EA043619B1 - MULTILAYER STRUCTURE - Google Patents

Description

Field of technology

The invention relates to a multilayer structure. In particular, the present invention relates to a multilayer structure that provides an oxygen barrier and that can be recycled. In particular, the present invention relates to a recyclable polyethylene multilayer structure that provides an oxygen barrier. The present invention further relates to a method for producing a multilayer structure by lamination or extrusion coating.

Solvable problem.

It is known in the art of the present invention that copolymers of ethylene and vinyl alcohol, often referred to as EVOH, have good oxygen barrier properties.

US-A-2016/0060425 describes typical PE/EVOH structures in the comparative examples of Films 3.2 and 3.3. Films 3.2 and 3.3 have nine-layer structures (including adhesive layers). Such films have good barrier properties, but their subsequent technological processing, such as orientation, is problematic. For example, the EVOH layer may crack during orientation, thereby resulting in a loss of barrier properties.

It is also known to produce barrier films by lamination, for example, adhesive lamination. This method is described, for example, in pending patent application No. PCT/EP2016/080756. The adhesives used in these structures are generally not PE based. The structure additionally contains a metal or ceramic layer. This can cause problems during recycling.

Essence

As can be seen from one aspect, the present invention relates to a multilayer structure comprising (i) a layer of polyethylene film of a first outer layer, said layer of polyethylene film oriented in at least a longitudinal direction; (ii) a polyethylene layer of the second outer layer; (iii) an ethylene vinyl alcohol copolymer (EVOH) layer formed between the first outer layer and the second outer layer; and (iv) an adhesive layer on each side of the EVOH layer.

As can be seen from another aspect, the present invention relates to a method for producing a multilayer structure as described above, said method comprising the steps of: (i) providing a substrate, wherein the substrate is a polyethylene film that is oriented in at least a longitudinal direction; (II) coextruding onto the substrate (II-1) a layer of ethylene-vinyl alcohol copolymer; (II-2) layers of polyethylene; and (II-3) adhesive layers on both sides of the ethylene-vinyl alcohol copolymer layer, wherein the ethylene-vinyl alcohol copolymer layer is disposed between the substrate and the polyethylene layer, thereby obtaining a multilayer structure.

As can be seen from yet another aspect, the present invention relates to a method for producing a multilayer structure as described above, said method comprising the steps of: (a) providing a first polyethylene film, wherein the first polyethylene film is oriented in at least a longitudinal direction; (b) providing a second plastic film; (c) coextruding (c-1) an ethylene-vinyl alcohol copolymer layer between the first polyethylene film and the second polyethylene film; and (c-2) adhesive layers on both sides of the ethylene-vinyl alcohol copolymer layer; and (d) compressing the first polyethylene film and the second polyethylene film, thereby obtaining a multilayer structure.

Detailed description

General.

Additionally, polymers may also include polymer layers, and preferably contain additives such as antioxidants, process stabilizers, anti-blocking agents, lubricants, acid scavengers, pigments and the like.

Antioxidants and stabilizers are used to stabilize the polymer against oxidation. The group of antioxidants includes sterically hindered phenols (phenolic AO (alpha-olefins)); phosphites and phosphonites; sulfur-containing alpha-olefins; alkyl radical scavengers; aromatic amines; stabilizers containing hindered amines (mainly known as UV stabilizers), HAS; and combinations of two or more of the above substances.

Sterically hindered phenols are added to provide stability to the final product over its service life. This parameter is measured using an oven aging test, which is an accelerated test, and from this the service life at the expected temperature of use is calculated (the so-called Arrhenius plot). Additionally, phenols contribute to process stability. In some cases, only phenol is added as a stabilizer, but this is not common practice.

Phosphites and phosphonites provide protection during processing. They react with hydroperoxides to prevent depolymerization or a combination occurs. They are not very effective as such and are usually used in a mixture with phenolic AOs. This so-called synergistic mixture provides good stabilization during processing.

- 1 043619

Antiblocking agents and friction reducing agents can be used to improve film processability.

The friction reducing agents migrate to the surface and act as lubricants for the polymer and as a lubricant for the polymer against the metal shafts, resulting in a reduction in the coefficient of friction (CoF). Anti-blocking agents are added to provide a slight surface roughness to prevent the film from sticking to itself.

Both erucamide and olemide are used as friction reducing agents. Olemide may get to the surface faster due to the lower Mw, but once equilibrium is reached, erucamide generally provides a slightly greater friction-reducing effect at the same concentration.

Various mineral substances such as talc, natural and synthetic silicon are used as anti-blocking agents for the film.

Acid absorbers are used to deactivate acidic impurities. Most polyolefins contain low levels of chlorine due to catalyst residues (in the range of 10-20 ppm). Acid scavengers are added to protect process equipment from corrosion caused by hydrochloric acid. The main product used is Ca stearate.

Lubricants can be used for several purposes, such as improving product removal, preventing melt cracking, adding shine, providing internal lubrication, and the like. Additionally, acid scavengers can be added in excess to provide lubrication.

If a specific color is required, different pigments can be used. Pigments are well known in the art to which the present invention relates, and the pigment is selected based on the desired color. For example, titanium oxide can be used for white, carbon black for black, and ultramarine blue for blue. Pigments are usually added in the form of masterbatches.

The first layer of polyethylene.

The structure contains a layer of polyethylene film, where the polyethylene film is oriented at least in the longitudinal direction. In the description of the structure it is indicated as the first layer of polyethylene. In the context of extrusion coating, this layer is referred to as the substrate. In the context of the extrusion lamination process, this layer is referred to as the first polyethylene film.

The first layer of polyethylene, as described in the specification of the present patent application, is a film or layer of film that is substantially derived from polyethylene. As used herein, the term substantially polyethylene-derived means that the main raw materials of the film are ethylene homopolymers or copolymers, such as high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, ethylene-based plastomers, ethylene-based elastomers, low density polyethylene, mixtures and the like. Raw materials may contain small amounts of additives and other polymers. However, the amount of polymers other than ethylene homo- and copolymers is generally no more than 10, preferably no more than 5, and substantially preferably no more than 2% by weight, such as no more than 1% by weight. Additionally, the first layer of polyethylene may be a multilayer film containing more than one layer. However, when the first layer of polyethylene contains multiple layers, the entire structure is preferably substantially polyethylene-derived.

Therefore, the first layer of polyethylene is a layer of film that is oriented at least in the longitudinal direction, optionally also in the transverse direction. Preferably, the film layer is oriented only in the longitudinal direction.

The first layer of the polyethylene structure of the present invention contains at least one layer A.

Layer A.

Layer A is based on a polyethylene polymer with a density of 890 to 980 kg/m ³ .

The polyethylene may be a homopolymer or may be a copolymer. Since polyethylene can have a density from 890 to 980 kg/m ³ , it can be, for example, high-density polyethylene (HDPE), medium-density polyethylene (MDPE) or linear low-density polyethylene (LLDPE), or mixtures with high-density low-density polyethylene (LDPE), or with ethylene-based plastomer, or a mixture of ethylene-based plastomer with low-density high-density polyethylene (LDPE).

Preferred polyethylenes for use in producing layer A of the first polyethylene layer are LLDPE.

The MFR ₂ (190°C, 2.16 kg, ISO 1133) of a suitable LLDPE is in the range of 0.01 to 20 g/10 min, preferably in the range of 0.05 to 10 g/10 min, more preferably in the range of 0.1 to 6.0 g/10 min and even more preferably in the range of 0.1 to 5.0 g/10 min.

The LLDPE of layer A of the first polyethylene layer may have a density ranging from 910 to 950, preferably 920 to 945, such as from 930 to 940 kg/m ³ .

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The weight average molecular weight Mw of LLDPE is preferably in the range from 100,000 to 200,000 g/mol.

Mw/Mn LLDPE can vary within fairly wide limits. Preferred Metrics

Mw/Mn is 3 or more, such as 6 or more, preferably 10 or more. Limits are provided from 3.5 to 30.

LLDPE contains at least one or two comonomer(s). Suitable comonomers are C ₃ -C ₁₀ alpha-olefin comonomers. Therefore, LLDPE may be a copolymer of ethylene and one C ₃ -C ₁₀ alpha-olefin comonomer or a terpolymer of ethylene and two different C ₃ C ₁₀ alpha-olefin comonomers.

Preferably, the comonomers are selected from the group of 1-butene, 1-hexene and 1-octene. Preferably the comonomer used is 1-butene and/or 1-hexene. Preferred terpolymers include comonomers of 1-butene and 1-hexene.

The total comonomer content of the overall polymer is 0.3 to 7.0, preferably 0.6 to 4.5, more preferably 1.0 to 3.5, and most preferably 1.2 to 2.3 mole percent.

In the case where the LLDPE is a terpolymer of ethylene and two different C ₃ -C ₁₀ alpha-olefin comonomers, preferably 1-butene and 1-hexene, 1-butene is present in an amount of from 0.1 to 3.0, preferably from 0.2 to 2.0, more preferably from 0.3 to 1.5 and most preferably from 0.4 to 0.8% by mole, and hexene is present in an amount from 0.2 to 4.0, preferably from 0.4 to 2.5, more preferably from 0.7 to 2.0 and most preferably from 0.8 to 1.5% by mole.

LLDPE may be unimodal or multimodal, preferably multimodal. Unimodal LLDPE has a single peak in the gel permeation chromatography spectrum because it is produced using a one-step process. Most preferably, when the LLDPE is multimodal, the LLDPE is derived from a homopolymer component and a copolymer component. These polymers are well known in the art and are available from Borealis and others, such as films under the trade name Borshape™ and Borstar™. It is well known that films produced from LLDPE and oriented in the longitudinal direction have good tear strength not only in the transverse direction, but also in the longitudinal direction.

Preferably, such multimodal, such as bimodal LLDPEs, are prepared using multi-stage polymerization using the same catalyst. Therefore, two slurry reactors or two gas phase reactors can be used. Preferably, however, such multimodal, such as bimodal LLDPEs, are prepared using slurry polymerization in a loop reactor followed by gas phase polymerization in a gas phase reactor.

LLDPE suitable for the present invention can be produced using a Ziegler-Natta catalyst or a single site metal polymerization catalyst (mLLDPE), but is preferably prepared using a Ziegler-Natta catalyst. Such catalysts are well known in the art to which the present invention relates.

Suitable films, LLDPE polymers for the production of such films and their preparation are described, inter alia, in WO-A-2004/000933, EP-A-1378528, WO-A-2004/011517, EP-A-2067799 and WO-A-2007 /003322,

Suitable HDPE has a density ranging from 940 to 980, preferably from about 945 to about 965 kg/m ³ . More preferably, the density is in the range of about 950 to about 965 kg/m ³ .

Preferably the HDPE is unimodal HDPE.

HDPEs used in the present invention may be homopolymers or copolymers with at least one alpha-olefin of 3 to 10 carbon atoms.

The melt flow rate (MFR) of the HDPE polymer used for Layer B of the present invention is not critical and may vary depending on the mechanical properties desired for the end application.

In one preferred embodiment of the present invention, the MFR ₂ is in the range of 0.05 to 10 g/10 min, preferably 0.1 to 7.0 g/10 min, more preferably 0.2 to 5.0 g/10 min. 10 min, more preferably 0.3 to 3.0 g/10 min, even more preferably 0.4 to 2.0 g/10 min, and most preferably 0.5 to 1.3 g/10 min.

The molecular weight distribution (MWD), expressed as Mw/Mn, of the HDPE polymer used in the present invention may vary widely. The MWD is preferably in the range of 2 to 20, preferably 2.5 to 15, more preferably 3 to 10, and most preferably 3.5 to 7.

The HDPE polymer used in the present invention may be a known and, for example, commercially available polyethylene polymer, or the HDPE polymer may be prepared using any complex catalyst, typically Ziegler-Natta catalysts, Cr catalyst along with single site metal catalysts (SSC) in

- 3 043619 well-documented polymerization processes.

Suitable films, HDPE polymers for producing such films and their preparation are described, inter alia, in WO-A-1999/058584, WO-A-1999/051649, WO-A-2007/104513 and WO-A-2007/065644.

Layer A of the first polyethylene layer may, of course, contain a mixture of various components, such as a combination of (high pressure) low density polyethylene (LDPE) produced in a tubular or autoclave reactor and LLDPE or a combination of unimodal and bimodal LLDPE polymers or a mixture of (high pressure) LDPE produced in a tubular or autoclave reactor as above, and/or LLDPE and ethylene-based plastomer with a density below 915 kg/m ³ .

Suitable plastomers used in layer A of the first polyethylene layer are ethylene-based plastomers with a density below 915 kg/m ³ . An ethylene-based plastomer is a copolymer of ethylene and propylene or a C ₄ -C ₁₀ alpha-olefin. Suitable C ₄ -C ₁₀ alpha-olefin includes 1-butene, 1-hexene and 1-octene, preferably 1-butene or 1-octene and more preferably 1-octene. Preferably, copolymers of ethylene and 1-octene are used.

Suitable ethylene-based plastomers have a density in the range of 860 to 915, preferably in the range of 870 to 910 kg/m ³ .

The MFR ₂ (ISO 1133; 190°C; 2.16 kg) of a suitable ethylene-based plastomer is in the range of 0.01 to 20 g/10 min, preferably in the range of 0.05 to 10 g/10 min, more preferably in the range from 0.1 to 6.0 g/10 min and even more preferably in the range from 0.1 to 5.0 g/10 min.

The melting point (measured using DSC according to ISO 11357-3:1999) of a suitable ethylene-based plastomer is below 130, preferably below 120, more preferably below 110 and most preferably below 100°C. Additionally, a suitable ethylene-based plastomer has a glass transition temperature Tg (measured using DMTA according to ISO 6721-7) below -25, preferably below -30, more preferably below -35°C.

In the case of a copolymer, the copolymer is a copolymer of ethylene and propylene and has an ethylene content of 10 to 55, preferably 15 to 50, and more preferably 18 to 48 wt%. In the case of a copolymer, the copolymer is a copolymer of ethylene and a C ₄ -C ₁₀ alpha-olefin, and has an ethylene content of 60 to 95, preferably 65 to 90, and more preferably 70 to 88 wt%.

The molecular weight distribution Mw/Mn of a suitable ethylene-based plastomer is overwhelmingly below 4, such as 3.8 or below but at least 1.7. Preferably it is from 1.8 to 3.5.

A suitable ethylene-based plastomer may be any copolymer of ethylene and propylene or ethylene and a C ₄ -C ₁₀ alpha-olefin with the above properties, which are commercially available, for example, from Borealis under the trade name Queo, from Dow Chemical Corp (USA) under the trade name Queo, under the Engage or Affinity brand, or from Mitsui under the Taimen brand

Alternatively, these ethylene-based plastomers can be prepared using known processes, one or two step polymerization processes, including solution polymerization, suspension polymerization, gas phase polymerization, or combinations thereof, in the presence of suitable catalysts, such as vanadium oxide catalysts or catalysts with single site of polymerization on the metal, for example, metallocene catalysts or catalysts with constrained geometry, known to one skilled in the art to which the present invention relates.

Preferably, these ethylene-based plastomers are produced using a one or two step solution polymerization process, preferably using a high temperature solution polymerization process at a temperature higher than 100°C. Such a process is essentially based on the polymerization of a monomer and a suitable comonomer in a liquid carbon solvent in which the resulting polymer is dissolved. Polymerization is carried out at a temperature above the melting point of the polymer, resulting in a polymer solution. This solution is evaporated to separate the polymer from the unreacted monomer and solvent. The solvent is then recovered and recycled back into the process.

Preferably, the solution polymerization process is a high temperature solution polymerization process using a polymerization temperature higher than 100°C. Preferably, the polymerization temperature is at least 110, more preferably at least 150°C. The polymerization temperature can be up to 250°C.

The pressure in such a solution polymerization process is preferably in the range of 10 to 100, preferably 15 to 100, and more preferably 20 to 100 bar.

The liquid hydrocarbon solvent used is preferably a C5 ₁₂ hydrocarbon, which may be an unsubstituted or substituted when using a C1.4 alkyl group, such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane and hydrogenated gasoline. More preferably, unsubstituted C ₆ - ₁₀ hydrocarbon solvents are used. Such processes are described, inter alia, in WO-A-1997/036942, WO-A-2006/083515, WO-A2008/082511, and WO-A-2009/080710,

The layer A polyethylene may also contain antioxidants, process stabilizers, friction reducing agents, pigments, UV stabilizers and other additives known in the art to which the present invention relates.

Layer B.

The first layer of the polyethylene structure of the present invention optionally contains at least one additional layer, representing layer B.

Layer B can be made from high density polyethylene (HDPE) with a density from 940 to 970 kg/m ³ or medium density polyethylene (MDPE) with a density from 925 to 940 kg/m ³ or linear low density polyethylene (LLDPE) with a density from 910 to 950 kg/m ³ or mixtures thereof or when using plastomers.

Suitable MDPE preferably has a density ranging from about 930 to about 940 kg/m ³ . A preferred MDPE is a copolymer that contains from about 85 to about 98 wt.% ethylene units and from about 2 to about 15 wt.% C ₃ -C ₁₀ alphaolefin units. Suitable C ₃ -C ₁₀ alpha-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl1-pentene and 1-octene, and the like, and mixtures thereof. Preferably, MDPE has a bimodal or multimodal molecular weight distribution. A method for producing bimodal or multimodal MDPE is known, for example, from WO-A-1999/041310 and WO-A-2008/089979.

Suitable HDPEs are those already described for layer A.

Suitable LLDPEs are those already described for layer A.

The MDPE or HDPE or LLDPE layer B may also contain minor amounts of conventional additives such as antioxidants, UV stabilizers, acid scavengers, nucleating agents, anti-blocking agents, friction reducing agents and the like, along with polymeric processing agents (PPAs). Additives may be added as individual components or as part of a masterbatch, as is known in the art to which the present invention relates.

The structure of the first layer of polyethylene.

The film forming the first layer of polyethylene may be a single-layer film, therefore it consists only of layer A.

The film forming the first layer of polyethylene may also be a multilayer film. Multilayer films are preferably formed of at least two layers, ideally at least three layers, such as 3 layers, 5 layers or 7 layers. Such films preferably contain at least adjacent layers A and B, preferably A, B and E. In the case of the film forming the first layer of polyethylene, it is a multilayer film, the film containing at least a layer A and a layer B, optionally in combination with a layer E.

In the case where the multilayer film contains a layer E, this layer can be made from high density polyethylene (HDPE) with a density of 940 to 970 kg/m ³ or from medium density polyethylene (MDPE) with a density of 925 to 940 kg/m ³ or linear low density polyethylene (LLDPE) with a density from 910 to 950 kg/m ³ as specified for layer B, or mixtures thereof or when using plastomers.

Layer E may be the same layer as layer B, or may be different from layer B.

Layer E may also contain minor amounts of conventional additives such as antioxidants, UV stabilizers, acid scavengers, nucleating agents, anti-blocking agents, friction reducing agents and the like, along with polymeric processing agents (PPAs). Additives may be added as individual components or as part of a masterbatch, as is known in the art to which the present invention relates.

This film has an E/A/B structure and is not blocked.

The film thickness distribution (%)E/A/B of the film layer is preferably 10 to 40%/20 to 80%/10 to 40%, preferably 12 to 30%/40 to 76%/12 to 30% of the total thickness films (100%).

The film forming the first layer of the polyethylene of the present invention may also have 5 or 7 layers, and additional layers may be made from any polyethylene.

In this case, in one preferred embodiment of the present invention, a film with a blocked structure is used as the first layer of polyethylene.

In this case, the first layer of polyethylene has the structure E/A/BL/BL/A/B or E/A/A/A/BL/BL/A/A/A/B, where BL represents the blocking layer, and layers A, B and E are as above, and layer E is identical to layer B.

For E/A/BL/BL/A/B film structure, the layer thickness can correspond to 7.5-27.5%/15-35%/525%/15-35%/7.5-27.5%, where the total film thickness represents 100%, and the amount of blocking layer represents the sum of two layers (BL).

The blocking layer (BL) in this case consists of a mixture of LLDPE, as above for layer A, and plastomer, as above; or from a mixture of LDPE, as above, and an ethylene-based plastomer with a density below 915 kg/m ³ , as above.

The plastomer is preferably present in the mixtures in an amount of 20 to 80, more preferably in an amount of 40 to 75, and even more preferably in an amount of 50 to 70 weight percent. Basically

- 5 043619 a mixture of any ratio is suitable, provided that the mixture fulfills its function as a blocking layer.

It is also possible to use 100 wt.% plastomer for the blocking layer or any other PE-based material known in the art as suitable for the blocking layers, such as EVA, EVA, mPE, and the like.

Receiving film.

Any mixture used in the above layers can be prepared using any suitable melt mixing process at temperatures above the melting point of the respective mixture. Typical devices for performing said melt mixing are dual screw extruders, single screw extruders, optionally combination static mixers, mixing chambers such as Farrel type mixers, Banbury type mixers and reciprocating mixers such as Buss mixers. Preferably, the melt mixing process is carried out in a twin screw extruder with high intensity mixing elements and preferably at a temperature of from 170 to 270°C, more preferably from 180 to 250°C.

It is also possible to produce a mixture of LLDPE or LDPE and plastomer by using dry mixing in a suitable mixing device such as a horizontal or vertical stirrer, rotating tanks and Turbula mixers, provided sufficient homogeneity is achieved.

The three-layer film of the present invention can be produced using any conventional film extrusion process known in the art, such as blown film extrusion. Preferably, the three-layer film is produced using a blown film extrusion process, more preferably using processes that are generally known and available to one skilled in the art to which the present invention relates.

Typical processes for producing the three-layer film of the present invention are extrusion processes using an annular nozzle die. The bubble formed by blowing air flow inside the sleeve formed by the film cools the film. After curing, the bubble is destroyed between the rollers. The film can then be longitudinally separated, cut or subjected to post-processing such as using a newspaper head if required. For these purposes, traditional film production technologies can be used. Typically, layer A and layers B and C are coextruded at temperatures ranging from 160 to 240°C and cooled by blowing gas (usually air) at a temperature of 5 to 50°C, to provide a frost line (cloud line) height 1 or 2 to 8 times the diameter of the mouthpiece. The inflation ratio may range from 1 (1:1) to 4 (1:4), preferably from 1.5 (1:1.5) to 3.5 (1:3.5), more preferably from 2 ( 1:2) to 3 (1:3).

The steps of the film production process of the present invention are known and can be carried out using a single-layer film production line in a manner known in the art to which the present invention relates. Such film production lines are commercially available, for example from Windmoller & Holscher, Reifenhauser, Hosokawa Alpine, and the like.

Typically, a three-layer film (E/A/B) is produced using a 3-layer coextrusion line, but in some embodiments of the present invention a coextruder may be used that is a 5- or 7-layer coextrusion line.

With this configuration, the central dies can all extrude a layer of material A to obtain a film of type E/A/A/A/B or E/A/A/A/A/A/B or each of the two, respectively, the three outer dies can extrude a layer material of the outer layer to obtain a film of type E/E/A/B/B or E/E/E/A/B/B/B, or as a combination of the previously described possibilities, a film of type E/E/A/A can also be obtained /A/B/B. Since all these outer (B and E layers), respectively, A-layers are identical, the resulting films are actually E/A/B films.

Such 5-layer or 7-layer coextrusion lines can also be used to produce the following structures:

A/A/A/A/A or A/A/A/A/A/A/A, which are all also monolayer films since the A-layers are identical.

A/B/B/B/A or A/A/B/A/A or A/A/B/B/B/A/A and the like, which are all also two-layer films.

In the case where the first layer of polyethylene contains additional layers to layer A, B and E, such layer F and/or layer G of the film structure can represent E/F/A/G/B and any combinations thereof that can be obtained using lines for 5-layer or 7-layer coextrusion.

Film with blocked structure.

For the blocked film, a B (or E)/A/BL type structure is used, where B (or E) represents one of the outer layers (E or B are identical in the blocked structure), A represents the inner layer, and the BL layer represents the blocking layer. As the three-layer coextruded film comes out of the die in the shape of a bubble, the bubble is cut and then the two halves are joined

- 6 043619 together to effectively form a structure of type B/A/BL/BL/A/B (that is, the bubble formed is collapsed, for example, when using pressure rollers to obtain a film). In this way, the film thickness is actually doubled and the desired initial film thickness is obtained. In the field of technology to which the present invention relates, this is called film blocking.

Therefore, B/A/BL/BL/A/B film is produced from two identical B (or E)/A/BL films laminated together through (BL) layers.

For B/A/A/A/BL/BL/A/A/A/B films, two identical B/A/A/A/BL films are produced using a 5-layer coextrusion line and the resulting bubble is collapsed to obtain corresponding film with a blocked structure.

Additionally, it is also possible to use other combinations of layers A, B, E and/or F or G with the blocking layer BL to obtain a film forming a first layer of polyethylene as a film with a blocked structure.

The film of the present invention, forming the first layer of polyethylene, is oriented at least in the longitudinal direction.

The resulting monolayer or multilayer films are subjected to a stretching step where the film is stretched in the longitudinal direction (MDO). The traction can be carried out using any conventional technology using any conventional traction devices that are well known to one skilled in the art to which the present invention relates.

The MDO process can be carried out on a single line where the MDO device is directly connected to the blown film machine, that is, the film exiting the blown film line is immediately transferred to the MDO machine.

The MDO process can also be carried out off-line, where the device for MDO represents a stand-alone device. In this case, the film leaving the blown film line is first wound on a winder (winder) and then enters an off-line MDO where the film is unwinded on an unwinder (unwinder) before being stretched.

In the case where blocking film structures are used, preferably the MDO process is carried out in one line.

During MDO, the film produced by the blown film line is heated to orientation temperature. Preferably, the orientation temperature limits may be 25°C below the VICAT temperature of the layer A (outer) film material down to the melting temperature of the (outer) layer of the film material. Heating is preferably carried out using multi-row heating rollers.

Next, the heated film is fed to a slow draw roll with a pressure roll, which has a rotation speed identical to that of the heating rolls. Next, the film is fed to a fast drawing shaft. The fast draw roller has a speed that is 2 to 10 times faster than the slow draw roller, allowing for efficient continuous film orientation.

The oriented film is then fed to thermal annealing rolls, which allows for stress relaxation by holding the film at an elevated temperature for a certain period of time.

The annealing temperature is preferably within the same range as that used for drawing or slightly lower (eg 10 to 20° C. lower), the lower limit being room temperature. Finally, the film is cooled using chill rollers to room temperature.

The ratio of film thickness before and after orientation is called the stretch ratio or stretch ratio. The degree of stretch varies depending on many factors, including the desired film thickness, film properties, and the structure of the multilayer film.

The process for producing a monoaxial MD (longitudinal direction) monolayer or multilayer film used in the present invention includes at least the stages of forming a monolayer or multilayer film and stretching the monolayer or multilayer film in the longitudinal direction with a stretch ratio from 1:1.5 to 1: 12, preferably in the range of 1:2.0 to 1:10, more preferably in the range of 1:3.0 to 1:8.

The film is stretched from 1.5 to 12 times longer than the original length in the longitudinal direction. In the specification of this patent application this is stated as a stretch ratio of 1:1.5 to 1:12, i.e. 1 represents the original length of the film and 1.5 or 12 means it was stretched to 1.5 or 12 times that length. original length.

The effect of stretching (or stretching) is a similar reduction in film thickness. Therefore, a stretch ratio of 1:1.5 or 1:12 generally also means that the resulting film thickness is between 1/1.5 and 1/12 of the original thickness.

After orientation, the film forming the first layer of polyethylene has a thickness of from 5 to 100, preferably from 10 to 80 and more preferably from 10 to 40 μm. This means that, for example, when

- 7 043619 stretch ratio 1:3 for a film yield of 40 μΜ it is necessary that the initial film has a thickness of 120 cm, and with a stretch ratio of 1:12 for a film yield of 40 μm it is necessary that the initial film have a thickness of 480 μm.

The film forming the first layer of polyethylene (i.e. MDO film) is preferably characterized by the following properties:

i) a tensile modulus (according to ISO 527-3) in the longitudinal direction, measured at room temperature, of at least 800, more preferably at least 1000, even more preferably at least 1200 and most preferably at least 1500 MPa;

ii) a tensile modulus (according to ISO 527-1 and 527-3) in the longitudinal direction, measured at 70°C, of at least 100, more preferably at least 110, even more preferably at least 120 and most preferably at at least 150 MPa;

iii) the ratio of i) to ii) is not more than 10.

The first layer of polyethylene may not be glossy if there are no such requirements for the film, but if the final film is required to be glossy, then the first layer of polyethylene preferably has:

iv) gloss (20°) according to ASTM D2457 of at least 30, more preferably at least 40, even more preferably at least 50 and most preferably at least 60%.

If the haze of the first layer of polyethylene is not important for a given application, then the haze can also be up to 100%, but if the haze must be low or relatively low for a given application, then the first layer of polyethylene preferably has:

v) ASTM D1003 turbidity below 30, more preferably below 25, even more preferably below 20 and most preferably below 15%.

If desired, the first layer of polyethylene can also be biaxially oriented, therefore oriented in the longitudinal direction as well as oriented in the transverse direction (TD). Suitable stretch ratios are from 1:4 to 1:13, preferably in the range from 1:5.0 to 1:10, more preferably in the range from 1:5.5 to 1:8.

If the first layer of polyethylene is a biaxially oriented film, then the film thickness before orientation is greater than if only the orientation device is used to achieve a given final film thickness after orientation. This knowledge is within the competence of a person skilled in the field of technology to which the present invention relates.

Preferably, the first layer of polyethylene is oriented only in the longitudinal direction.

Second layer of polyethylene.

The structure contains another layer of polyethylene film. In the description of the structure it is indicated as the second layer of polyethylene. In the context of extrusion coating, this layer is referred to as a polyethylene layer. In the context of the extrusion lamination process, this layer is referred to as a second polyethylene film.

The second layer of polyethylene, as described in the specification of the present patent application, is a film or layer of film that is substantially derived from polyethylene. As used herein, the term substantially polyethylene-derived means that the base raw materials of the film are homopolymers or copolymers of ethylene, as described above for the first layer of polyethylene. Additionally, the second layer of polyethylene may be a multilayer film containing more than one layer. However, when the second polyethylene layer comprises multiple layers, the entire structure is preferably substantially polyethylene-derived.

Extruded coating structure.

If the structure is produced by extrusion coating, the second layer of polyethylene contains and preferably essentially consists of low density polyethylene. As used herein, the term essentially consists of means that the second layer of polyethylene may contain minor amounts of additives known in the art to which the present invention relates, such as antioxidants, and other polymers, provided that such other polymers do not adversely affect negative impact on the technological properties of low-density polyethylene. Typically, the amount of additives and other polymers in such a case is no more than 2, preferably no more than 1, and substantially preferably no more than 0.5% by weight. In any case, if the structure is produced by extrusion coating, the second layer of polyethylene typically contains at least 40, preferably at least 50, more preferably at least 75, and substantially preferably at least 90% low density polyethylene.

Low density polyethylene typically has a melt flow rate MFR ₂ (measured under a 2.16 kg load at 190°C) from 1 to 15 g/10 min, preferably from 2 to 10 g/10 min and even more preferably from 3 to 8 g/10 min. Additionally, it typically has a density of 915 to 930, preferably 916 to 926, and even more preferably 917 to 925 kg/m ³ . Low density polyethylene can be produced using an autoclave reactor process as described in EP-A-1777238, or using a tubular reactor process as described in WO-A2013/132009, WO-A-2013/083285, WO-A-2013178241 and WO-A-2013/178242. It may also be a mixture of two low density polyethylenes, one obtained using an autoclave reactor process, one obtained using a tubular reactor process. Preferably the low density polyethylene is produced using a tubular reactor process.

Extrusion lamination structure.

If the structure is obtained using extrusion lamination, the second layer of polyethylene is preferably a film made from polyethylene. Such film may be a cast film or a blown film, and is preferably a blown film.

The film forming the second layer of polyethylene in extrusion lamination can be produced using cast or blown film techniques well known in the art to which the present invention relates. Preferably the film has a thickness of 10 to 200, preferably 10 to 150, such as 20 to 120 μm.

When the structure is produced using extrusion lamination, the second layer of polyethylene may comprise any suitable polyethylene, such as high density polyethylene, medium density polyethylene, linear low density polyethylene, ethylene based plastomers, ethylene based elastomers, low density polyethylene, the like. Raw materials may contain small amounts of additives and other polymers. However, the amount of polymers differs from ethylene homo- and copolymers and is generally no more than 10, preferably no more than 5, and substantially preferably no more than 2% by weight, such as no more than 1% by weight. Additionally, the second polyethylene layer may be a multilayer film comprising more than one layer. However, when the second layer of polyethylene contains multiple layers, the entire structure generally forming the second layer of polyethylene must in any case be substantially derived from polyethylene.

When the structure is obtained using extrusion lamination, the film forming the second layer of polyethylene can be any non-oriented film, or the film can be at least oriented in the longitudinal direction (MDO) and optionally also in the transverse direction (TD). Preferably, the film forming the second layer of polyethylene is a non-oriented film or MDO film. More preferably, the film forming the second layer of polyethylene is non-oriented.

The film forming the second polyethylene layer of the extrusion lamination structure of the present invention has a final thickness of 10 to 200, preferably 10 to 150, preferably 20 to 120 μm.

The film forming the second layer of polyethylene in the extrusion lamination structure preferably has at least a polyethylene-based seal layer C with a density of from 890 to 950 kg/m ³ .

The polyethylene may be a homopolymer produced by a low or high pressure process (LDPE) or may be a copolymer. Since polyethylene can have a density from 890 to 950 kg/m ³ , it can be medium density polyethylene (MDPE) or linear low density polyethylene (LLDPE), as described for layer A above, and any combination thereof.

Preferably, the seal layer C comprises a mixture of linear low density polyethylene (LLDPE) produced using either a Ziegler-Natta catalyst (znLLDPE) or a metallocene catalyst (mLLDPE) or an ethylene based plastomer with low density polyethylene (LDPE).

Suitable znLLDPEs are those described for layer A above.

As described in the specification of this patent application, the mLLDPE polymer is an ethylene copolymer with a density of 940 kg/m ³ or less. Preferred mLLDPE may have a density of from 905 to 940, more preferably from 910 to 937 kg/m ³ . In one preferred embodiment of the present invention, even densities from 915 to 925 kg/m ³ are possible.

mLLDPE is prepared from ethylene with at least one C ₃ -C 2 ₀ alpha-olefin comonomer, preferably a C ₃ -C ₁ 2-alpha olefin comonomer, for example 1-butene, 1-hexene or 1-octene. Preferably mLLDPE is a binary copolymer, that is, the polymer contains ethylene and one comonomer, or terpolymer, that is, the polymer contains ethylene and two or three, preferably two comonomers. Preferably mLLDPE contains an ethylene-hexene copolymer, an ethylene-octene copolymer, an ethylene-butene copolymer, or an ethylene terpolymer with 1-butene and 1-hexene comonomers. The amount of comonomer present in mLLDPE is preferably 0.5 to 12, more preferably 2 to 10, and most preferably 4 to 8 mol%. Alternatively, the comonomer content present in mLLDPE may be from 1.5 to 10%, preferably from 2 to 8% by weight.

- 9 043619

MFR2 mLLDPE is preferably 0.01 to 20 g/10 min, more preferably 0.2 to g/10 min, even more preferably 0.3 to 6.0 g/10 min, and most preferably 0.4 to 5.0 g/10 min.

mLLDPE can be unimodal or multimodal, both are preferred. As used herein, the term unimodal means that the molecular weight profile of the polymer includes a single peak and is obtained using a single reactor and a single catalyst.

Unimodal mLLDPE polymers preferably have a narrow molecular weight distribution. The Mw/Mn is preferably 2 to 4, more preferably 2 to 3.

Multimodal can be understood as bimodal MWD or bimodal comonomer distribution (eg, the MFR of the components is identical, but they may contain identical comonomers in different amounts). Bimodal mLLDPE contains an LMW component and an HMW component. Both the LMW and HMW components of the multimodal mLLDPE are preferably ethylene copolymers as stated above.

The molecular weight distribution, Mw/Mn, of the multimodal mLLDPE can be below 30, preferably in the range of 2-5.

Suitable mLLDPEs are commercially available from ExxonMobil Chemical, Nova, Dow, LyondellBasell, and are provided by way of example.

Alternatively, suitable mLLDPE polymers can be prepared using a known method according to or similar to conventional polymerization processes, including solution, suspension and gas phase polymerization, as described in the literature on polymer chemistry. Examples are given in WO-A-2006/066952, WO-A-2002/002323, WO-A-2005/002744 and WO-A2003/066699.

Unimodal mLLDPE, as indicated above, is preferably produced using a one-step polymerization, for example, solution polymerization, slurry or gas phase, preferably suspension polymerization in a slurry tank or more preferably in a loop reactor in a manner known in the art to which the present invention relates. By way of example, said unimodal mLLDPE may be prepared, for example, by using a one-step loop reactor polymerization process according to the principles set forth below for polymerizing a low molecular weight fraction in a loop reactor using a multi-step process, of course, except that the process conditions (e.g. , hydrogen and comonomer supply) are adjusted to ensure the properties of the final unimodal polymer.

Multimodal (eg, bimodal) mLLDPE, as described above, can be prepared by using mechanical mixing of two or more separately prepared polymer components, or preferably, by using in situ mixing in a multi-stage polymerization process during the process of preparing the polymer components. Both mechanical and in situ mixing are well known in the art to which the present invention relates.

Accordingly, preferred multimodal mLLDPE polymers are prepared using in-situ mixing in a multi-stage process, that is, two or more stages of the polymerization process, including solution, slurry and gas phase polymerization, in any order. Alternatively, said multimodal mLLDPE can be produced by using two or more different polymerization catalysts, including multisite or dual site catalysts, in a one-step polymerization process.

Preferably, the multimodal mLLDPE as described above is produced by at least two-stage polymerization using the same catalyst, for example a single site metal catalyst. Therefore, for example, two slurry reactors or two gas phase reactors, or any combination thereof, in any order, can be used.

mLLDPE, as stated above, can be prepared using any conventional metal single site catalyst (SSC), such SSC catalysts include metallocenes.

All of these catalysts are well known in the art to which the present invention relates. In the case of mLLDPE, the use of metallocene catalysts is preferred. The preparation of the metallocene catalyst can be carried out according to or similar to methods known in the literature and is within the competence of one skilled in the art to which the present invention relates. Therefore, for obtaining, see for example EP-A-129368, WO-A-1998/056831, WO-A-2000/034341, EP-A-260130, WO-A-1997/028170, WO-A-1998 /046616, WO-A-1998/049208, WO-A1999/012981, WO-A-1999/019335, WO-A-1998/056831, WO-A-2000/034341, EP-A-423101 and EP-A -537130, WO 2005/002744, which describes a preferred catalyst and process for producing said mLLDPE component.

Instead of znLLDPE or mLLDPE, a plastomer can be used for the first film, as described above.

- 10 043619

As used herein, the term LDPE means a low density ethylene homopolymer produced by a high pressure polymerization process (autoclave or tubular reactor polymerization process).

Such LDPEs are well known in the art and they typically contain long chain branches that distinguish LDPEs from linear low density polyethylenes LLDPEs.

The LDPE used in the sealing layer of the present invention is not limited in principle.

Typically, LDPE may have an MFR2 (190°C, 2.16 kg; ISO 1133) of at least 0.05 g/10 min, preferably in the range of 0.1-20 g/10 min, more preferably 0.3- 10 g/10 min, even more preferably 0.4-5 g/10 min. In one embodiment of the present invention, LDPE with an MFR2 of 0.2 to 1.0 g/10 min is preferred.

The density (ISO 1183) of LDPE is typically 905 to 940, preferably 910 to 935 kg/m ³ , for example 915 to 930 kg/m ³ .

The Tm (DSC, ISO 11357-3) of LDPE is preferably 70-180°C, more preferably 90-140°C, for example about 110-120°C.

LDPEs suitable for the second film structure are any conventional LDPEs, for example, commercially known LDPEs, or they can be prepared by any conventional high pressure (HP) polymerization process in a tubular or autoclave reactor using free radical generation. Such high pressure polymerization processes are very well known in the field of polymer chemistry and are described in the literature, see for example Vieweg, Schely and Schwarz: Kunstoff Handbuch, Band IV, Polyolefins, Carl Hanser Verlag (1969), pages 39-51. Typical pressures range from 1000 to 3000 bar. The polymerization temperature is preferably 150-350°C. Initiators of the formation of free radicals (initiators of free radical polymerization) are well known, for example, initiators based on organic peroxide.

Suitable LDPE is commercially available from Borealis, LyondellBasell, Exxon, Sabic, or other suppliers.

The amount of LDPE present in the sealing layer is from 0 to 50, preferably from 0 to 45, more preferably from 0 to 40 mass%.

Therefore, the amount of mLLDPE used in the sealing layer generally ranges from 50 to 100, preferably 55 to 100, and more preferably 60 to 100% by weight of the total amount of the sealing layer, i.e. second layer of polyethylene.

The amount of plastomer used in the sealing layer generally ranges from 30 to 70, preferably from 35 to 65, such as 40 to 60% by weight of the total amount of the sealing layer, that is, the second layer of polyethylene.

The second layer of polyethylene in the extrusion lamination structure may be a single layer film (layer C only).

The second layer of polyethylene in the extrusion lamination structure can also be multilayer. Multilayer films are preferably made from at least two layers, ideally at least three layers, such as 3 layers, 5 layers or 7 layers.

For example, one additional layer (C-2) of the second polyethylene layer may be an LLDPE as described for layer A, preferably a multimodal such as a bimodal LLDPE, more preferably a bimodal ethylene/1-butene/C ₆ -C ₁₂ alpha-olefin terpolymer , with a density from 926 to 950 kg/m ³ .

In one embodiment of the present invention, the second layer of polyethylene in the extrusion lamination structure contains a second additional film layer (C-3) forming a 3-layer C-3/C-2/C film structure.

The second additional film layer C-3 is preferably made from the same polymer as described above for the sealing layer C.

Layers C, C-2 and C-3 may all be of equal thickness or, alternatively, layer C-2, in this case forming the inner layer, may be thicker than each of C-3 and C forming the outer layers.

The corresponding 3-layer film contains two outer layers (C-3 and C), each of which constitutes from 10 to 35%, preferably from 15 to 30% of the total thickness of the 3-layer film, an inner layer (i.e. C- 2), constituting the remaining thickness, is, for example, from 30 to 80%, preferably from 40 to 70% of the total thickness of the 3-layer film.

In another embodiment of the present invention, the second layer of polyethylene in the extrusion lamination structure may comprise a seal layer C as above, at least one additional layer C-2 as above, and an additional 3 additional layers C-4, C-5 and C-6, with the formation of the film structure C-6/C-5/C-4/C/C-2.

In this case, C-2, C-4 and C-5 consist of LLDPE, which may represent the same LLDPE

- 11 043619 in all three layers. Alternatively, the three layers may consist of different LLDPEs or the middle layer of the three layers, in which case C-4 may consist of one LLDPE and two sandwich layers, C-2 and C-5 may consist of another LLDPE .

Suitable LLDPEs are described above for layer A of the film forming the first layer of polyethylene.

The C-6 layer consists of a mixture of LLDPE and metallocene-catalyzed linear low-density polyethylene (mLLDPE).

Suitable LLDPEs are described above for layer A of the film forming the first layer of polyethylene.

Suitable mLLDPEs are described above for the sealing layer C of the second polyethylene layer.

The amount of LLDPE in this layer ranges from 40 to 80, preferably from 50 to 70 and more preferably from 55 to 65 wt.%, therefore mLLDPE is present in an amount from 20 to 60, preferably from 30 to 50 and more preferably from 35 up to 34 wt.%.

All layers can be of equal or different thickness. For example, the sealing layer C and layer C-6 may each constitute from 5 to 15%, preferably from 8 to 12 wt.% of the total thickness, and layers C-5, C-4 and C-2 make up the balance, these three layers can be of equal thickness. Layers C-5, C-4 and C-2 may also have varying thicknesses such as 10 to 25%/30 to 60%/10 to 25%, preferably 15 to 20%/40 to 50%/15 to 20%, where the total film thickness is 100%.

The second polyethylene layer may optionally comprise a layer D of HDPE between the above multilayer structures or connected to a sealing film C representing a single layer film. The HDPE layer can act as a barrier layer and/or as a reinforcing layer.

When used in a multilayer HDPE structure, barrier layer D may be located at any location between two adjacent layers, such as C-3/D/C-2/C or C-3/C-2/D/C, or C- 6/D/C5/C-4/C/C-2, C-6/C-5/D/C-4/C/C-2, and so on.

A suitable HDPE barrier layer D consisting of an HDPE polymer may comprise a single HDPE polymer component or a mixture of said HDPE polymer component with one or more other HDPE polymer components. Mainly for economic reasons, in one embodiment of the present invention, where layer D consists of one HDPE polymer or a mixture of two different HDPE polymers, it is preferred. In the case where layer D consists of a mixture of two HDPE polymers, the same may be present in any given weight ratio, typically the two HDPE polymers are then present in a weight ratio of 30:70 to 70:30, more preferably from 60:40 to 40:60, HDPE polymers used in the present invention are polyethylenes with a density of at least 940, preferably at least 945, more preferably in the range of 950 to 980 kg/m ³ such as 950 to 965 kg/ ^m3 . In particular, it is preferable that the density of the HDPE polymer used in the present invention is at least 955 kg/m ³ .

The HDPE polymer used in the present invention refers to polyethylene, which may be either a homopolymer or a copolymer containing minor amounts of repeating units derived from one or more alpha-olefins of 3 to 20 carbon atoms, preferably 3 to 10 and more preferably from 3 to 6 carbon atoms. The comonomer content of the copolymer may generally be from 0.25 to 10.0, more preferably 0.5 to 5.0 mol%, and more preferably the upper limit of the comonomer content is 2.5 mol%. In the present invention, both homopolymers and copolymers of polyethylene are equally preferred.

The HDPE polymer used in the present invention may be unimodal with respect to properties such as molecular weight distribution and/or comonomer content, or the HDPE polymer used with the present invention may be multimodal, in particular bimodal, with respect to properties such as distribution molecular weight and/or comonomer content.

A preferred embodiment of the present invention is a multimodal HDPE polymer containing at least a lower molecular weight (LMW) component and a higher molecular weight (HMW) component. These components may be present in any desired ratios, with a typical split, ie, weight ratios between LMW component and HMW component being from 10:90 to 90:10, preferably 40:60 to 60:40. The LMW and/or HMW component may be a homo- or copolymer, preferably at least one of the LMW and HMW components is a homopolymer. More preferably, the LMW component is a homopolymer and the HMW component is a homo- or copolymer, typically a copolymer.

According to a preferred embodiment of the present invention, layer D consists of either a unimodal HDPE polymer (with respect to molecular weight distribution) or a multimodal, preferably bimodal HDPE polymer (with respect to molecular weight distribution).

The melt flow rate (MFR) of the HDPE polymer used for Layer D of the present invention is not critical and may vary depending on the mechanical properties desired for the end application. In one preferred embodiment of the present invention, the MFR2 is preferably in the range of 0.05 to 10 g/10 min, preferably 0.1 to 2 g/10 min, and more preferably 0.3 to 0.8 g/10 min . In another preferred embodiment of the present invention, the MFR21 is preferably in the range of 2 to 12 g/10 min, even more preferably in the range of 6 to 8 g/10 min.

The HDPE polymer used in the present invention may be a known and, for example, commercially available polyethylene polymer, or said HDPE polymer may be prepared using any complex catalyst, typically Ziegler-Natta catalysts, a Cr catalyst along with single site catalysts. metal (SSC). The molecular weight distribution (MWD), expressed as Mw/Mn of the HDPE polymer used in the present invention, is not critical and may vary depending again on the desired mechanical properties required for the end application. The MWD is preferably in the range of from 2 to 35, where the preferred range for unimodal HDPE polymer is from 2 to 20, preferably from 3 to 10, in particular from 4 to 7 and more preferably from 4.5 to 6.0, with preferred the range for a multimodal, preferably bimodal HDPE polymer is 10 to 35, preferably 12 to 20, while in some embodiments of the present invention it can be set as broad as 15 to 35.

The HDPE polymer used in the present invention can be produced using polymerization reactions that are generally known in the art to which the present invention relates and are available to one skilled in the art to which the present invention relates. Additionally, they can be prepared in principle using any polymerization method, including solution, suspension and gas phase polymerization. The temperature of the polymerization reactions must be high enough to achieve acceptable catalyst activity, while not exceeding the softening temperature of the polymer, in order to avoid technological problems. Therefore, typical polymerization temperatures may range from 50 to 110°C, preferably from 75 to 105°C, and more preferably from 75 to 100°C. Suitable pressure limits for suspension polymerization are, for example, from 10 to 100 bar, preferably from 30 to 80 bar.

Suitable films, HDPE rubbers for the production of such films and their preparation are described, inter alia, in WO-A-1999/058584, WO-A-1999/051649, WO-A-2007/104513 and WO-A-2007/065644.

The film structure for the film forming the second layer of polyethylene in the extrusion lamination structure of the present invention can be obtained using any conventional film extrusion process known in the art to which the present invention relates, for example, using cast film or film produced extrusion blow molding. Preferably, the film is produced using a blown film, more preferably using coextrusion processes which are generally known and available to one skilled in the art to which the present invention relates.

Typical processes for producing the film structure of the present invention are extrusion processes using annular die extrusion processes followed by blowing to form a bubble which collapses between rollers after curing. This film can then be longitudinally separated, cut or post-processed, such as using a newspaper head, if required. For these purposes, traditional film production technologies can be used. Typically, the layers are coextruded at temperatures ranging from 160 to 240°C and cooled by blowing gas (usually air) at a temperature of 5 to 50°C to provide a frost line (cloud line) height of 1 or 2 to 8 times the diameter of the mouthpiece. The inflation ratio may range from 1 (1:1) to 4 (1:4), preferably from 1.5 (1:1.5) to 3.5 (1:3.5), more preferably from 2 ( 1:2) to 3 (1:3).

In the case when the second layer of polyethylene is oriented in the longitudinal direction, a procedure similar to that described for the first layer of polyethylene is carried out.

A layer of ethylene-vinyl alcohol copolymer.

The structure contains a layer containing a copolymer of ethylene and vinyl alcohol. Preferably, the layer consists essentially of a copolymer of ethylene and vinyl alcohol. As used herein, the term essentially consists of means that the layer may contain minor amounts of additives known in the art, such as antioxidants, and other polymers, provided that such other polymers do not adversely affect influence on the properties of the oxygen barrier of a copolymer of ethylene and vinyl alcohol. Typically, the layer then contains at least 95, preferably at least 98, and more preferably at least 99% by weight ethylene vinyl alcohol copolymer.

Preferably, the ethylene-vinyl alcohol copolymer has an ethylene unit content of from 20 to 45, preferably from 25 to 40 and more preferably from 27 to 37% by mole. Additionally, the ethylene-vinyl alcohol copolymer preferably has a density of 1000 to 1250, preferably 1050 to 1230, and more preferably 1100 to 1220 kg/ ^m3 . Additionally, preferably has a melt flow rate MFR ₂ (measured at a load of 2.16 kg at a temperature of 190°C) from 1 to 10 g/10 min, preferably from 2 to 8 g/10 min, and more preferably from 2.5 to 7 .5 g/10 min.

The ethylene-vinyl alcohol copolymer layer preferably has a specific gravity of 1 to 10, preferably 1 to 8, and more preferably 2 to 6 g/ ^m2 . Too low a specific gravity may result in insufficient barrier properties. Too high a specific gravity results in unreasonably high structure costs and may also result in a thicker coating than required. Additionally, recyclability may be compromised if the structure contains too much ethylene vinyl alcohol copolymer.

Adhesive layer.

The structure contains adhesive layers on both sides of the layer containing a copolymer of ethylene and vinyl alcohol. Their purpose is to improve adhesion between the layer containing ethylene-vinyl alcohol copolymer and layers of polyethylene.

The polymers used in the adhesive layers are preferably ethylene-based polymers, such as copolymers of ethylene with a polar comonomer. Preferably, the polymers in the adhesive layers are graft copolymers of ethylene with polar comonomers, such as organic acids and organic acid derivatives. The organic acids and their derivatives are preferably selected from the group of double bond containing organic acids and their derivatives, and preferably from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, nadic acid, citraconic acid, itaconic acid, cretonic acid , their anhydrides, their metal salts, their esters, their amides, their imides and mixtures of two or more of the above compounds.

When the polymers used in the adhesive layers are ethylene graft copolymers, the base polymer used in the grafting process may be any suitable ethylene polymer, such as high density polyethylene, medium density polyethylene, linear low density polyethylene, ethylene based plastomer, elastomer ethylene-based, low-density polyethylene or mixtures of two or more of the above polymers.

When the polymers used in the adhesive layers are ethylene graft copolymers, they can be prepared according to methods known in the art to which the present invention relates. For example, polymers can be produced using extruder grafting by feeding a base polymer, a graft comonomer, and a free radical generator such as peroxide into the extruder and extruding the mixture at a temperature that exceeds the melting temperature of the base polymer and the decomposition temperature of the free radical generator. On the other hand, the temperature must be less than the decomposition temperature of the base polymer.

The polymers used in the adhesive layers preferably have an MFR2 of 0.5 to 10 g/10 min, preferably 1 to 10 g/10 min, and more preferably 2 to 10 g/10 min. Additionally, the polymers used in the adhesive layers preferably have a density of 905 to 940, preferably 910 to 940, and more preferably 915 to 940 kg/m ³ .

Polymers suitable for use in adhesive layers are commercially available, for example from DuPont under the trade name Bynel®. As such, polymers with higher amounts of anhydride incorporated are preferred and, for example, Bynel® 41E710 has given good results.

Each of the adhesive layers has a specific gravity of 1 to 10, preferably 2 to 8, and more preferably 2 to 6 g/m ² . Too low a specific gravity may result in insufficient adhesion. Too high a specific gravity does not have any serious technical disadvantages, but it does result in unreasonably high structure costs and may also result in a thicker coating than required.

It should be understood that the structure may comprise additional layers to a first polyethylene layer, a second polyethylene layer, an ethylene-vinyl alcohol copolymer layer, and an adhesive layer. If any such additional layer has good adhesion to the ethylene-vinyl alcohol copolymer layer, then such layer may be adjacent to the ethylene-vinyl alcohol copolymer layer and the adhesive layer is adjacent to such additional layer. However, when such a layer with good adhesion to the ethylene copolymer layer is absent, the adhesive layer may be adjacent to the ethylene vinyl alcohol copolymer layer.

Receipt process.

Extrusion coating.

According to one preferred embodiment of the present invention, the structure is obtained using extrusion coating. In this process, an ethylene-vinyl alcohol copolymer layer, adhesive layers, and a second layer of polyethylene are extruded onto a substrate formed by the first layer of polyethylene. The ethylene-vinyl alcohol copolymer layer, the adhesive layers, and the second polyethylene layer are extruded onto the substrate through a slot die, or more specifically, through a multiple slot die structure. Extrusion coating, including co-extrusion, is well known to one skilled in the art to which the present invention relates.

As is well known in the art to which the present invention relates, it is possible to improve adhesion between layers by treating the substrate with a flame or corona discharge. Additionally, the melt is treated with ozone to improve adhesion.

Once the ethylene-vinyl alcohol copolymer layer, the adhesive layers and the second polyethylene layer are extruded onto the substrate, the structure is passed through the gap between the chill roll and the pressure roll. The chill roll is typically water cooled and has the purpose of cooling the extruded structure to a suitable temperature. Typically, the surface temperature of the chill roller may range from about 15°C to about 60°C.

According to one preferred embodiment of the present invention, the second layer of polyethylene comprises, and preferably substantially consists of, low density polyethylene. Typically, the layer is extruded at a melt temperature of from about 275 to about 330°C. As used herein, the term essentially consists of means that the second layer of polyethylene may contain minor amounts of additives known in the art, such as antioxidants, and other polymers, provided that the other polymers do not have an adverse effect. negative impact on the manufacturability of low-density polyethylene. Typically, the amount of additives and other polymers in such a case is no more than 2, preferably no more than 1, and substantially preferably no more than 0.5% by weight. In any case, when the structure is obtained using extrusion coating, the second layer of polyethylene typically contains at least 40, preferably at least 50, more preferably at least 75, and substantially preferably at least 90% by weight of polyethylene low density. The above numerical indicators are given as a percentage of the total mass of the second layer of polyethylene.

Low density polyethylene typically has a melt flow rate MFR ₂ (measured under a 2.16 kg load at 190°C) from 1 to 15 g/10 min, preferably from 2 to 10 g/10 min and even more preferably from 3 to 8 g/10 min. Additionally, it typically has a density of 915 to 930, preferably 916 to 926, and even more preferably 917 to 925 kg/m ³ . Low density polyethylene can be produced using an autoclave reactor process as described in EP-A-1777238, or using a tubular reactor process as described in WO-A2013/132009, WO-A-2013/083285, WO-A -2013178241 and WO-A-2013/178242, Preferably, low density polyethylene is produced using a tubular reactor process.

The low density polyethylene layer typically has a specific gravity of 5 to 50, preferably 5 to 30 g/ ^m2 , such as 5 to 20 g/ ^m2 .

According to another preferred embodiment of the present invention, the second layer of polyethylene comprises a heat-sealable ethylene copolymer, such as linear low density polyethylene or an ethylene-based plastomer, or an ethylene-based elastomer. The layer may additionally contain low-density polyethylene to improve processability. Alternatively or additionally, the layer can be co-extruded with a layer of low density polyethylene to provide good processability when applied by extrusion coating in the processing line. In this embodiment of the present invention, the second layer of polyethylene typically contains at least 20, preferably at least 25, and more preferably at least 30% by weight of heat sealable ethylene copolymer. The upper limit is not critical and may be around 100, such as 95, 90% by weight. The above numerical indicators are given as a percentage of the total mass of the second layer of polyethylene. Typically, the layer is extruded at a melt temperature of from about 275 to about 330°C.

Preferably, the heat sealable ethylene copolymer is linear low density polyethylene (LLDPE) produced using either a Ziegler-Natta catalyst (znLLDPE) or a metallocene catalyst (mLLDPE), or an ethylene-based plastomer.

The MFR2 (190°C, 2.16 kg, ISO 1133) of a suitable znLLDPE is in the range of 0.01 to 20 g/10 min, preferably in the range of 0.05 to 10 g/10 min, more preferably in the range of 0 .1 to 6.0 g/10 min and even more preferably in the range from 0.1 to 5.0 g/10 min.

znLLDPE may have a density ranging from 910 to 950, preferably 915 to 945, preferably such as 920 to 940 kg/m ³ .

Mw/Mn znLLDPE can be within fairly wide limits. Preferably, the Mw/Mn is 3 or more, such as 6 or more, even 10 or more. Limits from 3.5 to 30 are used.

znLLDPE contains at least one or two comonomer(s). Suitable comonomers are C ₃ -C ₁₀ alpha-olefin comonomers. Therefore, znLLDPE may be a copolymer of ethylene and one of the C ₃ -C ₁₀ alpha-olefin comonomers, or a terpolymer of ethylene and two different C ₃ -C ₁₀ alpha-olefin comonomers. Preferably, the comonomers are selected from the group of 1-butene, 1-hexene and 1-octene. Preferably the comonomer used is 1-butene and/or 1-hexene. Preferred terpolymers contain comonomers of 1-butene and 1-hexene.

The total comonomer content of the overall polymer is from 0.3 to 7.0, preferably from 0.6 to 4.5, more preferably from 1.0 to 3.5 and most preferably from 1.2 to 2.3% by mole .

In the case where znLLDPE is a terpolymer of ethylene and two different C ₃ -C ₁₀ alpha-olefin comonomers, preferably 1-butene and 1-hexene, 1-butene is present in an amount of from 0.1 to 3.0, preferably from 0.2 to 2.0, more preferably from 0.3 to 1.5 and most preferably from 0.4 to 0.8% by mole, and hexene is present in an amount from 0.2 to 4.0, preferably from 0.4 to 2.5, more preferably from 0.7 to 2.0 and most preferably from 0.8 to 1.5% by mole.

znLLDPE may be unimodal or multimodal, preferably multimodal. Unimodal znLLDPE has a single peak in the gel permeation chromatography spectrum because it is produced using a one-step process. Most preferably, when the znLLDPE is multimodal, the znLLDPE is derived from a homopolymer component and a copolymer component. These polymers are well known in the art and are available from Borealis and others, for example, under the trade name Borstar.

Preferably, such multimodal, such as bimodal znLLDPE, is produced by multi-stage polymerization using the same catalyst. Therefore, two slurry reactors or two gas phase reactors can be used. However, preferably such multimodal, such as bimodal znLLDPE, is prepared using slurry polymerization in a loop reactor followed by gas phase polymerization in a gas phase reactor.

As described in the specification of the present patent application, the mLLDPE polymer is an ethylene copolymer with a density of 940 kg/m ³ or less. Preferably mLLDPE may have a density of 905 to 940, more preferably 910 to 937 kg/m ³ . In one preferred embodiment of the present invention, use even at a density of 915 to 925 kg/m ³ is permitted.

mLLDPE is derived from ethylene with at least one C ₃ -C ₂₀ alpha-olefin comonomer, preferably a C ₃ -C ₁₂ alpha-olefin comonomer, for example 1-butene, 1-hexene or 1-octene. Preferably mLLDPE is a binary copolymer, that is, the polymer contains ethylene and one comonomer or terpolymer, i.e. the polymer contains ethylene and two or three, preferably two comonomers. Preferably mLLDPE contains an ethylene-hexene copolymer, an ethylene-octene copolymer, an ethylene-butene copolymer, or an ethylene terpolymer with 1-butene and 1-hexene comonomers. The amount of comonomer present in mLLDPE is preferably 0.5 to 12, more preferably 2 to 10, and most preferably 4 to 8 mol%. Alternatively, the comonomer content present in mLLDPE may be from 1.5 to 10, preferably from 2 to 8 wt.%.

The MFR2 of mLLDPE is preferably in the range from 0.01 to 20 g/10 min, more preferably from 0.2 to 10 g/10 min, even more preferably from 0.3 to 6.0 g/10 min and most preferably from 0 .4 to 5.0 g/10 min.

mLLDPE can be unimodal or multimodal, both are preferred. As used herein, the term unimodal means that the molecular weight profile of the polymer includes a single peak, and mLLDPE is preferably prepared by copolymerizing ethylene in a single reactor in the presence of a single metallocene catalyst. Unimodal mLLDPE polymers preferably have a narrow molecular weight distribution. Preferably, the Mw/Mn is 2 to 4, more preferably 2 to 3.

Multimodal can be understood as a bimodal molecular weight distribution or a bimodal comonomer distribution (for example, the MFR of the components is identical, but they contain identical comonomers in different quantities). Bimodal mLLDPE contains an LMW component and an HMW component. Both the LMW and HMW components of the multimodal mLLDPE are preferably ethylene copolymers as stated above.

The molecular weight distribution, Mw/Mn, of the multimodal mLLDPE can be below 30, preferably in the range of 2-5.

Suitable mLLDPEs are commercially available from ExxonMobil Chemical, Nova, Dow, Basell, and are provided by way of example.

Alternatively, suitable mLLDPE polymers can be prepared using a known method according to or similar to conventional polymerization processes, including solution, suspension and gas phase polymerization, as described in the literature on polymer chemistry.

Unimodal mLLDPE, as indicated above, is preferably prepared using a one-step polymerization, for example, solution polymerization, slurry or gas phase, preferably suspension polymerization in a slurry tank or more preferably in a loop reactor in a manner known in the art to which the present invention relates. As an example, said unimodal mLLDPE can be produced, for example, using a one-step loop reactor polymerization process according to the principles

- 16 043619 below, for the polymerization of a low molecular weight fraction in a loop reactor using a multi-stage process, of course, except that the process conditions (for example, the supply of hydrogen and comonomer) are adjusted to ensure the properties of the final unimodal polymer.

Multimodal (eg, bimodal) mLLDPE, as described above, can be prepared using mechanical mixing of two or more separately prepared polymer components, or preferably using in situ mixing in a multi-stage polymerization process during the process of obtaining the polymer components. Both mechanical and in situ mixing are well known in the art to which the present invention relates.

Accordingly, preferred multimodal mLLDPE polymers are prepared using in-situ mixing in a multi-stage process, that is, two or more polymerization stages, including solution, slurry, and gas phase polymerization, in any order. Alternatively, said multimodal mLLDPE can be produced by using two or more different polymerization catalysts, including multisite or dual site catalysts in a one-step polymerization process.

Preferably, the multimodal mLLDPE as described above is produced by at least two-stage polymerization using the same catalyst, for example a single site metal catalyst. Therefore, for example, two slurry reactors or two gas phase reactors, or any combination thereof, in any order, can be used.

mLLDPE, as stated above, can be prepared using any conventional metal single site catalyst (SSC), such SSC catalysts include metallocenes.

All of these catalysts are well known in the art to which the present invention relates. In the case of mLLDPE, the use of metallocene catalysts is preferred. The preparation of the metallocene catalyst can be carried out according to or similar to methods known in the literature and is within the competence of one skilled in the art to which the present invention relates. Therefore, for obtaining, see for example EP-A-129368, WO-A-1998/056831, WO-A-2000/034341, EP-A-260130, WO-A-1997/028170, WO-A-1998 /046616, WO-A-1998/049208, WO-A1999/012981, WO-A-1999/019335, WO-A-1998/056831, WO-A-2000/034341, EP-A-423101 and EP-A -537130, WO 2005/002744 which describes a preferred catalyst and process for producing said mLLDPE component.

Suitable plastomers used in layer A of the first polyethylene layer are ethylene-based plastomers with a density below 915 kg/m ³ . An ethylene-based plastomer is a copolymer of ethylene and propylene or a C4-C ₁₀ alpha-olefin. Suitable C4-C ₁₀ alpha-olefin includes 1-butene, 1-hexene and 1-octene, preferably 1-butene or 1-octene and more preferably 1-octene. Preferably, copolymers of ethylene and 1-octene are used.

Preferred ethylene-based plastomers have a density in the range of 860 to 915, more preferably in the range of 870 to 910 kg/m ³ .

The MFR ₂ (ISO 1133; 190°C; 2.16 kg) of a suitable ethylene-based plastomer is in the range of 2.0-30 g/10 min, preferably in the range of 3.0-20 g/10 min and more preferably in the range 5.015.0 g/min.

The melting point (measured using DSC according to ISO 11357-3:1999) of a suitable ethylene-based plastomer is below 130°C, preferably below 120°C, more preferably below 110°C and most preferably below 100°C. Additionally, a suitable ethylene-based plastomer has a glass transition temperature Tg (measured using DMTA according to ISO 6721-7) below -25, preferably below -30, more preferably below -35°C.

In the case of a copolymer, it is a copolymer of ethylene and propylene and has an ethylene content of 10 to 55, preferably 15 to 50, and more preferably 18 to 48 wt%. In the case of a copolymer, it is a copolymer of ethylene and a C4-C ₁₀ alpha-olefin, and has an ethylene content of 60 to 95%, preferably 65 to 90%, and more preferably 70 to 88% by weight.

The molecular weight distribution Mw/Mn of a suitable ethylene-based plastomer is most often below 4, such as 3.8 or below, but is at least 1.7. Preferably it is from 1.8 to 3.5.

A suitable ethylene-based plastomer may be any copolymer of ethylene and propylene or ethylene and a C4-C ₁₀ alpha-olefin with the above properties, which are commercially available, for example from Borealis under the trade name Queo, from Dow Chemical Corp (USA) under the trade name Engage or Affinity, or from Mitsui under the Tafmer brand.

Alternatively, these ethylene-based plastomers can be prepared using known processes, one or two step polymerization processes, including solution polymerization, suspension polymerization, gas phase polymerization, or combinations thereof, in the presence of suitable catalysts, such as vanadium oxide catalysts or catalysts with single center of polymerization on the metal, for example, metallocene catalysts or catalysts with

- 17 043619 difficult geometry, known to a person skilled in the field of technology to which the present invention relates.

Preferably, these ethylene-based plastomers are produced using a one or two step solution polymerization process, preferably using a high temperature solution polymerization process at a temperature higher than 100°C. Such a process is essentially based on the polymerization of a monomer and a suitable comonomer in a liquid carbon solvent in which the resulting polymer is dissolved. Polymerization is carried out at a temperature above the melting point of the polymer, resulting in a polymer solution. This solution is evaporated to separate the polymer from the unreacted monomer and solvent. The solvent is then recovered and recycled back into the process.

Preferably, the solution polymerization process is a high temperature solution polymerization process using a polymerization temperature higher than 100°C. Preferably, the polymerization temperature is at least 110, more preferably at least 150°C. The polymerization temperature can be up to 250°C.

The pressure in such a solution polymerization process is preferably in the range of 10 to 100, preferably 15 to 100, and more preferably 20 to 100 bar.

The liquid hydrocarbon solvent used is preferably a C ₅ - ₁₂ hydrocarbon, which may be an unsubstituted or substituted by using a C 1 - ₄ alkyl group, such as pentane, methyl pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane and hydrogenated gasoline. More preferably, unsubstituted C ₆ - ₁₀ hydrocarbon solvents are used. Such processes are described, inter alia, in WO-A-1997/036942, WO-A-2006/083515, WO-A-2008/082511, and WO-A-2009/080710.

The ethylene-vinyl alcohol copolymer degrades at high temperatures and, therefore, the extrusion temperature of the ethylene-vinyl alcohol copolymer must be significantly lower than the extrusion temperature of the second layer of polyethylene. Suitable extrusion temperatures range from about 200 to about 240, preferably from 210 to 240, and preferably about 230°C. As is well known in the art to which the present invention relates, extrusion of the ethylene-vinyl alcohol copolymer must be carried out under very narrow temperature limits to avoid degradation.

The ethylene-vinyl alcohol copolymer layer preferably has a specific gravity of 1 to 10, preferably 1 to 8, and more preferably 2 to 6 g/ ^m2 . Too low a specific gravity may result in insufficient barrier properties. Too high a specific gravity does not have any serious technical disadvantages, but it does result in unreasonably high structure costs and may also result in a thicker coating than required.

The polymers used in the adhesive layers are also preferably extruded at temperatures lower than those of polyethylene. Suitable extrusion temperatures range from about 200 to about 280, preferably from 220 to 260°C.

Each of the adhesive layers typically has a specific gravity of 1 to 10, preferably 1 to 8, and more preferably 2 to 6 g/m ² . Too low a specific gravity may result in insufficient adhesion. Too high a specific gravity does not have any serious technical disadvantages, but it does result in unreasonably high structure costs and may also result in a thicker coating than required.

Also, if required, it is possible to extrude additional layers onto the first layer of polyethylene. The extrusion conditions for such additional layers are determined by the type of polymers included in such additional layers. For example, if the second polyethylene layer is a linear polymer, such as linear low density polyethylene, then it is preferable to co-extrude the low density polyethylene layer with the second polyethylene layer to ensure good processability. Such additional layer of polyethylene typically has a specific gravity of from 1 to 50, preferably from 2 to 30, such as from 2 to 20 g/m ² .

The line speed for extrusion coating is typically from 50 to 1000, preferably from 100 to 650 and generally from 150 to 500 m/min.

Extrusion lamination.

According to another preferred embodiment of the present invention, the structure is obtained using extrusion lamination. The extrusion lamination process is similar to extrusion coating, but in extrusion lamination, layers are extruded between two substrates. Thus, the first layer of polyethylene and the second layer of polyethylene are used as substrates in the extrusion lamination process. The ethylene-vinyl alcohol copolymer layer and adhesive layers are then extruded between the first polyethylene layer and the second polyethylene layer. If required, additional layers can also be extruded between the first polyethylene layer and the second polyethylene layer. Such additional layers may, depending on need, be additional polymers, such as additional layers of polyethylene.

The line speed in extrusion lamination process is generally from 50 to 1000,

- 18 043619 preferably from 100 to 650 and essentially from 150 to 500 m/min.

In the case where the structure is obtained using extrusion lamination, the second layer of polyethylene is preferably a film made from polyethylene as described above.

In the case where the ethylene vinyl alcohol copolymer layer and the adhesive layers are extruded between two films, the structure is passed through the gap between the cooling roller and the pressure roller. The chill roll is typically water cooled and has the purpose of cooling the extruded structure to a suitable temperature. Typically, the surface temperature of the chill roller may range from about 15°C to about 60°C.

The ethylene-vinyl alcohol copolymer degrades at high temperatures and, therefore, the extrusion temperature of the ethylene-vinyl alcohol copolymer must be significantly lower than the extrusion temperature of the second layer of polyethylene. Suitable extrusion temperatures range from about 200 to about 240°C, preferably from 210 to 240°C, and advantageously from about 230°C.

The ethylene-vinyl alcohol copolymer layer preferably has a specific gravity of 1 to 10, preferably 1 to 8, and more preferably 2 to 6 g/ ^m2 .

Too low a specific gravity may result in insufficient barrier properties. Too high a specific gravity does not have any serious technical disadvantages, but it does result in unreasonably high structure costs and may also result in a thicker coating than required.

The polymers used in the adhesive layers are also preferably extruded at temperatures lower than those of polyethylene. Suitable extrusion temperatures range from about 200 to about 280, preferably from 220 to 260°C.

Each of the adhesive layers typically has a specific gravity of 1 to 10, preferably 1 to 8, and more preferably 2 to 6 g/m ² . Too low a specific gravity may result in insufficient adhesion. Too high a specific gravity does not have any serious technical disadvantages, but it does result in unreasonably high structure costs and may also result in a thicker coating than required.

As stated above, additional layers may also be extruded between the first polyethylene layer and the second polyethylene layer. Therefore, according to a substantially preferred embodiment of the present invention, layers of low density polyethylene are extruded between adhesive layers and polyethylene films. Such polyethylene layers typically have a specific gravity of from 1 to 50, preferably from 2 to 30, such as from 2 to 20 g/m ² .

Such additional layers therefore comprise, preferably are substantially composed of, low density polyethylene. As used herein, the term essentially consists of means that the additional layer of polyethylene may contain minor amounts of additives known in the art to which the present invention relates, such as antioxidants and other polymers, provided that the other polymers do not have a detrimental effect. influence on the manufacturability of low-density polyethylene. Typically, the amount of additives and other polymers in such a case is no more than 2, preferably no more than 1, and substantially preferably no more than 0.5% by weight. In any case, such additional layers typically comprise at least 40%, preferably at least 50, more preferably at least 75, and substantially preferably at least 90% low density polyethylene.

Low density polyethylene typically has a melt flow rate MFR ₂ (measured at a load of 2.16 kg and a temperature of 190°C) from 1 to 15 g/10 min, preferably from 2 to 10 g/10 min and even more preferably from 3 to 8 g/10 min. Additionally, it typically has a density of 915 to 930, preferably 916 to 926, and even more preferably 917 to 925 kg/m ³ . Low density polyethylene can be produced using the autoclave reactor process as described above. It may also be a mixture of two low density polyethylenes, one produced using an autoclave reactor process, one produced using a tubular reactor process. Preferably, low density polyethylene is produced using a tubular reactor process.

Advantages of the present invention.

The structures of the present invention are recyclable and therefore contain ethylene copolymers. Essentially all of the polymers contained in the structures of the present invention are ethylene-based homo- or copolymers.

Compared to the prior art, the processes and structures of the present invention offer great advantages. The process has one less processing step compared to the standard lamination process. Additionally, the structures of the present invention provide a more reliable solution compared to barrier film (PE/EVOH) structures. In particular, barrier film structures cannot be easily oriented because the ethylene vinyl alcohol copolymer containing layer cannot withstand orientation. The present invention relates to a solution where orientation of the barrier layer can be avoided. The present invention provides a simpler solution since prior art barrier layer films

- 19 043619 techniques have a complex structure, with films with at least five layers obtained by coextrusion. Additionally, if the film is required to have a specific color, such as white, this poses additional challenges for the prior art film if the structure contains an ethylene vinyl alcohol copolymer.

The method is flexible and avoids many of the problems encountered in prior art processes. For example, fast and efficient cooling of the structure. Thus, the vastly different crystallization rates of ethylene-vinyl alcohol copolymer and polyethylene do not cause problems as may occur in an air-cooled blown film process.

The adhesives used in adhesive lamination are generally not ethylene polymer based and this does not pose a recycling problem. Additionally, the adhesive lamination process requires additional dwell time for adhesion. In addition, such adhesives may leave degradation products in the film, such degradation products may have adverse health or environmental impacts.

The inventors of the present invention have further found that the curling of the material can be controlled. When rigid coating is applied to substrates such as paper, cardboard or oriented polyesters (such as OPET), the structure tends to curl in the direction of coating. The extrusion coating process of the present invention, where the substrate is a longitudinally oriented polyolefin film such as polyethylene film, allows the curl tendency to be influenced by adjusting the tension of the web. It has also been found that films with a multilayer structure according to the present invention and films obtained by the method according to the present invention allow the temperature window to be extended even up to 40°C.

Description of methods.

The longitudinal tensile modulus was measured at room temperature according to ISO 527-3.

Gloss (at 20°) was measured according to ASTM D2457.

Turbidity was measured according to ASTM D1003.

Examples

The following experimental tests use the following examples:

PE1: PE1 is a bimodal terpolymer obtained using a Ziegler-Natta catalyst (C2/C4/C6) Grade BorShape™ Borshape FX1001 from Borealis AG. With an MFR ₅ of 0.85 g/10 min and a density of 931 kg/m ³ .

PE2: PE2 is Hostalen 7740 F2 high-density polyethylene from LyondellBasell. With MFR ₅ 1.8 g/10 min and density 948 kg/m ³ .

PE3: PE3 is a plastomer based on ethylene and octene Queo™ 8201 from Borealis AG. With MFR (190/2.16) 1.1 g/10 min, unimodal molecular weight distribution and density 882 kg/m ³ . It was produced using a solution polymerization process using a metallocene catalyst. It contains process stabilizers.

PE4: PE4 - low density polyethylene CT7200 from Borealis AG. With MFR ₂ (190/2.16) 5 g/10 min and density 918 kg/m ³ . It was produced using a high pressure polymerization process in a tubular reactor.

PE5: PE5 is low density polyethylene FT5230 from Borealis AG. With MFR2 (190/2.16) 0.7 g/10 min and density 923 kg/m ³ . It was produced using a high pressure polymerization process in a tubular reactor.

PE6: PE6 is Exceed 1018CA linear low-density polyethylene from ExxonMobil. With MFR ₂ (190/2.16) 1 g/10 min and density 918 kg/m ³ . Represents LLDPE produced using a metallocene catalyst.

PE7: PE7 - high density polyethylene FB1520 from Borouge Pte Ltd. With MFR ₂₁ (190/21.6) 7 g/10 min and density 952 kg/m ³ . It has a multimodal molecular weight distribution.

PE8: PE8 - medium density polyethylene Borshape FX1002 from Borealis AG. With MFR ₅ (190/5) 2 g/10 min and density 937 kg/m ³ .

PE9: PE9 - high density polyethylene FB1460 from Borouge Pte Ltd. With MFR ₂₁ (190/21.6) 6 g/10 min and density 946 kg/m ³ . It has a multimodal molecular weight distribution.

A1: A1 - technological additive Polybatch® AMF 705 HF from A. Schulman

A2: A2 is Polybatch® CE-505-E, which is a 5% erucamide, polyethylene-based friction-reducing concentrate from A. Schulman.

A3: A3 is a masterbatch of the anti-caking and friction-reducing agent Polybatch® AB 35 VT from A. Schulman.

A4: A4 - Schulman Polywhite NG8600 dye masterbatch containing 60% titanium dioxide by weight.

- 20 043619

EVOH: EVOH is an ethylene vinyl alcohol copolymer, EVAL™104B, from Kuraray. With MFR2 (190/2.16) 4.4 g/10 min and density 1.18 kg/ ^m3 .

ADP: ADP is Bynel® 41E710 adhesive polymer, from DuPont™. An anhydride-modified linear low-density polyethylene with a high level of anhydride modification. With MFR2 2.7 g/10 min and density 922 kg/ ^m3 .

Film 1.

The first film (used as substrate) IE1, IE2, IE3 was co-extruded on an Alpine 5-layer co-extrusion line with a die diameter of 400 mm, a blow-up ratio (BUR) of 1:2.7, a frozen line height of 3D and a die gap of 1.5 mm.

The resulting film had a thickness of 110 rm (blocking film).

The composition of 5 layers is given in table. 1.

Table 1

Film structure 1

Layer* A b With d e PE1 wt.% 98.5 98.5 98.5 80.0 PE2 wt.% 96.5 - - - - RES wt.% - - - - 20 A1 wt.% 0.5 - - - - A2 wt.% 1.5 1.5 1.5 1.5 - AZ wt.% 1.5 - - - -

Layers a-e are extruded using extruders a, b, c, d, and e of the 5-layer coextrusion line.

The stretching is carried out using a monodirectional stretching machine from Hosokawa Alpine AG Augsburg/Germany. The device consists of sections for preheating, drawing, annealing and cooling; each section has a specific one.

PE7 wt.% PE8 wt.% 95 95 95 PE9 wt.% 95 95 A1 wt.% 1 1 A2 wt.% 1 1 1 1 1 AZ wt.% 1 1 A4 wt.% 4 4 4 4 4

Layers a-g are extruded using extruders a, b, c, d, e, f and g of the 7-layer coextrusion line.

Example 1 (IE1).

Extrusion coating is carried out using the Beloit co-extrusion coating line. It uses a Peter Cloeren's EBR mouthpiece and feed tube to deliver five layers. The width of the die channel strip is 850-1000 mm, the maximum substrate width is 800 mm and the line speed is 100 m/min.

Extrusion was carried out at the following temperatures for EVOH and ADP at temperatures of 230 and 260°C, respectively, and PE4 at 280°C.

The structure is cooled on a chill roller (incoming cooling water temperature 15°C) and then rewound.

At the coating line, Film 1 obtained as described above was used as a substrate, on which a layer of ADP structure (adjacent to the substrate), EVOH, ADP and PE4 (outer layer) was applied. Each ADP layer has a specific gravity of 3 g/ ^m2 , the EVOH layer has a specific gravity of 4 g/ ^m2 , and the PE4 layer has a specific gravity of 10 g/ ^m2 .

A sample of the material was taken and it was determined that curling occurred in the substrate, with curling generally occurring in the direction of coating. Additionally, it was found that adjusting the tension of the web makes it possible to influence the tendency of the material to curl. Increasing the tension of the web will generally reduce the tendency to curl in the coating direction.

Example 2 (IE2).

Extrusion lamination is carried out using the Beloit co-extrusion coating line. It uses a Peter Cloeren's EBR mouthpiece and feed tube to deliver five layers. The width of the die channel strip is 850-1000 mm, the maximum substrate width is 800 mm and the line speed is 100 m/min.

- 21 043619

Extrusion was carried out for EVOH and ADP at temperatures of 230°C and 270°C, respectively, and

PE4 at 300°C.

The structure is cooled on a chill roller (incoming cooling water temperature 15°C) and then rewound.

Temperature to optimize the operation of the device and obtain a film with the desired properties. Heating is carried out at 105°C, stretching is carried out at 115°C, annealing and cooling are carried out at 110° with cooling to 40°C.

The blown film is fed into a stretcher where it is stretched between two rows of pinch rollers, the second pair moving at a higher speed than the first pair, resulting in a desired stretch ratio. To achieve a given thickness, stretching is carried out with the appropriate stretch ratio. (The stretch coefficient and the final thickness of the MDO film are given in Table 2). After exiting the stretching machine, the film is fed into a conventional winder where the film is cut to a specified width and wound to form a roll of film.

The properties of MDO film are also given in Table. 2.

table 2

Film 1 - oriented in the longitudinal direction

Primary film thickness [rm] BY Coefficient traction 4.5 Final film thickness [rm] MD/TD tensile test Parameter units 25 Tensile modulus MPa 860/1110 Optical properties Gloss (20°) % 136 Turbidity % 4

Film 2.

Film 2 was coextruded into a seven-layer structure according to table. 3 below. Where the total film thickness was 60 μm.

Table 3

Film structure 2

Layer* A b With d e f g % total thickness 10 20 12.5 15 12.5 20 10 PE5 wt.% 10 10 PE6 wt.% 88 88

At the coating line, films 1 and 2 obtained as described above were used as substrates. Layers of PE4, ADP, EVOH, ADP and PE4 were extruded between the films. Each ADP layer has a specific gravity of 5 g/ ^m2 , the EVOH layer has a specific gravity of 4 g/ ^m2 , and each PE4 layer has a specific gravity of 5.5 g/ ^m2 .

Example 3 (IE3).

We measured the oxygen and water vapor permeability of the structure according to Examples 1 and 2 using the Mocon Permatran-W MG device at a temperature of 38°C. A sample structure was placed in a testing area of 50 cm ² . The relative humidity on one side of the structure was 90%, and 0% on the other side. Oxygen permeability (OTR) and water vapor permeability (WVTR) were measured using a variety of samples over a period of 18 to 98 hours. Permeation rates are given in table. 4, expressed in g/(m ² -day). The values shown in the table represent the average of multiple measurements. Standard deviations are given in parentheses. The indicators indicate that the structures have very good barrier properties.

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Claims (9)

Table 4 OTR and WVTR structures of examples 1 and 2 Structure of Example OTR, g/(m ² -day) WVTR, g/(m ² -day) 1 0.80 (0.03) 3.80 (0.21) 2 1.21 (0.01) 2.13 (0.07) CLAIM 1. A multilayer structure comprising (i) a first layer of polyethylene as a first outer layer, said first layer of polyethylene oriented at least in a longitudinal direction; (o) a second layer of polyethylene as a second outer layer, wherein the second layer of polyethylene is non-oriented; (iii) an ethylene vinyl alcohol (EVOH)-derived layer between the first outer layer and the second outer layer; and (iv) an adhesive layer on each side of the EVOH layer, characterized in that the adhesive layers comprise a graft copolymer containing ethylene units and units selected from the group consisting of organic acids, derivatives of organic acids and mixtures thereof, wherein the first layer is polyethylene ( i) is a multilayer film, the entire structure of the multilayer film being substantially derived from polyethylene. 2. The structure of claim 1, wherein the organic acid and the organic acid derivative are selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, nadic acid, citraconic acid, itaconic acid, cretonic acid, their anhydrides, their salts metals, their esters, their amides, their imides and mixtures thereof. 3. The structure according to any of the previous paragraphs, where the first layer of polyethylene is oriented only in the longitudinal direction. 4. The structure according to any of the preceding claims, wherein the first layer of polyethylene (i) is formed from at least three layers. 5. A method for producing a multilayer structure according to any one of claims 1 to 4, wherein said method includes the steps of: (a) providing a first polyethylene film, wherein the first polyethylene film is oriented at least in a longitudinal direction; (b) providing a second polyethylene film, wherein the second layer of polyethylene is non-oriented; (c) coextruding (c-1) an ethylene-vinyl alcohol copolymer layer between the first polyethylene film and the second polyethylene film; and (c-2) adhesive layers on both sides of the ethylene-vinyl alcohol copolymer layer; and (d) compressing the first polyethylene film and the second polyethylene film, thereby obtaining a multilayer structure characterized in that the adhesive layers comprise a graft copolymer containing ethylene units and units selected from the group consisting of organic acids, derivatives of organic acids and mixtures thereof wherein the first layer of polyethylene is a multilayer film produced by coextrusion, the entire structure of the multilayer film being substantially derived from polyethylene. 6. The method according to claim 5, comprising the step of extruding a layer of ethylene-vinyl alcohol copolymer at a temperature ranging from 200 to 240, preferably from 210 to 240 and preferably 230°C. 7. The method according to claim 5 or 6, including the step of extruding the adhesive layers at a temperature ranging from 200 to 280, preferably from 220 to 260°C. 8. The method according to any one of claims 5 to 7, comprising the step of extruding layers of polyethylene between the first polyethylene film and adhesive layer and the second polyethylene film and adhesive layer. 9. The method according to any one of claims 5 to 8, wherein the first polyethylene film is a multilayer polyethylene film that is oriented in at least the longitudinal direction, preferably formed from at least three layers. Eurasian Patent Organization, EAPO Russia, 109012, Moscow, Maly Cherkassky lane, 2