MULTI-METAL LAYER WVTR BARRIER PRODUCTS ON WATER VAPOUR AND OXYGEN PERMEABLE BIO-BASED SUBSTRATES

Abstract

The invention relates to a metallized multilayer sheet material for packaging having a water vapour transmission rate of below 5 g/m.sup.2/day at 38° C. RH:90% comprising:

a water vapour permeable sheet substrate, and

at least two metallized layers, each covered directly by a solvent based polymeric coating layer,

wherein the cumulated metallized layers have an optical density of at least 2.5 and/or a thickness of at least 15 nm.

Claims

1. A metallized multilayer sheet material for packaging having a water vapour transmission rate (WVTR) of below 5 g/m.sup.2/day at 38° C. RH:90%, the metallized multilayer sheet material comprising: a water vapour permeable sheet substrate; and at least two metallized layers, each of which is covered directly by a solvent based polymeric coating layer; wherein the cumulated metallized layers have an optical density (OD) of at least 2.5 and/or a thickness of at least 15 nm.

2. The metallized multilayer sheet material of claim 1, wherein the metallized multilayer sheet material has a water vapour transmission rate of below 3 g/m.sup.2/day at 38° C. RH:90%.

3. The metallized multilayer sheet material according to claim 1, further comprising a polymeric coating between the water vapour permeable sheet substrate and a metallized layer.

4. The metallized multilayer sheet material according to claim 1, wherein metallized layers are on the same side of the water permeable sheet substrate.

5. The metallized multilayer sheet material according to claim 1, wherein metallized layers are on both sides of the water permeable sheet substrate.

6. The metallized multilayer sheet material according to claim 1, wherein the at least two metallized layers include more than two metallized layers.

7. The metallized multilayer sheet material according to claim 1, further comprising a further aqueous based polymer coating layer applied onto the water vapour permeable substrate or between the at least two metallized layers.

8. The metallized multilayer sheet material according to claim 1, wherein the water vapour permeable sheet substrate is biodegradable and/or from a renewable source.

9. The metallized multilayer sheet material according to claim 1, wherein the water vapour permeable substrate has a water vapour barrier of over 100 g/m.sup.2 per day at 38° C. and 90% RH.

10. The metallized multilayer sheet material according to claim 1, wherein the cumulated metallized layers have an optical density between 2.5 and 3.7, and/or a thickness between 15 nm and 100 nm.

11. The metallized multilayer sheet material according to claim 1, wherein the water vapour permeable substrate is a fibrous substrate.

12. A process for preparing a metallized multilayer sheet material for packaging, having a water vapour transmission rate (WVTR) of below 5 g/m.sup.2/day at 38° C. RH:90%, the process comprising: applying onto a water vapour permeable sheet substrate, at least two metallized layers; applying a solvent based polymeric coating directly onto each of the at least two metallized layers; and drying the polymeric coating; wherein the cumulated metallized layers have an optical density of at least 2.5 and/or a thickness of at least 15 nm.

13. The process according to claim 12, further comprising: applying a solvent based polymeric coating onto one or both sides of the water vapour permeable sheet substrate, prior to applying a metallized layer, when the substrate does not already comprise a polymeric coating.

14. The process according to claim 12, further comprising applying, between two metallized layers, a layer of water-based polymeric coating.

15. The process for preparing the metallized multilayer sheet material for packaging of claim 1, comprising: laminating onto each other at least two coated water vapour permeable sheet substrates.

16. (canceled)

17. The metallized multilayer sheet material of claim 1, wherein the metallized multilayer sheet material has a water vapour transmission rate of below 2 g/m.sup.2/day at 38° C. RH:90%.

18. The metallized multilayer sheet material of claim 1, wherein the metallized multilayer sheet material has a water vapour transmission rate of below 1 g/m.sup.2/day at 38° C. RH:90%.

19. The metallized multilayer sheet material according to claim 10, wherein the thickness is between 20 nm and 50 nm.

20. The metallized multilayer sheet material according to claim 10, wherein the optical density is between 3 and 4.

Description

[0038] The invention will be better understood with the following description of several examples, referring to the accompanying drawing on which:

[0039] FIG. 1 illustrates a sheet material according to the invention where the metallized multilayer and other layers are on one side of the substrate

[0040] FIG. 2 illustrates a sheet material according to the invention where the metallized multilayers and related layers are on both sides of the substrate,

[0041] FIG. 3 illustrates another sheet material according to the invention,

[0042] FIG. 4 illustrates further sheet material according to the invention and

[0043] FIG. 5 illustrate an arrangement of two laminated sheet materials according to the invention.

[0044] The metal layer used in the examples below is aluminium, the thickness of the metal layers has been correlated to the Optical Density, as well known to a person skill in the art (see for example McClure, D. J.; Copeland, N. Evaporated Aluminium on Polyester: Optical, Electrical, and Barrier Properties as a Function of Thickness and Time (Part II). Available online: httplidnn.convertingquarterly.com/Portals/1/files/matteucci-awards/2010-Evapourated-Aluminum-on-Polyester-p2.pdf)

[0045] The relationship between OD and thickness is not linear but is well established for a number of materials.

[0046] While OD can easily be measured for aluminium layers, as disclosed in the examples below, a person skilled in the art knows that other deposited layers, like for example metal oxides, for which their deposition thickness cannot be reliably quantified by OD measurement, other physical methods can be effectively applied to measure the thickness.

[0047] Units in g/m.sup.2/day is equivalent to g H.sub.2O/m.sup.2/day.

COMPARATIVE EXAMPLE 1-C1S

[0048] A multilayer metallized sheet material, according to the prior art, is prepared as follows: [0049] A first layer of acrylic polymer dissolved into ethyl acetate was applied on the clay coated side of UPM LabelCoat™ 60 gsm C1S base paper, resulting in 1.8 gsm (1.5 μm) acrylic polymer on the paper after ethyl acetate solvent was evaporated by oven drying from the substrate. [0050] An aluminium layer such that the final product after metallization will have an OD 3.5-4.0 was deposited on the dry acrylic polymer layer, by chemical vapour deposition. [0051] A second layer of the acrylic polymer coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the structure was around 1 gsm (0.8-1.2 μm thickness) after the solvent was evaporated from the substrate by oven drying.

[0052] This material represents the prior art, where only one thick metal layer is present in the sheet material, with an OD>2.5.

[0053] The material was characterized by WVTR values between 5.22 and 12.36 g-/m.sup.2/day, showing a variability (Δ)=7.14 g/m.sup.2/day with an average=8.56 g H.sub.2O/m.sup.2/day measured at 38° C. and relative humidity 90% on six selected samples.

COMPARATIVE EXAMPLE 1A—C1S

[0054] A single metallized layer sheet material, according to the prior art, is prepared as follows: [0055] A first layer of polyester polymer coating dissolved into ethyl acetate was applied on the clay coated side of Pixelle Pointflex by 60 gsm C1S base paper, resulting in 1.1-1.3 gsm polyester polymer on the paper after ethyl acetate solvent was evaporated by oven drying from the substrate (FIG. 1, layer #3). [0056] An aluminium layer such that the final product after metallization will have an OD 2.7-3.7 was deposited on the dry polyester polymer layer, by chemical vapour deposition (FIG. 1, layer #4). [0057] A second layer of the polyester polymer coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried polyester polymer on the structure was around 1.0-1.1 gsm after the solvent was evaporated from the substrate by oven drying (FIG. 1, layer #5).

[0058] This material represents the prior art, where only one thick metal layer is present in the sheet material, with an OD>2.5.

[0059] The material was characterized by WVTR values between 2.15 and 6.72 g/m.sup.2/day, showing a variability Δ=4.58 g H.sub.2O/m.sup.2/day with an average=4.81 g/m.sup.2/day measured at 38° C. and relative humidity 90% on six selected samples.

EXAMPLE 1 C1S

[0060] A multilayer metallized sheet material, as illustrated on FIG. 1, according to the present invention, was prepared as follows: [0061] A first layer of polyester polymer dissolved into ethyl acetate was applied on the coated side of UPM LabelCoat™ 60 gsm C1S base paper (FIG. 1, layer #2), resulting in 0.8 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 1, layer #3). [0062] An aluminium layer such that the final product after metallization will have an OD of approximately 2.5 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 1, layer #4). [0063] A second layer of the polyester polymer coating was applied on the aluminium layer 4, to protect the aluminium layer from abrasion damage, where the amount of oven dried polyester polymer on the structure was around 0.8 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 1, layer #5). [0064] A second aluminium layer was deposited on the dry polyester polymer layer 5 by vacuum deposition (FIG. 1, layer #6) under the same process and conditions as the first aluminium layer (though OD of this specific layer was not measured, it is expected to be similar to the first layer). [0065] A third layer of polyester polymer coating was applied on the aluminium layer 6, to protect the aluminium layer from abrasion damage, where the amount of dried polyester polymer on the metal was around 0.8 gsm after ethyl acetate was evaporated from the structure by oven drying (FIG. 1, layer #7).

[0066] The total thickness of aluminium layers 4 and 6 amounts to an OD of 3.5-4.0. The material has WVTR values between 0.33 and 1.76 g/m.sup.2/day, showing a Δ=1.43 g/m.sup.2/day with an average=0.80 g/m.sup.2/day measured at 38° C. and relative humidity 90%, exhibiting superior average WVTR with significantly reduced variability among six randomly chosen test samples.

EXAMPLE 1A C1S

[0067] A multilayer metallized sheet material, as illustrated on FIG. 1, according to the present invention, was prepared as follows: [0068] A first layer of polyester polymer dissolved into ethyl acetate was applied on the coated side of SAPPI Carlid 45 gsm C1S base paper (FIG. 1, layer #2), resulting in 0.8-1.2 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 1, layer #3). [0069] An aluminium layer having an OD of approximately 2.6 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 1, layer #4). [0070] A second layer of the polyester polymer coating was applied on the aluminium layer 4, to protect the aluminium layer from abrasion damage, where the amount of oven dried polyester polymer on the structure was around 0.9 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 1, layer #5). [0071] A second aluminium layer was deposited on the dry polyester polymer layer 5 by vacuum deposition (FIG. 1, layer #6) under the same process and conditions as the first aluminium layer (though OD of this specific layer was not measured, it is expected to be similar to the first layer). [0072] A third layer of polyester polymer coating was applied on the aluminium layer 6, to protect the aluminium layer from abrasion damage, where the amount of dried polyester polymer on the metal was around 0.8 gsm after ethyl acetate was evaporated from the structure by oven drying (FIG. 1, layer #7).

[0073] The total thickness of aluminium (FIG. 1, layers #4 and #6) amounts to an OD of 3.0-3.5. The material has WVTR values between 0.97 and 1.21 g/m.sup.2/day, showing a variability Δ=0.24 g/m.sup.2/day with an average=1.08 g/m.sup.2/day measured at 38° C. and relative humidity 90%, exhibiting superior average WVTR with significantly reduced variability among six randomly chosen test samples.

EXAMPLE 2 C1S

[0074] A multilayer metallized sheet material, comprising a sequence of layers as illustrated on FIG. 1, according to the present invention, was prepared as follows: [0075] A first layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the coated side of Aralar Aravac HWS 65 gsm C1S base paper 2 (FIG. 1, layer #2), leaving 1.6-1.8 gsm dried acrylic polymer on the paper C1S surface after water evaporation from the coating by oven drying (FIG. 1, layer #3). [0076] An aluminium layer 4 having an OD of approximately 2.0-2.5 was deposited on the dry acrylic polymer layer by vacuum deposition (FIG. 1, layer #4). [0077] A second layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer 4, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating (FIG. 1, layer #5). [0078] A second aluminium layer was deposited on the dry acrylic polymer layer by vacuum deposition (FIG. 1, layer #6) under the same process and conditions as the first aluminium layer. [0079] A third layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer 6, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating (FIG. 1, layer #7).

[0080] The total thickness of aluminium layers 4 and 6 amounts to an OD of 3.8-4.1. The material has WVTR values for the six random test samples was between 2.18 and 4.18 g/m.sup.2/day, showing a Δ=2.00 g/m.sup.2/day with an average=2.83 g/m.sup.2/day measured at 38° C. and relative humidity 90%.

COMPARATIVE EXAMPLES 3A— AND EXAMPLES 3B AND 3C—C2S

[0081] A single metallized sheet material (Comparative example 3A), is compared to multilayer metallized on one side of the sheet, comprising a sequence of layers as illustrated on FIG. 1 (example 3B) and to a multilayer metallized material where metal layers are deposited on each side of the substrate, comprising a sequence of layers as illustrated in FIG. 2 (example 3C), was prepared as follows:

COMPARATIVE EXAMPLE 3A— SINGLE METALLIZATION WITH OD=3.8-4.2

[0082] A first layer of polyester polymer dissolved into ethyl acetate was applied on one side of ND Orion 98 gsm C2S base paper, resulting in 1.4 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 3, layer #23). [0083] An aluminium layer having an OD of approximately 4.0 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 3, layer #24). [0084] A second layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer, under the same process and conditions as the first aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 2.0 gsm after the water was evaporated by oven drying from the coating (FIG. 3, layer #25).

[0085] This material represents the prior art, where only one thick metal layer is present in the sheet material. The material was characterized by WVTR values between 1.75 and >110 g (one sample over-ranged Permatran-W Model 3/61)/m.sup.2/day, showing a Δ>108 g/m.sup.2/day with an average>20 g/m.sup.2/day measured at 38° C. and relative humidity 90% on six random test samples.

EXAMPLE 3B

[0086] Double metallization on one side with OD=4.9-5.4, sequence of layers as on FIG. 1, was prepared as follows: [0087] A first layer of polyester polymer dissolved into ethyl acetate was applied on one side of ND Orion 98 gsm C2S base paper (FIG. 1, layer #2), resulting in 1.4 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 1, layer #3). [0088] An aluminium layer having an OD of approximately 3.5 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 1, layer #4). [0089] A second layer of the polyester polymer coating was applied on the aluminium layer 4, where the amount of oven dried polyester polymer on the structure was around 1.4 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 1, layer #5). [0090] A second aluminium layer, having an OD of approximately 2.5, was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 1, layer #6) under the same process and conditions as the first aluminium layer. [0091] A third layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating (FIG. 1, layer #7).

[0092] The material was characterized by WVTR values between 0.12 and 0.26 g/m.sup.2/day, showing a Δ=0.14 g/m.sup.2/day with an average 0.20 g/m.sup.2/day measured at 38° C. and relative humidity 90% with five random test samples.

EXAMPLE 3C

[0093] Single metallization's on both sides with OD=6.3-6.8, sequence of layers as illustrated on FIG. 2, was prepared as follows: [0094] A first layer of polyester polymer dissolved into ethyl acetate was applied on one side of ND Orion 98 gsm C2S base paper (FIG. 2, layer #22), resulting in 1.4 gsm dried amorphous polyester polymer was on the paper after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 2, layer #23). [0095] A second layer of polyester polymer dissolved into ethyl acetate was applied on other side of the first side coated ND Orion 98 gsm C2S base paper, resulting in 1.4 gsm dried amorphous polyester polymer was on the paper after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 2, layer #26). [0096] A first aluminium layer having an OD of approximately 3.0 was deposited on the first side of dry polyester polymer layer by vacuum deposition (FIG. 2, layer #24). [0097] A third layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating (FIG. 2, layer #25). [0098] A second aluminium layer having an OD of approximately 3.0 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 2, layer #27) under the same process and conditions as the first aluminium layer. [0099] A fourth layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer 27 and oven dried, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating (FIG. 2, layer #28).

[0100] The material was characterized by WVTR values between 0.77 to 1.41 g/m.sup.2/day, showing a Δ=0.64 g/m.sup.2/day with an average 1.13 g/m.sup.2/day measured at 38° C. and relative humidity 90% with six random test samples.

COMPARATIVE EXAMPLE EXAMPLES 4A-4B AND EXAMPLES 4C—4E

[0101] Futamura NatureFlex™ Renewable and Compostable Cellulosic double-sided heat sealable coated NVS with WVTR=600 g H.sub.2O/m.sup.2/day at 38° C., 90% RH and OTR=5 cc O.sub.2/m.sup.2/day at 23° C., 50% RH packaging films, was prepared as follows:

[0102] Single metallized sheet materials, 30NVS or 23NVS, (comparative examples 4A and 4B) are compared to multilayer metallized on one side of the sheet material 30NVS (examples 4C and 4D) according to the sequence of layers illustrated on FIG. 1 and to a multilayer metallized material where metallized layers are deposited on each side of the 30NVS substrate, according to the sequence of layers illustrated on FIG. 2 (example 4E), according to the present invention.

COMPARATIVE EXAMPLE 4A (COMPARATIVE TO 4C & 4E)

[0103] Single metallization directly on raw base sheets 30NVS (two WVTR test samples) and 23NVS (two WVTR test samples) with OD=2.5-4.0 [0104] An aluminium layer having an OD of approximately 3.5 was deposited on the NatureFlex™ NVS raw stocks by vacuum deposition. [0105] A first layer of a water-based acrylic polymer emulsion at 25% solids coating or a polyester polymer dissolved into ethyl acetate was applied on the aluminium layer to protect the aluminium layer from abrasion damage, where the amount of acrylic polymer or polyester polymer after oven drying on the metal was around 1.0-1.4 gsm

[0106] This material represents the prior art, where only one thick metal layer is present in the sheet material. The materials were characterized by WVTR values between 2.52 to 3.99 g/m.sup.2/day, showing a Δ=1.47 g/m.sup.2/day with an average 3.09 g/m.sup.2/day measured at 38° C. and relative humidity 90% with four test samples.

COMPARATIVE EXAMPLE 4B (COMPARATIVE TO 4D)

[0107] Single metallization on coated sheet OD=4.1-5.4, was prepared as follows: [0108] A first layer of polyester polymer dissolved into ethyl acetate was applied on one side of 30NVS base substrate, resulting in 1.4 gsm dried amorphous polyester polymer was on the film after ethyl acetate solvent was evaporated from the substrate by oven drying. [0109] An aluminium layer having an OD of approximately 4.0 was deposited on the dry polyester polymer layer by vacuum deposition. [0110] A second layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer and oven dried, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating.

[0111] This material represents the prior art, where only one thick metal layer is present in the sheet material. The material was characterized by WVTR values between 2.15 to 3.15 g/m.sup.2/day, showing a Δ=1.00 g/m.sup.2/day with an average 2.91 g/m.sup.2/day measured at 38° C. and relative humidity 90% with two test samples.

EXAMPLE 4C

[0112] Double metallization on one side with first metal deposited directly onto the raw base with final substrate OD=2.7-3.8 [0113] An aluminium layer having an OD of approximately 2.0 was deposited on the NatureFlex™ 30NVS raw stock (FIG. 1, layer #2) by vacuum deposition (FIG. 1, layer #4). [0114] A first layer polyester polymer dissolved into ethyl acetate was applied on the aluminium layer, resulting in 1.4 gsm dried amorphous polyester polymer was on the film after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 1, layer #5). [0115] A second aluminium layer having an OD of approximately 2.0 was deposited on the structure by vacuum deposition (FIG. 1, layer #6) under the same process and conditions as the first aluminium layer. [0116] A second layer polyester polymer dissolved into ethyl acetate was applied on the aluminium layer, resulting in 1.4 gsm dried amorphous polyester polymer was on the structure after ethyl acetate solvent was evaporated from the substrate by oven drying to protect the aluminium layer from abrasion damage (FIG. 1, layer #7).

[0117] The material was characterized by WVTR values between 1.23 to 1.32 g/m.sup.2/day, showing a Δ=0.09 g/m.sup.2/day with an average 1.27 g/m.sup.2/day measured at 38° C. and relative humidity 90% with two test samples.

EXAMPLE 4D

[0118] Double metallization on one side with both metal layers deposited onto polyester polymer coated 30NVS with final structure OD=3.6-5.3 [0119] A first layer of polyester polymer dissolved into ethyl acetate was applied on one side of NatureFlex™ 30NVS raw stock (FIG. 1, layer #2), resulting in 1.4 gsm dried amorphous polyester polymer was on the substrate after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 1, layer #3). [0120] An aluminium layer having an OD of approximately 2.5 was deposited on the dried polyester polymer layer by vacuum deposition (FIG. 1, layer #4). [0121] A second layer polyester polymer dissolved into ethyl acetate was applied on the aluminium layer, resulting in 1.4 gsm dried amorphous polyester polymer was on the film after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 1, layer #5). [0122] A second aluminium layer having an OD of approximately 2.5 was deposited on the structure by vacuum deposition (FIG. 1, layer #6) under the same process and conditions as the first aluminium layer. [0123] A third layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer and oven dried, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating to protect the aluminium layer from abrasion damage (FIG. 1, layer #7).

[0124] The material was characterized by WVTR values between 1.83 to 1.99 g/m.sup.2/day, showing a Δ=0.16 g/m.sup.2/day with an average 1.90 g/m.sup.2/day measured at 38° C. and relative humidity 90% with two test samples.

EXAMPLE 4E

[0125] Single metallization's on both sides of 30NVS raw stock with OD=3.1-4.0 (FIG. 3 [0126] An aluminium layer having an OD of approximately 2.5 was deposited on one side of the NatureFlex™ 30NVS raw stock (FIG. 3, layer #32) by vacuum deposition (FIG. 3, layer #34). [0127] A first layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating (FIG. 3, layer #35). [0128] A second aluminium layer having an OD of approximately 2.5 was deposited on the other side of the 30NVS substrate by vacuum deposition (FIG. 3, layer #37), under the same process and conditions as the first aluminium layer. [0129] A second layer of a water-based acrylic polymer emulsion at 25% solids coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried acrylic polymer on the metal was around 1.0 gsm after the water was evaporated by oven drying from the coating (FIG. 3, layer #38).

[0130] The material was characterized by WVTR values between 3.90 to 4.22 g/m.sup.2/day, showing a Δ=0.32 g/m.sup.2/day with an average 4.06 g/m.sup.2/day measured at 38° C. and relative humidity 90% with two test samples.

EXAMPLE 5

[0131] White Sack Kraft Paper 70 Gsm Non-Machine Finished, sheet material 5, high puncture resistance with final structure OD=3.3-4.4 (FIG. 4), was prepared as follows: [0132] A first layer of acrylic polymer dissolved into ethyl acetate was applied on one side of White Sack Kraft Paper 70 gsm COS base paper (FIG. 4, layer #42), resulting in 2.9 gsm dried acrylic polymer on the paper after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 4, layer #43-1). [0133] A second layer of acrylic polymer dissolved into ethyl acetate was applied on the other side of the White Sack Kraft Paper 70 gsm COS base paper, resulting in 2.9 gsm dried acrylic polymer was on the paper after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 4, layer #48). [0134] A third layer of aqueous acrylic polymer emulsion at 35% solids was applied on the first side of the acrylic polymer and EVA coated White Sack Kraft Paper 70 gsm substrate, where the amount of dried acrylic polymer on the metal was around 4 gsm after the water was evaporated by oven drying from the coating (FIG. 4; layer #43-2). [0135] A fourth layer polyester polymer dissolved into ethyl acetate was applied over the first side of the acrylic polymer, aqueous EVA and aqueous acrylic polymer coated layers resulting in 1.4 gsm dried amorphous polyester polymer was on the substrate after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 4, layer #43-3). [0136] An aluminium layer having an OD of approximately 2.5 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 4, layer #44). [0137] A fifth layer polyester polymer dissolved into ethyl acetate was applied over the first metal layer, resulting in 1.4 gsm dried amorphous polyester polymer was on the substrate after ethyl acetate solvent was evaporated from the substrate by oven drying (FIG. 4, layer #45). [0138] A second aluminium layer having an OD of approximately 2.5 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 4, layer #46) under the same process and conditions as the first aluminium layer. [0139] A sixth layer polyester polymer dissolved into ethyl acetate was applied on the aluminium layer resulting in 1.4 gsm dried amorphous polyester polymer was on the structure after ethyl acetate solvent was evaporated from the substrate by oven drying to protect the aluminium layer from abrasion damage (FIG. 4, layer #47).

[0140] The material was characterized by WVTR values between 1.31 to 3.56 g/m.sup.2/day, showing a Δ=2.25 g/m.sup.2/day with an average 2.21 g/m.sup.2/day measured at 38° C. and relative humidity 90% with six test samples.

COMPARATIVE EXAMPLE 6-C1S—FOLDED

[0141] A multilayer metallized sheet material, according to the prior art, is prepared as follows: [0142] A first layer of polyester polymer coating dissolved into ethyl acetate was applied on the clay coated side of Pixelle Pointflex 60 gsm C1S base paper (FIG. 1, layer #2), resulting in 1.1-1.3 gsm polyester polymer on the paper after ethyl acetate solvent was evaporated by oven drying from the substrate (FIG. 1, layer #3). [0143] An aluminium layer such that the final product after metallization will have an OD 2.7-3.7 was deposited on the dry polyester polymer layer, by chemical vapour deposition (FIG. 1, layer #4). [0144] A second layer of the polyester polymer coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried polyester polymer on the structure was around 0.9-1.1 gsm after the solvent was evaporated from the substrate by oven drying (FIG. 1, layer #5).

[0145] This material represents the prior art, where only one thick metal layer is present in the sheet material, with an OD>2.5.

[0146] The material was characterized by WVTR after folding according to the set method described as follows.

[0147] 180° folding of metallized WVTR barrier papers single sheets and laminated structures was accomplished by the following procedure: [0148] 1) Metallized paper-based structure is lightly folded lining up corners at top edge and finger pushing 10 mm hard crease in the paper on a polished marble tile (300 mm×300 mm). [0149] 2) A polished chromed surface 2 kg roller of dimensions 110 mm length with 157 mm circumference is lined up for roll crease formation on the folded sheet top 10 mm push creased area, then even speed drawn down full length of paper structure at approximately 300 mm per second. [0150] 3) The folded sheet is hand opened and spread to overcome the substrates dead fold with crease down in contact with the polished marble tile and the 2 kg roller is placed on the top 10 mm crease opened edge prior to drawing the roller down the full length of the substrate crease at approximately 300 mm per second. [0151] 4) Samples for WVTR Permatran-W Model 3/61 were cut maximizing the folded crease length in the testing cell.

[0152] Resulting in values between 11.79 and 19.21 g/m.sup.2/day, showing a variability Δ=7.42 g/m.sup.2/day with an average=15.61 g/m.sup.2/day measured at 38° C. and relative humidity 90% on six selected samples.

EXAMPLE 6—C1S-FOLDED

[0153] A multilayer metallized sheet material, according to the prior art, is prepared as follows: [0154] A first layer 3 of polyester polymer coating dissolved into ethyl acetate was applied on the clay coated side of Pixelle Pointflex 60 gsm C1S base paper (FIG. 1, layer #2), resulting in 1.1-1.3 gsm polyester polymer on the paper after ethyl acetate solvent was evaporated by oven drying from the substrate (FIG. 1, layer #3). [0155] An aluminium layer 4 having an OD of approximately 2.7-3.7 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 1, layer #4). [0156] A second layer 5 of the polyester polymer coating was applied on the aluminium layer 4, to protect the aluminium layer from abrasion damage, where the amount of oven dried polyester polymer on the structure was around 0.9-1.1 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 1, layer #5). [0157] A second aluminium layer 6 was deposited on the dry polyester polymer layer 5 by vacuum deposition (FIG. 1, layer #6) under the same process and conditions as the first aluminium layer (though OD of this specific layer was not measured, it is expected to be similar to the first layer). [0158] A third layer 7 of polyester polymer coating was applied on the aluminium layer 6, to protect the aluminium layer from abrasion damage, where the amount of dried polyester polymer on the metal was around 0.9-1.1 gsm after ethyl acetate was evaporated from the structure by oven drying (FIG. 1, layer #7).

[0159] The total thickness of aluminium layers 4 and 6 amounts to an OD of 4.5-5.0.

[0160] The material has WVTR after folding according to the set method described for Comparative example 6 resulted in values between 2.84 and 7.19 g-/m.sup.2/day, showing a variability Δ=4.35 g/m.sup.2/day with an average=4.77 g-/m.sup.2/day measured at 38° C. and relative humidity 90% on six selected samples.

EXAMPLE 7— C1S—LAMINATED—FLAT

[0161] A multilayer metallized sheet material, according to the prior art, is prepared as follows: [0162] A first layer of polyester polymer dissolved into ethyl acetate was applied on the coated side of SAPPI Carlid 45 gsm C1S base paper (FIG. 5, layer #52), resulting in 0.8-1.2 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 5, layer #53). [0163] An aluminium layer having an OD of approximately 2.6 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 5, layer #54). [0164] A second layer 5 of the polyester polymer coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of oven dried polyester polymer on the structure was around 0.9 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 5, layer #55). [0165] A second aluminium layer was deposited on the dry polyester polymer layer 5 by vacuum deposition (FIG. 5, layer #56) under the same process and conditions as the first aluminium layer (though OD of this specific layer was not measured, it is expected to be similar to the first layer). [0166] A third layer of polyester polymer coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried polyester polymer on the metal was around 0.8 gsm after ethyl acetate was evaporated from the structure by oven drying (FIG. 5, layer #57).

[0167] This metallized paper was then laminated onto itself, such that the final structure further has, on top on the third layer, the following layers: [0168] A fourth layer of polyester polymer coating 0.8 gsm (FIG. 5, layer #57a); [0169] A third aluminium layer (FIG. 5, layer #56a); [0170] A fifth layer 5a of the polyester polymer coating (FIG. 5, layer #55a); [0171] A fourth aluminium layer 4a (FIG. 5, layer #54a); [0172] A sixth layer of polyester polymer applied on the coated side of SAPPI Carlid 45 gsm C1S base paper (FIG. 5, layer #52a) which is here the outermost layer.

[0173] The total thickness of aluminium layers 54, 56, 54a and 56a amounts to an OD of 4.0-5.1. The material has WVTR values between 0.99 and 1.47 g-/m.sup.2/day, showing a variability Δ=0.48 g/m.sup.2/day with an average=1.22 g-/m.sup.2/day measured at 38° C. and relative humidity 90%, exhibiting superior average WVTR with significantly reduced variability among nine randomly chosen test samples.

COMPARATIVE EXAMPLE 8— C1S—LAMINATED— FOLDED

[0174] A single metallized layer sheet material, according to the prior art, is prepared as follows: [0175] A first layer of polyester polymer dissolved into ethyl acetate was applied on the coated side of Pixelle Pointflex 60 gsm C1S base paper (FIG. 5, layer #52), resulting in 1.1-1.3 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 5, layer #53). [0176] An aluminium layer having an OD of approximately 3.0 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 5, layer #54). [0177] A second layer of the polyester polymer coating was applied on the aluminium layer 4, to protect the aluminium layer from abrasion damage 1.0 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 5, layer #55).

[0178] This metallized paper has further been laminated to the polyester layer of a coated paper prepared as follows: [0179] a layer of polyester polymer dissolved into ethyl acetate was applied on the coated side of Pixelle Pointflex 60 gsm C1S base paper (FIG. 5, layer #52a), resulting in 1.1-1.3 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 5, layer #53a).

[0180] Note that layers #54a, 55a,56a, 57a, 56 and 57 in FIG. 5 are omitted from the structure of this example.

[0181] The material was characterized by WVTR after folding according to the set method described at Comparative Example 6 resulting in values between 3.22 and 17.36 g/m.sup.2/day, showing a variability Δ=14.64 g/m.sup.2/day with an average=9.29 g/m.sup.2/day measured at 38° C. and relative humidity 90%.

EXAMPLE 8— C1S—LAMINATED— FOLDED

[0182] A single metallized layer sheet material, according to the prior art, is prepared as follows: [0183] A first layer of polyester polymer dissolved into ethyl acetate was applied on the coated side of Pixelle Pointflex 60 gsm C1S base paper (FIG. 5, layer #52), resulting in 1.1-1.3 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 5, layer #53). [0184] An aluminium layer having an OD of approximately 3.0 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 5, layer #54). [0185] A second layer of the polyester polymer coating was applied on the aluminium layer 4, to protect the aluminium layer from abrasion damage 1.0 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 5, layer #55).

[0186] This metallized paper has been laminated to itself, in a symmetrical manner, such that the final structure further comprises the following layers onto layer #55: [0187] A layer of the polyester polymer coating (FIG. 5, layer #55a). [0188] An aluminium layer (FIG. 5, layer #54a). [0189] A layer of polyester polymer applied (FIG. 5, layer #53a) on the coated side of Pixelle Pointflex 60 gsm C1S base paper (FIG. 5, layer #52a).

[0190] Note that layers #56a, 57a, 56 and 57 in FIG. 5 are omitted from the structure of this example.

[0191] The material was characterized by WVTR after folding according to the set method described at Comparative Example 6 resulting in values between 1.48 and 4.88 g/m.sup.2/day, showing a variability Δ=3.40 g/m.sup.2/day with an average=2.59 g/m.sup.2/day measured at 38° C. and relative humidity 90%.

EXAMPLE 8A— C1S—LAMINATED—FOLDED

[0192] A multilayer metallized sheet material, according to the prior art, is prepared as follows: [0193] A first layer of polyester polymer dissolved into ethyl acetate was applied on the coated side of SAPPI Carlid 45 gsm C1S base paper (FIG. 5, layer #52), resulting in 0.8-1.2 gsm dried amorphous polyester polymer on the paper after ethyl acetate solvent was evaporated from the substrate (FIG. 5, layer #53). [0194] An aluminium layer having an OD of approximately 2.6 was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 5, layer #54). [0195] A second layer of the polyester polymer coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of oven dried polyester polymer on the structure was around 0.9 gsm after ethyl acetate was evaporated from the substrate by oven drying (FIG. 5, layer #55). [0196] A second aluminium layer was deposited on the dry polyester polymer layer by vacuum deposition (FIG. 5, layer #56) under the same process and conditions as the first aluminium layer (though OD of this specific layer was not measured, it is expected to be similar to the first layer). [0197] A third layer of polyester polymer coating was applied on the aluminium layer, to protect the aluminium layer from abrasion damage, where the amount of dried polyester polymer on the metal was around 0.8 gsm after ethyl acetate was evaporated from the structure by oven drying (FIG. 5, layer #57).

[0198] This metallized paper has been laminated to itself, in a symmetrical manner such that the final structure has the following layers on top of layer #57: [0199] A fourth layer of polyester polymer coating 0.8 gsm (FIG. 5, layer #57a). [0200] A third aluminium layer (FIG. 5, layer #56a). [0201] A fifth layer of the polyester polymer coating (FIG. 5, layer #55a). [0202] A fourth aluminium layer (FIG. 5, layer #54a). [0203] A sixth layer of polyester polymer applied on the coated side of SAPPI Carlid 45 gsm C1S base paper (FIG. 5, layer #52a)

[0204] The material was characterized by WVTR after folding according to the set method described at Comparative Example 6 resulting in values between 1.79 and 4.00 g/m.sup.2/day, showing a variability Δ=2.21 g/m.sup.2/day with an average=2.44 g/m.sup.2/day measured at 38° C. and relative humidity 90%.

[0205] Examples Summary Tables

TABLE-US-00001 Compara- Compara- Layers in tive tive Example FIG. 1 Example 1 Example 1A Example 1 1A Example 2 7 Polyester Polyester Acrylic polymer polymer polymer solvent solvent water based based based 6 Aluminium Aluminium Alumi- nium 5 Acrylic Polyester Polyester Polyester Acrylic polymer polymer polymer polymer polymer solvent solvent solvent solvent water based based based based based 4 Aluminium Aluminium Aluminium Aluminium Alumi- nium 3 Acrylic Polyester Polyester Polyester Acrylic polymer polymer polymer polymer polymer solvent solvent solvent solvent water based based based based based 2 One side One side One side One side One side coated coated coated coated coated (C1S) (C1S) (C1S) (C1S) (C1S) Final OD 3.5-4.0 2.7-3.0 3.5-4.0 3.0-3.5 3.8-4.1 WVTR  8.56 4.81 0.80 1.08 2.83 (g/m.sup.2/day) average WVTR  7.14 4.58 1.43 0.24 2.00 DELTA WVTR  5.22 2.15 0.33 0.97 2.18 min WVTR 12.36 6.72 1.76 1.21 4.18 max Number Six Six Six Five Six of test selected selected random random random samples

[0206] These examples show that the multilayer metallized sheet materials of the invention enable to improve the WVTR along with reducing the variability over the surface of the material.

TABLE-US-00002 Compar- Layers Example Layers in ative Example 3B in 3C FIG. 1 Example 3A (cf FIG. 1) FIG. 2 (cf FIG. 2) 7 Acrylic polymer water based 6 Aluminium 5 Acrylic Polyester 25 Acrylic polymer polymer polymer water based solvent based water based 4 Aluminium Aluminium 24 Aluminium 3 Polyester Polyester 23 Polyester polymer polymer polymer solvent solvent based solvent based based 2 Two side Two side 22 Two side coated coated (C2S) coated (C2S) (C2S) 26 Polyester polymer solvent based 27 Aluminium 28 Acrylic polymer water based Final OD 3.8-4.2 4.9-5.4 6.3-6.8 WVTR >20 0.20 1.13 (g H2O/m.sup.2 − day) average WVTR DELTA >108 0.14 0.64 WVTR min 1.75 0.12 0.77 WVTR max >110 0.26 1.41 Number of test Six random Six random Six random samples

[0207] These examples show that the multilayer metallized sheet materials of the invention display low WVTR and low variability, both when the two aluminium layers are on the same side of the paper and on each side of the paper.

TABLE-US-00003 Layers in Comparative Comparative Example 4C Example 4D Layers Example 4E Fig 1 Example 4A Example 4B (cf Fig 1) (cf Fig 1) in Fig 3 (cf Fig. 3) 7 Polyester Acrylic polymer polymer solvent based water based 6 Aluminium Aluminium 5 Polyester Acrylic Polyester Polyester 35 Acrylic polymer polymer polymer polymer polymer solvent based water based solvent based solvent based water based 4 Aluminium Aluminium Aluminium Aluminium 34 Aluminium 3 Polyester Polyester polymer polymer solvent based solvent based 2 NatureFlex NatureFlex NatureFlex NatureFlex 32 NatureFlex NVS, 2 side NVS, 2 side NVS, 2 side NVS, 2 side NVS, 2 side heat-sealable heat-sealable heat-sealable heat-sealable heat-sealable 37 Aluminium 38 Acrylic polymer water based Final OD 2.7-4.0 4.1-5.4 2.8-3.2 3.6-5.3 3.1-4.0 WVTR (g 3.09 2.91 1.27 1.90 4.06 H2O/m.sup.2/ day) average WVTR 1.47 1.00 0.09 0.16 0.32 DELTA WVTR min 2.52 2.15 1.23 1.83 3.90 WVTR max 3.99 3.15 1.32 1.99 4.22 Number of Four random Two random Two random Two random Two random test samples

[0208] These examples show that the multilayer metallized sheet materials of the invention enable reduce the variability of WVTR over the surface of the material, whether the aluminium is deposited directly on the substrate or whether an intermediate layer is applied.

TABLE-US-00004 Layers in FIG. 4 Example 5 47 Polyester polymer solvent based 46 Aluminium 45 Polyester polymer solvent based 44 Aluminium 43-3 Polyester polymer solvent based 43-2 Acrylic polymer water based 43-1 Acrylic polymer solvent based 42 White Sack Kraft, Non-MF (C0S) 48 Acrylic polymer solvent based Final OD 3.3-4.4 WVTR (g H2O/m.sup.2/day) average 2.21 WVTR DELTA 2.25 WVTR min 1.31 WVTR max 3.56 Number of test samples Six random

TABLE-US-00005 Comparative Layers in FIG. 1 Example 6 Example 6 2 One side coated One side coated (C1S) (C1S) 3 Polyester polymer Polyester polymer solvent based solvent based 4 Aluminium Aluminium 5 Polyester polymer Polyester polymer solvent based solvent based 6 Aluminium 7 Polyester polymer solvent based Final OD 2.7-3.7 4.5-5.0 WVTR (g H.sub.2O/m.sup.2/day) 15.61 4.77 average WVTR DELTA  7.42 4.35 WVTR min 11.79 2.84 WVTR max 19.21 7.19 Number of test Six Random Six random samples

[0209] These examples show that the multilayer metallized sheet materials of the invention enable to improve the WVTR along with reducing the variability over the surface of the material, even after folding.

TABLE-US-00006 Layers in FIG. 5 Example 7 52a One side coated (C1S) 53a Polyester polymer solvent based 54a Aluminium 55a Polyester polymer solvent based 56a Aluminium 57a Polyester polymer solvent based 57 Polyester polymer solvent based 56 Aluminium 55 Polyester polymer solvent based 54 Aluminium 53 Polyester polymer solvent based 52 One side coated (C1S) Final OD 4.0-5.1 WVTR (g H.sub.2O/m.sup.2/day) average 1.22 WVTR DELTA 0.48 WVTR min 0.99 WVTR max 1.47 Number of test samples Nine random

[0210] This example shows that the multilayer metallized sheet materials of the invention enable to improve the WVTR along with reducing the variability over the surface of the material, after lamination.

TABLE-US-00007 Comparative Layers in FIG. 5 Example 8 Example 8 Example 8A 52a One side One side One side coated (C1S) coated (C1S) coated (C1S) 53a Polyester Polyester Polyester polymer polymer polymer solvent based solvent based solvent based 54a Aluminium Aluminium 55a Polyester Polyester polymer polymer solvent based solvent based 56a Aluminium 57a Polyester polymer solvent based 57 Polyester polymer solvent based 56 Aluminium 55 Polyester Polyester Polyester polymer polymer polymer solvent based solvent based solvent based 54 Aluminium Aluminium Aluminium 53 Polyester Polyester Polyester polymer polymer polymer solvent based solvent based solvent based 52 One side One side One side coated (C1S) coated (C1S) coated (C1S) Final OD 2.7-3.7 3.0-4.0 4.0-5.1 WVTR (g H.sub.2O/m.sup.2/day) 9.29 2.59 2.45 average WVTR DELTA 14.64 3.40 2.21 WVTR min 3.22 1.48 1.79 WVTR max 17.36 4.88 4.00 Number of test samples Eleven random Six Random Eleven random

[0211] These examples show that the multilayer metallized sheet materials of the invention, obtained by lamination of two metallized sheet materials enable to improve the WVTR along with reducing the variability over the surface of the material, even after folding.