Heat-seal packaging material

Abstract

The present invention relates to a method of manufacturing a heat-seal packaging material (1) comprising: providing a support layer (2b) comprising paper (2a), applying a first barrier coating composition (7) in the form of an aqueous dispersion, thereby forming a first barrier coating (4) comprising at least 45% by weight of a binder based on the total dry weight of the first barrier coating (4), and applying a second barrier coating composition (7) in the form of an aqueous dispersion, thereby forming a second barrier coating (4) comprising at least 45% by weight of a binder based on the total dry weight of the first barrier coating (4). Applying a second barrier coating composition (8) to form a second barrier coating layer (5) wherein the second barrier coating composition (8) comprises a dispersed heat-sealing polymer which comprises at least 45% by weight of the total dry weight of the second barrier coating layer (5). The invention also relates to a heat-sealing packaging material, to a package comprising the heat-sealing packaging material, and to the use of the heat-sealing packaging material (1) in a package.

Description

TECHNICAL FIELD

[0001] The present specification relates to a method of manufacturing a heat-sealable packaging material. The present specification also relates to a heat-sealable packaging material. BACKGROUND

[0002] A wide variety of packaging materials are produced industrially. For packaging materials, the properties of the product to be packaged and the desired shelf life often determine the packaging material used for packaging each product. In addition, food packaging materials must have some properties that other uses can not require.

[0003] The material used to obtain the desired barrier properties can be chosen, for example, if good water vapour barrier properties are required, the packaging material can comprise a layer of material having excellent water vapour barrier properties, such as aluminium foil.

[0004] However, in the industry, there is still a need for new packaging materials. SUMMARY

[0005] It is an object of the present specification to provide a heat-sealable packaging material. In addition, it is an object of the present specification to propose a method for manufacturing a heat-sealable packaging material.

[0006] The features of the various aspects of the present invention are set forth in the claims. Preferred embodiments are disclosed in the dependent claims. These and other embodiments are disclosed and are disclosed in the specification and drawings.

[0007] The present specification provides a solution to obtain a heat-sealable packaging material comprising a bio-based and biodegradable adhesive. The packaging material according to the present specification comprises a support layer comprising natural fibres comprising cellulose. The support layer comprising natural fibres comprising cellulose can comprise paper. The paper can be a non-viscose paper, i.e. a paper free of viscose fibres.

[0008] The heat-sealable packaging material can comprise three coating layers on the first side of the paper, i.e. two barrier coating layers and a first pre-coating layer. The heat-sealable packaging material can further comprise one coating layer on the second side of the paper, i.e. a second pre-coating layer.

[0009] The first pre-coating layer is preferably the layer on the first side of the paper (between the uncoated paper and the barrier coating layers).

[0010] The second pre-coating layer is optional, but is preferably the layer on the second side of the paper, for example between the uncoated paper and the print.

[0011] The (optional) pre-coating layers can be directly coated on the paper, preparing the support layer surface for the first barrier coating layer and / or the print. At least one of the pre-coating layers can comprise or consist of an adhesive.

[0012] The support layer can thus be a pre-coated paper. Preferably, the first barrier coating is located on the first pre-coat.

[0013] The paper can be calendered, such as super-calendered paper. For example, the uncoated paper can be treated by calendering or the like to enable it to maintain a coated state. A further technical effect is to economically and efficiently improve the barrier properties of the heat-sealable packaging material.

[0014] The second barrier coating can be located on the first barrier coating, most preferably directly on the first barrier coating. A technical effect is to improve the barrier properties of the heat-sealable packaging material. A further technical effect is that the second barrier coating and the first barrier coating create a synergistic effect, further improving the barrier properties of the heat-sealable packaging material. A further technical effect is to provide the heat-sealable packaging material with good heat-seal properties.

[0015] According to the present specification, a method of manufacturing a heat-sealable packaging material can comprise the following steps:

[0016] - providing a support layer comprising a paper comprising natural fibers comprising cellulose, the support layer further comprising a first pre-coat on a first side of the paper, wherein the first pre-coat has a grammage in the range of 1 g / m 2 to 10 g / m 2 , and

[0017] - applying a first barrier coating composition in the form of an aqueous dispersion onto the first pre-coat, the aqueous dispersion preferably having a solids content of 30-45 wt%,

[0018] thereby forming a first barrier coating having a coating weight of 2 to 10 gsm and comprising at least 45 wt% of a binder based on the total dry weight of the first barrier coating, wherein

[0019] - the first binder of the first barrier coating composition is selected from the group consisting of starch, hemicellulose and mixtures thereof, and

[0020] - the second binder of the first barrier coating composition is selected from the group consisting of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, alginate, chitosan and mixtures thereof,

[0021] - applying a second barrier coating composition in the form of an aqueous dispersion onto the first barrier coating, thereby forming a second barrier coating having a coating weight of 4 to 12 gsm,

[0022] the second barrier coating composition comprising a dispersed heat-seal polymer in an amount of at least 45 wt% based on the total dry weight of the second barrier coating,

[0023] wherein the dispersed heat-seal polymer is selected from the group consisting of

[0024] - acrylates,

[0025] - ethylene-acrylic acid copolymers,

[0026] - styrene-acrylate copolymers,

[0027] - styrene-butadiene copolymers,

[0028] - polyolefins,

[0029] - polyesters, and

[0030] - mixtures thereof.

[0031] According to the present description, the heat-sealable packaging material can comprise:

[0032] - a support layer comprising paper comprising natural fibers comprising cellulose, the support layer further comprising a first pre-coat layer located on a first face of the paper, wherein the first pre-coat layer has a grammage in the range of 1 g / m 2 to 10 g / m 2 ,

[0033] - a first barrier coating having a coating weight of 2 to 10 gsm and comprising at least 45 wt% of a binder based on the total dry weight of the first barrier coating,

[0034] wherein

[0035] - the first binder of the first barrier coating composition is selected from the group consisting of starch, hemicellulose and mixtures thereof, and

[0036] - the second binder of the first barrier coating composition is selected from the group consisting of polyvinyl alcohol, ethylene-vinyl alcohol copolymers, alginate, chitosan and mixtures thereof, and

[0037] - a second barrier coating having a coating weight of 4 to 12 gsm and comprising at least 45 wt% of a heat-seal polymer based on the total dry weight of the second barrier coating,

[0038] wherein the heat-seal polymer is selected from the group consisting of

[0039] - acrylates,

[0040] - ethylene-acrylic acid copolymers,

[0041] - styrene-acrylate copolymers,

[0042] - styrene-butadiene copolymers,

[0043] - polyolefins,

[0044] - polyesters, and

[0045] - mixtures thereof,

[0046] wherein

[0047] - the first pre-coat layer is located between the paper and the first barrier coating, and

[0048] - the first barrier coating is located between the first pre-coat layer and the second barrier coating.

[0049] As mentioned before, the heat seal packaging material comprises a first pre-coat layer, which pre-coat layer is located between the paper and the first barrier coating. The first pre-coat layer has a grammage in the range of 1 gsm to 10 gsm.

[0050] Preferably, in order to obtain all the required properties, hemicellulose, polyvinyl alcohol, ethylene-vinyl alcohol copolymer and starch constitute at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt%, most preferably at least 95 wt% (by dry weight) of the first barrier coating binder. Thus, the total amount of hemicellulose, polyvinyl alcohol, ethylene-vinyl alcohol copolymer and starch is preferably at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt%, most preferably at least 95 wt% (by dry weight) determined on the total dry weight of the binder in the first barrier coating.

[0051] The paper can be a gloss paper or a super gloss paper. The technical effect is to provide an improved surface, for example for the barrier coating.

[0052] The first binder of the first barrier coating can comprise starch, wherein the degree of polymerization of the starch is preferably in the range of 100 to 3000. The technical effect comprises obtaining the required barrier properties, for example the required grease barrier properties, together with the second binder.

[0053] Alternatively, or in addition, the first binder of the first barrier coating can comprise hemicellulose, wherein the degree of polymerization of the hemicellulose is preferably in the range of 50 to 300. The technical effect comprises obtaining the required barrier properties, for example the required grease barrier properties, together with the second binder. Another technical effect is the use of a bio-based raw material that has no nutritional value for food or feed.

[0054] The second binder of the first barrier coating is preferably selected from the group consisting of polyvinyl alcohol and ethylene-vinyl alcohol copolymer. The technical effect of the second binder comprises increasing the elasticity of the coating.

[0055] The ratio of the first binder of the first barrier coating to the second binder of the first barrier coating is preferably in the range of 9:1 to 1:1, more preferably in the range of 4:1 to 2:1. The technical effect comprises providing improved barrier properties as well as the required film forming, emulsifying and adhesive properties.

[0056] In an advantageous embodiment, the heat seal polymer is selected from the group consisting of

[0057] - styrene-acrylate copolymers,

[0058] - styrene-butadiene copolymers, and

[0059] - polyolefins,

[0060] More preferably, the heat seal polymer is selected from styrene-acrylate copolymers and styrene-butadiene copolymers.

[0061] Preferably, all coatings of the heat seal packaging material are nano-cellulose and aluminium free coatings. Technical effect is to provide an economically efficient and environmentally friendly heat seal barrier material.

[0062] Preferably, the paper is a viscose free paper. Technical effect is to provide an economically efficient and environmentally friendly heat seal barrier material.

[0063] Preferably, the furnish used for the paper is free from highly refined cellulose. Furthermore, the paper is preferably free from highly refined cellulose, including nano-cellulose. Technical effect is to reduce energy consumption, thereby providing an economically efficient and environmentally friendly heat seal barrier material.

[0064] Preferably, the furnish is free from recycled fibres from used beverage cartons (UBC). Advantageously, the paper is free from recycled fibres from used beverage cartons (UBC). Furthermore, the heat seal packaging material is preferably free from recycled fibres from used beverage cartons (UBC).

[0065] In one embodiment,

[0066] - the mineral pigment content of the first barrier coating is 20 to 65 wt%, and / or

[0067] - the mineral pigment content of the second barrier coating is 10 to 60 wt%.

[0068] Technical effects include reducing the cost of manufacturing the product while achieving the required barrier properties. Furthermore, the mineral pigment content can increase the solid content of the barrier coating.

[0069] Preferably, the oxygen barrier value of the heat seal packaging material is less than 1000 cc / m 2 *day, more preferably less than 700 cc / m 2 *day, most preferably less than 400 cc / m 2 *day.

[0070] Preferably, the mineral oil barrier property (heptane vapour transmission rate) of the heat seal packaging material is less than 20 g / m*day, more preferably less than 15 g / m*day, most preferably less than 10 g / m*day.

[0071] Preferably, the heat-seal packaging material has a WVTR value of less than 100 g / m 2 *day, determined at 23°C / 85%RH according to ISO 2528 standard.

[0072] Preferably, the heat-seal packaging material has a grease barrier performance of more than 60 hours, determined at 40°C using chicken fat according to ASTM F119-82.

[0073] The packaging according to the present specification can comprise a heat-seal packaging material according to the present specification.

[0074] Traditionally, the barrier layer is formed on a fibre-based substrate by using e.g. metallization, extrusion coating or plastic lamination. Nowadays, both producers and end-users are looking for alternative paper and paperboard products suitable for various uses to avoid metallization, extrusion coating or lamination.

[0075] All coating layers of the heat-seal packaging material are preferably free from aluminium. Most preferably, the heat-seal packaging material is free from metal-based foils. The technical effect is to obtain an environmentally friendly, aluminium-free way to achieve the required barrier values.

[0076] The heat-seal packaging material according to the present specification can be manufactured in an environmentally friendly way. Dispersion coating provides a way to obtain thinner coating layers compared to extrusion coating or lamination. Furthermore, dispersion coating can reduce manufacturing and transportation costs. This can reduce the environmental load, such as carbon dioxide load. Thus, preferably, the heat-seal packaging material does not have an extrusion coating.

[0077] Thanks to the new heat-seal packaging material, the predetermined barrier properties can be achieved in a more environmentally friendly way than with traditional methods. The heat-seal packaging material can provide excellent grease, mineral oil and water vapour barrier properties to the packaging made with the heat-seal packaging material. The heat-seal packaging material is able to prevent or at least limit the migration of water vapour, grease and mineral oil through the heat-seal packaging material. Furthermore, the sealed packaging material can be recycled in fibre streams according to PTS METHOD PTS-RH 021 / 97 October 2012, class 2.

[0078] The total amount of natural and biodegradable polymers in the first barrier coating layer can be at least 50% by weight, calculated from the total dry weight of the first barrier coating layer.

[0079] Preferably, the adhesive of the first barrier coating is biodegradable as such, such that the biodegradation rate of the adhesive of the first barrier coating in water is higher than 50% by weight in two months and higher than 90% by weight in three months, determined according to the ISO 14851 standard. Thus, the biodegradation rate of the adhesive in water can exceed 50% by weight in two months and 70% in three months, determined from the adhesive of the first layer of barrier coating according to the ISO 14851 standard. The technical effect is to provide an environmentally friendly heat-seal barrier material.

[0080] Furthermore, the organic material of the first layer of barrier coating can be at least 85% biodegradable, determined according to ISO 14851. The technical effect is to provide an environmentally friendly heat-seal barrier material.

[0081] The biodegradable content of the heat-seal packaging material is at least 30% determined from the total amount of adhesive of the first barrier coating and heat-seal polymer of the second barrier coating. The technical effect is to provide an environmentally friendly heat-seal barrier material.

[0082] The solution according to the present description can be for soft or rigid packaging applications of food, beverages and non-foods requiring barrier values. Preferably, the design of the heat-seal packaging material should ensure recyclability.

[0083] According to the present description, the packaging material is preferably for food packaging. The packaging industry generally requires effective barrier properties, including against water vapour, grease, oil, mineral oil and oxygen, to extend the shelf life of the packaged food.

[0084] Advantageously, the heat-seal packaging material is heat-sealable at least at 150°C, determined at 0.6 bar sealing pressure using a 1.0 second dwell time.

[0085] More preferably, the heat-seal packaging material is heat-sealable at any temperature between 120°C and 160°C, determined at 0.6 bar sealing pressure using a 1.0 second dwell time.

[0086] Most preferably, the heat-seal packaging material is heat-sealable at 150°C, determined at 0.2 bar sealing pressure using a 0.5 second dwell time.

[0087] The technical effect is that the ability of the heat-seal packaging material to be heat-sealed at various temperatures and pressures can enhance the flexibility of the packaging process, thus allowing for example heat-sensitive printing to be used. BRIEF DESCRIPTION OF DRAWINGS

[0088] In the following, the present application will be described in more detail with reference to the accompanying drawings, in which:

[0089] Figure 1 、 2a - c illustrates a cross-sectional example of a heat-seal packaging material,

[0090] Figure 3 Some examples of method steps for manufacturing a heat-sealable packaging material are shown,

[0091] Figures 4-5 Examples of cross-sections of heat-sealable packaging materials are shown, wherein Figure 4 SEM images of the pre-coat and the first barrier coat are shown, Figure 5 SEM images of the pre-coat, the first barrier coat and the second barrier coat are shown,

[0092] Figure 6 Seal strength curves from experimental tests after sealing of heat-sealable packaging material test specimens of 15 mm width at 150°C and 0.2…1.6 bar pressure are shown, wherein good sealing performance is indicated at all tested sealing pressures, and

[0093] Figure 7a - l shows the test results of the VFFS machine packaging test.

[0094] The drawings are intended to illustrate the general principles of the disclosed technology. The drawings are therefore not necessarily to scale or precise in their depiction of system components. DETAILED DESCRIPTION

[0095] In this text, reference is made to the drawings with the following reference signs and symbols:

[0096] 1 heat-sealable packaging material,

[0097] 2a paper,

[0098] 2b support layer,

[0099] 3 pre-coat,

[0100] 3a first pre-coat on a first side of the paper 2a,

[0101] 3b second pre-coat on a second side of the paper 2a,

[0102] 4 first barrier coat,

[0103] 5 second barrier coat,

[0104] 6 pre-coat composition,

[0105] 6a first pre-coat composition,

[0106] 6b second pre-coat composition,

[0107] 7 first barrier coat composition,

[0108] 8 second barrier coat composition,

[0109] 9) calender or pre-coating unit,

[0110] 10) first barrier coating unit, and

[0111] 11) second barrier coating unit.

[0112] Terms and standards

[0113] Unless otherwise stated, the following standards refer to the method used to acquire the values of the quality parameters of the packaging material:

[0114] 1) grammage ISO 536:2019

[0115] 2) density ISO 534:2011

[0116] 3) Cobb 60 ISO 535

[0117] 4) WVTR ISO 2528, 23°C / 50%RH and 23°C / 85%RH

[0118] 5) oxygen barrier ASTM D3985-05, 23°C / 50%RH

[0119] 6) grease barrier ASTM F119-82, 40°C, using chicken fat

[0120] 7) compostability EN 13432

[0121] 8) biodegradability ISO 14851

[0122] 9) Brookfield viscosity SCAN-P 50:84, using RV Brookfield equipment

[0123] 10) Gurley Hill air permeability ISO 5636-5:2003

[0124] 11) roughness ISO 2494

[0125] 12) mineral oil barrier:

[0126] Heptane vapour transmission rate (HVTR) was determined gravimetrically, adapting the method described in Gaudreault et al. 2013 (R. Gaudreault, C. Brochu, R. Sandrosck, P. Deglmann, H. Seyffer and A. Tétreault, Overview of practical and theoretical aspects of mineral oil contaminants in mill process and paperboards, in: Advances in Pulp and Paper Research, Cambridge, 2013, Fifteenth Fundamental Research Symposium, Conference Proceedings, Cambridge, 2013, (S. J. I’Anson, Ed.), pp. 907-925, FRC, Manchester, 2018, DOI: 10.15376 / frc.2013.2.907. A sponge soaked in n-heptane was placed in a test cup, which was then covered with test paper, barrier side down. The rim of the cup was then sealed with melted wax and the filled and sealed cup was stored under standard conditions (50% relative humidity and 23°C). The cup was weighed immediately after sealing and then after 2 h, 3 h, 5 h and 25 h. The HVTR was determined according to the formula in Gaudreault et al. (2013).

[0127] 13) Determination of starch molecular weight distribution:

[0128] An Agilent 1260 Infinity II Multi-Detector GPC instrument equipped with a PLgel Mixed B kit (three analytical columns and one pre-column) was used to measure the starch molecular weight distribution.

[0129] Dimethyl sulfoxide (DMSO) with 50 mM lithium bromide (LiBr) was used as solvent and eluent. The flow rate was 1.0 ml / min and the injection volume was 100 μl. The sample preparation concentration was 5 mg / ml and the samples were filtered using a 0.2 μm PTFE syringe filter (PALL Cooperation, Port Washington, NY, USA) prior to analysis.

[0130] The GPC multi-detector system includes a refractive index detector (RI), a viscosity detector (VS) and a dual-angle light scattering detector (LS) with measurement angles of 15° and 90°. All detectors together (three-detector calibration) are used to measure and calculate the starch molecular weight distribution, calibrated using polymethyl methacrylate (PMMA) (Polymer Laboratories® Standard PMMA, nominal Mp 200,000 g / mol, Agilent Technologies, Santa Clara, CA, USA). The molecular weight distribution is calculated using Agilent GPC / SEC software version A.02.01. The molecular weight based on weight (Mw), number (Mn) and polydispersity index (PDI) are reported.

[0131] 14) Melting temperature Tm and glass transition temperature Tg:

[0132] The melting temperature Tm and the glass transition temperature Tg can be determined by differential scanning calorimetry (DSC) using a differential scanning calorimeter (Mettler-Toledo apparatus). The measurements are carried out under a nitrogen flow of 50 ml / min, with the following program: dynamic heating rate of 10°C / min.

[0133] 1. Dynamic phase from 0°C to 110°C

[0134] 2. Isothermal phase, 110°C, 60 minutes

[0135] 3. Dynamic phase from 110°C to 240°C (first heating)

[0136] 4. Isothermal phase, 240°C, 2 minutes

[0137] 5. Dynamic phase from 240°C to 0°C (first cooling)

[0138] 6. Isothermal phase, 0°C, 2 minutes

[0139] 7. Dynamic phase from 0°C to 240°C (second heating)

[0140] 8. Isothermal phase, 240°C, 2 minutes, and

[0141] 9. Dynamic phase from 240°C to 20°C

[0142] 15) Recycling test for determining recyclability carried out according to PTS method PTS-RH 021 / 97 October 2012, class 2.

[0143] 16) Heat sealing test:

[0144] Unless otherwise specified, heat sealability is tested according to ASTM F2029-16, in the following way: a 15 x 120 mm specimen is cut from the heat-sealable packaging material and a coating-to-coating seal is performed. The seal strength (N / 15 mm) can be measured using a tensile testing machine according to ASTM F88 / F88M-15 standard.

[0145] Furthermore, unless otherwise specified, the sealing parameters are a temperature of 150 °C, a dwell time of 1.0 second, a jaw pressure of 0.6 bar.

[0146] 17) Packaging machine test

[0147] A production test run is performed on pillow bags using a VFFS machine, with a saw-tooth jaw profile for the top and bottom seals and a flat jaw profile for the longitudinal seal. The produced bags are tested for seal integrity by visually evaluating the seal area and the three points (i.e. the intersection of the horizontal and longitudinal seals).

[0148] The term "WVTR" means water vapor transmission rate. Unless otherwise specified, the term "WVTR" means water vapor barrier at a relative humidity of 85%, at a temperature of 23 °C.

[0149] The term "RH" means relative humidity of air.

[0150] In the present specification, unless otherwise specified, percentage values referring to the amount of a material are weight percentages (wt%). Unless otherwise specified, all contents (percentages) are on a dry weight basis.

[0151] The term "gsm" means grams per square meter (g / m2). Unless otherwise specified, all grammages (i.e. coating weights) are on a dry weight basis.

[0152] For the purposes of the present specification and claims, unless otherwise specified, all ranges include any and all intermediate ranges between the stated upper and lower limits and include any and all intermediate ranges therein, which can or can not be specifically elicited herein.

[0153] Unless explicitly stated otherwise, the embodiments and examples recited in the claims and the specification can be freely combined with each other.

[0154] In the present specification, the term "comprising" can be used as an open- ended term, but also includes the closed term "consisting of". Thus, unless otherwise specified, the word "comprising" is to be interpreted as "including or consisting of" as well.

[0155] The term "PVA" refers to polyvinyl alcohol. Polyvinyl alcohol is a synthetic polymer that is prepared by polymerization of vinyl acetate followed by controlled hydrolysis of the ester in the presence of an alkaline catalyst.

[0156] The term "EVOH" refers to ethylene-vinyl alcohol. Ethylene-vinyl alcohol is a copolymer of ethylene and vinyl alcohol. Ethylene-vinyl alcohol can be prepared by polymerization of ethylene and vinyl acetate followed by hydrolysis.

[0157] Hemicellulose is a natural polysaccharide and is a major component of lignocellulosic biomass, a renewable natural polymer. Hemicellulose can be used to replace plastics and applied in specific fields such as films and coatings. Therefore, hemicellulose can be used to manufacture environmentally friendly packaging. Hemicellulose can be classified into xylan, mannan, mixed-linkage beta-glucan, and xyloglucan. In one embodiment, the hemicellulose is water-soluble hemicellulose.

[0158] Starch is a natural polysaccharide, for example, present in wheat, cassava, potato, rice, barley, corn, or pea. In a preferred embodiment, the starch can be dissolved in water.

[0159] In order to achieve the purpose of barrier coating, starch is degraded or converted to obtain solubility and suitable rheological properties. In this specification, the term "starch" specifically refers to starch degraded by chemical, thermal, or enzymatic methods, which can be referred to as dextrin or modified starch or converted starch.

[0160] Degraded starch can be dissolved by industrial methods using a jet cooker or the like at a temperature of 120-145°C for 1-3 minutes. Starch can be cooked at a dry solids content of up to 38-42%. By reducing the evaporation cost, low water usage and energy saving can be achieved at high solids content. The jet cooker utilizes high-speed steam and turbulent mixing to fully mix the fluid and steam.

[0161] Using the starch enzyme conversion method, natural starch can be dissolved at high solids content. Alpha-amylase is added to the natural starch slurry, and the starch slurry is heated to 60-85°C for 5-30 minutes according to the quality of the starch, with steam or heating equipment. For example, further heating to 120-145°C for 1-3 minutes in a jet cooker to complete the dissolution and denature the enzyme.

[0162] Alternatively, the starch can also be cooked in a batch cooking method by adding the modified starch to water under stirring, and then heating the slurry under stirring to 90-100°C until the starch is dissolved, usually for 20-60 minutes.

[0163] Natural starch can also be converted in the laboratory according to the above method.

[0164] Polyvinyl alcohol can be dissolved by adding polyvinyl alcohol powder or granules to water and then heating the slurry to 80-100°C for 20-60 minutes with steam or heating equipment. Fully hydrolyzed PVA typically has a degree of hydrolysis (DS) of 98% to 99.8% and can only be dissolved in water at temperatures above 80°C.

[0165] The term "latex" refers to a dispersion of polymer particles in water. Latex can be natural, for example derived from flowering plants, or synthetic, or a combination thereof.

[0166] The term "polymer dispersion" refers to a polymer dispersed in water by a dispersion technique such as thermal dispersion, mechanical dispersion, or a combination of both.

[0167] The term "dispersible polymer" refers to a polymer that can be dispersed in water by a dispersion technique such as thermal dispersion, mechanical dispersion, or a combination of both.

[0168] In this specification, the term "pigment" refers specifically to mineral pigments. Mineral pigments can include at least one of the following: kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulfate, and titanium dioxide.

[0169] In this specification, the term "platelet-shaped pigment" refers to a pigment having a flat structure, where one dimension of the structure is much smaller than the other two dimensions. Examples of platelet-shaped pigments include kaolin, talc, and mica.

[0170] The term "coating composition" refers to an aqueous composition applied to the surface of an object to form a coating.

[0171] The term "dispersion coating" refers to a coating technique where a coating composition in the form of an aqueous dispersion containing polymer particles is applied to the surface of a substrate, which after drying forms a solid coating.

[0172] The term "coating" refers to a thin solid layer applied to the surface of a substrate.

[0173] The terms "bio-based" and "bio-based material" refer to materials derived from plants and / or other renewable agricultural, marine, and forestry materials, rather than non-renewable materials such as petroleum. In this specification, these terms refer to bio-based materials that have not been chemically modified (except for hydrolysis). Modified starch is an exception, which can be modified to a low degree, meaning a degree of substitution less than 0.1. Degree of substitution (DS) refers to the average number of hydroxyl groups per anhydrous glucose unit (AGU) of starch that are substituted. Oxidized starch is another exception.

[0174] Advantageously, all the coating layers of the heat-seal packaging material are formed using dispersion coating techniques. The technical effect is that thinner coating layers than extrusion coating or lamination can be provided efficiently. Furthermore, dispersion coating can reduce manufacturing costs and transportation costs. This can reduce the environmental load, such as carbon dioxide load.

[0175] support layer

[0176] The support layer 2b comprises a paper 2a having a first side and a second side. Thus, the support layer 2b has a first side and a second side.

[0177] The paper 2a can be a calendered paper. The paper can be a super-calendered paper. The technical effect is to improve the flatness of the paper before applying the barrier coating.

[0178] The support layer comprises a first pre-coating 3, 3a on the paper 2a. The technical effect is to provide a better surface for the paper before applying the barrier coating.

[0179] The paper 2a comprises cellulose-containing natural fibres, typically as its main raw material, and can further comprise, for example, one or more fillers and / or additives.

[0180] The term "cellulose-containing natural fibres" refers to any plant material containing cellulose. The natural fibres can be derived from wood, and / or can include other natural fibres than wood-based natural fibres. Raw materials other than wood-based raw materials can also include agricultural waste, grass and / or other plant material, such as straw, leaves, bark, seeds, beans, flowers, tops or fruits, which can be obtained from cotton, corn, wheat, oat, rye, barley, rice, flax, hemp, abaca, sisal, jute, ramie, kenaf, sugar cane residue, bamboo and / or reed.

[0181] Preferably, the paper 2a comprises cellulose-containing natural fibres derived from wood. The paper 2a can comprise fibres from softwood trees, such as spruce, pine, fir, larch, Douglas fir or hemlock, or from hardwood trees, such as birch, aspen, poplar, alder, eucalyptus or acacia, or from a mixture of softwood and hardwood.

[0182] Preferably, the cellulose-containing natural fibres include chemically pulped natural fibres, i.e. pulp made by a chemical pulping process. Chemically pulped natural fibres are also called chemical pulp. Thus, in an advantageous example, the content of chemically pulped natural fibres is at least 70 wt.%, at least 80 wt.% or at least 90 wt.%, preferably at least 95 wt.%, and more preferably at least 98 wt.% of all cellulose-containing natural fibres used in the paper 2a. Most preferably, all cellulose-containing natural fibres used in the paper 2a are chemically pulped cellulose-containing natural fibres.

[0183] Preferably, the paper 2a does not comprise so-called mechanical pulp.

[0184] Preferably, the paper 2a does not comprise recycled fibers or filaments. Thus, advantageously, the heat-seal packaging material does not comprise recycled fibers and filaments.

[0185] Preferably, the paper 2a does not comprise viscose fibers. Thus, the paper is preferably a viscose-free paper. Thus, the heat-seal packaging material is preferably free of viscose. The technical effect is to improve the cost-effectiveness and environmental friendliness of the product.

[0186] Furthermore, preferably, the paper does not comprise synthetic fibers or filaments. Thus, the heat-seal packaging material is preferably free of synthetic fibers and filaments.

[0187] Furthermore, preferably, the paper does not comprise highly refined fibers. The paper also does not comprise recycled fibers from used beverage cartons (UBC).

[0188] The paper 2a refers to an uncoated structure, i.e. an uncoated paper.

[0189] As mentioned before, the support layer 2b can comprise a pre-coat layer 3, 3a, 3b in addition to the paper 2a.

[0190] Thus, the paper 2a can be coated with a pre-coat composition 6, 6a, 6b.

[0191] The support layer 2b has at least a first pre-coat layer 3, 3a on a first side of the paper 2a and, optionally, a second pre-coat layer 3, 3b on a second side of the paper 2a.

[0192] If the support layer 2b comprises a first pre-coat layer 3a and a second pre-coat layer 3b, the pre-coat compositions of the first and second pre-coat layers are preferably different from each other.

[0193] As mentioned before, the support layer comprises at least one pre-coat layer 3, 3a, 3b. The grammage of each pre-coat layer 3, 3a, 3b ranges from 1 gsm to 10 gsm. Preferably, the grammage of each pre-coat layer 3 is from 2 to 8 gsm, more preferably from 3 to 7 gsm, most preferably from 4 to 6 gsm. The technical effect consists in providing the support layer with a more optimal surface, thus achieving a complete surface coverage with a very low pre-coat layer coating weight. Another technical effect consists in preparing the surface of the support layer for the coating of a barrier pre-coat composition and as an adhesion promoter for the first barrier coating.

[0194] The thickness of the first pre-coat layer 3a and / or the optional second pre-coat layer 3b is preferably from 1 to 10 pm, more preferably from 2 pm to 8 pm, most preferably from 3 to 7 pm. The technical effect is to economically and efficiently prepare the surface of the support layer 2b (e.g. for a barrier coating).

[0195] The pre-coat layers 3a, 3b can comprise or consist of a binder. The binder content in the pre-coat layers is at least 25 wt%, preferably at least 32 wt%, such as in the range of 35% to 60%, most preferably in the range of 35% to 50%, here referring to the relative proportion of the binder in the total content of the pre-coat layer.

[0196] The binder in the pre-coat layers 3, 3a, 3b can comprise at least 65%, preferably at least 75%, more preferably at least 85%, most preferably at least 90% biodegradable material (by dry weight).

[0197] The binder of the pre-coat layers 3, 3a, 3b can be selected from the group consisting of starch, modified starch, enzymatically converted starch, polyvinyl alcohol, ethylene-vinyl alcohol, modified cellulose, dispersions of different polyesters, such as PLA, PBS, PBAT, PHA, PCL, copolymers (diblock copolymers) and terpolymers comprising or consisting of lactide, glycolide and caprolactone, and mixtures thereof.

[0198] Advantageously, the binder of the pre-coat layers 3, 3a, 3b comprises or consists of at least 60 wt% or at least 70 wt%, more advantageously at least 80 wt% or at least 90 wt%, most advantageously at least 95 wt% of the above-mentioned substances. The technical effect is to ensure good surface coverage and film formation of the pre-coat layer.

[0199] In one embodiment, the binder of the first pre-coat layer 3, 3a comprises polyvinyl alcohol and / or modified starch and / or enzymatically converted starch in a total amount of at least 60 wt% or at least 70 wt%, more preferably at least 80 wt% or at least 90 wt%, most preferably at least 95 wt%, up to 100 wt%. The technical effect is to ensure good surface coverage and to improve the film formation of the pre-coat layer.

[0200] The pre-coat layers 3, 3a, 3b can further contain pigments. The pre-coat layers 3, 3a, 3b can comprise mineral pigments, such as at least one of the following: kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate and titanium dioxide. The pigments can include at least one platelet-shaped pigment, such as clay.

[0201] The pre-coat layers 3, 3a, 3b can comprise mineral pigments in an amount of 30 wt% to 75 wt%, preferably 40 wt% to 70 wt%, more preferably 48 wt% to 68 wt%, all based on the total dry weight of the pre-coat layer 3. The use of mineral pigments can improve certain properties of the material, improve the rheological properties during the coating process and reduce the manufacturing costs of the product. However, the mineral content can not be too high.

[0202] Preferably, the adhesive of the second pre-coat layer 3b comprises or consists of modified starch and / or enzyme converted starch, the total amount of modified starch and enzyme converted starch preferably being at least 60 wt.% or at least 70 wt.%, more preferably at least 80 wt.% or at least 90 wt.%, most preferably at least 95 wt.% up to 100 wt.%. The technical effect of the second pre-coat layer 3b is to improve the printability of the heat-sealable packaging material. As mentioned before, the second pre-coat layer 3b can contain pigments. The technical effect of the pigments is to provide a surface more suitable for printing.

[0203] The first side of the paper 2a can be coated with a first pre-coat composition 6a, resulting in a first pre-coat layer 3a.

[0204] Furthermore, the second side of the paper 2a can be coated with a second pre-coat composition 6b, resulting in a second pre-coat layer 3b.

[0205] Thus, the support layer 2b comprises the first pre-coat layer 3a on the first side of the paper 2a. The support layer 2b can also comprise the second pre-coat layer 3b on the second side of the paper 2a.

[0206] Preferably, the support layer 2b comprises only one pre-coat layer 3, 3a, 3b on one or both sides of the paper 2a.

[0207] The grammage of the support layer 2b is advantageously at least 35 gsm, more advantageously at least 40 gsm and preferably not more than 130 gsm. For example, the grammage of the support layer 2b can be in the range of 40 gsm to 120 gsm. In an advantageous example, the grammage of the support layer 2b is between 45 gsm to 110 gsm. The technical effect is to obtain a heat-sealable packaging material with good strength properties. A support layer 2b with a lower grammage is thinner and the strength properties can be reduced, but a significantly lighter material can reduce manufacturing and transportation costs and reduce the environmental burden. Thus, good barrier, heat-seal and strength properties can be provided while the heat-sealable packaging material can be an environmentally friendly technical solution as the amount of raw material needed for the package is minimized.

[0208] The density of the support layer 2b can be 800 to 1200 kg / m 3 . The technical effect is to provide a support layer with good coating retention by high density and / or coating.

[0209] In an embodiment, the density of the support layer 2b is less than 1000 kg / m 3 , more preferably in the range of 800 kg / m 3 to 990 kg / m 3 , more preferably in the range of 820 kg / m 3 to 970 kg / m 3Within the range, the optimal value is equal to or less than 950 kg / m³. 3 For example, at 850 kg / m 3 Up to 950 kg / m 3 Within a certain range. The technological effect is to provide particularly environmentally friendly products, in which energy consumption of the papermaking unit processes (including refining, dewatering and drying steps) is reduced.

[0210] In another embodiment, the density of the support layer is at least 1000 kg / m³. 3 For example, at 1000 kg / m 3 Up to 1200kg / m 3 Within the range, more preferably within 1020 kg / m 3 Up to 1170 kg / m 3 Within the range, the optimal value is 1050 kg / m³. 3 Up to 1150kg / m 3 Within a certain range. The technical effect is that the high-density paper structure enables a good interaction between the surface of the support layer and the coating added to the support layer.

[0211] The roughness (Bendtsen) of the support layer 2b can exceed 40 ml / min, for example, in the range of 60 ml / min to 120 ml / min, as determined according to ISO 2494. The technical advantage is that by providing a support layer 2b with this roughness, the substrate to which the barrier coating is to be applied becomes smooth. The low surface roughness provides a good substrate for the coating process of the first barrier coating composition.

[0212] Because of the presence of the barrier coating, the support layer 2b does not need to have low water vapor permeability. In one embodiment, the WVTR (23°C / 85% RH, ISO 2528) of the support layer 2b is greater than 500 g / m²*day. Technical advantages include improved ease of manufacturing, as the support layer 2b (in itself) does not require the provision of a water vapor barrier material.

[0213] Furthermore, preferably, the mineral oil barrier property (HVTR method, heptane vapor permeability) of the support layer 2b is higher than 100 g / m²*day. Technical advantages include further improvements in the ease of manufacturing, since the support layer 2b (in itself) does not need to provide mineral oil barrier property.

[0214] The grease barrier properties (ASTM F119-82, 40°C, chicken fat) of support layer 2b can be less than 2 hours, or even less than 1 hour. Technical benefits include improved ease of manufacturing, as support layer 2b (at least for its part) does not require a grease barrier material.

[0215] The oxygen barrier property (OTR, 23°C / 50% relative humidity, ISO 15105-2) of the support layer 2b can be higher than 1000 cc / m 2 *day, or even higher than 10,000 cc / m 2 *day. Technical effects include improving the ease of manufacturing process, as the support layer 2b (as such) does not need to provide oxygen barrier property to the material. Another technical effect is to provide an environmentally friendly material, as the support layer 2b can use bio-based materials that do not have high oxygen barrier property.

[0216] The first barrier coating

[0217] The heat-sealable packaging material 1 comprises a first barrier coating 4. The technical effect of the first barrier coating 4 is to lay the foundation for oxygen and grease barrier properties.

[0218] The first barrier coating composition 7 comprises two or more binders. Thus, the first barrier coating comprises a first binder and a second binder.

[0219] The binder content of the first barrier coating 4 is at least 45 wt%, preferably at least 50 wt%, for example in the range of 55% to 80%, most preferably in the range of 58% to 75%, where the binder content refers to the relative proportion of the binder in the total content of the first barrier coating.

[0220] The first binder can comprise or consist of a polysaccharide.

[0221] The polysaccharide may, for example, include hemicellulose, starch, carboxymethylcellulose, and other cellulose ethers or esters.

[0222] Preferably, the first binder of the first barrier coating composition includes hemicellulose and / or starch. The first binder can include at least one of water-soluble hemicellulose and water-soluble starch.

[0223] Preferably, the binder of the first barrier coating composition comprises starch and / or hemicellulose. The total amount of starch and hemicellulose can be up to 90% (by dry weight) of the binder of the first barrier coating composition.

[0224] In one embodiment, the first binder of the first barrier coating comprises one or more hemicelluloses, which can include arabinoxylan or galactoglucomannan isolated directly from wood meal or sawdust, or arabinoxylan or galactoglucomannan isolated after being prepared into holocellulose.

[0225] In one embodiment, the first binder of the first barrier coating comprises hemicellulose, and the weight average molecular weight of these hemicelluloses is preferably 10 000 - 30 000 g / mol, the method of determination referring to Escalante et al., Carbohydrate Polymers 87 (4), 2012. The technical effect is to improve the film forming properties of the coating.

[0226] In one embodiment, the first binder of the first barrier coating can comprise one or more starches. The starches can include modified starches, heat-modified starches and enzyme-modified starches, such as depolymerized starch molecules (e.g. dextrins), enzyme-converted starches (depolymerized starches), maltodextrins and pyrodextrins, and cross-linked starches or thin-boiling starches, oxidized starches, esterified starches, etherified starches or acetylated starches. The technical effect of the said substances is to achieve the desired solubility, tailored rheology and good barrier properties.

[0227] Preferably, the first binder of the first barrier coating comprises or consists of at least one of a modified starch and an enzyme-converted starch.

[0228] In one embodiment, the first binder of the first barrier coating comprises starch, which is based on dextrin. The technical effect is to have a coating composition with a high solids content and excellent resistance to greases. In addition, the starch is easy to dissolve, e.g. by spraying or batch cooking.

[0229] In one embodiment, the starch is based on enzyme-converted native starch. The technical effect is to have a coating composition with a high solids content, a lower price compared to modified starch, to be able to adjust the viscosity and solids content in the preparation of the coating composition, and to provide a good basis for resistance to greases.

[0230] In one embodiment, the starch comprises or is oxidized starch, i.e. starch obtained by treating starch with an oxidizing agent such as hypochlorite or hydrogen peroxide. The technical advantage is the introduction of anionic charge.

[0231] In one embodiment, the enzyme conversion of the starch is carried out with alpha-amylase. The technical effect is to reduce the molecular weight to a level, which enables the dissolved starch to have a suitable viscosity range when the solids content is higher than 30%, e.g. higher than 32% or higher than 33%.

[0232] The starch material can be from any source, including, for example, wheat, cassava, potato, rice, barley, corn or pea.

[0233] If used in the first barrier coating composition 7, the starch preferably has a degree of polymerization of 100 to 3000, more preferably 200 to 1500. The technical effect is that the degree of polymerization is low enough to allow a solid content of 33-42 wt%, while the degree of polymerization is high enough to obtain the desired barrier properties, such as the desired grease barrier properties, together with the second binder.

[0234] If used in the first barrier coating composition 7, the hemicellulose preferably has a degree of polymerization of 50 to 300, more preferably 70 to 200. The technical effect is that the degree of polymerization is low enough to allow a solid content of more than 20% in the hemicellulose solution, while the degree of polymerization is high enough to obtain the desired barrier properties, such as the desired grease barrier properties, together with the second binder.

[0235] In a preferred embodiment, the starch is a low molecular weight starch material having a weight average molecular weight (Mw) of 15000 to 500000 g / mole, more preferably 300000 to 400000 g / mole, more preferably 40000 to 300000 g / mole, most preferably 50000 to 250000 g / mole. The low molecular weight starch material is preferably selected from the group consisting of dextrin and native starch having a specific molecular weight. The layer comprising starch in the first barrier layer - in particular when comprising dextrin and / or enzymatically native starch - shows very good performance in experimental tests. Another technical effect is that the molecular weight is low enough to allow a solid content of up to 33-42 wt% in the starch solution, while maximizing the grease barrier properties of the coating.

[0236] The binder of the first barrier coating 4 can comprise at least 30 wt%, preferably 30 wt% to 95 wt%, more preferably at least 50 wt% and less than 90 wt%, most preferably at least 66 wt% and less than 85 wt% of starch or hemicellulose. Technical effects include improved cost efficiency and operational performance, as well as superior viscosity compared to the use of the second binder alone. Another technical effect of the starch is to provide a higher solid content for the first barrier coating, thereby providing a cost-efficient drying process. Another technical effect is to provide an environmentally friendly coating with increased bio-based content and the introduction of chemicals that are biodegradable in a variety of environments, including soil, fresh water, and sea water.

[0237] In addition to the first binder of the first barrier coating, the binder of the first barrier coating comprises a second binder.

[0238] The second binder is preferably selected from the group consisting of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, alginate, chitosan and mixtures thereof, more preferably the second binder is selected from the group consisting of polyvinyl alcohol, ethylene-vinyl alcohol copolymer and mixtures thereof. A technical effect is to provide a material which is biocompatible, tasteless, non-toxic, has improved film forming properties and is particularly suitable for food packaging. Another technical effect is the inherent biodegradability.

[0239] Thus, preferably, the first barrier coating 4 comprises a first binder selected from the group consisting of hemicellulose and starch and mixtures thereof, and a second binder selected from the group consisting of polyvinyl alcohol, ethylene-vinyl alcohol copolymer and mixtures thereof. A technical effect of this combination is to impart the required biodegradability to the first barrier coating. Another technical effect is to form the required barrier properties against oil and oxygen. Yet another technical effect is to provide a material which is biocompatible, tasteless, non-toxic and has improved film forming properties, for example suitable for food packaging.

[0240] The second binder of the first barrier coating composition 7 can comprise or consist of polyvinyl alcohol and / or ethylene-vinyl alcohol copolymer. The binder can comprise polyvinyl alcohol and / or ethylene-vinyl alcohol copolymer in an amount of 5 to 50 wt.%, preferably 10 to 40 wt.%, more preferably 15 to 35 wt.%, based on the total amount of the binder. Technical effects include improved film forming properties.

[0241] If polyvinyl alcohol is used, it can have a degree of hydrolysis in the range of 97 to 100 mole% and a weight average molecular weight in the range of 30 to 60 kDa. Technical effects include a low tendency to blister and an increased crystallinity compared to lower degrees of hydrolysis.

[0242] If ethylene-vinyl alcohol copolymer is used, it can have a degree of hydrolysis in the range of 97 to 100 mole%, a weight average molecular weight in the range of 30 to 60 kDa and an ethylene content in the range of 1 to 20 mole%, preferably in the range of 10 to 15 mole%. Technical effects are to provide a higher hydrophobicity, a stronger resistance to high humidity and a higher flexibility to heat-seal packaging materials.

[0243] The binder of the first barrier coating can comprise at least 5 wt.% and less than 50 wt.%, more preferably at least 10 wt.% and less than 40 wt.%, most preferably 15 to 35 wt.% of polyvinyl alcohol. Technical effects are to improve the elasticity of the coating while keeping the biobased content of the coating as high as possible.

[0244] Preferably, the first barrier coating 4 comprises:

[0245] - a first binder selected from the group consisting of modified starch, enzyme-converted starch, hemicellulose and mixtures thereof, and

[0246] - a second binder selected from polyvinyl alcohol and ethylene-vinyl alcohol copolymers and mixtures thereof.

[0247] The technical effect, in particular in combination with the molecular weights described in the present specification, is to maximize the solid content of the polyvinyl alcohol or ethylene-vinyl alcohol, relative to what could be achieved as a food contact material on its own; at the same time, the bio-based content in the coating is maximized by the first binder. Furthermore, the presence of the second binder improves the elasticity of the coating compared to a layer consisting of the first binder only.

[0248] Preferably, the hemicellulose, polyvinyl alcohol, ethylene-vinyl alcohol copolymer and starch make up at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt%, most preferably at least 95 wt% (by dry weight) and at most 100 wt% of the binder in the first barrier coating. The technical effect is to provide a good basis for the barrier to oil and fat and to adjust the viscosity of the coating.

[0249] Most advantageously, the polyvinyl alcohol and starch make up at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt%, most preferably at least 95 wt% (by dry weight) of the binder in the first barrier coating. The technical effect is to ensure the use of a high bio-based and inherently biodegradable binder.

[0250] Preferably, the binder of the first barrier coating 4 has inherent biodegradability. By inherent biodegradability is meant that the binder itself biodegrades in water to a degree of more than 50 wt%, preferably > 60%, more preferably > 70% within two months and to a degree of more than 70%, preferably > 80%, more preferably > 85%, most preferably > 90% within three months, as determined according to the ISO 14851 standard.

[0251] The ratio of the first binder to the second binder is preferably 9.5:1 to 0.5:1, more preferably 7:1 to 0.8:1, more preferably 5:1 to 1:1, most preferably 4:1 to 2:1. The technical effects include providing improved barrier properties as well as excellent film-forming, emulsifying and adhesive properties.

[0252] Furthermore, the technical effect of a higher starch content is to provide a higher solid content and a higher bio-based content for the heat-sealable packaging material, while the technical effect of a higher PVA content is to provide a higher elasticity, which is advantageous in mechanical processing.

[0253] Advantageously, the solid content of the first barrier coating composition 7 is 30 to 45 wt%, preferably 32-43 wt%, more preferably 34-41 wt%. The technical effects include speeding up the production efficiency and reducing the energy required to dry the applied coating. This solid content can be obtained particularly easily by using the ratio of the first binder to the second binder as described.

[0254] The first barrier coating can further comprise one or more mineral pigments. The mineral pigments can comprise, for example, at least one of the following: kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate and titanium dioxide.

[0255] The first barrier coating 4 can comprise 20 to 65 wt%, preferably 25 to 60 wt%, more preferably 30 to 55 wt% of mineral pigments, calculated on the total dry weight of the first barrier coating 4. The use of mineral pigments can improve certain properties of the material and reduce the manufacturing cost of the product. However, the mineral content should not be too high in order to obtain the predetermined barrier properties.

[0256] Preferably, the main pigment of the first barrier coating is talc, clay or calcium carbonate, more preferably clay or talc, most preferably kaolin. The technical effect is to better fix the binder on the surface of the support layer 2b, reducing the possibility of the binder entering the micro- and macro-pores of the fibrous network structure. Thus, the binder is able to better interact with the adjacent coating added on the substrate. Another technical effect is to improve the operability of the manufacturing process and to obtain a higher solids content in an economically efficient way.

[0257] The first barrier coating composition and the first barrier coating preferably comprise binder and mineral pigments in a dry weight ratio of 0.8:1 to 6:1, more preferably 1.3:1 to 4:1, most preferably 1.5:1 to 3:1. The technical effect is to adjust the rheological properties and to reduce the cost of chemicals.

[0258] The first barrier coating composition and the first barrier coating can further comprise one or more additives, such as one or more slip agents, heat stabilizers, anti-blocking agents or antistatic agents and ultraviolet light stabilizers, among others. The technical effect of the additives is to modify the surface and / or optical properties of the first barrier coating.

[0259] The first barrier coating composition 7, and the first barrier coating formed thereby, can comprise a plasticizer, which is a compound or composition capable of imparting plastic flexibility to the heat-sealable packaging material. In one embodiment, the plasticizer is selected from the group consisting of ethylene glycol, glycerol, sorbitol, glucose and mixtures thereof.

[0260] The total amount of natural and biodegradable polymers in the first barrier coating 4 can be at least 50 wt%, such as 54 to 85 wt%, preferably 58 to 75 wt%, more preferably 60 to 70 wt%, calculated on the total dry weight of the first barrier coating 4. The technical effect is to provide biopolymers to fill, for example, the voids between the pigment particles. Other technical effects include obtaining better barrier properties.

[0261] The first barrier coating preferably has a grammage of 2 to 10 gsm, more preferably 3 to 9 gsm, most preferably 4.5 to 7.5 gsm (dry weight). The technical effect is to economically and efficiently improve the barrier properties of the heat-seal packaging material.

[0262] The first barrier coating 4 can have an average thickness in the range of 1.5 pm to 10 pm, preferably in the range of 3 pm to 9 pm, more preferably in the range of 4 pm to 8 pm, most preferably in the range of 4.5 pm to 7 pm. The technical effect is to economically and efficiently obtain protection against oxygen and fat by the first barrier coating. Another technical effect is that the first barrier coating 4 and the second barrier coating create a synergistic effect providing barrier properties to the heat-seal packaging material.

[0263] The first barrier coating composition 7 has a Brookfield viscosity of 100-1500 mPas, preferably 200-1100 mPas, more preferably 300-900 mPas, when measured at 40°C, 100 rpm, with a solid content of 32-40%. The technical effect is that the viscosity is suitable for pumping the coating to a storage tank and a coating unit.

[0264] The second barrier coating

[0265] The heat-seal packaging material 1 comprises a second barrier coating 5.

[0266] One technical effect of the second barrier coating 5 is to provide better water vapor barrier properties. Another technical effect is to provide heat-sealability to the heat-seal packaging material 1. According to the present specification, another technical effect of the second barrier coating is to enhance the fat barrier properties of the heat-seal packaging material by filling possible pinholes. According to the present specification, another technical effect of the second barrier coating is to improve the crack resistance of the barrier coating of the heat-seal packaging material 1.

[0267] The support layer 2b can be coated with the first barrier coating composition 7 and the second barrier coating composition 8, thereby obtaining a heat-seal packaging material 1 comprising a first barrier coating 4 and a second barrier coating 5.

[0268] The heat-seal packaging material 1 comprises a first pre-coating 3a, a first barrier coating 4 and a second barrier coating 5 on the same side of the paper 2a. Preferably, the first barrier coating 4 is on the first pre-coating 3 and the second barrier coating 5 is on the first barrier coating 4. The first barrier coating 4 can be directly on the first pre-coating 3 and the second barrier coating 5 can be directly on the first barrier coating 4. The technical effect is to improve the barrier properties of the heat-seal packaging material.

[0269] The second barrier coating 5 can comprise one or more heat seal polymers. Preferably, the second barrier coating 5 comprises 20 to 60 wt% of heat seal polymers of the total dry weight of the second barrier coating 5. The technical effect is to provide heat sealability as well as improved barrier properties.

[0270] The second barrier coating 5 can comprise at least one latex and / or other polymer dispersion based barrier coating having heat seal properties.

[0271] Preferably, the second barrier coating composition 8 is latex based. Preferably, the second barrier coating 5 comprises 20 to 60 wt% of latex of the total dry weight of the second barrier coating 5. The technical effect is to provide improved barrier properties as well as excellent runnability and high solids capacity.

[0272] If a latex is used, it can be natural latex, synthetic latex or a mixture thereof. Natural latex has better stretch effect, lower tear strength, mechanical strength and biodegradability, while synthetic latex, such as styrene-butadiene latex or styrene-acrylate latex, can be produced on a large scale and is generally less expensive.

[0273] In another embodiment, the polymer dispersion comprises a polymer having suitable heat properties, such as a polyolefin or a polyester. The technical effect is that the selected polymer is able to form an improved barrier layer on the paper surface at typical process temperatures of a paper machine.

[0274] The heat seal polymer can comprise at least one of the following polymers and mixtures thereof:

[0275] - acrylate,

[0276] - ethylene-acrylic acid copolymer,

[0277] - styrene-acrylate copolymer,

[0278] - styrene-butadiene copolymer,

[0279] - polyolefin, and

[0280] - polyester.

[0281] The technical effect is to provide water vapour barrier properties and heat seal properties for the heat seal packaging material.

[0282] Preferably, the heat seal polymer comprises at least one of the following polymers and mixtures thereof:

[0283] - acrylate,

[0284] - styrene-acrylate copolymer,

[0285] - styrene-butadiene copolymer, and

[0286] - polyolefins.

[0287] Technical effects include providing water vapour barrier, improving grease barrier, providing at least moderate oxygen barrier, and providing heat sealability for heat sealable packaging material.

[0288] Most preferably, the heat sealable polymer comprises at least one of the following polymers and mixtures thereof:

[0289] - acrylates, and

[0290] - styrene-acrylate copolymers.

[0291] Technical effects include providing water vapour barrier, improving grease barrier, at least moderate oxygen barrier, and heat sealability, suitable for heat sealable packaging material, and free from polyolefins and the like.

[0292] Thus, the second barrier coating 5 can comprise one of the above heat sealable polymers or a blend of the above heat sealable polymers. Technical effects include providing water vapour barrier, improving grease barrier, and heat sealability, and at least moderate oxygen barrier.

[0293] The dispersed heat sealable polymer, such as latex or polymeric material, has a melting point typically in the range of 60-120 °C and a glass transition temperature equal to or below 23 °C. This enables the film to be formed in a temperature range suitable for drying on a paper machine, while avoiding blocking. Traditionally, this has posed some challenges due to the lack of reel cooling devices in most paper machines. Thus, the temperature of the paper web on the paper machine reel is typically in the range of 40-60 °C. Therefore, the coating layer on the paper web should not be tacky at this temperature, as it could otherwise cause blocking of the reel. With this novel solution, the problem of blocking of the barrier coating on the reel can be avoided.

[0294] The second barrier coating can comprise 3-35 wt%, preferably 5-30 wt%, most preferably 10-25 wt% of a wax. If a wax is used, the wax can comprise at least one of the following:

[0295] - bio-based waxes, such as beeswax, carnauba wax, rice bran wax, rye meal wax, sunflower oil wax, soy wax,

[0296] - bio-based or synthetic Fischer-Tropsch waxes, and

[0297] - synthetic waxes, such as paraffin wax or polyethylene wax.

[0298] Technical effects are to provide improved performance, such as reaching the target water vapour barrier level. Mixing the polymer with a wax can change the physical properties of the coating, in particular the hydrophobic properties.

[0299] The term "soy wax" refers to a natural wax from soy.

[0300] Preferably, if a wax is used, the wax is selected from the group consisting of:

[0301] - bio-based waxes such as beeswax, carnauba wax, rice bran wax, rye bran wax, sunflower oil wax, soy wax, and

[0302] - bio-based fischer-tropsch wax.

[0303] The technical effect of the wax is to increase the bio-based content while maintaining the desired properties.

[0304] The second barrier coating composition and the second barrier coating formed therefrom can also comprise one or more additives such as one or more slip agents, heat stabilizers, anti-blocking agents or antistatic agents and UV stabilizers, etc. The technical effect of the additives is to modify the surface and / or optical properties of the second barrier coating.

[0305] Furthermore, the second barrier coating composition 8 can contain solid, insoluble pigments such as talc, calcium carbonate and / or titanium dioxide to provide, for example, opacity or color.

[0306] In one embodiment, the second barrier coating comprises one or more mineral pigments selected from the group consisting of kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulfate and titanium dioxide.

[0307] The second barrier coating 5 can comprise from 10 to 60 wt%, preferably from 15 to 50 wt%, more preferably from 18 to 40 wt% of mineral pigments, calculated on the total dry weight of the second barrier coating 5. The addition of fillers has benefits in terms of rheology and cost. The pigments can also increase the solid content, thus reducing the energy consumption of the drying section. The addition of pigments in the second coating also facilitates the maintenance of the recyclability of the heat-seal material. Furthermore, it is surprising that the second barrier coating with the addition of said pigments in the selected polymeric material exhibits heat-seal properties suitable for the packaging line.

[0308] Therefore, the second barrier coating composition 8 can comprise at least one platy pigment, preferably talc and / or kaolin. As previously mentioned, platy pigments refer to pigments having a flat structure, where one dimension of the structure is much smaller than the other two. The platy pigments can be selected from the group consisting of kaolin, talc and mica. The technical effect of combining a heat-seal polymer (such as latex) with platy pigments is to further enhance the water and water vapor barrier properties. The second layer, if comprising latex and platy pigments, provides excellent water and moisture barrier properties, especially in high humidity environments, so that when the coated paper is used for packaging products for storage and / or shipping to high humidity areas (such as humid subtropical climate zones), the packaged products can be well protected from external moisture.

[0309] In a preferred embodiment, the second barrier coating comprises talc.

[0310] In a preferred embodiment, the second barrier coating comprises kaolin.

[0311] Advantageously, the second barrier coating 5 comprises at least 50 wt.%, preferably at least 60 wt.%, more preferably at least 70 wt.%, most preferably at least 90 wt.% of kaolin, calculated on the basis of all mineral pigments in the second barrier coating 5. Kaolin is readily dispersible in water, improving the ease of manufacturing process, while providing the advantages of a platelet-shaped pigment.

[0312] The grammage of the second barrier coating is preferably 3 to 12 gsm, more preferably 4 to 10 gsm, most preferably 4.5 to 8 gsm (dry weight). The technical effect is to economically and efficiently improve the barrier properties of the heat-sealable packaging material.

[0313] The thickness of the second barrier coating 5 can be in the range of 2 pm to 10 pm, preferably in the range of 3 pm to 9 pm, more preferably in the range of 4 pm to 8 pm, most preferably in the range of 4.5 pm to 7 pm. The technical effect is to economically and efficiently obtain good grease and water vapor resistance, as well as at least moderate protection against oxygen, with the second barrier coating.

[0314] The total amount of heat-sealable polymer in the second barrier coating 5 can be at least 40 wt.%, such as 40 to 95 wt.%, preferably 50 to 90 wt.%, more preferably 55 to 85 wt.%, most preferably 60 to 80 wt.%, calculated on the basis of the total dry weight of the second barrier coating 5. The technical effects include filling the inter-particle voids and obtaining improved barrier properties. A further technical effect is to provide heat-sealability.

[0315] The second barrier coating 5 can form the uppermost barrier coating of the heat-sealable packaging material. Thus, the second barrier coating 5 can form the uppermost coating of the heat-sealable packaging material.

[0316] In an embodiment, there can be printing on the second barrier coating 5.

[0317] In a preferred embodiment, the heat-sealable packaging material has a barrier coating on the first side of the support layer, and a second pre-coating 3b (preferably designed for printing) on the second side of the paper 2a.

[0318] Heat-sealable packaging material

[0319] As previously described, the heat-sealable packaging material has a support layer 2b, a first barrier coating 4, and a second barrier coating 5.

[0320] Preferably, the first barrier coating 4 is located between the support layer 2b and the second barrier coating 5, and the second barrier coating 5 is located on top of the first barrier coating 4.

[0321] The heat-seal packaging material has at least one, preferably only one, side comprising the first barrier coating 4 and the second barrier coating 5. Preferably, the heat-seal packaging material has the barrier coatings 4, 5 only on the first side of the support layer 2b. The technical effect is to reduce the environmental load, such as carbon dioxide load, and to provide an economically efficient, environmentally friendly heat-seal barrier material.

[0322] The other side of the heat-seal packaging material can only have, for example, the second pre-coating 3b. However, the first barrier coating 4 and / or the second barrier coating 5 can also be provided on both sides of the support layer 2b.

[0323] The second pre-coating 3b can be a surface sizing layer. The second pre-coating 3b can consist of one or more binders. Alternatively, the second pre-coating can comprise a binder and a pigment.

[0324] Thus, the second side of the support layer can be

[0325] - uncoated, for example calendered, or

[0326] - coated.

[0327] If the heat-seal packaging material has a coating on the second side of the paper 2a, the coating on the second side of the paper 2a is preferably the second pre-coating 3b.

[0328] The heat-seal packaging material can have at least one side designed for printing. The printable side is preferably capable of being printed using at least one of the following methods:

[0329] • digital printing, such as digital inkjet printing,

[0330] • flexographic printing,

[0331] • gravure printing, and

[0332] • offset lithography.

[0333] Thus, preferably, the heat-seal packaging material is a printable heat-seal packaging material. The technical effect is to improve the simplicity of the printing process of a package comprising the heat-seal packaging material.

[0334] In an advantageous embodiment, the heat-seal packaging material comprises a barrier coating 4, 5 on the first side of the support layer and the second side of the support layer comprises printing. In this embodiment, the second side of the support layer preferably comprises a second pre-coating 3b on the paper 2a and the second side of the support layer is preferably configured to be printable. The technical effect is that the barrier layer can provide suitable barrier properties to the packaging, which has the barrier layer on the first side of the support layer, while the printing on the other side of the packaging can provide information to the user of the packaging. Alternatively, the second pre-coating 3b can be configured to cover a pigment coating and printing.

[0335] The heat-seal packaging material can have

[0336] - a support layer 2b comprising a paper 2a,

[0337] - a first barrier coating 4 comprising:

[0338] - a first binder, preferably selected from starch, hemicellulose and mixtures thereof, and

[0339] - a second binder, preferably comprising PVA and / or EVOH,

[0340] and

[0341] - a second barrier coating 5, preferably comprising a dispersible heat-seal polymer.

[0342] The technical effect is to provide an environmentally friendly heat-seal packaging material with good barrier properties.

[0343] Thus, the heat-seal packaging material can comprise two barrier layers, wherein the first barrier layer can provide the basis for grease and oxygen barrier properties and the second barrier layer can provide water vapour barrier properties and enhance the grease and oxygen barrier properties.

[0344] Thanks to the use of the new heat-seal packaging material, it is possible to achieve barrier properties without using extrusion-coated or laminated layers, nor using metal layers.

[0345] The heat-seal packaging material is preferably suitable for recycling in the fibre stream according to PTS METHOD PTS-RH 021 / 97, class 2, October 2012.

[0346] Furthermore, when the heat-seal packaging material is contaminated with food residues, the heat-seal packaging material is preferably suitable for composting and / or incineration after use, without causing environmental problems.

[0347] In this specification, the term "polymeric binder" refers to the binder of the first barrier coating and the heat-seal polymer of the second barrier coating.

[0348] The heat-seal packaging material preferably comprises at least 30% biodegradable polymer binder, more preferably at least 40% biodegradable polymer binder, most preferably at least 50% biodegradable polymer binder, the content being determined in relation to the biodegradability of the reference material according to ISO 14851.

[0349] In general, the organic material of the first barrier coating is preferably at least 85% biodegradable, more preferably at least 90% biodegradable, most preferably at least 93% biodegradable, determined in relation to the biodegradability of the reference material according to ISO 14851.

[0350] The polymer binder preferably comprises at least 20% bio-based binder, more preferably at least 30% bio-based binder, most preferably at least 40% bio-based binder, the content being determined in relation to the total amount of polymer binder, i.e. the total amount of binder of the first barrier coating and heat-seal polymer of the second barrier coating.

[0351] As mentioned previously, the term "bio-based" refers to "derived from plants and other renewable agricultural, marine, and forestry materials". Furthermore, the term "bio-based" refers to the origin of the raw material, which has not been chemically modified (except for hydrolysis). Modified starch is an exception, which can be modified to a low degree, meaning that the degree of substitution is below 0.1. The degree of substitution (DS) refers to the average number of hydroxyl groups per anhydrous glucose unit (AGU) in the starch that are substituted.

[0352] The heat-seal packaging material preferably comprises less than 80%, more preferably less than 70%, most preferably less than 60% fossil-based polymer binder, the content being determined in dry weight of all polymer binders in the heat-seal packaging material.

[0353] The manufacturing process according to the present specification can be greatly simplified compared to traditional manufacturing processes. Typically, the support layer is shipped from the paper mill to a converter, who adds barrier material, e.g. by extruding plastic onto the paper, as the paper mill does not necessarily have an extruder, and the coated paper is then shipped to another converter / printer, who finally produces the finished product. In the method according to the present specification, the barrier coating can be completed at the paper mill or at the site of only one converter / printer, thereby avoiding at least one processing step and shipping stage, making the entire manufacturing process more efficient.

[0354] The heat-seal packaging material can provide both grease- and water-vapor barrier properties to foldable or flexible packaging products, which properties are difficult to achieve with traditional methods (without the use of metal foils and laminated films), especially for foldable or flexible packaging products.

[0355] Furthermore, especially if the first barrier coating 4 uses starch with a high consistency and the second barrier coating 5 uses latex or a polymer dispersion, the drying time can be shortened, thereby increasing the production efficiency, especially in case of adding pigments.

[0356] The hot-seal packaging material can have a WVTR value of less than 100 g / m 2 *day, determined at 23°C / 85% RH according to ISO 2528. A technical effect is to provide the obtained hot-seal packaging material with the required water vapour barrier properties in an economically efficient way. Another technical effect is to provide an environmentally friendly material comprising bio-based materials.

[0357] The hot-seal packaging material can have an improved mineral oil barrier property (HVTR method, heptane vapour transmission rate) of less than 20 g / m*day, more preferably less than 15 g / m*day, most preferably less than 10 g / m*day. A technical effect is to improve the mineral oil barrier property in an economically efficient way, thereby avoiding the risk of mineral oil contamination when using the packaging material, e.g. a food packaging material. The mineral oil barrier property of the hot-seal packaging material is especially useful for food. Another technical effect is to provide an environmentally friendly material, since a material without a laminated film or an aluminium layer can be used for the hot-seal packaging material.

[0358] The hot-seal packaging material can have a fat barrier property of more than 60 hours, determined according to ASTM F119-82 using chicken fat at 40°C. A technical effect is to provide the hot-seal packaging material with a fat barrier property in an economically efficient way. Another technical effect is to provide an environmentally friendly material, since a material without a laminated film or an aluminium layer can be used for the hot-seal packaging material.

[0359] The hot-seal packaging material can have an oxygen value of less than 1000 cc / m 2 *day, more preferably less than 700 cc / m 2 *day, more preferably less than 500 cc / m 2 *day, more preferably less than 300 cc / m 2 *day, most preferably less than 100 cc / m 2 *day. A technical effect is to provide the hot-seal packaging material with an oxygen barrier property in an economically efficient way. Another technical effect is to provide an environmentally friendly material, since a material without a laminated film or an aluminium layer can be used for the hot-seal packaging material.

[0360] The heat-sealable packaging material preferably has heat-seal properties as determined according to the heat-sealability test. As previously mentioned, the heat-sealability is tested according to ASTM F2029-16 by cutting a 15 x 120 mm specimen from the heat-sealable packaging material and performing a coating-to-coating seal. In the present application, the term "heat-sealable" particularly refers to a seal strength (N / 15 mm) of at least 3 N / 15 mm, preferably more than 4 N / 15 mm, or more preferably more than 5 N / 15 mm, which is measured using a tensile testing machine according to ASTM F88 / F88M-15.

[0361] The heat-seal properties can be determined by using a dwell time of 1.0 seconds at a sealing pressure (i.e. jaw pressure) of 0.6 bar. Thus, the heat-sealable packaging material is preferably heat-sealable at 150°C using a jaw pressure of 0.6 bar and a dwell time of 1.0 seconds.

[0362] The heat-sealable packaging material according to the present specification is preferably heat-sealable at 150°C using a reduced jaw pressure of 0.2 bar and a reduced dwell time of 0.5 seconds. Furthermore, the heat-sealable packaging material is heat-sealable at 160°C using a jaw pressure of 0.2 bar and a dwell time of 0.5 seconds.

[0363] The heat-sealable packaging material is heat-sealable at 140°C using a jaw pressure of 0.2 bar and a dwell time of 0.5 seconds. The heat-sealable packaging material is preferably heat-sealable at 130°C using a jaw pressure of 0.2 bar and a dwell time of 0.5 seconds. A technical effect is to provide good sealing barrier properties in an economically efficient way. Furthermore, the sealing time required for heat-sealing is short, which can increase the efficiency of the packaging process.

[0364] Furthermore, the heat-sealable packaging material is preferably heat-sealable at 150°C using any jaw pressure of 0.2 bar to 1.6 bar and any dwell time of 0.5 seconds to 1.0 seconds.

[0365] In a preferred embodiment, the heat-sealable packaging material is heat-sealable at least at a temperature of 120°C to 160°C. A technical effect of the heat-sealability is to provide good sealing barrier properties in an economically efficient way. Furthermore, the heat-sealable packaging material 1 is capable of heat-sealing at all temperatures of 120°C to 160°C, which can enhance the process flexibility of the packaging, and thus, for example, heat-sensitive printing can be used, or for example, a heat-sensitive product can be packaged using a package comprising the heat-sealable packaging material.

[0366] In one embodiment, the heat-sealable packaging material 1 consists at least essentially of a support layer, a first barrier coating, and a second barrier coating.

[0367] Compared to conventional environmentally friendly heat-sealable materials, the use of the heat-sealable packaging material can significantly improve the barrier properties against oxygen, mineral oil and water vapor. In addition, the heat-sealable packaging material can have good sealing ability, and thus can effectively provide good barrier properties at a lower sealing cost.

[0368] Manufacturing method

[0369] The method of manufacturing the heat-sealable packaging material can comprise the following steps:

[0370] - providing a support layer 2b comprising a paper 2a and a first pre-coat layer 3a on the paper 2a,

[0371] - applying a first barrier coating composition 7 in the form of an aqueous dispersion to the support layer 2b, thereby forming a first barrier coating layer 4, and

[0372] - applying a second barrier coating composition 8 in the form of an aqueous dispersion to the first barrier coating layer 4, thereby forming a second barrier coating layer 5.

[0373] The support layer 2b can be made by a paper machine. The support layer 2b can be calendered.

[0374] The paper 2a is suitably coated by a pre-coating unit to apply the pre-coating composition 6, 6a, 6b. The pre-coating unit can be one of a knife coater, an immersion roll coating unit, a nozzle unit, a short dwell unit, a rod coater, an airbrush coater, a film transfer coater, a curtain coating unit or a spray coating unit.

[0375] The first barrier coating composition 7 can be applied on the support layer 2b by a first barrier coating unit 10 for applying the first barrier coating composition 7. The first barrier coating composition 7 can be applied in the form of an aqueous composition. The first barrier coating unit 10 can be one of a knife coater, an immersion roll coating unit, a nozzle unit, a short dwell unit, a rod coater, an airbrush coater, a film transfer coater, a curtain coating unit or a spray coating unit.

[0376] The second barrier coating composition 8 can be applied by a second barrier coating unit 11 to apply the second barrier coating layer. The second barrier coating composition 8 can be applied in the form of an aqueous composition. The second barrier coating unit 11 can be one of a knife coater, an immersion roll coating unit, a nozzle unit, a short dwell unit, a rod coater, an airbrush coater, a film transfer coater, a curtain coating unit or a spray coating unit.

[0377] Packaging

[0378] The packaging can be produced using the heat-sealable packaging material.

[0379] The package can comprise, consist essentially of, or consist of a heat sealable packaging material. In one embodiment, the proportion of heat sealable material in the package exceeds 50% by weight, for example at least 60% by weight (on a dry weight basis).

[0380] The package can comprise a heat sealable material, for example in combination with another paper or film, or other paper or film, in a laminate structure.

[0381] Thus, in one embodiment, a heat sealable packaging material is used in the packaging laminate.

[0382] The package can be produced using packaging machinery designed for soft packaging. Such packaging machinery includes form-fill-seal (FFS) machines that produce packages in a vertical or horizontal direction, bag-making machines, lidding machines, and seal and overwrap machines.

[0383] It will be fully appreciated by those skilled in the art that several different package forms can be produced using these types of packaging machinery.

[0384] Experimental testing

[0385] Example 1

[0386] The starch samples were prepared by conventional cooking of a modified starch (Starch 1), or by enzymatic conversion of native wheat starch (Starches 2 and 3). Table 1 shows the molecular weight distribution of the starch samples by describing the average molecular weight and polydispersity.

[0387] Table 1. Molecular weight distribution data and viscosity of the starch samples tested.

[0388]

[0389] Example 2

[0390] The coating compositions were prepared in a batch mixer for pilot scale trials. The properties of the coating compositions are shown in Table 2.

[0391] Table 2. Properties of the coating compositions

[0392]

[0393] The solid content of the starch-containing coating compositions was all above 30%, and most of them had a Brookfield viscosity (100 rpm) in the range of 300-600 mPas. Even a solid content of 38.3% was shown. There is still room for using higher solid contents, since the viscosity level can reach a range of 700-1200 mPas. This is an advantage compared to the possible solid content range of the reference coating composition with PVA as the only binder, which showed a solid content of 25.2%. The selection of PVA for products that comply with the standards for food contact materials is limited. This limits the use of PVA to high viscosity qualities only. All the listed coating compositions were suitable for blade coating in a pilot coating machine. Thus, the use of a large proportion of modified or enzymatically converted starch together with PVA has an advantage in terms of solid content, which in turn determines the achievable coating weight or the energy consumption during drying.

[0394] Comparative Example 1

[0395] Coating tests were performed in a pilot experiment on paper substrates, the pre-coat comprising binder and flake pigment.

[0396] The first barrier coating comprised different proportions of the starch samples of Example 1, polyvinyl alcohol (hydrolysis degree 98%) and flake pigment. Measurements of the applied coating weight, water uptake (Cobb 60 ), water vapour transmission rate (WVTR), grease resistance and heptane vapour transmission rate (HVTR) were performed for all test points (Table 3). Oxygen transmission rate (OTR) was measured for selected test points.

[0397] Table 3. Test point description and barrier properties of paper with pre-coat and first barrier coating.

[0398]

[0399] 1 Water uptake determined as Cobb 60s value, relative humidity 50%, temperature 23°C, standard ISO 535

[0400] 2 Water vapour transmission rate, relative humidity 50% or 85%, temperature 23°C, ISO 2528 standard

[0401] 3 Oxygen transmission rate, relative humidity 50%, temperature 23°C, ASTM D3985-05 standard

[0402] 4 Grease resistance, 40°C, using chicken fat, ASTM F119-82 standard

[0403] 5Heptane permeability, 50% relative humidity, 23°C, according to the method described above

[0404] The paper coated with the first pre-coat and the first barrier coat showed an improvement in barrier properties to grease, with OTR levels below 376 cc / (m 2 d), optimally 175 cc / (m 2 d). All samples showed excellent barrier properties to mineral oil, measured as heptane vapor transmission rate (HVTR). HVTR values below 70 g are expected to correlate with values below the migration limit of 0.5 mg / kg for low fat / oil content (≤ 4% fat / oil) dry foodstuffs.

[0405] However, at higher humidity (50% humidity compared to 85% humidity), the water vapor barrier properties decreased. Furthermore, due to the structure of the pre-coat and the first barrier coat on the paper, heat seal properties could not be obtained. The grease resistance of PVA was not superior compared to starch / PVA blends (used as adhesive) with starch contents up to 80 wt.%.

[0406] Example 3

[0407] The samples of the test points in Comparative Example 1 were coated on a pilot scale using a coating composition comprising latex, natural wax and pigment.

[0408] Measurements of applied coat weight, water uptake (Cobb 60 ), water vapor transmission rate and grease resistance were performed on all test points (Table 4). Oxygen transmission rate was measured on selected test points.

[0409] Table 4. Test point description and barrier properties of paper with first pre-coat, first barrier coat and second barrier coat.

[0410]

[0411] 1 Water uptake was determined as Cobb 60s value, 50% relative humidity, 23°C, standard ISO 535

[0412] 2 Water vapor transmission rate, 85% relative humidity, 23°C, ISO 2528 standard

[0413] 3 Oxygen transmission rate, 50% relative humidity, 23°C, ASTM D3985-05 standard

[0414] 4 Grease resistance, 40°C, using chicken oil, ASTM F119-82 standard

[0415] 5 Heptane permeability, 50% relative humidity, 23°C, according to the method described above

[0416] The paper coated with the first pre-coat, the first barrier coat and the second barrier coat showed further improvement in barrier properties to oil and fat, reaching values > 5 days, while the maximum value for the paper without the second barrier coat was 3.6 days and for the reference sample with only the pre-coat and the second barrier coat was 1.9 days. The OTR levels remained below 310 cc / (m 2 d) at several test points below 200 cc / (m 2 d), an improvement compared to the reference sample with only the pre-coat and the second barrier coat. All samples showed excellent barrier properties to mineral oil, measured as heptane vapour transmission rate (HVTR).

[0417] The second barrier coat significantly improved the water vapour barrier properties at 85% humidity, reaching values below 90 (m 2 d). The second barrier coat also introduced heat sealability.

[0418] In the first barrier coat, the content of starch as binder was up to 80%, and even at a pigment content of up to 41% in the first barrier coat, corresponding values were obtained.

[0419] Example 4

[0420] Heat sealability tests were performed on the material of Example 3 (paper sample with the first pre-coat and the first and second barrier coats). Table 5 shows the maximum force at tear and at adhesion.

[0421] Table 5. Heat sealability of heat seal packaging material (paper with first pre-coat, first barrier coat and second barrier coat).

[0422]

[0423] The heat sealability of the heat seal packaging material was excellent with high seal strength and good adhesion. All the sealed samples showed full fibre tear in the visual evaluation of the seal area.

[0424] Example 5

[0425] Table 6 shows the content of bio-based binder and biodegradable binder of Example 3 at the test points.

[0426] Table 6. Bio-based content and biodegradable content in the first barrier coat and the second barrier coat of the heat seal packaging material.

[0427]

[0428] 1 The content of bio-based binder in the first and second barrier coating is w-% / w-% of the total binder; here bio-based means starch and / or bio-based wax.

[0429] Minimum content - no bio-based content in the second barrier coating

[0430] Maximum content - 20% bio-based content in the second barrier coating

[0431] 2 The content of biodegradable binder in the first and second barrier coating is w-% / w-% of the total binder.

[0432] Minimum content - no biodegradable content in the second barrier coating

[0433] Maximum content - 20% biodegradable content in the second barrier coating

[0434] The bio-based and biodegradable binder content of all polymeric binders in the first and second barrier coating was evaluated.

[0435] The content of bio-based material (in the examples starch and bio-based wax) was higher than 25% in all cases, higher than 35% in many test points with good barrier properties, and higher than 45% in some test points. The advantage of high starch content in the first barrier coating resulted in a significant increase in bio-content in the heat-seal material barrier layer.

[0436] The content of biodegradable material (in starch, PVA and bio-based wax) was higher than 41% in all cases, higher than 50% in many test points with good barrier properties, and higher than 60% in some test points. It was proven that a high amount of biodegradable binder can be incorporated in the barrier layer.

[0437] Example 6

[0438] The heat-seal packaging material (with first pre-coating and first and second barrier coating according to Example 3) was tested for recyclability according to PTS method PTS-RH 021 / 97 (October 2012). The test results are summarized in Table 7.

[0439] Table 7. Recycle test results of heat-seal packaging material. Number of test points according to Example 3.

[0440]

[0441] The heat-seal packaging material was classified as recyclable according to PTS method PTS-RH 021 / 97 (October 2012). The sieve residue was below 1 w-%.

[0442] Example 7

[0443] The heat-seal packaging material (from Example 3, with the first pre-coat layer and the first and second barrier coating layers) was tested for packaging using a commercial vertical form-fill-seal (VFFS) machine, without any modification of the machine.

[0444] The operating window of the VFFS machine was determined based on the results of the laboratory heat-seal test (Example 4).

[0445] For the experiments, the heat-seal temperature range for the horizontal seal of pillow bag packaging was chosen to be 100 to 160 °C, and the heat-seal temperature range for the longitudinal seal was chosen to be 100 to 180 °C. The dwell times used for the horizontal and longitudinal seals were 0.15 s, 0.3 s, 0.5 s, 0.7 s and 1.0 s, and 0.3 s, 0.5 s, 0.7 s, 1.0 s and 1.5 s, respectively.

[0446] The produced bags were tested for seal integrity by visually evaluating the seal area and the three points (i.e. the intersection of the horizontal and longitudinal seals). Figure 7a - l shows the test results for the VFFS machine packaging test. Figure 7a - the full color areas with black in them indicate the operating window for the sample.

[0447] Figure 7a - b shows the test results for the reference point (i.e. sample-013). Figure 7c - d shows the test results for sample-015. Figure 7e - f shows the test results for sample-017. Figure 7g - h shows the test results for sample-019. Figure 7i - j shows the test results for sample-021. Figure 7k - l shows the test results for sample-047.

[0448] Based on the VFFS machine test, the heat-seal packaging material can be used to produce pillow bag type airtight packaging according to this specification.

[0449] The present application is not limited only to the examples presented in the attached drawings and in the above description, but can be modified within the scope of the attached claims.

Claims

1. A method of manufacturing a heat-seal packaging material (1), the method comprising: - providing a support layer (2b) comprising paper (2a) comprising natural fibers comprising cellulose, the support layer (2b) further comprising a first pre-coat layer (3a) on a first side of the paper (2a), wherein the grammage of the first pre-coat layer (3a) is in the range of 1 g / m 2 to 10 g / m 2 , and - providing a first coating layer (4a) on the first pre-coat layer (3a), wherein the first coating layer (4a) comprises a binder and a filler, and wherein the filler is present in an amount of 10 to 90 wt.-%, based on the total weight of the first coating layer (4a), and - providing a second coating layer (4b) on the first coating layer (4a), wherein the second coating layer (4b) comprises a binder and a filler, and wherein the filler is present in an amount of 10 to 90 wt. - applying a first barrier coating composition (7) on the support layer (2b), the composition being in the form of an aqueous dispersion, the solid content of the aqueous dispersion preferably being 30-45 wt%, Thereby a first barrier coating (4) is formed, which has a coating weight of 2 to 10 g / m 2 and comprises at least 45 wt.-% of the total dry weight of the first barrier coating (4) of a binder, wherein - the first binder of the first barrier coating composition (7) being selected from the group consisting of starch, hemicellulose and mixtures thereof, and - the second binder of the first barrier coating composition (7) being selected from the group consisting of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, alginate, chitosan and mixtures thereof, - applying a second barrier coating composition (8) in the form of an aqueous dispersion onto the first barrier coating (4), thereby forming a second barrier coating (5) having a coating weight of 4 to 12 g / m 2 , the second barrier coating composition (8) comprising a dispersed heat-seal polymer, which constitutes at least 45 wt% of the total dry weight of the second barrier coating layer (5), wherein the dispersed heat-seal polymer is selected from the group consisting of - acrylate, - ethylene-acrylic acid copolymer, - styrene-acrylate copolymer, - styrene-butadiene copolymer, - polyolefin, - polyester, and - mixtures thereof.

2. A heat-seal packaging material (1) comprising: A) A support layer (2b) comprising paper (2a) containing natural fibers containing cellulose, the support layer (2b) further comprising a first pre-coating layer (3a) on a first surface of the paper (2a), wherein the basis weight of the first pre-coating layer (3a) is 1 g / m². 2 Up to 10 g / m 2 Within the scope, and B) a first barrier coating (4) having a coating weight of 2 to 10 g / m 2 and comprises at least 45 wt.-% of the total dry weight of the first barrier coating (4) of a binder, wherein - the first binder of the first barrier coating composition (7) is selected from the group consisting of starch, hemicellulose and mixtures thereof, and - the second binder of the first barrier coating composition (7) is selected from the group consisting of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, alginate, chitosan and mixtures thereof, and C) a second barrier coating (5) having a coating weight of 4 to 12 g / m 2 and comprises at least 45 wt.-% of a heat-sealable polymer of the total dry weight of the second barrier coating (5), wherein, the heat-seal polymer is selected from the group consisting of - acrylate, - ethylene-acrylic acid copolymer, - styrene-acrylate copolymer, - styrene-butadiene copolymer, - polyolefin, - polyester, and - mixtures thereof, wherein - the first pre-coating layer (3a) is located between the paper (2a) and the first barrier coating layer (4), and - the first barrier coating layer (4) is located between the first pre-coating layer (3a) and the second barrier coating layer (5).

3. The method of claim 1 or the heat-seal packaging material of claim 2, wherein, The total amount of hemicellulose, polyvinyl alcohol, ethylene-vinyl alcohol copolymer and starch is at least 70 wt%, preferably at least 80 wt%, more preferably at least 90 wt%, most preferably at least 95 wt% (by dry weight) determined from the total dry weight of the binders in the first barrier coating layer.

4. The method or heat-seal packaging material of any of the preceding claims, wherein, The support layer (2b) also comprises a second pre-coat layer (3b) on the second face of the paper (2a), the grammage of the second pre-coat layer (3b) being in the range 1 g / m 2 to 10 g / m 2 .

5. The method or heat-seal packaging material of any of the preceding claims, wherein, The second binder is selected from the group consisting of polyvinyl alcohol and ethylene-vinyl alcohol copolymer.

6. The method or heat-seal packaging material of any of the preceding claims, wherein, The first binder comprises starch, the starch having a degree of polymerization of 100 to 3000.

7. The method or heat-seal packaging material of any of the preceding claims, wherein, The first binder comprises hemicellulose, the hemicellulose having a degree of polymerization of 50 to 300.

8. The method or heat-seal packaging material of any of the preceding claims, wherein, The ratio of the first binder to the second binder is 9.5:1 to 1:1, preferably 4:1 to 2:

1.

9. The method or heat-seal packaging material of any of the preceding claims, wherein, The heat-seal polymer is selected from the group consisting of: - styrene-acrylate copolymer, - styrene-butadiene copolymer, and - polyolefin, preferably the heat-seal polymer is selected from the group consisting of styrene-acrylate copolymer and styrene-butadiene copolymer.

10. The method or heat-seal packaging material of any of the preceding claims, wherein, All coating layers of the heat-seal packaging material (1) are nanocellulose and aluminium free coating layers.

11. The method or heat-seal packaging material of any one of the preceding claims, wherein - the mineral pigment content of the first barrier coating layer (4) is 20 wt% to 55 wt%, and / or - the mineral pigment content of the second barrier coating layer (5) is 10 wt% to 55 wt%.

12. The method or heat-seal packaging material of any of the preceding claims, wherein, The oxygen barrier value of the heat-seal packaging material (1) is less than 1000 cc / m 2 * day, more preferably less than 700 cc / m 2 * day, most preferably less than 500 cc / m 2 * day, the value being determined at 23°C / 50% relative humidity according to the ASTM D3985-05 standard.

13. The method or heat-seal packaging material of any of the preceding claims, wherein, The heat-sealable packaging material (1) has a mineral oil barrier, determined as described in the specification by the heptane vapour transmission rate, which is less than 20 g / m*day, more preferably less than 15 g / m*day, most preferably less than 10 g / m*day.

14. The method or heat-seal packaging material of any of the preceding claims, wherein, The water vapour barrier value of the heat-sealable packaging material (1) is less than 100 g / m 2 * day, the value being determined at 23°C and 85% relative humidity according to the ISO 2528 standard.

15. The method or heat-seal packaging material of any of the preceding claims, wherein, The heat-sealable packaging material (1) has a fat barrier of more than 60 hours, determined at 40°C using chicken fat according to ASTM F119-82 standard.

16. The method or heat-sealable packaging material of any of the preceding claims, wherein - the heat-sealable packaging material (1) is heat-sealable at 150°C, determined at a sealing pressure of 0.6 bar using a dwell time of 1.0 second, and / or - the heat-sealable packaging material (1) is heat-sealable at 150°C, determined at a sealing pressure of 0.5 bar using a dwell time of 0.5 second.

17. The method or heat-seal packaging material of any of the preceding claims, wherein, The heat-sealable packaging material (1) is recyclable in a fibre stream according to PTS method PTS-RH021 / 97 October 2012, class 2.

18. The method or heat-seal packaging material of any of the preceding claims, wherein, The binder of the first barrier coating (4) has a biodegradation rate in water of more than 50 wt% within two months and more than 70 wt% within three months, determined according to ISO 14851 standard.

19. The method or heat-seal packaging material of any of the preceding claims, wherein, The total amount of natural and biodegradable polymers in the first barrier coating (4) is at least 50 wt%, calculated on the total dry weight of the first barrier coating.

20. The method or heat-seal packaging material of any of the preceding claims, wherein, The biodegradable content of the barrier coating (4, 5) is at least 30%, determined by the total amount of binder of the first barrier coating and heat-sealable polymer of the second barrier coating.

21. The method or heat-seal packaging material of any of the preceding claims, wherein, At least 85% of the organic material of the first barrier coating is biodegradable, determined according to ISO 14851 standard.

22. The method or heat-seal packaging material of any of the preceding claims, wherein, The heat-sealable packaging material is a binder-free material.

23. The method or heat-seal packaging material of any of the preceding claims, wherein, The heat-sealable packaging material is free of recycled fibres and filaments.

24. The method or heat-seal packaging material of any of the preceding claims, wherein, The furnish used for the paper is free of highly refined cellulose.

25. The method or heat-seal packaging material of any of the preceding claims, wherein, The paper is free of recycled fibres from used beverage cartons (UBC).

26. A package comprising the heat-sealable packaging material (1) of any of the preceding claims 2 to 25, for example a package comprising a laminate structure of the heat-sealable packaging material (1) of any of the preceding claims 2 to 25.

27. Use of the heat-sealable packaging material (1) of any of the preceding claims 2 to 25 for packaging, preferably for a laminate structure of a package.

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