Flexible barrier paper

Abstract

The present invention relates to a packaging material comprising: a flexible substrate; and a barrier material over at least a portion of the flexible substrate, the barrier material comprising one or more inflexible barrier layers and one or more flexible barrier layers arranged alternately; wherein the or each inflexible barrier layer comprises an inflexible aluminium oxide or an inflexible silicon oxide; and wherein the or each flexible barrier layer comprises a flexible aluminium oxide or a flexible silicon oxide.

Description

[0001] Flexible Barrier Paper

[0002] The present invention is in the field of packaging materials, particularly flexible packaging materials having barrier properties.

[0003] Background

[0004] A number of metal and metalloid oxides are used to provide barrier properties in packaging applications. These materials are plastic free, inert, and provide excellent barriers to moisture and gas transmission. However, due to their brittle nature, they are easily damaged during post-processing. This problem is particularly acute when these inorganic barriers are used in flexible packaging. As the substrate flexes, defects such as cracks are introduced to the inorganic barrier, allowing moisture and gases to bypass the barrier layer. Certain inorganic barriers can be rendered flexible by altering their stoichiometry, however, this adversely affects their barrier properties.

[0005] It is an object of the present invention to solve one or more of the foregoing problems.

[0006] Summary of the Invention

[0007] A first aspect of the present invention relates to a packaging material comprising: a flexible substrate; and a barrier material over at least a portion of the flexible substrate, the barrier material comprising one or more inflexible barrier layers and one or more flexible barrier layers arranged alternately; wherein the or each inflexible barrier layer comprises an inflexible aluminium oxide or an inflexible silicon oxide; and wherein the or each flexible barrier layer comprises an flexible aluminium oxide or an flexible silicon oxide.

[0008] The flexible substrate may be a polymer film (such as polyethylene, polypropylene, polyester, polyamide, or polyvinyl chloride) or paper.

[0009] The flexible substrate is considered flexible when its elongation at break is more than 7% according to ISO 1924-2.

[0010] It may be that the or each flexible barrier layer comprises flexible aluminium oxide and the or each inflexible barrier layer comprises inflexible aluminium oxide.

[0011] It should be understood that the flexible or the inflexible properties associate to the aluminium oxide is considered depending on the ratio of aluminium and oxygen. More precisely, if the aluminium oxide is richer in oxygen than in aluminium, it is less dense with an amorphous structure and then more flexible and if there is less oxygen, the aluminium oxide may be in a crystalline form, highly ordered and then more inflexible.

[0012] Thus, the flexible aluminium oxide is oxygen rich and the inflexible aluminium oxide is aluminium rich.

[0013] According to the invention, the flexible aluminium oxide has formula AIOx and the inflexible aluminium oxide has formula AlOy, wherein x > y and x > 1.5. In other word, if the ratio Oxygen / Aluminium of the aluminium oxide is less than 1.5, the aluminium oxide is considers inflexible and if the ratio Oxygen / Aluminium is egal or more than 1.5, the aluminium oxide is considers flexible.

[0014] It may be that the or each flexible barrier layer comprises flexible silicon oxide and the or each inflexible barrier layer comprises inflexible silicon oxide.

[0015] It should be understood that the flexible or the inflexible properties associate to the silicon oxide is considered depending on the ratio of silicon and oxygen. More precisely, if the silicon oxide is richer in oxygen than in silicon, it is more ordered and then less flexible and if there is less oxygen and more silicon, the silicon oxide leads to fewer Si-0 bonds, which can result in a more brittle material and then also less flexible. In the case there is the same amount of oxygen and silicon in the silicon oxide, called Stoichiometric Silicon Monoxide, the silicon oxide is more flexible.

[0016] It may be that the flexible silicon oxide is approximately stoichiometric silicon monoxide and the inflexible silicon oxide is more oxygen-rich or more oxygen deficient than the flexible silicon oxide, optionally the flexible silicon oxide has formula SiOw and inflexible silicon oxide has formula SiOz, wherein either z < w < 1 or z > w > 1.

[0017] It understood from the above, that the flexibility or inflexibility of the Aluminium oxide and Silicon oxide depends of their formula, and more precisely of the quantity of their components as described above. It may be that the or each flexible barrier layer comprises flexible silicon oxide and the or each inflexible barrier layer comprises inflexible aluminium oxide.

[0018] It may be that the or each flexible barrier layer comprises flexible aluminium oxide and the or each inflexible barrier layer comprises inflexible silicon oxide. The barrier material may comprise one inflexible barrier layer laminated between a pair of flexible barrier layers.

[0019] The packaging material may further comprise one or more of adhesives, a polymer layer (such as a protective polymer layer), a heat sealing layer, an ink layer, and an overcoat varnish.

[0020] A second aspect of the present invention relates to a container comprising the packaging material of the first aspect of the present invention.

[0021] A third aspect of the present invention relates to the use of the packaging material of the first aspect of the present invention, or the container of the second aspect of the present invention, for the storage of an edible product for human or animal consumption.

[0022] A fourth aspect of the present invention relates to a method of forming a packaging material, the method comprising sequentially applying one or more inflexible barrier layers and one or more flexible barrier layers to at least a portion of a substrate to form a barrier material thereon.

[0023] Applying one or more inflexible barrier layers and one or more flexible barrier layers may comprise atomic layer deposition, preferably spatial atomic layer deposition, such as atmospheric pressure spatial atomic layer deposition.

[0024] The packaging material formed may be the packaging material of the first aspect of the present invention.

[0025] Brief Description of the Drawings

[0026] Fig. 1 shows a prior art embodiment of a packaging material 100 comprising a flexible substrate 110 over which an inflexible barrier material 120 has been deposited. The dotted arrows indicate that moisture and / or gases may only traverse the inflexible barrier material 120 slowly.

[0027] Fig. 2 shows the same prior art embodiment as Fig. 1 post-processing. Processing of the packaging material 100 has induced a defect 200 in the inflexible barrier material 120. The defect 200 allows unrestricted movement of moisture and / or gases through the inflexible barrier material 120, indicated by the solid black line. Fig. 3 shows an exemplary packaging material 300 according to the present invention, having a barrier material 310 comprising an inflexible barrier layer 320 between two flexible barrier layers 330. The dotted arrows indicate that moisture and / or gases may only traverse the barrier material 310 slowly.

[0028] Fig. 4 shows the same exemplary embodiment as in Fig. 3 post-processing. Processing of the packaging material 300 has induced a defect 200 in the inflexible barrier layer 320. However, traversal of moisture and / or gases through the barrier material 310 remains at an acceptable rate due to the presence of the flexible barrier layers 330 across the defect 200.

[0029] Fig. 5 shows a further exemplary packaging material 500 with a barrier material 510 comprising two inflexible barrier layers 320 interleaved with flexible barrier layers 330. Defects 200 have been induced post-processing, however, the defects are off-set, maintaining a high barrier property and slow traversal of moisture and / or gases through the barrier material 510.

[0030] Detailed Description

[0031] The present invention relates to a packaging material having high barrier properties that are maintained at an acceptable level through any post-processing (e.g. bending, stretching, and torsion) that may be used to convert the packaging material to a package containing, or ready to contain, contents that are sensitive to environmental factors (e.g. foodstuffs that are sensitive to oxygen and / or moisture). The packaging material comprises a flexible substrate and a barrier material over at least a portion of the flexible substrate, the barrier material comprising one or more inflexible barrier layers and one or more flexible barrier layers arranged alternately. The barrier material makes use of alternating layers of inflexible and flexible barrier layers to provide an initial high barrier that can be maintained to an acceptable level during post-processing. Inflexible barrier layers have higher barrier properties than flexible barrier layers, but these are compromised by post-processing that introduces defects traversing the entirety of the layer, such as pin-holes or cracks, leading to a lower barrier effect post-processing. Without wishing to be bound by theory, it is thought that alternating the inflexible and flexible barrier layers provides a barrier material in which any induced defect is present only in the inflexible barrier layer, with the uncompromised flexible barrier layer allowing the overall barrier material to provide acceptable barrier properties. The or each inflexible barrier layer comprises an inflexible aluminium oxide or an inflexible silicon oxide; and wherein the or each flexible barrier layer comprises a flexible aluminium oxide or a flexible silicon oxide. It has been found that these inorganic materials are particularly suited to use in this application, with the inflexible materials having a largely crystalline structure, resulting in layers with high barrier properties that are brittle, while the flexible materials have an amorphous character, resulting in layers with lower, but acceptable, barrier properties that are able to flex.

[0032] Substantially any substrate may be provided with the barrier material. The barrier material is particularly beneficial for flexible substrates, as the flexible nature of the substrate may be exploited without unduly diminishing the barrier properties of the packaging material. Suitable flexible substrates include paper and plastic films, such as polyethylene, polypropylene, polyester, polyamide, and polyvinyl chloride.

[0033] The one or more inflexible barrier layers may comprise inflexible aluminium oxide or inflexible silicon oxide. The one or more flexible barrier layers may comprise flexible aluminium oxide or flexible silicon oxide. It will be understood that it is the flexibility of the layers that is significant for the formation of an effective barrier material (i.e. the flexible layer is more flexible than the inflexible layer). Suitable combinations of aluminium and silicon oxides can be determined empirically using the following observations made by the inventors:

[0034] Aluminium oxide, having the general formula AIOx, has the stoichiometric formula AI2O3. In this balanced state (where x = 1.5), AIOx has a highly ordered and crystalline form that is inflexible. When made oxygen-deficient (where x < 1.5), the density of the AIOx increases and the flexibility is reduced. Conversely, when made oxygen-rich (where x > 1.5), the density of the AIOx decreases, resulting in an increase in flexibility. Therefore, to increase the flexibility of an aluminium oxide layer, the value of x must be increased to over 1 .5.

[0035] Silicon oxide, having the general formula SiOx, has the stoichiometric formula SiO2 for silicon dioxide (x = 2) that has a highly ordered structure that is inflexible. Silicon monoxide (SiO) may also be formed (where x = 1), which has a more amorphous structure and flexible nature. If all oxygen is removed (x = 0), silicon is formed, which is again a hard, crystalline material lacking flexibility. Therefore, to increase the flexibility of a silicon oxide layer, the value of x must be brought closer to 1.

[0036] In addition, it has been observed that aluminium oxides are, in general, less flexible than silicon oxides.

[0037] Accordingly, in general terms, oxygen deficient and stoichiometric aluminium oxides (where x < 1.5) are considered inflexible aluminium oxides, while oxygen rich aluminium oxides (where x > 1.5) are considered to be flexible aluminium oxides. However, an oxygen rich aluminium oxide (i.e. with xi > 1.5, such as ) may be considered an inflexible aluminium oxide if paired with an oxygen rich aluminium oxide layer, or layers, with further excess oxygen (with X2 > xi > 1 .5).

[0038] Additionally, in general terms, approximately stoichiometric silicon monoxides are considered flexible silicon oxides, while oxygen deficient silicon monoxide and oxygen rich silicon monoxide are considered inflexible silicon oxides. By approximately stoichiometric silicon monoxide it is meant that silicon oxide having formula SiOx, where x is about 1 , such as from 0.4 to 1.6, from 0.5 to 1.5, from 0.6 to 1.4, from 0.7 to 1.3, from 0.8 to 1.2, or from 0.9 to 1.1. Generally, for multiple silicon oxide layers, the layer more closely approximating silicon monoxide is considered to be the flexible layer. In embodiments, the inflexible barrier layer comprises an inflexible aluminium oxide and the flexible barrier layer comprises a flexible aluminium oxide. The flexible aluminium oxide may be a more oxygen-rich aluminium oxide than the inflexible aluminium oxide. The flexible aluminium oxide preferably has a higher proportion of oxygen than AI2O3. Expressed using formulae, the flexible aluminium oxide may have formula AIOx and the inflexible aluminium oxide may have formula AlOy, wherein x > y and x > 1.5. In embodiments with multiple inflexible barrier layers or multiple flexible barrier layers, layers of the same type may have the same aluminium oxide. Alternatively, they may have different aluminium oxides.

[0039] In embodiments, the inflexible barrier layer comprises an inflexible silicon oxide and the flexible barrier layer comprises a flexible silicon oxide. In certain embodiments, the flexible silicon oxide is approximately stoichiometric silicon monoxide and the inflexible silicon oxide is more oxygen-rich or more oxygen deficient than the flexible silicon oxide. In other words, the flexible silicon oxide more closely approximates silicon monoxide than the inflexible silicon oxide. By approximately stoichiometric silicon monoxide it is meant that silicon oxide having formula SiOw, where w is about 1 , such as from 0.4 to 1.6, from 0.5 to 1.5, from 0.6 to 1.4, from 0.7 to 1.3, from 0.8 to 1.2, or from 0.9 to 1.1. Expressed using formulae, the flexible silicon oxide has formula SiOw and inflexible silicon oxide has formula SiOz, wherein either z < w < 1 or z > w > 1. In embodiments with multiple inflexible barrier layers or multiple flexible barrier layers, layers of the same type may have the same silicon oxide. Alternatively, they may have different silicon oxides.

[0040] In embodiments, the inflexible barrier layer comprises an inflexible aluminium oxide and the flexible barrier layer comprises a flexible silicon oxide. The inflexible aluminium oxide may be oxygen deficient or stoichiometric aluminium oxide. The flexible silicon oxide may be approximately stoichiometric silicon monoxide.

[0041] In other embodiments, the inflexible barrier layer comprises an inflexible silicon oxide and the flexible barrier layer comprises a flexible aluminium oxide. The inflexible silicon oxide may be approximately stoichiometric silicon (i.e. SiOx where x is about 0, such as less than 0.1 , less than 0.2, less than 0.3, or less than 0.4) or silicon dioxide (i.e. SiOx where x is about 2, such as greater than 1 .6, greater than 1 .7, greater than 1.8, or greater than 1.9). The flexible aluminium oxide may be an oxygen rich aluminium oxide. In certain embodiments, the barrier material comprises one inflexible barrier layer laminated between a pair of flexible barrier layers. This has a protective effect on the inflexible barrier layer. For example, an inflexible silicon oxide layer sandwiched between two flexible silicon oxide layers.

[0042] Considering the above description of the flexibility or inflexibility of the Aluminium oxide and Silicon oxide, in the context of the invention it is considered that a barrier layer is inflexible when its elongation at break is less than 5% and is flexible when its elongation at break is more than 5% according to ISO 1924-2.

[0043] It will be understood that the barrier material may comprise more than three layers. For example, the barrier material may comprise multiple inflexible barrier layers alternating with the flexible barrier layers. Due to off-setting of any defects in the inflexible barrier layers, moisture or gases traversing the barrier material must pass through at least one inflexible barrier layer, increasing the barrier properties of the barrier material postprocessing.

[0044] Each layer may have a thickness of from 5 to 500 nm, preferably from 10 to 200 nm, more preferably from 15 to 100 nm, most preferably from 20 to 50 nm.

[0045] The packaging material may further comprise one or more additional components selected from adhesives, polymer layers (such as protective polymer layers), heat sealing layers, ink layers, and overcoat varnishes.

[0046] The packaging material described herein may be formed into a container. For example, if a flexible substrate such as paper is used, the packaging material may be pressed (such as in a punch process) to form the desired shape. Alternatively, or additionally, the packaging material may be folded, twisted, and / or cut to form the desired shape and affixed in place. Affixation may be achieved using adhesives or heat seals previously applied to the packaging material, or by using additional adhesives. The packaging material may be used to form part of a composite material. For example, the packaging material may be adhered (e.g. by lamination or adhesives) to a more rigid form, such as paperboard or cardboard.

[0047] The present invention also relates to a container comprising the packaging material described herein. In embodiments, the container consists of, or consists essentially of, the packaging material. Alternatively, the container comprises the packaging material and additional structural elements, such as rigid elements, closures, or adhesives. In embodiments, the container takes the form of a capsule or pod.

[0048] The present invention also relates to the use of the packaging material or the container described herein for the storage of an edible product for human or animal consumption. Preferably, said edible product is a powder, a gel, or kibbles and is selected within the list of: ground coffee, soluble coffee, nutrition compositions for infant, adult, or elderly consumption, soup, confectionery or candies, chocolate-based products, dry animal food, dairy products.

[0049] The present invention relates to a method of forming a packaging material, the method comprising sequentially applying one or more inflexible barrier layers and one or more flexible barrier layers to at least a portion of a substrate to form a barrier material thereon. Preferably, the inflexible and flexible barrier layers are applied alternately.

[0050] Applying the or each inflexible barrier layer and the or each flexible barrier layer may be done by any suitable technique for the deposition of thin layers of aluminium oxide or silicon oxide. For example, chemical vapour deposition (CVD) or atomic layer deposition (ALD) may be used. ALD is a preferred technique, particularly spatial ALD (SALD), and atmospheric pressure SALD (AP-SALD). These latter techniques permit high throughput of the packaging material and allows a roll-to-roll process to be used.

[0051] In embodiments, a continuous process is used that additionally forms the packaging material into a container, or a precursor to a container. For example, a flexible substrate may be unwound, have the barrier material applied (i.e. by SALD or AP-SALD) to its surface, and be punched to form a capsule or pod ready for filling and sealing.

[0052] Preferably, the packaging material is as described herein.

[0053] Exemplary Embodiment

[0054] In one embodiment, the packaging material comprises, from base to top, a paper substrate, a first flexible layer (e.g. comprising approximately stoichiometric silicon monoxide or oxygen rich aluminium oxide), an inflexible layer (e.g. comprising oxygen rich silicon monoxide, silicon dioxide, stoichiometric aluminium oxide, or oxygen deficient aluminium oxide), and a second flexible layer (e.g. comprising approximately stoichiometric silicon monoxide or oxygen rich aluminium oxide). The packaging material may comprise further layers, such as a protective polymer layer located between the paper substrate and the first flexible layer.

Claims

CLAIMS:

1. A packaging material comprising: a flexible substrate; and a barrier material over at least a portion of the flexible substrate, the barrier material comprising one or more inflexible barrier layers and one or more flexible barrier layers arranged alternately; wherein the or each inflexible barrier layer comprises an inflexible aluminium oxide or an inflexible silicon oxide; and wherein the or each flexible barrier layer comprises a flexible aluminium oxide or a flexible silicon oxide.

2. The packaging material of claim 1 , wherein the flexible substrate is polymer film (such as polyethylene, polypropylene, polyester, polyamide, or polyvinyl chloride) or paper.

3. The packaging material of claim 1 or claim 2, wherein the or each flexible barrier layer comprises flexible aluminium oxide and the or each inflexible barrier layer comprises inflexible aluminium oxide.

4. The packaging material of claim 3, wherein the flexible aluminium oxide is more oxygen-rich than the inflexible aluminium oxide, optionally wherein the flexible aluminium oxide has formula AIOx and the inflexible aluminium oxide has formula AlOy, wherein: x > y ; and x > 1.5.

5. The packaging material of claim 1 or claim 2, wherein the or each flexible barrier layer comprises flexible silicon oxide and the or each inflexible barrier layer comprises inflexible silicon oxide.

6. The packaging material of claim 5, wherein the flexible silicon oxide is stoichiometric silicon monoxide and the inflexible silicon oxide is more oxygen-rich or more oxygen deficient than the flexible silicon oxide, optionally wherein the flexible silicon oxide has formula SiOw and inflexible silicon oxide has formula SiOz, wherein: z < w < 1 ; or z > w > 1.

7. The packaging material of claim 1 or claim 2, wherein the or each flexible barrier layer comprises flexible silicon oxide and the or each inflexible barrier layer comprises inflexible aluminium oxide.

8. The packaging material of claim 1 or claim 2, wherein the or each flexible barrier layer comprises flexible aluminium oxide and the or each inflexible barrier layer comprises inflexible silicon oxide.

9. The packaging material of any preceding claim, wherein the barrier material comprises one inflexible barrier layer laminated between a pair of flexible barrier layers.

10. The packaging material of any preceding claim, further comprising one or more of adhesives, a polymer layer (such as a protective polymer layer), a heat sealing layer, an ink layer, and an overcoat varnish.

11. A container comprising the packaging material of any one of claims 1 to 10.

12. Use of the packaging material of any one of claims 1 to 10, or the container of claim 11 , for the storage of an edible product for human or animal consumption.

13. A method of forming a packaging material, the method comprising sequentially applying one or more inflexible barrier layers and one or more flexible barrier layers to at least a portion of a substrate to form a barrier material thereon.

14. The method of claim 13, wherein applying one or more inflexible barrier layers and one or more flexible barrier layers comprises atomic layer deposition, preferably spatial atomic layer deposition, such as atmospheric pressure spatial atomic layer deposition.

15. The method of claim 13 or claim 14, wherein the packaging material is as defined in any of claims 1 to 10.

Images