Laminated packaging material and packaging container made from the laminated packaging material

Abstract

The present invention relates to a non-foil, carton-based laminate packaging material (10) suitable for heat-sealable packaging of oxygen-sensitive products comprising a barrier-coated BOPP polymer film (12) and packaging containers made from the laminate packaging material.

Description

[Technical field]

[0001] The present invention relates to a laminated non-foil packaging material for packaging oxygen-sensitive products such as liquid, semi-liquid or viscous foods, comprising a bulk layer of paper, paperboard or other cellulosic material, a first outermost liquid-tight heat-sealable polymeric layer, a second innermost liquid-tight heat-sealable polyethylene layer, and a barrier-coated polymeric film between the bulk layer and the second innermost liquid-tight heat-sealable polyethylene layer, and to packaging containers made from this laminated packaging material. [Background technology]

[0002] Single-use packages for liquid foods are often manufactured from paperboard or carton-based packaging laminates. One such commonly used package is sold under the trademark "Tetra Brik Aseptic" and is primarily employed for the aseptic packaging of liquid foods such as milk, fruit juices, etc., sold for long-term ambient storage. The packaging material of this known package is usually a laminate comprising a bulk or core layer of paper, paperboard or other cellulose-based material and a liquid-tight outer layer of thermoplastic. To make the package gas-tight, and in particular oxygen-tight, for the purposes of aseptic packaging or packaging of, for example, milk or fruit juice, these laminates usually comprise at least one additional layer, most commonly aluminum foil.

[0003] The inside of the laminate, i.e. the side intended to face the food contents filled in a container made from the laminate, has an innermost layer applied onto the aluminum foil, which may comprise one or more partial layers comprising adhesive polymers and / or heat-sealable thermoplastic polymers such as polyolefins. To ensure interlayer adhesion and package integrity, the aluminum foil is usually laminated directly adjacent to a functionalized polyolefin-based adhesive, i.e. a polyolefin copolymer or graft polymer with a low amount of functional groups, to enhance the adhesive properties to the adjacent layer surfaces.

[0004] Also outside the bulk layer is an outermost heat-sealable polymer layer, preferably a polyolefin homopolymer such as LDPE.

[0005] Packaging containers are generally produced by modern high-speed packaging machines of the type that form, fill and seal packages from webs of packaging material or prefabricated blanks. The packaging containers are produced by joining the longitudinal edges of a web of laminate packaging material together at overlap joints by welding together the inner and outer heat-sealable thermoplastic polymer layers, converting it into a tube. The tube is filled with the desired liquid food product and then divided into individual packages by repeatedly transversely sealing the tube at a predetermined distance from each other below the level of the contents in the tube. The packages are separated from the tube by scoring along the transverse seals and formed into the desired geometric shape, usually a parallelepiped, by creating creases in the packaging material along pre-prepared crease lines. Each package may be equipped with an opening device, such as a screw cork, before or after filling, forming and sealing the container.

[0006] The main advantage of this continuous tube forming, filling and sealing packaging process concept is that the web can be continuously sterilized just before tube formation, offering the possibility of an aseptic packaging process, i.e. a process in which the liquid contents to be filled and the packaging material itself are reduced from bacteria and the filled packaging containers are produced under clean conditions so that they can be stored for long periods even at ambient temperature without risk of microbial growth in the filled product. Another important advantage of Tetra Brik® type packaging processes is that they allow continuous high speed packaging, which, as mentioned above, has a great impact on cost efficiency.

[0007] Packaging containers for sensitive liquid foods, such as milk and juice, can also be produced from sheet blanks or preassembled blanks of the laminate packaging material of the invention. Packages are produced from flat-folded tubular blanks of the packaging laminate by first assembling the blanks to form an open tubular container capsule, one open end of which is closed by folding and heat sealing an integral end panel. The container capsule thus closed is filled from the other open end with a food product, such as juice, and is then closed by further folding and heat sealing the corresponding integral end panel. Examples of packaging containers produced from sheet and tubular blanks are the conventional so-called gable top packages. Packages of this type can also be provided with a molded plastic top and / or a screw cap.

[0008] The aluminum foil layer of the packaging laminate provides a gas barrier that is significantly better than other gas barrier materials. Conventional aluminum foil-based packaging laminates for aseptic packaging of liquid foods have inherent barrier properties against water vapor, light, aromas, flavors and even acidic substances, and at their performance level, are the most cost-effective packaging materials available on the market. The thickness of the aluminum foil is typically 6-9 μm. Furthermore, the aluminum foil allows for heat sealing or heating of the laminate material by induction within the aluminum foil.

[0009] Other materials that compete with foil-based materials need to be cost effective in terms of raw materials, have comparable food preservation properties, and require similarly low complexity in converting the material into the finished packaging laminate.

[0010] Among the efforts to develop non-aluminium foil materials for liquid food carton packaging, there is also a general drive to develop prefabricated films and sheets with advanced, multiple barrier properties, including not only oxygen and gas barrier properties, but also water vapor, chemical and aroma barrier properties.

[0011] The earlier US Patent No. 558,075 describes a laminate packaging material for liquid carton packaging, which comprises a carton or paperboard, as well as a barrier-coated biaxially oriented film of polyethylene terephthalate (BOPET) or polypropylene (BOPP) coated with a silicon oxide (SiOx) coating. The carton and barrier layer are laminated to a thermoplastic polymer of low density polyethylene (LDPE) and an unspecified adhesive layer.

[0012] International Patent Publication WO 2013 / 041469 A1, of a more recent publication date, describes certain simultaneous biaxially oriented films having a base or core layer of BOPP, skin layers of ethylene vinyl alcohol copolymer (EVOH), and an optional barrier coating, which are employed in the barrier coating film of a liquid carton laminate packaging material for the aseptic packaging of liquid foods, where the film is laminated to the carton and to a polyethylene layer.

[0013] However, there remains a need for improved laminate packaging materials for liquid carton packaging that include such gas barrier coated polymeric film substrates. Summary of the Invention [Problem to be solved by the invention]

[0014] It is therefore an object of the present invention to provide a non-aluminium foil based ("non-foil") laminate packaging material for packaging oxygen sensitive products, e.g. food products, in particular liquid, semi-liquid, viscous or moist foods, which has good gas barrier properties and allows good integrity of the filled and sealed packaging containers made from the laminate packaging material.

[0015] More specifically, it is an object of the present invention to provide such a laminated packaging material which, when processed into a packaging container for liquid, semi-liquid or viscous food, has good gas barrier properties, good interlayer adhesion and good heat sealability.

[0016] It is a further object to provide such a non-aluminium foil-based ("non-foil") laminate packaging material that has good recyclability and sustainability, i.e., that meets the needs of future sustainable packaging materials for packaging oxygen-sensitive products.

[0017] A further object is to provide a heat sealable non-foil laminate packaging material and packaging containers made therefrom that allows for long term sterile storage under ambient conditions of liquid, semi-liquid or viscous food products.

[0018] These objects are achieved according to the present invention by a non-foil laminate packaging material, a method for producing the non-foil laminate packaging material, and a packaging container produced from the laminate packaging material, as defined in the appended claims. [Means for solving the problem]

[0019] According to a first aspect of the present invention, there is provided a non-foil laminate packaging material for packaging oxygen sensitive food such as liquid, semi-liquid or viscous food, the packaging material comprising a bulk layer of paper, paperboard or other cellulosic material, a first outermost liquid-tight, heat-sealable polymer layer, a second innermost liquid-tight, heat-sealable polyethylene layer, and disposed inside the bulk layer of paper or paperboard towards the inside of a packaging container made from the packaging material, and between the bulk layer and the second innermost liquid-tight, heat-sealable polyethylene layer, a barrier coated polymer film comprising a polypropylene polymer (PP) film substrate and a vapor deposition gas barrier coating, the second innermost liquid-tight, heat-sealable polyethylene layer comprising a barrier coated polymer film comprising a polypropylene polymer (PP) film substrate and a vapor deposition gas barrier coating, the second innermost liquid-tight, heat-sealable polyethylene layer being bonded to a non-coated surface of the barrier coated polymer film by a first adjacent bonding layer of linear low density polyethylene (m-LLDPE) produced in the presence of a single-site catalyst such as a metallocene catalyst or a constrained geometry catalyst.

[0020] The second innermost liquid-tight heat-sealable polyethylene layer may be selected from the group consisting of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), linear low density polyethylene polymerized by a constrained geometry catalyst such as a single-site catalyst such as a metallocene catalyst (m-LLDPE) and blends of two or more of the said polyethylenes. Preferably, the second innermost layer is a blend of LDPE and m-LLDPE, most preferably a blend of 60-80 wt% m-LLDPE and 20-40 wt% LDPE. This may further be a blend of 4-8 g / m2 of polyethylene comprising or consisting predominantly of m-LLDPE. 2 15-25 g / m by coextrusion coating with a first adjacent bonding layer applied at 2 , for example 16 to 22 g / m 2 It can be applied with

[0021] The described configuration of the thermoplastic polymer layer applied to the inside of the barrier coated polymer film shows improved interlayer integrity and adhesion of the resulting package, especially to support the overall integrity of the package filled with liquid beverages or food. In packaging heavy products such as liquids, it is very important to have a strong seal and good interlayer adhesion in and around the sealing area of ​​the package. The claimed inner layer configuration has been proven to provide the strongest inner layer adhesion and laminate integrity ever seen in this type of laminate.

[0022] The polypropylene polymer film substrate may be selected from the group consisting of films based on non-oriented, uniaxially or biaxially oriented polypropylene (PP, OPP, BOPP) films or multi-layer films having a core or main layer comprising any of said polymers. The most common and preferred polypropylene polymer film substrates are the biaxially oriented films, i.e. BOPP films.

[0023] The vapor deposition gas barrier coating may be selected from coating materials consisting of one or more of aluminum oxide (AlOx), silicon oxide (SiOx), carbon-containing silicon oxide (SiOxCy), amorphous diamond-like carbon coating (DLC), or aluminum metallization.

[0024] In a second aspect of the present invention, there is provided a packaging container comprising the laminate packaging material of the first aspect. According to an embodiment, the packaging container is at least partially manufactured from the laminate packaging material of the present invention, and according to a further embodiment, consists entirely of the laminate packaging material of the present invention.

[0025] (Detailed Description) The term "long-term storage" as used in the context of the present invention means that the packaging container is capable of preserving the quality, i.e. nutritional value, hygienic safety and taste, of the packaged food at ambient temperature conditions for at least 1 or 2 months, such as at least 3 months, preferably 6 months, such as 12 months or more.

[0026] The term "package integrity" generally refers to the tightness of the package, i.e., the resistance of the packaging container to leakage or breakage. The term encompasses the resistance of the package to the ingress of bacteria, dirt, and other microorganisms that may deteriorate the food contained therein and shorten the expected shelf life of the package.

[0027] One major contribution to the integrity of a laminate packaging material comes from good internal adhesion between adjacent layers of the laminate material. Another contribution comes from the resistance of the material to defects such as pinholes, ruptures, etc. in each material layer itself, and yet another contribution comes from the strength of the seal joints where the material is sealed when the package is formed. Thus, with respect to the integrity of the laminate packaging material itself, the focus is primarily on the adhesion of each laminate layer to its adjacent layers as well as the quality of the individual material layers. With respect to the sealing of the package, the focus is primarily on the quality of the seal joints, which is ensured by a well-functioning and robust heat-sealing operation in the filling machine, and further by the properly adapted heat-sealing properties of the laminate packaging material.

[0028] The term "liquid, semi-liquid or viscous food" generally refers to food that contains flowable contents and optionally solids. Non-limiting examples of contemplated foods include dairy products, milk, soy, rice, grain, seed drinks, juices, nectars, soft drinks, energy drinks, sports drinks, coffee or tea drinks, coconut water, wine, soup, crushed tomatoes, sauces (such as pasta sauces), legumes, olive oil, etc.

[0029] Other examples of oxygen-sensitive foods that can be packaged and protected with the laminate packaging materials of the present disclosure include, for example, dry foods and / or fatty foods.

[0030] The term "sterile" in relation to packaging materials and containers refers to a state in which microorganisms have been removed, inactivated, or killed. Examples of microorganisms include bacteria and spores. Generally, when a product is filled aseptically into a packaging container, an aseptic process is used. In order to maintain the sterility during the shelf life of the packaging container, the integrity properties of the package are very important. For the long-term storage of the filled food, and also to preserve the original taste and nutritional value, e.g., vitamin C content, it is important to have a barrier property against gases such as oxygen gas and vapors.

[0031] The term "bulk layer" usually refers to the "core layer" or the thickest layer or layer containing the most material in a multi-layer laminate, i.e. the layer that contributes most to the mechanical properties and dimensional stability of the laminate and the structural stability of the packaging container folded from the laminate, e.g. paper, paperboard or carton. It can also refer to the layer that provides a larger thickness distance in the sandwich structure, which further interacts with stabilizing facing layers with higher Young's modulus on both sides of the bulk layer to achieve sufficient structural stability of the formed packaging container.

[0032] The term "non-foil" packaging material refers to laminate packaging materials that do not contain aluminum foil with a thickness in the micrometer range, such as conventional aluminum foil for liquid carton packaging, which is usually 6-9 μm thick. However, "non-foil" packaging materials may contain a metallized layer, for example because the thickness of the aluminum metallized layer is in the nanometer range. The amount of aluminum material used in such metallized coatings is very small, which, compared to aluminum foil, significantly reduces the impact on recycling and material resource development.

[0033] OTR was measured using a coulometric sensor-based Oxtran 2 / 21 (Mocon) instrument according to ASTM F1927-14 and ASTM F1307-14.

[0034] The method for measuring OTR is to determine the amount of oxygen passing through a material per surface and time unit at a given temperature, a given atmospheric pressure, and a fixed time, i.e., 20 atmospheres, or 100% oxygen atmosphere expressed as 0.2 atmospheres or 1 atmosphere (oxygen), during a 24-hour period. Reference is made to the examples for a detailed description of the relevant OTR test method.

[0035] Thus, for purposes of the laminated non-foil packaging material of the present invention, the bulk layer of the laminate material is a layer of paper or paperboard or other cellulose-based material that provides bending stiffness, resistance to in-plane compression to the laminate material, and supports the dimensional stability of the packaging container in which it is employed.

[0036] The paper or paperboard bulk layer used in the present invention typically has a thickness of about 100 μm to about 600 μm and a surface weight of about 100 to 500 g / m 2 , preferably about 200 to 300 g / m 2 and may be conventional paper or paperboard of suitable packaging quality.

[0037] For low-cost, long-term, aseptic packaging of liquid foods, thinner packaging laminates with thinner paper core layers can be used. Packages made from such packaging laminates are more like pillow-shaped flexible pouches rather than collapsible. Papers suitable for pouch packaging typically have a surface weight of about 50 to about 140 g / m2. 2 , preferably about 70 to about 120 g / m 2 , more preferably about 70 to about 110 g / m 2 It is.

[0038] The bulk layer is bonded to the barrier coating surface of the barrier coated polymer film by a second contiguous bonding layer, which may be a thermoplastic polymer. The most cost-effective and preferred thermoplastic polymer for the second contiguous bonding layer is low density polyethylene (LDPE), which can be applied in thicknesses of 15-25 g / m by melt extrusion lamination of the barrier coated polymer film and the bulk layer. 2 , for example 16 to 22 g / m 2, may be applied to each side of a second adjacent polymeric bonding layer.

[0039] Thus, the bonding layer may be formed by melt extrusion laminating a bonding polymer layer between a web of the bulk layer and a web of the cellulose-based substrate and simultaneously pressing the three layers together while advancing through a lamination roller nip, thereby bonding the bulk layer to the barrier coated cellulose-based substrate by extrusion lamination to provide a laminate structure.

[0040] Suitable thermoplastics for the outermost and innermost heat-sealable liquid-tight layers are polyolefins such as homopolymers or copolymers of polyethylene and polypropylene, preferably polyethylene, more preferably polyethylene selected from the group consisting of low density polyethylene (LDPE), linear LDPE (LLDPE), single-site metallocene catalyzed linear low density polyethylene (m-LLDPE) and blends or copolymers thereof. According to one embodiment, the first outermost protective and liquid-tight layer is LDPE and the second innermost heat-sealable liquid-tight layer is a blend composition of m-LLDPE and LDPE for optimal lamination and heat sealing properties.

[0041] The same thermoplastic polyolefin-based materials, particularly polyethylene, listed for the first outermost and second innermost layers are also suitable as bonding layers within the laminate material, i.e., between a bulk or core layer, such as paper or paperboard, and a barrier film or sheet.

[0042] According to an alternative embodiment, a suitable polymer for the second interlayer tie layer may be, for example, a modified polyolefin, mainly based on LDPE or LLDPE copolymers, or a graft copolymer with functional group-containing monomer units, such as carboxyl or glycidyl functional groups, for example (meth)acrylic acid monomers or maleic anhydride monomers (i.e. ethylene acrylic acid copolymers (EAA) or ethylene methacrylic acid copolymers (MAH)). For example, (meth)acrylic acid monomers or maleic anhydride (MAH) monomers (i.e. ethylene acrylic acid copolymers (EAA) or ethylene methacrylic acid copolymers (EMAA)), ethylene-glycidyl (meth)acrylate copolymers (EG(M)A) or MAH-grafted polyethylene (MAH-g-PE). Another example of such modified or adhesive polymers are so-called ionomers or ionomeric polymers. Preferably, the modified polyolefin is ethylene acrylic acid copolymers (EAA) or ethylene methacrylic acid copolymers (EMAA).

[0043] From a recycling standpoint, simple homopolymer low density polyethylene (LDPE) is preferred and advantageous.

[0044] For recycling purposes and material sustainability, it is advantageous to use only one type of polymer in the packaging material, such as a polyolefin polymer with similar properties and compatibility, and the recycled blend fraction of such polymers can easily find a second premium purpose or use. Since the gas barrier coating and optional surface layer constitute only a small portion of the total material, even if the laminate packaging material of the present invention is fiberized and recycled, the recycled material will only produce two streams: cellulose fiber and polyolefin polymer. This is an improvement over existing gas-tight laminate materials, in which multiple different materials are mixed into the packaging material as a mixed layer or multi-layer laminate, which is difficult to separate.

[0045] According to one embodiment, the first outermost liquid-tight heat-sealable polymer layer may be composed of a polyethylene polymer selected from the group consisting of low density polyethylene (LDPE), medium density polyethylene (MDPE), and any blends thereof. The ... 2 , for example 10-13g / m 2 Preferably, the liquid-tight heat-sealable polymer is LDPE.

[0046] The polypropylene polymer film substrate of the barrier coated polymer film may have a thickness of 12 to 25 μm, such as 15 to 23 μm, for example 15 to 20 μm, to obtain optimum mechanical strength, integrity, barrier properties and cost-effectiveness of the laminate material of the present invention.

[0047] The polypropylene polymer film substrate may further include a skin layer on one surface thereof configured to receive a vapor deposition gas barrier coating. The skin layer may comprise a vinyl alcohol-based polymer, such as ethylene vinyl alcohol copolymer (EVOH), polyvinyl alcohol (PVOH), etc. Such a skin layer is defined as being applied to or melt processed together with the polypropylene core of the film substrate at a thickness substantially less than the polypropylene core layer, and then stretched, i.e. oriented, together with the core layer. The resulting film is substantially thinned overall by the stretching operation, so that the skin layer thickness may be as low as 0.5-2 μm.

[0048] Such skin layers may contribute some oxygen barrier due to the inherent oxygen barrier properties of the EVOH or PVOH polymer and may constitute a receptive surface for a subsequently applied barrier coating, and are therefore sometimes referred to as high surface energy (HSE) layers because they impart a high surface energy to the surface of the polypropylene polymer film substrate, allowing for good adhesion with subsequent vapor deposited coatings.

[0049] The barrier coating coated onto the barrier coated polymer film may be applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as plasma enhanced chemical vapor deposition (PECVD).

[0050] In one embodiment, the vapor deposition coating is a material selected from metals, metal oxides, inorganic oxides, and carbonaceous vapor deposition coatings.

[0051] In a further embodiment, the barrier deposition coating is a deposition coating selected from the group consisting of aluminum metallization coatings and aluminum oxide (AlOx).

[0052] Such thin vapor-deposited coating layers have a nanometer thickness, i.e., most preferably a thickness countable in nanometers, for example 5-500 nm (50-5000 Å), such as 5-200 nm, more preferably 5-100 nm, for example 5-50 nm.

[0053] Generally, below 5 nm the barrier properties may be too low to be useful, and above 200 nm, e.g. above 100 nm, e.g. above 50 nm, depending on the type of vapor deposition coating, the barrier coating may be less flexible, more susceptible to cracking when applied to flexible substrates, and more expensive.

[0054] In one embodiment, the barrier deposition coating may be applied to a thickness of from 10 to 80 nm, such as from 10 to 50 nm, for example from 10 to 45 nm.

[0055] Examples of vapor deposition coatings include aluminum oxide (AlOx, Al2O3) and silicon oxide (SiOx) coatings.

[0056] Such coatings may be applied by plasma-enhanced chemical vapor deposition (PECVD), where vapors of compounds are deposited on the substrate in a more or less oxidizing environment. Silicon oxide coatings (SiOx), for example, may be applied by PECVD processes and can obtain very good barrier properties under certain coating conditions and gas recipes.

[0057] DLC defines a type of amorphous carbon material (diamond-like carbon) that exhibits some of the typical properties of diamond. Preferably, a hydrocarbon gas such as acetylene or methane is used as the process gas of the plasma to produce the coating of amorphous hydrogenated carbon barrier layer, i.e. DLC, applied by PECVD vacuum process. DLC coating applied by PECVD under vacuum provides good adhesion to adjacent polymer layers or adhesive layers in laminate packaging materials. In particular, polyolefins, especially polyethylene and polyethylene-based copolymers, provide good adhesion to adjacent polymer layers.

[0058] Generally, thin coatings of metals or mixtures of metals and metal oxides provide both oxygen and water vapor barrier properties and may be used where the desired function is to prevent oxygen and / or water vapor migration into and through a multilayer film or packaging laminate. Preferably, for purposes of producing food packaging materials, the metal of the metallized or inorganic metal coating is aluminum (Al).

[0059] In one embodiment, the aluminum vapor deposition layer is applied to have an optical density (OD) of 1.8 or more, for example, 1.8 to 3.5, for example, 2.0 to 3.0. If the optical density is less than 1.8, the barrier properties of the metallized film may be rather poor.

[0060] Optical density is measured using a densitometer (Macbeth, Tobias, etc.) that uses the principle of diffuse light transmission. This device is suitable for measuring the optical density value of aluminum vapor deposition films. The measurement precision and accuracy are high, about ±0.2 OD and about ±0.01 OD, respectively, within the measurement range of 0 to 6.60 OD.

[0061] Alternatively, laboratory measurements may be performed using a spectrophotometer to measure the light transmittance over the entire visible spectrum (380-800 nm). The optical density can be calculated from the light transmittance (T) value at 560 nm as follows: OD = -log 10 (I / I 10 The values ​​obtained are as accurate (±0.2 OD) as those obtained by a light transmittance densitometer and are equivalent.

[0062] The vapor-deposited gas barrier coating of the barrier-coated polymer film may further have a topcoat applied by wet solution or dispersion coating and subsequent drying, which provides further inherent barrier properties and also covers and "repairs" imperfections in the initially applied vapor-deposited coating. The topcoat may comprise a vinyl alcohol-based polymer, such as ethylene vinyl alcohol copolymer (EVOH) or polyvinyl alcohol (PVOH). Alternative topcoats include or consist of acrylic polymers. Additionally, they may include low amounts of inorganic materials dispersed or partially incorporated into the composition, such as clay filler materials or sol-gel materials. Thus, a topcoat may be applied in a separate coating step over the vapor-deposited barrier coating of the barrier-coated polymer film, further enhancing the barrier properties.

[0063] In a further embodiment, the opposite, non-coated side of the polypropylene polymer film substrate has a skin layer comprising a copolymer comprising ethylene and propylene, and optionally a third comonomer, such as an ethylene-propylene copolymer or a terpolymer comprising ethylene, propylene and butylene. These polymers have low melting temperatures, allowing for low heat sealing temperatures and allowing the polypropylene core or main layer to remain geometrically or dimensionally stable during the sealing operation. This layer can be surface treated (flame, plasma, corona) to provide the desired surface energy for further film application steps.

[0064] The laminate packaging material produced according to the above provides good adhesion and interaction between adjacent layers in the laminate structure, and good quality of the gas barrier coating and the vapor deposition barrier coating, thereby providing good integrity when transformed into a filled packaging container. An important conclusion, especially in packaging for liquids and wet foods, is that the interlayer adhesion within the laminate packaging material, as well as the oxygen gas barrier properties, can be maintained even under wet packaging conditions.

[0065] According to further embodiments, packaging containers formed from the laminated packaging material may be partially sealed, filled with a liquid or semi-liquid food product, and then sealed by sealing the packaging material itself, optionally in combination with a plastic opening or package top.

[0066] In conclusion, a robust and reliable package for shelf-stable liquid food packaging can be obtained with the barrier coated polymeric film defined by the present invention and the laminated packaging material comprising the same. This laminated packaging material structure works well for forming into a folded and molded package due to both the improved adhesion between the polypropylene polymeric film substrate and the inner heat sealable thermoplastic layer and the improved integrity of the heat sealed portion of the formed package.

[0067] ( Examples and Description of the Preferred Embodiments Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. [Brief description of the drawings]

[0068] [Figure 1] FIG. 1 is a schematic diagram illustrating a cross-section of a non-foil laminate packaging material of the present invention comprising a barrier-coated polymeric film laminated to a cellulose-based bulk layer. [Figure 2a] FIG. 2 is a schematic diagram showing a method for melt extrusion laminating two webs. [Figure 2b] FIG. 2 is a schematic diagram illustrating a method of melt (co)extrusion coating layers of thermoplastic polymers onto a web substrate to form the innermost and outermost layers of the packaging laminate of the present invention. [Figure 3a] FIG. 2 is a diagram showing a typical example of a packaging container made from a laminate packaging material according to the present invention. [Figure 3b] FIG. 2 is a diagram showing a typical example of a packaging container made from a laminate packaging material according to the present invention. [Figure 3c] FIG. 2 is a diagram showing a typical example of a packaging container made from a laminate packaging material according to the present invention. [Figure 3d] FIG. 2 is a diagram showing a typical example of a packaging container made from a laminate packaging material according to the present invention. [Figure 4] FIG. 1 illustrates the principle of how packaging containers are produced from packaging laminate in a continuous roll-fed, form, fill and seal process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] Working Example A laminate material having the main layer configuration as shown in Table 1 was produced, and the adhesion between the first adjacent bonding layer of the inner layer and the back side of the barrier-coated BOPP film was measured. / / Outer LDPE 12g / m 2 / Paperboard 80mN / Second adjacent bonding layer LDPE 20g / m 2 / Barrier coating / Film substrate BOPP / X / (70:30 blend of mLLDPE and LDPE) 19g / m 2 / /

[0070] Layer X, if used, represents the first adjacent bonding layer of mLLDPE of the present invention and has a density of about 6 g / m 2 was applied.

[0071] Previous tests have also attempted to orient the barrier-coated polymer film in the other direction, i.e. with the gas barrier coating facing the second innermost heat-sealable layer. As a result, the barrier coating had to face towards the bulk layer, and a sufficiently good adhesion to the second adjacent bonding layer of LDPE, which bonds the bulk layer to the barrier-coated polymer film, was achieved by appropriate surface treatment of the types of barrier coatings tested (aluminum metallization, AlOx-, SiOx-, SiOxCy-coatings). As a result, the adhesion of the barrier coating to the LDPE bulk-barrier adjacent bonding layer was comparable to the corresponding adhesion in the Al foil reference laminate. The adhesion level at that layer interface is slightly less critical than that of the inner side of the barrier-coated film, i.e. against the inner layer. There is little or no migration of vapor, moisture or molecular substances from the filled product towards this interface, since the barrier coating is also a migration barrier to such compounds and molecules. Additionally, orienting the barrier coating towards the bulk layer has the added benefit of providing better protection from damage during handling of the laminate material during lamination and packaging machine operations.

[0072] The laminate materials were conditioned at 23° C. and 50% RH for at least 24 hours before adhesion measurements.

[0073] The adhesion measurements were performed at room temperature using a 180° peel force tester (Instron). The peel speed was 100 mm / min. The measurements were performed at 23°C and 50% RH. Thus, the peeling was performed at the interface between the uncoated side of the BOPP film and the inner layer, and the peel arm was the inner film. The adhesion force is in N / m and is the average of five measurements.

[0074] The results of the adhesion measurement are shown in Table 1.

[0075] [Table 1]

[0076] From the adhesion measurements it can be concluded that the optimal innerlayer configuration, with an mLLDPE layer adjacent between the backside of the barrier-coated BOPP film and the innermost liquid-tight, heat-sealable layer, provides sufficient innerlayer adhesion and internal integrity of the laminate material.

[0077] Direct extrusion coating of the innermost layer with a blend of mLLDPE and LDPE clearly demonstrated insufficient adhesion between the backside of the BOPP film and the inner heat-sealable layer. The traditionally used ethylene acrylic acid copolymer (EAA), representative of an olefin-based adhesive polymer with carboxyl functionality, did not perform at all in this location of the laminate material. Using traditional LDPE as the adjacent bonding layer, adhesion levels improved somewhat, but were still insufficient in this location of the laminate. It has been found that with currently manufactured aluminum foil-based materials, an adhesion force of at least 200 N / m is desirable and necessary.

[0078] The very good adhesion of Examples 1 and 2 represents an increase of at least 100 N / m over the benchmark for currently manufactured aluminium foil based materials and was achieved without prior surface treatment.

[0079] Further, with respect to the accompanying drawings: In Fig. 1, a laminated packaging material 10 for packaging oxygen-sensitive products, such as for liquid carton packaging, is shown, which comprises a barrier-coated polymer film 12 to provide the laminated packaging material with gas barrier properties. The polymer film 12 comprises a polymeric film substrate 12a, which is a prefabricated biaxially oriented film of polypropylene (i.e., BOPP film), and a nanometer-thick gas barrier coating 12b applied to one side of the film by a vapor deposition coating method. A separate gas barrier coating 12b applied by dispersion or solution coating onto the polymeric film substrate 12a and then dried is also conceivable. However, a vapor deposition coated barrier coating may provide significantly higher oxygen barrier properties and / or water vapor barrier properties at very low thicknesses (nanometer scale) and high coating quality.

[0080] This laminate material, in this example, has a bending force of 80 mN and a strength of approximately 200 g / m 2 and is therefore suitable for filling, folding and sealing into smaller packages containing liquids or beverages, for example so-called portion packages of 200-250 ml.

[0081] The bulk layer 11 is laminated to the barrier coated side of the barrier coated polymer film 12 by an adjacent or intermediate tie layer 13 of a thermoplastic polymer, most commonly low density polyethylene (LDPE). The intermediate tie layer 13 is formed by melt extrusion as a thin polymer melt curtain between the two webs, so that the bulk layer and the barrier coated polymer film are laminated together as all three layers pass through a chilled press roller nip. The coating weight of the intermediate tie layer 13 is 15-25 g / m 2 , for example 18 to 23 g / m 2 It is.

[0082] The laminate packaging material further comprises an outermost protective material layer, in this case a liquid-tight, heat-sealable polymer layer 16, applied to the outside of the bulk layer 11, which is directed towards the outside of the packaging container produced from the packaging laminate. This layer 16 is transparent to show on the outside any printed decorative pattern 17 that may be printed on the bulk layer of paper or paperboard. The printed decorative pattern may thereby inform the contents of the package, the package brand and other information targeted to consumers in retail establishments or food establishments. The polymer of the outermost layer 16 may be a polyolefin such as a conventional low density polyethylene (LDPE) of heat-sealable quality, or may include further similar polymers including LLDPE. Here, a polyolefin of about 12 g / m 2 It is applied with.

[0083] The innermost liquid-tight and heat-sealable layer 14 is located opposite the bulk layer 11, this layer 14 being directed towards the inside of the packaging container made from the packaging laminate, i.e. this layer 14 is in direct contact with the packaged product. The innermost heat-sealable layer 14, which will form the strong lateral heat seal of the liquid packaging container made from the laminated packaging material, may comprise one or more combinations of polyethylenes selected from the group consisting of LDPE, linear low density polyethylene (LLDPE) and LLDPE made by polymerizing ethylene monomers with C4-C8, more preferably C6-C8, α-olefin alkylene monomers in the presence of a metallocene catalyst, so-called metallocene-LLDPE (m-LLDPE). The innermost liquid-tight and heat-sealable layer 14 has a density of about 18-22 g / m 2 may be applied in an amount of

[0084] Preferably, the innermost heat sealable layer 14 comprises a heat sealable blend of m-LLDPE produced by a single-site catalyst, such as a metallocene catalyst, and LDPE in a weight ratio of 60:40 to 80:20, and has a viscosity of 18 to 22 g / m 2 The innermost heat sealable layer is applied at a basis weight of about 5-7 g / m 2The laminate is then coextrusion coated in the melt state with a second adjacent tie layer 15 of m-LLDPE polymer, which provides good adhesion to the backside of the barrier coated BOPP film 12 .

[0085] The primary method of melt extrusion lamination is shown in Figure 2a: A cellulose-based bulk layer 11 and a barrier-coated polymer film 12 pass as continuous material webs through a lamination nip 21 and are bonded together by an extruder feedblock and bonding layer 22 via adjacent melt extruded polymer layers which exit the nip as a curtain of molten polymer 23. The thus laminated material 24 is sent to a subsequent lamination station or wound up on a roll, not shown.

[0086] FIG. 2b illustrates the process step of the lamination step in the manufacture of the packaging laminate 10 of FIG. 1 after the bulk layer 11 has first been laminated to the barrier coated polymeric film 12 as shown in FIG. 2a.

[0087] The resulting paper prelaminate web 24 is transported from an intermediate storage reel or directly from a lamination station for laminating the bulk layer prelaminate to a barrier coated cellulosic substrate. The non-laminate side, i.e., the printed side 17, of the bulk layer 24 is melt extrusion coated at a chilled roller nip 27 by bonding with a molten polymer curtain 27a of LDPE forming the outermost layer 16 of the laminate material, which is extruded through an extruder feedblock and die 27b. The prelaminate bulk barrier film web, with the outermost layer 16 coated on the printed side, i.e., on the outside, then passes through a second extruder feedblock and die 28b and lamination nip 28 where the molten polymer curtain 28a is bonded and coated on the other side of the prelaminate, i.e., the uncoated side of the barrier coated polymer film substrate 12. Thus, the innermost heat-sealable layer 14, along with the adjacent polymeric bonding layer 15, is melt coextrusion coated onto the backside of the barrier coated film 12, i.e., the inside of the "bulk barrier film" prelaminate web 24, ultimately forming a laminated packaging material 10; 29, which is wound up onto a storage reel (not shown).

[0088] These two co-extrusion steps in the lamination roller nips 27 and 28 may alternatively be carried out as two successive steps in the reverse order.

[0089] According to a different embodiment of the method of the present invention, one or both of the outermost layers 14 or 16 may instead be applied in separate pre-lamination stations, where the co-extrusion coated outermost protective layers 16 and 14, respectively, are first applied to the outside of the (optionally printed) bulk paperboard layer 11 and onto the barrier coated polymer film 12, and finally, the two pre-laminated paper webs may then be laminated to each other by means of adjacent polymer bonding layers 13, as described above in connection with FIG. 2a.

[0090] FIG. 3a shows an embodiment of a packaging container 30a made from a packaging laminate according to the invention. This packaging container is particularly suitable for beverages, sauces, soups, etc. Typically, such packaging containers have a volume of about 100-1000 ml. It may be of any shape, but is preferably brick-shaped, with vertical and horizontal seals 31a and 32a, respectively, and optionally an opening device 33. In another embodiment, not shown, the packaging container may be wedge-shaped. To obtain such a "wedge shape", only the bottom of the package is folded, and the bottom horizontal heat seal is formed so as to be hidden under a triangular corner flap that is folded and sealed against the bottom of the package. The top horizontal seal remains unfolded. In this way, the packaging container, only partially folded, is easy to handle and dimensionally stable enough to be placed on a shelf in a food store or on a flat surface.

[0091] Figure 3b shows an alternative packaging container 30b made from an alternative packaging laminate according to the present invention, which has a thin paper bulk layer that is not dimensionally stable enough to form a parallelepiped or wedge shaped package and no creases are formed after the transverse seal 32b, leaving the package as a pillow bag and distributed and sold in this form.

[0092] Figure 3c shows a gable-top package 30c that is folded and formed from a pre-cut sheet or blank of a laminate packaging material that includes a bulk layer of paperboard and the barrier coated paper substrate of the present invention. Flat-top packages can also be formed from similar blanks.

[0093] Figure 3d shows a bottle-like package 30d which is a combination of a sleeve 34 formed from a pre-cut blank of the laminated packaging material of the present invention and a top 35 formed from injection-molded plastic in combination with an opening device such as a screw cork. Packages of this kind are sold, for example, under the trade names Tetra Top® and Tetra Evero®. These special packages are formed by attaching, in a closed state, a molded top 35 equipped with an opening device to a cylindrical sleeve 34 of laminated packaging material, sterilizing the bottle-top capsule thus formed, filling it with food, and finally folding and sealing the package at the bottom.

[0094] 4 shows the principle described at the beginning of this application: a web of packaging material is formed into a tube 41 by overlapping the longitudinal ends 42, 42' of the web and heat sealing them together to form an overlap joint 43. The tube is continuously filled 44 with the liquid food product to be filled and divided into individual filled packages by repeating double transverse sealing 45 of the tube at predetermined intervals below the level of the filled contents in the tube. The packages 46 are separated by cutting between the double transverse seals (top and bottom seals) and finally formed into the desired geometric shape by forming folds along crease lines prepared in the material.

[0095] Finally, it should be noted that the invention is not limited to the embodiments shown and described above, but that various modifications may be made within the scope of the appended claims.

Claims

1. A non-foil laminate packaging material (10) for packaging oxygen-sensitive foods, such as liquid, semi-liquid or viscous foods, comprising: a bulk layer (11) of paper, paperboard or other cellulose-based material, a first outermost liquid-tight heat-sealable polymer layer (16), and a second innermost liquid-tight heat-sealable polyethylene layer (14); a barrier-coated polymer film (12) disposed inside the bulk layer between the bulk layer and the second, innermost, liquid-tight, heat-sealable polyethylene layer toward the inside of a packaging container made from the packaging material; The barrier-coated polymer film (12) comprises a polypropylene polymer (PP) film substrate (12a) and a gas barrier coating (12b); the second, innermost, liquid-tight, heat-sealable polyethylene layer (14) is bonded to the uncoated surface of the barrier-coated polymeric film (12) by a first adjacent tie layer (15) of linear low density polyethylene (m-LLDPE) produced in the presence of a single-site catalyst, such as a metallocene catalyst, or a constrained geometry catalyst; A non-foil laminate packaging material (10).

2. the second, innermost, liquid-tight, heat-sealable polyethylene layer (14) is selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear low-density polyethylene polymerized by a constrained geometry catalyst, such as a single-site catalyst, e.g., a metallocene catalyst (m-LLDPE), and blends of two or more of the polyethylenes; The non-foil laminate packaging material (10) of claim 1.

3. The second innermost liquid-tight heat-sealable polyethylene layer (14) is coated by co-extrusion coating to a density of 4 to 8 g / m ２ with a first adjacent bonding layer (15) applied at 15-25 g / m The non-foil laminate packaging material (10) of claim 1.

4. the first outermost liquid-tight heat-sealable polymer layer (16) comprises a polyethylene polymer selected from the group consisting of low density polyethylene (LDPE), medium density polyethylene (MDPE), and blends thereof; The non-foil laminate packaging material (10) of claim 1.

5. the polypropylene polymer film substrate (12a) is selected from the group consisting of films based on unoriented, monoaxially or biaxially oriented polypropylene (PP, OPP, BOPP) films or multilayer films having a core layer made of any of the aforementioned materials; The non-foil laminate packaging material (10) of claim 1.

6. the gas barrier coating (12b) is selected from a vapor-deposited coating material consisting of one or more of aluminum oxide (AlOx), silicon oxide (SiOx), carbon-containing silicon oxide (SiOxCy), amorphous diamond-like carbon coating (DLC), or aluminum metallization; The non-foil laminate packaging material (10) of claim 1.

7. the polypropylene polymer film substrate (12a) is adapted to receive a vapor-deposited gas barrier coating (12b) and has a skin layer on one surface thereof made of a vinyl alcohol-based polymer, such as ethylene vinyl alcohol copolymer (EVOH) or polyvinyl alcohol (PVOH); The non-foil laminate packaging material (10) of claim 1.

8. the vapor-deposited gas barrier coating (12b) of the barrier-coated polymer film (12) further comprises a top coating applied by wet solution or dispersion coating and subsequent drying; The non-foil laminate packaging material (10) of claim 1.

9. the opposite, uncoated side of the polypropylene polymer film substrate (12a) has a skin layer comprising a copolymer comprising ethylene, propylene, and optionally a third monomer; The non-foil laminate packaging material (10) of claim 1.

10. The polypropylene polymer film substrate (12a) has a thickness of 12 to 25 μm. The non-foil laminate packaging material (10) of claim 1.

11. the barrier coated surface of said barrier coated polymer film (12) is bonded to the bulk layer (11) by a second adjacent bonding layer (13) of a thermoplastic polymer; The non-foil laminate packaging material (10) of claim 1.

12. the second adjacent bonding layer (13) comprises a polyolefin layer, for example low density polyethylene (LDPE); The non-foil laminate packaging material (10) of claim 11.

13. The second adjacent bonding layer (13) is applied at 15 to 25 g / m2 by means of melt extrusion laminating the barrier coated polymer film (12) and the bulk layer (11) on each side of the second adjacent bonding layer. The non-foil laminate packaging material (10) of claim 11.

14. A packaging container comprising the non-foil laminate packaging material of claim 1.

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