than 60 days after metallization, the metallized film with a hydrocarbon resin doped layer maintains a higher surface tension on the metal layer over time than the reference without hydrocarbon resin in the metallization layer.

[0092] The oxygen transmission rate of the films after metallization was measured at 23°C, 0% relative humidity (RH), according to ASTM D3985-17. Table 2 illustrates the oxygen transmission rate for some of the samples. The data illustrates that, with a hydrocarbon resin doped metallization layer, the films can have reduced oxygen transmission rates by as much as 39% ((26.7- 16.3)/26.7* 100). A significant improvement can be obtained with 5% hydrocarbon resin in the metallization layer (film I- 1), which gives oxygen transmission values among the lowest within the hydrocarbon concentration range tested.

[0093] The water vapor transmission rate of the films after metallization was measured at 38°C, 90% RH according to ASTM F1249-13. Table 2 illustrates the water vapor transmission rate for some of the samples. The data illustrates that with a hydrocarbon resin doped metallization layer, all of the films have water vapor transmission rates are below of 0.3 g/m²/d, which is a typical performance value in the industry. The presence of hydrocarbon resin up to 15% in the metallized skin does not affect WVTR significantly.

[0094] Example II. Another set of films according to the structure of FIG. 2 were produced and metallized on different equipment than Example I. The II-R, II- 1, II-2, and II-3 samples were firstly coextruded and casted on a 3 layer industrial scale W&H cast line (die width 2 m) using the materials in Table 3 to form transparent cast polypropylene (CPP) films. The first chill roll temperature was 38°C, and second chill roll temperature was 34°C. The line speed was 169 m/min. All films were corona- treated in line with film making. The film rolls were then kept in a 40°C warm room for 1 day for further stabilization. The film rolls were then put into a metallizer to deposit 99.99% A1 on the doped metallization layer 202 with a line speed of 6.6 m/s and a chill roll temperature of -15°C. A high vacuum condition, which was pumped by 0.5 h, was applied in the metallization procedure. The A1 feeding speed is controlled for each sample to have an equivalent resistance. Finally, the metalized CPP samples were formed. The film rolls were slit to proper size. The film property is reported in Table 4.

Table 3. Another set of layer compositions of films according to FIG. 2

** A propylene homopolymer available from Sinopec.

*** A propylene terpolymer available from The Polyolefin Company.

**** An antiblocking polyethylene master batch available from CONSTAB, Germany*****

A masterbatch available from Giriraj, containing 60% hydrocarbon resin. Table 4. Properties of example II samples

* WVTR (38°C, 90% RH) g/ (m²-d)]

** OTR[(23°C, 0% RH) cm3(STP)/(m²-d)]

[0095] The films II-R, II- 1, II-2 and II-3 contain about 0%, 5%, 10% and 15% of hydrocarbon resin, respectively. The films were prepared with about 1:3:1 relative thickness of metallization layercore layersealant layer and a total thickness of about 25 microns.

[0096] Table 4 illustrates the impact of doping the metallization layer with the hydrocarbon resin on the OTR (23°C, 0% RH) and the WVTR (38°C, 90% RH). The conclusions are similar to Example I. Table 4 illustrates that about 5% hydrocarbon resin or more in the metallization layer is enough to decrease the OTR of the metallized film by 36% ((47.9-30.8)/47.9*100). Table 4 illustrates that addition of hydrocarbon resin in the metallization layer has little to no impact on the WVTR of the metallized film.

[0097] Example III. Several films were produced according to the procedure in Example 1 and the composition of Table 5.

Table 5. Layer compositions of films according to FIG. 2

* A propylene terpolymer available from The Polyolefin Company.

** A propylene homopolymer available from LyondellBasell.

*** A propylene terpolymer available from The Polyolefin Company.

**** An antiblocking polypropylene master batch available from CONSTAB, Germany.

***** A masterbatch available from Giriraj, containing 60% hydrocarbon resin.

[0098] On the metallized side of the films III-R, III- 1 , III-2 and III-3, the films were then laminated to a 19 pm thick BOPP film. A 2-component solventless polyurethane adhesive from Huntsman was used. The laminated films were then passed through a vertical form fill and seal (VFFS) line in order to evaluate the impact of the packaging operation on the barriers. OTR (23 °C, 0% RH) was measured on the laminates before and after the VFFS packaging step (Table 6). Table 6. Properties of example III samples

* OTR[(23°C, 0% RH) cm3(STP)/(m²-d)]

[0099] The range of OTR values measured is significantly lower than for Example I and Example II, likely because the lamination with a polyurethane adhesive enhances the barrier performance of the metal layer.

[0100] Table 6 shows that the addition of 5% hydrocarbon resin in the metallization layer yields a decrease of oxygen transmission of more than 30% for the laminate, while higher concentrations appears to be less effective in this example.

[0101] Table 6 also shows that OTR values of the laminates increase after passing them though the packaging machine. But the barrier improvements brought by the hydrocarbon resin in the metallization layer remain.

[0102] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of“comprising,”“containing,” or“including” various components or steps, the compositions and methods can also“consist essentially of’ or“consist of’ the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form,“from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles“a” or“an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces.

Claims

CLAIMS The invention claimed is:

1. A multilayer metallized cast polypropylene film comprising:

a doped metallization layer comprising about 75 wt % to about 99 wt % of a polypropylene copolymer and about 1 wt % to about 25 wt% of a hydrocarbon resin; and a metal layer on a first surface of the doped metallization layer.

2. The film of claim 1 further comprising:

a sealant layer; and

a core layer between the doped metallization layer and the sealant layer, wherein the core layer is on a second surface of the doped metallization layer that opposes the first surface of the doped metallization layer.

3. The film of claim 2, wherein the core layer comprises polypropylene at about 90 wt% to about 100 wt%, and wherein the sealant layer comprises a propylene-based elastomer at about 90 wt% to about 100 wt%.

4. The film of any preceding claim, wherein the doped metallization layer comprises about 90 wt% to about 99 wt% of the polypropylene copolymer and about 1 wt% to about 10 wt% of the hydrocarbon resin.

5. The film of any preceding claim, wherein the multilayer film has an oxygen transmission rate that is at least 20% less than an oxygen transmission rate of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer.

6. The film of one of claims 1-3, wherein the doped metallization layer comprises about 80 wt% to about 90 wt% of the polypropylene copolymer and about 10 wt% to about 20 wt% of the hydrocarbon resin, wherein the polypropylene copolymer is the random propylene copolymer.

7. The film of claim 6, wherein the metal layer of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metal layer of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer, wherein both films have aged under same conditions.

8. The film of one of claims 6-7, wherein the metal layer of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metal layer of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 40 days at 23±2°C and 50%±10% humidity.

9. The film of one of claims 6-8, wherein the metal layer of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metal layer of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 80 days at 23±2°C and 50%±10% humidity.

10. A method comprising:

casting a doped metallization polymer melt to form a doped metallization layer, wherein the doped metallization polymer melt comprises about 75 wt% to about 99 wt% of a polypropylene copolymer and about 1 wt% to about 25 wt% of a hydrocarbon resin; and metallizing a first surface of the doped metallization layer to form a multilayer film.

11. The method of claim 10 further comprising:

casting a core polymer melt and a sealant polymer melt with the doped metallization polymer melt to form a film with a core polymer layer between the doped metallization layer and a sealant polymer layer, wherein after metallizing the core layer is on a second surface of the doped metallization layer that opposes the first surface of the doped metallization layer.

12. The method of claim 11, wherein the core polymer melt comprises polypropylene at about 90 wt% to about 100 wt%, and wherein the sealant polymer melt comprises a propylene- based elastomer at about 90 wt% to about 100 wt%.

13. The method of one of claims 10-12, wherein the doped metallization polymer melt comprises about 90 wt% to about 99 wt% of the polypropylene copolymer and about 1 wt% to about 10 wt% of the hydrocarbon resin.

14. The method of claims 13, wherein the multilayer film has an oxygen transmission rate that is at least 25% less than an oxygen transmission rate of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer.

15. The method of one of claims 10-12, wherein the doped metallization layer comprises about 80 wt% to about 90 wt% of the polypropylene copolymer and about 10 wt% to about 20 wt% of the hydrocarbon resin, wherein the polypropylene copolymer is a random propylene copolymer.

16. The method of claim 15, wherein the metallized surface of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metallized surface of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer, wherein both films have aged under same conditions.

17. The method of one of claims 15-16, wherein the metallized surface of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metallized surface of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 40 days at 23±2°C and 50%±10% humidity.

18. The method of one of claims 15-17, wherein the metallized surface of the multilayer film has a surface tension that is up to a 20% surface tension increase over a surface tension of a metallized surface of an identical multilayer film except with no hydrocarbon resin in the doped metallization layer after both films have aged 80 days at 23±2°C and 50%±10% humidity.