WO2023180329A1

WO2023180329A1 - Sealable card based container and blank therefor

Info

Publication number: WO2023180329A1
Application number: PCT/EP2023/057226
Authority: WO
Inventors: Franck PEREK
Original assignee: N.V. Nutricia
Priority date: 2022-03-21
Filing date: 2023-03-21
Publication date: 2023-09-28
Also published as: WO2023179843A1

Abstract

A card based container has a tubular sidewall of laminate material and first and second end closures, sealed to the tubular sidewall to form a hermetically sealed package. The sidewall comprises an outer card layer, an inner hygienic layer and one or more sealing strips provided at an inner surface of the inner hygienic layer, located at connection locations where the sidewall seals to itself or to the respective end closures. The sealing strips comprises a heat-sealable polymer. The overall amount of non-paper content in the sidewall and in the package may thus be reduced.

Description

SEALABLE CARD BASED CONTAINER AND BLANK THEREFOR

BACKGROUND OF THE INVENTION

Field of the Invention

[001] The present invention relates to containers made from laminated card material that can be effectively sealed and in particular to containers suitable for use as a primary packaging for food products. The invention also relates to the manufacture of such containers.

Description of the Related Art

[002] Card based containers of many different types are widely used, primarily for reasons of cost effectiveness and their relatively low environmental impact. These may range from low-grade corrugated cardboard boxes to high-value printed and embossed cartons for luxury goods and may range from materials with no oxygen and/or water vapour barriers to materials with very high oxygen and/or water vapour barriers. The containers may be primary packaging, in direct contact with their content or secondary packaging for surrounding an otherwise enveloped article. In this context, it is noted that card is sometimes referred to as carton, paperboard, cardboard or other variations. The term card is used in the following to mean all of the above as will further be defined below.

[003] The simplest packages may be based on card alone, while more complex packages may use combinations of card with other materials in order to produce a hybrid package with improved functionality. In particular, for use as a primary packaging with food products, a simple card material may not be adequate for reasons of hygiene, storage, and protection. This is especially the case for liquids, powders and fatty products or those susceptible to damp.

[004] One well known class of card based containers uses a laminate of polyethylene (PE), aluminium and card to form a primary package that is particularly suitable for storing powdered nutritional products. The PE layer is used as a food facing surface and also serves to heat seal the card to form the container. The aluminium acts as a barrier layer due to its good oxygen and water vapour barrier properties. It also acts as a light barrier. The card is provided at an outside of the container and provides structure and strength to the package. The card itself may be of various qualities depending on the required strength and outwards appearance. It can thus be printed or coated or otherwise decorated. Such a container is described in US5219087 and W02005/075314 and has been successfully marketed for many years under the name Cekacan TM.

[005] An important consideration in the terms of developing a packaging solution is its ability to be recycled or disposed of. More complex packages with greater functionality are often more difficult to handle during the waste disposal process. In some cases, it is possible to separate packages into their individual components and process each material accordingly. For laminates of different layers that require different processes for recycling, it has proven difficult to separate the layers. Despite their enormous advantages from a packaging perspective these packages have been difficult to recycle effectively. It would be desirable to improve the environmental impact of such packages.

[006] In particular, it would be desirable to provide a container that had a greater overall percentage of paper in the final container, that could be more easily recycled as a single item along with other paper, board, and laminate products.

BRIEF SUMMARY OF THE INVENTION

[007] According to the invention there is provided a card based container comprising a sidewall of laminate material and first and second end closures, sealed to the sidewall to form a hermetically sealed package, wherein the sidewall comprises: an outer structural layer comprising predominantly cellulose material; an inner hygienic layer; and one or more sealing strips provided at an inner surface of the sidewall, located at connection locations where the sidewall seals to itself and/or to the respective end closures, the sealing strips comprising a heat-sealable polymer. In existing packages, both the hygiene function and the heat sealing function are combined in a single layer that is present over the whole surface of the sidewall. This uses relatively large amounts of polymer that makes the resulting package more difficult to recycle. As a result of the proposed construction, much less heat sealable polymer is required in the final package. The hygienic layer can be relatively thin and need only perform the function of maintaining the sterility and/or hygiene of the product with respect to the outer structural layer. It may also assist in achieving other functions such as preserving freshness, humidity oxidation level etc in conjunction with other layers to be discussed further below. The heat sealing function is limited to the sealing strip, which can be provided in adequate thickness to achieve its function without significantly contributing to the amount of non-paper based materials in the container.

[008] The outer structural layer may have a weight of between 100 g/m2 and 500 g/m2, preferably from 150 g/m2 to 250 g/m2. Such weights are generally sufficient for packages in the domestic food sector e.g. for packages in the range of 100 ml to 5 litres in size. It may comprise any suitable card or paper construction in a single or multiple layers, including reinforced, corrugated, honeycomb and foamed constructions. For the purpose of the present specification, card is intended to denote a product that is primarily formed from cellulose pulp fibres, not excluding paper. Primarily formed, means that there may be small amounts of other materials including inorganic fillers, inks, binders and other additives conventionally included in the paper-making process. The card may be formed of virgin or recycled pulp and mixtures thereof.

[009] Importantly, the outer structural layer forms the bulk of the container, with any non-cellulose based materials forming a minor overall percentage thereof. In an embodiment the sidewall may comprise greater than 90 % cellulose pulp content or greater than 95% cellulose pulp content or even greater than 97% cellulose pulp content. By ensuring such a high cellulose pulp content, the sidewall and the resulting container may be deemed suitable for collection and recycling with paper and card based products. The precise requirements will depend on local or regional regulations.

[0010] The inner hygienic layer or food contact layer may comprise any suitable layer that achieves the required protection of the product that is to be stored in the container. In an embodiment, it may comprise a layer of food quality polymer material. Such polymer materials are those that have been approved by the relevant authorities for entering into contact with food products. This may vary according to the particular product and the time during which it is to be stored. The inner layer may suitably be a polyethylene polymer of the low density type, selected from the group consisting of LDPE, LLDPE, VLDPE, ULDPE or mLLDPE and blends of two or more thereof. Depending on the type of product, also inner layers of high density polyethylene, polypropylene or propylene co- or ter-polymers are conceivable. [0011] In particular, the inner hygienic layer may be liquid, water and oil or grease-proof. It may also be air or gastight and have oxygen barrier properties. The inner hygienic layer should have an adequate thickness to perform its function. It will be understood that to the extent that it is not paper based, the thinner the hygienic layer, the less will be its contribution to the overall non-paper content. In particular, it may merely need to be of a thickness to adequately seal the inner surface of the outer card layer. In an embodiment, the inner hygienic layer may have a thickness of less than 50 microns or less than 40 microns, preferably, less than 30 microns. In a preferred embodiment, the inner hygienic layer may have a thickness of less than 20 microns, preferably between 2 microns and 20 microns.

[0012] In conventional paperboard containers, the inner heat-seal layer may be significantly thicker, conventionally around 50 microns. Such a layer is usually formed by extrusion and applied in a laminating process to the other layers of the paperboard laminate or applied directly by extrusion coating. According to the present disclosure, other procedures may be used to apply the inner hygienic layer. It may thus be separately formed by extrusion but can also be applied to the inner side of the outer structural layer in a coating process, e.g. by extrusion coating or in the form of an aqueous or solvent-based dispersion or solution that may be sprayed, printed or otherwise applied onto the surface.

[0013] In the case of a coating, the thickness of the inner hygienic layer may be given as a weight e.g. from 1 to 20 g/m2 of dry product or preferably between 3 and 10 g/m2 of dry product. Measuring the thickness by weight may be more appropriate, since the surface irregularities of the card layer to which it may be applied can be of the same order of magnitude as the layer itself.

[0014] The container may comprise further layers in addition to the outer structural layer and the inner hygienic layer. In particular, while the inner hygienic layer may be the innermost layer, there may be additional layers between this and the outer structural layer in particular, there may be adhesive layers or bonding layers to ensure that each layer is compatible with the adjacent layer or layers. There may also be further layers outside the outer structural layer, such as a removable wrapper.

[0015] In an embodiment, there may be a barrier layer such as an oxygen barrier layer. This may be located between the inner hygienic layer and the outer structural layer. Additionally or alternatively, a barrier layer may be provided as part of the outer structural layer e.g. an intermediate layer between sub-layers of the outer structural layer.

[0016] In an embodiment the oxygen barrier layer may be a polymeric layer such as those described above as also being suitable as an inner hygienic layer having barrier properties. The skilled person will be familiar with all of the possible barrier layers that may be applied according to the degree of barrier required and also in relation to their compatibility with the adjacent layers. In a preferred embodiment, the barrier layer and/or the resulting wall of the container will have an oxygen transmission rate (OTR) of less than 0.1 cc/m2.day.

[0017] It is noted that metal layers such as aluminium may also be used for their barrier properties, including vapour deposited metal layers and layers coated with e.g., Al, SiOx, AlOx and the like. In one example, the barrier layer may be formed from a composition comprising a polymer selected from the group consisting of polyvinyl alcohol (PVOH), water dispersible ethylene vinyl alcohol (EVOH), ethylene vinyl alcohol vinyl acetate copolymer, polyvinylidene chloride (PVDC), water dispersible polyamide (PA), starch, starch derivatives, and combinations of two or more thereof. Such layers have been shown to not only be food compatible but also have good barrier functions against water vapour, oxygen and the like. Furthermore, a polymer or compound with functional carboxylic acid groups may be included in the composition to improve the water vapour or barrier properties, such as ethylene acrylic acid copolymer (EAA) and ethylene methacrylic acid copolymers (EMAA) or mixtures thereof. In an embodiment, the water vapour transmission rate (WVTR) may be less than 1 g/m2.day at 38 degrees C 90% RH. Preferably this should remain the case even after processing as may be recreated by 5 cycles of a Gelbo Flex tester according to ASTM F392: Standard Practice for Conditioning Flexible Barrier Materials for Flex Durability.

[0018] The outer structural layer may itself be a laminate comprising a plurality of layers. These may include one, two, three or more cellulose based layers of paper or card material, combined with intermediate layers of adhesive or barrier materials. The outer structural layer may also be provided with additional layers on its outer surface, in particular for decorative purposes. Such layers may include additional paper layers or labels, hygienic layers, such as the inner hygienic layer, lacquers, varnishes and printable layers or the like. [0019] The sealing strips may be provided in a thickness sufficient to ensure adequate connection and sealing of the container. Such thickness may generally correspond to the thicknesses used for the heat-seal layer in prior art paperboard containers. According to an aspect of the invention, the sealing strips may have a thickness of between 30 microns and 200 microns but preferably between 40 microns and 120 microns. The exact thickness of the sealing strip as determined for the final container will depend upon whether there is initially a sealing strip on both surfaces of a pair of surfaces to be joined and whether or not it is applied over the inner hygienic layer. In the following, reference to the sealing strip in the final container will refer to the thickness of the seal, regardless of whether it originates from one or the other of the surfaces. It should also be noted that the final thickness after heat-sealing may be reduced by flow of material under pressure.

[0020] Furthermore, the sealing strips may have a width appropriate for the joint to be formed and the length of seal required to achieve a hermetic closure. In an embodiment, the sealing strips may have a width of between 3mm and 20 mm, preferably between 7 mm and 15 mm. Here too, for the container, the value is given in the assembled state, whereby the seal strip may have spread due to the application of pressure or due to misalignment of a first seal strip with a second seal strip.

[0021] According to an important aspect of the invention, the sealing strip should be compatible with the inner hygienic layer. In this context, it is to be understood that it must be capable of sealing thereto to ensure a hermetic seal. It should also be compatible to the same extent with the connection locations of the end closures. Preferably, the sealing strip is also compatible with the outer structural layer or at least to an outermost layer provided thereon. This will need to be the case when the sidewall is sealed to itself in an overlap seal whereby the inner surface engages with the outermost surface. In an embodiment, an edge of the sidewall may be skived and a sealing strip applied to the inner surface may be folded over onto an outer surface of the sidewall for forming an overlap seal.

[0022] In an embodiment, one or both of the end closures may also comprise an outer structural layer and an inner hygienic layer. The end closures may be formed of the same material as the sidewall, whereby all of the layers are identical or just some of the layers may be the same. The one or more sealing strips provided at an inner surface of the sidewall may be located at the connection locations where the sidewall seals to itself in a longitudinal seam and where it seals to the lower end closure and the upper end closure in respective circumferential seams. In one example, a lower end of the container may be formed of the same material as the sidewall, with the possible exception of an outer decorative layer. In this case, the one or more sealing strips provided at an inner surface of the sidewall may be located only at the connection locations where the sidewall seals to itself in a longitudinal seam and where it seals to the lower end closure in a circumferential seam. The upper end of the container may be sealed with a different form of end closure, allowing it to be easily opened. For instance, the upper end closure may be a foil based upper end closure provided with a tear strip. The foil may comprise metal and/or polymer materials, which are at least partially removed in order to open the container. They may thus be separately disposed of and recycled.

[0023] In an embodiment, the sidewall at the upper end of the container has an upper rim that is rolled over outwardly, exposing the inner hygienic layer. A sealing strip may be provided circumferentially around the upper rim in particular facing upwardly. This allows an end closure to be applied across and sealed to the upper rim.

[0024] In an embodiment, the sidewall is tubular and comprises a longitudinal seal extending from the first end closure to the second end closure. The tubular crosssection may be circular or any other suitable shape such as oval, ovoid, oblong, rectangular and the like. The sidewall may also have a varying cross-section and may be conical or frusto-conical, waisted, tapering or of any other suitable form.

[0025] In addition to the end closures and the sidewall, the container may be provided with further components, including a resealable lid structure or a secondary wrapper of packaging. These components may be removable from the remainder of the container prior to recycling.

[0026] The invention also relates to a method of manufacturing a card based container, the method comprising: providing a blank of laminate material having longitudinal edges and upper and lower edges, the laminate material comprising an outer structural layer and an inner hygienic layer, applying one or more sealing strips of heat-sealable polymer onto the inner side of the blank, rolling the blank with the hygienic layer facing inwards and connecting the longitudinal edges together to form a tubular sidewall having first and second ends; closing the first end with a first end closure; filling the container with product through the second end; and sealing the container by applying a second end closure to the second end whereby connecting, closing and/or sealing takes place by heat sealing (melting) the strip of heat-sealable polymer.

[0027] In the present context, heat sealing is intended to refer to any suitable manner of generating and/or applying heat and pressure to melt the sealing strips, including welding, ultrasound, induction heating and the like. It will also be understood that such containers may be filled either through an upper or a lower end. Furthermore, reference to rolling of the blank is also considered to encompass folding of the blank should this be required to form the tubular sidewall.

[0028] Filling may take place in an aseptic environment and/or in the absence of oxygen. In particular, a vacuum may be applied to remove oxygen from the container, which may be flushed with an inert gas such as nitrogen and/or carbon dioxide prior to filling.

[0029] The sealing strip may be applied by any suitable process. In particular, it may be provided onto the sidewall at a point in the manufacturing process shortly prior to connection. Alternatively, it may be provided to the sidewall in a separate procedure e.g., during manufacture of the sidewall blank. It may be applied by extrusion, slot coating, spray coating, inkjet printing, transfer, or the like.

[0030] In general, the sealing strip or strips may be applied onto the hygienic layer. It is however also possible to apply the sealing strip directly onto the structural layer or an intermediate bonding layer. The hygienic layer and the sealing strips may also either fully or partially overlap each other. It may also be possible to apply the hygienic layer and the sealing strip in a single step or process, with the sealing strip being e.g., a thickened region of the hygienic layer. If the materials of the sealing strip and the hygienic layer are the same, then a step in the thickness of the hygienic layer may define the edge of the sealing strip. Merely as an example, PE may be applied at a thickness of around 20 microns as a hygienic layer but may increase to a thickness of 50 microns at the sealing strip location.

[0031] The sealing strip may be applied to the sidewall at one or more locations at which sealing is to take place. In an embodiment, a longitudinal sealing strip is applied to one of the longitudinal edges and the longitudinal edges are connected in an overlap seam. In an embodiment, the outer surface of the structural layer of the other of the longitudinal edge may be skived. The inner surface may then receive a sealing strip and be folded over such that the sealing strip faces outwards to be engaged in an overlap seam. The skilled person will be aware that other variations are possible. The longitudinal edges may also be abutted and a sealing tape can be applied to an inner surface of the sidewall to maintain the longitudinal edges in abutment. Such a sealing tape may include adequate reinforcement to ensure a firm joint. Alternatively, the longitudinal edges may be joined face to face and folded over at an outer side of the tubular sidewall.

[0032] Additionally, a lower strip may be applied to the lower edge of the blank and the first or second end closure can be heat-sealed to the lower edge of the blank. Alternatively, it will be understood that the lower edge may be devoid of a sealing strip and this may only be applied around an edge of the first or second end closure. In a further alternative, both surfaces may be provided with a sealing strip. In that case, each sealing strip may need to be less thick to nevertheless achieve adequate sealing.

[0033] In an embodiment, the heat-sealed lower edge may be rolled over inwards such that the container can stand on a lower rim of card material. Such a rolled joint is rather conventional for such card or paperboard containers as shown and described in US5219087 and W02005/075314, referenced above.

[0034] At the upper end of the container, the method may comprise applying a sealing strip at or adjacent to the upper edge of the blank, rolling over the upper edge of the blank to form an upper rim with the sealing strip uppermost and sealing the first or second end closure across the upper rim. The sealing strip thus extends circumferentially around the upper rim. Depending on the width of the sealing strip and the accuracy of its positioning, it may extend to the inside and to the outside of the container allowing for an effective seal at the crest of the rolled upper rim, or elsewhere if that is so desired.

[0035] The invention further relates to a blank of card based laminate material for forming the container or for carrying out the method as described above or hereinafter

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The features and advantages of the invention will be appreciated upon reference to the following drawings of a number of exemplary embodiments, in which: [0037] Figure 1 shows in perspective view a container according to an embodiment of the present invention;

[0038] Figure 2 shows the container of Figure 1 prior to assembly;

[0039] Figure 3 shows a cross-section through the sidewall of Figure 2 at III-III;

[0040] Figure 4 shows a detail of the container of Fig. 1 taken at IV-IV

[0041] Figure 5 shows a cross-sectional view through an upper part of a container according to a second embodiment of the invention;

[0042] Figures 6A to 6C show in schematic views, steps in making the longitudinal seam of the container of Figure 5 at the location VI- VI; and

[0043] Figure 7 shows a cross-sectional view through the laminate used in the sidewall of the container 100 of Figure 5.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0044] Figure 1 shows a perspective view of a container 1 according to the invention. The container comprises a tubular sidewall 2, closed at its lower end 4 by a first end closure 6. At its upper end 8, the container is closed by a second end closure 10. The container 1 has a longitudinal seam 12 extending from the lower end 4 to the upper end 8 and has a rim 9 on which it can stably stand.

[0045] Figure 2 shows the component parts of the container 1 of Figure 1 prior to their assembly. The sidewall 2 is in the form of a flat, rectangular blank 20 of card based material, to be described in further detail below. An inner hygienic layer 30 of the blank 20 is visible, namely the layer that will be at the interior of the container 1 once assembled. The blank 20 has longitudinal edges 22A,B an upper edge 24 and a lower edge 26. Applied onto the inner hygienic layer at the lower edge 26 is a lower sealing strip 27. An upper sealing strip 25 is applied at the upper edge 24 and a longitudinal sealing strip 23 is applied along one of the longitudinal edges 22A.

[0046] Figure 2 also shows the first end closure 6 and the second end closure 10. For the illustrated container, both end closures 6, 10 are oblong in shape, corresponding to the cross-section of the final container 1. It will be understood that various shapes are possible, including circular, elliptical, square, triangular and the like, although all polygonal shapes will preferably be provided with rounded corners. The first end closure 6 has a circumferential edge 7 and a structure that will be described further below. The second end closure 10 is an aluminium sealing film provided with a tear strip 11. It may be the sort of closure as described in EP3085636. It will be understood that other closures may also be used and that the second end 10 closure may also be identical to the first end closure 6.

[0047] Figure 3 shows a cross-section through the sidewall 2 taken in the direction III- III in Figure 2. The inner hygienic layer 30 is uppermost. This is a thin layer of PE having a thickness of 20 microns. On its surface, can be seen the upstanding lower sealing strip 27 and upper sealing strip 25. These are also the same PE material and have a thickness of 40 micron and a width of 5 mm. It will be understood that these dimensions are exemplary and Figure 3 is not to scale.

[0048] Beneath the inner hygienic layer 30 is an oxygen barrier layer 33, which comprises an aluminium barrier film 31 and an EVOH barrier film 32. At the outer side of the oxygen barrier layer is an outer structural layer 37. In the illustrated embodiment, the outer structural layer 37 is composed of an outermost card layer 36, an adhesive layer 35 and a thin paper layer 34. The outermost card layer 36 is a 200 g/m2 kraft card layer and the overall card/paper content exceeds 95 wt%.

[0049] Manufacture of the blank 20 may take place in otherwise conventional fashion. In the illustrated exemplary embodiment, the thin paper layer 34 is delivered from a roll to a deposition station where EVOH is spray coated as an aqueous dispersion and subsequently dried to a thickness of 15 micron. The aluminium barrier film 31 is then applied by vapour deposition onto the EVOH layer to a thickness of 5 micron. Finally, the PE inner hygienic layer 30 is applied by spray coating over the metallized aluminium barrier film 31.

[0050] In a subsequent lamination step, the coated, thin paper layer 34 and the outermost card layer 36 are assembled together with the adhesive layer 35 to form a continuous laminate of sidewall material that can be cut into blanks 20. In the illustrated embodiment, the strips 23, 25, 27 are applied to the blank 20 in a slot coating process prior to forming the sidewall. It will however be understood that they may also be applied earlier to the laminate of sidewall material prior to cutting.

[0051] Figure 4 shows a partial cross-section through the container 1 of Fig 1 at the location of the longitudinal seam 12 taken in the direction IV-IV.

[0052] As can be seen, at this location the longitudinal edge 22B having the longitudinal sealing strip 23 overlies the other longitudinal edge 22A. The longitudinal sealing strip 23 is heat sealed to the outer structural layer 37 of the longitudinal edge 22A. In this view, the outer structural layer 37 and the oxygen barrier layer 33 are schematically shown, distinguished by a dashed line, while the inner hygienic layer 30 cannot easily be distinguished from the sealing strip 23 where heat sealing has taken place.

[0053] Also visible in Figure 4 is the first end closure 6, applied to the lower end 4 of the tubular sidewall 2. The first end closure 6 is formed of the same laminate material as the sidewall 2 as described above in relation to Figure 3. It is distinguished in this embodiment only in that it is not provided with sealing strips.

[0054] The first end closure 6 is oriented with the inner hygienic layer 30 uppermost. The circumferential edge 7 is folded downwards into engagement with the lower end 4 of the sidewall 2 at the position of the lower sealing strip 27 and is heat sealed thereto. The combined structure of the lower end 4 of the sidewall 2 is rolled over inwards to form the lower rim 9. At this location of the seam 12, the rim 9 is formed of three layers of card material. Around the remainder of the circumference of the container 1, only two layers of material will be rolled to form the lower rim 9.

[0055] Figure 5 shows a cross-sectional view through an upper part of a container 100 according to a second embodiment of the invention. Distinguishing features over the first embodiment will be described and designated with the same reference numeral preceded by 100. Aspects of the container not described may be considered otherwise identical.

[0056] The container 100 comprises a sidewall 102 which, at its upper end 108, is rolled over outwardly to form an upper rim 140. An upper sealing strip 125 is applied at the crest of the upper rim 140 and extends around its full circumference. The container 100 is closed by a second end closure 110 that is sealed across the upper rim 140 and extends outwardly therefrom to a tab 142. The bottom of the container is closed by a first end closure (not shown).

[0057] The container 100 has a longitudinal seam 112 that can be seen from the inside of the container 100, extending above the level of the contents P. As in the previous embodiment, the sidewall 102 comprises an inner hygienic layer 130 and an outer structural layer 137. In this embodiment, the second end closure 110 is also manufactured of a similar laminate material and also has an inner hygienic layer 130 that engages with the upper sealing strip 125 and an outer structural layer 137. As previously discussed, the outer structural layer 137 is a multi-layer laminate as will be discussed further below. In this embodiment, the second end closure 110 is not provided with a tear strip but is instead removed in its entirety by pulling on the tab 142.

[0058] Figure 6C shows a schematic view of the longitudinal seam 112 of the container 100 of the second embodiment at the location VI- VI. Figures 6 A and 6B show similar views during steps in the construction of the longitudinal seam 112. As shown in Figure 6 A, the longitudinal seam 112 is made in a skiving process, whereby a portion of material is removed from the outer structural layer 137 at a first of the longitudinal edges 122A. In Figure 6B, this first longitudinal edge 122A is hemmed by folding over the skived edge with the inner hygienic layer 130 outwards. In Figure 6C the second longitudinal edge 122B is applied in an overlap onto the skived and hemmed first longitudinal edge 122A. The inner surface of the second longitudinal edge 122B carries a longitudinal sealing strip 123, which seals to the outer surface of the first longitudinal edge 122 A. Due to the skiving and hemming, the longitudinal sealing strip 123 is heat sealed to the inner hygienic layer 130, ensuring a fully compatible seal. It will be understood that this ensures that the inner hygienic layer 130 forms a continuous seal and that engagement to the outer surface of the outer structural layer is avoided.

[0059] Figure 7 shows a cross-sectional view through the laminate used in the sidewall 102 of the container 100 of the second embodiment. In this case, the sidewall comprises from outside in an outermost card layer 136, an adhesive layer 135, a primer layer 139, a metallized barrier film 131, an EVOH barrier film 132, a thin paper layer 134 and an inner hygienic layer 130. The lower sealing strip 127 is shown applied to the inner hygienic layer.

[0060] In this embodiment, it can be seen that the oxygen barrier layer 133, which comprises the metallized barrier film 131 and EVOH barrier film 132 is laminated within the outer structural layer 137. The skilled person will be well aware that various other laminate constructions may be contemplated and the individual layers may be adapted in thickness and construction as required.

[0061] Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art. Many modifications in addition to those described above may be made to the structures and techniques described herein without departing from the scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.

Claims

1. A card based container comprising a sidewall of laminate material and first and second end closures, sealed to the tubular sidewall to form a hermetically sealed package, wherein the sidewall comprises: an outer structural layer comprising predominantly cellulose material; an inner hygienic layer; and one or more sealing strips provided at an inner surface of the sidewall, located at connection locations where the sidewall seals to itself or to the respective end closures, the sealing strips comprising a heat-sealable polymer and having a thickness greater than that of the inner hygienic layer.

2. The container according to claim 1, wherein the inner hygienic layer comprises a layer of food quality polymer material.

3. The container according to claim 1 or claim 2, wherein the inner hygienic layer has a thickness of less than 20 microns, preferably between 2 microns and 20 microns.

4. The container according to any one of the preceding claims, wherein the outer structural layer has a weight of between 100 g/m2 and 500 g/m2, preferably from 150 g/m2 to 250 g/m2.

5. The container according to any one of the preceding claims, wherein the sidewall comprises greater than 95% cellulose pulp content, preferably greater than 97% cellulose pulp content.

6. The container according to any one of the preceding claims, comprising an oxygen barrier layer, preferably laminated within or to the outer structural layer.

7. The container according to claim 6, wherein the oxygen barrier layer is a polymeric layer exhibiting an oxygen transmission rate of less than 0.1 cc/m2.day.

8. The container according to any one of the preceding claims, wherein the outer structural layer is a laminate comprising at least one layer of card material.

9. The container according to any one of the preceding claims, wherein the sealing strips have a thickness of between 30 microns and 200 microns, preferably between 40 microns and 120 microns. The container according to any one of the preceding claims, wherein the sealing strips have a width of between 3 mm and 30 mm, preferably between 7 mm and 15 mm. The container according to any one of the preceding claims, wherein the sealing strips cover between 4% and 20% of the area of the sidewall. The container according to any one of the preceding claims, wherein one or both of the end closures comprises an outer structural layer and an inner hygienic layer. The container according to any one of the preceding claims, wherein the sidewall is tubular and comprises a longitudinal seal extending from the first end closure to the second end closure. The container according to any one of the preceding claims, wherein the sidewall has an upper rim that is rolled over and a sealing strip is preferably provided around the upper rim. The container according to claim 13 or claim 14, wherein the first or second end closure is applied across and sealed to the upper rim. A method of manufacturing a card based container, the method comprising: providing a blank of laminate material having longitudinal edges and upper and lower edges, the laminate material comprising an outer structural layer comprising predominantly cellulose material and an hygienic layer at an inner side of the blank, applying one or more sealing strips of heat-sealable polymer to the inner side of the blank, rolling the blank with the hygienic layer facing inwards and connecting the longitudinal edges together to form a sidewall having first and second ends; closing the first end with a first end closure; filling the container with product through the second end; and sealing the container by applying a second end closure to the second end whereby connecting, closing and/or sealing takes place by heat sealing the strip of heat-sealable polymer.

17. The method of claim 16, wherein a longitudinal sealing strip is applied to one of the longitudinal edges and the longitudinal edges are connected in an overlap seam.

18. The method of claim 16 or claim 17, wherein a lower sealing strip is applied to the lower edge of the blank and the first or second end closure is heat-sealed to the lower edge of the blank.

19. The method of any one of claims 16 to 18, wherein the heat-sealed lower edge is rolled over inwards such that the container can stand on a lower rim of card material.

20. The method of any one of claims 16 to 19, comprising applying a sealing strip at or adjacent to the upper edge of the blank, rolling over the upper edge of the blank to form an upper rim with the sealing strip uppermost and sealing the first or second end closure across the upper rim.

21. A blank of card based laminate material for forming a container for oxygen sensitive food materials, the blank comprising an outer structural layer comprising predominantly cellulose material, an inner hygienic layer and an oxygen barrier layer, wherein sealing strips of heat-sealable polymer material are provided at an inner surface of the blank at sealing locations such that the blank can be sealed to itself or to another component to form the container.

22. The blank of claim 21 for forming the container of any one of claims 1 to 15 or for carrying out the method of any one of claims 16 to 20.