Claims:We claim:

1. An oxygen barrier coating composition for polymer substrates, comprising:
a. about 6.0% to 15.0% by weight of a vinyl amine modified polyvinyl alcohol;
b. about 0.1 to 2.0% by weight of at least a crosslinking agent;
c. about 0.5 to 4.0% by weight of at least one clay;
d. about 0.1% to 1.0% by weight of an additive such as a wetting agent, a defoaming agent or mixtures thereof; and
e. deionised water,
wherein the total solid content of the barrier coating composition is about 7.0 to 22.0% by weight, preferably about 9.0 to 12.0% by weight of the total composition,
wherein the molecular weight of the vinyl amine modified polyvinyl alcohol is about 10,000 – 20,000 dalton, more preferably about 12,000 – 18,000 dalton, and most preferably about 15,000 – 18,000 dalton.

2. The oxygen barrier coating composition according to claim 1, wherein the crosslinking agent is selected from epoxy resin, silicone modified epoxy resin.

3. The oxygen barrier coating composition according to claim 1, wherein the crosslinking agent is present preferably in an amount of about 0.1 to 2.0% by weight, more preferably about 0.1 to 0.5% by weight.

4. The oxygen barrier coating composition according to claim 1, wherein the clay is selected from a cationic nano clay or an anionic nano clay or mixture of both selected from hydrotalcite, modified hydrotalcite, montimorillonite, bentonite, vermiculite, or combinations thereof, wherein the clay is present preferably in an amount of about 0.5 to 4.0% by weight, more preferably about 1.0 to 2.0% by weight.

5. The oxygen barrier coating composition according to claim 1, wherein the aspect ratio of the clay is about 200 to 5000, preferably about 1000 to 2000, wherein the particle size of the clay is about 0.5 to 5 microns when the aspect ratio of the clay is about 200 to 5000, and particle size of the clay is about 0.5 to 1 micron, when the aspect ratio of the clay is about 1000 to 2000.

6. The oxygen barrier coating composition according to claim 1, wherein the pH of the barrier coating composition is about 8 to 12, preferably about 9 to 10.

7. The polymer substrate according to claim 1 is selected from biaxially oriented polyethylene terephthalate (BOPET), biaxially oriented polypropylene (BOPP).

8. A method of preparing a coating composition to impart oxygen barrier properties to a polymer film sunstrate, comprising the steps of:
a. dispersing about 0.5 to 4.0% by weight of at least one clay in deionised water;
b. homogenising said mixture in a high shear homogeniser with RPM of 2000 to 20000 for 5 to 30 minutes to form a clay dispersion;
c. adding 6.0 to 15.0% by weight of a vinyl amine modified polyvinyl alcohol to the clay dispersion;
d. dissolving the vinyl amine modified polyvinyl alcohol in the temperature range 80-95 ?C while stirring to form a composition;
e. cooling down the composition to room temperature;
f. optionally mixing about 0.1% to 1.0% by weight of additives such as a wetting agent, a defoaming agent or mixtures; and
g. mixing about 0.1 to 2.0% by weight of a crosslinking agent such as epoxy resin, silicone modified epoxy resin to the coating composition.

9. An oxygen barrier coating composition for a polymer film substrate, comprising:
a. about 0.5 to 4.0% by weight of at least one clay;
b. about 6.0% to 15.0% by weight of a vinyl amine modified polyvinyl alcohol;
c. about 0.1% to 1.0% by weight of an additive such as a wetting agent, a defoaming agent or mixtures thereof; and
d. deionised water,
wherein the total solid content of the barrier coating composition is about 7.0 to 22.0% by weight, preferably about 9.0 to 12.0% by weight of the total composition,
wherein the molecular weight of the vinyl amine modified polyvinyl alcohol is about 10,000 – 20,000 dalton, more preferably about 12,000 – 18,000 dalton, and most preferably about 15,000 – 18,000 dalton.

10. A composite oxygen barrier film, comprising:
a. a base substrate layer of a biaxially oriented polyethylene terephthalate (BOPET) or a biaxially oriented polypropylene (BOPP) film substrate or a biaxially oriented polyamide (BOPA); and
b. a barrier coating layer of claim 9, mixed with about 0.1 to 1.0% by weight a crosslinking agent such as epoxy resin, silicone modified epoxy resin, coextensively adjacent in direct contact with one side of the base substrate layer,
wherein the oxygen transmission rate (OTR) of the coated BOPET or BOPP film is about 0.04 to 2.0 cc/m2/day under conditions of Relative Humidity (RH) of about 0 to 80% at 23 ?C and WVTR of the coated BOPET or BOPP is about 5.0 to 30 g/m2/day under conditions of 23°C & relative humidity of 90%.

11. A method of making a composite oxygen barrier film, comprising the steps of:
a. providing a coating composition that includes a vinyl amine modified polyvinyl alcohol in an aqueous clay dispersion, optionally mixing additives such as a wetting agent, a defoaming agent;
b. cooling down the coating composition to room temperature 25-30?C;
c. mixing a crosslinking agent such as epoxy resin, silicone modified epoxy resin to the coating composition;
d. providing a base polymer substrate layer;
e. applying a coating composition onto a surface of the base substrate layer; and
f. exposing the base substrate layer to a temperature of about 50 -190?C, more preferably 90-170?C time effective for crosslinking the vinyl amine modified polyvinyl alcohol with the crosslinking agent, and drying.

Description:FIELD OF THE INVENTION:
The present invention relates to an oxygen barrier coating composition for packaging applications, specifically the invention relates to transparent flexible packaging applications.

BACKGROUND OF THE INVENTION:
Plastics films have been an essential part of packaging applications since long time now, especially for packaging of foods and other materials which need protection from moisture, air/oxygen, and from handling. Several suitable multilayer laminate structures have been used to provide barrier properties and other performance characteristics. These laminates may solely be plastic materials or be any combination of plastic, cellulosic, and metallic substrates, and often include one or more coating or adhesive layers.

Laminates which include polymeric films having metals or inorganic compounds, such as aluminium and silicon oxides, deposited on them have given good general barrier properties. However, they may lose their ability to prevent the ingress of oxygen altogether at high temperatures, for example when the packaged material is retorted in order to sterilise and/or cook it. Moreover, the inorganic layer of these types of laminate is rather brittle and lack of flex cracking resistance (crack or break when the laminate is flexed), resulting in a loss of the gas barrier properties.

Polyvinyl alcohol (PVOH), ethylene vinyl alcohol copolymer (EVOH) or blends thereof can be applied to packaging films as a moisture vapour and oxygen transmission baarrier layer. It is commonly used on Biaxially oriented polypropylene (BOPP) and biaxially oriented polyethylene terephthalate (BOPET) base layers in multilayer packaging films. As the PVOH or EVOH layer is clear, so the packaging film can be transparent. However, polyolefin or polyester packaging film coated with a PVOH or EVOH barrier layer has not been found to provide high quality of moisture vapour and oxygen barrier properties required for products that are very sensitive to oxygen/air or need to be stored for long period of time. Additionally, high humidity conditions can cause PVOH or EVOH coatings to absorb moisture or swell when in contact with water vapour/moisture, which can decrease the effectiveness of gas barrier coatings. Also the transparent PVOH or EVOH coatings lack of adhesion over the substrate is an issue.

US5776618A discloses a polymeric film structure produced by coating a surface of a polymeric substrate with a solution of a polyvinyl alcohol-vinyl amine copolymer, an aldehyde-containing crosslinking agent and a crosslinking promoting acid catalyst.

US2007031654A1 discloses a coating composition for providing substrates with oxygen barrier properties. The coating composition includes a copolymer of maleic acid and acrylic acid and a copolymer of vinyl alcohol and a vinylamine.

US20160024326A1 discloses oxygen barrier coatings on flexible substrates that comprise lower molecular weight PVOH and EVOH co-polymers.

EP2245092A1 discloses a composition for preparing a gas barrier coating comprising an aqueous dispersion of a clay and a polyvinyl alcohol and/or an ethylene vinyl alcohol copolymer and poly(ethyleneimine).

US9617059B2 and US9624020B2 disclose a composite barrier film that has a base layer of polyester with a barrier layer modified polyvinyl amine (mPVA). The mPVA is polyvinyl alcohol/polyvinyl amine copolymer crosslinked with citric acid and an optional additional crosslinking agent such as epichlorohydrin.

US2018311919A1 discloses a balloon with a pattern that comprises a polymeric gas barrier of polyvinyl alcohol/polyvinyl amine copolymer crosslinked with citric acid and an optional additional crosslinking agent such as epichlorohydrin and a heat-seal layer.

OBJECTS OF THE INVENTION:
The principal objective of the present invention is to provide an oxygen barrier coating for transparent flexible packaging that provides an oxygen transmission rate (OTR) of about 0.04 to 2.0 cc/m2/day under conditions of Relative Humidity (RH) of about 0 to 80% at 23 ?C and WVTR of the coated BOPET or BOPP is about 5.0 to 30 g/m2/day under conditions of 23°C & relative humidity of 90%.

Another objective of the present invention is to provide an oxygen barrier coating for transparent flexible packaging that provides excellent flex cracking resistance.

Yet another objective of the present invention is to provide an oxygen barrier coating for transparent flexible packaging that provides excellent water resistance.

A further objective of the present invention is to provide an oxygen barrier coating for transparent flexible packaging that exhibits excellent adhesion to polymeric substrates such as biaxially oriented polyethylene terephthalate (BOPET) and biaxially oriented Polypropylene (BOPP).

SUMMARY OF THE INVENTION:
The present invention provides an oxygen barrier coating composition for polymer substrates, comprising:
a. about 6.0% to 15.0% by weight of a vinyl amine modified polyvinyl alcohol;
b. about 0.1 to 2.0% by weight of at least a crosslinking agent;
c. about 0.5 to 4.0% by weight of at least one clay;
d. about 0.1% to 1.0% by weight of an additive such as wetting agent and defoaming agent or mixtures thereof; and
e. deionised water.

The total solid content of the barrier coating composition is about 7.0 to 22.0% by weight, preferably about 9.0 to 12.0% by weight of the total composition.

The polymer substrate can be selected from biaxially oriented polyethylene terephthalate (BOPET), biaxially oriented Polypropylene (BOPP), biaxially oriented polyamide (BOPA). The polymer substrate preferably is BOPET or BOPP.

The crosslinking agent can be an epoxy resin, silicone modified epoxy resin, which is present in the composition preferably in an amount of about 0.1 to 2.0% by weight, more preferably about 0.1 to 0.5% by weight.

The clay can be a cationic nano clay or an anionic nano clay or mixture of both selected from hydrotalcite, modified hydrotalcite, montimorillonite, bentonite, vermiculite, or combinations thereof. The clay is present preferably in an amount of about 0.5 to 4.0% by weight, more preferably about 1.0 to 2.0% by weight. The aspect ratio of the clay is about 200 to 5000, preferably about 1000 to 2000. The particle size of the clay is about 0.5 to 5 microns when the aspect ratio is about 200 to 5000, and particle size of the clay is about 0.5 to 1 micron, when the aspect ratio is about 1000 to 2000.

The pH of the barrier coating composition is about 8 to 12, preferably about 9 to 10.

A method of preparing the coating composition is also provided.

A composite oxygen barrier coated film incorporating the oxygen barrier coating of the present invention includes a base polymer substrate layer coated with the barrier coating composition. The Oxygen transmission rate (OTR) of the coated film is about 0.04 to 2.0 cc/m2/day under conditions of Relative Humidity (RH) of about 0 to 80% at 23 ?C and WVTR of the coated film is about 5.0 to 30 g/m2/day under conditions of 23°C & relative humidity of 90%.

The base polymer substrate layer is preferably a biaxially oriented polyethylene terephthalate (BOPET) substrate or a biaxially oriented polypropylene (BOPP) film substrate.

DETAILED DESCRIPTION OF THE INVENTION:
The preferred embodiments of the present invention will be described in detail with the following disclosure and examples. The foregoing general description and the following detailed description are provided to illustrate only some embodiments of the present invention and not to limit the scope of the present invention. The invention is capable of other embodiments and can be carried out or practiced in various other ways.

Unless otherwise specified, all the technical and scientific terms used herein have the same meaning as is generally understood by a person skilled in the art pertaining to the present invention. All the patents published patent applications referred to throughout the entire disclosure herein, unless specified otherwise, are incorporated by reference in their entirety.

It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from greater than 0 % by weight to about 25 % by weight should be interpreted to include not only the explicitly recited limits of greater than 0 % by weight to about 25 % by weight, but also to include individual values, such as 0.05 % by weight, 0.9 % by weight, 7 % by weight, 21 % by weight, etc., and sub-ranges, such as from about 1 % by weight to about 24 % by weight, from about 5 % by weight to about 20 % by weight, etc. Furthermore, when “about” is utilized to describe a value, this is meant to encompass minor variations (up to +/-10%) from the stated value.

Reference throughout this specification to “one embodiment,” “an embodiment,” “one example,” or “an example” means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” “one example,” or “an example” in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and/or sub-combinations in one or more embodiments or examples. In addition, it should be appreciated that if any figures are provided herewith, they are for explanation purposes to persons ordinarily skilled in the art and that the drawings of them are not necessarily drawn to scale.

In this specification, certain aspects of one embodiment include process steps and/or operations and/or instructions described herein for illustrative purposes in a particular order and/or grouping. However, the particular order and/or grouping shown and discussed herein are illustrative only and not limiting. Those of skill in the art will recognise that other orders and/or grouping of the process steps and/or operations and/or instructions are possible and, in some embodiments, one or more of the process steps and/or operations and/or instructions discussed above can be combined and/or deleted. In addition, portions of one or more of the process steps and/or operations and/or instructions can be re-grouped as portions of one or more other of the process steps and/or operations and/or instructions discussed herein. Consequently, the particular order and/or grouping of the process steps and/or operations and/or instructions discussed herein do not limit the scope of the disclosure.

The terms “oxygen barrier coating” or “barrier coating” or “oxygen barrier coating composition” or “barrier coating composition” or “coating composition” or “barrier composition” may be interchangeably used in the present disclosure to mean the coating composition of the present invention to be applied to a base polymeric substrate to impart oxygen barrier properties to the base polymeric substrate.

The terms “composite oxygen barrier film”, “composite barrier film”, “barrier film”, “oxygen barrier film” may be interchangeably used in the present disclosure to mean a polymeric substrate coated with the oxygen barrier coating composition of the present invention. The base polymeric substrate may be a single film layer, or it may be a laminate. When it is a laminate, the coating composition is applied coextensively adjacent in direct contact with one side of the base polymeric substrate.

Formulation of the oxygen barrier coating composition
The present invention provides an oxygen barrier coating composition for polymer substrates, comprising:
a. about 6.0% to 15.0% by weight of a vinyl amine modified polyvinyl alcohol;
b. about 0.1 to 2.0% by weight of at least a crosslinking agent;
c. about 0.5 to 4.0% by weight of at least one clay;
d. about 0.1% to 1.0% by weight of an additive such as wetting agent and defoaming agent or mixtures thereof; and
e. deionised water.

The total solid content of the barrier coating composition is about 7.0 to 22.0% by weight, preferably about 9.0 to 12.0% by weight of the total composition.

The crosslinking agent can be an epoxy resin, silicone modified epoxy resin, which is present in the composition preferably in an amount of about 0.1 to 2.0% by weight, more preferably about 0.1 to 0.5% by weight.

The clay is a nano clay, and can be a cationic nano clay or an anionic nano clay or mixture of both selected from hydrotalcite, modified hydrotalcite, montimorillonite, bentonite, vermiculite, or combinations thereof. The clay is present preferably in an amount of about 0.5 to 4.0% by weight, more preferably about 1.0 to 2.0% by weight. The aspect ratio of the clay is about 200 to 5000, preferably about 1000 to 2000. The particle size of the clay is about 0.5 to 5 microns when the aspect ratio is about 200 to 5000, and particle size of the clay is about 0.5 to 1 micron, when the aspect ratio is about 1000 to 2000. A representative example of such a clay is Closite Na+ available from BYK.

The pH of the oxygen barrier coating composition is about 8 to 12, preferably about 9 to 10.

In another embodiment of the invention, while formulating the oxygen barrier coating composition, crosslinking agent is not added, rather the crosslinking agent is added to the composition before applying the coating to the polymer substrate film.

The molecular weight of the vinyl amine modified polyvinyl alcohol is about 10,000 – 20,000 dalton, more preferably about 12,000 - 18,000 dalton, and most preferably about 15,000 – 18,000 dalton. A representative example of vinyl amine modified polyvinyl alcohol to be used in the composition of the present invention is Selvol Ultiloc 5003 available from Sekisui Specialty Chemicals America LLC.

Additives:
The additives present in the oxygen barrier coating composition of the present invention may contain a wetting agent, a defoaming agent or mixtures thereof.

A wetting agent such as silicon or an acrylic compound may be added. Suitable wetting agents include BYK331, BYK333, BYK348, BYK381 available from Big Chemie.

Examples of defoaming agents or defoamers or anti-foaming agents of this type include one or more of: Air Products Surfynol materials, mineral oil, silicone defoaming agents. Suitable types of defoaming agents include silicone based defoamers, alcohols, glycol ethers, mineral spirits, Surfynol materials, acetylene diol based defoamers, polysiloxane, and any combinations of two or more of these.

Defoaming agents that are essentially solvent free when used in an amount from 0.01 to 1.0 weight percent of composition formulation (solids + water) also are suitable. Although defoaming agent or defoamers or anti-foaming agents need not be solvent free to be suitable. Also in some cases higher levels are needed to achieve defoaming action but this higher amount needs to be balanced with any type of solvent used in the coating composition to avoid adverse affects. A particularly suitable defoamer is one having a combination of siloxane glycol, organosiloxane, and reaction product of silicon dioxide and organosiloxane polymer. Also suitable is one having in weight percent of the solids of the defoamer 55 polyglycol, 30 to 40 organosiloxane and the remainder siloxane glycol. Defoamers that are suitable are those available from DOW CORNING Dow Corning Corporate Center, Midland, Mich., U.S.A. which include: Antifoam FG-10 Emulsion; Antifoam H-10 Emulsion; Antifoam Y-30 Emulsion; 200® Fluid; 544 Antifoam Compound; FS-1265 Fluid; Antifoam 1400 Compound Antifoam 1410 Emulsion; Antifoam 1430 Emulsion; Antifoam 1510-US Emulsion Antifoam 1520-US Emulsion; Antifoam 2200; Antifoam 2210; 7305 Antifoam; Q2-2617 Diesel Antifoam; Q2-2647 Diesel Antifoam; Q2-2677 Diesel Antifoam; Q2-2600 Diesel Antifoam; Antifoam A Compound;. Antifoam AF Emulsion; Antifoam B Emulsion; .Antifoam C Emulsion; 2-3436 ANTIFOAM COMPOUND; 2-3522 ANTIFOAM COMPOUND; 2-3896 ANTIFOAM COMPOUND; 2-3898 ANTIFOAM COMPOUND; 2-3899 ANTIFOAM COMPOUND; 2-3900 ANTIFOAM COMPOUND; 2-3902 ANTIFOAM COMPOUND; 2-3911 ANTIFOAM; 2-3912 ANTIFOAM; 3160 ANTIFOAM COMPOUND; ANTIFOAM 1400; ANTIFOAM 1500; ANTIFOAM A COMPOUND; ANTIFOAM A COMPOUND-FOOD G RADE; Q2-4128 ANTIFOAM. Defoamers that are suitable that are available from LUBRIZOL Corporation Wickliffe, Ohio include: Foam Blast® RKA and Foam Blast® RKB defoamers. Defoamers that are suitable that are available from BYK-Chemie USA Inc. of 524 South Cherry Street, P.O. Box 5670, Wallingford, Conn. 06492-7651 Website: http://www.bvk-chemie.com include: BYK®-052; BYK®-057; BYK®-066 N; BYK®-088; BYK®-354; BYK®-392; BYK®-031; BYK®-032; BYK®-033; BYK®-034; BYK®-035; BYK®-036; BYK®-037; BYK®-038; BYK®-017; BYK®-018; BYK®-019; BYK®-020; BYK®-021; BYK®-022; BYK®-023; BYK®-024; BYK®-025; BYK®-028 A; BYK®-044; BYK®-045; BYK®-060 N; BYK®-065; BYK®-066 N; BYK®-067 A; BYK®-070; BYK®-071; BYK®-080 A; BYK®-088; BYK®-094; BYK®-141; BYK®-1610; BYK®-1615; BYK®-1650; BYK®-1660; Byketol®-WS; BYK®-011; BYK®-012; BYK®-051; BYK®-052; BYK®-053; BYK®-055; BYK®-057; BYK®-A 500; BYK®-A 501; and BYK®-A 530 defoamers. Defoamers that are suitable that are available from Tego Chemie Service GmbH a business unit of the Degussa AG, Tego Chemie Service GmbH, Goldschmidtstr. 100, 45127 Essen, Germany; Degussa Tego Coating and Ink Additives, 1111 South 6th Avenue, P.O. Box 1111, Hopewell, Va. 23838, USA include: TEGO® Foamex 3062, TEGO® Foamex 8050, TEGO® Foamex K 3, TEGO® Foamex 1488, TEGO® Foamex 7447, TEGO® Foamex 800, TEGO® Foamex 805, TEGO® Foamex 808, TEGO® Foamex 815, TEGO® Foamex 822, TEGO® Foamex 825, TEGO® Foamex 845, TEGO® Foamex 1495, TEGO® Foamex 8030, TEGO® Foamex 810, TEGO® Foamex 830, TEGO® Foamex 832, TEGO® Foamex 835, TEGO® Foamex 840, and TEGO® Foamex 842 defoamers.

Composite oxygen barrier film:
A composite oxygen barrier film includes a polymer base substrate layer. An oxygen barrier coating composition of the present invention applied coextensively adjacent in direct contact with one side of the base substrate layer.

The polymer base substrate layer can be any suitable polymer layer such as a biaxially oriented polyethylene terephthalate (BOPET) and biaxially oriented polypropylene (BOPP) film substrate.

The thickness of the polymer substrate film may vary depending upon the particular application and the type of polymer used to form the film. In general, the film thickness can be less than about 5 mils, preferably less than about 3 mils. In various embodiments of the invention, based on the application, the thickness of the polymer substrate film may be about 2 mils, about 1 mil, or about 0.5 mil.

The barrier coating composition of the present invention was found to be advantageous with the fact that they provide good oxygen barrier properties with reduced coating thicknesses, hence requiring less quantity of the barrier coating composition, resulting in reduced cost of production, enhanced transparency making them more suitable for packaging applications. Of course based on the need, higher barrier coating thicknesses may be employed in specific applications. Barrier coating thicknesses in the range of about 0.5 to about 1.0 gsm are preferred. More preferably, the thickness is about 0.7 to about 1.0 gsm.

In an “inline coating method” of the base polymer layer, in which the coatings are applied during the film manufacturing process and before it is heat-set. While in an “off-line” method, the base layer film completely is formed and then wet coating composition is applied to the completed base layer, is the preferred method for use of the coating disclosed. An anchor coat agent may be applied in advance to the surface of the above-mentioned substrates. The anchor coat agent is not particularly restricted but may be, for example, polyurethane-or polyester based adhesive for dry lamination. The substrate surface may also be subjected to such surface treatment as corona discharge treatment, sputtering treatment, high-frequency treatment, flame treatment, chromate treatment or solvent etching treatment. However, a person skilled in the art may use a suitable coating methods such as casting head, roll coating, air knife coating, gravure roll coating, doctor roll coating, doctor knife coating, curtain flow coating, spray, dipping and brushing techniques in order to coat the barrier coating composition onto the polymer substrate.

The method for the drying and heat treatment of the substrates after application of the aqueous coating composition by such a technique as mentioned above, there may be mentioned, for example, the infrared irradiation, hot air drying and like dry heat treatment methods. The temperature for the above drying and heat treatment is desirably 50-210°C, preferably 80-200°C and more preferably 90-170°C. The drying/ heat treatment time may vary depending on the temperature but in generally 5 seconds to 5 minutes, preferably 15 seconds to 1 minute.

The oxygen transmission rate (OTR) of the coated polymer substrate film (preferably BOPET or BOPP) is about 0.04 to 2.0 cc/m2/day under conditions of 23°C and relative humidity of 0-80% using Mocon OX-TRAN 2/22 and water vapour transmission rate (WVTR) of the coated polymer substrate film (preferably BOPET or BOPP) is about 5.0 to 30.0 g/m2/day under conditions of 23°C and relative humidity of 80% using Mocon PERMATRAM-W-3/34.

Examples:
The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the invention without being limited to the specific examples given here.

Method of Preparation of the oxygen barrier coating composition
The most preferred embodiments of the invention to prepare the oxygen barrier coating composition are given in the examples below.

In one embodiment of the invention, preparation of the coating composition comprises the following steps. About 0.5 to 4.0% by weight of at least one clay was dispersed in deionised water; said mixture was homogenised in a high shear homogeniser with RPM of 2000 to 20000 for 5 to 30 minutes to form a clay dispersion; about 6.0 to 15.0% by weight of vinyl amine modified polyvinyl alcohol was added to the clay dispersion, and the vinyl amine modified polyvinyl alcohol dissolved in the clay dispersion in the temperature range of 80-95 ?C while stirring to form a composition; the composition was cooled down to room temperature; about 0.1% to 1.0% by weight of additives such as wetting agent and defoaming agent was mixed after cooling down of composition, about 0.1 to 2.0% by weight a crosslinking agent such as epoxy resin, silicone modified epoxy resin was added to the coating composition.

In another embodiment of the invention, the crosslinking agent was not mixed with the formulation at the time of preparation of the coating composition. Rather the crosslinking agent is added to the composition before applying the coating to the polymer substrate film.

Barrier Coating compositions and Composite oxygen barrier film employing the coating composition

Example 1 - 6.
A composite oxygen barrier film was prepared by providing a base substrate layer of a biaxially oriented polyethylene terephthalate (BOPET) film substrate of thickness 0.5 mil; applying the barrier coating composition prepared with the compositions of Examples 1 to 6 below onto a surface of the base substrate layer; and exposing the base substrate layer to a temperature of about 50 -190 ?C time effective for crosslinking the vinyl amine modified polyvinyl alcohol in the caoating composition with the crosslinking agent, and drying. The coating thickness of the barrier coating composition on the substrate was 0.9 gsm.

Table 1
Example No. DM Water (Wt%) Vinyl modified PVOH (Wt%) Clay (Wt%) Cross linking agent (Wt%) Wetting agent & Defoamer (Wt%)
1 87.7 12 0 0.2 0.1
2 89.8 9 1.0 0.1 0.1
3 88.8 10 1.0 0.1 0.1
4 86.8 12 1.0 0.1 0.1
5 89.7 9 1.0 0.2 0.1
6 88.7 10 1.0 0.2 0.1

Example 7 - 12.
In the Examples 7-12, the crosslinking agent was not mixed with the formulation at the time of preparation of the coating composition, but the crosslinking agent was mixed with the composition immediately before applying the coating to the polymeric substrate. A composite oxygen barrier film was prepared by providing a base substrate layer of a biaxially oriented polyethylene terephthalate (BOPET) film substrate of thickness 0.5 mil; applying the barrier coating composition of Examples 7-12 (i.e. the crosslinking agent was mixed with the composition immediately before applying the coating) onto a surface of the base substrate layer; and exposing the base substrate layer to a temperature of about 50 -190 ?C time effective for crosslinking the vinyl amine modified polyvinyl alcohol with the crosslinking agent, and drying. The coating thickness of the barrier coating composition on the substrate was 0.9 gsm.

Table 2
Example No. DM Water (Wt%) Vinyl modified PVOH (Wt%) Clay (Wt%) Cross linking agent (Wt%) Wetting agent & Defoamer (Wt%)
7 86.7 12 1.0 0.2 0.1
8 87.2 12 0.5 0.2 0.1
9 89.6 9 1.0 0.3 0.1
10 88.6 10 1.0 0.3 0.1
11 86.6 12 1.0 0.3 0.1
12 85.7 12 2.0 0.2 0.1

Example 13 – 17.
In the example 13-17, the crosslinking agent was mixed with the composition immediately before applying the coating to the polymeric substrate. A composite oxygen barrier film was prepared by providing a base substrate layer of biaxially oriented polypropylene (BOPP) film substrate of thickness 0.5 mil; applying the barrier coating composition of examples 13-17 (i.e. crosslinking agent mixed immediately before applying the coating) onto the surface of the base substrate layer; and exposing the base substrate layer to a temperature of about 50-190°C time effective for crosslinking the vinyl amine modified polyvinyl alcohol with the crosslinking agent, and drying. The coating thickness of the barrier coating composition on the substrate was 0.9 gsm.

Table 3
Example No. DM Water (Wt%) Vinyl modified PVOH (Wt%) Clay (Wt%) Cross linking agent (Wt%) Wetting agent & Defoamer (Wt%)
13 87.2 12 0.5 0.2 0.1
14 86.7 12 1.0 0.2 0.1
15 88.7 10 1.0 0.2 0.1
16 89.7 9 1.0 0.2 0.1
17 86.6 12 1.0 0.3 0.1

Sample test result
The barrier coating composition evaluation results have been provided in the following Table 3.
Table 4
Example No. OTR (cc/m2/day) at 0% RH and 23 ?C
1 0.4
2 0.6
3 0.3
4 0.2
5 0.1
6 0.1
7 0.2
8 0.2
9 0.08
10 0.06
11 0.04
12 0.04
13 1.84
14 1.62
15 1.28
16 1.1
17 0.92

Advantages:
The barrier coating composition applied to polymeric substrate films provide excellent oxygen barrier properties, i.e. an oxygen transmission rate (OTR) of about 0.04 cc/m2.day, very good water resistance, flex cracking resistance, and adhesion.

Although the present disclosure is described in terms of certain preferred embodiments and examples, other embodiments and examples will be apparent to those of ordinary skill in the art, given the benefit of this disclosure, including embodiments and examples that do not provide all of the benefits and features set forth herein, which are also within the scope of this disclosure. It is to be understood that other embodiments may be utilized, without departing from the true spirit and scope of the present invention being indicated by the following claims.