Patent Description:
Polymeric film substrates may be coated with various materials to impart various desired properties to the substrates. These properties include, but are not limited to, sealability, water and grease resistance, adhesion, and tear or puncture resistance. In some instances, the coating materials may incorporate metals or metal oxides. These types of coatings are particularly important in the flexible packaging industry, which may utilize polymeric film substrates. Packaging items such as pouches and bags used for storing food may involve polymeric film substrates. In these items, barrier properties may be desired in the polymeric film substrates to improve durability of the package and quality and shelf life of the package contents.

Metal and metal oxide coatings are used to improve the barrier of plastic films used in packaging. However, the performance of these coatings tends to diminish during processing of the film. For example, the film is kept under tension when it is wound and unwound during printing and lamination processes. The tension can cause cracking of the coatings deposited on the film. Additionally, the surface of the film is also in contact with rollers and guides that can abrade and scratch the coatings. These damages to the coating can affect the barrier properties of the coated polymeric films with regards to water vapor and oxygen transmission rates.

<CIT> discloses barrier films comprising: (i) a substrate comprising at least first and second coatings on the substrate; (ii) the first coating comprising an inorganic oxide, metal oxide or metallic coating; and (iii) the second coating capable of adhering to the substrates, wherein the second coating is polymeric.

<CIT> discloses coating composition comprising a silylated polyvinyl alcohol, a colloidal silica and a water-dispersible or water-soluble aminoplast resin in an aqueous vehicle may be coated on a substrate with a layer of an inorganic compound to form a gas barrier lamella.

Accordingly, there is a continual need for a coated film structure that exhibits improved barrier performance to water vapor and oxygen. Moreover, there is a need for a coated film structure, which includes aluminum oxide that exhibits favorable water vapor and oxygen transmission rates.

Embodiments of the present disclosure provide a coated film structure including a substrate layer, an overcoat layer, and at least one intermediate layer disposed between the substrate layer and the overcoat layer. The substrate layer includes a polymer film substrate, the overcoat layer includes at least one acid-functional copolymer, and at least one intermediate layer includes aluminum oxide.

According to one or more embodiments, the coated film structure has an oxygen transmission rate of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM D3985. Further, the coated film structure has a water vapor transmission rate of less than <NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM E-<NUM>. In some particular embodiments, the coated film structure has an oxygen transmission rate of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM D3985 and a water vapor transmission rate of less than <NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM E-<NUM>.

The acid-functional copolymer is a hydrophobic styrene copolymer selected from the group of styrene-acrylic copolymers stabilized with alkali-soluble resins (ASR), acid-functional styrene-acrylic copolymers, alkali-soluble acrylic copolymers, and carboxylated styrene-butadiene rubber (SBR) dispersions.

The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where aspects of the structure are indicated with corresponding reference numerals and in which:.

Reference will now be made in detail to various embodiments of the coated structures. The components of the coated film structure include a first substrate layer including at least one polymer film, an intermediate layer including aluminum oxide, and an overcoat layer including an acid-functional copolymer. The coated film structures of various embodiments may exhibit increased barrier performance to moisture vapor and oxygen.

In various embodiments, the substrate layer includes at least one polymer film substrate. The polymer film substrate may be a polyester, a polyamide, or a polyolefin. For example, the substrate may include at least one polyethylene or polypropylene, a polyester substrate, or combinations thereof. By way of example and not limitation, the polymer film may comprise polyethylene, polypropylene, biaxially oriented polyethylene terephthalate (BOPET), biaxially oriented polypropylene (BOPP), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polypropylene, biaxially oriented polyamide, nylon, or polyvinyl chloride. In certain embodiments, the polymer substrate includes polyester, such as BOPET. According to other embodiments, the polymer substrate includes a polypropylene. Suitable polypropylenes include, but are not limited to, BOPP.

In one or more embodiments, the substrate layer has a thickness from <NUM> to <NUM>. In other embodiments, the substrate layer has a thickness from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. Coated film structures that have too thin of a substrate layer may be more susceptible to punctures or tears. Coated film structures that have too thick of a substrate layer may have inadequate flexibility and the coatings may be less durable to deformation.

One or both of the surfaces of the polymer film substrate may be surface-treated. Surface treatments may, for example, improve receptivity of the polymer film substrate to metallization, coatings, printing inks, lamination, or combinations thereof. By way of example and not limitation, one or both surfaces of the polymer film substrate may be subjected to one or more of a corona discharge treatment, a flame treatment, a plasma treatment, a chemical treatment, or the like. Chemical treatments include chemical etching with acids, bases, or oxidizing agents. The chemical treatment used for chemical etching may include nitric acid, potassium chromate, trichloric acid, or combinations thereof.

The coated film structure of various embodiments includes at least one overcoat layer including an acid-functional copolymer. As used herein, the term "acid-functional copolymer" refers to a copolymer that includes at least one comonomer including one or more acid-functional groups. In some embodiments, the acid-functional copolymer is an alkali-soluble stabilizing resin used to prepare a styrene-acrylic copolymer. Examples of monomers including one or more acid-functional groups include, but are not limited to, acrylic acid, methacrylic acid, β-carboxyethyl acrylate, fumaric acid, maleic acid, and monoalkyl esters of dibasic acid/anhydrides. In various embodiments, the acid-functional copolymer includes an acrylic acid comonomer.

In various embodiments, barrier functionality for resistance to water can be measured by the Cobb Sizing Test, as defined in ASTM D-<NUM> (TAPPI T-<NUM>). In various embodiments, the coated substrate exhibits a Cobb Value (<NUM> minute exposure) less than or equal to about <NUM>, less than or equal to about <NUM>, or less than or equal to about <NUM> after a Cobb test of <NUM> minutes duration. The acid-functional copolymer can be, by way of example and not limitation, a carboxylated styrene-butadiene rubber (SBR), an acid-functional styrene-acrylic copolymer, an alkali-soluble acrylic copolymer, or a styrene (meth)acrylic polymer stabilized with alkali-soluble resins, such as those described in <CIT>. In some embodiments, the acid-functional copolymer may be prepared in accordance with the teachings of <CIT>, <CIT>, and <CIT>.

In some embodiments, the acid-functional copolymer is a copolymer including an acrylic comonomer and a styrene comonomer. The acid-functional copolymer can include, for example, from about <NUM> wt% to about <NUM> wt% styrene, from about <NUM> wt% to about <NUM> wt% styrene, from about <NUM> wt% to about <NUM> wt% styrene, from about <NUM> wt% to about <NUM> wt% styrene, from about <NUM> wt% to about <NUM> wt% styrene, from about <NUM> wt% to about <NUM> wt% styrene, or about from about <NUM> wt% to about <NUM> wt% styrene. The acid-functional copolymer can include, for example, from about <NUM> wt% to about <NUM> wt% acrylic comonomer, from about <NUM> wt% to about <NUM> wt% acrylic comonomer, from about <NUM> wt% to about <NUM> wt% acrylic comonomer, from about <NUM> wt% to about <NUM> wt% acrylic comonomer, or from about <NUM> wt% to about <NUM> wt% acrylic comonomer. Other amounts of styrene and acrylic comonomers are contemplated, depending on the particular embodiment.

The amount of styrene in particular can impact the glass transition temperature (Tg) of the acid-functional copolymer. In particular, as the styrene content of the acid-functional copolymer increases, the Tg of the acid-functional copolymer also increases. In various embodiments, the acid-functional copolymer has a Tg of from about -<NUM> to about <NUM>, from about -<NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about -<NUM> to about <NUM>, from about -<NUM> to about <NUM>, or even from about -<NUM> to about <NUM>.

In various embodiments, the acid-functional copolymer has an acid value of about <NUM> mgKOH/g to about <NUM> mgKOH/g, from about <NUM> mgKOH/g to about <NUM> mgKOH/g, from about <NUM> mgKOH/g to about <NUM> mgKOH/g, or from about <NUM> mgKOH/g to about <NUM> mgKOH/g. In some embodiments, such as embodiments in which the acid-functional copolymer is an alkali soluble acrylic copolymer, the acid value may be from about <NUM> mgKOH/g to about <NUM> mgKOH/g. In various embodiments, the acid-functional copolymer has a molecular weight (MW) of greater than about <NUM>,<NUM>/mol, greater than about <NUM>,<NUM>/mol, or even greater than about <NUM>,<NUM>/mol. In still other embodiments, such as embodiments in which the acid-functional copolymer is an alkali soluble acrylic copolymer, the molecular weight may be from about <NUM>,<NUM>/mol to about <NUM>,<NUM>/mol.

The overcoat layer further includes a crosslinker. The crosslinker may comprise a multivalent metal salt. For example, the crosslinker may be a transition metal ion. The crosslinker may, in some embodiments, comprise a metal oxide, such as zirconium oxide, zinc oxide, iron oxide, aluminum oxide, copper oxide, and complexes thereof.

In some embodiments, the amount of crosslinker can vary depending on the acid functionality of the acid-functional copolymer. In particular, according to some embodiments, a ratio of moles of crosslinker to acid functionality of the acid-functional copolymer is less than about <NUM>:<NUM>. For example, the ratio of moles of crosslinker to acid functionality of the acid-functional copolymer can be from about <NUM>:<NUM> to about <NUM>:<NUM>, from about <NUM>:<NUM> to about <NUM>:<NUM>, or from about <NUM>:<NUM> to about <NUM>:<NUM>.

The overcoat layer may also optionally include one or more other additives, including, but not limited to, biocides, thickeners (also referred to herein as rheology modifiers), defoamers, plasticizers, and/or co-solvents, including but not limited to alcohols. Suitable biocides may include, by way of example and not limitation, those commercially available under the trade name PROXEL®, including PROXEL® GXL <NUM>%, available from Lonza Group (Basel, Switzerland).

In some embodiments, the overcoat layer includes a thickener selected from the group consisting of water swellable polymers. The particular amount of thickeners included in the overcoat layer can vary depending on the particular embodiment, and can depend on, among other factors, the type of thickener used as well as the desired viscosity of the overcoat layer. Water swellable polymers can be selected from the group consisting of natural, semisynthetic or synthetic water swellable polymers, such as polyacrylates, polymethacrylates, polyacrylamides, polymethacrylamides, polyurethanes and co-polymers thereof, polysaccharides, cellulose ethers, gums, and mixtures thereof. In some embodiments, the thickener may be selected from the group consisting of inorganic clays, cellulosic polysaccharides, synthetic hydrocarbon polymers, biopolymer polysaccharides, acrylic copolymers, polyacrylate ammonium salts, polyether carboxylate polymers, non-associative thickeners and associative thickeners, and base-neutralized ethylene acrylic acid copolymers.

In one or more embodiments, the overcoat layer has a dry coat weight of from about <NUM>/m<NUM> to about <NUM>/m<NUM>. In other embodiments, the overcoat layer has a dry coat weight of from about <NUM>/m<NUM> to about <NUM>/m<NUM>; from about <NUM>/m<NUM> to about <NUM>/m<NUM>; or from about <NUM>/m<NUM> to about <NUM>/m<NUM>. In further embodiments, the overcoat layer may comprise at least <NUM>% by dry coat weight of acid-functional copolymer, or at least <NUM> by dry coat weight of acid-functional copolymer. Said another way, in other embodiments, the overcoat layer may comprise from <NUM> to <NUM>% by dry coat weight of acid-functional copolymer.

Referring to <FIG>, in one or more embodiments, a coated film structure <NUM> comprises at least one intermediate layer <NUM> disposed between the substrate layer <NUM> and the overcoat layer <NUM>. The intermediate layer <NUM> may be, for example, disposed on the substrate layer <NUM>. The intermediate layer <NUM> may be in contact with the substrate layer <NUM>, the overcoat layer <NUM>, or both.

According to one or more embodiments, the intermediate layer <NUM> may include metals, metal oxides, or both. In at least one embodiment, the intermediate layer <NUM> comprises aluminum oxide. The intermediate layer <NUM> may have a thickness of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

In various embodiments, the coated film structure may further comprise at least one coating layer <NUM>. In at least one embodiment, at least one coating layer <NUM> is located between the polymer film substrate and the intermediate layer <NUM>. In other embodiments, at least one additional coating layer <NUM> may be applied to the overcoat layer <NUM> in such a way that the additional coating layer <NUM> does not contact the substrate or intermediate layer <NUM>. In still other embodiments, two or more additional coating layers <NUM> may be included in the coated film structure. The additional coating layer <NUM> may be, for example, one of the overcoat formulations described above and applied between the polymer film substrate and the intermediate layer <NUM>. The additional coating layer <NUM> may include, for example, a polyvinyl alcohol, a polyurethane, a polyolefin or mixtures thereof. Similar to the overcoat layer <NUM>, the additional coating layer <NUM> may optionally include one or more additives, such as biocides, adhesion enhancers, crosslinking agents, or the like. In embodiments in which an additional coating layer <NUM> and an overcoat layer <NUM> are employed, the additional coating layer <NUM> and the overcoat layer <NUM> may have the same formulation, or may have different formulations.

Referring to <FIG>, in one or more embodiments, a coated film structure <NUM> comprises a substrate layer <NUM>, a coating layer <NUM>, an intermediate layer <NUM>, and an overcoat layer <NUM>. The coating layer <NUM> is disposed between the intermediate layer <NUM> and the substrate layer <NUM> such that it does not contact the overcoat layer <NUM>. Still referring to <FIG>, the intermediate layer <NUM> is not in contact with the substrate layer <NUM> because of the placement of the intervening coating layer <NUM>.

In one or more embodiments, the at least one coating layer <NUM> has a dry coat weight of from about <NUM>/m<NUM> to about <NUM>/m<NUM>. In other embodiments, the at least one coating layer <NUM> has a dry coat weight of from about <NUM>/m<NUM> to about <NUM>/m<NUM>; from about <NUM>/m<NUM> to about <NUM>/m<NUM>; or from about <NUM>/m<NUM> to about <NUM>/m<NUM>. The combined coat weights of all coating layers <NUM> are less than or equal to about <NUM>/m<NUM>, less than or equal to about <NUM>/m<NUM>, or even less than or equal to about <NUM>/m<NUM>.

In one or more embodiments, the coated film structure further includes at least one layer including a laminate adhesive. In other embodiments, the coated film structure further comprises a second substrate layer. The laminate adhesive may be located in the overcoat layer <NUM> or in an additional coating layer <NUM>. In other embodiments, the laminate adhesive may be located in a layer between the first substrate layer <NUM> and the second substrate layer. Laminate adhesives include polyurethane based adhesives that can be either single component or two component adhesives where the degree of crosslinking is determined for a particular end use. Suitable adhesives include, as a non-limiting example, those commercially available under the tradename Loctite LIOFOL® (including, for example, Loctite LIOFOL® LA <NUM> / LA <NUM>), available from Henkel AG & Company (Düsseldorf, Germany). Suitable adhesives also include, by way of example and not limitation, those with bond strengths between <NUM> Newtons per inch (N/inch) to <NUM> N/inch.

In various embodiments, the coated film structure exhibits improved barrier properties to oxygen and water vapor as compared to structures including metalized barrier layers alone. For example, various embodiments of the coated film structure exhibit oxygen transmission rates of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM D3985. In embodiments, the coated film structure may exhibit oxygen transmission rates of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM>, of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM>, of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM>, of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM>, or of less than about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM D3985. For example, the coated film structure may exhibit oxygen transmission rates of from about <NUM><NUM>/m<NUM>/day to about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM>, from about <NUM><NUM>/m<NUM>/day to about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM>, or from about <NUM><NUM>/m<NUM>/day to about <NUM><NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM D3985.

In one or more embodiments, the coated film structure has a water vapor transmission rate of less than <NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM E-<NUM>. In other embodiments, the coated film structure has a water vapor transmission rate of less than <NUM>/m<NUM>/day, less than <NUM>/m<NUM>/day, less than <NUM>/m<NUM>/day, or even less than <NUM>/m<NUM>/day at <NUM>% relative humidity and <NUM> as measured in accordance with ASTM E-<NUM>.

The improved barrier properties of embodiment coated film structures of the present disclosure may continue over the lifetime of the coated film structure. Gelbo flex testing (ASTM F392) measures the flex durability of flexible packaging materials. The flex durability can be quantified as the resistance of the barrier material against repetitive strain. In some embodiments, the oxygen barrier remains unchanged after <NUM> flexes.

Various synthesis methods are contemplated for making the coated film structures and constituent layers. The overcoat layer <NUM> or additional coating layers <NUM> may be prepared as a solution in organic solvents, inorganic solvents, or combinations thereof. Alternatively, each overcoat layer <NUM> or additional coating layer <NUM> may be prepared as an aqueous emulsion. The layer compositions, in solution or emulsion form, may be applied to the substrate or other layers of the coated film structure. In still other embodiments, the layer composition may be vaporized on applied to the coated film structure via vapor deposition.

The intermediate layer <NUM> may be deposited on the substrate layer <NUM> in any suitable way. For example, the intermediate layer <NUM> may be deposited on the polymer film substrate using chemical vapor deposition ("CVD"), physical vapor deposition ("PVD"), vacuum vapor deposition, or atomic layer deposition ("ALD"). In one particular embodiment, the intermediate layer <NUM> is deposited on the polymer film substrate by PVD.

In one embodiment, the overcoat layer <NUM> may be prepared by adding the constituent components to a mixing vessel and mixing at ambient temperatures until all of the components are uniform. However, it is contemplated that other methods for preparing the overcoat layer <NUM> may be employed, including methods of mixing the components at increased temperature, increased pressures, in the presence of solubilizing agents, or combinations thereof. As used herein, solubilizing agents include rheology modifiers, pH buffering agents, counter salts, or other compound that aid in the mixing of a uniform overcoat layer <NUM> composition.

The overcoat layer <NUM> can be applied using a gravure coating, flexographic coating, or other application methods. A reverse gravure kiss coating geometry may be used to minimize damage to the intermediate layer <NUM> or other layers. After the overcoat layer <NUM> is applied, it may be dried by hot air, radiant heat, ambiently dried, or any other suitable means to provide an adherent coated film structure. Additional coating layers <NUM> may also be applied and dried by similar methods.

After all layers of the coated film structure are applied, the coated film structure may be cured before its barrier properties are tested. The curing may occur ambiently or actively. Ambient curing involves leaving the coated film structure to rest at atmospheric conditions. Active curing may involve the application of heat, a vacuum, or electromagnetic radiation.

In order that various embodiments may be more readily understood, reference is made to the following examples, which are intended to illustrate various embodiments, but not limit the scope thereof.

Various example coated film structures comprising a BOPET polymer film substrate were prepared with an aluminum oxide (AlOx) intermediate layer and a styrene acrylic overcoat. Next, oxygen transmission rates, moisture vapor transmission rates, and water resistance were compared against two comparative examples. Comparative Example A is a BOPET polymer film substrate with an AlOx coating and no overcoat. Comparative Example B is a BOPET polymer film substrate with an aluminum oxide (AlOx) intermediate layer and an amorphous polyvinyl alcohol (PVOH) overcoat including <NUM> wt% deionized water, <NUM> wt% Nippon Goshsei G-POLYMER™ AZF8035Q, <NUM> wt% CYMEL® <NUM> (Allnex), <NUM> wt% PEI LOXANOL® MI6730 (BASF), <NUM> wt% orthophosphoric acid <NUM>%, <NUM> wt% formaldehyde <NUM>%, and <NUM> wt% PROXEL® GXL <NUM>%. The examples have an intermediate layer comprising AlOx disposed between the PET film substrate layer and the overcoat layer comprising styrene acrylic copolymer. The AlOx was applied by physical vapor deposition via thermal evaporation and reactive oxidation at a thickness of about <NUM>. All substrate films used were commercial grade packaging films with a thickness of <NUM>. The Tg and acid values of the styrene acrylic copolymer used in the styrene acrylic overcoats are summarized in Table <NUM>.

The overcoat formulations were prepared by mixing the components in a paddle mixer at room temperature until uniform. The liquid overcoat formulations were applied to the examples using a Klox proofer with a EPDM shore <NUM> rubber roller and a TR34 engraved roll from RK Printcoat Instruments.

The oxygen transmission rates of the coated film structure including an intermediate layer and an overcoat layer at <NUM>% relative humidity (RH) <NUM> were measured in accordance with ASTM D3985. Humidity was applied directly to the coated side of the substrate; the other side of the substrate was maintained at <NUM>% RH. The water vapor transmission rates were measured at <NUM> and <NUM>% relative humidity in accordance with ASTM E-<NUM>. Water resistance was measured by placing a drop of water on the film and removing the drop after five (<NUM>) minutes. The film was then rated from <NUM> to <NUM>, where <NUM> corresponds to the film being dissolved in the water and <NUM> corresponds to the film being unchanged by the presence of water. The oxygen transmission rates, water vapor transmission rates, and water resistance of the examples are summarized in Table <NUM>.

The data in Table <NUM> shows that the Examples demonstrate a marked improvement in water resistance over the Comparative Example B and improved OTR over uncoated AlOx (Comparative Example A).

Various example coated film structures comprising a PET polymer film substrate were prepared with an aluminum oxide (AlOx) intermediate layer and a styrene acrylic overcoat including a ZnO crosslinker (ZINPLEX <NUM>™) in the overcoat formulation. Next, oxygen transmission rates, moisture vapor transmission rates, and water resistance were measured. The AlOx was applied by physical vapor deposition via thermal evaporation and reactive oxidation at a thickness of about <NUM>. All substrate films used were commercial grade packaging films with a thickness of <NUM>. The formulations for the styrene acrylic overcoats are summarized in Table <NUM>, with amounts reported in weight percent.

The overcoat formulations were prepared as described above with respect to Examples <NUM>-<NUM>. The oxygen transmission rates, water vapor transmission rates, and water resistance were measured as described above and are summarized in Table <NUM>.

A comparison of the data in Tables <NUM> and <NUM> demonstrates that for Examples <NUM> and <NUM>, the OTR and the MVTR both decrease (improved barrier functionality) with the addition of the ZnO crosslinker. However, for Examples <NUM> and <NUM>, the OTR increased, but the MVTR decreased, indicating an improvement in water vapor barrier functionality but a decrease in oxygen transmission barrier functionality.

Various example coated film structures comprising a PET polymer film substrate were prepared with an aluminum oxide (AlOx) intermediate layer and a styrene acrylic overcoat optionally include a ZnO crosslinker (ZINPLEX <NUM>™) in the overcoat formulation. The compositions of the overcoat layers are provided in Table <NUM>.

This example illustrates that zinc crosslinking can be useful in improving OTR and/or WVTR when used in styrene acrylic overcoat formulations.

Various example coated film structures comprising a BOPET polymer film substrate were prepared with an aluminum oxide (AlOx) intermediate layer and a styrene acrylic overcoat optionally include a ZnO crosslinker (ZINPLEX <NUM>™) in the overcoat formulation. The compositions of the overcoat layers and resultant layered film properties are provided in Table <NUM>.

This example illustrates that the inclusion of ZnO crosslinkers in the overcoat formulation can improve OTR and WVTR. For many of the formulations above, it appears a preferred weight ratio of ZnO to acid groups is about <NUM> to <NUM>.

Various example coated film structures comprising a BOPET polymer film substrate were prepared with an aluminum oxide (AlOx) intermediate layer and an alkali-soluble resin overcoat optionally include a ZnO crosslinker (ZINPLEX <NUM>™) in the overcoat formulation. The compositions of the overcoat layers and resultant layered film properties are provided in Table <NUM>. All samples had a water resistance of <NUM>.

This example illustrates that the inclusion of ZnO crosslinkers in alkali-soluble resin overcoat formulations can improve OTR and WVTR. It appears that greater acid values provide greater improvement in OTR and WVTR.

Various example coated film structures comprising a BOPET polymer film substrate were prepared with an aluminum oxide (AlOx) intermediate layer and a carboxylated styrene-butadiene rubber overcoat optionally include a ZnO crosslinker (ZINPLEX <NUM>™) in the overcoat formulation. The compositions of the overcoat layers and resultant layered film properties are provided in Table <NUM>. All samples had a water resistance of <NUM>.

This example illustrates that the inclusion of ZnO crosslinkers in carboxylated styrene-butadiene rubber overcoat formulations can improve OTR and WVTR.

Some of the data from the foregoing examples were compiled into <FIG>, which is a plot of the change in OTR and WVTR (with zinc value minus without zinc value) as a function of the Tg of the polymer in the overcoat formulation. Delta values that are negative indicate an improvement in OTR or WVTR. The solid line is the fit to OTR, and the dashed like is the fit to WVTR. Preferably, the polymer in the overcoat formulation has a Tg of -<NUM> to <NUM>, more preferably -<NUM> to <NUM>, and most preferably -<NUM> to <NUM>.

In addition to the water resistance test used in Tables <NUM> and <NUM> a <NUM>-minute exposure Cobb test ASTM D-<NUM> (TAPPI T-<NUM>) was also conducted using some of the polymers to show their levels of hydrophobicity (Table <NUM>). To do this test a heavy coat weight of the polymer is applied to a paper surface. The absorption of water by the paper over a given surface area in <NUM> minutes is recorded in grams per square meter. The lower the number the greater the hydrophobicity.

It can be seen that in all cases except where the Tg is very high we obtain low cobbs and hydrophobic coatings. The high Tg gives a polymer which doesn't film form completely which accounts for its poor Cobb value.

Gelbo flex testing (ASTM F392-<NUM>(<NUM>)) measures the flex durability of flexible packaging materials. The flex durability can be quantified as the resistance of the barrier material against repetitive strain. The major drawback of AlOx coatings is how easily they are damaged by such flexing. Several of the examples on BOPET coated AlOx were subjected to <NUM>, <NUM>, <NUM>, and <NUM> flexes. Then, the oxygen transmission rate was measured after flexing. Compared to the uncoated AlOx coated films all the examples showed an improvement in maintaining barrier with flexing, Table <NUM>.

Unless otherwise indicated, the disclosure of any ranges in the specification and claims are to be understood as including the range itself and also anything subsumed therein, as well as endpoints.

Claim 1:
A coated film structure comprising:
a substrate layer comprising a polymer film substrate;
an overcoat layer comprising at least one hydrophobic styrene copolymer and a crosslinker, wherein the at least one hydrophobic styrene copolymer is selected from the group consisting of styrene-acrylic copolymers stabilized with alkali-soluble resins (ASR), alkali-soluble acrylic copolymers, acid functional styrene-acrylic copolymers, and carboxylated styrene-butadiene rubber (SBR) dispersions, and wherein the crosslinker is selected from the group consisting of: a multivalent metal salt and a metal oxide; and
at least one intermediate layer disposed between the substrate layer and the overcoat layer, the intermediate layer comprising aluminum oxide.