EP4096924A1

EP4096924A1 - A packaging sheet for packaging of butterable products

Info

Publication number: EP4096924A1
Application number: EP21701990.0A
Authority: EP
Inventors: Torben FOGTMANN; Peter Johansen; Lars Christian Christensen
Original assignee: Danapak Flexibles AS
Current assignee: Danapak Flexibles AS
Priority date: 2020-01-31
Filing date: 2021-01-25
Publication date: 2022-12-07
Also published as: WO2021151842A1

Abstract

A packaging sheet for packaging of butterable products, such as butter, the packaging sheet comprising: an inner surface and an outer surface, the inner surface being configured for facing the butterable product, a paper base sheet with a first surface and a second surface, the paper base sheet comprising a paper layer and a light barrier layer or light barrier coating on the paper layer, the barrier layer or barrier coating forming the first or the second surface of the paper base sheet and forming a barrier against light for light protection of the butterable products, an inner polymer contact layer comprising a polyolefin and/or a polyester, a surface of the contact layer establishing said inner surface of the packaging sheet, and one or more polymer tie layers positioned between the paper base sheet and the contact layer, a first surface of the one or more tie layers facing the paper base sheet, a second surface of the one or more tie layers facing the contact layer, wherein the one or more tie layers and the contact layer are co-extrusion coated on the second surface of the paper base sheet, and wherein the paper base sheet has a grammage of above 50 g/m², the one or more tie layers have a total grammage of 1 to 10 g/m², and a total grammage of the coextrusion coated one or more tie layers and contact layer is 5-20 g/m².

Description

A packaging sheet for packaging of butterable products

The present invention relates to a packaging sheet or packaging lam inates or packaging foils for packaging of butterable products, such as butter.

Today, butter is typically packaged in packaging sheets comprising, in sequence, an aluminium (Al) barrier layer, a paper sheet, and a fat/oil-resistant layer, typically of polyethylene (PE). A purpose of the barrier layer is to provide a barrier to oxygen/air and light to prevent the butter from becoming rancid or the butter from otherwise deteriorating. Often, a fat/oil-resistant layer is also included on the surface facing the butter, especially if protection of the paper sheet is desired. Usually, there are requirements to foldability and deadfold to ensure that the packaging can be carried out on a packaging machine while ensuring a tight packaging, especially avoiding air pockets in the packaging corners which can lead to the packaged butter becoming rancid. Also, a rela tively low amount of curl of the packaging sheets is often desired to allow for the packaging to be carried out on a packaging machine.

One example of such a prior art packaging sheet consists, in se quence, of an 8 pm Al sheet coextrusion laminated to a 41 g/m² parchment sheet using a 12 g/m² PE-based coextrusion lamination. The parchment pro vides resistance to fat/oil.

Another example consists, in sequence, of a 6 pm Al sheet coextrusion laminated to a 35 g/m² paper sheet using a 10 g/m² PE-based coextrusion lam ination, and a 15 g/m² PE-based coextrusion coating on the other side of the paper sheet. The paper used in this example is not parchment. Therefore, a coextrusion coating provides resistance to fat/oil to prevent the paper from be ing dissolved. This packaging sheet is typically embossed.

A disadvantage of such prior art packaging sheets is that they are not suitable for being re-cycled, especially due to the high amounts of metal and other non-paper materials in the packaging sheets.

Accordingly, it may be seen as an object of the present invention to provide a packaging sheet for packaging of butter and other butterable prod ucts, which is more suitable for being recycled and which sufficiently maintains one or more of the desired properties of butter packaging sheets as mentioned above.

This and/or further objects may be achievable according to a first as pect of the present invention which involves a packaging sheet for packaging of butterable products, such as butter, according to claim 1.

Alternatively, the packaging sheet may be defined as a packaging sheet for packaging of butterable products, such as butter, the packaging sheet comprising: an inner surface and an outer surface, the inner surface being config ured for facing the butterable product, a paper base sheet with a first surface and a second surface, the paper base sheet comprising a paper layer and a light barrier layer or light barrier coating on the paper layer, the barrier layer or barrier coating forming the first or the second surface of the paper base sheet and forming a barrier against light for light protection of the butterable products, an inner polymer contact layer comprising PE, PET, and/or PP, a sur face of the contact layer establishing said inner surface of the packaging sheet, and one or more polymer tie layers positioned between the paper base sheet and the contact layer, a first surface of the one or more tie layers facing the paper base sheet, a second surface of the one or more tie layers facing the contact layer, wherein the one or more tie layers and the contact layer are co-extru- sion coated on the second surface of the paper base sheet, and wherein the paper base sheet has a grammage of above 50 g/m², the one or more tie layers have a total grammage of 1 to 10 g/m², and a total gram mage of the coextrusion coated one or more tie layers and contact layer is 5- 20 g/m². Such packaging sheets may be suitable for recycling, e.g. for manu facture of new paper materials, since the relative amount of paper to other ma terials, especially metal and thermoplastic polymers, may be high or very high compared to prior art packaging sheets for packaging of butter.

Furthermore, experiments have shown that such packaging sheets with a contact layer comprising a polyolefin or a polyester can provide sufficient and satisfactory barrier to water vapour and fat/oil to make them suitable for use for packaging of butterable products, such as butter. Such packaging sheets can also provide a suitable barrier against oxygen/air. A satisfactorily small curl, foldability and deadfold of the packaging sheets can be achieved, allowing for satisfactory runability on a packaging machine and for a satisfac tory packaging of butterable products. The foldability and deadfold properties achieved with such packaging sheets can be achieved to be near or identical to those properties of prior art packaging sheets for packaging of butter. Also, experiments have shown that it is surprisingly possible to emboss the relatively thin coextrusion coated layers without penetrating these layers, such penetra tion potentially negatively influencing the light barrier properties of the packag ing sheet, see also further below in this regard.

The term “grammage” as used in the present disclosure may also be denoted “loading”, is expressed in g/m² (mass per unit area), and is a measure of the areal density of sheets or layers of a laminate or of the laminate itself. The term “total grammage” is intended to mean the accumulated grammage of two or more layers. For example, two layers each having a grammage of 1 g/m² have a total grammage of 2 g/m². The grammage may be a dry weight gram mage.

In the context of the present disclosure, the term “butterable product” may involve solid or high-viscous (at least at refrigerator and/or room tempera ture, e.g. from 1 to 30 or 5 to 25 degrees Celsius) products suitable for being buttered on bread or the like. Such products may include only unmatured milk products, i.e. may exclude e.g. cheeses. Such products may include products comprising at least 10, 30, 40, 50, 60, 70, 80, 90, 95, or 99 % or substantially 100 % fat originating from milk. The milk may be cow’s milk or milk from any other suitable animals, such as farm animals, such as sheep. Such products may comprise from or up to 0 to 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, or 100 % fat or oil originating from plants, such as rape seed oil, colza oil, or olive oil, or margarine. Such products may comprise products comprising or essen tially consisting of a mixture of milk-based fat or butter and plant-based fat or oil. Such products may also involve, potentially small amounts, of salt, such as natrium chloride, and/or additives, such as for improving shelf life or for adding flavouring. Butterable products may include butter and/or margarine.

The paper base sheet or a paper layer of the base sheet may be man ufactured from conventional paper and may mainly comprise cellulose fibres. The paper may comprise other additives such as bonding additives, adhesive additives or colouring agents. The paper may comprise machine glazed (MG) paper, i.e. paper given a high finish on one side only by drying the paper in continuous contact with a highly polished heated cylinder.

The paper base sheet may be metallized paper with a total grammage of 90 g/m², metallized paper with a total grammage of 70 g/m², or metallized paper with a total grammage of 73 g/m². The grammage of the metallization may be 3 g/m², the remaining of the total grammage being the paper layer.

The inner polymer contact layer may comprise at least 70 percent by weight of polyolefin or polyester, such as one or more of these as disclosed herein, or a monomer thereof, preferably at least 80 percent by weight, more preferred at least 95 percent by weight, and most preferred at least 98 percent by weight. The contact layer may further comprise binders such as polymer binders, polyurethane binders, nitrocellulosis binders or polyester binders. The contact layer may further comprise slip additives, such as a wax, and/or sof tening, colouring and stiffening additives. The contact layer may in some em bodiments comprise pores of a gas, usually air. In such embodiments the pores preferably constitute less than 50, preferably 40, more preferred 30, more pre ferred 20, more preferred 10, more preferred 5, most preferred 2, percent by volume of the contact layer.

PE is proven as suitable for use in a contact layer for facing the butter in packaging sheets. With a contact layer comprising polyethylene tereph- thalate (PET), an improved fat/oil and/or oxygen barrier may be achieved, and/or less flavour may be transferred from the contact layer to the butterable product. Similar to PE, polypropylene (PP) and cyclic olefin copolymer (COC) are polyolefins with relevant characteristics similar or identical to the character istics of PE so that similar results and effects as for PE can be expected for PP and COC in terms of the packaging sheets of the present disclosure.

In the context of the present disclosure, water vapour transmission rate (WVTR) is measured according to standard test method ASTM F1249 at 38°C and 90 % atmospheric humidity and rated per 24 hours unless noted otherwise. The packaging sheet may have a water vapour transmission rate of less than 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, or 8 g/m² per 24 hours at 38°C and 90 % atmospheric humidity.

In some embodiments, the packaging sheet has an oxygen transmis sion rate of less than 15,000, 14,000, 13,000, 12,000, or 11 ,000, 10,500, 9,000, 5,000, 4,000, 3,000, 2,000, or 1 ,000 cm³/m² per 24 hours per bar (OTR; 0%RH 23°C; ASTM D3985).

In the packaging sheets according to the present disclosure, the con tact layer and the one or more tie layers have been coextrusion coated onto the paper base sheet. In such a sheet, the coextrusion coated layers will adhere to the base sheet without a separate adhesive/glue layer being provided be tween them. Accordingly, no separate adhesive or glue layer that includes a hardener or a hardening agent/component, will usually be present between the tie layer(s) and the base sheet. An adhesive or glue layer that includes a hard ener or a hardening agent/component may be defined as a layer that comprises or essentially consists of a two-component adhesive or a two-component glue such as a polyurethane (PU) based adhesive/glue, available from, for example, Henkel AG, Coim Spa or Dow Chemical. Alternatively, it can be determined from a packaging sheet that the tie layer(s) and contact layer have been coex trusion coated onto the base sheet since in that case the packaging sheet will have small curl compared to if it were manufactured in any other manner. An extrusion coating primer may be present between the layers, the primer poten tially improving adhesion.

The polyolefin of the contact layer may be or comprise an ethylene or polyethylene polymer or copolymer, especially a polyethylene (PE), such as a high density polyethylene. The ethylene polymer or copolymer, especially a PE, such as a high density polyethylene, of the contact layer may be or comprise one or more selected from a light density polyethylene (LDPE), a high density polyethylene (HDPE), a medium density polyethylene (MDPE), a PE copoly mer, a copolymer of ethylene and one or more further monomers, a PE terpol- ymer, a terpolymer comprising ethylene and further monomers, and metallo cene. The contact layer comprising one or more of the former PE or ethylene materials may further comprise or include a filler or a filled PE. The filler may be an inorganic substance, such as a calcium-based filler, such as chalk or calcium carbonate. The filler may increase density of the contact layer and/or may provide improved deadfold of the packaging sheet.

The polyolefin of the contact layer may be or comprise a propylene or polypropylene polymer or copolymer, especially a polypropylene (PP). The pro pylene polymer or copolymer, especially a PP, of the contact layer may be or comprise one or more selected from a compound or blend of PP and PE, a PP copolymer, a copolymer of propylene and one or more further monomers, a PP terpolymer, a terpolymer comprising propylene and further monomers, and a maleic anhydride modified PP or propylene.

The polyolefin of the contact layer may be or comprise a COC or a COC polymer. The COC (cyclic olefin copolymer) of the contact layer may be or comprise one or more selected from COC 6013M-07, COC 8007F-600, or 9506F500 marketed by Topas®.

The polyester of the contact layer may be a polyester polymer and may comprise or consist of a polyethylene terephthalate (PET). The PET may be or comprise one or more selected from a glycol-modified PET (PETG), a neopen- tylglycol-modified PET, an amorphous PET (APET), a crystalline or non-crys talline PET, and an isophthalic-acid-modified PET. One suitable PET is Skygreen PN100, which is a PETG.

The PET (polyethylene terephthalate) of the contact layer may be or comprise one or more selected from a glycol-modified PET (PETG), a neopen- tylglycol-modified PET, an amorphous PET (APET), a crystalline or non-crys talline PET, and an isophthalic-acid-modified PET. One suitable PET is Skygreen PN100, which is a PETG.

The PE (polyethylene) of the contact layer may be or comprise one or more selected from an LDPE (light density polyethylene), an HDPE (high den sity polyethylene), an MDPE (medium density polyethylene), a PE copolymer, a PE terpolymer, and metallocene.

The PP (polypropylene) of the contact layer may be or comprise one or more selected from a compound of PP and PE, a PP copolymer, and a ma leic anhydride modified PP.

One or more tie layers may consist of only one single tie layer, or two, three or more tie layers. No further layers besides the tie layers may be posi tioned between the tie layers, where several tie layers are employed. One or more of the tie layers may comprise or consist any one or more of the tie layer materials mentioned further below. In some embodiments, a “tie layer” may be any intermediate layer positioned between the paper base sheet and the con tact layer. Such a “tie layer” may be a barrier layer, i.e. a tie layer with the main purpose thereof being to provide a barrier to e.g. oxygen or water vapor. Such a tie layer with barrier properties may be a HDPE or a cyclo olefin copolymer COC layer.

In other embodiments, the one or more tie layers are not barrier layers.

In some embodiments, at “tie layer” is a layer than ties two adjacent layers to each other.

In some embodiments, the single purpose or function of the one or more tie layers is to tie the two adjacent layers to each other.

In some embodiments, the light barrier layer or light barrier coating is a tie layer. In other embodiments, the light barrier layer or light barrier coating is not a tie layer. The grammage of the paper base sheet or a paper layer of the base sheet may be above 50, 51 , 52, 53, 54, 55, 60, 65, or 70 g/m² and/or may be below 120, 110, 100, 95, 90, 85, 80, or 75 g/m². The grammage of the paper base sheet or a paper layer of the base sheet may be 50-120, 50-100, 50-90, 50-80, 55-110, 55-100, 55-95, 55-90, 55-85, 55-75, 60-100, 60-90, 60- 85, 60-80, 65-100, 65-90, 65-80, 70-120, 70-110, 70-100, 70-90, 70-80, or 70- 75 g/m².

The one or more tie layers may have a total grammage of 1 to 9, 1 to 8, 1 to 7, 1 to 5, 2 to 10, 2 to 9, 2 to 8, 2 to 7, 2 to 5, 3 to 9, 3 to 8, 3 to 7, 3 to 5, 3 to 9, 3 to 8, 3 to 7, 3 to 5,41 to 9, 4 to 8, 4 to 7, or 4 to 5 g/m²,

The total grammage of the coextrusion coated one or more tie layers and contact layer may be 5-18, 5-16, 5-15, 5-14, 5-13, 5-12, 5-11 , 5-10, 5-9, 5- 8, 6-18, 6-16, 6-15, 6-14, 6-13, 6-12, 6-11 , 6-10, 6-9, or 6-8 g/m²

The grammage of the contact layer may be 1-17, 1.5-17, 2-17, 3-17,

4-16, 4-15, 4-14, 4-13, 4-12, 4-11 , 4-10, 5 to 17, 5-16, 5-15, 5-14, 5-13, 5-12,

5-11 , 5-10, 6-16, 6-15, 6-14, 6-13, 6-12, 6-11 , 6-10, 7 to 17, 7-16, 7-15, 7-14, 7-13, 7-12, 7-11 , or 7-10 g/m²

The inner and outer surfaces of the packaging sheet may be free sur faces or surfaces not covered by any further layers or coatings of the packaging sheet.

A primer may be an extrusion coating primer and may be provided on the second surface of the paper base sheet and may potentially be applied before coextrusion coating the one or more tie layers and the contact layer on the second surface of the paper base sheet. The primer layer may have a dry weight grammage of less than 2, 1 .5, 1.2, 1 , 0.8, 0.5, 0.3, 0.2, 0.1 , or 0.05 g/m². The primer may be an extrusion coating primer and may comprise or substan tially consist of polyethylene imine, ethylene acrylic acid, and/or a PP based primer. The paper base sheet may not comprise any further layers or materials besides the paper layer and the light barrier layer or light barrier coating, and potentially besides the primer layer.

In some embodiments, no further layers or material are provided on the first surface of the paper base sheet. Alternatively, a print layer and/or a coloured layer and/or a protection lacquer, which may be transparent, may be provided at or on the first surface of the paper base sheet, an outer surface of the coloured layer establishing said outer surface of the packaging sheet.

The light barrier layer or light barrier coating on the paper layer may be or comprise a metallization of a surface of the paper layer, a lacquer, an ink, a colour, or a coloured layer. A metallization may include a metallization primer facing the paper layer, followed by a metal layer, followed by a lacquer layer. The metallization may include a metal, such as Al. A thickness of the metal layer may be very small, such as less than 1 urn, especially in the nm range. A grammage of the metallization may be less than or equal to 5, 4, or 3 and/or higher than or equal to 1 , 2, or 3 g/m² A lacquer light barrier layer may have a grammage of above or equal to 3, 4, 5, 6, 7, 8, 9, or 10 and/or less than or equal to 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 , 10, 9, 8, 7, 6, or 5 g/m².

A light transmission or a maximum LT of the packaging sheet may be equal to or less than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.5, 1.2, 1.1 , 1 , 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, or 0.55 %. Experiments have shown that such lows LTRs may be achieved according to the present invention, see further below.

The light barrier layer or light barrier coating on the paper layer may lower a light transmission or maximum light transmission through the packag ing sheet with equal to or above 50, 60, 70, 80, 90, 95, or 99 % compared to if it were not present. The term “light transmission” may be a light transmission rate or a maximum light transmission rate or the transmission or the maximum transmission or the directional transmittance or the maximum directional trans mittance. The light transmission may be measured for light within the visible spectrum or from 200-800 nm or from 380-740 nm. A maximum light transmis sion may be the light transmission or light transmission rate of light with the wavelength at which the packaging sheet allows the largest amount of light to be transmitted. The light transmission may be measured as an amount of light passing through the packaging sheet comparted to if no sheet were present, potentially if air were present instead of the packaging sheet. The light trans mission may be measured with light emitted in a direction substantially at a right angle to the packaging sheet. The light may be emitted from a lamp, which may form be substantially a point-shaped and/or circular or longitudinally ex tending or rectangular or square light emitting surface.

The light transmission of the packaging sheet may be denoted “LT” or “LTR” and may be less than or equal to 10, 9, 7, 6, 5, 4, 3, 2, 1 , 0.9, 0.8, 0.7, 0.6, or 0,55 %. The LT may be measured by or in a spectrometer, especially in an ultraviolet/visible (UV/VIS) spectrometer, specifically in a Perkin Elmer UV/VIS Spectrometer Lambda 18. Measurement of the light transmission in a spectrometer may occur continuously within a wavelength interval, the meas urement occurring for one wavelength at a time across the interval, potentially resulting in a curve showing LT as a function of wavelength. The maximum LT is at a top point of such a curve, typically occurring at a wavelength around 500 nm.

The one or more tie layers may be extrusion coating tie layers.

One or more or all of the one or more tie layers may comprise at least 50, 60, 70, 80, 90, 95, 98, or substantially 100 % by weight polyolefin. A poly olefin may be defined as the class of polymers produced from a simple olefin (also called an alkene with the general formula CnH2n) as a monomer. One or more or all of the one or more tie layers may comprise or mainly consist of one or more materials selected from a PE copolymer, a PE terpolymer, each poten tially comprising of an ethylene-acrylic ester, an ethylene maleic anhydride, an ethylene vinyl acetate, an ethylene methyl acrylate, an ethylene butyl acrylate, a metallocene, an ethyl acrylate, an ethylene acrylic acid, an ethylene meth- acrylic acid, an ethylene - acrylic ester - maleic anhydride (EMA) terpolymer, an ethylene-butyl acrylate maleic anhydrate ter-polymer, a random terpolymer of ethylene, an acrylic ester, and a maleic anhydride. Examples of suitable tie layer materials include LOTADER® 3410 and 3210, respectively, both random terpolymers of ethylene, acrylic ester and maleic anhydride. The one or more tie layers may comprise a blend of a polymer, such as an ethylene polymer or copolymer, such as PE, and one or more further materials. In a method of man ufacture of the packaging sheet, these materials may have been blended be fore being melted and/or before entering an extrusion worm or screw of a man ufacturing apparatus. The one or more tie layers may comprise or consist of a copolymer of ethylene and one or more further monomers and/or may be or comprise an ethylene polymer, such as one of the types of ethylene polymers as disclosed herein as suitable for use in the contact layer.

The one or more tie layers or said further materials may include extru sion coating tie layer materials, such as e.g. Lotader 3410 and/or Lotader 3210, which may each be provided as a blend with PE.

In an embodiment, the one or more tie layers includes only one single tie layer having a first surface facing the paper base sheet and a second sur face facing the contact layer. In other embodiments, the one or more tie layers include or consist of two, three or more tie layers.

In another embodiment, a light transmission of the packaging sheet is equal to or less than 1 %.

In another embodiment, the paper base sheet has a grammage of 60 to 100 g/m²

In another embodiment, the one or more tie layers is/are extrusion coating tie layer(s) having a total grammage of 2 to 6 g/m².

In another embodiment, the total grammage of the coextrusion coated one or more tie layers and contact layer is 6 to 16 g/m².

In another embodiment, the contact layer mainly comprises an eth ylene polymer or copolymer, especially a polyethylene, such as a high density polyethylene.

In another embodiment, the contact layer mainly comprises a propyl ene polymer or copolymer, especially a polypropylene.

In another embodiment, the contact layer mainly comprises a cyclic olefin copolymer.

In another embodiment, the contact layer mainly comprises a polyeth ylene terephthalate.

In another embodiment, the grammage of the contact layer is 3 to 12 g/m².

In another embodiment, the contact layer mainly comprises PE. The contact layer may comprise at least 50, 60, 70, 80, 90, 95, or 99 % ethylene.

In another embodiment, the contact layer mainly comprises PET. The contact layer may comprise at least 85, 90, 95, or 99 % PET.

In another embodiment, the contact layer mainly comprises PP. The contact layer may comprise at least 85, 90, 95, or 99 % PP.

In another embodiment, the packaging sheet is embossed, the em bossing comprising substantially no perforations extending through the coex trusion coated tie layers and contact layer.

The term “emboss” as used herein comprises both processes of em bossing and processes of debossing, a relevant effect being that a changed surface roughness is achieved. When the surface roughness is changed, a coarseness of the surface is affected.

A roller may be any type of cylinder that rotates about a central axis. A surface roughness of the roller may be of varying size.

The inventors of the present invention have discovered that, despite the low total thickness of the coextruded layers, it is surprisingly possible and advantageous to emboss the packaging material, and to do this without perfo rating the coextruded layers. That the coextruded coated layers are not perfo rated may involve that all the coextruded layers are not perforated, i.e. none or substantially none of the embossing cavities extend all the way through all the coextruded layers to reach the paper base sheet. Furthermore, the inventors have discovered that the embossing may be carried out without destroying or substantially increasing the light transmission of the light barrier layer or light barrier coating and the packaging sheet, in particular metallizations as de scribed elsewhere in the present disclosure. A depth of the embossing, which may be a maximum depth of em bossing cavities, less than or equal to 40, 35, 34, 33, 32, 31, or 30 pm. The embossing depth may similarly be more than or equal to 15, 20, 21 , 22, 23, 24, or 25pm. The embossing depth may, in particular, be from 20 to 35 pm. The embossing depth may thus, surprisingly, be made similar to embossing depths used in the above-mentioned Al-based packaging sheets without substantially increasing the light transmission of the light barrier layer or light barrier coating and the packaging sheet.

Embossing the packaging sheet may improve runability during manu facture of the packaging sheet and/or may improve deadfold properties of the packaging sheet. The deadfold properties may accordingly be sufficient to al low for packaging of butterable products in the packaging sheet.

Embossing depths of embossings of in packaging sheets of the prior art are usually in the range of 24-34 pm.

In another embodiment, the light barrier layer or light barrier coating of the paper base sheet is a metallization on a paper layer, the metallization and the paper layer forming the paper base sheet.

According to another aspect, a package comprising a lump or piece of a butterable product, such as butter, is provided, the product being wrapped in a packaging sheet according to any one of the above embodiments.

Hereby, advantages and effects similar to the ones achieved accord ing to other aspects of the invention may be achieved.

The packaging sheet may be folded about the piece or lump of butter- able product, potentially in a conventional manner. The piece of butterable product may be shaped substantially as a parallelepiped or may be box shaped. A length, width, and/or height of the piece may be 2-20 or 3-15 cm.

In another aspect, the present invention involves a method according to claim 20.

The packaging sheet manufactured according to the methods of this disclosure may be according to any one of the embodiments of packaging sheets discussed above and herein, including any one of claims 1 to 19.

Extrusion coating and coextrusion coating are well-known processes where a carrier foil or base sheet is moved between two rollers, a cooling roller and a counter roller, respectively. Coextrusion is a process of extruding two or more materials through a single die of an extruder so that the extrudates merge and weld together into a laminar structure before chilling or quenching. Coex trusion can be employed in film blowing, free film extrusion, and extrusion coat ing processes, the latter being referred to as coextrusion coating. Extrusion lamination and coextrusion lamination are processes similar to extrusion coat ing and coextrusion coating, respectively, but where two sheets of material are laminated together.

In the present methods, the one or more tie layers and the contact layer, specifically comprising or consisting of a thermoplastic polymeric melt, may be applied between the base sheet and the cooling roller in a continuous process. Upon contact with the cooling roller, the melt may solidify, and upon contact with the base sheet, the thermoplastic melt may be adhered to the base sheet, potentially without the use of an adhesive/glue layer between them. The result will be the base sheet coated with a thin layer of the coextruded thermo plastic material.

The coextrusion coating step may be performed by means of an ex truder.

The two or more coextruded melts may be extruded together from one common die. While still not having been chilled and solidified, the melts are coated onto the base sheet or carrier foil so that the coextruded layers adhere to the base sheet. An extrusion coating primer may be applied to the base sheet before the coextruded melt is applied to it to improve adherence.

When coextrusion coating the one or more tie layers and the contact layer on the paper base sheet, the layers may immediately adhere to each other. Hereby, tooling costs may be lowered since both layers can be applied by the same machine. The manufacturing time may be shortened accordingly since the application of both layers can be done at the same time, instead of having to apply an adhesive/glue layer in a separate step prior to the application of the contact layer.

In the methods according to this disclosure, the tie layer material(s) and the contact layer material may be fed into a feed block of an extruder through a respective separate feeder, which may comprise a worm or other means for transporting the materials through the feeder and into the feed block.

The melts or extrudates within the die may merge and weld together into a laminar structure to form the coextruded layers that are applied onto the base sheet before chilling or quenching. Chilling or quenching may be carried out by applying the coextruded layers or the packaging sheet onto a cooling roller in a subsequently performed coating step of the coextrusion coating pro cess. In the coating step, the two or more coextruded melts may be extruded onto the base sheet so that the coextruded layers adhere to the base sheet. The coextruded layers and the base sheet may be guided through a nip be tween the cooling roller and an opposed pressure roller, and pressure may be applied between the two rollers. The contact layer may face the cooling roller, the base sheet facing the pressure roller. As mentioned, a primer may be ap- plied to the base sheet before the coextruded melt is applied onto it. The po tential primer is preferably applied to the base sheet immediately before the coextruded layers are coated onto the base sheet, i.e. less than 60, 30, 15, 5, 4, 3, 2 or 1 seconds before.

In an embodiment of the method, the method further comprises the step of increasing a surface roughness of the inner surface of the packaging sheet by means of embossing using an embossing roller with a surface rough ness.

The embossing may be Damask embossing which is a type of em bossing well known in the art.

The packaging sheet may be rolled off from a roll and enter into a nip between two rollers, which may be two embossing rollers or one embossing roller and one paper roller. The paper roller may not comprise an embossing surface pattern.

The embossing roller(s) may include a surface pattern of e.g. pyramid shaped embossing projections, which may be distributed on the embossing roller.

In the embossing step, the packaging sheet may be run between two rollers, specifically of metal or steel, both rollers potentially comprising a sur face embossing pattern, potentially in a male/female configuration. The two rollers may be pressed together to form a nip between them.

Alternatively, only one of the rollers is an embossing roller and includes a surface embossing pattern, the other roller potentially being a paper roller. In this case, water may be applied to the paper roller during the embossing step. The paper roller may have a diameter of more than 1.5 to 2.5 times a diameter of the patterned embossing roller. A tolerance of the diameter of the paper roller may be kept narrow to avoid tearing of the packaging sheet, which may occur if the roller speeds of the two rollers are not strictly aligned. Furthermore, the pressure in the nip may be kept relatively low. Hereby, not perforating the co extrusion coated layers of the packaging sheet may be achieved even with thin coextrusion coated layers.

The above and/or additional objects, features, and advantages of the present invention will be further outlined by the following illustrative and non limiting detailed description of embodiments of the present invention, with ref erence to the appended drawings, in which:

Fig. 1 schematically shows a cross section of a packaging sheet ac cording to an embodiment of the packaging sheets of the present disclosure,

Fig. 2 schematically illustrates a method of manufacture of the pack aging sheet of Fig. 1 according to an embodiment of the methods according to the present disclosure, and

Fig. 3 schematically shows a cross section of a packaging sheet ac cording to another embodiment of the packaging sheets of the present disclo sure.

Fig. 1 shows a cross section of a packaging sheet S for packaging of a piece or lump of butter (not shown) to form a package (not shown). The pack aging sheet is to be folded about the piece butter in a conventional manner. The piece of butterable product may be shaped substantially as a parallelepi ped and/or may be box-shaped. A length, width, and/or height of the piece may be 2-20 or 3-15 cm.

The packaging sheet S comprises an inner surface 2 and an outer surface 3, the inner surface 2 being configured for facing the butterable product.

The packaging sheet S further comprises a paper base sheet 4 with a first surface coinciding with the surface 3 and a second surface 5. The paper base sheet 4 comprises a paper layer 4a and a light barrier layer in the form of a metallization 4b on the paper layer 4a. An outer surface of the metallization 4b is coinciding with the surface 3. The metallization forms a barrier against light and oxygen for protection of the butter.

The packaging sheet S further comprises an inner polymer contact layer 6 comprising a polyolefin or a polyester, such as PE, PET, and/or PP, an inner surface of the contact layer establishing the inner surface 2 of the pack aging sheet S.

The packaging sheet S further comprises one polymer extrusion coat ing tie layer 7 positioned between the paper base sheet 4 and the contact layer 6, a first surface of the tie layer 7 facing the paper base sheet 4, a second surface of the tie layer facing the contact layer 6. In other words, the tie layer 7 is positioned between the base sheet 4 and the contact layer 6. In other em bodiments, one or more further tie layers may be provided between the base sheet 4 and the contact layer 6, see also the description of Fig. 3 below.

No further layers are present in the sheet S. The inner surface 2 and the outer surface 3 of the packaging sheet S are free surfaces not covered by any further layers or coatings of the packaging sheet. However, an extrusion coating primer has been applied to the surface 5 of the base sheet 4 before the coextrusion coating of layers 6, 7. In other embodiments, a print layer and/or a coloured layer and/or a protection lacquer, which may be transparent, may be provided at or on the first surface 3 of the base sheet 4, an outer surface of the coloured layer establishing the outer surface 3 of the packaging sheet S.

The paper base sheet 4 has a grammage of above 50 g/m², the tie layer has a grammage of 1 to 10 g/m², and a total grammage of the coextrusion coated tie layer 7 and contact layer 6 is 5 to 20 g/m².

The tie layer 7 and the contact layer 6 are co-extrusion coated on the second surface of the paper base sheet 4. Due to this, the coextrusion coated layers 6, 7 adhere to the base sheet 4 without a separate adhesive/glue layer being provided between them.

In a conventional manner, the metallization 4b includes a metallization primer facing the paper layer 4a, followed by a metal layer, followed by a lac quer layer. The metallization 4b includes Al. A grammage of the metallization 4b is less than 1 g/m².

The packaging sheet S is embossed, the embossing comprising sub stantially no perforations extending through the coextrusion coated tie layer 7 and contact layer 6. The embossing depth is from 20 to 35 pm.

The packaging sheet S is manufactured according to a method illus trated in Fig. 2 as described in the following. Thus, the packaging sheet S is manufactured in a conventional coextrusion coating process as illustrated in Fig. 2.

In the coating process of the coextrusion coating step the paper base sheet 4 is continuously rolled off from a feed roll (not shown) to be moved be tween a cooling roller 8 and a counter roller or pressure roller 9. The cooling roller 8 has a chilled or cooled outer surface onto which a melt 10 of the material eventually forming the coextruded layers 6, 7 is applied from an extruder die D positioned between the base sheet 4 and the cooling roller 8. Before reaching the die D, tie layer material and contact layer material are fed into a feed block of an extruder through an associated separate feeder, which comprises a worm for transporting the materials through the feeder and into the feed block.

The coextrusion coating step shown in Fig. 2 is thus a continuous pro cess, the rollers 8, 9 rotating along the arrows shown in Fig. 2 to continuously pull the base sheet 4 off of the feed roll. Upon contact with the base sheet 4 at or right before a nip 11 between the rollers 8, 9, the melt 10 adheres to the base sheet 4. Subsequently, or at the same time, upon contact with the cooling roller 8, the melt 10 is chilled to solidify. The result is the packaging sheet or packaging laminate S comprising the base sheet 4 coated with the layers 6, 7, which is then rolled up on a not shown collecting roller. The melt 10 comprises the two melts of the materials of the layers 6. 7 that are coextruded, i.e. ex truded together through the single die D of the extruder. Thus, the two coex truded melts are coextrusion coated on the base sheet 4 so that the coextruded layers 6, 7 adhere to the base sheet 4 to form the sheet S shown in Fig. 1 . The melt 10 and the base sheet 4 are guided through the nip 11 between the cooling roller 8 and the opposed pressure roller 9 so that the melt 10 faces and contacts the cooling roller 8, and the base sheet 4 faces and contacts the pressure roller 9.

Flereby, the contact layer 6 and the tie layer 7 are coextrusion coated on the second surface 5 of the base sheet 4 so that an inner surface of the contact layer 6 establishes the inner surface 2 of the packaging sheet S and the tie layer 7 is positioned between the paper base sheet 4 and the contact layer 6, a first surface of the tie layer 7 facing and being adhered to the paper base sheet 4, and a second surface of the tie layer 7 facing and being adhered to the contact layer 6.

Coextrusion of the layers 6, 7 occurs through the single die D of the extruder so that the extrudates merge and weld together into a laminar struc ture in the melt 10. The tie layer 7 and the contact layer 6 are applied as a thermoplastic polymeric melt between the base sheet 4 and the cooling roller 8 in a continuous process. Upon contact with the cooling roller 8, the melt so lidifies, and upon contact with the carrier base sheet, the thermoplastic melt is adhered to the base sheet 4, without the use of an adhesive/glue layer between them. The result is the base sheet 4 coated with a thin layer of the coextruded thermoplastic material of layers 6 and 7.

As mentioned, to improve adherence, an extrusion coating primer is applied to the base sheet 4 before the coextruded melt is applied to it.

When coextrusion coating the tie layer 7 and the contact layer 6 on the base sheet 4, the layers 4, 6, 7 immediately adhere to each other.

The melts or extrudates within the die D merge and weld together into a laminar structure to form the coextruded layers 6, 7 that are applied onto the base sheet 4 before chilling or quenching. The chilling or quenching is carried out by applying the coextruded layers 6, 7 and the packaging sheet S onto the cooling roller 8. A pressure is applied between the two rollers 8, 9. The extru sion coating primer is applied to the base sheet immediately before the coex truded layers are coated onto the base sheet.

After the steps described above, the method of manufacture also in volves the subsequent step of increasing a surface roughness of the inner sur face 2 of the packaging sheet S by means of embossing using an embossing roller (not shown) with a surface roughness. In this step, the packaging sheet S manufactured as explained with reference to Fig. 2 is rolled off from a roll (onto which the sheet S was rolled up following the coextrusion coating pro cess) and enters a nip between the embossing roller and a paper roller (not shown). The two rollers are pressed together to form the nip between them. The paper roller does not comprise an embossing surface pattern.

The embossing roller includes a surface pattern of e.g. pyramid shaped embossing projections, which are distributed on the embossing roller.

Water is applied to the paper roller during the embossing step. The paper roller has a diameter of more than 1.5 to 2.5 times a diameter of the patterned embossing roller. A tolerance of the diameter of the paper roller is kept narrow to avoid tearing of the packaging sheet S, which may occur if the roller speeds of the two rollers are not strictly aligned. The pressure in the nip is kept relatively low. Hereby, not perforating the coextrusion coated layers 6, 7 of the packaging sheet S may be achieved even with thin coextrusion coated layers 6, 7. See also further below.

Fig. 3 shows a cross section of a packaging sheet S for packaging of a piece or lump of butter (not shown) to form a package (not shown). The pack aging sheet S of Fig. 3 is identical to that of Fig. 1 , except for the differences as explained in the following. The same reference signs as in Fig. 1 are used in Fig. 3 for identical or similar elements.

In contrast to the embodiment of Fig. 1 , the paper base sheet 4 does not comprise the light barrier layer in the form of a metallization but it could comprise a similar light barrier layer to lower light transmission through the packaging sheet S.

As in the embodiment of Fig. 1 , the inner polymer contact layer 6 shown in Fig. 3 comprises a polyolefin or a polyester.

Compared to Fig. 1 , the packaging sheet S of Fig. 3 comprises a fur ther polymer extrusion coating tie layer 12 positioned between the paper base tie layer 7 and the contact layer 6. The tie layer 12 can alternatively, or addi tionally, be denoted a barrier layer, which may provide an improved barrier against water vapour. The tie layer 12 can be e.g. a HDPE layer or a COC layer. The tie layer 12 is a tie layer in the sense that it ties the contact layer 6 to the tie layer 7. A first surface of the tie layer 7 faces the paper base sheet 4, a second surface of the tie layer 7 facing the tie layer 12. The tie layer 12 is positioned between and in contact with the tie layer 7 and the contact layer 6. Individual grammages and a total grammage of the two tie layers 7, 12 can be varied.

No further layers are present in the sheet S of Fig. 3. No extrusion coating primer has been applied to the surface 5 of the base sheet 4 before the coextrusion coating of layers 6, 7. In other embodiments, a print layer and/or a coloured layer and/or a protection lacquer, which may be transparent, may be provided at or on the first surface 3 of the base sheet 4, an outer surface of the coloured layer establishing the outer surface 3 of the packaging sheet S.

The tie layer 12, the layer 7, and the contact layer 6 are co-extrusion coated on the second surface of the paper base sheet 4. Due to this, the coex trusion coated layers 6, 7, 12 adhere to the base sheet 4 without a separate adhesive/glue layer being provided between them.

The packaging sheet S of Fig. 3 is not embossed.

The packaging sheet S is manufactured in a manner identical to the embodiment of Fig. 1 ; however, the further tie layer 12 is included in the coex trusion coating.

Flereby, the contact layer 6 and the tie layers 7, 12 are coextrusion coated on the second surface 5 of the base sheet 4 so that, as in Fig. 1 , an inner surface of the contact layer 6 establishes the inner surface 2 of the pack aging sheet S and the tie layers 7, 12 are positioned between the paper base sheet 4 and the contact layer 6.

Coextrusion of the layers 6, 7, 12 occurs through the single die D of the extruder. The result is the base sheet 4 coated with a thin layer of the co extruded thermoplastic material of layers 6, 7, and 12.

To improve adherence, an extrusion coating primer may in alternative embodiments be applied to the base sheet 4 before the coextruded melt is ap plied to it.

Experiments

The following embodiments, Samples No. 1-12, of the packaging sheet S of Fig. 1 were manufactured using a method as described with refer ence to Fig. 2:

In the above experiments, the PET used in the contact layer was Skygreen PN100. The PE used in the contact layer was INEOS 23L430B, an additive-free LDPE (0.923 g/m³). “MPAP73” is a 70 g/m² paper layer with a 3 g/m² metallization (total grammage 73 g/m²). The paper layer was DREWSEN SPECIALPAPIERE PROBARRIER Nature Greaseproof Paper, wet strength, machine finish, natural white, high resistance.

The tie layer and the contact layer were coextrusion coated on the base sheet as described in the above with reference to Fig. 2. Samples 1a to 4b were then embossed essentially as described in the above. Samples 1 to 4 were not embossed.

For Samples 1b to 4b (corresponding to Samples 1 to 4, but damask embossed), all Samples 1b to 4b were embossed as described above without perforating the coextrusion coated layers.

For Samples 1a to 4a (corresponding to Samples 1 to 4, but line em bossed), Sample 4a was embossed without perforating the coextrusion coated layers; in Samples 1a to 3a the coextrusion coated layers experienced perfo ration. Samples 1a to 4a were run at embossing settings standard for coextru sion coatings of higher grammage. By optimizing the line embossing parame ters, it is expected that also Samples 1a to 3a can be line embossed without perforating the coextrusion coated layers. Measurements of the light transmission (LT) according to the method as described above of all Samples are shown in the table below in percentages.

The maximum LT was for all samples measured at a wavelength of approximately 500 nm. Less light was transmitted at all other measured wave lengths.

A similar measurement was made on an untreated MPAP73 sheet. The LT of this sheet was measured to 0.55 %. Accordingly, after coextrusion coating the MPAP73 sheet as in all Samples, and embossing the relevant Sam ples, the LT was generally slightly reduced, but still within acceptable parame ters for use for packaging of butter.

A similar measurement was made on a Comparison Sample consist ing, in sequence, of an 8 pm Al sheet coextrusion laminated to PAP41 (a 41 g/m2 parchment sheet) using a 12 g/m2 PE-based coextrusion lamination. The LT of the Comparison Sample was measured to 0.01 %. The Comparison Sam ple corresponds to the first example of a prior art packaging sheet as mentioned in the introduction to this description.

All Samples had an LT of less than 1 %, which was considered ac ceptable for the intended use.

For the Samples, the following values were also measured and appear from the below table (for some measurements, the measurement was repeated for check of measured value):

- Stiffness L was measured as the stiffness in the machine direction in mN according to SCAN- P 29: 95.

- Stiffness T was measured as the stiffness in the cross direction in mN according to SCAN-P 29:95.

- Curl (chord length C) was measured in mm according to ISO 11556:2005(E), second edition 2005.

- Total grammage of the entire packaging sheet and of the coextru sion coated layers was measured in g/m².

- WVTR was measured in g/m² according to ASTM F1249 at 38°C and 90 % atmospheric humidity per 24 hours.

The stiffness and curl values measured were for all Samples compa rable to the Comparison Sample and were considered acceptable for the in tended purpose. Satisfactory runability on a packaging machine can similarly be expected.

Pieces of butter were packaged in each Sample with the contact layer in contact with the butter. By visual inspection, it was determined that in all Samples, there was some absorption of butter (or butter fat/oil) into the paper. However, upon opening of the butter packages, there was no visible delamina tion of coextrusion coated layers from each other nor from the base sheet. Dur ing packaging and unpackaging of the piece of butter, it was also observed that the foldability and deadfold were near identical to the Comparison Sample and sufficient for the intended purpose of the packaging sheets. The following embodiments, Samples No. 5 to 13, of the packaging sheet S of Fig. 1 were manufactured using a method as described with refer ence to Fig. 2 at usual extrusion coating parameters. The embodiment of Fig. 1 was revised to not include a metallized paper. Instead, the paper base sheet 4 (“B paper”) was 60 g/m² white MG Kraft paper, BillerudKorsnas™ ConFlex Silk™.

“HDPE1” was Borealis™ Polyethylene CG8410, an HDPE.

“HDPE2” was Borealis™ Polyethylene CG9620, an HDPE.

“PE” was Borealis™ Polyethylene CA9150, an LDPE.

“COC” was Topas™ 8007F-600, a COC.

WVTR was measured for each of the samples 5-13 above and appear from table below.

The following embodiments, Samples No. 14 to 22, of the packaging sheet S of Fig. 3 were manufactured using a method as described with refer- ence to Fig. 2 at usual extrusion coating parameters.

WVRT was measured for each of the Samples No. 14 to 22 appear from the table below.

Stiffness values of Samples No. 5 to 22 can generally be expected to be at the same levels as or higher than in Samples no. 1 to 4b depending on the applied polymer materials and paper as well as the grammages thereof. Stiffness of coextrusion coated HDPE and COC can generally be expected to be at the same levels as or higher than that of coextrusion coated LDPE if applied in identical grammages. Therefore, curl can be expected to also be satisfactory in Samples 5 to 22. Light transmission rate can be expected to be somewhat higher in

Samples No. 5 to 22 than in Samples No. 1 to 4b since no metallization was applied to the paper of the former. However, this may be alleviated by instead applying a metallized paper, e.g. as in Samples No. 1 to 4b, in Samples 5 to 22. If paper of larger grammage were instead applied in the Samples No.

1 to 22, identical or near identical WVTR values can be expected to be achieved.

Claims

C L A I M S

1 . A packaging sheet for packaging of butterable products, such as butter, the packaging sheet comprising: an inner surface and an outer surface, the inner surface being config ured for facing the butterable product, a paper base sheet with a first surface and a second surface, the paper base sheet comprising a paper layer and a light barrier layer or light barrier coating on the paper layer, the barrier layer or barrier coating forming the first or the second surface of the paper base sheet and forming a barrier against light for light protection of the butterable products, an inner polymer contact layer comprising a polyolefin and/or a poly ester, a surface of the contact layer establishing said inner surface of the pack aging sheet, and one or more polymer tie layers positioned between the paper base sheet and the contact layer, a first surface of the one or more tie layers facing the paper base sheet, a second surface of the one or more tie layers facing the contact layer, wherein the one or more tie layers and the contact layer are co-extru- sion coated on the second surface of the paper base sheet, and wherein the paper base sheet has a grammage of above 50 g/m², the one or more tie layers have a total grammage of 1 to 10 g/m², and a total gram mage of the coextrusion coated one or more tie layers and contact layer is 5- 20 g/m².

2. A packaging sheet according to claim 1 , wherein the one or more tie layers include only one single tie layer having a first surface facing the paper base sheet and a second surface facing the contact layer.

3. A packaging sheet according to claim 1 or 2, wherein a light trans mission of the packaging sheet is equal to or less than 1 %.

4. A packaging sheet according to any one of the previous claims, wherein the paper base sheet has a grammage of 50 to 100 g/m².

5. A packaging sheet according to claim 4, wherein the paper base sheet has a grammage of 60 to 100 g/m².

6. A packaging sheet according to any one of the previous claims, wherein each of the one or more tie layers is an extrusion coating tie layer having a total grammage of 2 to 6 g/m².

7. A packaging sheet according to any one of the previous claims, wherein the or a total grammage of the coextrusion coated one or more tie layers and contact layer is 6 to 16 g/m².

8. A packaging sheet according to any one of the previous claims, wherein the grammage of the contact layer is 3 to 12 g/m².

9. A packaging sheet according to any one of the previous claims, wherein the contact layer mainly comprises an ethylene or polyethylene poly mer or copolymer, especially a polyethylene, such as a high density polyeth ylene.

10. A packaging sheet according to any one of claims 1 to 8, wherein the contact layer mainly comprises a propylene or polypropylene polymer or copolymer, especially a polypropylene.

11 . A packaging sheet according to any one of claims 1 to 8, wherein the contact layer mainly comprises a cyclic olefin copolymer.

12. A packaging sheet according to any one of claims 1 to 8, wherein the contact layer mainly comprises a polyethylene terephthalate.

13. A packaging sheet according to any one of the previous claims, wherein the packaging sheet is embossed, the embossing comprising substan tially no perforations extending through the coextrusion coated tie layers and contact layer.

14. A packaging sheet according to any one of the previous claims, wherein the light barrier layer or light barrier coating of the paper base sheet is a metallization on a paper layer, the metallization and the paper layer forming the paper base sheet.

15. A packaging sheet according to any one of the previous claims, wherein the paper base sheet does not comprise any further layers or materials besides the paper layer and the light barrier layer or light barrier coating, and potentially besides a primer layer.

16. A packaging sheet according to any one of the previous claims, wherein no further layers or material are provided on the first surface of the paper base sheet, or wherein a colored layer is provided at or on the first sur face of the paper base sheet, an outer surface of the colored layer establishing said outer surface of the packaging sheet.

17. A package comprising a lump or piece of a butterable product, such as butter, wrapped in a packaging sheet according to any one of claims 1 to 16.

18. A method for manufacturing a packaging sheet for packaging of butterable products, such as butter, the packaging sheet comprising an inner surface and an outer surface, the inner surface being configured for facing the butterable product, the method comprising the steps of: providing a paper base sheet with a first surface and a second surface, the paper base sheet comprising a paper layer and a light barrier layer or light barrier coating on the paper layer, the barrier layer or barrier coating forming the first or second surface of the paper base sheet and form ing a barrier against light for light protection of the butterable products, and coextrusion coating an inner polymer contact layer and one or more polymer tie layers on the second surface of the paper base sheet so that a surface of the contact layer establishes the inner surface of the packaging sheet and the one or more tie layers is positioned between the paper base sheet and the contact layer, a first surface of the one or more tie layers facing the paper base sheet, a second surface of the one or more tie layers facing the contact layer, wherein the contact layer comprises a polyolefin and/or a polyester, and wherein the paper base sheet has a grammage of above 50 g/m², the one or more tie layers have a total grammage of 1 to 10 g/m², and a total gram mage of the coextrusion coated one or more tie layers and contact layer is 5- 20 g/m².

19. A method according to claim 18, further comprising the step of in creasing a surface roughness of the inner surface of the packaging sheet by means of embossing using an embossing roller with a surface roughness.

20. A method according to claim 18 or 19, wherein the packaging sheet is according to any one of claims 1 to 16.