Oxygen Barrier Plastic Material

Abstract

The invention relates to a multilayer packaging film comprising at least three different types of layers (A), (B), and (C): (A) is at least one outer layer, (B) is at least one passive oxygen barrier layer, (C) is at least one active oxygen scavenging layer, characterized in that the at least one outer layer (A) is a thermoplastic polymer; the at least one passive oxygen barrier layer (B) is selected from the group consisting of ethylene vinyl alcohol copolymers, polyvinylchloride, copolymers of polyvinyl chloride, polyvinyl alcohol, polyvinylidene dichloride, copolymers of polyvinylidene dichloride, polyacrylonitrils, copolymers of polyacrylonitrils, polyethylene terephthalate, polyethylene naphthalate, polyethylenefuranoate, polysiloxanes, and polyamides; the at least one active oxygen scavenging layer (C) comprises a) a plastic material which is a polyolefin, a polyolefin copolymer or a polystyrene, and additives (b) and (c), wherein b) is a polyterpenic resin; and c) is a transition metal catalyst

Claims

1. A multilayer packaging film comprising at least three different types of layers (A), (B), and (C): (A) is at least one outer layer, (B) is at least one passive oxygen barrier layer, (C) is at least one active oxygen scavenging layer, wherein the at least one outer layer (A) is a thermoplastic polymer; the at least one passive oxygen barrier layer (B) is selected from the group consisting of ethylene vinyl alcohol copolymers, polyvinylchloride, copolymers of polyvinyl chloride, polyvinyl alcohol, polyvinylidene dichloride, copolymers of polyvinylidene dichloride, polyacrylonitrils, copolymers of polyacrylonitrils, polyethylene terephthalate, polyethylene naphthalate, polyethylenefuranoate, polysiloxanes, and polyamides; and the at least one active oxygen scavenging layer (C) comprises a) a plastic material which is a polyolefin, a polyolefin copolymer or a polystyrene, and additives (b) and (c), wherein b) is a polyterpenic resin; and c) is a transition metal catalyst, and wherein, the additive (b) is used in an amount of from 0.05 to 10% by weight, based on the total weight of the respective active oxygen scavenging layer (C).

2. The multilayer packaging film as claimed in claim 1 wherein the additives b) and c) are combined in the same oxygen scavenging layer.

3. The multilayer packaging film as claimed in claim 1 further comprising at least one inner layer (D) which is a thermoplastic polymer.

4. The multilayer packaging film as claimed in claim 1, wherein at least one of the active oxygen scavenging layers (C) is sandwiched between a passive oxygen barrier layer (B) and an inner layer (D) or, when this is lacking, the inside of the packaging itself.

5. The multilayer packaging film as claimed in claim 3, wherein one or more further layers selected from the group consisting of moisture barrier layers, strengthening layers and adhesive layers are positioned between at least two of the layers (A), (B), (C), and (D).

6. The multilayer packaging film as claimed in claim 1, wherein the polyterpenic resin (b) contains monomers selected form alpha-pinene, beta-pinene, gamma-ter-pinene, limonene, norbornene, myrcene, phellandrene, carvone, camphene, 2-carene, 3-carene, perillyl alcohol, perillyl aldehyde, perillyl acid, alkyl esters of perillyl alcohol, aryl esters of perillyl alcohol, arylalkyl esters of perillyl alcohol, alkylaryl esters of perillyl alcohol, alpha-ionone, beta-ionone, beta-citronellol, beta-citronellene, citronellal, citronellic acid, alkyl esters of beta-citronellol, aryl esters of beta-citronellol, arylalkyl esters of beta-citronellol, alkylaryl esters of beta-citronellol, geraniol, geranial, alkyl esters of geraniol, aryl esters of geraniol, arylalkyl esters of geraniol, alkylaryl esters of geraniol, linalool, alkyl esters of linalool, aryl esters of linalool, arylalkyl esters of linalool, alkylaryl esters of linalool, nerolidol, alkyl esters of nerolidol, aryl esters of nerolidiol, arylalkyl esters of nerolidiol, alkylaryl esters of nerolidiol, verbenol, verbenone, alkyl esters of verbenol, aryl ester verbenol, arylalkyl esters of verbenol, alkylaryl esters of verbenol and mixtures thereof.

7. The multilayer packaging film as claimed in claim 1, wherein the polyterpenic resin (b) is a homopolymer or copolymer of alpha-pinene, beta-pinene or mixtures of alpha/beta pinene.

8. The multilayer packaging film as claimed in claim 1, wherein the transition metal catalyst (c) contains iron, nickel, manganese, cobalt or copper.

9. The multilayer packaging film as claimed in claim 1, wherein the transition metal catalyst (c) is used in an amount of from 0.001 to 1% by weight, based on the total weight of the respective active oxygen scavenging layer (C).

10. The multilayer packaging film as claimed in claim 1, wherein the thickness of the passive oxygen barrier layers in comparison to the total thickness of the multilayer film ranges between 3 to 30%.

11. The multilayer packaging film as claimed in claim 1, wherein the thickness of the active oxygen scavenging layers in comparison to the total thickness of the multilayer film ranges from 9 to 43%.

12. The multilayer packaging film as claimed in claim 1, which is in the form of a container.

13. A method for the manufacture of a multilayer packaging film as claimed in claim 1, comprising the step of providing the polymers according to the layers (A), (B) and (C), providing the additives (b) and (c) and comprising a mixing step and a shape forming process.

14. The method as claimed in claim 13 wherein the additives (b) and (c) are provided in the form of a masterbatch.

15. A method for the manufacture of a multilayer packaging film as claimed in claim 3, comprising the step of providing the polymers according to the layers (A), (B) and (C) and (D), providing the additives (b) and (c) and comprising a mixing step and a shape forming process.

16. The method as claimed in claim 15 wherein the additives (b) and (c) are provided in the form of a masterbatch.

Description

[0050] Having thus described the invention in general terms herein follows a brief explanation of the attached graphs and drawings. When applicable, these are not necessarily drawn to scale. Applicability of the invention to multilayer structures is not to be bound to the following structures only but also to analogous laminated or not-laminated multilayer structures. In the Figures, Passive layer means passive oxygen barrier layer and Active layer means active oxygen scavenging layer.

[0051] FIG. 1. This is a cross-sectional side view of a multilayer film that is in accordance with the present invention. It can be observed that the active oxygen-scavenging layer is sandwiched between the passive oxygen barrier layer and the inside of the packaging or an additional inner/sealant layer. The film might include tie or adhesive layers when required by compatibility issues between different layers.

[0052] FIG. 2. This is a cross-sectional side view of a multilayer film that is in accordance with the present invention. It can be observed that the passive oxygen barrier layer is sandwiched between two active oxygen-scavenging layers. The film might include tie layers between the active layers and the passive barrier layer or between the active layers and the adjacent outer and/or the optional inner layer.

[0053] FIG. 3. This is a cross functional side view of a multilayer films that is in accordance with the present invention. It can be observed that the active oxygen-scavenging layer is sandwiched between two subsequent passive oxygen barrier layers and the inside of the packaging or an additional inner/sealant layer. The film might include tie or adhesive layers when required by compatibility issues between different layers.

[0054] FIG. 4. This is a cross-sectional side view of a multilayer film that is in accordance with the present invention. It can be observed that the active oxygen-scavenging layer is sandwiched between two passive oxygen barrier layers. The film might include tie layers between the outer layer and the first passive barrier layer, the active oxygen-scavenging layer and the two passive barrier layer and the last passive barrier layer and the inner layer.

[0055] FIGS. This is a cross-sectional side view of a multilayer film that is in accordance with the present invention. It can be observed that the passive oxygen barrier layer is sandwiched between two active oxygen-scavenging layers. The film might include tie layers between the outer layer and the first active oxygen-scavenging layer, the passive oxygen barrier layer and the two active oxygen-scavenging layers and the last oxygen-scavenging layer and a polyethylene (PE) layer.

[0056] FIG. 6. This is a cross-sectional side view of a multilayer film that is in accordance with the present invention. It can be observed that two active oxygen-scavenging layers are sandwiched one between two passive barrier layer and one between one of the passive barriers and the outer layer. The film might include tie layers between the outer layer and the first active oxygen-scavenging layer, the first passive oxygen barrier layer and the two active oxygen-scavenging layers, the second oxygen-scavenging layer and the two passive barriers and the last passive barrier and the inner layer.

[0057] FIG. 7. This is a cross-sectional side view of an example of laminated multilayer film that is in accordance with the present invention. It can be seen that a polyvinylidene chloride (from now on PVdC) layer is sandwiched between a PET layer that functions as outer layer and a first active oxygen scavenging layer. The passive oxygen barrier layer is sandwiched between two active oxygen scavenging layers. An inner layer can be optionally present. The film might include tie or adhesive layers when required by compatibility issues between different layers.

[0058] FIG. 8. This is a cross-sectional side view of an example of laminated multilayer film that is in accordance with the present invention. It can be seen that a PVdC layer is sandwiched between a PET layer that functions as outer layer and a first passive barrier layer. The active oxygen scavenging layer is sandwiched between two passive oxygen barrier layers. An inner layer can be optionally present. The film might include tie or adhesive layers when needed.

[0059] Oxygen barrier, as in the present invention, refers to the reduction or elimination of oxygen permeation inside of a packaging article by providing a substance that reacts with, absorbs and/or consumes oxygen. This is known as an active oxygen barrier and differs from the passive oxygen barriers, which attempt to hermetically seal a product away from oxygen. A passive oxygen barrier layer does not always completely impede the permeation of oxygen inside of the packaging but rather slows down its ingress up to a certain extent.

[0060] For all embodiments of this invention, it is preferable for at least one of the active oxygen scavenging layers to be sandwiched between a passive oxygen barrier layer and an inner layer or, when this is lacking, the inside of the packaging itself.

[0061] It is subsequent that all the illustrated embodiments reported in FIG. 1 to FIG. 8 also fall within this definition. In these and other embodiments one or more intermediate layers (e.g. tie or adhesive layers) may be disposed between any of the layers interfaces of the multilayer film and more specifically anywhere the need for binding two layers which otherwise would be incompatible requires their use.

[0062] FIGS. 1 to 8 report a series of possible embodiments of this invention where the various components are combined in a variety of ways in order to produce the multilayer film. The converters of plastic materials normally decide the structure of a multilayer film based of the specific need of the food producers and on the nature of the good that should be contained and protected by the package. It is therefore impossible to cite in this patent every possible multilayer structure that is employed nowadays. Nonetheless, FIGS. 1 to 8 represent configurations that are representative of real packaging structures but do not necessarily comprise all of the embodiments the invention could be applied to.

[0063] The crystalline structure of some of the most commonly used passive barriers significantly alter by exposure to humidity above 65% (when wet foods are packaged or when the packaging is exposed during transportation or storage to such environmental conditions) or temperature above 30? C. (during packaging sterilization processes or environmental conditions of storage and/or transportation). The modification of crystallinity is not a permanent effect, but the material can revert to its original crystalline state if and once the above-mentioned conditions are prevented. The time required for this reversible process to occur can take up to a week or longer. During this time, oxygen is able to permeate through the packaging with faster permeation rates thus shortening the shelf life of the foods or drugs contained within. Normally to limit this from happening, moisture barrier layers have to be interposed between the passive barrier layer and the surface of the film that is exposed to high moisture.

[0064] The oxygen barrier compositions of the invention can be used to produce multilayer films that are able to compensate for the loss of performance of the passive barrier, thus reaching levels of oxygen transmission rate that are similar to those of the same multilayer film that has not been exposed to high humidity and/or temperature.

[0065] Active oxygen scavenging layer (C)

[0066] In general, the active oxygen scavenger layer stops oxygen coming from the outside of the packaging while permeating through the polymer matrix by chemically reacting with it. The same reaction also can occur with oxygen that might have remained trapped inside of the packaging at the moment of sealing/closure thus maintaining constant or lowering the concentration of oxygen inside of the final article for an extended time. An active scavenger layer normally has an absorption capacity that is at least 0.1 cc/(g.sub.scavenger*day).

[0067] Preferred polyolefins and polyolefin copolymers, i.e. component (A) and/or (D) within the meaning of the invention, are thermoplastic polyolefins known in the art and are selected from the group consisting of [0068] polyethylene (PE), preferably selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene low density polyethylene (mLDPE) and metallocene linear low density polyethylene (mLLDPE), [0069] polypropylene (PP), preferably selected from the group consisting of polypropylene homopolymer (PPH), polypropylene random copolymer (PP-R) and polypropylene block copolymers (PP-block-COPO), [0070] PE copolymers, preferably selected from the group consisting of ethylene-vinyl acetate copolymers (EVA), copolymers of ethylene and methyl acrylate (EMA), copolymers of ethylene and butyl acrylate (EBA), copolymers of ethylene and ethyl acrylate (EEA), and cycloolefin copolymers (COC), [0071] general purpose polystyrene (GPPS) and high impact polystyrene (HIPS); more preferably of [0072] high density polyethylene (HDPE) and low density polyethylene (LDPE) polypropylene homopolymer (PPH), general purpose polystyrene (GPPS).

[0073] Preferred polystyrenes, i.e. component (A) and/or (D) within the meaning of the invention, can be a styrene homopolymer, an alkylstyrene homopolymer, preferably a C.sub.1-C.sub.4-alkylstyrene homopolymer, for example ?-methylstyrene homopolymer; a styrene copolymer, especially a high impact polystyrene (HIPS).

[0074] High impact polystyrenes (HIPS) are generally prepared by polymerization by grafting mixtures of styrene and optionally of one or more copolymerizable vinyl monomers, preferably mixtures of styrene, methylstyrene, ethylstyrene, butylstyrene, halostyrenes, vinylalkylbenzenes, such as vinyltoluene, vinylxylene, acrylonitrile, methacrylonitrile, lower alkyl esters of methacrylic acid, in the presence of a rubbery polymer trunk comprising copolymers chosen from polybutadiene, polyisoprene, rubbery styrene-diene copolymers, acrylic rubber, nitrile rubber and olefinic rubbers, such as propylene diene monomer rubber (PDM) and propylene rubber (PR). In the high impact polystyrene, the rubbery polymer trunk normally constitutes from 5 to 80% by weight, preferably 5 to 50% by weight, of the total weight of the grafted polymer.

[0075] The preferred density of component (A) and/or (D) is of from 1.0 to 1.1 g/cm.sup.3, more preferably of from 1.02 to 1.06 g/cm.sup.3, even more preferably of from 1.03 to 1.05 g/cm.sup.3.

[0076] Preferred polystyrenes are polystyrenes with a MFR at 200? C./5 kg according to ISO 1133 of from 0.1 to 300 g/10 min, more preferably of from 1 to 200 g/10 min, even more preferably of from 5 to 100 g/10 min, especially of from 10 to 50 g/10 min, more especially of from 15 to 35 g/10 min, in particular of from 20 to 25 g/10 min.

[0077] The additive (b) being a polyterpene resin contains cyclic or acyclic monomers preferably selected form alpha-pinene, beta-pinene, gamma-ter-pinene, limonene, norbornene, myrcene, phellandrene, carvone, camphene, 2-carene, 3-carene, perillyl alcohol, perillyl aldehyde, perillyl acid, alkyl esters of perillyl alcohol, aryl esters of perillyl alcohol, arylalkyl esters of perillyl alcohol, alkylaryl esters of perillyl alcohol, alpha-ionone, beta-ionone, beta-citronellol, beta-citronellene, citronellal, citronellic acid, alkyl esters of beta-citronellol, aryl esters of beta-citronellol, arylalkyl esters of beta-citronellol, alkylaryl esters of beta-citronellol, geraniol, geranial, alkyl esters of geraniol, aryl esters of geraniol, arylalkyl esters of geraniol, alkylaryl esters of geraniol, linalool, alkyl esters of linalool, aryl esters of linalool, arylalkyl esters of linalool, alkylaryl esters of linalool, nerolidol, alkyl esters of nerolidol, aryl esters of nerolidiol, arylalkyl esters of nerolidiol, alkylaryl esters of nerolidiol, verbenol, verbenone, alkyl esters of verbenol, aryl ester verbenol, arylalkyl esters of verbenol, alkylaryl esters of verbenol and mixtures thereof.

[0078] In other specific embodiments, the polyterpene resins can also be copolymers of unsaturated monoterpenes, such as alpha-pinene, beta-pinene, gamma-ter-pinene, limonene, norbornene, myrcene, phellandrene, carvone, camphene, 2-carene, 3-carene, perillyl alcohol, perillyl aldehyde, perillyl acid, alkyl esters of perillyl alcohol, aryl esters of perillyl alcohol, arylalkyl esters of perillyl alcohol, alkylaryl esters of perillyl alcohol, alpha-ionone, beta-ionone, beta-citronellol, beta-citronellene, citronellal, citronellic acid, alkyl esters of beta-citronellol, aryl esters of beta-citronellol, arylalkyl esters of beta-citronellol, alkylaryl esters of beta-citronellol, geraniol, geranial, alkyl esters of geraniol, aryl esters of geraniol, arylalkyl esters of geraniol, alkylaryl esters of geraniol, linalool, alkyl esters of linalool, aryl esters of linalool, arylalkyl esters of linalool, alkylaryl esters of linalool, nerolidol, alkyl esters of nerolidol, aryl esters of nerolidiol, arylalkyl esters of nerolidiol, alkylaryl esters of nerolidiol, verbenol, verbenone, alkyl esters of verbenol, aryl ester verbenol, arylalkyl esters of verbenol, alkylaryl esters of verbenol,

[0079] with ethylenically unsaturated monomers that are petroleum-based or come from renewable sources such as styrene, alpha-methylstyrene, alkyl acrylates, alkyl methacrylates, vinyl alkonates such as vinyl acetate, vinyl butyrate or the like, ethylene vinyl acetate, styrene-maleic anhydride, and similar monomers.

[0080] Preferred embodiments of additive (b) are polyterpene resins of either homopolymers or copolymers of unsaturated cyclic monoterpenes, such as alpha-pinene, beta-pinene, d-limonene, mixtures of alpha/beta-pinene or the like, and blended combinations thereof.

[0081] In a more preferred embodiment of the present invention, the additive (b) is either a homopolymer or copolymer of alpha-pinene, beta-pinene or mixtures of alpha/beta pinene.

[0082] A particularly preferred additive (b) is a beta-pinene resin, expediently with an average Mw of at least 2500 g/mol.

[0083] Preferably, the additive (b) is used in an amount of from 0.05 to 10%, more preferably 0.1 to 3.5%, most preferably 0.1 to 2%, by weight, based on the total weight of the respective active oxygen scavenging layer (C).

[0084] Additive (c) within the meaning of the invention is a transition metal catalyst that initiates and accelerates the rate of oxygen consumption. The catalyst may or may not be consumed with oxygen, or if consumed, may only be consumed temporarily by converting back to a catalytically active state.

[0085] More preferably, the transition metal catalyst is a salt, with the transition metal selected from the first, second or third transition series of the Periodic Table of the Elements. Suitable metals and their oxidation states include, but are not limited to, manganese II or III, iron II or III, cobalt II or III, nickel II or III, copper I or II, rhodium II, III or IV, and ruthenium. The oxidation state of the metal when introduced does not need necessarily to be that of the active form. The metal is preferably iron, nickel, manganese, cobalt or copper; more preferably manganese or cobalt; and even more preferably cobalt. Suitable counterions for the metal include, but are not limited to, chloride, acetate, acetylacetonate, propionate, oleate, stearate, palmitate, 2-ethylhexanoate, octanoate, neodecanoate or naphthenoate. The metal salt can also be an ionomer, in which case a polymeric counterion is employed. Such ionomers are well known in the art.

[0086] Even more preferably, the salt, the transition metal, and the counterion are either compliant with country regulations in the matter of food contact materials or, if part of a packaging article, exhibit substantially no migration from the oxygen barrier composition to the packaged contents. Particularly preferable salts include cobalt oleate, cobalt propionate, cobalt stearate, and cobalt neodecanoate.

[0087] Preferably, the transition metal catalyst (c) is used in an amount of from 0.001 to 1%, more preferably 0.01 to 0.5%, by weight, based on the total weight of the respective active oxygen scavenging layer (C).

[0088] The thickness of the active oxygen scavenging layers in comparison to the total thickness of the multilayer film can range from 1 to 50%, preferably between 5 to 45%, more preferably between 9 to 43% and even more preferably between 7 to 42%.

[0089] Passive Oxygen Barrier Layer (B)

[0090] A passive barrier normally comprises a polymeric material that cannot react chemically with the oxygen that permeates through a layer made thereof, but rather slows down its ingress by creating a tortuous path for the oxygen molecules to permeate from one side of the packaging at higher oxygen concentration to the other at lower oxygen concentration.

[0091] In the scope of this invention, a passive barrier can include any material that might alter its barrier performance at conditions of temperature and r.h. that exceed the already mentioned thresholds.

[0092] There are many oxygen barrier polymers that can be used as passive oxygen barrier layers. If more than one passive barrier layers are present as in FIGS. 3, 4, 6 and 7, these layers can be the same or different from one another.

[0093] The oxygen barrier polymer can be selected from a group including but not limited to ethylene vinyl alcohol copolymers, polyvinyl chloride and its copolymers, polyvinyl alcohol, polyvinilydene dichloride and its copolymers, polyacrilonitriles and its copolymers, polyethylene terephthalate, polyethylene naphthalate (PEN), polyethylene furanoate (PEF), silicones (SiOx), polyamides such as polycaprolactam (nylon 6), meta-xylene adipamide (MXD6), hexamethylene adipamide (nylon 66), amorphous polyamides, such as nylon 6I,6T, and also copolymers and blends of the above.

[0094] Preferred polymers are ethylene vinyl alcohol copolymers and polyamides such as polycaprolactam (nylon 6), meta-xylene adipamide (MXD6), hexamethylene adipamide (nylon 66).

[0095] Alternative material that classify as a passive oxygen barrier layers also include metal foil layers, metal coatings or metal depositions, metal oxides like silica, alumina, nano clays and vermiculate.

[0096] The thickness of the passive oxygen barrier layer can vary widely according to the number of other layers, functionality and desired performance and can range from 1 to 100 ?m, preferably between 1.5 to 50 ?m, more preferably between 2 to 10 ?m and even more preferably between 3 and 5 ?m.

[0097] The thickness of the passive oxygen barrier layers in comparison to the total thickness of the multilayer film can range from 1 to 50%, preferably between 2 to 40%, more preferably between 3 to 30% and even more preferably between 4 to 10%.

[0098] Outer Layers (A) and Inner Layers (D)

[0099] The inner layer of a multilayer film is defined here as the layer which is directly exposed to the content of the packaging. This layer normally functions as sealant layer since it is responsible for ensuring the heat-sealing and subsequent airtight isolation of the goods contained inside when adhering to a support article like for instance a tray, another film or, as in a pouch, to the multilayer film itself. Within the embodiments of this invention, the inner layer may therefore comprise a single polymeric material or a blend thereof.

[0100] The term outer layer is defined above.

[0101] Both the inner or outer layer may be the same or different in material which may include thermoplastic polymers like polyolefins, polystyrenes, polyurethanes, polyvinyl chloride and ionomers. Polymeric material useful in this respect include homo- and copolymers of ethylene and propylene such as, but not limited to, low density polyethylene, ethylene/alpha-olefin copolymers, medium density polyethylene, linear low density polyethylene, linear medium density polyethylene, very low density polyethylene, ultra-low density polyethylene, polypropylene homopolymer and polypropylene copolymer. The mentioned polymers can be prepared with many different procedures and catalysts and can be either homogeneous or heterogeneous.

[0102] The thickness of the inner layer or of the outer layer in comparison to the total thickness of the multilayer film can range from 1 to 50%, preferably between 5 to 45%, more preferably between 14 to 44% and even more preferably between 15 to 42%.

[0103] Each of the layers (A), (B), (C) and (D) may also comprise further customary additives (d) like compatibilizers, antioxidants (different from the oxygen scavenger (b)), heat stabilizers, colorants, fillers, acid scavengers, processing aids, coupling agents, lubricants, blowing agents, polyhydric alcohols, nucleating agents, antistatic agents, light-stabilizers, process stabilizers, clarifiers, UV absorbers, slip agents, anti-fogging agents, anti-condensation agents, suspension stabilizers, anti-blocking agents, waxes, and mixtures of these substances. The concentration of said auxiliaries can vary between 0 to 20%, preferably 0.001 to 10%, more preferably 0.1 to 5%, by weight, relative to the total weight of the respective layer. These layers can optionally be combined with moisture barrier layers, strengthening layers and adhesive layers. Compositions typically used for adhesive layers include well-known anhydride functional polyolefins, e.g. Admer? types (Mitsui).

[0104] The multilayer packaging film of the present invention provides an improvement in oxygen transmission rate (cm.sup.3/m.sup.2*day) of at least 5%, preferably more than 20%, more preferably above 30% and even more preferably above 50%, compared to the same multilayer packaging film in the absence of the barrier properties, when the packaging article is exposed to r.h. above 65% and/or when the packaging article is exposed to temperature above 30? C.

[0105] The multilayer packaging film according to the invention can be a packaging material, preferably a container, a film or a sheet, especially for use in packaging of personal care, cosmetics, medical, pharmaceutical, household, industrial, food and beverage products where a high oxygen barrier is needed.

[0106] The packaging material can be flexible, rigid, semi-rigid or a combination thereof.

[0107] Rigid packaging articles typically have wall thicknesses in the range of 100 to 1000 micrometers. Typical flexible packages typically have thicknesses of 5 to 250 micrometers.

[0108] Specific articles containing the multilayer packaging film of the present invention include containers, films and sheets for packaging of food, beverages, cosmetics, pharmaceuticals, and personal care products where a high oxygen barrier is needed. Examples of beverage containers are: bottles for juices, sport drinks, or any other beverage where oxygen detrimentally affects the flavour, fragrance, performance (prevent vitamin degradation), or colour of the drink.

[0109] The articles of the present invention are also particularly useful as a sheet for thermoforming into rigid packages and films for flexible structures. Rigid packages include food trays and lids. Examples of food tray applications include dual ovenable food trays, or cold storage food trays, both in the base container and in the lidding (whether a thermoformed lid or a film), where the freshness of the food contents can decay with the ingress of oxygen.

[0110] The articles of the present invention also find use in the manufacture of cosmetic containers and containers for pharmaceuticals or medical devices.

[0111] Preferred articles of the present invention are rigid packaging articles, such as bottles and thermoformed sheets and flexible films.

[0112] More preferred articles of the present invention are hollow containers, which are expediently manufactured by any kind of blow moulding process known in the art.

[0113] Another subject of the invention is a method for the manufacture of the multilayer packaging film comprising the step of providing the polymers according to the layers (A), (B) and (C) and optionally (D), providing the additives (b) and (c) and comprising a mixing step and a shape forming process.

[0114] The shape forming process is dependent on the desired shape of the packaging article to be manufactured.

[0115] Containers are preferably made by blow moulding, injection moulding, injection and stretch blow moulding, extrusion blow moulding, compression moulding, compression and stretch blow moulding processes.

[0116] Films and sheets are preferably made by cast or blown film extrusion or co-extrusion processes, depending on the thickness required and on the number of layers needed to obtain specific properties, eventually followed by post-extrusion shaping processes like thermoforming, stretching or lamination. In the thermoforming process, the plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a final article. If vacuum is used, this process is generally called vacuum forming. In post-extrusion stretching processes an extruded film can be, for example, biaxially oriented by drawing. All the above listed processes are well-known in the art.

[0117] The additives (b) and (c) as well as the optional further customary additives (d) are expediently provided in the form of a masterbatch, in which the polymer is preferably the same as the polymer of the layer in which the respective additive is to be incorporated.

[0118] Masterbatches can be prepared by customary physical mixing processes.

[0119] A mixing apparatus for a liquid masterbatch can be a high speed dispersor (e.g. of Cowles? type), a media mill, a three-roll mill, a submill or a rotor-stator type dispersor.

[0120] A mixing apparatus used to make solid masterbatches MB can be a mixer, extruder, kneader, press, mill, calender, blender, injection moulding machine, injection and stretch blow moulding machine (ISBM), extrusion blow moulding machine (EBM), compression moulding machine, compression and stretch blow moulding machine; more preferably a mixer, extruder, injection moulding machine, injection and stretch blow moulding machine, compression moulding machine, compression and stretch blow moulding machine; even more preferably a mixer, extruder, injection and stretch blow moulding machine and extrusion blow moulding machine.

[0121] Extruders may be equipped with a metering system for introducing said additives and/or masterbatches into the main stream polymer. This metering may be carried out directly with one or more pure components or with one or more masterbatches.

[0122] The type of metering equipment used depends on the form in which the pure component or the masterbatch is metered.

[0123] In the case of solid component, a metering device of the feed screw type is usually employed and the point of introduction may be the main inlet of the extruder jointly with the feed of the main polymer granules, or in an unpressurized injection zone located along the extruder. For a solid masterbatch, the metering device may be a system comprising an additional extruder that pre-melts the masterbatch, pressurizes it and meters it by means of a metering pump, the amount of masterbatch metered being fed at a point along the main extruder advantageously without pressure.

[0124] For a liquid pure component or a liquid masterbatch, the metering device may be a system comprising one or more metering pumps which introduce the liquid masterbatch at the main inlet of the extruder jointly with the feed with the main polymer granules, without any pressure, or at a point under pressure located along the extruder.

[0125] Test Methods

[0126] The product properties are determined by the following methods, unless indicated otherwise:

[0127] Values of density are determined in accordance with ASTM D792 (g/cm.sup.3).

[0128] Values of melt flow rates (MFR) are determined in accordance with ASTM D1238 (g/10 min at specified temperature and weight)

[0129] Measurement method for oxygen scavenging performance

[0130] In Case of Films:

[0131] Five (5) grams of a cast film sample are cut in stripes of homogenous dimensions and placed inside of a glass two-necks 550 mL Schlenk. The Schlenk is sealed hermetically with a fitted cap made of gas-impermeable material on one of the two necks and with a Fit-Suba-Seal? septum of the other entrance. Measuring of the oxygen headspace is carried out by piercing the septum using the probe of a CheckMate? instrument and taking an aliquot of the atmosphere inside. Data are collected at regular time intervals. The oxygen concentration inside the Schlenk is then plotted against time. Between two measurements, the presence of an extra adhesive septum on top of the Fit-Sub-Aseal? septum ensures the lack of oxygen ingress through the pierced hole.

[0132] Measurement Method for Oxygen Transmission Rate Performance

[0133] In Case of Films:

[0134] All OTR measurements reported have been determined according to DIN 53380-3 and they were measured with an instrument specifically designed for high OTR films available from Fachlaboratorium f?r Permeationspr?fung, Wiesbaden, Germany.

[0135] The OTR cell wherein the samples are placed has two sides. On one side is the oxygen which permeates through the film sample to the other side where a nitrogen carrier gas is and which carries the permeated oxygen to the detector. Relative humidity can be fine-tuned on both sides of the film.

[0136] Haze Measurement:

[0137] Values of haze are determined on a 120 ?m film in accordance with ASTM D1003, Procedure A (% of transmitted light which, in passing through a specimen, deviates from the incident beam by forward scattering)

% Haze=(T.sub.diffuse/T.sub.total)*100

[0138] where T=% transmission.

[0139] Films were manufactured as described below and the haze of the films was measured with a hazemeter haze-gard dual (BYK Gardner). D65 illuminant was used with a CIE 1964 10? standard observer. The haze is defined as the percent of the CIE Y diffuse transmittance to the CIE Y total transmission.

EXAMPLES

[0140] All samples produced were 107 to 128 ?m five-layer cast films with a LDPE/tie/EVOH/tie/LDPE structure and respective thicknesses 50 ?m/6 ?m/5 to 7 ?m/6 ?m/50 ?m. This multilayer system corresponds to the three-layer system of FIG. 1, but with two additional adhesive layers (tie layers).

[0141] In all structures the low-density polyethylene used was LDPE Lupolene? 2420 (LyondellBasell) with a M.F.I. 4 g/10 min 190? C. 2.16 Kg; density 0.924 g/cm.sup.3 (ASTM D3236-88). The ethylene vinyl-alcohol copolymer (EVOH) used was EVAL? H171B with 38 mol % of ethylene content, a M.F.I. 1.7 g/10 min 190? C. 2.16 Kg; density 1.17 g/cm.sup.3 (ISO 1183). The tie resin used was Admer? AT1707 (Mitsui) with a M.F.I. 4.3 g/10 min 190? C. 2.16 Kg; density 0.91 g/cm.sup.3 (ASTM D1505).

[0142] % by weight mentioned in the following examples are based on the total weight of the mixture, composition or article; parts are parts by weight;

[0143] ex means example; cpex means comparative example; MB means masterbatch; CO means compound; unless indicated otherwise.

[0144] Substances Used

[0145] Component A1:

[0146] Low Density Polyethylene (LDPE) powder: LDPE Riblene?, M.F.I. 2 g/10 min 190? C. 2.16 Kg; density 0.925 g/cm.sup.3 (ASTM D3236-88).

[0147] Component b1:

[0148] Dercolyte? S125

##STR00001##

[0149] Component c1:

[0150] Cobalt stearate (9.5% Cobalt concentration)

[0151] Component c2:

[0152] Manganese stearate (8.5% Manganese concentration).

[0153] Masterbatches MB1 to MB3

[0154] The components were homogenized together on a Leistritz? ZSE18HP extruder at the temperature of 140? C. to obtain solid masterbatches MB1 to MB3; Table 1 gives the details.

TABLE-US-00001 TABLE 1 Components used Masterbatches [parts] (MB) A1 b1 c1 c2 MB1 60 30 MB2 97 3 MB3 94 6

Examples: ex1, ex2, and cpex1

[0155] Component A1 and the masterbatches MB1, MB2 and MB3 were mixed and homogenized in the ratios according to Table 2.

TABLE-US-00002 TABLE 2 Components used [parts] ex-cpex Compounds A1 MB1 MB2 MB3 cpex 1 CO1 (virgin LDPE) 100 ex1 CO2 90.5 6.5 3 ex2 CO3 90 6.5 3.5

[0156] The obtained compounds CO1 to CO3 were used to manufacture the above mentioned five-layer films (for ex1 and ex2 with a 50 ?m active oxygen-scavenging internal layer as in FIG. 1, left picture) on a cast film machine Dr. Collin? Extruder 20P. As an example of operational mode, components A1, MB1, MB2 or MB3 were inserted through one hopper applied to the main stream of a Dr. Collin? Extruder 20P (model 20P; 30 mm screw diameter 1:30 ratio) while internal barrel temperature was kept between 230 and 240? C.; EVOH, tie resin, and LDPE necessary for extruding the remaining layers of the multilayer films were added into separate hoppers each applied to the main stream of a Dr. Collin? Extruder 20P (model 20P; 30 mm screw diameter 1:30 ratio); the obtained co-extruded cast films were then winded from the unit and stored for the necessary testing.

[0157] Haze Measurement:

[0158] Total haze is the preferred method of measuring the clarity of POs articles, which can determine their suitability for packaging applications requiring high levels of transparency. Haze was measured on above prepared PO films obtained from compounds CO1 to CO3. Table 3 gives the details.

[0159] Composition CO2 and CO3 of the present invention clearly show a level of clarity very similar to virgin LDPE, as in CO1.

TABLE-US-00003 TABLE 3 Compounds Haze (%) CO1 1.5 CO2 1.9 CO3 1.8

[0160] Oxygen Barrier Performance:

[0161] The oxygen barrier performance corresponding to the films prepared above was measured by following the methods described above.

[0162] Table 4 shows the measured OTR (in cm.sup.3/m.sup.2*day*atm) for some of the above prepared multilayer films exposed to 50% and 100% r.h. in a nitrogen carrier gas (from now on carrier gas), respectively, where the active oxygen scavenger layer is an internal LDPE layer of 50 ?m thickness with compositions CO1 and CO3. It can clearly be seen that for each EVOH thickness the scavenger is able to compensate the EVOH loss of performance due to high r.h., maintaining values of OTR equivalent to the film without scavenger when exposed to low r.h.

TABLE-US-00004 TABLE 4 OTR OTR [cm.sup.3/m.sup.2 * day * atm] [cm.sup.3/m.sup.2 * day * atm] @ 50% r.h @100% r.h. (N.sub.2 carrier gas) (N.sub.2 carrier gas) Neutral Scavenger Neutral Scavenger EVOH Layer (CO1) (CO3) (CO1) (CO3) 6 ?m 6.1 2.44 16.5 6.9 7 ?m 4.7 1.75 14.6 4.9

[0163] Table 5 shows the measured OTR (in cm.sup.3/m.sup.2*day) of the above prepared multilayer films exposed at 23? C., 50? C. and 90? C. and 50% r.h., respectively, where the active oxygen scavenger layer is an internal LDPE layer of 50 ?m thickness with compositions CO1 and CO3.

TABLE-US-00005 TABLE 5 OTR @ 23? C. OTR @ 50? C. OTR @ 90? C. EVOH Neutral Scavenger Neutral Scavenger Neutral Scavenger Layer (CO1) (C03) (CO1) (C03) (CO1) (C03) 5 ?m 4.4 2.3 27.5 15.6 397 263

[0164] In Table 6, the depletion of an oxygen atmosphere by multilayer films containing compositions CO2 and CO3 is reported against the time elapsed (measured in days) from the moment the Schlenk where they are contained is hermetically sealed, leaving inside an air atmosphere (20.9% oxygen). Measurements of the oxygen concentration inside of the Schlenks are reported in 02%. The oxygen scavenging capacity per day in the same period is reported as mL 02/g Scavenger, according to the formula

mL O.sub.2/g Scavenger=(% O.sub.2 start?% O.sub.2 fin)*0.01*V.sub.flask free/(g active O.sub.2Scavenger)

[0165] For every composition the measurements have been interrupted when one of following conditions were met: end of the interesting period of desired shelf life (84 days), or oxygen content at nearly 0% (close to the lower accuracy limit of the measurement system).

TABLE-US-00006 TABLE 6 COMPOUNDS CO2 CO3 Time mL O.sub.2/g mL O.sub.2/g [days] % O.sub.2 Scavenger % O.sub.2 Scavenger 0 20.9 0 20.9 0 2 20.3 17.5 15.8 265.5 7 19.5 68.2 14.9 312.8 14 19.1 86.4 13.8 370.7 21 18.8 100.1 12.9 418.0 28 18.3 122.8 12.5 439.1 35 18.0 136.5 12.8 423.3 42 17.6 154.7 13.8 370.7 49 17.5 159.2 12.6 433.8 56 17.2 172.9 13.0 415.4 63 16.8 191.1 11.7 481.1 70 16.8 191.1 11.4 498.2 77 16.8 191.1 11.4 498.2 84 16.8 191.1 11.4 498.2