Barrier laminate

Abstract

A flexible barrier laminate comprising a cellulose fiber-based substrate layer (1), a barrier layer (2) comprising an electrospun fiber web, deposited on one side of the substrate layer.

Description

[0001] BARRIER LAMINATE

[0002] The present invention relates to a barrier laminate. The invention further relates to a packaging product comprising the barrier laminate. The invention further relates to a method to manufacture the barrier laminate.

[0003] Background of the invention

[0004] Consumer goods, such for example food products including frozen confectionary, liquid and dry bouillon, soup, sauce products; savoury snack products, instant meals, but also soap bars, laundry detergent, etc, are typically packaged before they are used by the consumer. Besides marketing purposes, depending on the consumer product, the packaging provides structure to the product and / or keeps it in place, and protects the product against external influences that may affect the quality, including light, water, and air, which results in the presence of several barrier materials that are included in a packaging material, depending on the product need. In addition, the consumer product itself may affect the packaging material, because of for example ingredients like water, fat, salts, corrosive alkaloids etc., and the packaging material typically may need to be resistant against such influences to ensure proper protection of the packaged product. For this reason, packaging materials for consumer products typically are laminates of different materials, such as different polymer materials (plastics), and metal, such as aluminium.

[0005] With increasing emphasis on environmentally friendlier packaging materials, the use of non- petroleum-based substrate layers, such as paper, which function e.g. as a structural base of a barrier laminate, gained interest. The substrate layer, such as paper, obviously is typically thin, to allow high flexibility, for example during packaging processes and in packaging lines. In the case of paper, paper provides to a certain extent texture to a packaged consumer product, its barrier properties for external influences such as water are limited, and it can be easily damaged upon contact with fat or water from the packaged consumer product. In the art, laminates comprising paper and petroleum-based polymers are found as a solution to provide barrier properties to the paper material.

[0006] Barrier laminates can be used for example to produce flexible packaging products, such as pouches or doy packs. To do this, the barrier laminate is typically folded and sealed on itself to form a bag-like structure. Alternatively, individual pieces of barrier laminate can be sealed to each other, to result in a bag-like structure, such as a pouch or a doypack. After filling of the packaging product, the packaging product may be closed in a procedure that involves a further sealing step. To effect such sealing steps during manufacturing of the packaging product and closing thereof, barrier laminates typically comprise a sealing layer. This is a layer in the barrier laminate that connects to another layer upon applying heat.

[0007] It was realized by the present inventors, that one of the complications observed in the context of barrier laminates free from petroleum-sourced materials, was the integrity of the seals in a packaging product produced from the flexible barrier laminate. For optimal protection of the consumer product, the sealed areas in a packaging product, typically located at the borders of the packaging product, should not open or leak during storage and transport. In particular when the substrate layer in the barrier laminate is paper-based, integrity of seals is a challenge, but is of paramount importance.

[0008] A need therefore was recognized for a flexible barrier laminate, substantially free from barrier layers of petroleum-sourced materials, and which comprises a substrate layer and a barrier layer, which laminate allows for manufacturing of packaging products for consumer products, and which provides proper integrity during use (transport and storage)with proper sealing. Preferably the number of barrier layers is as few as possible and is preferably a total of one barrier layer and preferably no layer applied over that barrier layer for sealing purposes.

[0009] EP3907078 A1 relates to a biodegradable container comprising a thermoformable structural layer and optionally an adhesive barrier layer.

[0010] WO2011 / 114311 A1 relates to a method for providing a surface of a fiber based substrate wihta barrier layer wherein the barrier layer is formed by depositing nanofibers on the surface by the use of electrospinning or melt spinning and wherein the film is formed by post treatment of substrate.

[0011] Summary of the invention

[0012] Surprisingly, this objective could be met by the present invention, which relates in a first aspect to a flexible barrier laminate comprising: a. A cellulose fiber-based substrate layer (1), b. A barrier layer (2) comprising an electrospun fiber web, deposited on one side of the substrate layer, wherein the barrier layer (2) has a thickness of between 1 and 35, preferably between 1 and 30, and more preferably between 1 and 25 micrometer, wherein the barrier layer (2) is the only barrier layer, preferably the only layer, applied at the side where the barrier layer (2) is applied, and wherein the barrier layer comprises one or more of polyhydroxyalkanoates, fibroin protein, prolamine, chitin polysaccharide, phenolic polymer, and mixtures thereof, with the proviso that if fibroin protein is used, it is used in combination with another material from the list.

[0013] In a second aspect, the present invention relates to a packaging product to package a consumer product, the packaging product comprising the barrier laminate according to the invention. Preferably, the packaging product is a wrapper or sachet.

[0014] In a third aspect, the present invention relates to a method to provide a packaging laminate according to the invention, the method comprising the steps of: a) Providing a cellulose fiber-based substrate layer (1). b) Depositing fibers using electrospinning to form a fiber network, c) Laminating the deposited fiber network, to result in a barrier laminate according to the invention.

[0015] In a fourth aspect, the invention relates to a method to manufacture a packaging product of the third aspect of the invention.

[0016] In a fifth aspect, the present invention relates to the use of an electrospun fiber layer, positioned on cellulose fiber-based substrate layer to enhance the sealing properties of the barrier laminate.

[0017] Barrier laminates comprising a substrate and an electrospun layer have been described in the art. The inventors are not aware of any cellulose fiber-based barrier laminate that comprises an electrospun barrier layer, and wherein enhanced seal force has been recognized, in particular, no packaging product is known which is manufactured from such barrier laminate which is heat- sealed together.

[0018] Description of the Drawing

[0019] Figure 1 shows a schematic diagram of the process of electrospinning of fibres. Detailed description

[0020] The barrier laminate of the present invention comprises two layers. It includes a substrate layer (1) and a barrier layer (2) comprising a fiber network, positioned on top of the substrate layer. The barrier laminate typically is a film comprising at least two layers, as described herein, a substrate layer and a barrier layer. The film provides a barrier function, e.g. against water vapour or oxygen or both, to protect the content of a packaging product prepared from the film, i.e. from the barrier laminate. It was found that the barrier layer (2) being electrospun resulted in significantly enhanced sealing properties of the barrier laminate, wherein the thickness of the individual layers is of relevance. The advantage achieved in this manner is to provide a barrier laminate with reduced risk for detachment of barrier laminate after sealing, e.g. when a packaging product was formed from the barrier laminate, detachment of sealed barrier laminate may in particularly form a risk in cellulose fiber-based barrier laminates, in particular when the barrier laminate is used in packaging products containing e.g. consumer goods and therefore exposed to forces e.g. during cutting the material or tearing it during opening of such packaging products. The advantage achieved in this manner is to provide a barrier laminate which has enhanced seal properties while it does not rely on materials that are sourced from petroleum. Such materials are preferably absent from the substrate layer, connection layer and sealing layer and more preferably are absent from the barrier laminate.

[0021] The barrier laminate is flexible. It can typically be easily bended without damaging the integrity. The laminate is not rigid. The barrier laminate is typically a laminate comprising from 2 to 5, preferably 3 or 4 layers. It is preferred, that the barrier laminate consists of 2 layers at the side of the barrier laminate where the barrier layer (2) is located (typically facing the packaged product when in use), being the substrate layer (1), and the barrier layer (2). At the other side of the substrate layer (typically facing the outside world when in use) can preferably be one or two other layers deposited, such as an ink layer (3) and an over varnish layer (4).

[0022] Substrate layer

[0023] The barrier laminate comprises a substrate layer (1). The substrate layer preferably is a cellulose fiber-based layer. More preferably, the substrate layer is paper-based or cardboard based, most preferably paper based and more preferably is paper. The flexible barrier laminate comprises preferably a total of one, or a total of two, but preferably a total of one layer of paper. Paper typically comprises cellulose fibers. The cellulose fiber-based layer preferably comprises paper, or more preferably is paper with a grammage of between 40 and 100 gram / m2, preferably of 50 to 90 gram / m2, even more preferably from 50 to 80 gram / m2and most preferably of 50 to 70 gram / m2. This provides suitable rigidity to the final packaging product to contain a consumer product, such as for example a wrapper or sachet, whereas it can be suitably transported in a packaging line, e.g. over rollers.

[0024] In view of the aim of providing a barrier laminate with less impact on the environment, it may be preferred, that paper is present in an amount of more than 80 wt%, more preferably more than 85 wt%, based on the total weight of the barrier laminate. Preferably, paper fibers constitute more than 80 wt%, more preferably more than 85 wt%, based on the total weight of the barrier laminate. It may be preferred, that the amount of polymer, for example the amount of plastic, or typically the total amount of petroleum based plastic, is below 20 wt%, preferably below 15 wt%, based on the weight of the barrier laminate. It can be for example from 9 to 20 wt%, more preferred from 11 to 15 wt%. A paper content of more than 80 wt% is typically considered to meet the criteria for recyclability in many countries.

[0025] Barrier layer

[0026] A barrier layer (2) is present within the barrier laminate. The barrier layer is preferably directly deposited on the substrate layer. It is preferred, that the barrier layer (2) is the only barrier layer, preferably the only layer, which is present at the side of the substrate layer (1) where the barrier layer is applied.

[0027] The barrier layer comprises a fiber network. The fibers in the fiber network preferably have a diameter (shortest dimension) of between 250 and 1000 nm, more preferably of between 300 and 700 nm and most preferably of between 300 and 500 nm.

[0028] The barrier layer preferably has a density of from 5 to 50 g / m2, preferably 5 to 30 g / m2, preferably from 5 to 10 g / m2. The thickness of the barrier layer is from 1 to 35 micrometers, preferably from 1 to 30 micrometers, more preferably from 1 to 25 micrometers, even more preferably 4 to 25 micrometres, and even more preferably from 4 to 15, and even more preferably from 5 to 10 micrometers. It was observed, that using the bio-degradable materials selected for the present invention, and when deposited on a cellulose-fiber based substrate layer, barrier and sealing properties could be assured when the thickness of the barrier layer was relatively thin, and most preferably below 25 microns. The materials in the barrier layer (2) preferably are not petroleum-based. The barrier layer may comprise filler particles. The barrier layer preferably comprises one or more materials selected from the group consisting of polyhydroxyalkanoates (PHA), fibroin proteins, pro-lamines, chitin polysaccharides, phenolic polymers, and mixtures thereof. Preferred polyhydroxyalkanoates in the context of the invention are selected from the group consisting of polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3- hydroxyhexanoate) (PHBH) and mixtures thereof. A preferred fibroin protein in the context of the invention is silk. A preferred pro-lamine in the context of the invention is zein. A preferred chitin polysaccharide in the context of the invention is chitin from shellfish and chitin from mushrooms. A preferred phenolic polymer in the context of the invention is lignin. The barrier layer (2) preferably comprises polyhydroxyalkanoates (PHA) or pro-lamines or mixtures thereof. This provides optimal sealing results when applied in paper / cardboard based flexible packaging products. It may be preferred, that next to polyhydroxyalkanoates (PHA) or pro-lamines or mixtures thereof, one or more materials are present selected from the group consisting of fibroin proteins, chitin polysaccharides, phenolic polymers, and mixtures thereof.

[0029] More preferably, the barrier layer comprises PHA, fibroin protein or pro-lamine. Even more preferably, the barrier layer comprises one or more selected from the group consisting of polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3- hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), silk, zein and mixtures thereof. Preferably, the barrier layer comprises one or more selected from the group consisting of polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3- hydroxyhexanoate) (PHBH), and zein, optionally combined with silk. PHB may result in relatively higher layer thickness, which may not be preferred. It could be preferred that no PHB layer is present. More preferably, the barrier layer comprises one or more selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co- 3-hydroxyhexanoate) (PHBH), silk, zein and mixtures thereof. Even more preferably, the barrier layer comprises one or more selected from the group consisting of poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), zein and mixtures thereof, optionally combined with silk.

[0030] In the case, that fibroin protein is used in the barrier layer, for example silk protein, or chitin polysaccharides, for example chitin, or phenolic polymers, for example lignin, it is preferred that another material is present in the barrier layer as well. Fibroin, preferably silk protein, or chitin polysaccharides, for example chitin, or phenolic polymers, for example lignin, may be combined preferably with one or more materials selected from the group consisting of polyhydroxyalkanoates (PHA), or pro-lamines. It may preferably be combined with one or more selected from the group consisting of polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), and zein. It may more preferably be combined with one or more selected from the group consisting of polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3- hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), and zein. It may most preferably be combined with one or more selected from the group consisting of poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), and zein.

[0031] Electrospinning

[0032] The barrier layer (2) typically is an electrospun layer of deposited fibers. Electrospinning is a known deposition technique to deposit fibers on a substrate. It is generally used in pharmaceutical applications, e.g. to manufacture filters. General deposition techniques involve heating of the material to be deposited, e.g. to melt it. It was found, that in the context of the present invention, several non-petroleum based, natural, materials cannot be melted and accordingly are hard to deposit, and could be deposited using electrospinning, in the form of fibers. In this manner, barrier laminates can be produced with enhanced seal strength, in particular enhanced heat-seal strength. In the context of cellulose fiber-based, in particular paper-based, barrier laminates, electrospinning allows for deposition of the materials without negatively affecting the quality of the cellulose-based fiber layer: Whereas traditionally coatings are applied to a substrate using dispersion coating, which may wilt the substrate when absorbing the solvents used in dispersion coating, and which may damage the cellulose fiber-based substrate, during electrospinning, fibers are deposited while any solvent evaporates in the deposition process, leaving the cellulose fiberbased substrate unaffected.

[0033] Electrospinning is a fiber manufacture technique, which produces non-woven fiber mats. This technique utilises electric charge to draw a charged jet of polymer solution, and deposit a dry fibre on a negatively charged collector. Polymers such as polyhydroxyalkanoates (PHA), and proteins such as silk fibroin and zein protein can be electrospun. These polymers are dissolved in a solvent and loaded into a syringe, and when electrospun, the solvent evaporates leaving behind a dry fiber. The process is essentially depicted in Figure 1. The electrospinning parameters can be adjusted, as known in the art, including the distance to the collector, the voltage and the flow rate, which will allow adjustment of the fiber diameter. In the context of the present invention, a diameter of between 250 and 1000 nm, but in particular, preferably 300-700 microns, proved optimal, in particular in the context of a cellulose-fiber based, preferably paper-based substrate layer, since this diameter resulted in optimal barrier properties to accommodate for the inherent pores present in this substrate material.

[0034] Also, the thickness of the barrier layer can be adjusted by increasing the spinning time of the fibres, allowing a higher fibre density to be deposited, and is preferably not too thin, but also not too thick. A preferred deposition thickness of the fiber layer is between 10 and 55 microns, preferably of between 10 and 20 microns. This is not necessarily the thickness as observed in the final packaging laminate of the present invention, since the manufacturing process preferably involves a compression step, and results in the final thickness of the barrier layer as mentioned earlier herein. In the context of the invention, a ‘random’ orientation of the fibres upon deposition is preferred (e.g. vs. an ’aligned’ deposition), for optimal seal effect.

[0035] The process of electrospinning will be further elaborated when describing the manufacturing method of the invention.

[0036] Additional layers

[0037] It is preferred, that the substrate layer is in direct contact with the barrier layer, and the latter is preferably directly deposited on the substrate layer, for optimal sealing strength. Alternatively, it could be preferred that a pre-coat layer is present between the substrate layer (1) and the barrier layer (2), but this is not required. If present, the precoat layer is preferably from a material that is not petroleum-sourced. A preferred precoat layer could be selected from the group consisting of starch, zein, protein, cellulose, clay and mixtures thereof. A clay-based precoat layer is most preferred. A precoat layer may preferably have a thickness of between 1 and 5 gsm, preferable 1 .5 to 4 gsm. The pre-coat can suitably be applied using dispersion or extrusion coating, as known to the skilled person. It may be preferred, that no pre-coat layer is present between the substrate layer and the barrier layer, e.g. for a more optimal result.

[0038] Apart from the substrate layer, and the barrier layer, the barrier laminate of the present invention may further comprise an ink layer (3). The barrier laminate is used to protect a consumer product (6). In this respect, it also provides a communication function to the consumers who will buy the consumer products, typically via information printed on the substrate, e.g. paper, including information regarding ingredients, appealing artwork and advertisement etc. The barrier laminate therefore preferably comprises a layer of ink (3). This layer of ink is preferably connected to the substrate layer (1). It may be preferred that there is a primer applied between paper layer and ink layer. Appropriate primers are known to the person skilled in the art. The layer of ink is preferably in direct connection with the substrate layer (1) and typically faces the outside of the barrier laminate (e.g. when applied in a consumer packaging), i.e. the site opposite to the site of the barrier laminate that will be in contact with the consumer product to be packaged. I.e. typically opposite of the side of the substrate layer where the barrier layer (2) is located.

[0039] For example, to protect the ink layer, the barrier laminate preferably comprises a protection layer (4) on top of the ink layer. The protection layer is typically facing and in contact with the outside world. It is typically located opposite to the product-facing site of the laminate (e.g. when applied in a consumer packaging) and opposite to the side of the laminate where the barrier layer (2) is located. The protection layer (4) may be an over-print varnish (OPV), OPVs are well-known to the person skilled in the art and the chosen varnish depends on the intended use of the barrier laminate of the present invention. For example, the OPV may be selected from the group consisting of conventional offset letterpress varnishes, acrylic varnishes, UV varnishes, and gravure varnishes. OPVs can be water-based polymer formulations or solvent-based polymer formulations. The protection layer (4) typically is deposited directly on the ink layer (3), It is preferably in direct contact with the ink layer. The ink layer and the protection layer (e.g. OPV) do not count as ‘barrier layer’ in the meaning used in this description.

[0040] The thickness of the protection layer (4) is preferably between 0.5 and 3 microns, preferably of between 1 and 2 microns.

[0041] It is preferred, that at the ‘product side’, i.e. the side where the barrier layer is located, a total of two layers is present, including the substrate layer (1). Accordingly, preferably no further layer is present between the barrier layer and the substrate layer. Preferably no layer, such as a sealing layer, is present on top of the barrier layer (2). It may be preferred that only one barrier layer, i.e. the barrier layer comprising, preferably consisting of the electrospun fibers, is present in the barrier laminate of the invention. The barrier layer (2) therefore can be sealed, preferably heat- sealed. Preferably no second or further barrier layer is present on the side of the substrate layer that faces the environment (5), i.e. the side opposite to that where the barrier layer (2) is present. Preferably, no metal layer or metal oxide layer is present in the barrier laminate. It may be preferred that no plasma treatment is present of any of the materials used in the barrier laminate.

[0042] Packaging product and packaged consumer product

[0043] In a second aspect, the invention relates to a flexible packaging product for packaging a consumer product, the packaging product comprising the flexible barrier laminate of the invention. The packaging product comprises flexible barrier laminate of the invention that has been sealed, wherein the pieces of barrier laminate have been sealed together, or wherein a piece of barrier laminate has been folded and sealed together, wherein respective barrier layers (2) are facing each other. Preferably, the barrier layer (2) effectively functions as a sealing layer. It is preferred, that no further sealing layer is present or applied, preferably no additional (i.e. besides the barrier layer layer (2)) electrospun sealing layer is present. Preferably the electrospun barrier layer is the peripheral layer of the barrier laminate. Typically the borders of the resulting packaging product, such as a sachet or wrapper are sealed together, as the skilled person understands. Sealing is preferably carried out by heat sealing.

[0044] The packaging product may be in the form of a flow-wrap, pillow bag, gusseted bag, stand-up pouch, diaper bag, tetrahedral bag, quattro seal bag or sachet. The packaging product may contain a consumer product. Typical consumer products that can be packaged using packaging products with flexible barrier laminate of the invention are preferably selected from the group consisting of frozen confectionary, bouillon, soup, sauces, coffee, tea, supplements, vitamins, electrolyte powders, laundry detergents, skin cleansing products, skin care products and haircare products. In particular, it is preferred that the packaging product is a sachet or a wrapper. A wrapper can be used for example to wrap a soap bar, a frozen confectionary product or a condiment like a bouillon or seasoning concentrate. “Frozen confectionary” is a term known to the skilled person, and frozen confectionery items include ice cream, gelato, frozen yoghurt, sorbet, granita, water ice, and the like.

[0045] The invention further relates to a packaged consumer product, wherein the consumer product is packaged in a packaging product comprising the flexible barrier laminate of the invention.

[0046] The packaging product preferably consists of one or more pieces of barrier laminate, which are formed and sealed to form a packaging, enveloping the consumer product.

[0047] Method of manufacturing

[0048] In a third aspect, the present invention relates to a method to manufacture the barrier laminate of the present invention. The process comprises the steps of: a) Providing a cellulose fiber-based substrate layer (1). b) Depositing fibers using electrospinning, to form a fiber network, c) Laminating the resulting composite comprising substrate layer (1) and deposited fiber network, to result in a barrier laminate according to the invention.

[0049] Preferences and details as described in the context of the first aspect of the invention, apply to the second and other aspects of the invention, mutatis mutandis.

[0050] The barrier laminate can be produced in a conventional electro spinning apparatus, such as for example the EF500 electrospinning system from Ske Research Equipment. In step a) of the process of the invention, a substrate layer is provided. With reference to Figure 1 , a substrate layer as described above in relation to the first aspect of the invention, is typically positioned on the collector, like a collection plate, of the apparatus, which is typically negatively charged. It can be advantageous, that low air pressure (a “vacuum”) is applied under the substrate layer, for optimal result. The material to be spun, like polymer or protein, is dissolved in a solvent. The solvent is then loaded in the apparatus, e.g. in a syringe.

[0051] The materials described in the first aspect of the invention are spun to form a fiber network, which forms a layer (2), typically on top of the substrate layer (1). Solvents to dissolve the materials such polymers to be spun are known in the art. For example, polyhydroxyalkanoates, like PHBV or PHBH, are preferably dissolved in a mixture of 1 ,1 ,1 ,3,3,3-Hexafluoro-2-propanol (HFIP), DMSO and water (8:1 :1), wherein the PHA is suitably dissolved at preferably 50 °C under stirring, e.g. overnight, after which dimethyl sulfoxide and water are added at room temperature (RT) under stirring. Zein dissolves at RT in ethanol / DI water (80% / 20%), under stirring. Fibroin, like silk fibroin, dissolves in formic acid.

[0052] The solution comprising the material to form fibers (polymer, polysaccharide, protein) is transported to a charged jet with typically a Taylor cone. Electric charge draws the charged jet with polymer solution and deposits fiber on the collector. In this manner non-woven fiber mats result and are deposited on the substrate layer. The fibers can be deposited using a needlebased electrospinning system, or (preferably) a needleless electrospinning system.

[0053] As known in the art, the diameter of the fibers can be suitably adjusted by altering the electrospinning parameters including voltage, flow rate, distance to the collector and the speed of collector rotation. The thickness of the resulting fiber mat can be adjusted by increasing the fibre deposition time to collect a thicker mat, the longer the fibres spin, the higher the fibre density is deposited. The fiber network deposited in step b) of the process, has preferably a thickness of between 10 and 60 microns, preferably of between 12 and 35 microns. A mat of PHA, in particular of PHB, PHBV or PHBH, preferably PHBV or PHBH, preferably is deposited to a thickness of between 10 and 30 microns, preferably of between 15 and 25 microns. A mat of fibroin, e.g. silk fibroin, is preferably deposited to a thickness of between 10 and 30 microns, preferably of between 15 and 20 microns. A mat of pro-lamines, preferably zein, is preferably deposited to a thickness of between 10 and 30 microns, preferably of between 10 and 15 microns. A mat of polysaccharides, preferably chitin polysaccharides, including chitosan, is preferably deposited to a thickness of between 10 and 60 micron, preferably of between 12 and 35 microns. A mat of phenolic polymers (e.g lignin), is preferably deposited to a thickness of between 10 and 60 microns, preferably of between 12 and 35 microns.

[0054] In a preferred situation, the electrospinning in step b) involves electro spinning, preferably electro- blow-spinning. Electro-blow spinning is a technique as such known in the art. In the present context, it has the advantage that the throughput is enhanced compared to traditional electrospinning. The fiber coating can be deposited at higher speed and more fibers can be deposited in a shorter period of time.

[0055] It may be preferred, that at least two materials are electrospun at the same time in step b). For example, it may be preferred, to spin a mixture of silk and PHBV, It was found, that a mixture of silk and PHBV proved to be optimal for reducing the laminate water vapour permeability.

[0056] After application of the barrier layer in step b), the deposited fiber web is laminated. Accordingly, the process preferably comprises a step c), of laminating the deposited fiber network. Lamination typically involves applying pressure and a heat treatment. Lamination is preferably carried out in a thermal laminator. The substrate layer (1), preferably paper, with the barrier layer (2) applied, is typically placed in between two thin sheets of flexible Teflon film, where heat and pressure is applied using a heat laminator. Lamination is carried out, and preferably pressure is applied, preferably when the barrier layer has not been cooled down completely, e.g. to RT, more preferably when the barrier layer is still hot, ensuring it is still in the melting phase to ensure tackiness to encourage the sealing layer to adhere. The pressure is suitably applied via a press, such as preferably a hydraulic press, typically pressure is applied in a thermal laminator. Pressure is suitably applied with a force of between 1 and 10 tonnes, preferably of between 3 and 5 tonnes. Pressure application results in the compression of the barrier layer. It is preferred, that pressure is applied to result in a density of the barrier layer from 5 to 50 g / m2, preferably 5 to 30 g / m2, preferably from 5 to 10 g / m2. The resulting thickness of the barrier layer is preferably of from 1 to 35 micrometers, more preferably of from 1 to 30 micrometres, even more preferably of from 1 to 25 micrometres, even more preferably of from 4 to 25 micrometres, even more preferably from 4 to 15 micrometres, and more preferably from 5 to 10 micrometres. Pressure is preferably applied under heating, preferably at a temperature of between 140 and 160 °C. Heat is typically applied by the pressure plates within the hot press. Heat is preferably applied to both the top and bottom of the laminate structure.

[0057] In the case an ink layer (3) is applied as part of the barrier laminate, it is typically applied after step c), preferably to the substrate layer, as described earlier. A protection layer (4) may be applied over the ink layer, after application thereof.

[0058] Accordingly, the present invention further relates to a barrier laminate manufactured by the process of the invention.

[0059] The invention further relates to a method to manufacture a packaging product according to the invention, the method comprising the steps of: a. Providing a cellulose-based substrate layer; b. Depositing a barrier layer onto the cellulose-based substrate layer via electrospinning to form a fiber network; c. Laminating the resulting composite comprising the substrate layer (1) and the deposited fiber network, to form a barrier laminate; d. Forming a packaging product comprising the barrier laminate; e. Sealing the barrier laminate by connecting parts of the barrier laminate wherein the respective barrier layers become sealed together; to form a packaging product.

[0060] It is preferred, that the method further comprises the step of filling the packaging product resulting from step d) or e) with consumer product.

[0061] Sealing in step e) is typically carried out using heat sealing. The sealing conditions used are preferably in a temperature range of 120-200 °C. Typically pressure is applied during the sealing step, preferably at a pressure range of 2 to 4 bar. The sealing time is preferably 0.2 to 1 seconds. Use

[0062] It was found in the present invention that a barrier layer applied using electrospinning resulted in improved seal strength, obviating the need for a further sealing layer in the barrier laminate, while maintaining acceptable barrier properties. In this manner, low-density coating is achieved, which forms an alternative for conventional barrier layers that relay on extra layers, and may comprise three or even four substrate + barrier layer composites.

[0063] In this respect, it may be preferred, that the barrier laminate has a Water Vapour transmission Rate at 23°C 50 %RH, of below 35 g / m2 / day, preferably of below 30 g / m2 / day, even more preferably of below 25 g / m2 / day, even more preferably of below 20 g / m2 / day and most preferably below 10 g / m2 / day. An average seal strength above 0.8 N / 15 mm is preferred, preferably above 1 N / 15 mm.

[0064] In view of the observed enhanced seal strength, the invention further relates to the use of an electrospun barrier layer in a barrier laminate according to the invention, to enhance the adhesion force upon sealing of the barrier laminate. In particular, the invention relates to the use of an electrospun fiber web in a barrier layer in a flexible barrier laminate, to enhance the adhesion force upon sealing of the barrier laminate to form a packaging product, wherein the barrier laminate comprises a cellulose fiber-based substrate layer (1), and wherein the barrier layer (2) is deposited on one side of the substrate layer, and wherein the barrier layer (2) has a thickness of between 1 and 35 micrometres, preferably between 1 and 30 micrometres, and more preferably between 1 and 25 micrometres, wherein the barrier layer (2) is the only barrier layer, preferably the only layer, applied at the side where the barrier layer (2) is applied, and wherein the barrier layer comprises one or more of polyhydroxyalkanoates, fibroin protein, pro-lamine, chitin polysaccharide, phenolic polymer, and mixtures thereof, with the proviso that if fibroin protein is used, it is used in combination with another material from the list.

[0065] The width of the barrier layer preferably is between 1 and 35 micrometres, preferably of between 1 and 30 micrometres even more preferably of from 1 to 25 micrometres, even more preferably of from 4 to 5 micrometres, even more preferably from 4 to 15 micrometres, and more preferably from 5 to 10 micrometres. Using electrospinning of a barrier layer, a barrier laminate could be prepared wherein the need for a further sealing layer is omitted, and thereby rendering the barrier layer (2) and preferably the barrier laminate home-compostable. “Home-compostable” is a term known to the skilled person, and is according to standard EN 13432. The conditions are 25-30°C within 12 months. The pass condition is: disintegration after 26 weeks, biodegradation within 12 months. Preferably, the barrier layer, and more preferably, apart from a possible protection layer (4) such as an OVP layer and an ink layer (3), the barrier laminate, is free from petroleum sourced materials, to further allow compostability.

[0066] The invention is now exemplified by the following, non-limiting examples.

[0067] Examples

[0068] Example 1 :

[0069] Paper-based flexible packaging materials according to the invention were prepared using the following process.

[0070] Paper sheets with a grammages of 65, 78 and 90 gsm were introduced onto a collector with a diameter of 200mm, and a length of 250mm.

[0071] Samples 1-3 (UPM Confidio) and 4-5 (UPM Solide Lucent) are commercially available papers with paper grammage of 65 and 78 gsm and thickness of 67 and 80 microns, respectively.

[0072] Prior to electrospinning, the fibre materials were solubilised using the parameters below:

[0073] Silk fibroin: Silk fibroin protein was solubilized in pure formic acid to obtain films, which were then solubilized at 8% w / v in formic acid under mechanical stirring for 20 minutes at room temperature. Zein: Zein was dissolved at room temperature in 80% v / v Ethanol 20% DI water under mechanical stirring for 1 hour. The end concentration of zein protein in the resulting solution was 29 wt%.

[0074] PHBV: Dissolution of the polymer was carried out in 1 ,1 ,1 ,3,3,3-Hexafluoro-2-propanol (HFIP) at 50°C under magnetic stirring overnight. In the morning, the solution was removed from the heat source and brought back to room temperature. A dimethyl sulfoxide (DMSO) + DI water mixture (1 :1 , v / v) was added under magnetic stirring for 20 minutes, to result in a HFIP: DMSO: H2O mixture of 8:1 :1 and a final concentration of 7.5 wt% PHBV in the solvent. The solution is then ready to electrospin.

[0075] PHBH: PHBH was solubilized 4.5 wt% w / v in 1 ,1 ,1 ,3,3,3-Hexafluoro-2-propanol (HFIP), under stirring with a magnetic stir bar at room temperature for 24 hours until a cloudy white solution appeared.

[0076] Four different electrospun fibre coatings were prepared. The solution chamber was loaded with the dissolved polymer, and a voltage was applied to the spinneret, from which the polymer is deposited. The difference in charge caused the polymer solution to create fibres, which project onto the paper on the collector. The solvent carrier for the polymer evaporates whilst the fibre travels to the collector. When the target fibre mat thickness was achieved, the coated paper is removed from the electrospinning rig. The target mat thickness was set to 20 pm prior to compression with heat.

[0077] Electrospinning parameters-.

[0078] Using electrospinning fibres were obtained with diameters within a consistent range and deposition with ‘random’ (vs. ‘aligned') fibre orientation. Spray droplets and other artefacts were absent. To this effect, the polymer concentration, the distance to the collector, the voltage and the spinneret rotation speed / flow rate of the polymer and the collector rotation speed were set as indicated in Table 1A and 1 B.

[0079] Table 1A: Electrospinning parameters for polymer / protein fibres optimised to produce stable and uniform fibres on a needleless electrospinning system.

[0080] Table 1B: Electrospinning parameters for PHBH fibres optimised on a needle-based electrospinning system

[0081] Fibres spun at the above conditions had the following properties, indicated in Table 2:

[0082] Table 2: Fibre properties of polymers / proteins spun onto paper.

[0083] For all fibre mats, the target deposited mat thickness was 20 micrometer, which was then compressed using heat lamination to achieve coatings with a uniform thickness. The Solide Lucent paper is based on cellulose fibers, the Confidio paper is the Solide Lucent paper with a clay-based pre-coat applied by the supplier. The thickness of the layer of fibres was controlled by the time of deposition and the flow rate of the fibres.

[0084] Table 3. Breakdown of electrospun materials used in each construct. *= in C.E. 5, the PHBV is not electrospun, PHBV has been applied as barrier layer by dispersion coating for a comparison between technologies.

[0085] **= silk fibroin and PHBV were concomitantly applied using by electrospinning in layers on top of one another. Results

[0086] WVTR (water vapour transmission rate) measurements recorded at 23 °C 50 %RH were conducted using a MOCON AQUATRAN 3 WVTR Analyser following ASTM F3288-18 standards using a Coulometric P2O5 Sensor.

[0087] Seal strength measurements were performed at ambient conditions following ASTM F88, using an Instron, after sealing with an RDM Heat Sealer.

[0088] WVTR:

[0089] Table 4 Water vapour (WVTR) of fibre coated paper measured using a MOCON Permeation Testing Analyser

[0090] At 23°C 50 %RH, a WVTR of below 20 g / m2 / day is preferred, preferably below 10 g / m2 / day. All of examples 1-4 show an acceptable WVTR, wherein Example 1 shows a relatively high WVTR compared to Examples 2 and 3, due to a relatively low coating thickness in Example 1. Example 4 shows a relatively high WVTR, despite a relatively high coating thickness, and without willing to be bound by theory, this is assumed to be due to the type of paper which includes a precoating.

[0091] The thin layer of polymer fibres functioning both as a barrier and heat seal layer allows for recyclability of the barrier paper. For example, conventional metalized PP or LDPE should be applied at levels of 20 to 50 gsm to providing similar levels of barrier properties. Seal Strength:

[0092] Table 5. Seal strengths The results indicate that a paper-based barrier laminate with an electrospun barrier layer prepared from non-petroleum-based material and with a dimension of between 2 and 25 microns, showed superior adhesion force when parts of the barrier laminate where joined using heat sealing, compared to the situation wherein dispersion coating was used (C.E.5). The examples show that that the electrospun barrier layer is in itself sufficient to provide the required seal strength to provide a functional packaging product, without the need for an additional sealing layer, and the desired WVTR which is desired for packaging products (sachets, wrappers) to contain consumer products.

[0093] Example 2 Examples of a barrier laminates according to the invention have been depicted below:

[0094] These two proposed barrier laminate structures are the final constructs that would be entered into a flexible sachet line for product manufacture. Here, the constructs would be subject to another heating step to seal the exterior edges of the sachet prior to product filling. The barrier layers (2) function effectively as sealing layer. The sealing conditions used are preferably in a temperature range of 120-200 °C, a pressure range of 2-4 bar, and a time range of 0.5-1 seconds. The Sealing and barrier layer (2) in these constructs would form a seal around the product (6) and contain it.

Claims

Claims1. A flexible barrier laminate comprising: a. A cellulose fiber-based substrate layer (1), comprising paper or cardboard, b. A barrier layer (2) comprising an electrospun fiber web, deposited on one side of the substrate layer, wherein the barrier layer (2) has a thickness of from 4 to 15 micrometers, and preferably from 5 to 10 micrometers, wherein the barrier layer (2) is the only layer applied at the side where the barrier layer (2) is applied, and wherein the barrier layer comprises one or more of polyhydroxyalkanoates and prolamine, optionally in combination with one or more of fibroin protein, chitin polysaccharide, lignin.

2. The barrier laminate according to any one of the preceding claims, wherein the barrier layer (2) comprises one or more materials selected from the group consisting of polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3- hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)), and zein, optionally in combination with silk, chitosan, lignin, or mixtures thereof.

3. The barrier laminate according to any one of the preceding claims, wherein the barrier layer (2) comprises one or more materials selected from the group consisting of poly(3- hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3- hydroxyhexanoate) (PHBH)), zein, optionally in combination with silk.

4. The barrier laminate according to any one of the preceding claims, wherein the barrier layer (2) is adjacent to the cellulose-based substrate layer (1).

5. The barrier laminate according to any one of the preceding claims, wherein no metal layer or metal oxide layer is present in the barrier laminate.

6. The barrier laminate according to any one of the preceding claims, wherein all materials in the barrier laminate are sourced from non-petroleum-sourced materials.

7. The barrier laminate according to any one of the preceding claims, wherein the barrier laminate excluding an optional ink layer (3) and optional protection layer (4) is home- compostable according to standard EN 13432.

8. The barrier laminate according to any one of the preceding claims, wherein electrospinning comprises electro blow spinning.

9. A method to manufacture the barrier laminate according to any one of the preceding claims, the process comprising the steps of: i. Providing a cellulose fiber-based substrate layer (1) comprising paper or cardboard, ii. Depositing fibers using electrospinning to form a fiber network, iii. Laminating the composite comprising the substrate layer and the deposited fiber network.

10. Packaging product to package a consumer product, wherein the packaging comprises the barrier laminate according to any one of claims 1 to 9.

11. Packaging product according to claim 10, wherein the packaging product is a wrapper or a sachet.

12. Packaging product according to claim 10 or 11 , wherein the consumer product is selected from the group consisting of soap bar, detergent powder, personal wash product, food granules, a liquid or semi-liquid food product, and frozen confectionary.

13. Method to manufacture a packaging product according to any one of the claims 10 to 12, the method comprising the steps of: i. Providing a cellulose-based substrate layer comprising paper or cardboard; ii. Depositing fibers via electrospinning to form a fiber network; iii. Laminating the resulting composite comprising the substrate layer and the deposited fiber network, to form a barrier laminate; iv. Forming a packaging product comprising the barrier laminate; v. Sealing the barrier laminate by connecting parts of the barrier laminate wherein the respective barrier layers become sealed together; to form a packaging product.

14. Method according to claim 13, wherein the method further comprises the step of filling the packaging product resulting from step iv. or v. with consumer product.

5. Use of an electrospun fiber web in a barrier layer in a flexible barrier laminate, to enhance the adhesion force upon sealing of the barrier laminate to form a packaging product, wherein the barrier laminate comprises a cellulose fiber-based substrate layer (1) comprising paper or cardboard, and wherein the barrier layer (2) is deposited on one side of the substrate layer, and wherein the barrier layer (2) has a thickness of between 1 and 35 micrometres, preferably between 1 and 30 micrometres, and more preferably between 1 and 25 micrometres, wherein the barrier layer (2) is the only barrier layer, preferably the only layer, applied at the side where the barrier layer (2) is applied, and wherein the barrier layer comprises one or more of polyhydroxyalkanoates and pro-lamine, optionally in combination with fibroin protein, chitin polysaccharide, lignin, or mixtures thereof.

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