WO2024110665A1

WO2024110665A1 - Packaging

Info

Publication number: WO2024110665A1
Application number: PCT/EP2023/083081
Authority: WO
Inventors: Mark Robinson
Original assignee: Smurfit Kappa Uk Limited
Priority date: 2022-11-24
Filing date: 2023-11-24
Publication date: 2024-05-30
Also published as: WO2024110045A1

Abstract

The present invention relates to transit packaging, such as packaging used for transportation of temperature-sensitive products, such as foodstuffs and human organs, whether they need to be maintained at low temperatures or elevated temperatures. In one aspect, the invention provides a thermal packaging product comprising a closable container formed of a primary substrate having a pigmented coating layer applied to at least an inner surface thereof; wherein the pigmented coating layer comprises at least one of a metallic material, a mineral material and a flake glass. The substrate is preferably a paperboard. The metallic material may be aluminium and/or copper. The mineral material is preferably a mica. The present invention also provides a thermal coating composition for recyclable packaging, the composition comprising at least one metallic, mineral and/or flake glass pigment in an amount of from about 5 wt% to about 50 wt.%, based on the total mass of the pigmented composition.

Description

PACKAGING

The present invention relates to packaging. More specifically, the present invention relates to transit packaging, such as packaging used for transportation of temperature-sensitive products, such as foodstuffs and human organs, whether they need to be maintained at low temperatures or elevated temperatures.

Presently, temperature-sensitive foodstuffs are typically transported in moulded expanded polystyrene (EPS).

EPS has a low density, typically in the region of 28-45 kg/m³ Around 98% of the mass of a moulded EPS product is air, giving EPS very high thermal insulating properties, making it a very suitable transit packaging material for both chilled or frozen products and heated products. EPS is also resilient to damage by water, such as condensation.

However, EPS is not considered to be an environmentally-sustainable material, due to the materials used in its manufacture and its poor record of recyclability. Whilst EPS is considered to be non-toxic and chemically inert in use, the materials from which it is formed are not. Expanded polystyrene is formed by polymerising styrene, which is highly flammable and is known to be carcinogenic, to form polystyrene beads. Styrene is also prone to autopolymerisation, an exothermic reaction, necessitating careful storage of the monomer and careful control of the polymerisation step.

The polystyrene beads are then exposed to a blowing agent, which penetrates pores in the beads, and the beads are treated with steam, causing the blowing agent to evaporate from the beads, expanding the polystyrene, to form expanded polystyrene beads. A typical blowing agent is the hydrocarbon pentane, also highly flammable.

The blown, expanded polystyrene beads are moulded by filling a mould with the beads and exposing the beads to steam, to bond adjacent beads to each other.

Accordingly, there is a need to develop packaging products having safer methods of manufacture whilst retaining the thermal advantages of EPS. Additionally, whilst moulded EPS packaging used for foodstuffs, human organs and so on, is capable of being reused a large number of times, in practice, it is only rarely re-used. Whether re-used over its lifespan or not, whilst EPS is capable of being recycled at the end of its life, in practice, very little recycling of EPS is carried out anywhere in the world due to the uneconomic costs of transporting materials which are very large in proportion to their mass. Consequently, EPS tends to be buried at landfill or incinerated.

Accordingly, there is also a need to develop thermal packaging products which lend themselves better to recycling. We have aimed to develop a thermal packaging material which can be recycled using entirely standard recycling routes, including those available to householders, through their municipal recycling facilities.

The high volume to weight ratio for moulded EPS packaging also results in relatively high costs for transportation of the packaging from the manufacturer’s factory where the blowing and moulding is carrier out to the customer’s site where the packaging will be used. The customer must also provide large storage capacity to store the moulded EPS packaging.

Yet further, whilst EPS beads are a closed-cell foam, moulded EPS includes interstitial gaps between the beads, such that moulded EPS is not entirely waterproof or vapour-proof. As a result, where the moulded EPS product will be exposed, in use, to high humidity or exposure to liquids, an impermeable plastic coating is often applied to the exterior of the EPS container, adding to both manufacturing complexity and recyclability.

The present invention seeks to address the problems in the prior art.

Accordingly, in its broadest sense, the present invention provides a packaging material suitable for temperature-sensitive products and compositions for use in manufacturing such packaging materials.

In a first aspect, the present invention provides a packaging comprising a closable container formed of a primary substrate and having a cavity for receipt of products to be packaged. The cavity has an inner surface having a coating layer applied thereto and wherein the coating layer comprises at least one of a metal or metallic material, a mineral material and a flake glass material.

The coating layer is applied as a continuous layer over the inner surface of the cavity or as a contiguous coating to panels of the inner surface.

In certain examples, the metallic material is at least one of aluminium and copper.

In other examples, the mineral material is a mica.

In certain embodiments, the mica has an average particle size in the range of between about 5 pm and about 25 pm.

In some embodiments, the pigmented coating further comprises an acrylic polymer binder.

Optionally, the pigmented coating layer has dry weight, applied to the substrate, of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1 .5 g/m²

In preferred embodiments, the pigmented coating layer comprises a mica, optionally a natural mica.

Optionally, the mica is present in the pigmented coating layer in an amount of from 0.1 to 1 .5 g/m², 0.12 to 1.0 g/m², 0.15 to 0.7 g/m² or about 0.2 to about 0.7 g/m².

In other embodiments, the pigmented coating layer comprises aluminium powder.

Optionally, the aluminium powder is present in the pigmented coating layer in an amount of from 0.1 to 1.0 g/m², 0.12 to 0.6 g/m², 0.15 to 0.5 g/m² or about 0.2 to about 0.4 g/m².

In some examples, the packaging further comprising at least one water-resistant barrier coating layer overlaying the pigmented coating layer.

Optionally, the barrier layer is coated to provide a dry weight amount of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1 .5 g/m².

Further optionally, the barrier layer comprises an acrylic polymer.

In certain examples, the primary substrate is selected from paperboard, such as cartonboard or boxboard, such as kraftboard or corrugated paperboard. Optionally, the container comprises a base portion having at least one wall extending upwardly therefrom, wherein there are no apertures between the base portion and the at least one wall or between adjacent wall portions.

Typically, the base portion is rectangular or square and includes side and end panels extending therefrom; wherein a corner web is formed between each adjacent side and end panel.

Suitably, the packaging further comprises additional layers of one or more further substrates, optionally wherein the one or more further substrates are formed of the same material as the primary substrate.

Advantageously, at least one of the additional layers includes a pigmented coating layer as defined above.

Optionally, at least one of the additional layers is a water-resistant barrier layer.

In a second aspect, the present invention also provides a method of improving the thermal insulation properties and/or liquid-resistance properties of a container formed of a primary substrate; the method comprising the steps of: i) applying a pigmented coating composition to an inner surface of the container to form a pigmented coating layer; and ii) applying at least one barrier coating composition to the pigmented coating layer to form a water-resistant barrier coating layer; wherein the pigmented coating composition comprises at least one of a metallic material, a mineral material and a flake glass material.

Optionally, the metallic material is at least one of aluminium and copper.

Optionally, the mineral material is a mica.

Advantageously, the pigmented coating layer has dry weight of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1 .5 g/m².

Preferably, the pigmented coating layer comprises a mica, optionally a natural mica.

In some examples, the mica is present in the pigmented coating layer in an amount of from 0.1 to 1.5 g/m², 0.12 to 1.0 g/m², 0.15 to 0.7 g/m² or about 0.2 to about 0.7 g/m². Alternatively, the pigmented coating layer comprises an aluminium powder.

In certain examples, the or each barrier layer is coated in a dry weight in an amount of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1 .5 g/m².

In a third aspect, the present invention provides a coating composition, the composition comprising at least one metallic pigment, mineral pigment or flake glass pigment in an amount of from about 5 wt% to about 50 wt.%, based on the total mass of the pigmented composition.

In some examples, the pigment is present in an amount of from about 5 wt% to about 40 wt%, about 5 wt% to about 30 wt%, or about 8 to about 30 wt%.

In some examples, the pigment includes a metallic powder present in the pigmented coating composition in an amount of from about 5 wt.% to about 30 wt.%, or from about 5 wt.% to about 25 wt.%, or from about 9 wt.% to about 20 wt.%.

In some examples, the pigment includes a mica in an amount of from about 10 wt.% to about 35 wt.%, or from about 15 wt.% to about 30 wt.%, or from about 20 wt.% to about 30 wt.%.

Optionally, the pigment is a mixed pigment comprising a mixture of at least two pigments selected from metal powders, mica and flake glass.

In some examples, the pigment includes at least one colourant or additional colourant.

In certain examples, the composition further comprises at least one carrier compatible with the pigment and one or more binders and optional processing aids such as dispersants and antifoaming agents.

Suitably, the carrier is water in an amount of from about 30 wt.% to about 60 wt.%.

Optionally, the composition further comprises a binder in an amount of from 20 wt.% to about 60 wt.%, further optionally an acrylic polymer binder. In certain examples, the composition further comprises a dispersant in an amount of about 0.1 wt% and/or an antifoaming agent in an amount of about 0.1 wt.%.

The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompany figures, in which:

Figure 1 is a perspective view of an embodiment of packaging in accordance with the present invention;

Figure 2 is a photograph showing water resistance exhibited by a first example substrate of packaging in accordance with the present invention;

Figure 3 is a photograph showing water resistance exhibited by a second example substrate of packaging in accordance with the present invention;

Figure 4 is a graph comparing thermal performance of an uncoated substrate with a white-coated substrate;

Figure 5 is a graph comparing thermal performance of packaging formed of an uncoated substrate with a first embodiment of packaging coated with a composition according to the present invention;

Figure 6 is a graph comparing thermal performance of packaging formed of an uncoated substrate with a second embodiment of packaging coated with a composition according to the present invention;

Figure 7 is a graph comparing thermal performance of packaging of the present invention coated with a mica-containing pigment with packaging of the present invention coated with an aluminium pigment; and

Figure 8 is a graph illustrating thermal performance of packaging of the present invention coated with a mica-containing pigment overcoated with two layers of a water-resistant barrier coating. In the present invention and embodiments of the present invention, the term packaging is intended to relate to packaging for enclosing or protecting products for distribution, storage, sale and use. The term encompasses packaging commonly referred to as boxes or containers.

The present invention is particularly concerned with packaging formed of planar materials such a packaging made of corrugated cardboard sheets, corrugated plastic sheets and similar materials.

Figure 1 is an exploded perspective view illustrating the principal components of an embodiment of packaging 10 in accordance with the present invention in the form of a box. The packaging 10 has a base Hand a lid 13. In the embodiment shown, the packaging includes an optional tray 12, dimensioned to fit within the base 11 . The lid 13 in the embodiment shown is a multiple-layer lid having an inner lid 13’ and an outer lid 13”. Lid 13 is dimensioned to provide a close fit against base 11. It will be appreciated by the skilled reader that numerous alternative constructions of packaging are well known in the art, including packaging in which a lid is formed as a hinged component within the same blank as based 11 .

As shown, in preferred embodiments, the base 11 is of a type in which the base has no apertures around its lower portion and sides through which liquids could leak. Typically, this is achieved by forming the base from a blank having a base panel 20 (obscured) with opposing end panels 21 and opposing side panels 22, with corner web portions 23 adjoining each adjacent panel, each web portion 23 being creased such that, in the assembled base, web portion 23 may be folded to form an external flap (as shown) or an internal flap.

In the embodiment shown in Figure 1 , each side panel 22 includes a side panel flap 24 which can be folded, in the assembled box, over the edge of its respective end panel, to provide additional rigidity.

Optional tray 12 is, in the specific embodiment illustrated, of a broadly similar construction, having a tray base panel 30 with adjoining end panels 31 and side panels 32, which web portions 33 adjoining adjacent panels and each foldable to form a flap 34, providing an aperture-free tray. In certain embodiments, an upper insert (not shown) identical to tray 12 is provided to be inserted into the base once the product to be transported has been inserted into the base. The upper insert serves to reduce the volume of the packaging immediately adjacent the product, which further improves temperature maintenance.

Lid 13 is constructed to fit over base 11 and has a broadly conventional construction which will be entirely within the skilled person’s common general knowledge and will not be described here in further detail.

In certain example embodiments, the box of the packaging of the present invention may be supplemented by one or more supplemental interior or exterior layers, such as layers selected from one or a series of outer boxes or containers, or sleeves and/or covers; or inner liners. Any or each of the supplemental payers may be coated with the compositions of the present invention.

An adhesive or adhesive tape may additionally be used to hold the components together. Additionally, or alternatively, locking tabs (not shown) may be included in the design of the packaging. The precise constructional details of the packaging may be varied having regard to the intended purpose of the packaging and the handling conditions under which it will be used. Such details are well within the scope of the common general knowledge of the skilled person.

In alternative embodiments, not shown, the packaging or components of the packaging may be moulded from a pulp material, such as paper pulp.

This design and construction of base 11 provides a tray formed of a continuous sheet of material such that there are no apertures in the sheet through which liquids, such as water (for example, as a condensate) can flow, either from the interior of the box to the exterior, or vice versa. Those skilled in the art will be readily able to devise modifications and alternative packaging constructions achieving the same effect. For example, the packaging may be formed with a circular, oval or polygonshaped base having a unitary wall extending upwardly therefrom, in which the wall is sealed to the base, for example by an adhesive and crimping.

The materials from which the substrate of the blank may be made will now be discussed in further detail. In certain embodiments, the blank may be formed from a plastics substrate, such as heavy-gauge polypropylene. Advantageous results are obtained with a corrugated plastics substrate.

However, in preferred embodiments, the substrate is formed from paperboard, such as cartonboard, containerboard or boxboard, such as Kraft board, or other material recyclable as paper, such as under recycling codes #20 PAP, #21 PAP or #22 PAP (Commission Decision of 28 January 1997 establishing the identification system for packaging materials pursuant to European Parliament and Council Directive 94/62/EC on packaging and packaging waste (Text with EEA relevance) (97/129/EC)). The present invention and embodiments of the present invention are particular useful with corrugated fibreboard/cardboard, in which at least one fluted sheet is sandwiched between flat liner boards, and which may include multiple layers of fluted sheets and liner boards.

The blank may be cut from the substrate material by any suitable method, such as die cutting.

The substrate from which the blank is formed is coated with a pigmented coating to enhance its properties. The step of coating the substrate may be carried out prior to cutting the blank from the substrate or after cutting the blank from the substrate.

The surface of the substrate which, in the assembled packaging, forms the internal surfaces of the cavity into which products are placed for storage, distribution and sale, is coated with a pigmented coating as described below. Other surfaces of the substrate may also be coated with a pigmented coating.

The packaging may include a plurality of sheets of the substrate, to form a multilayered packaging. Optionally, each of the plurality of sheets is coated, on one or both faces, with a pigmented coating.

Optionally, a primer coating layer is applied to the substrate prior to application of the pigmented coating.

Further optionally, the substrate may be subjected to a pre-treatment step to aide adherence of the pigmented coating and/or primer to the substrate. The pre- treatment may include any conventional process in the art such as a corona discharge treatment of plastics substrates.

Pigmented coating

A pigmented coating composition is applied to at least one face of the substrate to form, once dried, a pigmented coating. In some embodiments, both faces of the substrate are coated include a pigmented coating.

The pigmented coating composition comprises at least one reflective pigment material and a carrier.

In some examples, the pigment material comprises a metal, a ceramic, a mineral and/or a glass.

In certain examples, the pigment comprises a metallic or metal powder, a metallic or metal flake, a mica and/or a flake glass.

A metal-based pigmented coating composition typically includes a metal having the desired colour characteristics, such as aluminium, to give a silver colour, or copper, to give a golden colour. The coating may include further additives to provide desired properties, such as colourants, for example, mica pigments and/or flake glass pigments.

The amount of reflective pigment material may be chosen having regard to the process by which the pigmented coating will be applied to the substrate, which may dictate a maximum viscosity for the coating composition.

In a typical composition, the reflective pigment material is present in the pigmented coating composition in an amount of from about 5 wt% to about 50 wt.%, based on the total mass of the pigmented composition.

In certain examples, the reflective pigment material is present in an amount of at least about 5 wt%, at least about 10 wt%, at least about 15 wt%, or at least about 20 wt%. In some examples, the reflective pigment material is present in an amount of about 60 wt% or less, about 50 wt% or less, about 40 wt% or less or about 30 wt% or less.

In some examples, the reflective pigment material is present in an amount of from 10 wt% to 40 wt%, 15 wt% to 35 wt% or 20 wt% to 30 wt%. In certain examples, the reflective pigment is present in an amount of about 25 wt% ± 2 wt%.

In some examples, the reflective pigment material includes a metallic powder pigment. The metallic powder pigment may be present in the pigmented coating composition in an amount of from about 5 wt.% to about 30 wt.%, or from about 5 wt.% to about 25 wt.%, or from about 9 wt.% to about 20 wt.%.

In certain examples, the metallic powder pigment is or substantially comprises an aluminium powder.

In preferred examples, the reflective pigment material is or includes mica.

Mica may be present in the pigmented coating composition in an amount of from about 10 wt.% to about 35 wt.%, or from about 15 wt.% to about 30 wt.%, or from about 20 wt.% to about 30 wt.% or about 25 wt%.

The mica is preferably a natural mica. Synthetic mica, fluorophlogopite, may be used as an alternative, alone or in combination with a natural mica.

In preferred examples, the mica has a particle size or average particle size in the range of 5 pm to 25 pm. Larger particle sizes may show poorer in-plane alignment of mica particles, reducing the reflectance of the coated substrate. Additionally, larger particle sizes may cause problems with certain printing processes. A particle size of 5 pm to 25 pm has been found to perform well in flexographic printing processes.

Compositions containing mica as the pigment, with no metal, are considered to be preferable from an environmental perspective for recycling and repulping.

In alternative examples, not specifically described herein, flake glass having similar properties of particle size, is used in place of, or in addition to, mica. In certain examples, the pigment is a mixed pigment comprising a mixture of at least two pigments selected from metal powders, mica and flake glass.

Optionally, the pigment may include additional colourants. Such colourants may be used to provide a visual indication of characteristics of the pigmented coating or of the packaging as a whole.

The pigmented coating composition also includes one or more carriers, including solvents, compatible with the pigment, one or more binders and optional processing aids such as dispersants and antifoaming agents.

In respect of cardboard and similar substrates, a water-based carrier is preferred. In respect of plastic-based substrates, an organic solvent-based carrier may have advantageous properties.

The pigmented coating composition may include water in an amount of from about 30 wt.% to about 60 wt.%.

The pigmented coating composition may include a binder in an amount of from 20 wt.% to about 60 wt.%. Suitable binders include polymer binders, such as acrylic polymer binders.

The pigmented coating composition may further comprise a dispersant in an amount of about 0.1 wt% and/or an antifoaming agent in an amount of about 0.1 wt.%.

Coating process

In preferred examples, the pigmented composition is coated to give a dry weight of the pigmented coating layer on the substrate of from about 1 to about 5 g/m², about 1 to about 4 g/m²; or about 1 to about 3 g/m².

The pigmented coating composition may be applied by any technique suitable for applying a composition to a substrate. Preferred techniques include the use of an anilox roller. Advantageously, the anilox roller has a transfer volume in the range of from about 5 to about 20 cm³/m². In one example, an anilox roller having a transfer volume of about 12.5 cm³/m² was used, giving a wet weight for the applied pigmented coating composition of about 4 g/m² and a dry weight of about 1.6 g/m². It will be appreciated by the skilled person that the desired coating weight may most suitably be achieved in many instances, depending upon the chosen coating technique, by applying multiple layers of the coating composition rather than as a single layer. For example, application by a roller of a layer which is too thick or has too much volume can result in a mottled surface to the ink film, known as ‘orange peel’ due to a failure of the ink to flow to a uniformly thick film or by a roller tending to pick up ink as the roller curves away from applied film of ink. Such a surface is undesirable in the context of the present invention as it causes scattering of incident radiation, which may reduce the thermal effectiveness of the coating.

Example 1

In this example, the pigmented coating composition is a water-based metallic ink and comprises metallic particles in an aqueous acrylic binder.

A typical metal-pigment based pigmented coating composition has the following composition:

The coating composition is prepared using conventional mixing and blending techniques well-known to the skilled reader. Example 2

A typical mica-based pigmented coating composition has the following general composition:

The composition optionally further comprises further colourants, including metal pigments.

In certain examples, a single layer of the pigmented coating composition is applied to the substrate. In other examples, multiple layers are applied to the substrate, to provide the desired thermal profile to the substrate.

Prior to application of the pigmented coating, where necessary or advantageous, the surface of the substrate may be treated with a primer coating or subjected to other pre-treatment processes, as would be apparent to the skilled person. In certain examples, the substrate may be treated with a clay-containing composition, to improve keying of the reflective coating to the substrate.

Barrier coating

Whilst the reflective pigment coating will provide some water barrier properties, in preferred embodiments, a barrier coating composition is applied to the pigmented coating, once sufficiently dried, to improve its water and grease-resistance properties and resistance to damage

The barrier coating may be formed from any coating composition which is considered suitable, when dried or cured, for Direct Food Contact (DFC) applications.

In certain examples, the barrier coating composition is an acrylic emulsion-based barrier coating.

In some examples, a single layer of barrier coating composition is to the pigmented coating coated substrate. In other examples, two or more layers are applied.

In preferred examples, the dry weight of the barrier coating layer is from about 1 to about 5 g/m², about 1 to about 4 g/m²; or about 1 to about 3 g/m²

The barrier coating composition may be applied by any technique suitable for applying a composition to a substrate. Preferred techniques include the use of an anilox roller. Advantageously, the anilox roller has a transfer volume in the range of from about 5 to about 20 cm³/m². In one example, an anilox roller having a transfer volume of about 12.5 cm³/m² was used, giving a wet weight for the applied barrier coating composition of about 4 g/m² and a dry weight of about 1.6 g/m².

Example 3

A typical barrier coating composition may have the following general composition:

Example 4

The barrier coating composition may also include anti-bacterial agents, such as bismuth oxychloride. For example a modification to the coating composition of Example 3 has the following composition:

In other examples, the pigmented coating composition and barrier coating composition are combined into a single coating composition. In certain embodiments, multiple layers of the combined reflective and barrier coating composition are applied to the substrate. In certain examples, the dry weight of a combined coating composition is in the range of from about 2 g/m²to about 12 g/m²

Cobb value

The Cobb value (DIN EN ISO 535) quantifies the water absorption capacity of a cartonboard sample. The Cobb value relates to the amount of water that is taken up by a defined area of cartonboard through contact of one side of the cartonboard with water, typically measured over a period of 60, 180 or 1800 seconds.

In preferred embodiments, the substrate is coated to provide a Cobbeo value (tested over a period of 60 seconds) of 30 g/m² or less, preferably 20 g/m² or less, more preferably about 10 g/m² or less than about 10 g/m².

Coating compositions having a barrier coating of Example 3 or Example 4 have exhibited, in trials, Cobbeo values of about 10 g/m² or less. This forms a further aspect of the present invention.

Water-resistant coating In certain examples, a face of the substrate which, in the assembled box forms the outer surface of the box, is provided with a food packaging-compatible varnish or lacquer to provide additional external water-resistance to the box.

Additional coatings

In some examples, the reflective-containing coating or the barrier or water-resistant barrier coating may include a thermochromically-active material, having a thermochromic response relating to an intended temperature, in use, for the packaging. In an alternative embodiment, the thermochromically-active material may be provided in a separate coating layer.

One or more of the coatings may include antibacterial compositions, uv-protective coatings and so on.

In preferred examples, all materials used in the packaging are fully recyclable and repulpable.

Application processes

As discussed above, roller coating by means of an anilox roller has been determined to be a particularly suitable method for application of the coatings. Nevertheless, other conventional coating and printing methods are equally suitable, as will be apparent to the skilled person, including flexographic printing, gravure printing, screen-printing, lithographic printing, digital printing, spray coating, Meyer rod coating or gap coating, for example. The same or different processes may be used for applying the reflective coating from applying the direct food coating.

Other components

In modifications of the embodiments described above, the box of the packaging of the present invention may be supplemented by one or more supplemental interior or exterior layers, such as layers selected from one or a series of outer boxes or containers, or sleeves and/or covers; or inner liners.

In certain embodiments, the packaging comprises an inner liner formed of a box as described above, formed of a containerboard or corrugated sheet board, together with 1 to 7 supplemental layers of corrugated sheet board. In tests, packaging having an inner liner as described above with 3-5 supplementary layers of corrugated sheet board were found to have thermal properties comparable to moulded EPS.

The configuration and construction of such additional layers will be apparent to the skilled person and will not be described in further detail here.

The packaging may further be supplemented by inclusion of additional materials to protect the product with which the packaging is intended to be used, including glassine and/or corrugated liners, for example.

Advantageously, at least some of any supplemental layers and/or additional materials are also treated to have a reflective coating on at least one surface thereof. The supplemental layers and/or additional materials are also treated with a barrier layer composition. In some examples, outer-facing surfaces are treated with a food packaging-compatible varnish or lacquer, as described above

EXPERIMENTAL

Materials

Substrate:

The following materials have been found to be particularly suitable for our purposes:

Royal White/Royal White NB - a two-ply kraftliner, available in weights of 115, 125, 135, 160, 175 and 200 g/m² Royal White has a typical Cobbeo value of 30 g/m². Royal Cote Plus - a three-ply kraftliner with a fully-coated white top ply, double-coated at a total weight of about 20 g/m² and available in weights of 135, 155, 175 and 190 g/m² and with a typical Cobbeo value of 30 g/m².

Smurfit Kappa Kraftliner Brown - a two ply kraftliner, available in weights of 110, 125, 135, 160, 170, 186, 200, 225, 275 and 300 g/m²; and with a typical Cobbeo value of 30 g/m².

Royal 2000 - a two ply kraftliner available in weights of 115, 125, 135, 160 and 175 g/m². Royal 2000 has a typical Cobbeo value of 30 g/m².

Royal White, Royal White NB, Royal Cote Plus, Royal and Smurfit Kappa Kraftliner Brown are trade marks of Smurfit Kappa.

Coatings

Reference Example 1.

In order to provide a baseline for comparing enhanced properties of substrates treated with compositions of the present invention, reference packaging was formed from an untreated 140 g/m² paper - Reference Example 1 - and from a Prime WKL white-coated paper of the same gauge - Reference Example 2 and their performance was assessed by preparing freezing 200g water in a metal container (- 18°C), wrapping the paper around the container and measuring the temperature of the paper over a period of 16 hours. The results are shown in Figure 4. As can be seen, the presence of a white coating had a negligible impact on the temperature profile of the packaging. An initial temperature drop from ambient over the first hour transitioned to a relatively stable period of 4-5 hours at around 14°C, after which the temperature returned to ambient relatively quickly.

Inventive Examples A substrate was providing having the following sequence of layers: 155gsm Light Clay Coated White Top Kraft I 85gsm RF1 (recycled single flute) I 85gsm RF1 I 85gsm RF1 1 160gsm White Top Kraft.

The compositions of the present invention were applied to the sample substrate by roller coating with a 7.5 cm³/m² roller, with two coats applied at an applied weight of about 6 g/m² (wet), and allowed to dry, giving a final applied weight when dry of about 3 g/m².

A water-resistant coating comprising an acrylic polymer having a solids content of 30-50 wt.% was applied to the substrate coated with the pigmented compositions by a roller coating method, using a 12-14 cm³/m² roller, at an applied film weight of about 7 g/m² (wet), giving a dry weight of about 3 to 4 g/m².

Similar results were obtained with application of the pigmented coating compositions and barrier coating compositions to the substrates using a 6 micron wire bar.

The coated substrates were left at room temperature for a minimum of 12 hours to dry.

In the following examples, values may not add up to 100.00 due to rounding.

Example 5 - metal pigmented coating composition

A metallic, water-based coating composition was prepared having the following composition.

Example 6 - mica pigmented coating composition

An aqueous mica-based composition was prepared having the following composition:

Example 7 - barrier (water-resistant) coating composition A barrier composition having the following composition was prepared:

Example 8 - Barrier coating

A further barrier composition was prepared, having the following composition:

Example 9 - Empty packages A first box of the construction described above was coated with a mineral primer layer and a layer of the pigmented coating of Example 5. A second, identically constructed box, was coated with two layers of the pigmented coating of Example 5. Both boxes were placed in a refrigerator set at 5°C for 24 hours. Throughout the test, the second box maintained a temperature which was, on average, 2°C ± 0.2°C colder than that of the first box.

Example 10 - Frozen fish test

This example was performed to represent performance of the inventive packaging as might be used in an e-commerce supply of frozen fish, in which a box of frozen fish might be removed from a refrigerated delivery vehicle and left on a customer’s doorstep for some time before being taken in by the customer.

A box of the construction described above was coated with the pigmented coating material of Example 5. An uncoated box was used as a control. Equal weights of frozen fish were placed in each box together with a thermal sensor. The boxes were left at room temperature (approximately 20°C) and the temperature was monitored over 24 hours and the results shown in Table 1 below and illustrated in Figure 5.

Table 1

As can be seen, the coated packaging maintained a lower temperature throughout the test, remaining an average of over 2°C cooler than the uncoated box and remaining over 3°C cooler at the end of the test.

It should be noted that the frozen fish were packed into the boxes at room temperature, which is why the initial readings are above 0°C.

The test was repeated with boxes containing 5kg of frozen fish and the results shown in Figure 6. Again, an average temperature difference of over 2°C was seen over the duration of the test, with a difference at the end of the test in excess of 3°C

Example 11 - Frozen water test

Two samples were prepared of water (200ml) frozen in a small metal container and wrapped with coated single-ply (non-fluted) substrates, one coated with a composition of Example 5 and one coated with a composition of Example 6, each with an electronic thermal sensor therebetween. The results are shown in Figure 7, showing comparable thermal resistance for the mica-based coating with the aluminium-based coating over the first 10 hours of the test. The test was repeated comparing an untreated substrate with the mica-based coating of Example 6. The mica-based coating showed an average temperature improvement over the first 4 hours of the test of around 2°C. Example 12

A box was prepared as described above, having a 150 gsm waste based (recycled fluting) substrate having a 160 gsm coated white kraft inner liner and 200 gsm brown kraft external liner. The box was provided with an internal coating of a micacontaining composition as described in Example 6 above, to which two layers of a barrier coating as described in Example 8 above were applied.

The box had dimensions of 385mm length, 255mm width and a height of 173mm. The box was conditioned at -12°C for two hours prior to testing. Frozen meat (3kg) at -19°C, was placed in the box together with 4x1 kg slices of dry ice. A UTRIX-16 temperature data-logging device was placed in the box and an upper insert formed of a tray 12 as described above was placed over the contents to reduce the internal volume of the box. The interior of the box was thereby chilled from an ambient temperature of 24°C to -40°C. The box was placed in a Weiss Technik Labevent environmental test chamber set to replicate ambient temperature for 48 hours. The internal temperature of the box was recorded at 3 minute intervals and the data is plotted in Figure 8.

As can be seen, the internal temperature of the box remained below -30°C for 12 hours and remained below 0°C for over 33 hours.

Example 13 - water resistance

The water-resistance of fully-coated packaging in accordance with the present invention was assessed to determine Cobbisoo values (according to DIN EN ISO 535), with a contact time of 1 ,800 seconds. Cartonboard substrates having different grades of fluting - fine fluting (E), coarse fluting (B) and a double-walled combined (EB) grade were prepared and coated, both internally and externally, with two layers of the barrier coating of Example 8. Identical substrates were prepared with a layer of the mica-containing composition of Example 6 prior to application of an identical coating of two layers of the coating of Example 8 again both internally and externally.

The results are shown in Table 2 below:

Table 2

As can be seen from these results, the inclusion of a pigmented coating below the barrier coatings provides a surprising reduction in the Cobbisoo value, down to Cobb values of the order of 10 to 20.

Results

The example coatings provided a highly water-resistant coated substrate - see Figures 2 and 3 and Example 12.

The repulpability and recyclability of the coated substrate was also tested, which demonstrated full compliance with standard paper recycling protocols. Substrates coated with metal-containing pigment compositions include metal flakes in the pulp from pulping the coated substrates, which may limit reuse of the pulp. Those substrates including a mica-based pigment demonstrated no issues around recyclability.

The pigmented coating compositions based on a mica pigment have a better recycling profile and have been demonstrated to be able to achieve equal thermal performance to reflective metallic coatings and both types of coatings provide enhanced thermal performance, whether in maintaining a cool temperature within the packaging or in maintaining heated conditions within the packaging.

Whilst providing packaging having thermal properties comparable to moulded expanded polystyrene, the packaging of the present invention consists of components which are all safe to handle as regards preparation of the packaging and which can all be recycled through entirely conventional recycling routes and procedures.

The coating compositions follow conventional preparative routes and manufacture of the blanks for the packaging can use a range of entirely conventional printing or coating machines to prepare the coated substrates and entirely conventional die cutting machines, for example, to shape the blanks from the substrates. See, for example, Ullmann’s Encyclopaedia of Industrial Chemistry, Printing Inks, and the references cited therein.

A further advantage of the packaging of the present invention resides in the advantage that the packaging can be supplied from the manufacturer in a stacked, flattened configuration, typically occupying around one twentieth of the volume of the equivalent moulded EPS packaging. Consequently, transportation costs per unit packaging are considerably lower and the storage requirements, and consequent costs, for the customer are greatly reduced.

Claims

1 Packaging comprising a closable container formed of a primary substrate having a coating layer applied to at least an inner surface thereof; wherein the coating layer comprises at least one of a metallic material, a mineral material, and a flake glass material.

2. Packaging as claimed in claim 1 wherein the metallic material is a metal powder or metal flakes, optionally at least one of aluminium and copper.

3. Packaging as claimed in claim 1 wherein the mineral material is a mica.

4. Packaging as claimed in claim 3 wherein the mica has an average particle size of between 5 pm to 25 pm.

5. Packaging as claimed in claim 1 wherein the pigmented coating layer comprises a mica, optionally a natural mica.

6. Packaging as claimed in claim 6 wherein the mica is present in the pigmented coating layer in an amount of from 0.1 to 1 .5 g/m², 0.12 to 1.0 g/m², 0.15 to 0.7 g/m² or about 0.2 to about 0.7 g/m².

7. Packaging as claimed in claim 1 or claim 2 wherein the pigmented coating layer comprises aluminium powder.

8. Packaging as claimed in claim 7 wherein the aluminium powder is present in the pigmented coating layer in an amount of from 0.1 to 1.0 g/m², 0.12 to 0.6 g/m², 0.15 to 0.5 g/m² or about 0.2 to about 0.4 g/m².

9. Packaging as claimed in any preceding claim wherein the pigmented coating further comprises an acrylic polymer binder.

10. Packaging as claimed in any preceding claim wherein the pigmented coating layer has dry weight of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1 .5 g/m².

11 . Packaging as claimed in any preceding claim further comprising at least one water-resistant barrier coating layer overlaying the pigmented coating layer.

12. Packaging as claimed in claim 11 wherein the barrier layer is coated in a dry weight amount of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1 .5 g/m².

13. Packaging as claimed in claim 11 or claim 12 wherein the barrier layer comprises an acrylic polymer.

14. Packaging as claimed in any preceding claim wherein the primary substrate is selected from paperboard, such as cartonboard or boxboard, such as kraftboard or corrugated paperboard; or corrugated plastic.

15. Packaging as claimed in any preceding claim wherein the container comprises a base portion having at least one wall extending upwardly therefrom, wherein there are no apertures between the base portion and the at least one wall or between adjacent wall portions.

16. Packaging as claimed in any preceding claim wherein the base portion is rectangular or square and includes side and end panels extending therefrom; wherein a corner web is formed between each adjacent side and end panel.

17. Packaging as claimed in any preceding claim further comprising additional layers of one or more further substrates, optionally wherein the one or more further substrates are formed of the same material as the primary substrate.

18. Packaging as claimed in claim 17 wherein at least one of the additional layers includes a pigmented coating layer as defined in any preceding claim.

19. Packaging as claimed in claim 17 or 18 wherein at least one of the additional layers is a water-resistant barrier layer.

20. A method of improving the thermal insulation properties and/or liquidresistance properties of a container formed of a primary substrate; the method comprising the steps of: i) applying a coating composition to an inner surface of the container to form a coating layer to the substrate of the container; and ii) applying at least one barrier coating composition to the coating layer to form a water-resistant barrier coating layer; wherein the coating composition comprises at least one of a metallic material, a mineral material and a glass flake material.

21. A method as claimed in claim 20 wherein the metallic material is at least one of aluminium and copper.

22. A method as claimed in claim 20 or claim 21 wherein the mineral material is selected from mica and glasses, optionally glass flakes.

23. A method as claimed in any one of claims 20 to 22 wherein the coating layer has dry weight of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1 .5 g/m²

24. A method as claimed in claim 20 wherein the coating layer comprises a mica, optionally a natural mica.

25. A method as claimed in claim 24 wherein the mica is present in the coating layer in an amount of from 0.1 to 1 .5 g/m², 0.12 to 1 .0 g/m², 0.15 to 0.7 g/m² or about 0.2 to about 0.7 g/m².

26. A method as claimed in claim 20 wherein the coating layer comprises aluminium powder.

27. A method as claimed in claim 26 wherein the aluminium powder is present in the coating layer in an amount of from 0.1 to 1.0 g/m², 0.12 to 0.6 g/m², 0.15 to 0.5 g/m² or about 0.2 to about 0.4 g/m².

28. A method as claimed in any one of claims 20 to 27 wherein the or each barrier layer is coated in a dry weight in an amount of from 0.5 to 3 g/m²; 0.75 to 2 g/m², or about 1 to 1.5 g/m².

29. A coating composition for recyclable packaging, the composition comprising at least one of a metallic pigment, a mineral pigment and a flake glass pigment in an amount of from about 5 wt% to about 50 wt.%, based on the total mass of the pigmented composition.

30. A composition as claimed in claim 29 wherein the pigment is present in an amount of from about 5 wt% to about 40 wt%, about 5 wt% to about 30 wt%, or about 8 to about 30 wt%.

31. A composition as claimed in claim 29 or claim 30 wherein the pigment includes a metallic powder present in the pigmented coating composition in an amount of from about 5 wt.% to about 30 wt.%, or from about 5 wt.% to about 25 wt.%, or from about 9 wt.% to about 20 wt.%.

32. A composition as claimed in claim 29 or claim 30 wherein the pigment includes a mica in an amount of from about 10 wt.% to about 35 wt.%, or from about 15 wt.% to about 30 wt.%, or from about 20 wt.% to about 30 wt.%.

33. A composition as claimed in any one of claims 29 to 32 wherein the pigment is a mixed pigment comprising a mixture of at least two pigments selected from metal powders, mica and flake glass.

34. A composition as claimed in any one of claims 29 to 33 wherein the pigment includes at least one additional colourant.

35. A composition as claimed in any one of claims 29 to 34 further comprising at least one carrier compatible with the pigment and one or more binders and optional processing aids such as dispersants and antifoaming agents.

36. A composition as claimed in claim 35 wherein the carrier is water in an amount of from about 30 wt.% to about 60 wt.%.

37. A composition as claimed in claim 35 or claim 36 comprising a binder in an amount of from 20 wt.% to about 60 wt.%, optionally an acrylic polymer binder.

38. A composition as claimed in any one of claims 29 to 36 further comprising a dispersant in an amount of about 0.1 wt% and/or an antifoaming agent in an amount of about 0.1 wt.%.