BARRIER FILM

Abstract

A multi-layer polymeric film substrate comprising at least a core layer and a coextruded oxygen barrier layer wherein the film exhibits an oxygen transmission rate (OTR) when measured in accordance with ASTM F1927-14 of below 200 cc/m.sup.2/24 hr at a relative humidity (RH) of 85% and/or of below 600 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%.

Claims

1. A multi-layer polymeric film substrate comprising at least a core layer and a coextruded oxygen barrier layer wherein the film exhibits an oxygen transmission rate (OTR) when measured in accordance with ASTM F1927-14 of below 200 cc/m.sup.2/24 hr at a relative humidity (RH) of 85% and/or of below 600 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%.

2. The multi-layer polymeric film substrate according to claim 1, having one or more of the following properties: (a) a modulus of elasticity in the machine direction (MD) of above 1500 N/mm.sup.2, preferably above 1750 N/mm.sup.2, preferably above 2000 N/mm.sup.2, preferably above 2100 N/mm.sup.2, more preferably above 2200 N/mm.sup.2, still more preferably above 2300 N/mm.sup.2, most preferably above 2400 N/mm.sup.2, for example above 2500 N/mm.sup.2; (b) a modulus of elasticity in the transverse direction (TD) of above 1500 N/mm.sup.2, preferably above 1750 N/mm.sup.2, preferably above 2000 N/mm.sup.2, preferably above 2100 N/mm.sup.2, more preferably above 2200 N/mm.sup.2, still more preferably above 2300 N/mm.sup.2, most preferably above 2400 N/mm.sup.2, for example above 2500 N/mm.sup.2; (c) shrinkage in the machine direction (MD) of below 15%, preferably below 12.5%, more preferably below 10%, still more preferably below 7.5%, most preferably below 7%; and (d) shrinkage in the transverse direction (TD) of below 15%, preferably below 12.5%, more preferably below 10%, still more preferably below 7.5%, most preferably below 7%.

3. The multi-layer polymeric film substrate according to claim having two or more of the properties (a) to (d).

4. The multi-layer polymeric film substrate according to claim 3, having three or more of the properties (a) to (d).

5. The multi-layer polymeric film substrate according to claim 4, having all four of the properties (a) to (d).

6. The multi-layer polymeric film substrate according to claim 1, wherein the core layer of the film comprises a substantially pure isotactic homopolymer.

7. The multi-layer polymeric film substrate according to claim 1, wherein during manufacture of the film substrate the oxygen barrier layer and the core layer have together been simultaneously stretched in both the machine and transverse directions of the film to over twenty five times the original areal dimensions of the film pertaining immediately before stretching.

8. The multi-layer polymeric film substrate according to claim 7, wherein during manufacture of the film substrate the oxygen barrier layer and the core layer have together been simultaneously stretched in both the machine and transverse directions of the film to over 50 times the original areal dimensions of the film pertaining immediately before stretching.

9. The multi-layer polymeric film substrate according to claim 1, wherein during manufacture of the film substrate the oxygen barrier layer is stretched at a temperature lower than the melting point of the oxygen barrier layer material.

10. A multi-layer polymeric film substrate according claim 1, wherein during manufacture of the film substrate the oxygen barrier layer is stretched in a solid state.

11. The multi-layer polymeric film substrate according to claim 1, wherein the crystal structure of the oxygen barrier layer is balanced in the machine and transverse directions of the film.

12. The multi-layer polymeric film substrate according to claim 1, wherein the oxygen barrier layer exhibits balanced strain-induced crystallinity.

13. The multi-layer polymeric film substrate according to claim 1, wherein during manufacture of the film substrate the oxygen barrier layer and the core layer have together been subjected to a balanced machine and transverse direction draw, either simultaneously or sequentially, to more than 25 times the original areal dimensions, or to 36 or more times the original areal dimensions, or to 49 or more times the original areal dimensions, of the film pertaining immediately before stretching.

14. The multi-layer polymeric film substrate according to claim 1, wherein the film core layer comprises a polyolefin film.

15. The multi-layer polymeric film substrate according to claim 14, wherein the film core layer comprises BOPP.

16. The multi-layer polymeric film substrate according to claim 1, wherein the OTR of the film when measured in accordance with ASTM F1927-14 is below 175 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%, below 150 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%, below 125 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%, below 100 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%, below 75 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%, below 50 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%, below 30 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%, below 600 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%, below 500 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%, below 400 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%, below 300 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%, below 200 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%, below 100 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%, and/or below 50 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%.

17. The multi-layer polymeric film substrate according to claim 1, wherein the film substrate is transparent.

18. The multi-layer polymeric film substrate according to claim 1, wherein the film substrate exhibits a wide angle haze (WAH) value of less than about 5, less than about 4, less than about 3 or less than about 2.

19. The A multi-layer polymeric film substrate according to claim 1, wherein the film substrate exhibits a gloss value (at 45°) of at least about 75, at least about 80, at least about 85 or at least about 90.

20. The multi-layer polymeric film substrate according to claim 1, wherein the oxygen barrier layer comprises EVOH.

21. The multi-layer polymeric film substrate according to claim 1, wherein the thickness of the barrier layer is in the range of from about 0.1 μm to about 5 μm.

22. The multi-layer polymeric film substrate according to claim 1, wherein the thickness of the film is from about 10 to about 240 μm.

23. The multi-layer polymeric film substrate according to claim 1, wherein the film substrate is provided with a functional and/or aesthetic coating.

24. The multi-layer polymeric film comprising the film substrate according to claim 1, wherein the film substrate is provided with one or more sealable skin layers.

25. A sealed package formed at least in part from the multi-layer polymeric film substrate according to claim 1.

26. An article of commerce wrapped or packaged in a material comprising the multi-layer polymeric film substrate according to claim 1.

27. A method for manufacturing a barrier film or film substrate comprising coextruding a core layer and an oxygen barrier layer, and simultaneously stretching the coextruded film in both its machine and transverse directions to more than twenty five times its original areal dimensions to produce a film which exhibits an oxygen transmission rate (OTR) when measured in accordance with ASTM F1927-14 of below 200 cc/m.sup.2/24 hr at a relative humidity (RH) of 85%.

28. The method according to claim 27, wherein the film exhibits an oxygen transmission rate (OTR) when measured in accordance with ASTM F1927-14 of below 600 cc/m.sup.2/24 hr at a relative humidity (RH) of 90%.

Description

EXAMPLES

Test Methods

[0069] Details of the test methods used in these Examples are as follows:

TABLE-US-00001 Test Types Method Optical Properties Testing Gloss ASTM D2457-13 Narrow Angle Haze Internal Innovia Method Wide Angle Haze Based on ASTM D1003-13 Physical Properties Testing Tensile Properties Based on ASTM D882-12 Shrinkage Based on ASTM D2732-08 Barrier Properties Testing Oxygen Barrier at Based on ASTM D3985-05 0% RH (2010)e1 & ASTM D3985-17 Oxygen Barrier at Based on ASTM F1927-14 Elevated RH WVTR Testing/Barrier Based on ASTM F1249-13

Physical Properties

Thickness

[0070] Sample thickness is measured on a calibrated Mercer 1220DM or 122 thickness gauge taking the average over the applicable parts of the sample. Alternatively, sample thickness is measured using a calibrated microscope to image a film section (thin films are cut as produced or can be embedded in a polymeric material cured at 60° C. overnight to ease sectioning of a flexible film, using a Leica semi-motorised microtome fitted with either a diamond knife or disposable blade), image taken using a Zeiss axio M2m imager compound light microscope (using reflected bright field light under the ×20 and ×50 objectives lenses) the image generated allows us to knowledge of both EVOH layer thickness and also overall film thickness.

Shrinkage (Free)

[0071] Based on ASTM D2732. A minimum of 3 samples of film are cut in both direction 1 and direction 2 (equivalent of MD & TD in pilot and production plant produced films) to 10 mm wide strips using a calibrated twin bladed cutter. These samples were then marked at distances over 10 cm and placed in a shrinkage frame. The frame was then subjected to the temperature of shrinkage (in a preheated Swallow Shrinkage Oven with LTE Scientific Temperature Controller) for 60 second before being removed and measured. Percentage shrinkage was calculated from the change in length versus original length and averaged over the number or samples.

Tensile Tests

[0072] Based on ASTM D882. Samples of film substrate are cut to 25 mm wide strips using a calibrated twin blade Guillotine (or twin bladed cutter). These strips are then cut to the required size using a calibrated grid underlay and Stanley knife (with new blade). For Plant/Laboratory scale samples—3 specimens of each sample are cut in both direction 1 & 2 (equivalent of sampling in the MD and TD in plant samples). These samples are then set up and drawn at room temperature on either a Shimadzu AGS-X Std tester or an Instron 4301 tester, draw forces are recorded under conditions outlined in the ASTM method and results recorded.

Optical Properties

Gloss

[0073] Gloss measurements are taken based on ASTM D2457. Gloss results are recorded at 45° using a calibrated unit either using a Novo-gloss Lite unit calibrated to a zero reference and then set on a black back ground of known reflectance or a NovoGloss 45° Rhopoint meter. The unit is regularly tested against both the supplied calibrated block and the background to black sheet. Results are taken over a sample and reported as an average of 3 tests.

Wide Angle Haze (WAH)

[0074] Testing is based on ASTM D1003. WAH of a specimen is the percentage of transmitted light which, in passing through the specimen, deviates from the incident beam by more than 2.5 degrees by forward scattering. WAH results are recorded at using a pre calibrated unit (Hazemeter M57 and Spherical Hazemeter from Diffusion Systems) each variant is tested 3 times across the sample web and an average result recorded.

Narrow Angle Haze (NAH)

[0075] NAH of a specimen is the parallel light which is scattered by more than 6 minutes (0.1°) of an arc when passing through the film or film substrate sample from the incident beam, and is measured as a percentage of total light transmitted through the film. Results are recorded using a pre calibrated “Rayopp” laser haze meter and recorded over the length of a 25 mm wide film strip, recording both the maximum and minimum results achieved over the sample.

Barrier Testing

Oxygen Barrier 0% RH

[0076] Based on ASTM D3985. Testing is carried out with 2 replicates of each sample, these materials are run under standard conditions and results for the given film or film substrate sample recorded as average of these results. For multilayer samples the sample is sectioned and the thickness of the barrier layer and film determined by microscopy otherwise the film thickness is recorded using a calibrated micrometer.

Oxygen Barrier Variable RH

[0077] Based on ASTM F1927. Testing is carried out with 2 replicates of each sample, these materials are run under the set RFI conditions and results for the given film or film substrate sample recorded as average of these results. For multilayer samples the sample is sectioned and the thickness of the barrier layer and film or film substrate determined by microscopy otherwise the film thickness is recorded using a calibrated micrometer.

Processing

Drying of Samples

[0078] Drying of samples before processing on extruders is carried out using either a fluidised bed dryer from Christison or a Dri Air Drier model ARTD-X100 using conditions recommended by the relevant supplier when required.

Stretching

[0079] Samples are stretched on a Karo IV stretcher under conditions shown in the experimental section in all cases the oven is allowed between 30 minutes and 1 hour to equilibrate at the desired temperature and samples are stretched at 181% rate unless otherwise noted.

Comparative (Sequentially Drawn) Example

[0080] A multilayer barrier sequentially drawn BOPP film substrate comprising an oxygen barrier layer produced by Taghleef Industries SPA (film marketed as Extendo XTMU) was sourced from the market place and analysed, the results being reported below. It is believed that this film was manufactured broadly in accordance with the disclosure of EP2113378.

Simultaneously Oriented Film Sample Production

[0081] Details of the individual components of the film substrates referenced below are listed in Table 1:

TABLE-US-00002 TABLE 1 Materials Used Range Code Producer Polymer Type Moplen HP4220 LyondellBasell PP homopolymer DuPure M10050 Ducor PP homopolymer Admer 1179 Mitsui Maleic Anhdrydide PP + elastomers EVAL SP521 Kuraray EVOH 27% Ethylene Content EVAL SP482 Kuraray EVOH 32% Ethylene Content G-SoarnoL GC3304 Nippon Gohsei EVOH 33% Ethylene Content EVAL SP292 Kuraray EVOH 44% Ethylene Content

Lab Scale Samples

[0082] Cast sheet samples were produced using a Dr Collins 5-layer cast film line. The multilayer extrusion system was configured to give a sheet layer structure ABCBA. Where the A layer is polypropylene, B layer is a tie layer and the C layer is EVOH.

[0083] Extrusion was carried out with the die at 235° C. and extruders increasing in temperature from the first zone at 190° C. to 230° C. The extrudate was cast onto chilled rollers at 30-36° C. and an approximately 1 mm thick cast sheet produced.

[0084] The cast sheet samples were then cut into square plaques, which were then simultaneously drawn biaxially to a produced a thin film substrate using a Bruckner Karo IV film stretching machine using the conditions shown in the Table 2.

TABLE-US-00003 TABLE 2 Experimental Conditions for Laboratory Scale Work Average OXYGEN Draw Final BARRIER Conditions/Ratio Film OXYGEN Layer Draw Preheat Substrate BARRIER Thickness Draw Temp Time Thickness Sample Type (microns) Ratio ° C. (sec) (microns) Comparative * 1.8 * * N/A 30 Lab 1 SP482 2.5 7 × 7 156 30 15.5 Lab 2 SP521 2.8 7 × 7 156 30 18.5 Lab 3 GC3304 4.0 7 × 7 156 60 25 *not specified

Pilot Scale Samples

[0085] A pilot trial was carried out on a pilot double bubble biaxial orientation line. Comprising coextrusion and quenching, followed by reheating and orientation of the generated cast tube. Simultaneous orientation of the tube occurs under the action of internal air 5 pressure (TD) and differential nips (MD).

[0086] Extrusion was carried out between 210-230° C., with the die set to 220° C. and the die lip at 210° C. The cast tube was then chilled simultaneously internally and externally to control the level of crystallinity. The cast tube was then fed to the top of the orientation tower, 0 reheated and blown under the conditions itemized in Table 3 below:

TABLE-US-00004 TABLE 3 Experimental Conditions for Pilot Trials Average OXYGEN Final BARRIER Draw Conditions/ Film OXYGEN Layer Ratio Substrate BARRIER Thickness Draw Draw Thickness Sample Type (microns) Ratio Temp ° C. (microns) Comparative * 1.8 * * 30 Pilot 1 SP482 2.0 6.5 × 6.5 148 16.7 Pilot 2 GC3304 1.4 6.5 × 6.5 148 18.4 Pilot 3 GC3304 1.2 6.5 × 6.5 148 18.9 *See Sequentially Drawn Sample Introduction for Information

[0087] The theoretical structure of the resulting film substrates (lab and pilot scale Examples) was as follows in Table 4:

TABLE-US-00005 TABLE 4 Film Structures Outer Core Layer (A) Tie Layer (B) Barrier Layer (C) Tie Layer (B) Outer Core Layer (A) Wt. Wt. Wt. Wt. wt. % Sample Material % Material % Material % Material % Material Structure  Lab 1 HP420M 36 Admer 1179 8 SP482 11 Admer 1179 8 HP420M 36  Lab 2 HP420M 36 Admer 1179 8 SP521 11 Admer 1179 8 HP420M 36  Lab 3 HP420M 38 Admer 1179 6 GC3304 11 Admer 1179 6 HP420M 38 Pilot 1 HP420M 38 Admer 1179 6 SP482 12 Admer 1179 6 HP420M 38 Pilot 2 HP420M 39 Admer 1179 6 GC3304 10 Admer 1179 6 HP420M 39 Pilot 3 HP420M 38 Admer 1179 6 GC3304 12 Admer 1179 6 HP420M 38 * Wt. % refers to the percent by weight of the Material relative to the whole film substrate structure.

[0088] All film substrates of the examples were subjected to optical testing under standard conditions, with the results being presented in Table 5 below:

TABLE-US-00006 TABLE 5 Optical Properties OXYGEN Final BARRIER Film OXYGEN Layer Substrate BARRIER Thickness Thickness Gloss WAH NAH Sample Type (microns) (microns) 45° % mmn max Compar- * 1.8 30 90.5 3 1.3 2.3 ative.  Lab 1 SP482 2.5 15.5 71.7 4.3 34.4 42.0  Lab 2 SP521 2.8 18.5 91.6 2.1 14.1 29.1  Lab 3 GC3304 4.0 25 97.9 1.1 7.8 12.7 Pilot 1 SP482 2.0 16.7 88.5 0.5 1.2 7.5 Pilot 2 GC3304 1.4 18.4 89.9 1 0.4 3.2 Pilot 3 GC3304 1.2 18.9 79.9 0.6 0.2 1.4 * not specified

[0089] All film substrate samples were subjected to oxygen barrier testing at varying levels of % RH with the results presented in Table 6 below:

TABLE-US-00007 TABLE 6 Barrier Results—ASTM Test Method D3985-17 & F1927-14 OXYGEN Oxygen Transmission Rate Film Substrate BARRIER (cm.sup.3/m.sup.2/24 hr) at % RH Thickness Sample Thickness (μm) 0 50 70 85 90 (μm) Comparative 1.8 2.5 2.3 13 260 760 30 Lab Samples Lab 1 2.5 14 7.6 14.5 29 — 15 Lab 2 2.8 2.5 1.5 2.2 5.9 — 20 Lab 3 4.0 — 1 — 11 — 25 Pilot-Plant Samples Pilot 1 2.0 8.6 4.9 9.4 27 31 23.4 Pilot 2 1.4 6.1 2.5 5.5 27 49 19.7 Pilot 3 1.2 3.2 4.7 9.5 24 44 15.3

[0090] It will be seen that the film substrates of the invention exhibit substantially improved oxygen barrier performance with respect to the prior art sequentially stretched film substrate at higher levels of % RH.

The Effect of Draw Ratio

[0091] The effect of draw ratio on barrier properties as explored.

[0092] Cast sheet samples were produced using a Dr Collins 5-layer cast film line. The multilayer extrusion system was configured to give a sheet layer structure ABCBA. Where the A layer is polypropylene, B layer is a tie layer and the C layer is EVOH.

[0093] Extrusion was carried out with the die at 235° C. and extruders increasing in temperature from the first zone at 190° C. to 230° C. The extrudate was cast onto chilled rollers at 30-36° C. and an approximately 1 mm thick cast sheet produced.

[0094] The cast sheet samples were then cut into square plaques, which were then simultaneously drawn biaxially at different draw ratios with a preheat time of 50 seconds and a draw temperature of 156° C.) to produce a thin film substrates using a Bruckner Karo IV film stretching machine.

[0095] The barrier properties of these film substrates are summarised in Table 7.

TABLE-US-00008 TABLE 7 Lab Scale—Barrier Results Standardised to a 2.0 micron EVOH Barrier layer—ASTM Test Method D3985-17 & F1927-14 Oxygen Transmission Barrier with Thickness Sample Rate (cm.sup.3/m.sup.2/24 hr) Correction average 2 micron Description & 50% 85% 90% EVOH 50% 85% 90% Draw Ratio RH RH RH EVOH Thickness RH RH RH Lab 4 4 × 4 0.8 6 12 SP482 10.0 4.00 30.00 60.00 Lab 4 5 × 5 1.3 10 17 8.0 5.22 40.18 68.31 Lab 4 6 × 6 2 12 28 5.0 5.00 30.00 70.00 Lab 4 7 × 7 2.9 12 26 4.1 5.95 24.60 53.30 Lab 5 4 × 4 0.2 1.9 4.1 SP521 8.0 0.80 7.60 16.40 Lab 5 5 × 5 0.2 2.1 4.6 7.0 0.70 7.35 16.10 Lab 5 6 × 6 0.4 2.6 6.6 8.0 1.60 10.40 26.40 Lab 5 7 × 7 0.5 4.1 7.5 3.9 0.98 8.00 14.63 Lab 6 4 × 4 3.9 14 21 SP292 10.0 19.50 70.00 105.00 Lab 6 5 × 5 5.9 22 35 6.0 17.70 66.00 105.00 Lab 6 6 × 6 7.7 27 40 5.0 19.25 67.50 100.00 Lab 6 7 × 7 11 38 64 3.2 17.60 60.80 102.40 Lab 7 4 × 4 0.3 2.2 5.3 GC3304 10.0 1.50 11.00 26.50 Lab 7 5 × 5 0.4 5.4 11 8.0 1.60 21.60 44.00 Lab 7 6 × 6 0.6 6.2 15 6.0 1.80 18.60 45.00 Lab 7 7 × 7 0.9 8.7 23 3.6 1.62 15.66 41.40

[0096] It will be seen that when corrected for thickness of EVOH layer, the barrier properties of the inventive film substrates are improved at one or both of 85% and 90% RH when the areal draw is increased beyond 25 or beyond 36. This is counterintuitive since often the barrier properties reduce as between areal draws of 16 and 25 suggesting that barrier properties will continue to reduce as draw ratios become higher. This turns out not to be the case. We speculate that this may be a function of two different mechanisms for inducing crystallinity in the oxygen barrier layer. A level of crystallinity may be present in the barrier layer initially which is broken down at first as the film substrate is drawn. However, as the drawing increases in intensity (i.e. increased areal draw ratio), further strain-induced crystallinity may become apparent in the oxygen barrier layer.

[0097] The same samples were assessed for WVTR, with the results presented in Table 8.

TABLE-US-00009 TABLE 8 Lab Scale—WVTR Barrier Results—ASTM Test Method ASTM F1249-13 OTR @ 50% Thickness microns Sample EVOH Orientation RH EVOH Film WVTR Description Type Temp (cm.sup.3/m.sup.2/24 hrs) Layer Layer (g/m.sup.2/24 hrs) Lab 4 7 × 7 SP482 156 2.9 4.1 23 5.6 Lab 5 7 × 7 SP521 156 0.5 3.9 19 5.7 Lab 6 7 × 7 SP292 156 11 3.2 21 6.3 Lab 7 7 × 7 GC3304 156 0.9 3.6 22 5.2

[0098] The effect of draw ratio was further investigated in production scale studies on a double bubble biaxial orientation line. Extrusion was carried out with all extruders except the EVOH layer between 210-265° C., with the die set to 245° C. and the EVOH extruder at 190-230° C. The cast tube was then chilled simultaneously internally and externally to control the level of crystallinity. The cast tube was then reheated and blown under standard BOPP orientation conditions (150-160° C.). In each case the EVOH used was SP482. The draw ratio for each sample was 8.0×8.05 and the results are presented in Table 9. The overall film structure is the form ABCDCBA. Where the A layer is a thin heat seat layer, B is a polypropylene (approx. 75% of Total Structure), C layer is a tie layer (approx. 14% of Total Structure) and the D layer is EVOH (approx. 10% Total Structure).

TABLE-US-00010 TABLE 9 Production Scale (Plant)—Barrier Results Standardised to a 2.0 micron EVOH Barrier layer- ASTM Test Method D3985-17 & F1927-14 Oxygen Transmission Rate @ 23° C. (cm.sup.3/m.sup.2/24 hr) Barrier with OTR Thickness Ave. Thickness @ Correction in Microns from EVOH average Microscopy Thickness 2 microns Sections 50% 85% 50% 85% EVOH Film RH RH RH RH Sample Layer Substrate Ave. Ave. Ave. Ave. Plant 1 2.9 26.8 3.9 17 5.66 24.65 Plant 2 2.9 27.3 4.3 17 6.24 24.65 Plant 3 2.8 27.3 4.6 18 6.44 25.20 Plant 4 2.6 24.3 4.9 21 6.37 27.30

[0099] It will be apparent that the OTR performance of the film substrate of the invention is maintained at production (Plant) scale in comparison with our findings at lab scale, despite the areal draw ratio being even higher (8×8.05 compared with a maximum of 7×7 at lab scale).

[0100] The effect of draw ratio was further investigated in production scale studies on a double bubble biaxial orientation line. Extrusion was carried out with all extruders except the EVOH layer between 210-265° C., with the die set to 245° C. and the EVOH extruder at 190-230° C. The cast tube was then chilled simultaneously internally and externally to control the level of crystallinity. The cast tube was then reheated and blown under standard BOPP orientation conditions (150-160° C.). In each case the EVOH used was SP482. The draw ratio for each sample was 8.0×8.0 and the results are presented in Tables 10 & 11. The overall film structure is the form ABCDCBA. Where the A layer is a thin heat seat layer, B is a polypropylene (approx. 75% of Total Structure), C layer is a tie layer (approx. 14% of Total Structure) and the D layer is EVOH (approx. 10% Total Structure).

TABLE-US-00011 TABLE 10 Production Scale—Optics, Barrier Results EVOH Barrier layer—ASTM Test Method D3985-17 & F1927-14 & Shrinkage results ASTM D2732-08 Optics EVOH OTR 45° 45° Thickness Barrier @ 50% Shrinkage Gloss, Gloss, NAH Microscope RH, 23° C. 130° C. Sample NDT DT WAH Low High Clarity Sections (cm.sup.3/m.sup.2/24 hr) MD TD Plant 5 93.2 94.3 1.5 9.2 11.1 94.1 2.5 6.0 6.33 −0.25 Plant 6 93.8 94.0 1.5 8.3 10.2 93.7 2.6 4.8 6.88 −0.25 Plant 7 93.4 92.4 1.6 9.1 10.7 93.6 3.1 3.4 7.01  0.33 Plant 8 93.5 94.0 1.5 11.1 13.2 92.4 3.5 3.3 6.59  0.75

TABLE-US-00012 TABLE 11 Production Scale—Tensile Results—ASTM Test Method D882-12 1% Elong Load Youngs Secant Ten @ Max @ Modulus Modulus Str brk Load brk Thickness Sample (Mpa) (Mpa) (Mpa) (%) (N) (N) (μm) Tensiles, MD Plant 5 2707 2701 227.4 63.69 158.4 158.4 27.9 Plant 6 2965 2940 226.7 60.43 157.3 157.3 27.8 Plant 7 2876 2937 225.4 56.46 153.5 152.3 27.2 Plant 8 2988 3045 228.0 50.51 148.4 144.8 26.0 Tensiles, TD Plant 5 2505 2378 172.5 104.89 119.8 119.8 27.8 Plant 6 2405 2254 153.7 90.75 106.4 106.4 27.7 Plant 7 2448 2308 165.4 93.17 111.8 111.8 27.0 Plant 8 2533 2363 161.8 88.20 105.9 105.9 26.2

[0101] The effect of draw ratio was further investigated in production scale studies on a double 10 bubble biaxial orientation line. Extrusion was carried out with all extruders except the EVOH layer between 210-265° C., with the die set to 245° C. and the EVOH extruder at 190-230° C. The cast tube was then chilled simultaneously internally and externally to control the level of crystallinity. The cast tube was then reheated and blown under standard BOPP orientation conditions (150-160° C.). In each case the EVOH used was 15 SP521. The draw ratio for each sample was 7.7×8.0 and the results are presented in Tables 12 & 13. The overall film structure is the form ABCDCBA. Where the A layer is a thin heat seat layer, B is a polypropylene (approx. 75% of Total Structure), C layer is a tie layer (approx. 14% of Total Structure) and the D layer is EVOH (approx. 10% Total Structure).

TABLE-US-00013 TABLE 12 Production Scale—Optics, Barrier Results EVOH Barrier layer—ASTM Test Method D3985-17 & F1927-14 & Shrinkage results ASTM D2732-08 EVOH OTR Barrier Film Thickness @ 50% Optics Shrinkage Thickness Microscope RH, 23° C. 45° C. NAH 130° C. Sample (μm) Sections (cm.sup.3/m.sup.2/24 hr) Gloss WAH Low High Clarity MD TD Plant 9 28 2.3 0.8 95.6 1.73 9.0 14.1 91.4 6.84 2.74 Plant 10 29 2.4 0.8 95.9 1.63 9.5 13.0 91.4 6.55 2.55 Plant 11 28 2.6 0.6 95.6 1.80 9.6 14.7 91.0 6.12 3.14

TABLE-US-00014 TABLE 13 Production Scale—Tensile Results—ASTM Test Method D882-12 Elong Load Youngs Secant 1% @ Max @ Modulus Modulus Ten Str brk Load brk Thickness Sample (Mpa) (Mpa) (Mpa) (%) (N) (N) (μm) Tensiles, MD Plant 9 3116 3028 214 79 135 135 25 Plant 10 2976 2923 212 84 134 134 25 Plant 11 3062 3014 211 76 131 131 25 Tensiles, TD Plant 9 2757 2609 190 96 121 121 25 Plant 10 2726 2591 186 94 119 119 26 Plant 11 2870 2707 190 94 117 117 25