Moisture modulating materials and methods

Abstract

The present invention relates generally to moisture vapour transmission modulators and / or humidity control materials, and more particularly but not necessarily exclusively, to compositions for decreasing the moisture vapour transmission rate and / or humidity control and their method of use. In some forms, the composition of the invention may be applied to a material. Such materials may be used in packaging goods prone to spoilage such as food. Such materials may be used to reduce or prevent degradation of or damage to packaged electronics, pharmaceuticals, and dry products such as paper (for example, so as to prevent curl in copy paper). Such materials may be used to form packaging that may otherwise be weakened by the action of liquids such as water. Such materials may be used to protect other packaging components added to protect contents but are prone to degradation under high moisture environments by way of example repulpable and compostable materials are subject to loss of barrier performance under high humidity conditions.

Description

[0001] MOISTURE MODULATING MATERIALS AND METHODS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to moisture vapour transmission modulators and / or humidity control materials, and more particularly but not necessarily exclusively, to compositions for decreasing the moisture vapour transmission rate and / or humidity control and their method of use. In some forms, the composition of the invention may be applied to a material. Such materials may be used in packaging goods prone to spoilage such as food. Such materials may be used to reduce or prevent degradation of or damage to packaged electronics, pharmaceuticals, and dry products such as paper (for example, so as to prevent curl in copy paper). Such materials may be used to form packaging that may otherwise be weakened by the action of liquids such as water. Such materials may be used to protect other packaging components added to protect contents but are prone to degradation under high moisture environments - by way of example repulpable and compostable materials are subject to loss of barrier performance under high humidity conditions.

[0004] BACKGROUND TO THE INVENTION

[0005] A high relative humidity environment can facilitate the growth of microorganisms such as bacteria and mould. Even under cold conditions, a high relative humidity presents problems as moisture can result in unwanted ice crystals being formed on a product. In both cases, where the product is food, accelerated spoilage will usually occur.

[0006] Numerous approaches to shielding a product from the impact of environmental moisture have been taken.

[0007] One such approach is to use product packaging that provides a moisture barrier, such as sealed metal packaging, hard plastic packaging, or soft plastic packaging. In many cases such moisture barriers are costly, weighty, and / or expensive, and may not provide sufficient barrier properties.

[0008] The ability of a material for product packaging to protect contents from environmental moisture is typically referred to as their moisture vapor transmission rate (MVTR). That rate is determined by measuring its resistance to moisture penetrating the packaging material under a constant pressure. Whilst it may be generally considered that a plastic barrier is impermeable to water vapour, some low -density polyethylene films may have a MVTR of as much as 16-23 g / m2 / 24hr for films having a thickness of about 25 microns. For reference, an aluminium foil laminate may have a MVTR of 0.001 g / m2 / 24hr, this being effectively impermeable to water vapour.

[0009] However, in some instances, it may be preferable that the packaging allows for moisture vapour to pass through and that the product within the packaging is not sealed within the packaging. An example of this is when the product itself is hygroscopic and can release water vapour upon increasing temperatures, e.g. tomatoes. In such instances, if the temperature increases then the water vapour from the product may condense within the packaging and damage the product. Accordingly, the packing material needs to be carefully selected based on the properties of the product. It is therefore desirable to be able to modulate the moisture barrier properties of a packaging product, depending on the product to be packaged.

[0010] Another approach to reducing the impact of environmental moisture on packaged products, which is often used in combination with the use of a packaging material that provides some degree of a moisture barrier, is to include a dessicant material within the packaging. The dessicant will typically compete with the product for absorbing moisture and reduce spoilage. Existing desiccants have limited capacity for absorbing water before the desiccant is saturated, and once saturated further absorption of water is not possible.

[0011] Existing desiccants are provided in the form of tablets, sachets, and dry powders. A common example in the art of this is silica gel in the form of spherical beads packaged into a sachet which is placed into a package so it can absorb moisture that enters the package. Desiccants in such forms can be accidentally ingested or can be aerosolised upon handling which presents a health risk, that varies depending on the nature of the desiccant. Other more effective desiccants such as calcium chloride become liquid at high humidities and can cause damage.

[0012] Another problem that arises with the use of absorbent or adsorbent packaging materials is that their structural integrity may be reduced upon exposure to moisture. For example, the ubiquitous corrugated cardboard packaging provides a relatively strong packaging material when it is dry. However, exposure to moisture - even small quantities of moisture - can dramatically reduce its structural integrity. One previous approach to reducing the impact of moisture on such packaging is to laminate or impregnate the cardboard with a moisture resistant material such as a synthetic polymer or a wax. However laminating or impregnating the cardboard with such materials will generally render the cardboard as non- recyclable, may be relatively expensive to implement, and also may still leave sufficient of the cardboard unlaminated that water will ingress and then readily wick through the material. A common solution to retaining an acceptable structural integrity for the packaging material for a sufficient period of time is to over-engineer the package by using excess packaging material to compensation for the loss of strength due to high humidity and fluctuating humidity environments, however such over-engineering add cost, weight and / or bulk.

[0013] In many cases, product packaging designed to reduce the transmission of moisture is a disposable item and so cost and waste considerations are significant. In many cases the product packaging will typically not decompose. Whilst the recycling of some of these forms of packaging may reduce the environmental impact of the use of that packaging, inevitably some of the material will enter landfill and that waste compounds over time. Even relatively cheap disposable materials such as polyethylene that are used to provide soft plastic packaging are not impervious to moisture. While some biodegradable packaging materials are becoming more widely used, most are expensive and have poor moisture barrier properties.

[0014] It is an object of the invention to provide a packaging material that reduces the impact of moisture on the contents of the packaging material.

[0015] Alternatively, or in addition, it is an object of the invention to provide a method of treating a material to reduce the impact of moisture on the material.

[0016] Alternatively, or in addition, it is an object of the invention to provide a method of treating a packaging material to reduce the impact of moisture on the material.

[0017] Alternatively, or in addition, it is an object of the invention to provide a biodegradable and / or recyclable packaging material that reduces the impact of moisture on the contents of the packaging material.

[0018] It is an object of the invention to provide a packaging material that reduces the impact of oxygen on the contents of the packaging material.

[0019] Alternatively, or in addition, it is an object of the invention to provide a biodegradable and / or recyclable packaging material that reduces the impact of oxygen on the contents of the packaging material.

[0020] It is an object of the invention to provide a packaging material that reduces the impact of moisture and oxygen on the contents of the packaging material. Alternatively, or in addition, it is an object of the invention to provide a biodegradable and / or recyclable packaging material that reduces the impact of moisture and oxygen on the contents of the packaging material.

[0021] Alternatively, or in addition, it is an object of the technology to at least provide the public with a useful choice.

[0022] SUMMARY OF THE INVENTION

[0023] In a first aspect the invention provides a composite material (such as a packaging material, fabric or building material) including a first layer and a second layer bonded to the first layer, wherein: i) the first layer includes a substrate including a matrix of fibres wherein a hygroscopic material (such as a water soluble hygroscopic salt) is bound (such as adsorbed) to the fibres (such as onto the surface of the fibres); and ii) the second layer is a moisture (such as provided as water) and / or gas (such as oxygen) resistive layer.

[0024] Typically the second layer will be at least a moisture resistive layer.

[0025] It has been discovered that the use of a hygroscopic material (such as a water soluble hygroscopic salt, such as having a cation selected from calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium, and combinations thereof) bound (such as adsorbed) to a matrix of fibres provides a decreased moisture vapour transmission rate compared with the same material that lacks the a hygroscopic material (such as hygroscopic salt).

[0026] Preferably the cation of the hygroscopic salt is selected from calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium, and combinations thereof.

[0027] The second layer is selected to be at least partially, such as substantially, moisture (such as provided as water) and / or gas (such as oxygen) resistive . As used herein, the expression "moisture resistive" refers to the ability of a material to at least partially resist the penetration of moisture into and / or through the material. The ability of a material to resist the penetration of moisture may be measured and quantified as a moisture vapor transmission rate (MVTR). The determination of the MVTR is performed under conditions of constant pressure. Whilst it may be generally considered that a plastic barrier is impermeable to water vapour, some low-density polyethylene films may have a MVTR of as much as 16- 23 g / m2 / 24hr for films having a thickness of about 25 microns. For reference, an aluminium foil laminate may have a MVTR of 0.001 g / m2 / 24hr, this being effectively impermeable to water vapour. Glass is also considered to be impermeable to moisture and air. As used herein, moisture resistive materials will typically have a MVTR of less than 300 g / m2 / 24hr, preferably have a MVTR of less than 100 g / m2 / 24hr, preferably have a MVTR of less than 50 g / m2 / 24hr, more preferably have a MVTR of less than 30 g / m2 / 24hr, such as a MVTR of less than 10 g / m2 / 24hr.

[0028] Test methods that may be used to measure MVTR (sometimes referred to as WVTR) in the present invention include ASTM F 1249 (such as ASTM F 1249-20) and ISO 15106-2, although these should not be seen as limiting. Other test methods that may be useful include ASTM E96, ISO 15106-1, and ISO 15106-3.

[0029] Preferably the moisture (such as provided as water) and / or gas (such as oxygen) resistive second layer will be provided as a substantially continuous layer. As used herein, the expression "substantially continuous layer" implies that at least to the unmagnified human eye, the layer lacks any discernible pores. At a microscopic level, it will be appreciated that pores may exist but these will be limited to the extent that the second layer is at least partially, such as substantially moisture (such as provided as water) and / or gas (such as oxygen) resistive.

[0030] Preferably the invention relates to a composite material (such as a packaging material, fabric or building material) including a first layer and a second layer bonded to the first layer, wherein:

[0031] 1) the first layer includes substrate including a matrix of fibres wherein calcium chloride is bound (such as adsorbed) to the fibres (such as onto the surface of the fibres); and

[0032] 2) the second layer is a moisture (such as provided as water) and / or gas (such as oxygen) resistive layer.

[0033] Typically the second layer will be at least a moisture resistive layer.

[0034] It will be appreciated that the composite material of the invention may be referred to as having a sandwich construction. The composite material (such as a packaging material, fabric or building material) of the present invention may further include one or more other layers used in the packaging industry such as printed layers, compacted layers, additional barrier layers - such as additional moisture (such as provided as water) and / or gas (such as oxygen) resistive layers, etc. In a second aspect the invention provides a coating system for applying to a substrate including a matrix of fibres to decrease moisture vapour transmission across said substrate, the coating system including: a first composition including: a hygroscopic material (such as a water soluble hygroscopic salt which is water soluble, preferably wherein the cation of the hygroscopic salt is selected from calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium, and combinations thereof); and a first carrier; a second composition including: a polymeric or pre-polymeric material and optionally a second carrier.

[0035] As used herein the term "pre-polymeric material" will generally refer to monomeric component(s) or oligomeric component(s) or similar that will undergo a polymerisation step (including curing, selfpolymerisation, initiated polymerisation) upon application of the second composition to the substrate. The first carrier and the second carrier (when used) may each be the same or different and may be selected from any carrier suitable for dispersing the hygroscopic material (such as the water soluble hygroscopic salt), or the polymeric or pre-polymeric material (respectively). In some embodiments the first carrier and the second carrier (when used) are independently selected from an aqueous carrier, such as water.

[0036] In a third aspect the invention provides a method of treating a substrate including a matrix of fibres to provide a composite material having a decreased moisture vapour transmission compared with the substrate, the method including the steps of: i. providing a substrate including a matrix of fibres; ii. applying a first composition to the substrate, the composition including: a hygroscopic material (such as a water soluble hygroscopic salt which is water soluble, preferably wherein the cation of the hygroscopic salt is selected from calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium, and combinations thereof); and a first carrier; iii. removing at least a portion of the first carrier from the substrate; iv. following step iii), providing the substrate with a moisture (such as provided as water) and / or gas (such as oxygen) resistive second layer, so as to provide the composite material.

[0037] The step of providing the substrate with a moisture (such as provided as water) and / or gas (such as oxygen) resistive second layer may involve the modification of the structure of the substrate and / or the addition of material to the substrate. Where the structure of the substrate is modified, it may be densified by calendaring with a steel nip or hot soft calendaring, providing a denser second layer, and a less dense first layer. By way of another example, the addition of material to the substrate may include the steps of: applying a second composition to the substrate, the second composition including: a polymeric or prepolymeric material and optionally a second carrier; and removing at least a portion of the second carrier, when used.

[0038] Any step of removing a carrier, but especially the step of removing at least a portion of the first carrier from the substrate may include pressing (to express the carrier from the substrate) and / or drying.

[0039] The method of the third aspect will typically coat at least a portion of the substrate with the hygroscopic material (such as the hygroscopic salt) such that at least a portion of the hygroscopic material (such as the hygroscopic salt) will be bound (such as adsorbed) to at least a portion of the matrix of fibres of the substrate.

[0040] The method of the invention may include a number of additional step(s). For example: i) the first composition may be applied and the first carrier removed iteratively, a plurality of times, so as to potentially increase the amount of the hygroscopic material (such as the hygroscopic salt) that is loaded on the substrate; and / or ii) in forming the second layer the structure of the substrate may be modified and / or material may be added to the substrate using a second composition, a plurality of times, so as to potentially increase the water resistivity of the second layer.

[0041] Without wishing to be bound by theory, it is believed that iteratively applying the first composition and / or iteratively forming the second layer may provide a lower MVTR to the composite material so produced from the substrate.

[0042] Where the first composition is applied a plurality of times, by way of example the first composition might be applied to both sides of a substrate sequentially or simultaneously, and allowed to substantially penetrate the substrate from both sides before adding the subsequent second composition.

[0043] For example, the first carrier (carrying the hygroscopic material) might be applied to both sides of the sheet sequentially or simultaneously) and allowed to substantially penetrate the base sheet from both surfaces before adding the subsequent resistive surface layer or layers. Further steps may be performed to the composite material, so as to provide the composite material with one or more other layers used in the packaging industry such as printed layers, compacted layers, additional barrier layers (such as oxygen resistive layers adjacent to the packaged product), etc.

[0044] For example, further steps (such as coating steps) may be undertaken once, twice, three times, four times, or five times, etc.

[0045] The present inventors have realised that by using the hygroscopic material (such as the water soluble hygroscopic salt) in combination with a moisture (such as provided as water) and / or gas (such as oxygen) resistive layer it is possible to reduce the amount of polymeric material used in the final coated product compared with traditional moisture resistive composite materials typically used in packaging. For instance, a substrate coated in a traditional polymer coating may only be able to decrease the MVTR by X when the polymer coating is provided at a coverage of Y gsm. By incorporating the hygroscopic material (such as the hygroscopic salt) the substrate will typically need less than Y gsm coverage of the polymer to achieve the same (or better) MVTR of X.

[0046] Without wishing to be bound by theory, the second layer of the invention provides a physical barrier, slowing the rate at which water vapor moves into and out of the paper. While it restricts the overall transfer of moisture, it does not directly affect the moisture gradient driving diffusion. The hygroscopic material (such as hygroscopic salt) within the paper actively absorbs moisture from the surrounding environment, lowering the localized humidity immediately adjacent to the composite material. This creates a microenvironment immediately adjacent to the material having a reduced vapor pressure, thereby diminishing the driving force for moisture transfer. The second layer slows vapor entry, giving the hygroscopic material (such as the hygroscopic salt) more time to adsorb moisture and maintain a low-humidity zone adjacent (such as immediately adjacent) to the composite material (such as inside a package formed from the composite material). Simultaneously, the hygroscopic material (such as the hygroscopic salt) reduces the moisture gradient, further decreasing the driving force for water vapor to penetrate the second layer. Together, these mechanisms work synergistically, each enhancing the effectiveness of the other, to slow moisture transmission and provide superior protection for packaged goods.

[0047] The present invention provides a number of significant advantages, especially where the composite material of the invention is provided as packaging material, and a package is formed therefrom. One advantage may be provided where the package forms an enclosure so that the contents of the package can be sealed from the environment external of the package to the contents. In such an example, the packaging material will provide a decreased moisture vapour transmission rate compared with the same material that lacks the hygroscopic material (such as the water soluble hygroscopic salt) and / or moisture (such as provided as water) and / or gas (such as oxygen) resistive layer. In practical terms, this function provides that the contents of the enclosed package will retain a substantially constant moisture level over a period of time. Where the package contains a product that is prone to spoilage, such as food, the shelf-life of the product may be increased. In some embodiments, the environment external of the package to the contents will have a higher relative humidity than the environment internal of the package. In some embodiments, the environment external of the package to the contents will have a lower relative humidity than the environment internal of the package. In some embodiments the relative humidity of the environment external of the package to the contents will fluctuate (such as through a diurnal cycle or warming and cooling) between a higher relative humidity and a lower relative humidity compared with the environment internal of the package. In some or all of these embodiments it will generally be an advantage to decrease the moisture vapour transmission rate through a packaging material so as to retain the qualities of the contents of the package in a condition similar to those when first enclosed in the package.

[0048] One advantage may be provided where the packaging material provides superior mechanical properties when relatively dry, and inferior mechanical properties if it becomes wet or at least wetter. Such wetting may occur through a number of mechanisms: such as a single incident of being contacted with a liquid such that the liquid wicks through the material; or such as through fluctuating temperature and / or relative humidity conditions that gradually expose the material to wetting conditions. In each or any case it would be appreciated that being able to reduce the exposure of the material to moisture would lead to the material retaining the superior mechanical properties for longer. The present invention provides a packaging material that provides a decreased moisture vapour transmission rate compared with the same material that lacks the hygroscopic material (such as the water soluble hygroscopic salt) and moisture (such as provided as water) and / or gas (such as oxygen) resistive layer, which in turn will typically lead to a reduced exposure of the material to moisture. In this way the use of the hygroscopic material (such as the water soluble hygroscopic salt) and moisture (such as provided as water) and / or gas (such as oxygen) resistive layer provides a type of modified atmosphere package, namely a type of packaging system in which the atmospheric composition inside the package is altered from the normal air composition to extend the shelf life of perishable products. In this case the modification is to relative humidity. Two examples of packaging that benefits mechanically from the present invention are detailed below. In the first example, where the material is corrugated cardboard packaging used in box manufacture, it will be appreciated that the mechanical properties of such cardboard will be superior when it is dry compared with when it is wetted. Advantageously, by applying the hygroscopic material (such as the water soluble hygroscopic salt) and moisture (such as provided as water) and / or gas (such as oxygen) resistive layer to the cardboard, the rate of transmission of environmental moisture through the cardboard material will be decreased and hence the superior mechanical properties will be sustained for a greater period of time than in the absence of the hygroscopic material (such as the water soluble hygroscopic salt) and / or moisture (such as provided as water) and / or gas (such as oxygen) resistive layer. Cardboard packaging in particular (but also many other forms of packaging to which the present invention is suited) is typically over-engineered so as to account for the assumed loss of mechanical strength as a result of exposure to moisture over time. Another advantage of reducing the rate of transmission of environmental moisture through the cardboard material using the present invention is that the cardboard packaging may be designed more efficiently since it does not need to be overengineered to the same extent.

[0049] In the second example, where the material is a laminated cellulosic material used to package liquids, such as marketed by the international company TetraPak®, it is a recognised problem that over time the core cellulosic material becomes increasingly more exposed to moisture from the liquid contents of the package and / or the external environment. In time the mechanical properties of the cellulosic material are weakened which manifests itself with bulging of the package - namely deformation of the generally planar surfaces towards having a rounded form. Advantageously, by applying the hygroscopic material (such as the water soluble hygroscopic salt) and moisture (such as provided as water) and / or gas (such as oxygen) resistive layer to the cardboard, the rate of transmission of environmental moisture through the cardboard material will be decreased and hence the superior mechanical properties will be sustained for a greater period of time than in the absence of the hygroscopic material (such as the water soluble hygroscopic salt) and / or moisture (such as provided as water) and / or gas (such as oxygen) resistive layer.

[0050] In the third example, it will be appreciated that the product to be packaged (such as one that is prone to spoilage) may be substantially dry, partly wet, or otherwise, and may be provided at any temperature. For example, some frozen products are provided packaged in laminated cellulosic material such as laminated cardboard packaging, one example of which is ice cream. Variations in storage temperature of such frozen products, such as during transport, can lead to moisture in the packaging material undergoing a freeze / thaw action which in turn can rapidly degrade the structure of the cellulosic material relied on for the packaging's structure. Advantageously, by applying the hygroscopic material (such as the water soluble hygroscopic salt) and moisture (such as provided as water) and / or gas (such as oxygen) resistive layer to the cardboard, the rate of transmission of environmental moisture through the cardboard material will be decreased and hence the superior mechanical properties will be sustained for a greater period of time than in the absence of the hygroscopic material (such as the water soluble hygroscopic salt) and / or moisture (such as provided as water) and / or gas (such as oxygen) resistive layer.

[0051] Another example of a useful application of the composite material of the present invention would be for multi-layer paper packaging such as used for the bulk packaging of moisture sensitive materials (e.g. cement and dog foods). In this case the composite material of the present invention could be used as the outer ply to preserve the dry strength of the inner layers and the product.

[0052] Conventional moisture barrier materials such as polyethylene, polyacrylates, or waxes provide a moisture resistive layer provided by a matrix of those hydrophobic materials. The strength of that barrier will generally be proportional to the thickness of the layer and the hydrophobicity of the matrix material.

[0053] Once the layer is penetrated, or if the layer does not otherwise fully cover the material, then the material will be exposed to moisture. Where the material is capable of wicking moisture, such a weakness in the layer will inevitably lead to the ingress of moisture.

[0054] The present invention differs from other previous approaches to modifying the water permeability of a material. In each case the previous approaches seek to solely create a resistive barrier layer at the surface of the paper, typically by the technique of dispersion coating which is inherently prone to imperfections imposed by the irregular surface profile of paper on a microscopic scale. For instance, WO2021224881 discloses the application of a glyceride and / or a fatty acid salt to a cellulosic / polymeric material to make it hydrophobic and / or lipophilic. Likewise, WO2021105231 discloses the use of a composite material having multiple layers of water impermeable polymers, most of which are non-biodegradable and would typically mean that the coated product is neither recyclable nor biodegradable. Similarly, the technology in WO2021105231 uses (meth)acrylate polymers to reduce water permeability.

[0055] Without wishing to be bound by theory, it is believed that the application of the hygroscopic material (such as the water soluble hygroscopic salt) in combination with a moisture (such as provided as water) and / or gas (such as oxygen) resistive layer to the material in the present invention provides a function that is different to merely the use of the resistive function attempted by conventional moisture barrier materials (such as polyethylene, polyacrylates, or waxes). Again without wishing to be bound by theory, conceptually it is believed that the present invention provides a capacitive function (i.e. functions as a capacitor by conceptually substantially preventing water movement up to a threshold determined by the amount and type of the salt applied to the substrate in much the same way as an electronic capacitor functions to accumulate electrical charge until a discharge event) which importantly is provided across the whole material (since the hygroscopic material (such as the water soluble hygroscopic salt) is believed to be bound (such as adsorbed) to the surface of / or entrained within, and in intimate contact with, the material) rather than as a layer separate to the material. Again without wishing to be bound by theory it is believed that the hygroscopic material (such as the water soluble hygroscopic salt) functions synergistically with the moisture (such as provided as water) and / or gas (such as oxygen) resistive layer so as to provide a reduction in the MVTR that would not have been predicted based on the additive properties of the individual components (even if those functions were known at the relevant priority date). The hygroscopic material (such as the water soluble hygroscopic salt) has a capacity (or threshold) to interact with moisture beyond which the hygroscopic material (such as the water soluble hygroscopic salt) will effectively become saturated and no longer inhibit moisture vapour transmission to or across the material. Below such a capacity (or threshold) the moisture vapour transmission will be inhibited and it is believed that adding more hygroscopic material (such as more water soluble hygroscopic salt) will lead to greater inhibition of moisture vapour transmission.

[0056] The present invention may more broadly relate to a material including a matrix of fibres, the matrix having at least one of the following: a) a first substance having water adsorption gualities, the substance being bound (such as adsorbed) to the fibres (such as onto the surface of the fibres), and b) a second substance and / or morphology that inhibits moisture transmission.

[0057] The present invention may relate to a method of applying the first substance and / or the second substance and / or morphology to the material.

[0058] Further aspects of the technology, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the technology.

[0059] BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the technology will be described below by way of example only, and without intending to be limiting, with reference to the following drawings, in which:

[0060] Figure 1 shows an example of the water holding capacity per coating weight of compositions according to the invention;

[0061] Figure 2 shows an example of the water holding efficiency of coatings with microfibri Hated cellulose, and both microfibrillated cellulose and nanocrystalline cellulose, with varying calcium chloride content;

[0062] Figure 3 shows an absorption isotherm across a composite material of the present invention prepared using calcium chloride on paper substrate. The graph shows a gradual increase in the moisture vapour transmission rate to a maximum rate over a period of eight hours. The rate of transmission is low at 1 g / m2 / day for about two hours. This is followed by a period of linear increase from 1 to 7.5 g / m2 / day of about 6 hours corresponding to the period of progressive adsorption of water by the calcium chloride. Eventually the front of saturated calcium chloride reaches the interior surface of the paper and the subsequent period of constant rate corresponds to the inherent resistance of the paper and coating. This paper had a thin resistive coating being formed of a platy kaolin clay as the pigment (50% w / w) and a styrene-butadiene (SB) latex as the polymer material (50% w / w). The coat weight was 8 gsm.

[0063] Figure 4 shows MVTR vs. Time graph demonstrating the effect of layering and orientation in the composite materials of the invention.

[0064] Figure 5 shows MVTR vs. Time graph demonstrating the effect of layering and orientation in the composite materials of the invention.

[0065] Figure 6 shows moisture (water) vapour transmission rate data for formulation G3.

[0066] Figure 7 shows moisture (water) vapour transmission rate data for formulation G3 (reversed).

[0067] Figure 8 shows a comparison between vapour pressure gradient across a traditional Fickian stack (obeying Fick's law of diffusion) versus the system of the present invention which uses calcium chloride.

[0068] DETAILED DESCRIPTION OF THE INVENTION

[0069] Hygroscopic material (such as hygroscopic salt)

[0070] The present invention is predicated in part on the realisation that the properties (such as moisture vapor transmission rate) of the matrix of fibres may be modulated by the presence of a hygroscopic material (such as a water soluble hygroscopic salt) bound (such as adsorbed) to the fibres (such as onto the surface of the fibres). As used herein the term "hygroscopic" refers to the ability of the hygroscopic material (such as the water soluble hygroscopic salt) to absorb water from air. Such a hygroscopic material (such as a water soluble hygroscopic salt) may be applied to the to the fibres (such as onto the surface of the fibres) in a carrier, such as an aqueous carrier, such as in water. The hygroscopic material (such as the water soluble hygroscopic salt) will be dispersed in the carrier, such as dissolved in the carrier. After application of the hygroscopic material (such as the water soluble hygroscopic salt) in a carrier, the subsequent removal of the carrier will leave behind the hygroscopic material (such as the water soluble hygroscopic salt). Where used, such a salt may be provided as a hydrate, although it is believed that a form of the hygroscopic salt that is in less than a fully hydrated state is preferred, such as a partially hydrated form, or an anhydrous form. To that end, the degree of dehydration will depend upon the drying conditions chosen. Typical drying conditions on a paper machine or paper coater achieve a moisture content of 4 to 8%. It is believed that the present invention benefits from a low moisture content, - the dryer the better for maximum initial moisture adsorption capacity of the hygroscopic material.

[0071] It will be appreciated that different materials (such as salts) are hygroscopic to different degrees. The degree of hygroscopicity of any hygroscopic salt used may be considered to be a function of the cation and the anion. Preferred cations are calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium. Preferred anions are chloride, sulphate, carbonate, and nitrate. All combinations of these cations and anions that are hygroscopic and water soluble are contemplated for use in the present invention.

[0072] The present invention contemplates the use of any hygroscopic material which may include hygroscopic salts and non-salts such as silica gel (amorphous silicon dioxide). Preferably the hygroscopic material will be a hygroscopic salt, such as a water soluble hygroscopic salt.

[0073] It will be appreciated that different salts are water soluble to different degrees. The degree of water solubility of the hygroscopic salt may be considered to be a function of the cation and the anion. Preferred cations are calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium. Preferred anions are chloride, sulphate, carbonate, and nitrate. All combinations of these cations and anions that are hygroscopic and water soluble are contemplated for use in the present invention.

[0074] Properties of preferred hygroscopic water soluble salts of the present invention are provided in the table below:

[0075] The table also indicates relative affinity for cellulose - with those noted as *** showing the highest affinity for cellulose (which is a preferred characteristic) and those noted as * showing a lower affinity for cellulose (less preferred). Some preferred salts of the invention are calcium chloride, magnesium chloride lithium chloride, zinc chloride, and aluminium chloride. The most preferred salts of the invention are calcium chloride, magnesium chloride, aluminium sulphate, and calcium nitrate. Of these, calcium chloride is considered to be the most preferred. The invention contemplates the use of either single hygroscopic water soluble salts, or combinations of different hygroscopic water soluble salts.

[0076] Calcium chloride is deliquescent (becomes liquid after adsorbing high amounts of moisture). In situations of exposure to environments with moderate humidity, calcium chloride can absorb excess moisture, potentially helping to keep the material (such as paper fibres) dry and strong. In particular, by reducing the moisture content of the surrounding air, calcium chloride can prevent the paper fibres from swelling, thereby maintaining their mechanical integrity. However, in environments of prolonged exposure to high humidity calcium chloride can become liquid. Once liquid the reverse effect will generally apply to the paper material. In such embodiments, it may be preferable to use non-deliquescent hygroscopic salts such as potassium carbonate and sodium carbonate.

[0077] Without wishing to be bound by theory it is believed that the present invention is particularly effective in reducing moisture transmission across a material due to the following factors shared by the particular hygroscopic salts described herein: i) the salts are soluble in carriers, such as aqueous solvents (such as the preferred carrier water) making them easy to use commercially and easier to recycle and / or biodegrade; ii) the salts are hygroscopic, and in some cases are deliquescent salts. It is believed that the salts form extensive ionic layers bound (such as adsorbed) to the fibres; iii) the salts disperse efficiently across the material (such as the preferred cellulosic material); iv) several of the hygroscopic salts (such as calcium chloride and magnesium chloride) are generally regarded as safe (GRAS) for use in food packaging in particular.

[0078] In some embodiments the hygroscopic salt is lithium chloride. Lithium chloride is highly soluble in water and is hygroscopic. Lithium chloride has an affinity for cellulose surfaces which makes it suitable for cellulose modification processes. As a monovalent cation, lithium (Li+) has a relatively small ionic radius, and it does not typically form extensive ionic layers of adsorbed water on cellulose fibres compared to divalent or trivalent cations like calcium (Ca2+) or aluminium (Al3+).

[0079] In some embodiments the hygroscopic salt is zinc chloride. Zinc chloride is soluble in water and is hygroscopic. Zinc chloride can be used in the modification of cellulose fibres due to its ability to form complexes with cellulose, thereby enhancing its properties such as strength and moisture resistance. Zinc chloride can be used in the production of food packaging materials such as films, coatings, and liners.

[0080] In some embodiments the hygroscopic salt is aluminium chloride. Aluminium chloride is soluble in water and is hygroscopic. It can modify cellulose surfaces and enhance its properties.

[0081] In some embodiments the hygroscopic salt is calcium chloride. Calcium chloride is soluble in water and is hygroscopic. Calcium chloride is classified as Generally Recognized as Safe (GRAS) by the FDA when used in accordance with good manufacturing practices (GMP) and within specified limits. Calcium chloride is approved for direct addition to food and is considered safe for use in various food products. The hygroscopic material may be bound to the matrix of fibres of the substrate at any loading sufficient to modulate the transmission of moisture vapour through the composite material of the invention. Preferably, the hygroscopic material is provided at a dry loading of from 1 to 100 grams per square metre (gsm) of substrate: such as at least 5 gsm; such as at least 10 gsm, such as no more than 50 gsm, such as no more than 25 gsm; such as from 10 to 25 gsm such as from 15 to 19 gsm. For instance, when the substrate is paper (having a weight of, for example, 80 gsm), the hygroscopic material may be provided at a dry loading of from 15 to 19 gsm.

[0082] Substrate

[0083] While it is contemplated for the composite material of the invention to be formed in a process such that the hygroscopic material (such as the hygroscopic salt) is included in the matrix of fibres at the time that the matrix of fibres is used for forming into a substrate (such as during paper formation) this would be atypical, and instead it would be more typical for the hygroscopic material (such as the hygroscopic salt) to be applied after the matrix of fibres is pre-formed into a substrate (such as packaging material, fabric, or building material). Where applied after the substrate formation, these subsequent processes such as applying the compositions of the invention (such as the use of various forms of coaters), can be directly inline with the papermaking process or subsequently in off-line processes either in a papermill or at the sites of subsequent converting processes.

[0084] In those more typical cases, the substrate to which the hygroscopic material (such as the water soluble hygroscopic salt) and moisture (such as provided as water) and / or gas (such as oxygen) resistive layer is applied may be packaging material, fabric, or building material, and they will include a matrix of fibres. The substrate may be in the form of a membrane, panel, hydrogel, paste, granule, or pellet, for example. The fibres of the substrate will typically be formed of a polymer - the polymer being a biological polymer or a synthetic polymer although blends of biological and synthetic polymers are also contemplated.

[0085] In general, the matrix of fibres of the material will provide a porous structure which can adsorb a hygroscopic material (such as a hygroscopic salt) of the invention. Examples of such structures are all forms of paper, fabric / cloth (e.g. woven, knitted, non-woven, felted, laminated and spun), and porous construction / architectural materials (e.g. plasterboard, ceiling tiles, foam insulation, panels, plaster).

[0086] By way of example only, there are many different types of paper available and suitable for different types of applications. The properties of the paper may be targeted in the paper making process to satisfy market requirements / demand. For traditional applications of a barrier coating / resistive layer, a paper with low porosity and high smoothness is desired primarily so that a dispersion coating of a barrier material will bond to the surface to maximise its barrier properties. While the use of such paper in the current invention is contemplated, it is preferred to use paper that does not have a low porosity. The present inventors have discovered that paper suppliers (such as Mondi, Billerud et al.) that are asked to supply higher porosity papers, generally having a reduced smoothness, have been surprised to be asked to supply such paper. This supports the non-obvious nature of such material for use in the present invention. In particular, the inventors' request contradicts the paper suppliers' current understanding, and commercial availability of such paper is much reduced compared with traditional barrier material paper.

[0087] Preferably the present invention uses unsized, highly porous paper as the substrate. It is believed that such paper provides enhanced adsorption of the hygroscopic material (such as the hygroscopic salt) and application of the moisture (such as provided as water) and / or gas (such as oxygen) resistive layer. In some embodiments the (paper) material to be used as a substrate is uncoated highly porous kraft cellulose-fibre material. Initially it was preferred to use a highly porous and open paper as the substrate to enable uptake of a concentrated calcium chloride solution, because of its high viscosity and high surface energy. However since then it has been possible to use a wider range of substrates, which have benefited from the use of application methodologies such as high pressure pulse coating to force the solution into the paper, so as to achieve saturation with denser papers (a typical paper produced with the no on- machine size press). Porosity has been realized to be less deterministic, and the invention is suitable for application to a substrate with even a moderate level of porosity.

[0088] In some embodiments the paper substrate will have a high resistance to moisture transfer, so as to provide a MVTR of less than 300 g / m2 / day.

[0089] Where the matrix of fibres of the substrate is formed of a polymer, preferably the polymer is biodegradable. More preferably the polymer is compostable under both industrial and non-industrial conditions. One recognised non-industrial composting standard is ISO 14855-1 (2012). An example of such a biodegradable material is one that may degrade in home composting conditions where temperatures typically do not attain the temperatures found in industrial composting settings. Preferably the biodegradable polymer matrix of fibres of the invention is configured to undergo substantial biodegradation within 12 months of being exposed to non-industrial composting conditions. Preferably the biodegradable composition of the invention is configured to fully biodegrade within 24 months of being exposed to non-industrial composting conditions. A polymer that may be used as the matrix of fibres may be selected from any one or more (such as combinations) of the following:

[0090] • an aliphatic polyester such as: polyglycolide / polyfglycolic acid) (PGA), polycaprolactone (PCL), polydioxanone (PDO), polylactic acid (PLA) (including poly(L-lactic acid), poly(D-lactic acid), and poly(DL-lactic acid)), poly(lactic-co-glycolic acid) (PLGA), poly(trimethylene carbonate) (PTMC), poly(butylene succinate-co-butylene adipate) (PBSA), poly(alkyl succinates), including: polyethylene succinate) (PES), (polypropylene succinate) (PPS), poly(butylene succinate) (PBS); polyhydroxyalkanoates (PHA), including polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO), polyhydroxydecanoate (PHD), polyhydroxy-5-phenylvalerate (PHPV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV);

[0091] • an aromatic polyester such as: poly(butylene adipate-co-terephthalate) (PBAT);

[0092] • a polyamide such as BAK 1095 and BAK 2195 (based on caprolactam, butanediol, and adipic acid);

[0093] • a polyurethane that will typically include a biodegradable portion consisting of a polyester (such as PCL, PLA, and PGA);

[0094] • an agro-polymer (such as such as silk, wool, collagen);

[0095] • a polysaccharide (such as starch, hemicellulose, cellulose, chitin, chitosan, alginic acid, cellophane, pectin, pullulan, or modified forms thereof, for example cellulose acetate, products of brown algae (Phaeophyceae)' or red algae Rhodophyta) or green algae (ChlorophytaY)

[0096] • a polypeptide (such as gelatin, wheat gluten, casein, whey protein);

[0097] • a vinyl alcohol such as polyvinylalcohol or vinyl alcohol precursor such as poly(vinyl acetate).

[0098] Without wishing to be bound by theory, it is believed that substrates having a degree of ionic attraction to the hygroscopic salt (where used) of the invention are preferred. In many cases, such substrates will include functional groups that provide a dipole moment capable of attracting and retaining the cation of the hygroscopic salt. It is believed that the ability to attract and retain the cation of the hygroscopic salt enables the hygroscopic salt to be well dispersed in the substrate and in turn attract and retain moisture that comes into the environment of the composite material that includes the hygroscopic salt and the substrate. By attracting and retaining the moisture the present invention is able to decrease the moisture transmission rate across the material.

[0099] In preferred embodiments, the substrate is paper. The paper fibres may be composed of blends of natural polymers, such as cellulose, lignin and hemi-cellulose. Advantageously, the use of cellulose (or a modified form of cellulose) as part or the totality of the substrate of the invention has been shown to provide the following advantages:

[0100] • it attracts and retains the cation of the hygroscopic salt (where used) of the invention - such as the calcium cation of the calcium chloride salt;

[0101] • it is used widely in packaging;

[0102] • it is biodegradable, and is home compostable.

[0103] In some embodiments the substate is a cellulose material such as paper, cardboard, cotton, jute, hemp, sisal, or wood. In some embodiments the substate is a cotton membrane, cellulose membrane, or ligninbased membrane. In some embodiments the substate is paper fibres which are comprised of fibrils, microfibrils which in turn contain cellulose polymers. The cellulose containing fibre may be cellulose fibres extracted from a wood source that are used to make an end product such as paper, paperboard or cardboard. In some embodiments, the cellulose fibres may be combined to form a pulp and are then processed into the desired end product with the desired weight, i.e., grams per square metre (gsm). In some embodiments, when the substate is a paper, the paper weight may be between 50 grams per square meter to 300 grams per square meter, such as about 125 gsm. In some embodiments the material may have a heavier weight than paper - such as heavyweight paperboard which may have a weight of 400 to 600 gsm. Such material is commonly used for more robust packaging applications where additional strength and durability are required, such as rigid boxes, high-end product packaging, and displays. Beyond 600 gsm, the material is often referred to as "chipboard" or "greyboard," and it is primarily used for applications where stiffness and rigidity are essential, such as book covers, binders, and rigid packaging boxes. All of these forms / weights of products are contemplated for use as the material (material) in the present invention.

[0104] In some embodiments the substrate is a starch-based material, including certain types of packaging or starch-based films, which may adsorb salts (such as calcium chloride) through hydrogen bonding, leading to increased water adsorbency.

[0105] In some embodiments the substrate is a hydrogel material. Hydrogels are known for their ability to absorb and retain water. The hydrogel may be formed from polymers such as polyvinyl alcohol (PVOH), polyacrylamide, or polysaccharides, which can form hydrogen bonds with salts (such as calcium chloride) resulting in increased water adsorbency. In some embodiments, the substrate is a chitosan material, derived from chitin, which contains amino and hydroxyl groups that can form hydrogen bonds with salts (such as calcium chloride), resulting in increased water adsorbency. Chitosan is used in various applications, including as a water treatment agent.

[0106] In some embodiments, the substrate is a silica gel material and other silica-based materials which may adsorb salts (such as calcium chloride) through hydrogen bonding, leading to increased water adsorbency. Silica surfaces have hydroxyl groups that can interact with salts such as calcium chloride ions. In some embodiments the substate is sintered glass.

[0107] In some embodiments, the substrate is a clay material or an aluminosilicate material. The aluminosilicate may be a zeolite. Clays and zeolites have hydrophilic surfaces, which can adsorb salts such as calcium chloride ions through hydrogen bonding, resulting in increased water adsorbency.

[0108] In some embodiments the substrate is a carboniferous material. In some embodiments the carbon is activated carbon that is preferably functionalised with functionality (such as carboxyl (-COOH), hydroxyl (- OH), or carbonyl (-C=O) groups) that promotes absorbency of the hygroscopic material (such as the hygroscopic salt) of the invention.

[0109] In some embodiments the density of the substate may be approximately 600-1400 kg / m3; such as approximately 800-1400 kg / m3; such as approximately 900-1300 kg / m3; such as approximately 1000-1300 kg / m3.

[0110] Preferably the substrate is provided in a substantially planar form, such as in the form of a sheet and / or membrane - such as paper or card / cardboard. In some embodiments the substate in a membrane form may between about 1 to about 500 gsm; such as from 1 to 200 gsm, such as from 50 to 300 gsm, such as from 75 to 150 gsm, such as about 125 gsm.

[0111] In some embodiments the barrier properties of the substate in a membrane form are such that water vapour transmission through the moisture resistive layer is less than 50 gsm per day at 25 °C and 75% relative humidity.

[0112] In some embodiments where strength is particularly important, wet and / or dry strength additives may also be included in the substrate. For example, cationic starch can be added at 0.5-2.0 % of the paper weight for dry strength. Where used, the (for example, cationic) starch may be added separately or together with one or more components. In some embodiments, (for example, cationic) starch may be combined with the hygroscopic material and that combination of starch and the hygroscopic material added to the matrix of fibres. Without wishing to be bound by theory it is believed that adding the combination of (for example, cationic) starch and the hygroscopic material may modulate the degree of hygroscopicity of the hygroscopic material by the formation of a gel of starch and the hygroscopic material. As such, the use of starch (which is provided as a non-limiting example of a means of modulating the degree of hygroscopicity of the hygroscopic material) may be used to attenuate the performance of the composite material.

[0113] By way of further example, polyamide-epichlorohydrin resin (PAE) can be added at 0.5-2.0 % of the paper weight for wet strength, in the later case by forming covalent bonds between fibres. PVOH can used for ecofriendly applications.

[0114] Without wishing to be bound by theory, there may be additional benefits of adding materials such as PAE because the resin forms strong covalent bonds with cellulose fibres and cross-links with other components, such as calcium chloride, in the paper matrix. The addition of polyamide-epichlorohydrin (PAE) resin to paper can enhance the effectiveness of bound (such as adsorbed) calcium chloride by creating an improvement in moisture resistance and mechanical properties:

[0115] • Reduces the risk of leaching or migration of calcium chloride under humid conditions

[0116] • Provides wet strength by creating a network of water-resistant cross-links in the paper.

[0117] • Amplifies the effect of calcium chloride by maintaining the integrity of the low-humidity environment within the paper structure. That is, the calcium chloride does not migrate with the moisture gradient.

[0118] • Enables the paper to withstand repeated cycles of adsorption and desorption without significant degradation.

[0119] Alkyl ketene dimer (AKD) may also be used to enhance wet strength in the substrate. AKD is widely employed in papermaking as a hydrophobic sizing agent that enhances the resistance of cellulose fibres to water penetration, thereby contributing to improved wet strength. When applied during the wet end of the papermaking process, AKD reacts with hydroxyl groups on the cellulose surface to form covalent ester bonds, imparting a durable hydrophobic character to the fibre matrix. This chemical modification reduces fibre swelling and water absorption, which in turn stabilizes the fibre-fibre bonds under wet conditions and minimizes the loss of mechanical integrity. By limiting the disruption of hydrogen bonding within the paper structure, AKD treatment ensures that sheets retain a significant proportion of their dry strength even when exposed to moisture, making it particularly valuable for applications requiring dimensional stability and durability in humid or aqueous environments. This functional improvement has been historically believed to be critical in the development of papers intended for packaging, labelling, and other uses where wet strength is a key performance parameter. In some embodiments, AKD may be combined with the hygroscopic salt to form a combination, and that combination is added to the matrix of fibres. In some (less preferred) embodiments, AKD is added to the matrix of fibres separately to the addition of the hygroscopic salt being added to the matrix of fibres.

[0120] The second layer

[0121] As previously noted, the second layer will be selected to be at least partially, such as substantially, moisture (such as provided as water) and / or gas (such as oxygen) resistive. As such, all previously known approaches to applying moisture resistive layers are contemplated by the present invention for providing the second layer. In some case, those previously known approaches may be modified to account for the added contribution to reducing MVTR provided by the first layer including the hygroscopic material (such as the hygroscopic salt). Examples of those approaches include one or more of the following:

[0122] • surface densification by existing papermaking processes such as calendaring with a steel nip or hot soft calendaring;

[0123] • applying a membrane or membranes of any one or blends of variety of polymer layers using extrusion or laminating processes as might exist in paper converters;

[0124] • printing a layer or layers of ink or other surface treatment using processes such as might exist in paper converters; or

[0125] • applying a dispersion layer of a pigment (such as platy kaolin clay) and polymer binder using processes such as coating equipment available in on and off-machine configurations in many papermills.

[0126] Preferably the moisture (such as provided as water) and / or gas (such as oxygen) resistive layer will be applied as a polymeric layer using extrusion, lamination, or applying a dispersion layer. Dispersion coating is less expensive than extrusion coating and cost is important for packaging applications so in some cases dispersion coating is preferred. Dispersion coatings are used to create moisture (such as provided as water) and / or gas (such as oxygen) resistive layers on paper due to their adaptability, ease of application, and cost-effectiveness. Although they are easier to apply, they are prone to defects and holes due to their inability to completely fill or bridge some of the surface pores of the paper. Such disadvantages may be ameliorated or even overcome by providing a pigment (such as platy kaolin clay) in a dispersion coating to add tortuosity and / or increase "holdout" - namely the tendency of a coating not to strike into the sheet and create surface discontinuities in the form of open areas.

[0127] Advantageously, the composite material of the present invention may allow for the thickness of the moisture (such as provided as water) and / or gas (such as oxygen) resistive layer to be less than the thickness of a traditional resistive layer.

[0128] The second layer may be provided as a membrane such that:

[0129] • The membrane provides barrier properties such that water vapour transmission through the second layer is less than 300 gsm per day at 25 °C and 75% relative humidity. It is to be appreciated that lesser water vapour transmission may be desirable and water vapour transmission may be less than any of 250, 200, 150, 100, 50 or 40 gsm per day at 25 °C and 75% relative humidity. Without being limiting, it is generally true that the lesser the water vapour transmission rate at 25 °C and 75% relative humidity, the greater the barrier properties of the material (such as a packaging material or building material) and the greater the range of water sensitive produce that can be packaged using the packaging material; and / or

[0130] • The membrane provides oxygen transmission barrier properties, such that oxygen transmission through the second layer is less than 400 cm3 / m3per day at 1 atm oxygen, 25 °C and 75% relative humidity. It is to be appreciated that lesser oxygen transmission may be desirable and oxygen vapour transmission may be less than any of 300, 250, 200, 150, 100 or 50 cm3 / m3per day at 1 atm oxygen, 25 °C and 75% relative humidity. Without being limiting, it is generally true that the lesser the oxygen transmission rate at 1 atm oxygen, 25 °C and 75% relative humidity, the greater the barrier properties of the packaging material and the greater the range of oxygen sensitive produce that can be packaged using the packaging material.

[0131] The second layer may be from 1 to 500 pm in thickness, such as from 1 to 200 pm in thickness, such as from 1 to 50 pm in thickness, such as up to 30 pm in thickness. It is to be appreciated that a range of thicknesses may be suitable, depending on the application, such as the packaging or building application, and the second layer may be about 10 to about 25 pm in thickness or may be about 15 to about 20 pm in thickness.

[0132] In some embodiments the polymeric material included in the second layer is recyclable and / or biodegradable. The polymeric material may be compostable under both industrial and non-industrial conditions. One recognised non-industrial composting standard is ISO 14855-1 (2012). An example of such a biodegradable material is one that may degrade in home composting conditions where temperatures typically do not attain the temperatures found in industrial composting settings. Where used, the biodegradable polymer of the invention may be configured to undergo substantial biodegradation within 12 months of being exposed to non-industrial composting conditions. Preferably the biodegradable composition of the invention is configured to fully biodegrade within 24 months of being exposed to non-industrial composting conditions.

[0133] Polymers commonly used in extrusion coating layers on paper serve various purposes such as barrier properties, adhesion, or specific surface characteristics. Some examples of such polymers are from the following classes: polyesters, polyamides, polyurethanes, polysaccharides, proteins, polyvinyl alcohols, acrylic or styrenic polymers, polyolefins, siloxane-containing polymers, nanocomposite polymers, or inorganic-polymer hybrid barrier coatings.

[0134] More specific examples of polymers that may be included in the second layer are:

[0135] 1. Polyolefins

[0136] • Polyethylene (PE):

[0137] • Low-Density Polyethylene (LDPE): Offers good water resistance, flexibility, and adhesion to paper.

[0138] • High-Density Polyethylene (HDPE): Provides better stiffness and higher temperature resistance.

[0139] • Linear Low-Density Polyethylene (LLDPE): Enhances puncture resistance and toughness.

[0140] • Polypropylene (PP):

[0141] • Used for improved heat resistance, clarity, and rigidity compared to PE.

[0142] 2. Polyesters

[0143] • Polyethylene Terephthalate (PET):

[0144] • Provides excellent gas and moisture barriers.

[0145] • Often used for metallized layers or high-strength applications.

[0146] 3. Ethylene Copolymers

[0147] • Ethylene Vinyl Acetate (EVA):

[0148] • Adds flexibility and adhesion to difficult substrates.

[0149] • Ethylene Acrylic Acid (EAA):

[0150] • Enhances adhesion to polar substrates like paper or aluminum foil.

[0151] • Ethylene Methacrylic Acid (EMAA):

[0152] • Used for superior adhesion and seal strength. 4. Biodegradable and Compostable Polymers

[0153] • Polylactic Acid (PLA):

[0154] • A bio-based polymer used for compostable paper coatings.

[0155] • Polybutylene Succinate (PBS):

[0156] • Biodegradable, with good flexibility and toughness.

[0157] • Polyhydroxyalkanoates (PHA):

[0158] • Biopolymer for sustainable barrier applications.

[0159] 5. Barrier Polymers

[0160] • Polyvinyl Alcohol (PVOH):

[0161] • Water-soluble polymer for excellent oxygen barrier.

[0162] • Polyamide (PA):

[0163] • Used for grease resistance and mechanical strength.

[0164] 6. Other Functional Polymers

[0165] • Acrylic Coatings:

[0166] • Provides gloss and scratch resistance.

[0167] • Fluoropolymers:

[0168] • High-end barrier applications for grease or moisture resistance.

[0169] • Silicone Coatings:

[0170] • Used for release liners or non-stick surfaces.

[0171] When used, these polymers may be blended and / or combined in multilayer configurations to achieve the desired performance (e.g., LDPE for water resistance paired with PET for a gas barrier; or LDPE for water resistance paired with PVOH for a gas barrier - such as oxygen barrier). Choices depend on the end-use requirements like recyclability, sustainability, or specific performance characteristics.

[0172] More specific and / or other classes of polymeric materials that may be included in the second layer are:

[0173] • an aliphatic polyester such as: polyglycolide / polyfglycolic acid) (PGA), polycaprolactone (PCL), polydioxanone (PDO), polylactic acid (PLA) (including poly(L-lactic acid), poly(D-lactic acid), and poly(DL-lactic acid)), poly(lactic-co-glycolic acid) (PLGA), poly(trimethylene carbonate) (PTMC), polyfbutylene succinate-co-butylene adipate) (PBSA), poly(alkyl succinates), including: polyfethylene succinate) (PES), (polypropylene succinate) (PPS), polyfbutylene succinate) (PBS); polyhydroxyalkanoates (PHA), including polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO), polyhydroxydecanoate (PHD), polyhydroxy-5-phenylvalerate (PHPV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV);

[0174] • an aromatic polyester such as: poly(butylene adipate-co-terephthalate) (PBAT); • a polyamide such as BAK 1095 and BAK 2195 (based on caprolactam, butanediol, and adipic acid);

[0175] • a polyurethane that will typically include a biodegradable portion consisting of a polyester (such as PCL, PLA, and PGA);

[0176] • an agro-polymer (such as such as silk, wool, collagen);

[0177] • a polysaccharide (such as starch, hemicellulose, cellulose, chitin, chitosan, alginic acid, cellophane, pectin, pullulan, or modified forms thereof, for example cellulose acetate);

[0178] • a polypeptide / protein (such as gelatin, wheat gluten, casein, whey protein);

[0179] • a vinyl alcohol such as polyvinylalcohol (PVOH), ethylvinylalcohol (EVOH), or vinyl alcohol precursor such as poly(vinyl acetate);

[0180] • styrene-butadiene latex - such as styrene-butadiene rubber (SBR) latex;

[0181] • acrylic latex;

[0182] • polyvinylidene chloride (PVDC) latex.

[0183] Products that can be formed using the composite material of the invention include the following:

[0184] A) A compostable flexible wrap including: a first layer of cellulose matrix of fibres to which is bound calcium chloride; a second (outer) moisture resistive layer including PLA / PBAT (-70 / 30) and nanoclay blend (10-20 pm); and an optional (inner) layer including thin PVOH or protein for oxygen resistive properties.

[0185] B) A high-barrier pouch laminate including: a first layer of cellulose matrix of fibres to which is bound calcium chloride; a middle layer including MXD6 (poly(m-xylene adipamide) / nanoclay (-5-10 pm) or PEF blend; and an outer layer including PBAT I PHA (-60 / 40).

[0186] C) A dry-goods liner including: a first layer of cellulose matrix of fibres to which is bound calcium chloride; a second (outer) moisture resistive layer including relatively cheap PBS / PBAT blend; and an inner layer including gelatin / PVOH / nanoclay coated layer for oxygen resistive properties and aroma.

[0187] The present inventors have identified that PVOH is a particularly preferred polymeric material for inclusion in the second layer of the invention. While PVOH has previously been recognised as being a recyclable oxygen barrier, it has also been recognised that it loses effectiveness under high humidity conditions. Advantageously, the present invention may be utilised to combine the hygroscopic properties of, for example, calcium chloride, with the oxygen barrier properties of PVOH to provide a recyclable package having both oxygen and moisture barriers where calcium chloride provides moisture protection to both the PVOH and the contents. Other materials like PVOH that can be used in the second layer include EVOH (ethylene vinyl alcohol - a copolymer of ethylene and vinyl alcohol) and microfibrillated celluose.

[0188] A particularly preferred polymer blend for inclusion in the second layer of the invention is PVOH-LDPE.

[0189] Recyclable papers are subject to a variety of regulatory standards, depending on product type and mostly geographic location / state. Standards can either be based on the percentage of non-fiber based content or the percentage of reject material in the screen. The difference between the two variables being the allowance for water soluble polymers that filter through to waste water and are not counted toward non-fiber based content.

[0190] Standards in the U.S. are 80 / 20, where the 20% value corresponds to the non-fiber based allowance. In Europe the standard is 90 / 10, where the 10% value corresponds to the reject material from the screen. Germany has progressed through to a 95 / 5 standard. Over time it is expected that these regulations will become more stringent. While the standards are initially relatively lenient to incentivize R&D teams to begin innovating towards achievable outcomes and gain knowledge, they will soon tighten. Concurrently with increasing regulations, all existing and developing barrier chemistries follow the same line of thinking of resistance, with mechanisms such as tortuosity, density, surface energy, hydrophobicity, and so on, to inhibit moisture permeation / diffusion.

[0191] Advantageously, the present invention allows for a reduction in the non-fiber based material in the paper / packaging without a decrease in performance. Indeed, in many cases, the present invention allows an increase in performance (in moisture vapour transmission and / or oxygen transmission) while also reducing the non-fiber based material.

[0192] While previous approaches might includes coating one side of a 200-320 gsm fiber board with several polymers, tie and metalized layers to provide aseptic packaging with a polymer (non-fiber based / cellulose polymer) content of 15-25%, the present invention allows similar performance with significantly less polymer content - such as 40% less. The polymer (non-fiber based / cellulose polymer) content of the composite material of the invention may be 25% w / w or less, such as 20% w / w or less, such as 15% w / w or less, such as 10% w / w or less, such as 5% w / w or less, such as less than 5% w / w.

[0193] The second layer may be provided at any loading sufficient to modulate the transmission of moisture vapour through the composite material of the invention. Preferably, the second layer is provided at a dry loading of from 1 to 100 grams per square metre (gsm) of substrate; such as at least 1 gsm; such as at least 10 gsm, such as no more than 50 gsm, such as no more than 25 gsm; such as from 1 to 50 gsm; such as from 5 to 25 gsm, such as 5 to 15 gsm or 15 to 25 gsm. For instance, when the substrate is paper (having a weight of, for example, 80 gsm), the second layer may be provided at a dry loading of from 5 to 25 gsm. Examples of such second layers are:

[0194] • styrene-butadiene rubber (SBR) latex at from 5 to 15 gsm, such as 9 gsm, optionally provided with clay (such as kaolin clay); or

[0195] • LDPE and PVOH as a blend provided at from 15 to 25 gsm, such as 20 gsm, such as provided by 8 gsm of LDPE and 12 gsm of PVOH.

[0196] In some embodiments the moisture (such as provided as water) and / or gas (such as oxygen) resistive properties of the second layer are such that water vapour transmission through the second layer is less than 50 gsm per day at 25 °C and 75% relative humidity.

[0197] The second layer may also be provided with one or more components additional to the polymeric material. Such one or more components will typically be entrained within the polymeric material, although that should not be seen as limiting. For instance, in some embodiments, the one or more components may be provided in discrete domains within the second layer such that the polymeric material exists substantially separate to the discrete domains. Nonetheless in the more typical embodiments where the one or more components are entrained within the polymeric materials, the components will typically be provided to modify the physico-chemical properties of the second layer. For instance, the one or more components may be provided to modify the moisture (such as provided as water) and / or gas (such as oxygen) resistive properties of the second layer and / or the processability of the pre-polymeric or polymeric material used to form the second layer.

[0198] For example, it will be appreciated that in a pure polymeric material, a penetrant (such as water) may still be able to move between the polymeric strands of material in order to pass through the second layer. It has been identified that the entrainment of a solid particulate material within the polymeric material may advantageously create a more "tortured path" for the penetrant (such as water) to move through the second layer (referred to as "tortuosity"), thus adding to the moisture (such as provided as water) and / or gas (such as oxygen) resistive quality of the second layer. Such solid particulate materials may have a range of geometries, but are preferably platy (that is, having a high aspect ratio or the ratio of a particle's lateral dimensions (length and width) to its thickness). Such solid particulate materials may be formed from a range of materials, but are preferably clay. A preferred particulate material is high aspect clay. Without wishing to be bound by theory, it is believed that the resistivity of the second layer is provided in some cases as a function of the porosity (open volume) and tortuosity (how much extra distance the moisture needs to travel because of the structure of the layer. For example, platy clays that lie substantially parallel to the surface create a large lateral component to the travel distance through the layer while the polymeric material may partially or substantially fills the pores of the surface of the substrate.

[0199] Other examples of components that may be included in the second layer include: viscosity modifier; dispersant; surfactant; and / or defoamer.

[0200] Carrier

[0201] The present invention may make use of one or more carriers to disperse the hygroscopic material (such as the hygroscopic salt) and / or pre-polymeric material or polymeric material. The or each carrier will preferably be an aqueous carrier, such as water, and will disperse (such as dissolve) the hygroscopic material (such as the hygroscopic salt) and / or pre-polymeric material and / or polymeric material, such that the dispersion is capable of being applied to the material.

[0202] The properties of the carrier, such as pH and temperature, may be modified to assist with dispersing the hygroscopic material (such as the hygroscopic salt) and / or pre-polymeric material and / or polymeric material.

[0203] The physical and / or chemical nature of the carrier (such as temperature; pH; use of surfactants, dispersing agents, and / or flocculants) may be adjusted to modulate the dispersion (such as solubility) or other properties of the hygroscopic material (such as the hygroscopic salt) and / or pre-polymeric material and / or polymeric material being carried therein. For instance, it will be appreciated that the size of any included platy particles being entrained in the polymeric material may lead to agglomeration which may or may not be desired. By adjusting the physical and / or chemical nature of the carrier the desired dispersion of the platy particles may be achieved.

[0204] Additional Layer(s)

[0205] In some embodiments the composite material of the invention (such as the packaging material) may be provided with one or more layers additional to the first layer and the second layer. Such additional layer(s) of material may be provided to the substrate before or after the hygroscopic material (such as the hygroscopic salt) is included in the substrate provided on the material. An additional layer may be provided as a membrane such that:

[0206] • The membrane provides barrier properties such that water vapour transmission through the additional layer is less than 300 gsm per day at 25 °C and 75% relative humidity. It is to be appreciated that lesser water vapour transmission may be desirable and water vapour transmission may be less than any of 250, 200, 150, 100, 50 or 40 gsm per day at 25 °C and 75% relative humidity. Without being limiting, it is generally true that the lesser the water vapour transmission rate at 25 °C and 75% relative humidity, the greater the barrier properties of the material (such as a packaging material or building material) and the greater the range of water sensitive produce that can be packaged using the packaging material; and / or

[0207] • The membrane provides oxygen transmission barrier properties, such that oxygen transmission through the second layer is less than 400 cm3 / m3per day at 1 atm oxygen, 25 °C and 75% relative humidity. It is to be appreciated that lesser oxygen transmission may be desirable and oxygen vapour transmission may be less than any of 300, 250, 200, 150, 100 or 50 cm3 / m3per day at 1 atm oxygen, 25 °C and 75% relative humidity. Without being limiting, it is generally true that the lesser the oxygen transmission rate at 1 atm oxygen, 25 °C and 75% relative humidity, the greater the barrier properties of the packaging material and the greater the range of oxygen sensitive produce that can be packaged using the packaging material.

[0208] In some embodiments, the or each additional layer may be independently selected from being from 1 to 500 pm in thickness, such as from 1 to 200 pm in thickness, such as from 1 to 50 pm in thickness, such as up to 30 pm in thickness. It is to be appreciated that a range of thicknesses may be suitable, depending on the application, such as the packaging or building application, and the or each additional layer may be about 10 to about 25 pm in thickness or may be about 15 to about 20 pm in thickness.

[0209] In some embodiments, the or each additional layer may include (such as substantially formed from) polymeric material. The polymeric material may be a biological polymer or a synthetic polymer although blends of biological and synthetic polymers are also contemplated.

[0210] Where present, any additional layer(s) of polymeric material is preferably provided at an extremity of the composite material, rather than being interposed (sandwiched) between the outer extremity layers of the material. By positioning any additional layer(s) of polymeric material (such as a biodegradable polymer) at an extremity it may be allowed to contact a packaged product such as food, for example. When used in a package, such an extremity may be internal to the package. Such a polymer may have a thickness of the order of less than 50 microns, such as less than 20 microns, such as about 5 to 10 microns. In some embodiments the polymer is biodegradable and / or recyclable. In some cases such polymers are expensive which might rule them out as being suitable for packaging. Advantageously, the present invention enables a reduction in the amount of polymeric material needed to provide the same or greater moisture resistance and / or oxygen permeability, thus making some polymers cost effective that would not otherwise be cost effective.

[0211] In some embodiments the polymer is compostable under both industrial and non-industrial conditions. One recognised non-industrial composting standard is ISO 14855-1 (2012). An example of such a biodegradable material is one that may degrade in home composting conditions where temperatures typically do not attain the temperatures found in industrial composting settings. Preferably the biodegradable polymer of the invention is configured to undergo substantial biodegradation within 12 months of being exposed to non-industrial composting conditions. Preferably the biodegradable composition of the invention is configured to fully biodegrade within 24 months of being exposed to non-industrial composting conditions.

[0212] The polymer may be selected from:

[0213] • an aliphatic polyester such as: polyglycolide / poly(glycolic acid) (PGA), polycaprolactone (PCL), polydioxanone (PDO), polylactic acid (PLA) (including poly(L-lactic acid), poly(D-lactic acid), and poly(DL-lactic acid)), poly(lactic-co-glycolic acid) (PLGA), poly(trimethylene carbonate) (PTMC), poly(butylene succinate-co-butylene adipate) (PBSA), poly(alkyl succinates), including: polyethylene succinate) (PES), (polypropylene succinate) (PPS), poly(butylene succinate) (PBS); polyhydroxyalkanoates (PHA), including polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO), polyhydroxydecanoate (PHD), polyhydroxy-5-phenylvalerate (PHPV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV);

[0214] • an aromatic polyester such as: poly(butylene adipate-co-terephthalate) (PBAT);

[0215] • a polyamide such as BAK 1095 and BAK 2195 (based on caprolactam, butanediol, and adipic acid);

[0216] • a polyurethane that will typically include a biodegradable portion consisting of a polyester (such as PCL, PLA, and PGA);

[0217] • an agro-polymer (such as such as silk, wool, collagen);

[0218] • a polysaccharide (such as starch, hemicellulose, cellulose, chitin, chitosan, alginic acid, cellophane, pectin, pullulan, or modified forms thereof, for example cellulose acetate);

[0219] • a polypeptide (such as gelatin, wheat gluten, casein, whey protein); • a vinyl alcohol such as polyvinylalcohol (PVOH), ethylvinylalcohol, or vinyl alcohol precursor such as poly(vinyl acetate).

[0220] A particularly preferred polymeric material for use as an oxygen barrier in an additional layer of the invention is polyvinylalcohol (PVOH).

[0221] In some embodiments the barrier properties of at least one additional layer is such that water vapour transmission through the additional layer is less than 50 gsm per day at 25 degrees C and 75% relative humidity.

[0222] The additional layer may be provided at any loading sufficient to modulate the transmission of moisture vapour through the composite material of the invention. Preferably, the additional layer is provided at a dry loading of from 1 to 100 grams per square metre (gsm) of substrate; such as at least 1 gsm, such as at least 5 gsm; such as at least 10 gsm, such as no more than 50 gsm, such as no more than 25 gsm, such as from 1 to 50 gsm; such as from 5 to 25 gsm, such as 5 to 15 gsm or 15 to 25 gsm. For instance, when the substrate is paper (having a weight of, for example, 80 gsm), the additional layer may be provided at a dry loading of from 5 to 25 gsm. Examples of such an additional layer is: LDPE and PVOH as a blend provided at from 15 to 25 gsm, such as 20 gsm, such as provided by 8 gsm of LDPE and 12 gsm of PVOH.

[0223] Additional Additive(s)

[0224] The matrix of fibres and / or the polymeric material may include one or more additional additives. For instance, the matrix of fibres may include a phyllosilicate and / or cellulosic particle and / or water insoluble (or poorly soluble) hygroscopic material (such as hygroscopic salt). Such inclusion(s) may be retained within the matrix of fibres.

[0225] In some embodiments the cellulosic particle is selected from the group consisting of: a micro -fibril lated cellulose, microcrystalline cellulose, and nano-structured cellulose, and combinations thereof.

[0226] In some embodiments the matrix of fibres may include a water insoluble (or poorly soluble) hygroscopic salt. An example of an insoluble hygroscopic salt which may be used in the present invention is calcium sulfate (hemihydrate and / or dihydrate, preferably hemihydrate). The water insoluble (or poorly soluble) hygroscopic salt may be entrained within the matrix of fibres. It has been discovered that the use of a phyllosilicate mineral applied to a matrix of fibres provides a decreased moisture vapour transmission rate compared with the same material that lacks the phyllosilicate mineral.

[0227] It has been discovered that the use of a cellulosic particle (selected from the group consisting of: a micro- fibrillated cellulose, microcrystalline cellulose, and nano-structured cellulose, and combinations thereof) applied to a matrix of fibres provides a decreased moisture vapour transmission rate compared with the same matrix that lacks the particle.

[0228] However, it has been further discovered that the combined use of any two or more - preferably all three - of the hygroscopic material (such as the hygroscopic salt), phyllosilicate mineral, and cellulosic particle applied to a material so that the hygroscopic material (such as the hygroscopic salt) is bound (such as adsorbed) to the matrix of fibres provides a decreased moisture vapour transmission rate compared with the same matrix without that combination. In some embodiments the use of any two or more, or all three of the components provides a synergistic decrease in the moisture vapour transmission rate compared with the same matrix without that combination in a manner that could not have been contemplated based merely on an additive effect.

[0229] Without wishing to be bound by theory, it is believed that the hygroscopic material (such as the hygroscopic salt) functions to adsorb water, while the phyllosilicate mineral and cellulosic particle not only decrease the moisture transmission rate themselves but synergistically assist with dispersing the hygroscopic material (such as the hygroscopic salt) across the matrix.

[0230] Phyllosilicates

[0231] The phyllosilicate that may be used in the present invention is a sheet silicate mineral, or a combination of different phyllosilicates. Examples of suitable phyllosilicates are a serpentine, a clay, or a mica mineral. Preferably the phyllosilicate is a clay or a mica mineral. Examples of suitable clays include a halloysite, kaolinite (kaolin), a pyrophyllite, talc, illite, smectite (such as a montmorillonite mineral), chlorite, vermiculite, sepiolite, or a palygorskite (attapulgite) mineral. Examples of suitable mica minerals include a biotite, fuchsite, muscovite, phlogopite, lepidolite, margarite, or a glauconite mineral. Examples of suitable serpentine minerals are an antigorite, chrysotile, or a lizardite mineral. Preferably the phyllosilicate is selected from a kaolinite (such as red kalonite, such as kaolin), talc, illite (such as red illite, or green French clay), or a bentonite (such as red bentonite). Bentonite is particularly useful in the present invention since its availability is widespread, it is relatively inexpensive, and it performs well. Without wishing to be bound by theory, it is believed that the phyllosilicate may be included (such as entrained) within the matrix (such as within pores within the matrix). It is believed that the phyllosilicates are likely to form agglomerations in combination with the hygroscopic water soluble salt (such as calcium chloride) acting as a flocculation agent. This working theory is based on the observation that there is a significant increase in the viscosity of a composition of the hygroscopic water soluble salt and the phyllosilicate in solution, compared with a solution of the hygroscopic water soluble salt alone. It is theorised that the phyllosilicates are an agent of agglomeration.

[0232] Cellulosic Particle

[0233] The cellulosic particle may be cellulose or a modified cellulose (such as cellulose acetate) and may contain a mixture of cellulose / modified cellulose with other material(s). The cellulosic particle may be derived from any source of material including both naturally occurring and synthetic / semi-synthetic sources (including synthetic biology sources).

[0234] The cellulosic particle is preferably selected from micro -fibril lated cellulose, microcrystalline cellulose, and nano-structured cellulose, and combinations thereof. These forms of cellulose may be formed by treating cellulose in a range of different ways, including by applying shear, reactive extrusion, enzyme mediated hydrolysis, mechanical grinding, ultrasonication, steam explosion, and acid hydrolysis.

[0235] The cellulosic particle can be entrained within the matrix. This ability will generally be related to the size of the pores that may be found in the matrix, such that the size of the cellulosic particle will be smaller than the size of the pores. For example, the size of the cellulosic particle may be less than 0.1 pm, or from 0.1 to 1 pm, or from 0.1 to 20 pm, or from 0.01 to 200 pm, or from 0.1 to 400 pm. While the cellulosic particle of the invention is described with reference that it "can be entrained within the matrix", it may equally be the case that the cellulosic particle of the invention is actually entrained within the matrix where the cellulosic particle and the matrix have been placed in contact with eachother.

[0236] For illustrative purposes only, it is worthwhile discussing the entrainment of cellulosic particles within the matrix of fibres provided in office paper. Such a matrix may be considered to provide pores as the interstitial space between the fibres in the matrix. The average pore size in a sheet of office paper typically ranges from about 10 to 100 micrometres (pm) in diameter, such as from 10 to 50 micrometres (pm) in diameter. This range can vary depending on the specific type of office paper, its manufacturing process, and the intended use. In some embodiments it may be beneficial to use a flocculating agent where cellulosic particles having a size of less than 1 pm are used, so that the cellulosic particles are retained within the pores. One such flocculating agent that may be used is calcium cations. For example, micro- fibrillated cellulose particles (and some phyllosilicates such as bentonite) and have net negative surface charges. When calcium ions are brought into contact with such a charged surface, particularly when both are dispersed in a carrier, they are attracted to the negatively charged surfaces of these particles causing them to flocculate.

[0237] Without wishing to be bound by theory, it is believed that the cellulosic particle may be included (such as entrained) within the matrix of the material (such as within pores within the material) and / or assist with the dispersion of the hygroscopic material (such as the hygroscopic salt) where the components are used in combination. In particular, it is believed that the hygroscopic material (such as the hygroscopic salt) can also adsorb to the surface of the cellulosic particle.

[0238] Method of Application to Substrate

[0239] For application to the substrate, generally the hygroscopic material (such as the hygroscopic salt) will be dispersed (such as dissolved) in one or more carriers (such as an aqueous carrier, such as water) and the dispersion (such as solution) will be applied to the substrate. Most existing technologies for applying surface treatments to paper are suitable to apply the compositions of the present invention. These include, size presses, short and long dwell coaters, slot coaters, spray coaters, etc.

[0240] The hygroscopic salt (where used) of the present invention is preferably provided as a salt of calcium, lithium, zinc, or aluminium. In each case, but especially so for calcium, zinc, and aluminium, it can be difficult to optimally apply the salt to the material especially when the material is cellulose. Without wishing to be bound by theory, and by way of example, it is believed to be especially challenging to apply calcium chloride to a cellulose paper because the hydroxyl groups have a strong affinity to the cation, which coincidentally is why some of the composite materials of the invention have been shown to be so effective in decreasing the transmission of moisture through the material.

[0241] The present invention can overcome any such challenge particularly when the method of application makes use of a pressure gradient to encourage the hygroscopic material (such as the hygroscopic salt) / carrier onto / into the material. In some examples, such a pressure gradient may be provided by a pressure pulse which could be thought of as a positive pressure gradient. The pressure pulse may be provided by a blade or pressure roll coater (such as a size press) which can form a pressure pulse as the paper passes through the nip between them and a backing roll. Another mechanism for overcoming any such challenge is to use a negative pressure gradient such as may be provided by a vacuum to draw the hygroscopic material (such as the hygroscopic salt) / ca rrier into the material.

[0242] The same, or a different, method of application may be repeated for successive applications of the hygroscopic material (such as the hygroscopic salt) / ca rrier to the substrate.

[0243] The quantity of the hygroscopic material (such as the hygroscopic salt) that may be applied to the substrate may depend on the intended purpose or application of the composite material so formed. It may be convenient to refer to the amount of the hygroscopic material (such as the hygroscopic salt) that is applied with reference to its dry weight per unit surface area of the substrate. For instance, from 1 to 500 gsm may be applied to the material, such as from 1 to 200 gsm, such as from 5 to 100 gsm. The quantity may be applied in a single application step, or a plurality of application steps. The or each application step may apply from 1 to 100 gsm to the material, such as from 1 to 50 gsm, such as from 1 to 25 gsm, such as from 5 to 25 gsm, such as from 10 to 25 gsm.

[0244] Where used, the quantity of the phyllosilicate mineral that may be applied to the material may depend on the intended purpose or application of the material so formed. It may be convenient to refer to the amount of the phyllosilicate mineral (where used) that is applied with reference to its dry weight per unit surface area of the material. For instance, from 1 to 500 gsm may be applied to the material, such as from 1 to 200 gsm, such as from 1 to 100 gsm, such as from 5 to 100 gsm. The quantity may be applied in a single application step, or a plurality of application steps. The or each application step may apply from 1 to 100 gsm to the material, such as from 1 to 50 gsm, such as from 1 to 25 gsm, such as from 5 to 25 gsm, such as from 10 to 25 gsm.

[0245] Where used, the quantity of the cellulosic particle (where used) that may be applied to the material may depend on the intended purpose or application of the material so formed. It may be convenient to refer to the amount of the cellulosic particle (where used)) that is applied with reference to its dry weight per unit surface area of the material. For instance, from 1 to 500 gsm may be applied to the material, such as from 1 to 200 gsm, such as from 1 to 100 gsm, such as from 5 to 100 gsm. The quantity may be applied in a single application step, or a plurality of application steps. The or each application step may apply from 1 to 100 gsm to the material, such as from 1 to 50 gsm, such as from 1 to 25 gsm, such as from 5 to 25 gsm, such as from 10 to 25 gsm. An application rate of from 1 to 25 gsm, such as from 5 to 25 gsm, such as from 10 to 25 gsm per application step is believed to be particularly beneficial to materials such as cellulose, or modified cellulose, such as paper, card or cardboard having a weight of about 125 gsm.

[0246] Without wishing to be bound by theory, it is believed that the hygroscopic material (such as the hygroscopic salt) is bound (such as adsorbed) into the crystalline and amorphous cellulose presented at the surfaces of the fibres and their internal structure of fibrils and microfibrils of the matrix of the material - for example, the cation of a hygroscopic salt may bond to the cellulose. Without wishing to be bound by theory, where used it is believed that the phyllosilicate mineral, and / or cellulosic particle are retained by a combination of filtration and the flocculating effect of the cation of the hygroscopic salt - which effect is referred to herein as being "entrained" within the matrix. For instance, the cellulosic particles and / or phyllosilicates may be considered to be of the same charge as the matrix of fibres wherein the fibres are cellulosic. In such a case, the presence of a hygroscopic salt, such as calcium chloride (particularly the calcium cations) will provide somewhat of a bridge between the fibres and the cellulosic particles and / or phyllosilicates. It is believed that this mechanism of adsorbency / adherency leads to maximal dispersal of the hygroscopic salt (in particular) across the material and hence maximising pickup of the active ingredients and the consequent maximal reduction in moisture transmission across the material.

[0247] As opposed to adsorbency, absorbency involves the substance being drawn into and held within the internal structure of the material such as within pores of the matrix. Absorbance is likely the predominant mechanism for retaining the particulate components of the treatment, particularly in an agglomerated form.

[0248] Method of Application of Second Layer

[0249] The moisture (such as provided as water) and / or gas (such as oxygen) resistive second layer that is bonded to the first layer may be achieved by using any one of a number of techniques, including one or more of the following:

[0250] • surface densification by existing papermaking processes such as calendaring with a steel nip or hot soft calendaring;

[0251] • applying a membrane of any one or blends of variety of polymer layers using extrusion or laminating processes as might exist in paper converters;

[0252] • printing a layer of ink or other surface treatment using processes such as might exist in paper converters; or • applying a dispersion layer of a pigment (such as platy kaolin clay) and polymer binder using processes such as coating equipment available in on and off-machine configurations in many papermills.

[0253] Orientation of the first and second iayers

[0254] At its most basic, the composite material of the present invention provides a first layer (substrate layer) and a second layer (resistive layer) and hence may be asymmetric across the material. To the extent that the composite material may be used to partition one environment (eg more humid) from a second environment (eg less humid), such an asymmetric composite material may be described as having an orientation with respect to the two environments.

[0255] For instance, the resistive layer may be proximal to the more humid environment and distal to the less humid environment. In turn the substrate layer may be proximal to the less humid environment and distal to the more humid environment. Without limitation, this orientation may be (and generally are) preferred where heavier "upstream" (gradient) resistance is desired, and is provided by the resistive properties of the second layer, and will generally provide the greatest synergistic benefit with the hygroscopic material in the first layer.

[0256] Conversely the orientation may be reversed. All such orientations of the composite material of the present invention are contemplated and may be adapted depending on the desired outcome. Without limitation, this orientation may be preferred where lower "upstream" (gradient) resistance is desired, such as in packages that are subject to spikes in the relative humidity in the external environment such as might occur during transit in a supply chain rather than in a steady state external environment. Specifically, and without wishing to be bound by theory, it is believed that the absorption / desorption properties of the first layer hygroscopic material are able to effectively attenuate the spikes in relative humidity to modulate the effects of those spikes on the composite material and / or contents of any such package made using the composite material.

[0257] The effect of orientation on MVTR is described below and shown in Figures 4 to 7. Applications & Advantages

[0258] The composite material of the present invention may be used in a myriad of packaging applications where the packaged product or the package itself is susceptible to damage from moisture and / or oxygen.

[0259] Examples of such packaged products include:

[0260] • Electronics and Electronic Components

[0261] • Pharmaceuticals

[0262] • Foodstuffs, such as powdered milk, coffee, or powdered supplements

[0263] • Liquid foods - such as milk and juice

[0264] • Certain textiles and fabrics, especially those prone to mildew or mould growth

[0265] • Certain types of paper, such as copy paper

[0266] • Powdered and granular materials, such as cement, pet foods, fertilisers

[0267] Examples of food packaging applications include:

[0268] • Flexible wraps and stand-up pouches that are re-sealable and come in a range of sizes;

[0269] • Rigid packaging such as takeaway coffee cups, containers of chilled or frozen dairy products, and bowls and trays manufactured through pressing or vacuum forming; and

[0270] • Rigid packaging such as 3D pulp containers manufactured through traditional pulping methods with thermoformed polymer layer.

[0271] • Paperboard packaging used for liquid foods which can be weakened by prolonged exposure to moisture during distribution and use.

[0272] • Secondary packaging, such as corrugated boxes, which can be weakened by prolonged exposure to cyclic humidity during distribution and fail to protect their contents form mechanical damage.

[0273] • Multiwall paper sacks which need to be strong enough to carry their contents safely in moist environments

[0274] Without wishing to be bound by theory, the composite material of the present is believed to provide a cost effective alternative or complement to expensive barrier materials, in some cases extending the application of known barrier materials.

[0275] Where the composite material is used to form a building material, it may be used in a myriad of building applications where it is desirable to reduce the transmission of moisture and / or oxygen from one side of the material to the other side of the material. For instance, the material may be used to control humidity within buildings by installing wallboards and / or ceiling tiles treated with the hygroscopic material (such as the hygroscopic salt) and the polymeric material. The addition of these components could enhance the wallboard's ability to absorb moisture from the surrounding environment. This property might be advantageous in certain applications, such as controlling humidity in indoor spaces during periods of cyclic diurnal humidity.

[0276] The building material of the present invention may also be used as a sink / source of moisture such that it absorbs moisture under humid conditions and releases moisture under dry conditions so as to modulate the humidity in an environment.

[0277] Solely for legal purposes during the prosecution of this patent application, so as to avoid collision with any other patent application filed by the applicant, it may be preferable to disclaim the specific composite materials (and their methods of manufacture) of any of the materials in examples 1, 2, and / or 3.

[0278] Examples

[0279] Controls: Kraft cellulose-fibre material - negative control; and Kraft cellulose-fibre material coated with a polymeric layer of PH A (25 gsm) - positive control

[0280] Uncoated highly porous kraft cellulose-fibre material (125 gram per square meter) was measured to have a water vapour transmission rate (WVTR) of 3000 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity). For this material, this WVTR represents a negative control.

[0281] For a positive control, to be used as a reference for how the product of the present invention provides a useful alternative and believed to overcome some problems associated with using a barrier layer, a polymeric coating of polyhydroxyalkanoates (PHA) (25 gram per square meter, 20 micron) was applied directly to a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) with a compostable adhesive by air atomizing spray nozzle. The adhesive used was sourced from a compostable laminating adhesive sold by Scitech Adhesive Systems as ST6093G HS.

[0282] It was found with this positive control provided an average water vapour transmission rate of 115 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity). The oxygen transmission rate of this packaging material was also measured and the average was calculated as 400 cm3 / m2 / 24hr. Comparative Example 1 - Kraft cellulose-fibre material coated with calcium chloride (15.8 gsm)

[0283] In this example a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a solution of calcium chloride, which was then dried to provide on a dry weight basis a 15.8 grams per square meter coating of calcium chloride. The coating was applied in a 50 wt% solids solution after dissolving in deionized water. It was found with this example that the average water vapour transmission rate was reduced to 217 g / m2 / day (measured at 25 degrees Celsius and at 75% relative humidity), a very significant reduction from a water vapour transmission rate of 3000 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity) for the uncoated highly porous kraft cellulose-fibre material (125 gram per square meter).

[0284] Comparative Example 2 - Kraft cellulose-fibre material coated with calcium chloride (63.3 gsm)

[0285] In this example a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a solution of calcium chloride, which was then dried to provide on a dry weight basis a 63.3 grams per square meter coating of calcium chloride. The coating was applied in a 50 wt% solids solution after dissolving in deionized water. It was found with this example that the average water vapour transmission rate was reduced to 255 g / m2 / day (measured at 25 degrees Celsius and at 75% relative humidity), a very significant reduction from a water vapour transmission rate of 3000 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity) for the uncoated highly porous kraft cellulose-fibre material (125 gram per square meter). It was interesting to note that a fourfold increase in the dry weight of the calcium chloride over that tested in Example 5 did not lead to any further decrease in the water vapour transmission rate.

[0286] Comparative Example 3 - Kraft cellulose-fibre material coated with bentonite clay (11.67 gsm), calcium chloride (15.83 gsm), and microfibrillated cellulose and bentonite clay (4.31 gsm)

[0287] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of bentonite clay which was then dried to provide on a dry weight basis a 11 .67 grams per square meter coating of bentonite clay. A solution of calcium chloride was then spray coated directly by air atomizing spray nozzle onto the bentonite clay coated material and then dried to provide on a dry weight basis a 15.83 grams per square meter coating of calcium chloride. A dispersion of 6 wt% bentonite clay and 1.5 wt% microfibrillated cellulose was then spray coated directly by air atomizing spray nozzle onto the bentonite clay and calcium chloride coated material and then dried to provide on a dry weight basis a 4.31 grams per square meter coating of bentonite clay and microfibrillated cellulose.

[0288] It was found with this example that the average water vapour transmission rate was 1223 g / m2 / day (measured at 25 degrees Celsius and at 75% relative humidity), a reduction from a water vapour transmission rate of 3000 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity) for the uncoated highly porous kraft cellu lose-fibre material (125 gram per square meter).

[0289] Example 1 - Kraft cellu lose -fibre material coated with calcium chloride (15.83 gsm), and a polymeric layer of polyhydroxybutyrate (20 gsm)

[0290] In this example, a sheet of highly porous kraft cel lulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a solution of calcium chloride and then dried to provide on a dry weight basis a 15.83 grams per square meter coating of calcium chloride. Two polymeric coatings of polyhydroxybutyrate (PHB) (applied sequentially, for a total of 20 gram per square meter, 20 micron) were applied directly by air atomizing spray nozzle to the coated material with a compostable adhesive. The adhesive used was sourced from a compostable laminating adhesive sold by Scitech Adhesive Systems as ST6093G HS.

[0291] It was found with this example that the average water vapour transmission rate was 31 g / m2 / day (measured at 25 degrees Celsius and at 75% relative humidity), a reduction from a water vapour transmission rate of 3000 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity) for the uncoated highly porous kraft cellulose-fibre material (125 gram per square meter). The oxygen transmission rate of this packaging material was also measured and the average was calculated as 253 cm3 / m2 / 24hr.

[0292] Example 2 - Kraft cellulose-fibre material coated with calcium chloride (15.83 gsm), bentonite clay and microfibrillated cellulose (12.93 gsm), and a polymeric layer of polyhydroxybutyrate (20 gsm)

[0293] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a solution of calcium chloride and then dried to provide on a dry weight basis a 15.83 grams per square meter coating of calcium chloride. A dispersion of 6 wt% bentonite clay and 1.5 wt% microfibrillated cellulose was then spray coated directly by air atomizing spray nozzle onto the calcium chloride coated material and then dried (the process of spray coating and drying completed three more times) to provide on a dry weight basis a 12.93 grams per square meter coating of bentonite clay and microfibril lated cellulose. A polymeric coating of polyhydroxybutyrate (PHB) (20 gram per square meter, 20 micron) was then applied directly by air atomizing spray nozzle to the coated material with a compostable adhesive. The adhesive used was sourced from a compostable laminating adhesive sold by Scitech Adhesive Systems as ST6093G HS.

[0294] It was found with this example that the average water vapour transmission rate was 33 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity), a reduction from a water vapour transmission rate of 3000 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity) for the uncoated highly porous kraft cel I ulose-fibre material (125 gram per square meter). The oxygen transmission rate of this packaging material was also measured and the average was calculated as 287 cm3 / m2 / 24hr.

[0295] Example 3 - Kraft cellulose -fibre material coated with bentonite clay (11.67 gsm), calcium chloride (15.83 gsm), microfibrillated cellulose and bentonite clay (4.31 gsm), and a polymeric layer of PH A

[0296] In this example, a sheet of highly porous kraft cel lulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of bentonite clay which was then dried to provide on a dry weight basis a 11 .67 grams per square meter coating of bentonite clay. A solution of calcium chloride was then spray coated directly by air atomizing spray nozzle onto the bentonite clay coated material and then dried to provide on a dry weight basis a 15.83 grams per square meter coating of calcium chloride. A dispersion of 6 wt% bentonite clay and 1.5 wt% microfibrillated cellulose was then spray coated directly by air atomizing spray nozzle onto the bentonite clay and calcium chloride coated material and then dried to provide on a dry weight basis a 4.31 grams per square meter coating of bentonite clay and microfibrillated cellulose. This example differed from Example 1 in that a polymeric coating of PHA (25 gram per square meter, 20 micron) was then applied directly to the coated material with a compostable adhesive. The adhesive used was sourced from a compostable laminating adhesive sold by Scitech Adhesive Systems as ST6093G HS.

[0297] It was found with this example that the average water vapour transmission rate was 62 g / m2 / day (measured at 25 degrees Celsius and at 75% relative humidity), a reduction from a water vapour transmission rate of 3000 g / m2 / 24hr (measured at 25 degrees Celsius and at 75% relative humidity) for the uncoated highly porous kraft cellu lose-fibre material (125 gram per square meter). The oxygen transmission rate of this packaging material was also measured and the average was calculated as 747 cm3 / m2 / 24hr.

[0298] As illustrated in Table 1, the water vapour transmission test results show that coating with calcium chloride and a polymeric material (examples 1 to 3) provides excellent barrier properties against water vapour permeation through the coating. This effect is significantly better than the effect of using either a polymeric material alone (negative control 2) or calcium chloride alone (comparative examples 1 and 2), and is synergistic. This result is even more remarkable considering that the PHBV used in Example 1 is lower weight and many times more conductive to moisture than PHA making the four fold reduction due to the addition of calcium chloride even more remarkable.

[0299] Table 1

[0300] Water Holding Capacity

[0301] Further coatings were investigated to evaluate the effect of different salts and phyllosilicates on the water holding capacity of the coating with microfibrillated cellulose. The average water holding capacity per coating weight of the examples B1 -B14 is illustrated in Fig. 1. Without wishing to be bound by theory, the water holding capacity may be considered to be the practical result stemming from the theory of capacitance that has been proposed - namely the ability of the hygroscopic material (such as the hygroscopic salt), and optional additives, to retain water before wetting out and allowing a significant proportion of the environmental moisture to affect the contents of a package, by way of example.

[0302] Example Bl - Kraft cellulose -fibre material coated with microfibrillated cellulose, red bentonite clay, and subjected to a 50 wt% solution of calcium chloride

[0303] In this example, a sheet of highly porous kraft cel lulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose and 7.7 wt% red bentonite clay. Once dry, the coated material was spray coated directly by air atomizing spray nozzle with a 50 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1499.7 kg / m3(measured at 25 degrees Celsius).

[0304] Example B2 - Kraft cellulose-fibre material coated with microfibrillated cellulose, red kaolin clay, and subjected to a 50 wt% solution of calcium chloride

[0305] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose, and 11.6 wt% red kaolin clay, and then dried. The coated material was spray coated directly by air atomizing spray nozzle with a 50 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1422.5 kg / m3(measured at 25 degrees Celsius).

[0306] Example B3 - Kraft cellulose-fibre material coated with microfibrillated cellulose, talc, and subjected to a 50 wt% solution of calcium chloride

[0307] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose and 7.9 wt% talc, and dried. The coated material was spray coated directly with a 50 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1493.8 kg / m3(measured at 25 degrees Celsius). Example B4 - Kraft cellulose-ftbre material coated with microftbrlllated cellulose, red illite clay, and subjected to a 50 wt% solution of calcium chloride

[0308] In this example, a sheet of highly porous kraft cel lulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% m icrofi bril lated cellulose, and 6.99 wt% red illite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a 50 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1622.0 kg / m3(measured at 25 degrees Celsius).

[0309] Example B5 - Kraft cellulose-ftbre material coated with microftbrlllated cellulose, Ben Red and subjected to a 50 wt% solution of calcium chloride

[0310] In this example, a sheet of highly porous kraft cel lulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% m icrofi bril lated cellulose, and 7.7 wt% Ben Red, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a 50 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1382.5 kg / m3(measured at 25 degrees Celsius).

[0311] Example B6- Kraft cellulose-ftbre material coated with microftbrlllated cellulose, red bentonite clay and subjected to a 40 wt% solution of calcium chloride

[0312] In this example, a sheet of highly porous kraft cel lulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% m icrofi bril lated cellulose, and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a 40 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1249.7 kg / m3(measured at 25 degrees Celsius).

[0313] Example B7- Kraft cellulose-ftbre material coated with microftbrlllated cellulose, red bentonite clay and subjected to a 45 wt% solution of calcium chloride

[0314] In this example, a sheet of highly porous kraft cel lulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% m icrofi bril lated cellulose, and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a 45 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1370.3 kg / m3(measured at 25 degrees Celsius). Example B8 - Kraft cellulose-fibre material coated with microftbrillated cellulose, red bentonite clay and subjected to a 20 wt% solution of calcium chloride

[0315] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% m icrofi bril lated cellulose, and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a 20 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1189.5 kg / m3(measured at 25 degrees Celsius).

[0316] Example B9 - Kraft cellulose-fibre material coated with microftbrillated cellulose, red bentonite clay and subjected to a 15 wt% solution of calcium chloride

[0317] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% m icrofi bril lated cellulose, and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a 15 wt% solution of calcium chloride in deionized water, and dried. It was found with this example that the average water holding capacity was 1152.1 kg / m3(measured at 25 degrees Celsius).

[0318] Example BIO - Kraft cellulose-fibre material coated with microfibrillated cellulose, red bentonite clay and subjected to a solution of 45 wt% calcium chloride and 5wt % wt magnesium sulfate

[0319] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose, and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a solution of 45 wt% calcium chloride and 5 wt% magnesium sulfate in deionized water, and dried. It was found with this example that the average water holding capacity was 1231.7 kg / m3(measured at 25 degrees Celsius).

[0320] Example B11 - Kraft cellulose-fibre material coated with microfibrillated cellulose, red bentonite clay and subjected to a solution of 35 wt% calcium chloride and 15 wt% magnesium sulfate

[0321] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a solution of 35 wt% calcium chloride and 15 wt% magnesium sulfate in deionized water, and dried.

[0322] It was found with this example that the average water holding capacity was 842.5 kg / m3(measured at 25 degrees Celsius).

[0323] Example Bl 2 - Kraft cellulose-fibre material coated with microfibrillated cellulose, red bentonite clay and subjected to a solution of 25 wt% calcium chloride and 25 wt% magnesium sulfate

[0324] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a solution of 25 wt% calcium chloride and 25% wt magnesium sulfate in deionized water, and dried. It was found with this example that the average water holding capacity was 845.7 kg / m3(measured at 25 degrees Celsius).

[0325] Example Bl 3 - Kraft cellulose-fibre material coated with microfibrillated cellulose, red bentonite clay and subjected to a solution of 15 wt% calcium chloride and 35 wt% magnesium sulfate

[0326] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose, 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a solution of 15 wt% calcium chloride and 35% wt magnesium sulfate in deionized water, and dried. It was found with this example that the average water holding capacity was 606.2 kg / m3(measured at 25 degrees Celsius).

[0327] Example Bl 4 - Kraft cellulose-fibre material coated with microfibrillated cellulose, red bentonite clay and subjected to a solution of 5 wt% calcium chloride and 45 wt% magnesium sulfate

[0328] In this example, a sheet of highly porous kraft cellulose-fibre material (125 gram per square meter) was spray coated directly by air atomizing spray nozzle with a dispersion of 1 .5 wt% microfibrillated cellulose and 7.7 wt% red bentonite clay, and dried. The coated material was spray coated directly by air atomizing spray nozzle with a solution of 5 wt% calcium chloride and 45 wt% magnesium sulfate in deionized water, and dried. It was found with this example that the average water holding capacity was 715.0 kg / m3(measured at 25 degrees Celsius).

[0329] Water Holding Efficiency

[0330] The effect of the concentration of calcium chloride content on the water holding capacity of the coatings comprising microfibrillated cellulose, and both bentonite and microfibrillated cellulose was evaluated.

[0331] Example Cl - Kraft cellulose-fibre material coated with microfibrillated cellulose and subjected to a calcium chloride treatment

[0332] In this example, five sheets of highly porous kraft cellulose-fibre material (125 gram per square meter) were spray coated directly with a dispersion of 1 .5 wt% microfibrillated cellulose and dried. The coated materials were spray coated directly with a solution of either deionized water, or a solution of 40% and 45% calcium chloride in deionized water, and dried. As illustrated in Fig. 2, it was found with that the water holding capacities were 1,249.7 and 1,370.3 kg / m3, respectively, measured at 25 degrees Celsius.

[0333] Example C2 - Kraft cellulose-fibre material coated with microfibrillated cellulose and red bentonite clay, and subjected to a calcium chloride treatment

[0334] In this example, five sheets of highly porous kraft cellulose-fibre material (125 gram per square meter) were spray coated directly by air atomizing spray nozzle with a dispersion of 1.5 wt% microfibrillated cellulose and 7.7 wt% red bentonite and dried. The coated materials were spray coated directly with a solution of either deionized water, or a solution of 15%, 20% or 50% calcium chloride in deionized water, and dried. As illustrated in Fig. 2, it was found with that the water holding capacities were 1,152.1, 1,370.3, 1,499.7 kg / m3, respectively, measured at 25 degrees Celsius.

[0335] Composite Material Orientation

[0336] This set of examples was used to probe the effect of orientation of the composite material of the invention in relation to the humidity gradient.

[0337] The composite material included: i) a first layer which is a substrate of 80 gsm paper to which is bound calcium chloride with a dry loading of 15-19 gsm; ii) a second layer which is a moisture resistive layer referred to as a latex precoat consisting of kaolin clay and latex at 9 gsm; and iii) an additional layer which is a moisture resistive layer formed from 8 gsm LDPE and 12 gsm PVOH, wherein the first layer is interposed between the second layer and the additional layer.

[0338] In shorthand, these components i) to iii) are referred to in the text that follows as: i) 80 gsm paper plus CaCb; ii) latex precoat; and iii) LDPE-PVOH.

[0339] The latex precoat was a typical composite coating of a clay and latex binder, not a continuous film of polymer as is typically used for barrier purposes. In these examples, this coating was provided at such a small level (i.e. low grammage) that its effect on MVTR is negligible.

[0340] In this set of examples, the region that is at higher humidity is referred to as being "upstream", whereas that region that is at lower humidity is referred to as being "downstream". The composite material may be oriented so that the LDPE-PVOH layer is proximal to the upstream (relatively "humid") region, so that the latex layer is proximal to the downstream (relatively "dry") region. Alternatively, the orientation of the composite material may be reversed so that the latex layer is proximal to the upstream (relatively "humid") region, so that the LDPE-PVOH layer is proximal to the downstream (relatively "dry") region. The moisture vapour transmission rate (MVTR) isotherm may be measured against time for each orientation.

[0341] A similar measurement was made for comparative purposes for control compositions that are not examples of the invention. The control material included: i) a substrate of 80 gsm paper - referred to below as 80 gsm paper untreated; ii) a moisture resistive layer formed from LDPE and PVOH - referred to below as LDPE- PVOH.

[0342] The MVTR isotherm results are presented below in Table 2 and in Figure 4:

[0343] * "rise time" is the duration over which an increase in MVTR was observed.

[0344] The results shown in Figure 4 demonstrate the effect of layering and orientation on MVTR, particularly over time. Whilst the control demonstrates typical Fickian behaviour (satisfying Fick's law), configurations A and B probe the effect of orientation - in particular demonstrating the effect of a heavier resistor upstream of the capacitor.

[0345] Please note that the orientation of Control A was reversed, yielding Control B, to rule out any effect the LDPE suppression may have on the PVOH layer.

[0346] In a non-Fickian structure as demonstrated above, incorporating calcium chloride coupled with heavier resistance upstream can result in a 38% increase in moisture barrier (for the given dry loading weight (gsm) of calcium chloride) without any additional polymer.

[0347] One explanation is that the calcium chloride doesn't just absorb moisture, it absorbs gradient. So the system overall slows vapor flow, not by resistance but by internal demand. Once at equilibrium and no longer absorbing, the structure still holds a large quantity of bound moisture, therefore the vapor phase remains suppressed compared to the external environment slowing diffusion across the structure.

[0348] By extending the absorption isotherm window, the composite material can buffer or mitigate moisture shocks caused by sudden changes in ambient humidity.

[0349] Across a composite material undergoing Fickian diffusion (which may be referred to herein as a 'Fickian stack') layering order would not be expected to affect MVTR if material(s) and gradient are constant. However, composite materials of the present invention have been demonstrated to display non-Fickian behaviour. To that end, Fick's Law assumes:

[0350] • A constant diffusion coefficient;

[0351] • A fixed concentration gradient; and

[0352] • A passive system.

[0353] However, composite materials of the present invention break all three of these assumptions:

[0354] • The material binds water, which in turn changes the concentration across the material profile;

[0355] • The material binds water, which in turn alters the concentration gradient over time (collapsing AP);

[0356] • The material are chemically active (to the extent that they bind water) - they are not just resistive.

[0357] Without wishing to be bound by theory, the present inventors believe that the effective diffusion coefficient (Deff) of the composite materials of the present invention may be related according to the following relationship:

[0358] Deff = D x f (RH, hydration state) where f is a nonlinear function that decreases with internal moisture binding.

[0359] To confirm the above findings on reduced MVTR behaviour the same sample (A and B above in this example) but with an additional 9 gsm of pigmented latex (composite material G3) were tested in both orientations to the moisture gradient - standard and reversed configurations. By the theory of Fick's law of diffusion, additional resistance should reduce moisture transmission when coupled with the suppressed vapor pressure gradient.

[0360] The second data set, represented in the graph of Figure 5 shows the same effect of reduced MVTR by suppression of vapor pressure gradient - for composite materials G3 -A and G3 - B (which is G3-A in the reverse configuration).

[0361] The data for G3-A and G3-B demonstrates two things:

[0362] A) the relationship between upstream resistance and MVTR over time, otherwise known as the absorption isotherm profile; and

[0363] B) the effect the internal vapor environment has on the vapor pressure gradient across the structure resulting in reduced MVTR relative to control samples, or in this case, the same in the reverse orientation as control. To further confirm the theory of vapor pressure suppression, MVTR tests were run again under the following preconditions: i) without pre-drying; and ii) after 2 months in storage.

[0364] For reference both controls in this scenario of G3 and G3 reversed are attached (Figure 6 and Figure 7). Data points were collected from two runs on the Mocon Permatran W 3 / 34 and / or 3 / 33 instruments over 50 hours and the average of the two runs at each data point was used (ASTM F 1249-20: Water Vapour Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infra-Red Sensor" using Mocon Permatran W 3 / 34 and / or 3 / 33 instruments. Test area: Nominally 5cm2).

[0365] From the results shown in Figures 6 and 7 it is apparent that the gradients of the two graphs follow a similar path, although values at time of recording are much below the results from the control material (described above and shown in Figure 4). This observation represented a significant departure from earlier expectations - significantly, it would not have been predictable that there would be a near 40% reduction for the same time period.

[0366] The graphs shown in Figures 5 to 8 demonstrate a reduction in MVTR, in some cases by 38% with no additional polymer. The present invention provides novel and non-obvious composite materials that may be used to provide superior barrier papers for food protection that align with environmental concerns and increasing regulatory standards for several reasons:

[0367] • First, the composite materials do not attempt to resist all moisture / vapor - rather the opposite - they allow moisture but provide a longer absorption isotherm. This approach is opposite to conventional wisdom and intuition.

[0368] • Second, the composite materials do not operate by conventional Fickian diffusion principles. The materials have the ability to suppress vapor pressure delta across a packaging substrate. That is, the very mechanism that governs moisture / vapor permeation / diffusion is compromised, in a way that produces an advantageous outcome.

[0369] A practitioner in barrier paper technologies would not reasonably expect that vapor suppression could be achieved by flattening the vapor pressure gradient within a substrate itself without relying on a continuous plastic film. Nor would they expect this approach to result in measurable improvements to MVTR over time.

[0370] Previous approaches in the field are directed toward reducing porosity or adding filmic layers - they do not teach manipulating the driving force for diffusion itself, which is the vapor pressure gradient, by using hygroscopic material bound to the substrate. This mechanism offers non-obvious advantages. Where traditional barriers rely on tortuous paths or impermeable membranes, the present invention alters the driving force for vapor ingress itself. This strategy of flattening vapor pressure gradients has not been explored in previous approaches and represents a new class of barrier design logic rooted in internal chemical eguilibria, not just structural resistance.

[0371] It is extremely likely that such mechanisms will be bound by a performance ceiling. Where that ceiling lies is governed by a multitude of factors - with cost, polymer content, and recyclability regulation being large influences. The present invention provides a step-change in thinking - moving beyond first principles of diffusion to a genuinely innovative approach. Instead of well-known and documented mechanisms commonly found in prior art such as tortuosity, density, crosslinking, hydrophobicity, surface energy, the composite materials of the present invention provide their advantageous effects through a combination of vapor pressure suppression and internal moisture modulation. This approach has not previously been utilized. Without wishing to be bound by theory, the mechanistic understanding of the present invention is presented in Figure 8.

[0372] In a Fickian stack, layering order would not be expected to affect MVTR if material(s) and gradient are constant. However, the present invention exhibits different behaviour.

[0373] Fick's Law assumes:

[0374] • A constant diffusion coefficient

[0375] • A fixed concentration gradient

[0376] • A passive system

[0377] However, the system of the present invention breaks all three assumptions:

[0378] 1. The system binds water (changing concentration profile)

[0379] 2. The systems provides an altered gradient over time (collapsing AP)

[0380] 3. The system is chemically active, not just resistive

[0381] The effective diffusion coefficient (Deff) of the structure of the present invention can be related as follows:

[0382] Deff = D x f (RH, hydration state) where f is a nonlinear function that decreases with internal moisture binding. Whilst the aforementioned mechanisms of traditional Fickian barrier chemistries are necessary, their overall effect has yet to be optimized or enhanced to enable a sizeable reduction in polymer content whilst maintaining current barrier performance and aligning with increasing regulation standards. These challenges have been addressed in part or whole by the composite materials of the present invention.

[0383] Furthermore, the system exhibits dynamic vapor interaction, buffering changes in ambient humidity through a time-dependent internal response. This behaviour is particularly advantageous in fluctuating storage conditions, such as cold-chain logistics or high-humidity regions. The hygroscopic material bound to the substrate acts not merely as a passive barrier, but as an active humidity modulator, extending protection during humidity spikes and preventing breakthrough events that conventional films often fail to mitigate.

[0384] One significant commercial benefit is the low cost of the preferred CaCI2additive (US$0.32 per kg) relative to current barrier materials. In contrast, specialized barrier chemistries typically range from $ 5 / kg up to $15 / kg. While direct comparisons with existing technologies can be complex, it is important to note that the function of the invention is not necessarily to replace polymer layers entirely, but rather to enable down-gauging of barrier films by supplementing their performance through internal vapor suppression. In this way, hygroscopic material (such as calcium chloride)-based systems can achieve meaningful MVTR reductions while reducing overall polymer usage, helping converters meet recyclability targets and reduce material costs simultaneously. Given most food groups typically require multiple barriers for protection, such costs can become an inhibiting factor for converters and brands economically. Converters must carefully balance cost-per-tonne economics, equipment compatibility, machine uptime, and claims risk — often while navigating brand pressure to deliver lower-plastic, recyclable or biodegradable formats without sacrificing functional performance. These competing demands create a narrow operating window for innovation. The resulting alternatives remain confined to niche, low volume applications, where higher unit costs and risk tolerance are more acceptable to brand owners. By utilizing the composite materials of the present invention - which may include a vapor engineered paper with a manufactured vapor suppressant - this has the potential to bridge the gap from niche to commodity papers in the market place. Therefore there is a strong commercial benefit to enable brands and converters to replace non- recyclable plastic laminates within economical constraints for high barrier food groups and expand market penetration of recyclable papers. By utilizing the composite materials of the present invention - namely a vapor engineered paper with a manufactured vapor suppressant - this has the potential to bridge the gap from niche to commodity papers in the market place. Critically, the invention answers a long-standing challenge in the industry on how to maintain high barrier properties without compromising recyclability or cost thresholds. By shifting the paradigm from 'resisting' water to 'modulating' it internally, this technology redefines what is possible for fiber-based substrates.

[0385] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

[0386] The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.

[0387] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

[0388] The technology may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

[0389] Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

[0390] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the technology and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present technology.

Claims

CLAIMS1. A composite material including a first layer and a second layer bonded to the first layer, wherein: i) the first layer includes a substrate including a matrix of fibres wherein a hygroscopic material (such as a water soluble hygroscopic salt) is bound (such as adsorbed) to the fibres (such as onto the surface of the fibres); and ii) the second layer is a moisture (such as provided as water) and / or gas (such as oxygen) resistive layer.

2. The composite material according to claim 1 wherein the hygroscopic material is a water soluble hygroscopic salt.

3. The material according to claim 2 wherein the cation of the hygroscopic salt is selected from: calcium; magnesium; aluminium; potassium; sodium; zinc; and lithium.

4. The composite material according to claim 2 wherein the anion of the hygroscopic salt is selected from: chloride; sulphate; carbonate; and nitrate.

5. The composite material according to any one of claims 2 to 4 wherein the hygroscopic salt is selected from: calcium chloride; magnesium chloride; aluminium sulphate; calcium nitrate; potassium nitrate; potassium carbonate; sodium nitrate; and sodium chloride; and combinations thereof.

6. The composite material according to any one of claims 2 to 5 wherein the hygroscopic salt is calcium chloride.

7. The composite material according to any one of claims 2 to 6 wherein the moisture (such as provided as water) and / or gas (such as oxygen) resistive second layer includes a polymeric material.

8. The composite material according to claim 7 wherein the polymeric material is selected from at least one of: LDPE; H DPE; LLDPE; PET; EVA; EAA; EMAA; PLA; PBS; PHA; PHB; PVOH; PVA; and blends or copolymers thereof.

9. The composite material according to claim 8 wherein the polymeric material is selected from at least one of: LDPE; PVOH; PHA; PHB; and blends or copolymers thereof.

10. The composite material according to any one claims 1 to 9 which is a packaging material.

11. The composite material according to any one of claims 1 to 10 wherein the hygroscopic material (such as the hygroscopic salt) is provided at from 5 to 100 grams per square metre surface area of the material.

12. The composite material according to any one of claims 1 to 1 1 further including an additional layer wherein the additional layer includes a polymeric material.

13. The composite material according to claim 12 wherein the polymeric material of the additional layer is selected from at least one of: an aliphatic polyester; an aromatic polyester; a polyamide; apolyurethane; an agro-polymer; a polysaccharide; a polypeptide; a vinyl alcohol; a polyethylene or substituted polyethylene; poly(ethylvinylacetate) (EVA) copolymer latex; styrene-butadiene latex; acrylic latex; polyvinylidene chloride (PVDC) latex.

14. The composite material according to any one of claims 1 to 13 having a MVTR of less than 300 g / m2 / 24hr, preferably less than 200 g / m2 / 24hr, more preferably less than 100 g / m2 / 24hr.

15. The composite material according to any one of claims 1 to 14 having a MVTR of less than 10 g / m2 / 24hr.

16. The composite material according to any one of claims 1 to 15 having a polymer content of 25% w / w or less.

17. The composite material according to any one of claims 1 to 16 wherein the substrate is a matrix of cellulose fibres, the hygroscopic salt is calcium chloride, and the composite material has a polymer content of 25% or less and an MVTR of less than 10 g / m2 / 24hr.

15. The composite material according to claim 1 wherein: i) the first layer includes a matrix of cellulose fibres wherein calcium chloride is bound to the cellulose fibres; and ii) a second layer which is a moisture resistive layer including PVOH or LDPE-PVOH.

16. The composite material according to claim 15 further including an additional layer including styrene-butadiene latex and kaolin clay, wherein the first layer is interposed between the second layer and the additional layer.

17. A coating system for applying to a substrate including a matrix of fibres to decrease moisture vapour transmission across said substrate, the coating system including: a first composition including: a hygroscopic material (such as a hygroscopic salt) which is water soluble (preferably wherein the cation of the hygroscopic salt (where used) is selected from calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium, and combinations thereof); and a first carrier^ a second composition including: a polymeric or pre-polymeric material and optionally a second carrier.

18. The coating system according to claim 17 wherein at least one of the first carrier and second carrier is an aqueous solvent.

19. The coating system according to claim 17 or claim 18 wherein: the hygroscopic material is calcium chloride; and / or the polymeric material is selected from at least one of: LDPE; HDPE; LLDPE; PET; EVA; EAA; EMAA; PLA; PBS; PHA; PHB; PVOH; PVA.

20. A method of treating a substrate including a matrix of fibres to provide a composite material having a decreased moisture vapour transmission compared with the substrate, the method including the steps of:i. providing a substrate including a matrix of fibres; ii. applying a first composition to the substrate, the composition including: a hygroscopic material (such as a hygroscopic salt) which is water soluble (preferably wherein the cation of the hygroscopic salt (where used) is selected from calcium, magnesium, aluminium, potassium, sodium, zinc, and lithium, and combinations thereof); and a first carrier; iii. removing at least a portion of the first carrier from the substrate; v. following step iii), providing the substrate with a moisture (such as provided as water) and / or gas (such as oxygen) resistive second layer, iv. so as to provide the composite material.21 . The method according to claim 20 wherein the step of providing the substrate with a moisture (such as provided as water) and / or gas (such as oxygen) resistive second layer may involve the modification of the structure of the substrate and / or the addition of material to the substrate.

22. The method according to claim 21 wherein the addition of material to the substrate includes the steps of: i) applying a second composition to the substrate, the second composition including: a polymeric or pre-polymeric material and optionally a second carrier; and ii) removing at least a portion of the second carrier, when used, so as to provide the composite material.

23. The method according to any one of claims 20 to 22 wherein at least one of the first carrier and second carrier is an aqueous solvent.

24. The method according to any one of claims 20 to 23 wherein: the hygroscopic material is calcium chloride; and / or the polymeric material is selected from at least one of: LDPE; HDPE; LLDPE; PET; EVA; EAA; EMAA; PLA; PBS; PHA; PHB; PVOH; PVA; and blends or copolymers thereof.

25. A package formed from the composite material according to any one of claims 1 to 16.

26. The package according to claim 25 which is recyclable.

27. The package according to claim 25 which is biodegradable.

28. The package according to claim 25 or claim 27 which is compostable.

29. The package according to claim 28 which is compostable under non-industrial composting conditions.

30. The composite material according to any one of claims 1 to 16 further including at least one of: i. a platy, high aspect clay; ii. a phyllosilicate mineral; and iii. a cellulosic particle.

31. The composite material according to claim 30 wherein the phyllosilicate mineral is selected from: a kaolinite; talc; illite; and a bentonite; and combinations thereof32. The composite material according to claim 30 wherein the cellulosic particle is selected from: a micro-fibril lated cellulose; microcrystalline cellulose; and nano-structured cellulose; and combinations thereof.

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