Paperboard-based container

Abstract

A multilayer barrier coating (50) comprising as layers of a layer sequence, a layer (51, 51a, 51b) comprising polyvinyl alcohol (PVOH), a bonding layer (52, 52a, 52b) and a moisture barrier layer (53, 53a, 53b); wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater, a laminated packaging sheet material (100) a container (1) for holding a pourable food product, a blank for making the container a method of manufacturing a multilayer barrier coating (50) and a method of manufacturing a laminated packaging sheet material (100).

Description

[0001] PAPERBOARD-BASED CONTAINER

[0002] Field of the invention

[0003] The present invention relates to a multilayer barrier coating, a laminated packaging sheet material, a container for holding a food or non-food product, e.g. a pourable food or non-food product, a blank for making the container, a method of manufacturing a multilayer barrier coating and a method of manufacturing a laminated packaging sheet material.

[0004] Background

[0005] Within the art of paperboard-based packaging, it is known to produce a blank which is folded and assembled to produce a container. The container may then be utilised to hold a pourable food product, e.g. a liquid, e.g. dairy products, such as milk or yoghurt, or juices or other food or non-food products.

[0006] The blank is typically produced from a laminated packaging material, which typically comprises a multi-ply paperboard sheet on which is laminated one or a plurality of barrier layers for holding the food product and / or prevent migration of air and flavours through the paperboard.

[0007] A method of producing the blank from the laminated packaging material typically comprises the steps of cutting the laminated packaging material to a predefined shape, and a method of producing the container from the blank typically comprises the step of folding the blank along predefined folding lines to produce the container.

[0008] The blank may be provided with crease lines in the laminated packaging material to aid folding of the blank along the folding lines. A crease line, or crease, may be defined as an embossed or impressed depression on one side of the laminated packaging material with a corresponding raised ridge or welt, also referred to as the bead, on the other side forming a line along which the laminated packaging material is structurally weakened and along which the laminated packaging material will bend or fold when pressure is applied.

[0009] Alternatively, a paperboard-based container may be produced in a roll-fed process in which a continuous web of laminated packaging material is fed to a filling machine, folded and sealed longitudinally to form a tube. The tube is then filled with the pourable food product, sealed and cut transversally to form so called pouches. The pouches are then provided with an opening device and manipulated to obtain its final form. Said manipulation typically involves folding down and securing sections of the container to side panel section of the same.

[0010] The container may be provided with an opening arrangement allowing a consumer to open the container to access the food product. In the prior art, it is known to use plastic opening arrangements, such as arrangements comprising plastic pour spouts and lid portions. A particular advantageous opening arrangement for such containers is based on the known halfcut method. Details of the half-cut method are disclosed in EP1786618B1. The major advantage of the half-cut method is that the barrier layer is fully intact until the container is opened by an end user. Another advantage of the half-cut method during production is that the laminated material may initially be produced as a homogenous sheet without any cutouts. In similar methods for obtaining an opening having an intact barrier layer, the paperboard is provided with openings before lamination and at least the barrier layer is subsequently laminated over the paperboard including the openings.

[0011] In recent years, society has focused on preventing the generation of waste while encouraging the reuse, recycling, and other means of recovering waste. This is also the case for the packaging industry.

[0012] In order to improve the sustainability properties of laminated material, blanks and container, a focus of the industry has been to produce materials that are easier to recycle, for example by replacing the material of the barrier layer with more sustainable materials.

[0013] However, there is still a lot of room for improvement in terms of sustainability for the laminated material, blanks and container as a whole. An object of the present invention is to provide laminated material, blanks and container having improved sustainability properties.

[0014] Summary of the invention

[0015] The present invention is defined by the appended claims and in the following:

[0016] In a first aspect, the invention relates to a multilayer barrier coating comprising as layers of a layer sequence, a layer comprising polyvinyl alcohol (PVOH), a bonding layer and a moisture barrier layer; wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater.

[0017] In an embodiment, the layer comprising PVOH has a degree of hydrolysis of 75% or greater, 80% or greater, 85% or greater or 90% or greater.

[0018] In an embodiment, the layer comprising PVOH has a melting point in the range 150°C to 225°C; 160°C to 225°C; 170°C to 220°C or 180°C to 220°C.

[0019] In an embodiment, the layer comprising PVOH has a melting point over the melting point of the moisture barrier layer.

[0020] The layer comprising PVOH may also comprise one or more plasticisers. The plasticisers may be selected from the group consisting of polyethylene glycols, polyhydric alcohols, glycerol, diols or triols, for example, propylene glycol, ethylene glycol, polyethylene glycol, glycerol, mannitol erythritol, pentaerythritol sorbitol, trimethylolpropane and mixtures thereof.

[0021] A bonding layer is a layer that enhances or ensures adhesion between the layers adjacent to the bonding layer. A bonding layer may also be called an adhesive layer or a tie layer.

[0022] In an embodiment, the bonding layer may comprise a polyolefin, such as a polyethylene or a functionalized polyethylene, such as a polyethylene grafted with a polar group, such as maleic anhydride.

[0023] In an embodiment, the layer comprising PVOH, the bonding layer and the moisture barrier layer are coextruded.

[0024] Polyvinyl alcohol (PVOH) coated papers are normally produced from aqueous solutions, through dispersion coating. The polymer is dissolved in water, which has great impact on viscosity. In practice, the polymer is used in relatively low concentrations (10-20 wt%). This put high requirements on the application methods and a high drying capacity to evaporate the water used to dissolve and carry the PVOH polymer. Sometimes multiple coating stations are necessary to obtain desired thickness for and pinhole free PVOH coatings.

[0025] The process for producing a multilayer barrier coating including a layer comprising PVOH made from an aqueous solution, is thus requires extra process step for multiple application of the water based PVOH solution, drying and is therefore energy intensive. By applying the PVOH by co-extrusion coating together with the bonding layer and / or the moisture barrier layer, for example from melt, there is no need for any extra process step or any additional energy intensive process for drying out applied water. The process of coextrusion may be faster than a dispersion coating process.

[0026] By coextrusion coating with a polymer it is easier to steer coating and thickness of the layers to secure a pinhole free coating to get desired properties for the multilayer barrier and to facilitate an easier recycling.

[0027] In addition, coextrusion reduces the number of pinholes in the layer comprising PVOH, compared to a layer comprising PVOH obtained by dispersion coating.

[0028] In a second aspect, the invention relates to a laminated packaging sheet material for a container, the sheet material comprising as layers of a layer sequence, a paperboard layer, a layer comprising polyvinyl alcohol (PVOH), a bonding layer and a moisture barrier layer; wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater.

[0029] The skilled person will understand that the terms laminated packaging sheet material, laminate, sheet material and laminate sheet material are synonyms.

[0030] In an embodiment, the sheet material comprises as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material, the paperboard layer, the layer comprising polyvinyl alcohol (PVOH), the bonding layer and the moisture barrier layer.

[0031] In an embodiment, the sheet material comprises as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material, the moisture barrier layer, the bonding layer, the layer comprising polyvinyl alcohol (PVOH), and the paperboard layer.

[0032] In an embodiment, the sheet material comprises as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material, a first moisture barrier layer, a first bonding layer, a first layer comprising polyvinyl alcohol (PVOH), a paperboard layer, a second layer comprising polyvinyl alcohol (PVOH), a second bonding layer and a second moisture barrier layer.

[0033] In an embodiment, the laminated packaging sheet material may further comprise an additional gas barrier layer made from a composition mainly comprising a polymer selected from the group consisting of ethylene vinyl alcohol (EVOH ), polyvinyl alcohol (PVOH), polyvinylidene chloride (PVDC), polyamide (PA), polylactic acid, cellulose derivatives, polysaccharides, polyhydroxyalkanoates (PHA), polysaccharide derivatives, graphene and combinations thereof. In an embodiment, the grammage of the additional gas barrier layer may be under 16 g / m2. In an embodiment, the grammage of the gas barrier layer may be under 14 g / m2, under 12 g / m2, under 10 g / m2, under 8 g / m2, under 6 g / m2, under 5 g / m2, or under 4 g / m2.

[0034] In an embodiment, the grammage of the additional gas barrier layer may be comprised between 1 g / m2and 16 g / m2. In an embodiment, the grammage of the gas barrier layer may be comprised between 2 g / m2 and 10 g / m2, between 2 g / m2 and 7 g / m2, or between 3 g / m2 and 5 g / m2.

[0035] Here the term mainly comprising may be interpreted as comprising at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or at least 99% of the material in weight.

[0036] In an embodiment, the laminated packaging sheet material may not comprise an additional gas barrier layer.

[0037] In an embodiment, the laminated packaging sheet material may comprise a metalized layer.

[0038] In an embodiment, the laminated packaging sheet material may comprise an aluminium foil layer.

[0039] In an embodiment, the laminated packaging sheet material may comprise an intermediate layer between the paperboard layer and the layer comprising PVOH, wherein the intermediate layer comprises a polymer binder material and a filler.

[0040] In an embodiment of the laminated packaging sheet material, the intermediate layer may directly be adjacent to the paperboard layer.

[0041] In an embodiment of the laminated packaging sheet material, the intermediate layer may directly be adjacent to the layer comprising PVOH.

[0042] Here the skilled person will understand that when a layer is directly adjacent to another layer means that there is no layer between the two adjacent layers, on other words, they are in direct contact.

[0043] Typically, “paperboard” refers to a paper based substrate comprising fibres including, at least in part, cellulose fibres. A typical paperboard substrate used for packaging material comprises at least one ply, preferably several plies, e.g. a back ply, a top ply and one or several middle plies. Paperboard may comprise chemi-thermomechanical pulp (CTMP) and / or sulphate pulp. Typical paperboard grades may be solid bleached sulphate (SBS) and coated unbleached kraft (CUK). To improve the surface properties of the paperboard layer, the paperboard layer may be calendered and or smoothened with a planarisation layer consisting of surface sizes and / or pigment coating.

[0044] In a preferred embodiment, the paperboard layer has a eucalyptus fibre layer on one or both surfaces of the paperboard layer.

[0045] When describing the sheet material comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material, the internal side is the side refers to the side intended to face the inside of the container.

[0046] In an embodiment, the filler of the intermediate layer may be an inorganic filler, preferably a kaolin clay, a bentonite clay, talcum particles, silicate and / or calcium carbonate.

[0047] In an embodiment, the polymer binder material of the intermediate layer may be selected from the group consisting of vinyl acetate, styrene-butadiene copolymer (SB) latex, styrene acrylate copolymer (SA) latex, other latexes of acrylate polymers and copolymers, such as vinyl acrylic copolymer latex and vinyl acetate acrylate copolymer latex, and of bio-based polymer materials.

[0048] In an embodiment, the intermediate layer may comprise from 1 wt% to 90 wt% of filler.

[0049] In an embodiment, the intermediate layer may comprise from 1 wt% to 80 wt%, 1 wt% to 70 wt%, 1 wt% to 60 wt%, 1 wt% to 50 wt%, 1 wt% to 40 wt%, 1 wt% to 30 wt% or 1 wt% to 20 wt% of filler.

[0050] In an embodiment, the intermediate layer may comprise from 10 wt% to 90 wt%, 20 wt% to 80 wt%, 30 wt% to 80 wt%, 40 wt% to 80 wt% or 50 wt% to 80 wt% of filler.

[0051] In an embodiment, the intermediate layer may comprise from 10 wt% to 99 wt% of binder.

[0052] In an embodiment, the intermediate layer may comprise from 20 wt% to 99 wt%, 30 wt% to 99 wt%, 40 wt% to 99 wt%, 50 wt% to 99 wt% , 60 wt% to 99 wt%, 70 wt% to 99 wt% or 80 wt% to 99 wt% of binder.

[0053] In an embodiment, the intermediate layer may comprise from 10 wt% to 90 wt%, 20 wt% to 80 wt%, 20 wt% to 70 wt%, 20 wt% to 60 wt% or 20 wt% to 50 wt% of binder.

[0054] In an embodiment, the grammage of the intermediate layer may be comprised between 1 g / m2and 20 g / m2. In an embodiment, the grammage of the intermediate layer may be comprised between 2 g / m2and 15 g / m2, between 5 g / m2and 15 g / m2, between 10 g / m2and 15 g / m2. Grammages of papers were determined according to the official test method of ISO 536:2019 by the unit g / m2, while thickness and density were determined according to ISO 534:2011, by the units pm (m) and kg / m3, respectively.

[0055] In an embodiment, the intermediate layer may have a Bendtsen smoothness / roughness of less than 1000 ml / min. In an embodiment, the intermediate layer may have a Bendtsen smoothness / roughness of less than 800 ml / min, of less than 600 ml / min, of less than 500 ml / min, of less than 400 ml / min, or of less than 300 ml / min.

[0056] In an embodiment, the intermediate layer may have a Bendtsen smoothness / roughness of between 5 ml / min and 1000 ml / min, between 15 ml / min and 500 ml / min, between 50 ml / min and 300 ml / min.

[0057] The Bendtsen smoothness / roughness may be measure according to ISO 8791-2:2013.

[0058] In an embodiment of the container according to the first aspect of the invention, the moisture barrier layer may be made of a material comprising low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene linear low density polyethylene (mLLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), polypropylene (PP) or any blend thereof.

[0059] LDPE is a low density polyethylene with a density between 0.910 and 0.925 g / cm3.

[0060] LLDPE is a linear low density polyethylene with a density between 0.915 and 0.925 g / cm3.

[0061] MDPE is a medium density polyethylene with a density between 0.926 and 0.935 g / cm3.

[0062] HDPE is a high density polyethylene with a density greater or equal to 0.936 g / cm3.

[0063] In an embodiment of the container, the moisture barrier layer may be made of a material having a density equal to or over 0.926 g / cm3. In another embodiment of the container, the polymeric intermediate layer is made of a material having a density equal to or over 0.936 g / cm3. In another embodiment of the container, the polymeric intermediate layer is made of a material having a density equal to or over 0.941 g / cm3.

[0064] In an embodiment of the container, the moisture barrier layer may comprise 20% to 80% HDPE; 30% to 70% HDPE or 40% to 60% HDPE.

[0065] In an embodiment of the container, the moisture barrier layer may comprise 20% to 80% LDPE; 30% to 70% LDPE or 40% to 60% LDPE.

[0066] In an embodiment of the container, the moisture barrier layer may comprise 20% to 80% LLDPE; 30% to 70% LLDPE or 40% to 60% LLDPE.

[0067] In an embodiment of the container, the moisture barrier layer may comprise 20% to 80% mLLDPE; 30% to 70% mLLDPE or 40% to 60% mLLDPE. In an embodiment of the container, the moisture barrier layer may comprise 20% to 80% MDPE; 30% to 70% MDPE or 40% to 60% MDPE.

[0068] In an embodiment of the container, the moisture barrier layer may comprise 20% to 80% PP; 30% to 70% PP or 40% to 60% PP.

[0069] In an embodiment of the container, the moisture barrier layer may consist of a blend of HDPE and LDPE.

[0070] In an embodiment of the container, the moisture barrier layer may consist of a blend of HDPE and LLDPE.

[0071] In an embodiment of the container, the moisture barrier layer may consist of a blend of HDPE and mLLDPE.

[0072] In an embodiment of the container, the moisture barrier layer may consist of a blend of HDPE and MDPE.

[0073] In an embodiment of the container, the moisture barrier layer may consist of a blend of MDPE and LDPE.

[0074] In an embodiment of the container, the moisture barrier layer may consist of a blend of LDPE and LLDPE.

[0075] In an embodiment of the container, the moisture barrier layer may consist of a blend of LDPE and mLLDPE.

[0076] In an embodiment of the container, the moisture barrier layer may consist of a blend of PP and LDPE, PP and LLDPE, PP and mLLDPE, PP and MDPE or PP and HDPE.

[0077] In an embodiment of the container, the moisture barrier layer may consist of a blend HPDE and two other polymers chosen from LDPE, PP, MDPE, LLDPE and mLLDPE.

[0078] In an embodiment of the container, the moisture barrier layer may consist of a blend HPDE, LLDPE and LDPE

[0079] In an embodiment, the grammage of the moisture barrier layer may be under 60 g / m2. In an embodiment, the grammage of the moisture barrier layer may be under 50 g / m2, under 40 g / m2, under 30 g / m2, under 24 g / m2, under 22 g / m2, under 20 g / m2, under 18 g / m2, under 16 g / m2, under 14 g / m2, under 12 g / m2, under 10 g / m2, or under 8 g / m2.

[0080] In an embodiment, the grammage of the moisture barrier layer may be comprised between 5 g / m2and 60 g / m2. In an embodiment, the grammage of the moisture barrier layer may be comprised between 6 g / m2 and 50 g / m2, between 6 g / m2 and 40 g / m2, between 6 g / m2 and 30 g / m2, between 6 g / m2 and 20 g / m2, or between 8 g / m2 and 16 g / m2. In a third aspect, the invention relates to a container for holding a pourable food product, the container comprising a laminated packaging sheet material according to the second aspect of the invention which is folded to form said container.

[0081] In a fourth aspect, the invention relates to a blank for making the container according to the third aspect of the invention.

[0082] In a fifth aspect, the invention relates to a method of manufacturing a multilayer barrier coating comprising the step of co-extruding as layers of a layer sequence, a layer comprising polyvinyl alcohol (PVOH), a bonding layer and a moisture barrier layer; wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater.

[0083] In a sixth aspect, the invention relates to a method of manufacturing a laminated packaging sheet material comprising the steps of co-extruding a multilayer barrier coating comprising as layers of a layer sequence, a layer comprising polyvinyl alcohol (PVOH), a bonding layer and a moisture barrier layer; wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater; and applying the multilayer barrier coating to a paperboard layer; wherein the multilayer barrier coating is applied at a temperature over the melting temperature of the layer comprising PVOH.

[0084] In an embodiment, the multilayer barrier coating may be applied at a temperature between 150°C to 225°C; 160°C to 225°C; 170°C to 220°C or 180°C to 220°C.

[0085] The moisture barrier layer has an average thickness t53, and the layer comprising PVOH has an average thickness t51.

[0086] In an embodiment, t53 is greater or equal to t51, t53 is greater or equal to two times t51, t53 is greater or equal to five times t51, and t53 is greater or equal to ten times t51.

[0087] Here, by having the combination of these different thicknesses, the layer comprising PVOH stays warmer longer during coextrusion and application, which ensures a better adhesion to the next layer, for example the paperboard layer. Short description of the drawings

[0088] In the following description this invention will be further explained by way of exemplary embodiments shown in the drawings:

[0089] Fig. 1 is a cross-sectional view of a laminate known in the art.

[0090] Fig. 2 is a perspective view from above of a gable-top container with a pour spout fitment applied thereto.

[0091] Fig. 3 is a cross-sectional view of an example of the coating of the present invention.

[0092] Fig. 4 is a cross-sectional view of a first example of the laminate of the present invention.

[0093] Fig. 5 is a cross-sectional view of a second example of the laminate of the present invention.

[0094] Fig. 6 is a cross-sectional view of a third example of the laminate of the present invention.

[0095] Fig 7 is describing the reference disintegration / repulping over time.

[0096] Fig .8 is describing the disintegration / repulping over time of the present invention.

[0097] It should be understood that the drawings are not intended to limit the invention to the subjectmatter depicted in the drawings.

[0098] In the drawings, like reference numerals have been used to indicate common parts, elements or features unless otherwise explicitly stated or implicitly understood by the context.

[0099] Detailed description

[0100] In the following embodiments of containers will be described in more detail with reference to the drawings. However, it is specifically intended that the invention as defined in the claims is not limited to the embodiments and illustrations contained herein but includes modified forms of the embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the claims.

[0101] FIG. 1 shows a schematic cross-sectional view of a known laminate comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material, a paperboard layer 30 made of bleached board fibers, and a moisture barrier layer 53 made of LDPE.

[0102] This laminate may comprise further layer, on an internal side of the moisture barrier layer 53, such as a gas barrier layer 45 for example made of Alu foil.

[0103] The laminate structure of FIG. 1, may be used to make packaging, using any kind of an opening arrangement. A typical container is illustrated in FIG. 2.

[0104] FIG. 2 illustrates a container 1 following filling and top-sealing. A pour spout fitment 3 has been applied to the top surface of the panel 2, the pour spout fitment 3 consisting of a flanged pour spout 5, a screw cap 7 on the pour spout.

[0105] It is an object of the invention, to modify known laminate structure in order to obtain a laminate structure that will be more environmental friendly, while retaining the necessary properties to be usable in the fabrication of container for holding a pourable food product.

[0106] This objective is achieved by providing a multilayer barrier coating 50 comprising as layers of a layer sequence, a layer comprising polyvinyl alcohol (PVOH) 51, 51a, 51b, a bonding layer 52, 52a, 52b and a moisture barrier layer 53, 53a, 53b; wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater and applying the multilayer barrier coating 50 on a paperboard layer 30.

[0107] After use, when container is recycled, the paperboard layer 30 will be easier to separate from the moisture barrier layer(s) 53, 53a, 53b. This will allow for these layers to be recycled separately, which ensures a better process.

[0108] Fig. 3 shows an example of the inventive multilayer barrier coating 50, comprising a layer 51, comprising PVOH, a bonding layer 52, comprising a modified polyethylene, here a maleic anhydride grafted PE, such as Yparex 9207, and a moisture barrier layer 53, comprising LDPE. The layer comprising PVOH has a degree of hydrolysis of 70% or greater.

[0109] In this example, the layer 51 comprising PVOH layer 50 has a grammage of 4 g / m2. The moisture barrier layer 53 has a grammage of 20 g / m2. Fig. 4 shows a first example of the inventive laminate, comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material 100, a layer of duplex paperboard 30, and the inventive multilayer barrier coating 50 of fig. 3.

[0110] In other words, the inventive laminate, comprises as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material 100, a layer of duplex paperboard 30, a layer 51, comprising PVOH, a bonding layer 52, comprising a modified polyethylene, here a maleic anhydride grafted PE, such as Yparex 9207, and a moisture barrier layer 53, comprising LDPE. The layer comprising PVOH has a degree of hydrolysis of 70% or greater.

[0111] Fig. 5 shows a second example of the inventive laminate, comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material 100, a first inventive multilayer barrier coating 50a as shown in fig. 3 (here in the reversed order compared to figure 3), a layer of duplex paperboard 30, and a second inventive multilayer barrier coating 50b as shown in fig. 3.

[0112] In other words, the inventive laminate, comprises as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material 100, a first moisture barrier layer 53a, comprising LDPE, a first bonding layer 52a, comprising a modified polyethylene, here a maleic anhydride grafted PE, such as Yparex 9207, a first layer 51a, comprising PVOH, a layer of duplex paperboard 30, a layer 51b, comprising PVOH, a bonding layer 52b, comprising a modified polyethylene, here a maleic anhydride grafted PE, such as Yparex 9207, and a second moisture barrier layer 53b, comprising LDPE.

[0113] The first and second layers 51a, 51b comprising PVOH has a degree of hydrolysis of 70% or greater.

[0114] Fig. 6 shows a third example of the inventive laminate, comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material 100, a first inventive multilayer barrier coating 50a as shown in fig. 3 (here in the reversed order compared to figure 3), a first intermediate layer 40a, a layer of duplex paperboard 30, a second intermediate layer 40b and a second inventive multilayer barrier coating 50b as shown in fig. 3.

[0115] In other words, the inventive laminate, comprises as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material 100, a first moisture barrier layer 53a, comprising LDPE, a first bonding layer 52a, comprising a modified polyethylene, here a maleic anhydride grafted PE, such as Yparex 9207, a first layer 51a, comprising PVOH, a first intermediate layer 40a, a layer of duplex paperboard 30, a layer 51b, comprising PVOH, a bonding layer 52b, comprising a modified polyethylene, here a maleic anhydride grafted PE, such as Yparex 9207, a second intermediate layer 40b and a second moisture barrier layer 53b, comprising LDPE.

[0116] The first and second layers 51a, 51b comprising PVOH have a degree of hydrolysis of 70% or greater. The first and second intermediate layer 40a, 40b are made of clay. The first and second intermediate layer 40a, 40b each have a grammage of 15 g / m2.

[0117] The internal surface of the paperboard layer 30 is uneven (high Bendtsen smoothness / roughness usually over 1000 ml / min), which is why the first and second layers 5 la, 5 lb comprising PVOH need to be sufficiently thick in order to ensure good enough separation properties when placed directly on the paperboard layer 30.

[0118] In addition, the first and second layers 51a, 51b comprising PVOH also have barrier properties. The laminate structure may also comprise an additional barrier layer 45, for example placed between the paperboard layer 30 and the first and / or second layers 51a, 51b. Typical gas barrier layer in such laminates have a grammage of at least 18 g / m2to ensure a sufficient gas barrier property.

[0119] By adding the intermediate layer 40, the unevenness of the paperboard layer is reduced. In other words, the Bendtsen smoothness / roughness of the intermediate layer 40 (on its internal side) is lower than the Bendtsen smoothness / roughness of the paperboard layer 30 (on its internal side). Therefore, the first and / or second layers 51a, 51b comprising PVOH, and or the optional additional layer 45 may have a reduced thickness / density / grammage while presenting similar or even superior barrier properties, i.e. that at least satisfy the requirements to be used in container for holding a pourable food product. It is worth noting that, without the intermediate layer 40, filled containers comprising a reduced gas barrier layer 50 present a decreased shell life.

[0120] Suitable examples of adhesive polymer are Admer NF837E from Mitsui, Admer AT3078E from Mitsui, Yparex 9408 from The Compound Company BV and Yparex 9207 from The Compound Company BV.

[0121] Suitable examples of HDPE are CG8410 from Borealis (0.941 g / cm3), CG8410 from Borealis (0.962 g / cm3), Dowlex 2006G from Dow (0.961 g / cm3), Trucoat MC2004 from Westlake (0.946 g / cm3), Rigidex HD6070FA (0.960 g / cm3).

[0122] Suitable examples of LDPE are CA 8200 from Borealis (0.920 g / cm3), LDPE PT 7007 from Dow (0.918 g / cm3), LDPE LD 258 from ExxonMobil (0.919 g / cm3), 19N430 from INEOS (0.920 g / cm3).

[0123] Suitable examples of mLLDPE are Queo 0210 from Borealis, Queo 1019 from Borealis, Elite 5800G from Dow, Affinity PT 1451G1 from Dow, Exceed 0019XC from ExxonMobil, and Eltex PF1315AA from INEOS.

[0124] The gas barrier properties of the laminate structure may be evaluated by measuring the oxygen transmission rate (OTR).

[0125] The OTR is evaluated using ASTM 1927, at 23°C and at different relative humidity (RH) : 50, 70, and 90% RH on both sides of the sample, with a cell area of 50 cm2 and a sample orientation with the barrier towards the carrier gas N2. The moisture barrier properties of the laminate structure may be evaluated by measuring the water vapor transmission rate (WVTR).

[0126] The WVTR is evaluated using ASTM F1249, at 23°C and at different relative humidity (RH) : 90% and 100% RH on both sides of the sample and a sample orientation with the barrier to the dry side and towards the carrier gas N2.

[0127] The laminate structures presented in fig. 4 to 6 all present sufficient gas barrier properties for use in container for holding a pourable food product.

[0128] The risk of leakage may be evaluated using what will be referred to as a dye test.

[0129] In the dye test, a large number of containers, for example 100, are cut in two halves and thoroughly rinsed. Both halves of all the containers are filled with a solvent containing a dye. Both halves are then stored for 12h, after which a visual inspection is realized. If dye spots can be seen from the outside, then the half container is considered to leak. The risk of leakage, i.e. the percentage of leaking containers, i.e. containers showing die spots is then calculated.

[0130] The laminate structure of fig. 4 to 6 does not present any significant risk of leakage.

[0131] In addition, the laminate structure of fig. 4 to 6 present improved recyclability properties.

[0132] The combination of a water-soluble intermediate layer 40a, 40b and the layer comprising PVOH 51a, 51b is particularly advantageous and present further improved recyclability properties.

[0133] Examples

[0134] First laminated packaging sheet material

[0135] The first laminated packaging sheet material is a reference material, and comprised, as as layers of a layer sequence, a moisture barrier layer (low density polyethylene 12 g / m2), a paperboard layer (duplex paperboard 268 g / m2), and a moisture barrier layer (low density polyethylene 24 g / m2);

[0136] Second laminated packaging sheet material

[0137] The second laminated packaging sheet material comprised, as as layers of a layer sequence, a moisture barrier layer (low density polyethylene 14 g / m2), a paperboard layer (duplex paperboard 268 g / m2), a PVOH layer (6 g / m2), a bonding layer (Yparex 9411, 4 g / m2), and a moisture barrier layer (low density polyethylene 20 g / m2);

[0138] Third laminated packaging sheet material

[0139] The third laminated packaging sheet material comprised, as as layers of a layer sequence, a moisture barrier layer (low density polyethylene 14 g / m2), a paperboard layer (duplex paperboard 268 g / m2), a PVOH layer (6 g / m2), a bonding layer (Yparex 9411, 4 g / m2), and a moisture barrier layer (low density polyethylene 14 g / m2);

[0140] Fourth laminated packaging sheet material

[0141] The fourth laminated packaging sheet material comprised, as as layers of a layer sequence, a moisture barrier layer (low density polyethylene 14 g / m2), a paperboard layer (duplex paperboard 268 g / m2), a PVOH layer (3 g / m2), a bonding layer (Yparex 9411, 4 g / m2), and a moisture barrier layer (low density polyethylene 10 g / m2);

[0142] In the second, third and fourth laminated packaging sheet material, the PVOH had a degree of hydrolysis of 70% or greater. The PVOH was Hydropol™ 55218 provided from Aquapak.

[0143] All the laminated packaging sheet material were individually repulped using an automated pulper, using a medium to high consistency pulping process.

[0144] The reference material, the first laminated packing material, took about 30-35 minutes, see Fig 7, to achieve a complete separation of the different layers and fiber disintegration, whereas for the second, third and fourth laminated packaging material, it only took about 5-10 minutes, as exemplified in Fig8.

[0145] The disintegration graphs figures 7 and 8 illustrates the energy uptake when the piece of laminate is subjected to shear force in water. Before fibers are starting to disintegrate from the laminate there is a lag time where the laminate is predominantly agitated in a water phase with limited fiber release. When fiber disintegration occurs, viscosity and effect needed to agitate the solution increase rapidly to reach a new plateau where fiber separation and disintegration of fiber flocks occurs. The shorter lag phase demonstrates the faster fiber separation with a release layer that overall have the potential to shorter process cycle time and to reduced energy need for fiber separation.

[0146] In addition, after separating the fiber fraction from the polymer fraction, it is noted that for the second, third and fourth laminated packaging material the polymer fraction is made of bigger pieces than for the first laminated packing material after the separation. Bigger pieces are advantageous as they are easier to separate from the fiber fraction.

[0147] In other words, the inventive laminated packing material allow for a quicker separation, produce a cleaner fiber fraction, and reduce the breakup (fractionation) of the polymer layers. The repulping process for the inventive material consumes also less energy than for the reference material to obtain the same effect.

Claims

CLAIMS1. A multilayer barrier coating (50) comprising as layers of a layer sequence, a layer (51, 51a, 51b) comprising polyvinyl alcohol (PVOH), a bonding layer (52, 52a, 52b) and a moisture barrier layer (53, 53a, 53b); wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater.

2. The multilayer barrier coating (50) according to claim 1, wherein the layer (51, 51a, 51b) comprising PVOH has a melting point over the melting point of the moisture barrier layer (53, 53a, 53b).

3. The multilayer barrier coating (50) according to claim 1 or 2, wherein the bonding layer (52, 52a, 52b) is made of functionalized polyethylene.

4. The multilayer barrier coating (50) according to any one of claims 1 to 3, wherein the layer comprising PVOH (51, 51a, 51b), the bonding layer (52, 52a, 52b) and the moisture barrier layer (53, 53a, 53b) are coextruded.

5. A laminated packaging sheet material (100) for a container, the sheet material (100) comprising as layers of a layer sequence, a paperboard layer (30), a layer comprising polyvinyl alcohol (PVOH) (51, 51a, 51b), a bonding layer (52, 52a, 52b) and a moisture barrier layer (53, 53a, 53b); wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater.

6. The laminated packaging sheet material (100) according to claim 5, the sheet material (100) comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material (100), the paperboard layer (30), the layer comprising polyvinyl alcohol (PVOH) (51, 51b), the bonding layer (52, 52b) and the moisture barrier layer (53, 53b).

7. The laminated packaging sheet material (100) according to claim 5, the sheet material (100) comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material (100), the moisture barrier layer (53, 53a), the bonding layer (52, 52a), the layer comprising polyvinyl alcohol (PVOH) (51, 51a), and the paperboard layer (30).

8. The laminated packaging sheet material (100) according to any one of claim 5 to 7, the sheet material (100) comprising as layers of a layer sequence, in a direction from an external side to an internal side of the sheet material (100), a first moisture barrier layer (53a), a first bonding layer (52a), a first layer comprising polyvinyl alcohol (PVOH) (51a), a paperboard layer (30), a second layer comprising polyvinyl alcohol (PVOH) (51b), a second bonding layer (52b) and a second moisture barrier layer (53b).

9. The laminated packaging sheet material (100) according to any one of claim 5 to 8, wherein the laminated packaging sheet material (100) further comprises an intermediate layer (40) between the paperboard layer (30) and the layer comprising PVOH (51, 51a, 5 lb) and wherein the intermediate layer comprises a polymer binder material and a filler.

10. The laminated packaging sheet material (100) according to any one of claim 5 to 9, wherein the intermediate layer (40) is directly adjacent to the paperboard layer (30) on one side and is directly adjacent to the layer comprising PVOH (51, 51a, 51b) on the other side.

11. The laminated packaging sheet material (100) according to any one of claim 5 to 10, wherein the filler of the intermediate layer (40) is an inorganic filler.

12. The laminated packaging sheet material (100) according to any one of claim 5 to 11, wherein the filler of the intermediate layer (40) is a kaolin clay, a bentonite clay, talcum particles, silicate and / or calcium carbonate.

13. The laminated packaging sheet material (100) according to any any one of claim 5 to 12, wherein the polymer binder material of the intermediate layer (40) is selected from the group consisting of vinyl acetate, styrene-butadiene copolymer (SB) latex, styrene acrylate copolymer (SA) latex, other latexes of acrylate polymers and copolymers, such as vinyl acrylic copolymer latex and vinyl acetate acrylate copolymer latex, and of biobased polymer materials.

14. The laminated packaging sheet material (100) according to any one of claim 5 to 13, wherein the intermediate layer (40) comprises from 10 to 90 wt% of filler.

15. The laminated packaging sheet material (100) according to any one of claim 5 to 14, wherein the grammage of the intermediate layer (40) is comprised between 1 and 20 g / m2.

16. The laminated packaging sheet material (100) according to any one of claim 5 to 15, wherein the moisture barrier layer (53), is made of a material comprising LDPE, LLDPE, mLLDPE, MDPE, HDPE, PP or any blend thereof.

17. The laminated packaging sheet material (100) according to any one of claim 5 to 16, wherein the grammage of the moisture barrier layer (53) is equal to or under 60 g / m2.

18. A container (1) for holding a pourable food product, the container (1) comprising a laminated packaging sheet material (100) according to any one of claim 5 to 17.

19. A blank for making the container according to claim 18.

20. A method of manufacturing a multilayer barrier coating (50) comprising the step ofco-extruding as layers of a layer sequence, a layer comprising polyvinyl alcohol (PVOH) (51), a bonding layer (52) and a moisture barrier layer (53); wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater.

21. A method of manufacturing a laminated packaging sheet material (100) comprising the steps of co-extruding a multilayer barrier coating (50) comprising as layers of a layer sequence, a layer comprising polyvinyl alcohol (PVOH) (51, 51a, 51b), a bonding layer (52, 52a, 52b) and a moisture barrier layer (53, 53a, 53b); wherein the layer comprising PVOH has a degree of hydrolysis of 70% or greater; and applying the multilayer barrier coating (50) to a paperboard layer (30); wherein the multilayer barrier coating (50) is applied at a temperature over the melting temperature of the PVOH layer (51).

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