Multilayer polyethylene structure

Abstract

The present invention relates to the flexible packaging material, it particularly relates to a multilayered extrusion laminated polyethylene structure which are recyclable. It is desired to provide a flexible multilayered PE laminate which is suitable for packaging even higher volumes while providing desired stiffness and providing improved impact strength without the requirement for increasing the thickness of the multilayered laminate. The present inventors have found that a multilayered laminate having a blown PE film extrusion laminated with a blown PE sealant layer and having a sandwiched PE extrusion layer provides for high stiffness and also has good impact strength.

Description

[0001] MULTILAYER POLYETHYLENE STRUCTURE

[0002] Field of the Invention

[0003] The present invention relates to the flexible packaging material, it particularly relates to a multilayered extrusion laminated polyethylene structure which are recyclable.

[0004] Background of the Invention

[0005] Flexible packaging is used in several applications, particularly in packaging application as they provide a resource efficient way of forming a protective barrier by combining different materials in the layers of the multilayer structures, like in multilayer films.

[0006] Multilayer structures are prepared in different ways depending on the desired properties and demands of the consumer product and materials used in the preparation of the multilayer material, these include extrusion coating process, extrusion lamination or adhesive lamination. In an extrusion coating process, a thin film of molten polymer is extruded through a flat die and pressed onto or into a substrate. As substrates are commonly used paper, paperboard, fabrics, metal foils, plastic films or also another polymer layer. In a lamination process two or more substrate layers are bonded together using a layer between the substrate layer. In an adhesive lamination method, an adhesive layer is needed to bond two or more substrate layers together. Such an adhesive layer act as a glue between the substrate layers. In an extrusion lamination process the molten polymer is extrusion laminated between two substrates, whereby the polymer acts as an adhesive between the layers.

[0007] Different types of multilayered film are developed with structures which must fulfil desired end application such as mechanical, optical and / sealing properties. However, these types of multimaterial multilayer structures, like PET / PE or PET / PP combinations are a challenge for circular economy. Recycling, both mechanical and chemical recycling are very demanding or impossible due to poor quality of the recyclate.

[0008] However, as recycling is becoming more and more important, multilayer materials composed of two or more different materials, are less desirable and not even suitable from recycling point of view.

[0009] Therefore, there is a need to provide multilayer structures being prepared of only one type of polymer or compatible polymers, and still resulting in the product having desired properties. PE / PE laminates are easily recyclable and may fulfil some of the end user performance required to provide desired properties.

[0010] One such example of a recyclable laminate is described in WO 2020 / 136674 A1 (Huhtamaki PPL Limited) which discloses a laminate having a first polyolefin layer and a second polyolefin layer and an intermediate metallized polyolefin film having alcohol-based polymer barrier resin sandwiched between the first and the second polyolefin layer.

[0011] PE / PE laminates having machine direction-oriented polyethylene provides high stiffness equivalent to that of Polyethylene terephthalate (PET). The high stiffness of the MDO-PE (Machine-direction oriented Polyethylene) based laminates are desirable for forming stand-up pouches and finds wide use in preparing sachets and pouches for consumer products.

[0012] It is however found that due to their orientation, the MDO-PE (Machine-direction oriented Polyethylene) have lowered impact strength. When these pouches are used for packaging higher volumes of liquid such as 1 litre or above, the pouches were found to fail the drop test. One way to overcome the drop test failure is to increase the thickness of the laminate, which is counterproductive as this increases the consumption of the plastic and increases cost of the product.

[0013] EP4122705 A1 (Borealis AG, 2023) discloses a PE multilayered film, a laminate and an article comprising this film for packaging, and which provides good mechanical properties such as high stiffness and provides high speed printability without requiring the film to be oriented.

[0014] US2023347629 A1 (Clare Robert, 2023) discloses a multilayer film having PE polymers which is used for packaging purposes for moisture sensitive materials. The multilayered structure has a core layer comprising HDPE and two layers comprising LLDPE which layers are sandwiching the core layer.

[0015] EP2064057 (Borealis Tech, 2017) discloses a film enabling good protection and which provides sufficient mechanical properties.

[0016] US2023364844 (Souza Mayara, 2023) discloses a method of forming a multi-layer packaging laminate for preparing tubes or tube packaging containers. It is desired to provide a flexible multilayered PE laminate which is suitable for packaging even higher volumes while providing desired stiffness and providing improved impact strength without the requirement for increasing the thickness of the multilayered laminate.

[0017] It is also desired to provide a flexible multilayered PE structure which provides for further recycling and is suitable for circular economy.

[0018] Summary of the Invention

[0019] The present inventors have found that a multilayered laminate structure having a blown PE film extrusion laminated with a blown sealant film and having a sandwiched PE extrusion layer provides for high stiffness and also has good impact strength. The multilayered structure includes 0 wt.% adhesive and therefore provides better recyclability. The multilayered laminate structure has quick curing time and improves the production process. The multilayered laminate structure also provides for reducing the blown sealant film thickness while maintaining the laminate thickness. It was also found that when the blown PE film is extrusion laminated with the blown sealant film it provides for a bond strength of 6N / 15mm or more.

[0020] The present inventors have found that when a multilayered laminate structure is formed by extrusion laminating a layer of blown PE film and a layer of extruded PE film and where the so formed multilayered laminate has specific levels of LDPE, LLDPE, mLLDPE, MDPE and HDPE in the laminate structure it provides the laminate with good resilience and impact strength without increasing the thickness of the laminate.

[0021] According to a first aspect, the present invention provides a multilayer structure comprising: i. a blown polyethylene (PE) film layer; ii. a blown PE sealant layer;

[0022] Hi. a core PE layer sandwiched between the blown PE film and the blown PE sealant layer wherein the core PE layer is extrusion laminated between the blown PE film and the blown sealant PE layer; wherein the blown PE film is a multilayered film comprising

[0023] (i) an outer layer comprising LLDPE and MDPE;

[0024] (ii) a middle layer adjacent the outer layer / sandwiched between the outer layer and the inner layer comprising HDPE and MDPE; and,

[0025] (iii) an inner layer opposite the outer layer comprising LLDPE and MDPE. According to another aspect, the present invention provides a process for preparing a multilayer structure, said process comprising the steps of: i. providing a blown PE film; ii. providing a blown sealant layer film;

[0026] Hi. providing a core layer component comprising a PE film iv. extrusion laminating the blown PE film and the blown sealant layer film by extruding the core PE layer between the blown PE film and the blown sealant layer film to produce the multilayer structure. wherein the blown PE film is a multilayered film comprising i. an outer layer comprising LLDPE and MDPE; ii. a middle layer adjacent the outer layer / sandwiched between the outer layer and the inner layer comprising HDPE and MDPE; and,

[0027] Hi. an inner layer opposite the outer layer comprising LLDPE and MDPE.

[0028] According to a third aspect, present invention provides a package preferably for holding a cleaning composition, said package comprising:

[0029] (i) a multilayer structure according to the first aspect where the multilayer structure is sealed to form a package;

[0030] (ii) a cleaning composition.

[0031] Brief Description of the figures

[0032] Figure 1 shows a cross-sectional view of a layer structure of a laminate sheet (1) comprising a non-oriented blown polyethylene film layer (2), extruded polyethylene layer (3), blown sealant layer (4).

[0033] Detailed Description of the Invention

[0034] According to the first aspect provided is a multilayer structure comprising a blown polyethylene (PE) film layer; a blown sealant polyethylene (PE) layer and a core extruded polyethylene (PE) layer.

[0035] "Polyethylene" or PE means a polymer having more than 50% by weight derived from an ethylene monomer. PEs of different densities such as LLDPE, LDPE, MDPE, HDPE are considered the same type or kind of PE as far as the recyclability in mono-material recycling streams is concerned. Preferably at least 90 wt.% of the multilayered structure is made of the polyolefin of the same kind, still preferably at least 95 wt.%, most preferably 100 wt.% of the multilayered structure is made of the polyolefin of the same kind. Polyethylene is defined in the present invention to be a composition of polyethylene homopolymer or polyethylene copolymer with an alpha-olefin comonomer of 4 to 10 C atoms, preferably alpha-olefin comonomer of 4 to 6 C atoms. Polyethylene copolymers are thus polyethylene random copolymers, polyethylene heterophasic copolymers or polyethylene terpolymers with propylene and / or alpha olefin comonomers of 4 to 10 C atoms. The composition optionally contains at most 15 wt.%, preferably at most 10 wt.%, of a plastomer of ethylene with C6to C10 alpha-olefin copolymer, and / or a polyethylene blended with the polypropylene homo- or copolymer.

[0036] The expression homopolymer used in the invention relates to a polyethylene that includes substantially, i e. of at least 97wt.%, preferably of at least 99 wt.%, and most preferably of at least 99.8 wt% of ethylene units. In a preferred embodiment only ethylene units in the polyethylene homopolymer are detectable.

[0037] In polyethylene copolymers a major part of the monomers is ethylene i.e., at least 50 % of the monomers is ethylene. Polyethylene copolymers are non-polar.

[0038] The multilayered structure has 0 wt.% adhesive, particularly those adhesive selected from solvent-free or water-based adhesive, more particularly polyurethane adhesive, acrylic based adhesive, and mixtures thereof.

[0039] The recyclable multilayered structure preferably has not more than 5 wt.% printing related component. Preferably the printing related component includes but is not limited to print ink, print lacquers and mixtures thereof.

[0040] The recyclable multilayered structure preferably has 0 wt.% non-PE polymeric material selected from the group consisting of PET, PVC, PVDC, biodegradable polymers and compostable polymers.

[0041] The recyclable multilayered structure preferably has not more than 5 wt.% barrier material selected from the group consisting of EVOH, polyacrylate, acrylics, PVOH, SiOx, AlxOy, metallization and water-based coating.

[0042] Preferably the multilayered structure has a density less than 0.95 g / cm3. Preferably the blown PE film layer and the blown sealant layer according to the multilayer structure of the present invention is a multilayer film. Preferably the blown film PE film layer and the blown sealant layer are a three-layer film.

[0043] The multilayer structure is characterized by a bond strength of 6N / 15 mm or more where the bond strength is measured using ASTM F904.

[0044] When the core PE layer is extrusion laminated between the blow PE film and the sealant PE layer, the adhesion between the blow PE film layer and the blown sealant layer by the core PE layer which is extrusion laminated provides a bond strength to the multilayer structure which is 6N / 15 mm or more where the bond strength is measured using ASTM F904.

[0045] Preferably the multilayer structure comprises:

[0046] (i) 15 wt.% to 40 wt.% HDPE;

[0047] (ii) 8 wt.% to 16 wt.% LDPE;

[0048] (iii) 15 wt.% to 45 wt.% LLDPE;

[0049] (iv) 18 wt.% to 20 wt.% metallocene PE;

[0050] (v) 5 wt.% to 7 wt.% MDPE; wherein the core PE layer sandwiched between the blown PE film layer and the blown sealant PE layer and wherein the core PE layer is extruded; wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer provides the laminate with a bond strength of 6N / 15 mm or more when measured using ASTM F904.

[0051] Preferably the multilayer structure has a tensile Strength (MD) value ranging from 25 to 30 N / mm2, more preferably 28 N / mm2to 30 N / mm2when measured using ASTM D 882.

[0052] Preferably the multilayer structure has a tensile Strength (CD) value ranging from 15 to 20 N / mm2, more preferably 18 N / mm2to 20 N / mm2when measured using ASTM D 882.

[0053] Preferably the multilayer structure has an elongation (MD) value ranging from 900% to 1000%, more preferably 950 % to 980 % when measured using ASTM D 882.

[0054] Preferably the multilayer structure has an elongation (CD) value ranging from 950% to 1500%, more preferably 1000 N / mm2to 1500 N / mm2when measured using ASTM D 882. Preferably the multilayer structure has a dart impact ranging from 750g to 850g, more preferably 800 N / mm2to 850 N / mm2when measured using ASTM D1709 (Method A).

[0055] Preferably the multilayer structure has a bond strength ranging from 6N / 15mm to 20N / 15mm, more preferably 6 N / 15mm to 15N / 15mm, still preferably 6 N / 15mm to 12 N / 15mm, still more preferably from 6 N / 15mm to 10N / 15mm, further preferably from 6 N / 15mm to 8 N / 15mm, still further preferably 6 N / 15mm to 6.5 N / 15mm when measured using ASTM F904.

[0056] Blown polyethylene (PE) film layer

[0057] According to the first aspect provided is a multilayered structure which comprises a blown polyethylene (PE) film layer.

[0058] The blown polyethylene (PE) film layer is preferably a non-oriented film. The process for preparing a blown film is known to a person skilled in the art. The blown PE film in accordance with the present invention may be prepared by any conventional film extrusion procedure known in the art, e.g., with blown film extrusion. Preferably, the blown PE film layer is a non-oriented multilayered film structure.

[0059] Preferably, the blown PE film layer is a non-oriented multilayered film structure which is formed by blown film process, more preferably by co-extrusion blown film processes. Preferably the blown film having multilayered structure is formed by an extrusion process through an annular die. A bubble is formed by blowing air inside the tube formed by the film, thereby cooling the film. The bubble is collapsed between the rollers after solidification. The blow-up ratio can be in the range of from 1 :1 to 1 :4, preferably 1 : 1 .5 to 1 :3.5.

[0060] The blown PE film according to the first aspect of the present invention is a multilayered film comprising: (i) an outer layer comprising LLDPE and MDPE; (ii) a middle layer adjacent to the outer layer / sandwiched between the outer layer and the inner layer comprising HDPE and MDPE; and, (iii) an inner layer opposite the outer layer comprising LLDPE and MDPE. Preferably the LLDPE in the outer layer of the blown PE film is metallocene LLDPE. Preferably the LLDPE in the inner layer of the blow PE film is metallocene LLDPE.

[0061] Preferably the blown PE film has one or more polyethylene film layers, still preferably from 1 to 7 film layers. The blown PE film is preferably a 3-ply or three-layered film. It may also be 5-ply, or a 7-ply or more blown film. Typically, a three-layer structure is produced on a 3-layer coextrusion line, but it may be appreciated that the co-extruder is a 5- or 7-layer co-extrusion line, especially in case when barrier or tie layers are to be co-extruded. All further layers, present in the blown PE film of the present invention are of PE composition.

[0062] Preferably the blown PE film layer comprises from 30 wt.% to 40 wt.% HDPE, 25 wt.% to 35 wt.% MDPE and from 30 wt.% to 40 wt.% LLDPE, preferably mLLDPE. Preferably 100% of the HDPE present in the blown PE film layer is located in the middle layers of the multilayered blown PE film.

[0063] Preferably the linear low-density polyethylene (LLDPE) has a density ranging from 0.915 g / cm3to 0.925 g / cm3. Preferably the linear low-density PE is a metallocene low density PE (mLLDPE) and has a density ranging from 0.915 g / cm3to 0.925 g / cm3. Preferably the high-density polyethylene (HDPE) has a density equal to or more than 0.941 g / cm3. Preferably the medium density polyethylene (MDPE) has a density ranging from 0.926 g / cm3to 0.941 g / cm3.

[0064] Preferably the blown PE film comprises an outer layer preferably comprising metallocene linear low-density PE (mLLDPE) and medium density PE (MDPE); a middle layer adjacent the outer layer / sandwiched between the outer layer and the inner layer preferably comprising high density PE (HDPE) and medium density PE (MDPE); and an inner layer opposite the outer layer preferably comprising metallocene low linear density PE (mLLDPE) and medium density PE (MDPE). The multilayered blown PE film is preferably co-extruded and preferably has 0 wt.% adhesive.

[0065] Preferably the blown PE film has an outer layer comprising mLLDPE and MDPE. The amount of mLLDPE ranges from 70 wt.% to 80 wt.% by weight of the outer layer of the blown PE film. The amount of MDPE ranges from 20 wt.% to 30 wt.% by weight of the outer layer of the blown PE film.

[0066] Preferably the blown PE film has middle layer comprising HDPE and MDPE. The amount of HDPE ranges from 70 wt.% to 80 wt.% by weight of the middle layer of the blown PE film. The amount of MDPE ranges from 20 wt.% to 30 wt.% by weight of the middle layer of the blown PE film.

[0067] Preferably the blown PE film has an inner layer opposite the outer layer comprising mLLDPE and MDPE. The amount of mLLDPE ranges from 70 wt.% to 80 wt.% by weight of the inner layer of the blown PE film. The amount of MDPE ranges from 20 wt.% to 30 wt.% by weight of the inner layer of the blown PE film. The blown PE film layer preferably has a density ranging from 0.85 g / cc to 0.94 g / cc. Preferably the outer layer of the multilayered blown PE film is printable, preferably surface printable, more preferably reverse printable. Preferably the outer layer of the blown PE film layer is printed. Preferably the printing is by surface printing, more preferably by reverse printing.

[0068] Preferably the blown PE film layer has a thickness ranging from 15 micrometers to 50 micrometers, still preferably from 20 micrometers to 50 micrometers, still preferably from 25 micrometers to 35 micrometers, still more preferably from 25 micrometers to 30 micrometers. Also preferably the blown PE film layer has a thickness ranging from 15 micrometers to 30 micrometers. Preferably the thickness is measured after the extrusion blowing but prior to lamination to form the multilayer structure.

[0069] The blown PE film is preferably prepared as a tri-extruded blown film in the preferred embodiment but could be manufactured by alternative methods which follow the same guidelines of components described herein. The three-layer co-extruded film contributes to the significant strength and toughness characteristics which, when compared with other reinforced laminates, is superior in tear tests, outdoor weathering, tensile strength, and other significant characteristics for polymer products.

[0070] Preferably the blown PE film comprises a high level of polyethylene to facilitate recycling. The blown PE film layer preferably comprises at least 85 wt.% polyethylene by weight of the blown PE film, preferably at least 90 wt.%, still more preferably at least 95 wt.%, further preferably at least 97 wt.%, preferably the amount of the PE by weight of the blown PE film is from 85 wt.% to 100 wt.%. It is highly preferred that the blown PE film layer is substantially free or free of PET, more preferably substantially free or free of polypropylene (PP) and PET.

[0071] Core PE layer

[0072] According to the first aspect of the present invention the multilayered laminate structure includes a core PE layer. The core layer may include one or more additional polyethylene film layer. Preferably the core PE layer comprises at least one film layer of PE. More preferably the core PE layer has a thickness ranging from 12 micrometers to 15 micrometers. Preferably the core PE layer has a basis weight ranging from 3 g / m2to 20 g / m2, preferably from 5 g / m2to 15 g / m2, still more preferably from 10 g / m2to 14 g / m2furthermore preferably from 10.8 g / m2to 13.5 g / m2. The core PE layer preferably comprises low density polyethylene (LDPE). The LDPE preferably is produced by high pressure autoclave process. The LDPE present in the core PE layer is preferably an extrusion coating grade Low density Polyethylene (LDPE). Preferably the extrusion coating grade LDPE specially developed for extrusion coating on different substrates and contains 0 wt.% additives. Preferably a 40 micrometers blown film prepared using with 1 .0 mm die gap and 2.0 BUR from the extrusion grade LDPE, has a melt flow index when measured at 190°C / 2.16 kg using the ASTM D1238 method has a value around 8.5 gm / 10 minutes, a density (at 23°C) measured using ASTM D1505 has a value around 0.917 g / cc, a tensile strength at break (MD / TD) of 15 / 15 MPa (ASTM D882) and an elongation at break (MD / TD) value of 250 / 400% (ASTM D882). Preferably the core PE layer is a non-oriented PE.

[0073] During the process of preparing the multilayer structure according to the present invention the core layer is heated to form a molten extruded polymer layer (core PE layer) which is applied as an adhesive layer between the blown PE film and the sealant layer to form the multilayer (extrusion laminated) structure.

[0074] The multilayer structure according to the present invention is prepared by extrusion lamination.

[0075] Blown PE Sealant layer

[0076] According to the first aspect of the present invention the multilayered laminate structure includes a blown PE sealant film.

[0077] When the blown PE sealant layer is a multilayer film structure it is formed by a co-extrusion process, preferably blown film coextrusion process. Preferably the blown sealant layer is a nonoriented film. Typically, the non-oriented sealant film layer is a blown film or a cast film, preferably a blown film. Preferably the blown sealant layer may include at least one machine- oriented layer.

[0078] Preferably the blown sealant film layer is formed using a blown film apparatus composed of a multi-manifold circular die head having concentric circular orifices. Preferably when the sealant layer is a multilayer film it is formed by coextruding a molten layer through a circular die, and a molten layer on the other or each opposite side of the first layer through additional circular dies concentric with the first circular die. Next, a gas, typically air, is blown through a jet that is concentric with the circular dies, thereby forming a bubble that expands the individual layers. The bubble is collapsed onto itself to form a pair of multilayer films attached at two opposite edges. Usually, the pair of attached multilayer films are then cut apart at one or more edges and separated into a pair of multilayer films that can be rolled up. Alternatively, the sealant film layer may be manufactured using other extrusion processes known in the art, such as a cast film process, wherein melted and plasticized streams of individual layer materials are fed into a coextrusion die, such as a multi-manifold die. Upon emersion from the die, the layers are quenched to form a single multilayer film of polymeric material.

[0079] Preferably the blown sealant film layer may include one (monolayer) or more (multilayered) layers. Preferably the blown sealant layer includes 1 to 7 film layers, still preferably from 1 to 5 film layers. Preferably the blown sealant layer may be 1 -ply / layer, 3-ply / layered or 7-ply film. One or more layers of the blown sealant may be a composition of polyethylene blend with a plastomer. More preferably the blown sealant layer includes 100% PE. Preferably the blown sealant layer has at least three layer, more preferably the sealant layer has only three layers. Preferably the layers of the blown sealant film is co-extruded blown film.

[0080] The thickness of the blown PE sealant film layer is preferably ranging from 20 micrometers to 200 micrometers, still preferably from 40 micrometers to 200 micrometers, preferably in the range of 50 micrometers to 150 micrometers, more preferably in the range of 50 micrometers to 120 micrometers, and still more preferably in the range of 60 micrometers to 100 micrometers. Also, preferably the blown sealant PE layer has a thickness ranging from 20 micrometers to 150 micrometers.

[0081] Preferably the blown PE sealant layer is multilayered comprising:

[0082] (i) an outer layer comprising metallocene PE and LDPE;

[0083] (ii) a middle layer adjacent the outer layer / sandwiched between the outer layer and the inner layer comprising metallocene PE, HDPE and LDPE; and,

[0084] (iii) an inner layer opposite the outer layer comprising LLDPE and LDPE.

[0085] Preferably the blown PE sealant layer is a 3-ply or layered structure. Preferably the blown PE sealant layer has an outer layer comprising metallocene PE and LDPE. The amount of metallocene PE ranges from 90 wt.% to 80 wt.% by weight of the outer layer of the blown sealant film layer. The amount of LDPE ranges from 10 wt.% to 20 wt.% by weight of the outer layer of the blown sealant film layer. Preferably the metallocene PE is a metallocene LLDPE. Commercially metallocene PE is available as Enable™ 2005ME from ExxonMobil Chemical which is an ethylene-1 -hexene copolymer. Preferably the metallocene PE includes an anti-block agent and a slip additive. Preferably the outer layer of the sealant layer is adjacent to the core PE layer, preferably in contact with the core PE extrusion layer. Preferably the blown PE sealant layer has a middle layer comprising HDPE and LDPE. The amount of HDPE ranges from 30 wt.% to 40 wt.% by weight of the inner layer of the blown sealant layer. The amount of LDPE ranges from 10 wt.% to 20 wt.% by weight of the inner layer of the blown sealant layer.

[0086] Preferably the blown PE sealant layer has an inner layer comprising LLDPE and LDPE. More preferably the LLDPE is metallocene LLDPE. The amount of LLDPE ranges from 80 wt.% to 90 wt.% by weight of the inner layer of the sealant layer. Preferably the LLDPE is metallocene LLDPE. The amount of LDPE ranges from 10 wt.% to 20 wt.% by weight of the inner layer of the sealant layer.

[0087] Preferably the polymer composition of the inner layer of the sealant film layer comprises 60 wt.% to 90 wt.% LLDPE and 10 wt.% to 40 wt.% LDPE by weight of the inner layer. The LLDPE is preferably a multi-modal LLDPE, still preferably a bimodal LLDPE, more preferably a bimodal butene LLDPE. The presence of the bimodal LDDPE provides low seal initiation temperature. Preferably the LLDPE is a Commercially available LLDPE includes Polyethylene Anteo™ FK1828 from Borouge. Preferably the LDPE is commercially available from Reliance polymers under the grade name 1020FA20. The LDPE has a density (at 23°C) when measured using ASTM D 792 of 0.92 g / cc.

[0088] Preferably the blown sealant PE film layer has a seal initiation temperature ranging from 95 °C to 110°C. The seal initiation temperature (SIT) is the lowest temperature at which a consistent and acceptable seal is formed. To measure the SIT, gradually increase the temperature of the sealing machine in small increments. At each increment, attempt to seal the material and check the seal strength by using ASTM F2029-08.

[0089] Preferably the blown sealant film layer has a melting temperature ranging from 110°C to 135 °C. The melting temperature was measured using differential scanning calorimetry using ASTM D3418. This method involves heating a small sample of the polymer at a controlled rate and recording the temperature at which it melts. The melting point is represented by the melting peak temperature in the DSC curve.

[0090] Preferably the blown sealant PE film layer has a thickness ranging from 20 micrometers to 150 micrometers, more preferably from 30 micrometers to 150 micrometers, still more preferably from 50 micrometers to 100 micrometers, (as measured after extrusion blowing but before any lamination). Preferably the sealant PE film comprises a high level of polyethylene to facilitate recycling. The sealant PE film layer preferably comprises at least 85 wt.% polyethylene by weight of the sealant PE film, preferably at least 90 wt.%, still more preferably at least 95 wt.%, further preferably at least 97 wt.%, preferably the amount of the PE by weight of the sealant PE film is from 85 wt.% to 100 wt.%. It is highly preferred that the sealant PE film layer is substantially free or free of PET, more preferably substantially free or free of polypropylene (PP) and PET.

[0091] Optional ingredients

[0092] Optionally, additional additives such as fillers, slip agents, anti-block agents, antioxidants, chill roll release agents and polymer process aid can be incorporated into the melt blends and dry blends of the laminate structure. Typically, the amount of additive is not more than 2 % by weight, preferably not more than 1 % by weight and especially preferably not more than 0.5 % by weight.

[0093] The blown PE film layer is preferably the print layer is free from additives. Preferably the blown sealant PE film layer includes slip agents as an additive for reducing the coefficient of friction and improving the ease of extrusion lamination. Preferably the amount of slip additive is present in an amount ranging from 1 .2 wt.% to 1 .25 wt.% by weight of the blown sealant PE film layer.

[0094] Multilayered structure

[0095] According to the first aspect of the present invention the multilayered structure comprises (i) a blown polyethylene (PE) film layer; (ii) a blown PE sealant layer; (iii) a core PE layer sandwiched between the blown PE film and the blown sealant PE layer; wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer.

[0096] The multilayer structure according to the first aspect of the present invention preferably comprises

[0097] (i) 15 wt.% to 40 wt.% HDPE;

[0098] (ii) 8 wt.% to 16 wt.% LDPE;

[0099] (iii) 15 wt.% to 45 wt.% LLDPE;

[0100] (iv) 18 wt.% to 20 wt.% mLLDPE;

[0101] (v) 5 wt.% to 7 wt.% MDPE. where the multilayer structure comprises,

[0102] (i) a layer of blown PE film;

[0103] (ii) a blown PE sealant layer; (iii) a core PE layer sandwiched between the blown PE film layer and the blown sealant PE layer and wherein the core PE layer is extruded. wherein the core PE layer sandwiched between the blown PE film layer and the blown sealant PE layer and wherein the core PE layer is extruded; wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer provides the laminate with a bond strength of 6N / 15 mm or more.

[0104] Preferably the laminate structure may further include one or more of a moisture barrier layer, an oxygen barrier layer, and mixtures thereof. These may be in the form of a coextruded layer in the blown PE layer or the blown sealant layer or both. These may preferably be provided in the form of coating. These includes but are not limited to layer of EVOH, aluminium oxide, an inorganic vapor deposition layer, aluminium deposition, SiOx or natural polymer coating, for example nanocellulose.

[0105] The multilayered structure according to the first aspect of the present invention was found to have immediate curing.

[0106] Preferably blown PE sealant layer and the blown PE layer are in contact with the core PE layer, wherein the core PE layer is extrusion laminated between the blown PE film and the blown PE sealant layer. When the blown PE film and the blown sealant PE film are both multilayered then the inner layer of the blown PE film and the outer layer of the blown PE sealant film are adjacent to the core PE layer, preferably in contact with the core PE layer.

[0107] Lamination according to the present invention is made by combining the blown PE film layer and the blown sealant PE film layer by extrusion lamination. Preferably the multilayer structure according to the invention does not include an adhesive layer. The multilayer structure according to the present invention is substantially free or free of polyurethane-based adhesive, acrylic acid based adhesive or any other adhesive known to a person skilled in the art.

[0108] The multilayer structure according to the present invention preferably has an overall thickness ranging from 40 micrometers to 200 micrometers, still preferably from 47 micrometers to 150 micrometers, furthermore preferably from 80 micrometers to 180 micrometers. One suitable way to assess the thickness is by SEM, in addition to various optical techniques.

[0109] Preferably the multilayer structure according to the invention comprises a high level of polyethylene to facilitate recycling. The multilayer structure preferably comprises at least 85 wt.% polyethylene by weight of the sealant PE film, preferably at least 90 wt.%, still more preferably at least 95 wt.%, further preferably at least 97 wt.%, preferably the amount of the PE by weight of the multilayer structure is from 85 wt.% to 100 wt.%. It is highly preferred that the multilayer structure is substantially free or free of PET, more preferably substantially free or free of polypropylene (PP) and PET.

[0110] Process for preparing the multilayer structure

[0111] According to another aspect, the present invention provides a process for preparing a multilayer structure, said process comprising the steps of: i. providing a blown PE film; ii providing a blown PE sealant layer film;

[0112] Hi providing a core PE layer iv extrusion laminating the blown PE film and the blown PE sealant layer film by extruding the core PE layer between the blown PE film and the blown PE sealant layer film to produce the multilayer structure. wherein the blown PE film is a multilayered film comprising:

[0113] (i) an outer layer comprising LLDPE and MDPE,

[0114] (ii) a middle layer adjacent the outer layer / sandwiched between the outer layer and the inner layer comprising HDPE and MDPE; and,

[0115] (iii) an inner layer opposite the outer layer comprising LLDPE and MDPE; preferably wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer and the extruded lamination provides the laminate with a bond strength of 6N / 15 mm or more.

[0116] Preferably the LLDPE in the outer layer is metallocene LLDPE. Preferably the LLDPE is an inner layer opposite the outer layer is metallocene LLDPE.

[0117] According to present invention the polyethylene mono-material multilayer structure is produced by extrusion lamination. The extrusion lamination process resembles the extrusion coating process, but in extrusion lamination the core PE layer is extruded between two substrates, i.e., between the blown PE film and the blown PE sealant layer. Thereby, the blown PE film and the blown PE sealant film layer, as herein defined are provided as substrates to the extrusion lamination process. The core PE layer, as herein defined is then extrusion laminated between the blown PE film and the blown PE sealant layer. As indicated in the present invention, blown PE film and the blown sealant layer may comprise one or more film layers. The core PE layer preferably comprises a single layer film. In the extrusion lamination process according to the present invention, a molten layer of core PE layer is extruded through a T-Shape die and applied as an adhesive layer between the blown PE film and the blown PE sealant layer to form a laminated structure.

[0118] The line speed in the extrusion lamination process is typically from 50 m / min to 1000 m / min, preferably from 75 m / min to 650 m / min, and especially from 100 m / min to 500 m / min.

[0119] Preferably when the core PE layer has been extrusion laminated between the blown PE film and the blown PE sealant film layer, the multilayer structure is then passed to a nip formed by a chill roll and a pressure roll. The chill roll is typically water-cooled and has the objective of cooling the extruded structure to a suitable temperature. Typically, the surface temperature of the chill roll can be from about 15°C to about 60°C. The temperature of the polymer melt is typically between 240 to 330°C, preferably from 250°C to 315°C. Preferably the blown PE film and / or the blown PE sealant layer may be subjected to pre-corona treatment and preferably the core PE layer may preferably be subjected to ozone treatment.

[0120] Preferably the multilayer structure may include additional optional film layers. Preferably when the multilayer structure has additional film layers, such film layers are composed of PE composition. The PE composition includes but is not limited to LDPE, LLDPE, mLLDPE, MDPE, HDPE and mixtures thereof.

[0121] Package

[0122] According to another aspect, the present invention provides a polyethylene mono-material multilayer structure for use as packaging material, in particular as a packaging material for packaging consumer products. Particularly for preparing standup pouch which has good stiffness and good impact strength. These pouches further have good barrier properties.

[0123] Preferably the invention provides a package comprising a multilayer structure according to the first aspect of the present invention. Preferably the invention provides a package obtainable according to the second aspect of the invention.

[0124] According to another aspect, the present invention provides a container comprising the multilayer structure of the present invention. Preferably the container is a flexible package suitable for holding a cleaning composition, more preferably a laundry composition. The term flexible package includes bag, pouches, gusset pouch, wicket pouch, standup pouch, pillow bags and pillow pouches. Preferably the flexible package according to the present invention includes an opening feature. The term “opening feature” is defined as an aid to opening the flexible package that includes a weaking of a selected opening path on the laminate.

[0125] The flexible package comprising the multilayer structure according to the present invention, is capable of holding relatively large amounts of the consumer product. Preferably the flexible package is suitable for holding 0.25 Kg to 5 Kg, still more preferably from 0.5 Kg to 4 Kg, still preferably from 0.75 Kg to 3 Kg, further preferably from 1 Kg to 3 Kg and alternatively from 1 Kg to 2 Kg. Preferably the flexible package is suitable for holding a volume of 0.25 L to 5 L, still more preferably from 0.5 L to 4 L, still preferably from 0.75 L to 3 L, further preferably from 1 L to 3 L and alternatively from 1 L to 2 L. The consumer product is preferably a liquid laundry composition or a solid laundry composition.

[0126] The flexible package comprising the multilayer structure according to the present invention preferably has a total surface area from 1600 cm2to 2600 cm2.

[0127] Examples

[0128] Example 1 : A multilayer structure according to the present invention

[0129] A multilayer structure according to the present invention comprising a blown film PE, extruded PE core layer and a blown PE sealant layer was prepared having a structure which included

[0130] Blown PE 25 micrometers / Extruded PE 15micrometers / blown PE sealant layer 100 micrometers

[0131] Blown Film

[0132] The blown film had a thickness of 25 micrometers and was a multilayered film comprising 3 layered structure.

[0133] The formed blown PE film having a thickness of 25 micrometers had the following structure as provided in table 1. All the weight % are in terms of the weight % of the total weight of the layer.

[0134] • An outer layer of the blown film has 70 wt.% of LLDPE (Exceed™ 1327MA from ExxonMobil Chemical Company) and 30 wt.% of MDPE (Enable™ 4009MC from ExxonMobil Chemical Company). The outer layer of the blown film may be printed.

[0135] • The middle layer of the blown film has 70 wt.% HDPE (Elite™ AT 6900 from Dow Chemical Company) and 30 wt.% of MDPE (Enable™ 4009MC from ExxonMobil Chemical Company) The inner layer of the blown film has 70 wt.% LLDPE (Exceed™ 1327MA from ExxonMobil Chemical Company) and 30 wt.% MDPE (Enable™ 4009MC from ExxonMobil Chemical Company)

[0136] Table 1

[0137] Core Laver

[0138] Core layer includes a monolayer of the LDPE (Grade 1070LA17 from Reliance Polymers). The core layer has a thickness of 12 to 15 micrometers and a basis weight of around 10.8 g / m2to 13.5 g / m2.

[0139] Sealant layer

[0140] The sealant film had a thickness of 100 micrometers and was a multilayered structure comprising 3 layers which was formed by a co-extrusion blown film process. The sealant layer was a non-oriented 3 layered film.

[0141] The co-extruded sealant layer film having a thickness of 100 micrometers had the following structure as provided in table 2. All the weight % are in terms of the weight % of the total weight of the layer of the sealant film layer.

[0142] • The outer layer of the sealant film had 90 wt.% of metallocene PE (Enable™ 2005ME from ExxonMobil Chemical Company) and 10 wt.% of LDPE (Grade 1020FA20 from Reliance Polymers)

[0143] • The middle layer of the sealant film has 50 wt.% of metallocene PE (Enable™ 2005ME from ExxonMobil Chemical Company), 40 wt.% of HDPE (F46003 from Reliance polymers) and 10 wt.% of LDPE (Grade 1020FA20 from Reliance Polymers)

[0144] • The inner layer of the sealant film has 90 wt.% LLDPE (Polyethylene Anteo™ FK1828 from Borouge) and 10 wt.% LDPE (Grade 1020FA20 from Reliance Polymers) Table 2

[0145] Extrusion lamination to form the multilayer structure

[0146] The blown PE film layer and the sealant film layer were extrusion laminated by extruding the core layer to a thickness of 15 micrometers (basis weight 13.5 g / m2) between the blown PE film layer and the blown PE sealant film layer. Extruded core PE layer act as an adhesive / binding component. One surface of the core PE layer is adjacent the inner layer of the blown PE film layer and the other opposite surface of the core PE layer is adjacent the outer layer of the blown sealant film layer.

[0147] Extrusion lamination was carried out on Rajoo Lamex-R machine have specification to process 725 mm to 1300 mm width substrate. The melt extruder, which excrete polymer melt for lamination has different zones like feed, compression, metering, adapter and die. Machine is fitted with unwinder, rewinder and out feed tension ranging from 90N to 140N. To ensure proper cooling of the layers after lamination a water-cooled chiller roller was used in which the temperature is maintained between 18°C to 25°C.

[0148] The prepared laminate was then analyzed for various functional properties as provided in table 3 below along with the observed parameters which were recorded and provided in table 3 below.

[0149] Table 3: Functional Properties of the multilayer structure according to the invention

[0150] The data provided in table 3 shows that the multilayer structure according to the present invention having a blown film layer, core PE extruded layer and the sealant layer has overall good performance. It has a good tensile strength which indicates that laminate have good load bearing capacity without undergoing deformation. The laminate has good elongation properties which ensures its suitability in packaging application. It also has high dart impact values which makes the laminate impact resistance.

Claims

CLAIMS1. A multilayer structure comprising:(i) a blown polyethylene (PE) film layer;(ii) a blown PE sealant PE layer;(iii) a core PE layer sandwiched between the blown PE film and the blown sealant PE layer; wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer; wherein the blown PE film is a multilayered film comprising(i) an outer layer comprising LLDPE and MDPE;(ii) a middle layer adjacent the outer layer / sandwiched between the outer layer and the inner layer comprising HDPE and MDPE; and,(iii) an inner layer opposite the outer layer comprising LLDPE and MDPE.

2. A structure according to claim 1 wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer and provides the laminate with a bond strength of 6N / 15 mm or more.

3. A structure according to claim 1 or 2 wherein the blown PE film is non-oriented.

4. A structure according to any one of the preceding claims wherein the LLDPE in the outer layer of the blown PE film is metallocene LLDPE.

5. A structure according to any one of the preceding claims wherein LLDPE in the inner layer of the blown PE film is metallocene LLDPE.

6. A structure according to any one of the claims 1 to 5 wherein the outer layer of the multilayered blown PE film is printable, preferably surface printable, more preferably reverse printed.

7. A structure according to any one of the preceding claims wherein the blown PE sealant film is monolayer film or multilayered film, preferably the blown PE sealant film is unoriented.

8. A structure according to any one of the preceding claims wherein the blown PE sealant layer is multilayered comprising:(i) an outer layer comprising metallocene PE and LDPE;(ii) a middle layer adjacent the outer layer comprising metallocene PE, HDPE and LDPE; and,(iii) an inner layer opposite the outer layer comprising LLDPE and LDPE.

9. A structure according to any one of the preceding claims wherein the blown PE sealant layer has a melting temperature less than 150°C when measured using a differential scanning calorimetry using ASTM D3418 and preferably has a density ranging from 0.85 g / cc to 0.94 g / cc.

10. A structure according to any one of the preceding claims wherein the blown PE film layer has a density ranging from 0.85 g / cc to 0.94 g / cc.

11. A structure according to any one of the preceding claims wherein the blown PE film layer has a thickness ranging from 20 micrometers to 50 micrometers, more preferably from 25 micrometers to 35 micrometers, still more preferably from 25 micrometers to 30 micrometers, (when measured after the extrusion blowing but before any lamination)12. A structure according to any one of the preceding claims wherein the blown sealant PE layer has a thickness ranging from 20 micrometers to 150 micrometers13. A structure according to any one of the preceding claims wherein the multilayer structure comprises:(i) 15 wt.% to 40 wt.% HDPE;(ii) 8 wt.% to 16 wt.% LDPE;(iii) 15 wt.% to 45 wt.% LLDPE;(iv) 18 wt.% to 20 wt.% metallocene PE;(v) 5 wt.% to 7 wt.% MDPE; wherein the core PE layer sandwiched between the blown PE film layer and the blown sealant PE layer and wherein the core PE layer is extruded; wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer provides the laminate with a bond strength of 6N / 15 mm or more.

14. A process for preparing the multilayer structure according to any one of the preceding claims wherein the process comprises the steps of:(i) providing a blown PE film;(ii) providing a blown PE sealant layer film;(iii) providing a core PE layer;(iv) extrusion laminating the blown PE film and the blown PE sealant layer film by extruding the core PE layer between the blown PE film and the blown PE sealant layer film to produce the multilayer structure; wherein the blown PE film is a multilayered film comprising:(i) an outer layer comprising LLDPE and MDPE;(ii) a middle layer adjacent the outer layer / sandwiched between the outer layer and the inner layer comprising HDPE and MDPE; and,(iii) an inner layer opposite the outer layer comprising LLDPE and MDPE. preferably wherein the core PE layer is extrusion laminated between the blown PE film and the sealant PE layer and the extruded lamination provides the laminate with a bond strength of 6N / 15 mm or more.

15. A package comprising a multilayered structure according to any one of the preceding claims 1 to 13 or obtainable according to the process of claim 14.

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