Multilayer film

Abstract

The present invention relates to a multilayer film comprising: A) a first outer layer (O1) and a second outer layer (O2) wherein the first outer layer (O1) and / or the second outer layer (O2) comprises A1) a bimodal ethylene terpolymer having a density as determined according to ISO 1183 of 910 to 930 kg / m3 and an MFR2 of 0.5 to 10 g / 10 min as measured according to ISO 1133 (190 DEG C, 2.16 kg) comprising at least a C4-C12 alpha-olefin comonomer, and A2) a first multimodal ethylene copolymer (CP1) having a density as determined according to ISO 1183 of 910 to 930 kg / m3 and an MFR2 of 0.5 to 10 g / 10 min and comprising at least a C4-C12 alpha-olefin comonomer, a multimodal ethylene copolymer (CP2) having a density of 930 to 950 kg / m3 as determined according to ISO 1183 and an MFR5 of 0.5 to 10 g / 10 min as measured according to ISO 1133 (190 DEG C, 5.00 kg) comprising at least a first C4-C12 alpha-olefin comonomer, B) a core layer (C) sandwiched between a first outer layer (O1) and a second outer layer (O2) wherein the core layer (C) comprises B1) recycled LDPE having a density of 910 to 940 kg / m3 as determined according to ISO 1183 and an MFR2 of 0.1 to 10 g / 10 min as measured according to ISO 1133 (190 DEG C, 2.16 kg), and B2) a second multimodal ethylene copolymer (CP2) having a density of 910 to 940 kg / m3 as determined according to ISO A multimodal ethylene copolymer (CP1) having a density of from 930 to 950 kg / m3 as determined according to ISO 1183 and an MFR5 of from 0.5 to 10 g / 10 min as measured according to ISO 1133 (190 DEG C, 5.00 kg) comprising at least a first C4-C12 alpha-olefin comonomer wherein the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) is trimodal comprising:-a first ethylene homopolymer in an amount of from 10 to 30 wt%, more preferably from 15 to 25 wt%; -a second ethylene homopolymer in an amount of 15 to 35 wt%, more preferably 20 to 30 wt%, having an MFR2 of at least 50 g / 10 min higher than the MFR2 of component a), measured according to ISO 1133 (190 DEG C, 2.16 kg); and-a third ethylene copolymer having at least a first C4 to C12 alpha-olefin comonomer in an amount of 35 to 75 wt%, more preferably 45 to 65 wt%; wherein these amounts are based on the total weight of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2).

Description

Technical Field

[0001] The present invention relates to a multilayer film comprising a core layer (C), a first outer layer (O1) and a second outer layer (O2) sandwiching the core layer (C). The present invention also relates to a heavy duty transport sack (HDSS) comprising the multilayer film. Background Art

[0002] There has long been a need to provide packaging materials with the desired properties depending on the final application, such as mechanical properties in terms of tensile modulus, tear resistance, dart impact resistance and toughness, or processability in terms of bubble stability during blown film extrusion, for example. In addition to the demands on packaging material performance, environmental issues have arisen in recent years, which have led packaging material producers to focus on sustainability aspects.

[0003] Multilayer films are often used in industrial packaging, where each layer can serve a different purpose to ensure the desired functional properties. Produced by coextrusion, such films offer design flexibility, reflecting the needs of the packaging industry. However, designing multilayer films with enhanced sustainability remains challenging.

[0004] WO 2006 / 039603 A1 discloses a multilayer film suitable for applications such as pouches, comprising at least three layers; two of which are outer layers sandwiching a core layer. Each outer layer independently comprises an LLDPE component, while the core layer comprises a multimodal polyethylene component with a specific design. However, it does not focus on increasing the sustainability of the film, but rather on improving the performance of the film through the design of each layer.

[0005] WO 2020 / 219378 A1 also discloses a multilayer film structure suitable for forming into a stretch hood, with an emphasis on increasing the tear resistance of the film in the longitudinal direction. The multilayer film comprises a first outer layer, a first inner layer, a core layer, a second inner layer and a second outer layer in a given order. Although the document mentioned discloses reducing the use of raw materials by introducing less raw materials, it does not mention the use of recycled materials in the multilayer structure.

[0006] Therefore, the object of the present invention is to provide a packaging solution that focuses on increasing sustainability while ensuring the requirements established in the industry, such as mechanical properties and processability of the film. In particular, the object of the present invention is to provide a multilayer film suitable for heavy duty shipping sacks (HDSS) that has ideal mechanical properties in terms of dart impact resistance, tensile modulus and tear resistance and that increases sustainability through the successful use of recycled content in the film structure. Summary of the invention

[0007] The present invention relates to a multilayer film comprising:

[0008] A) a first outer layer (O1) and a second outer layer (O2), wherein the first outer layer (O1) and / or the second outer layer (O2) comprises

[0009] A1) a bimodal ethylene terpolymer having a molecular weight of 910 to 930 kg / m 3 and a MFR of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 , containing at least C 4 -C 12 α-olefin comonomer, and

[0010] A2) a first multimodal ethylene copolymer (CP1) having a molecular weight of 930 to 950 kg / m 3 The density is 0.5 to 10 g / 10 according to ISO 1133 (190°C, 5.00 kg).

[0011] min MFR 5 , including at least the first C 4 -C 12 2 containing olefin comonomers,

[0012] B) a core layer (C) sandwiched between a first outer layer (O1) and a second outer layer (O2), wherein the core layer (C)

[0013] include

[0014] B1) Recycled LDPE having a molecular weight of 910 to 940 kg / m 3 and a density of 0.1 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 ,as well as

[0015] B2) a second multimodal ethylene copolymer (CP2) having a molecular weight of 930 to 950 kg / m 3 The density is 0.5 to 10 g / 10 according to ISO 1133 (190°C, 5.00 kg).

[0016] min MFR 5 , including at least the first C 4 -C 12 α-Olefin Comonomer

[0017] wherein the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) is trimodal comprising:

[0018] - a first ethylene homopolymer in an amount of 10 to 30 wt%, more preferably 15 to 25 wt%;

[0019] - a second ethylene homopolymer in an amount of from 20 to 30 wt%, having an MFR of 1.5-1.0 (190° C., 2.16 kg) as measured according to ISO 1133 relative to component a) 2 MFR at least 50g / 10min higher 2 ;as well as

[0020] - 35 to 75 wt%, more preferably 45 to 65 wt% of a third ethylene copolymer having at least a first C 4 -C 12 α-olefin comonomers;

[0021] Therein these amounts are based on the total weight of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2).

[0022] The present invention also relates to a heavy duty shipping sack (HDSS) comprising the multilayer film according to the present invention. DETAILED DESCRIPTION

[0023] definition

[0024] All terms used herein should be understood as having the ordinary meaning known to those skilled in the art. For greater accuracy, the following terms will have the meanings described below.

[0025] As used herein, the term "multilayer film" refers to a film having a layered structure, ie, comprising more than one layer.

[0026] The term "multimodal" as used herein refers to a polymer having two or more fractions that differ from each other in at least one property, such as weight average molecular weight or comonomer content. The molecular weight distribution curve (a plot of polymer weight fraction versus molecular weight) of such a multimodal polymer exhibits two or more maxima, depending on the morphology, or such a curve is significantly broadened compared to the curve for a single fraction. When a polymer contains two different fractions, it is called "bimodal", similarly, when it contains three different fractions, it is called "trimodal".

[0027] As used herein, the term "ethylene copolymer" refers to an ethylene polymer containing ethylene and at least one comonomer. On the other hand, the term "ethylene terpolymer" refers to an ethylene polymer containing two different comonomers.

[0028] The term "recycled LDPE" as used herein refers to a recycled polymer material comprising at least 80 wt%, preferably at least 85 wt%, more preferably at least 90 wt%, and most preferably at least 95 wt% of low density polyethylene based on the total weight of the recycled low density polyethylene. Therefore, the recycled LDPE may also comprise up to 20 wt%, preferably up to 15 wt%, more preferably up to 10 wt%, and even more preferably up to 5 wt% of other (preferably recycled) polymer components, such as LLDPE, MDPE, HDPE, based on the total weight of the recycled low density polyethylene.

[0029] Recycled polymeric materials are polymeric materials recovered from post-consumer waste (PCR) and / or industrial waste. Post-consumer waste refers to items that have completed at least their first cycle of use (or life cycle), i.e. items that have served their first purpose, while industrial waste refers to manufacturing waste that does not normally reach the consumer.

[0030] Multilayer film

[0031] The multilayer film according to the present invention comprises:

[0032] A) a first outer layer (O1) and a second outer layer (O2), wherein the first outer layer (O1) and / or the second outer layer (O2) comprises

[0033] A1) a bimodal ethylene terpolymer having a molecular weight of 910 to 930 kg / m 3 and a MFR of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 , containing at least C 4 -C 12 α-olefin comonomer, and

[0034] A2) a first multimodal ethylene copolymer (CP1) having a molecular weight of 930 to 950 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 5.00 kg) 5 , including at least the first C 4 -C 12 α-olefin comonomers,

[0035] B) a core layer (C) sandwiched between a first outer layer (O1) and a second outer layer (O2), wherein the core layer (C) comprises

[0036] B1) Recycled LDPE having a molecular weight of 910 to 940 kg / m 3and a density of 0.1 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 ,as well as

[0037] B2) a second multimodal ethylene copolymer (CP2) having a molecular weight of 930 to 950 kg / m 3 The density is 0.5 to 10 g / 10 according to ISO 1133 (190°C, 5.00 kg).

[0038] min MFR 5 , including at least the first C 4 -C 12 2 containing olefin comonomer

[0039] wherein the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) is trimodal comprising:

[0040] - a first ethylene homopolymer in an amount of 10 to 30 wt%, more preferably 15 to 25 wt%;

[0041] - an amount of 15 to 35 wt%, more preferably 20 to 30 wt% of a second ethylene homopolymer having an MFR of 1.0% to component a) measured according to ISO 1133 (190°C, 2.16 kg) 2 At least 50g / 10

[0042] min MFR 2 ;as well as

[0043] - 35 to 75 wt%, more preferably 45 to 65 wt% of a third ethylene copolymer having at least a first C 4 -C 12 α-olefin comonomers;

[0044] Therein these amounts are based on the total weight of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2).

[0045] The outer layers (O1, O2) of the multilayer film according to the invention sandwich the core layer (C), which means that the core layer (C) is covered on both sides by the first outer layer (O1) and the second outer layer (O2).

[0046] The multilayer film according to the invention can be produced by coextrusion of the layers. In such a method, the following steps are preferably followed:

[0047] a) feeding the components of the polymer blend constituting each layer to a blown film line,

[0048] b) Coextrusion of multilayer films on a blown film line.

[0049] When the blend is added in step a), additives such as antioxidants, processing stabilizers, pigments, UV stabilizers and other additives known in the art may be added.

[0050] It is preferred that the blend for the first outer layer (O1) and / or the second outer layer (O2) comprises up to 10 wt%, more preferably up to 7 wt% of additives based on the total weight of the mixture constituting the first outer layer (O1) and / or the second outer layer (O2).

[0051] It is also preferred that the blend for the core layer (C) comprises up to 10 wt%, more preferably up to 7 wt% of additives based on the total weight of the blend constituting the core layer (C).

[0052] The coextrusion mentioned in step b) above is well known in the art and is carried out by extruding at least two polymer melt streams in a simultaneous manner through a multi-channel tubular, annular or circular die to form a tube, which is blown, expanded and / or cooled with air (or a combination of gases) to form a film.

[0053] The blown coextrusion of step b) as described above is preferably carried out at a temperature of 160 to 240°C, and the subsequent cooling is preferably carried out by blowing a gas (eg air) at 10 to 50°C to provide a frost line height of 1 to 8 times the die diameter.

[0054] The blow up ratio (BUR) should generally be in the range of 1.2 to 6, preferably 1.5 to 4.

[0055] Preferably, the multilayer film according to the present invention has a dart drop impact resistance (DDI) measured according to ASTM D1709 on 110 μm blown film of 130 to 500 g, more preferably 150 to 400 g, most preferably 150 to 350 g.

[0056] Preferably, the multilayer film according to the present invention has a relative tear resistance in the machine direction (MD) of 20 to 250 N / mm, more preferably 25 to 150 N / mm, measured on a 110 μm blown film according to ISO 6383 / 2 and / or a relative tear resistance in the transverse direction (TD) of 200 to 450 N / mm, more preferably 270 to 400 N / mm, measured on a 110 μm blown film according to ISO 6383 / 2.

[0057] It is also preferred that the multilayer film according to the invention has a relative tear resistance in the machine direction (MD) of 350 to 580 MPa, more preferably 400 to 550 MPa, measured on a 110 μm blown film according to ISO 527-3 and / or a relative tear resistance in the transverse direction (TD) of 400 to 700 MPa, more preferably 500 to 650 MPa, measured on a 110 μm blown film according to ISO 527-3.

[0058] The multilayer film according to the present invention preferably has a thickness of 10 to 500 μm, more preferably 50 to 350 μm, most preferably 70 to 150 μm.

[0059] The multilayer film according to the present invention preferably comprises 10 to 70 wt%, more preferably 20 to 60 wt%, most preferably 25 to 50 wt% of recycled LDPE based on the total weight of the polymer blend used to make the multilayer film.

[0060] Outer layer (O1 and O2)

[0061] The first and second outer layers (O1, O2) of the present invention sandwich the core layer (C), regardless of whether any one or both of them are the outermost layers. However, in an embodiment of the present invention, the outer layer may be the outermost layer.

[0062] The first outer layer (O1) and / or the second outer layer (O2) according to the present invention comprises:

[0063] A1) a bimodal ethylene terpolymer having a molecular weight of 910 to 930 kg / m 3 and a MFR of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 , containing at least C 4 -C 12 α-olefin comonomer, and

[0064] A2) a first multimodal ethylene copolymer (CP1) having a molecular weight of 930 to 950 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 5.00 kg) 5 , including at least the first C 4 -C 12 2. Contains olefin comonomer.

[0065] Preferably, the thickness of the first outer layer (O1) and / or the second outer layer (O2) is 2 to 100 μm, more preferably 5 to 80 μm, most preferably 10 to 50 μm. It is particularly preferred that the first outer layer (O1) and / or the second outer layer (O2) have the same thickness.

[0066] It is preferred that the first outer layer (O1) and the second outer layer (O2) have the same composition, ie are made of the same polymer with the same recipe.

[0067] Bimodal ethylene terpolymer

[0068] The bimodal ethylene terpolymer of the first outer layer (O1) and / or the second outer layer (O2) preferably comprises 1-butene as C 4 -C 12 α-olefin comonomer.

[0069] It is preferred that the bimodal ethylene terpolymer of the first outer layer (O1) and / or the second outer layer (O2) further comprises a second comonomer, namely C 6 -C 20 an alpha-olefin comonomer, preferably 1-hexene.Most preferably the bimodal ethylene terpolymer comprises 1-butene and 1-hexene as comonomers, ie it is a terpolymer of ethylene / 1-butene / 1-hexene.

[0070] The bimodal ethylene terpolymer of the first outer layer (O1) and / or the second outer layer (O2) preferably has a density of 912 to 925 kg / m 3 , more preferably 915 to 920 kg / m 3 .

[0071] The bimodal ethylene terpolymer of the first outer layer (O1) and / or the second outer layer (O2) preferably has an MFR measured according to ISO 1133 (190°C, 2.16 kg) of 0.8 to 5.0 g / 10 min, more preferably 1.0 to 3.0 g / 10 min, most preferably 1.2 to 2.0 g / 10 min 2 .

[0072] The bimodal ethylene terpolymer may contain additives such as antioxidants, processing stabilizers, pigments, UV stabilizers and other additives known in the art.

[0073] Preferably, in the first outer layer (O1) and / or the second outer layer (O2), the bimodal ethylene terpolymer is present in an amount of 10-50 wt%, more preferably 20 to 45 wt%, most preferably 25 to 38 wt%, based on the total weight of the first outer layer (O1) and / or the second outer layer (O2).

[0074] Commercially available bimodal ethylene terpolymers are also preferably used in the multilayer films according to the invention, such as Anteo from Borealis or Borouge having the properties required herein. TM , especially Anteo TM FK1820.

[0075] First and second multimodal ethylene copolymers (CP1, CP2)

[0076] According to the present invention the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) according to the present invention is trimodal comprising:

[0077] - a first ethylene homopolymer in an amount of 10 to 30 wt%, more preferably 15 to 25 wt%;

[0078] - 15 to 35 wt%, more preferably 20 to 30 wt% of a second ethylene homopolymer having an MFR greater than component a) 2 MFR at least 50g / 10min higher 2 ;as well as

[0079] - 35 to 75 wt%, more preferably 45 to 65 wt% of a third ethylene copolymer having at least a first C 4 -C 12 α-olefin comonomers;

[0080] Therein these amounts are based on the total weight of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2).

[0081] It is preferred that the first ethylene homopolymer part of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) has an MFR measured according to ISO 1133 (190°C, 2.16 kg) of 50 to 400 g / 10 min, more preferably of 100 to 300 g / 10 min, most preferably of 150 to 250 g / 10 min. 2 .

[0082] It is preferred that the second ethylene homopolymer part of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) has an MFR, measured according to ISO 1133 (190°C, 2.16 kg), of 100 to 900 g / 10 min, more preferably of 300 to 800 g / 10 min, most preferably of 400 to 750 g / 10 min. 2 .

[0083] The first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) preferably comprises 1-butene as first C 4 -C 12 2 as olefin comonomer.

[0084] It is preferred that the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) further comprises a second comonomer, i.e. C 6 -C20 Most preferably, the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) comprises 1-butene and 1-hexene as comonomers, i.e. is a terpolymer of ethylene / 1-butene / 1-hexene.

[0085] The first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) preferably has a density measured according to ISO 1183 of 935 to 948 kg / m 3 , more preferably 938 to 945 kg / m 3 .

[0086] The first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) preferably has an MFR measured according to ISO 1133 (190°C, 2.16 kg) of 0.1 to 3.0 g / 10 min, more preferably of 0.2 to 1.5 g / 10 min, most preferably of 0.25 to 0.80 g / 10 min. 2 .

[0087] The first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) preferably has an MFR measured according to ISO 1133 (190°C, 5.00 kg) of 0.8 to 5.0 g / 10 min, more preferably of 1.0 to 3.0 g / 10 min, most preferably of 1.2 to 2.0 g / 10 min. 5 .

[0088] The first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) preferably has an MFR measured according to ISO 1133 (190°C, 21.6 kg) of 5 to 100 g / 10 min, more preferably of 10 to 80 g / 10 min, most preferably of 20 to 60 g / 10 min 21 .

[0089] It is preferred that the first multimodal ethylene copolymer (CP1) and the second multimodal ethylene copolymer (CP2) have the same composition, ie are made of the same polymers having the same recipe.

[0090] In a most preferred embodiment the first multimodal ethylene copolymer (CP1) and the second multimodal ethylene copolymer (CP2) have the same composition, i.e. are trimodal terpolymers comprising the following fractions:

[0091] - a first ethylene homopolymer in an amount of 10 to 30 wt%, more preferably 15 to 25 wt%;

[0092] - 15 to 35 wt%, more preferably 20 to 30 wt% of a second ethylene homopolymer having an MFR greater than component a)2 MFR at least 50g / 10min higher 2 ;as well as

[0093] - a third ethylene terpolymer having 1-hexene and 1-butene as comonomers in an amount of 35 to 75 wt%, more preferably 45 to 65 wt%;

[0094] Therein these amounts are based on the total weight of the trimodal terpolymer.

[0095] The first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) may comprise additives such as antioxidants, processing stabilizers, pigments, UV stabilizers and other additives known in the art.

[0096] Preferably, in the first outer layer (O1) and / or the second outer layer (O2), the first ethylene copolymer (CP1) is present in an amount of 50-90 wt%, more preferably 55 to 80 wt%, most preferably 62 to 75 wt%, based on the total weight of the first outer layer (O1) and / or the second outer layer (O2).

[0097] Process for the first and / or second multimodal ethylene copolymer (CP1 and / or CP2)

[0098] The first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) may be produced according to the process described below. Preferably, both the first multimodal ethylene copolymer (CP1) and the second multimodal ethylene copolymer (CP2) are trimodal and produced according to the process described below.

[0099] The process for the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) comprises the following steps:

[0100] a) polymerizing ethylene in a first polymerization step in the presence of a Ziegler-Natta polymerization catalyst to produce a first ethylene homopolymer;

[0101] b) polymerizing ethylene in the presence of a first ethylene homopolymer in a second polymerization step to produce a first ethylene polymer mixture comprising the first ethylene homopolymer and a second ethylene homopolymer; and

[0102] c) in the third polymerization step, in the presence of the first ethylene polymer mixture, ethylene and at least a first C 4 -C 12 The α-olefin comonomer is copolymerized to produce a second ethylene polymer mixture comprising the first ethylene polymer mixture and the third ethylene copolymer.

[0103] In a preferred embodiment, a prepolymerization is carried out before the polymerization as described in step a). The purpose of the prepolymerization is to polymerize a small amount of polymer onto the catalyst at low temperature and / or low monomer concentration. By prepolymerization, the performance of the catalyst in slurry can be improved and / or the properties of the final polymer can be changed. The prepolymerization step is preferably carried out in slurry, for example in a loop reactor. The prepolymerization is then preferably carried out in an inert diluent, which is typically a hydrocarbon diluent, such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc., or a mixture thereof. Preferably, the diluent is a low boiling hydrocarbon having 1 to 4 carbon atoms or a mixture of such hydrocarbons.

[0104] The temperature in the prepolymerization step is generally from 0 to 90° C., preferably from 20 to 80° C., more preferably from 55 to 75° C. The pressure is not critical and is generally from 1 to 150 bar, preferably from 40 to 80 bar.

[0105] The amount of monomer in the prepolymerization step is generally 0.1 to 1000 grams of monomer per gram of solid catalyst component. As known to those skilled in the art, the catalyst particles recovered from the continuous prepolymerization reactor do not all contain the same amount of prepolymer. On the contrary, each particle has its own characteristic amount, which depends on the residence time of the particle in the prepolymerization reactor. Because some particles stay in the reactor for a relatively long time, and some stay for a relatively short time, the amount of the prepolymer on different particles is also different, and some single particles may contain the amount of the prepolymer beyond the above range. However, the average amount of prepolymer on the catalyst is usually within the above range.

[0106] As is known in the art, the molecular weight of the prepolymer can be controlled by hydrogen.In addition, antistatic additives can be used to prevent the particles from sticking to each other or to the reactor walls, as disclosed in WO-A-96 / 19503 and WO-A-96 / 32420.

[0107] If a prepolymerization step is used, it is preferred that the prepolymer is an ethylene homopolymer. Any prepolymer component is considered part of the first ethylene homopolymer, and thus the weight percent, melt flow rate (MFR), density, etc. of the first ethylene homopolymer are determined on this basis.

[0108] When there is a prepolymerization step, the catalyst components are preferably all introduced into the prepolymerization step (separately or together). However, when the solid catalyst component and the cocatalyst can be fed separately, only a portion of the cocatalyst may be introduced into the prepolymerization stage, while the remainder is introduced into the subsequent polymerization stage. Moreover, in this case, it is necessary to introduce the cocatalyst into the prepolymerization stage in order to obtain a sufficient polymerization reaction therein.

[0109] Typically, the amounts of hydrogen and comonomer are adjusted so that the presence of the prepolymer has no effect on the properties of the final multimodal polymer. In particular, it is preferred that the prepolymer has a melt flow rate (MFR) greater than the MFR of the final polymer, but less than the MFR of the polymer produced in the first polymerization stage (i.e. the ethylene homopolymer). It is further preferred that the density of the prepolymer is greater than the density of the final polymer. Suitably, the density is about equal to or greater than the density of the polymer produced in the first polymerization stage. Further, typically the amount of prepolymer is no more than about 5 wt% of the multimodal ethylene polymer.

[0110] The first polymerization step a) is generally operated at a temperature of 20 to 150° C., preferably 50 to 110° C., more preferably 60 to 105° C. The polymerization can be carried out in slurry, gas phase or solution. In the first polymerization step a), a first ethylene homopolymer is produced. The first ethylene homopolymer has an MFR measured according to ISO 1133 (190° C., 2.16 kg) of preferably 50 to 400 g / 10 min, more preferably 100 to 300 g / 10 min, most preferably 150 to 250 g / 10 min. 2 and 955 to 980 kg / m 3 density.

[0111] The catalyst can be transferred to the first polymerization step a) by any means known in the art. Therefore, the catalyst can be suspended in a diluent and kept as a uniform slurry. It is particularly preferred to use an oil with a viscosity of 20 to 1500 mPa.s as a diluent, as disclosed in WO-A-2006 / 063771. The catalyst can also be mixed with a viscous mixture of grease and oil, and the resulting paste can be fed to the first polymerization step a). In addition, the catalyst can be allowed to settle, and the catalyst slurry obtained in part can be introduced into the first polymerization step a) in a manner disclosed in, for example, EP-A-428054. In a preferred embodiment, when the first polymerization step a) is preceded by a prepolymerization step, the mixture taken out from the prepolymerization step is introduced into the first polymerization step a).

[0112] Into the first polymerization step a) ethylene, optionally an inert diluent and optionally hydrogen are introduced. Hydrogen and α-olefin are introduced in such amounts that the melt flow rate MFR of the first ethylene homopolymer is 2 and density are at the desired values.

[0113] The polymerization of the first polymerization step a) can be carried out in slurry. The polymer particles formed in the polymerization are then suspended in a fluid hydrocarbon together with the catalyst fragmented and dispersed in the particles. The slurry is stirred to transfer the reactants from the fluid to the particles.

[0114] The polymerization is usually carried out in an inert diluent, which is usually a hydrocarbon diluent, such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc., or a mixture thereof. Preferably, the diluent is a low boiling hydrocarbon having 1 to 4 carbon atoms or a mixture of such hydrocarbons. A particularly preferred diluent is propane, which may contain small amounts of methane, ethane and / or butane.

[0115] The ethylene content of the fluid phase of the slurry can be 1 to about 50 mol%, preferably about 1.5 to about 20 mol%, and especially about 2 to about 15 mol%. The benefit of having a high ethylene concentration is that the productivity of the catalyst is increased, but the disadvantage is that more ethylene needs to be recovered compared to the case of lower concentrations.

[0116] The slurry polymerization can be carried out in any known reactor for slurry polymerization. Such reactors include continuous stirred tank reactors and loop reactors. Particularly preferably, the polymerization is carried out in a loop reactor. In such a reactor, the slurry is circulated at high speed along a closed pipeline by using a circulation pump. Loop reactors are well known in the art, and examples are given, for example, in US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186 and US-A-5391654.

[0117] If the first ethylene homopolymer is produced at a ratio of alpha-olefin to ethylene of not more than about 400 mol / kmol, for example not more than 300 mol / kmol, it is usually advantageous to carry out the slurry polymerization above the critical temperature and pressure of the fluid mixture. Such an operation is described in US-A-5391654.

[0118] When the first polymerization step a) is carried out in slurry form, it is carried out at a temperature ranging from 50 to 115° C., preferably from 70 to 110° C., in particular from 80 to 105° C. The pressure in the first polymerization step a) is from 1 to 300 bar, preferably from 40 to 100 bar.

[0119] The amount of hydrogen is adjusted based on the desired melt flow rate of the first ethylene homopolymer and it depends on the specific catalyst used. For many commonly used Ziegler-Natta catalysts, the molar ratio of hydrogen to ethylene is, for example, 10 to 2000 mol / kmol, preferably 20 to 1000 mol / kmol, and especially 40 to 800 mol / kmol.

[0120] The polymerization of the first polymerization step a) can be carried out in the gas phase. A preferred embodiment of a gas phase polymerization reactor is a fluidized bed reactor. In the reactor, the polymer particles formed in the polymerization are suspended in the gas moving upward. The gas is introduced into the bottom of the reactor. The upwardly moving gas passes through the fluidized bed, wherein a portion of the gas reacts in the presence of a catalyst, and the unreacted gas is discharged from the top of the reactor. The gas is then compressed and cooled to remove the heat of polymerization. In order to increase the cooling capacity, it is sometimes necessary to cool the recycle gas to a temperature at which a portion of the gas condenses. After cooling, the recycle gas is introduced into the bottom of the reactor. Fluidized bed polymerization reactors are particularly disclosed in US-A-4994534, US-A-4588790, EP-A-699213, EP-A-628343, FI-A-921632, FI-A-935856, US-A-4877587, FI-A-933073 and EP-A-75049.

[0121] According to a preferred embodiment of the present invention, the polymerization of the first polymerization step a) is carried out in slurry. Furthermore, suitably, the polymerization is carried out at a temperature exceeding the critical temperature of the fluid mixture and at a pressure exceeding the critical pressure of the fluid mixture.

[0122] The first polymerisation step a) is preferably carried out as a slurry polymerisation in a liquid diluent at a temperature of 75 to 100°C, such as 80 to 95°C and a pressure of 30 to 100 bar, such as 40 to 80 bar, such as 50 to 80 bar.

[0123] The polymerisation rate in the first polymerisation step a) is appropriately controlled to obtain the desired amount of the first ethylene homopolymer in the second ethylene polymer mixture.

[0124] In the first polymerisation step a), the molar ratio of hydrogen to ethylene is suitably from 50 to 350 mol / kmol, preferably from 75 to 325 mol / kmol.

[0125] The polymerization rate is suitably controlled by adjusting the ethylene concentration in the first polymerization step a).When the first polymerization step a) is carried out as a slurry polymerization in a loop reactor, the mole fraction of ethylene in the reaction mixture is suitably, for example, 0.5 to 10 mol%, preferably 1 to 8 mol%.

[0126] The amount of the first polymer (including prepolymer in case a prepolymerization is carried out before the first polymerization step a)) in the multimodal ethylene copolymer is preferably from 10 to 30 wt%, more preferably from 15 to 25 wt%, based on the total weight of the first multimodal ethylene copolymer (CP1) and / or the multimodal ethylene copolymer (CP2).

[0127] In the second polymerisation step b) a second ethylene homopolymer is produced in the presence of the first ethylene homopolymer.

[0128] The second polymerization step b) is usually operated at a temperature of 20 to 150° C., preferably 50 to 110° C., more preferably 60 to 100° C. The polymerization can be carried out in slurry, gas phase or solution. In the second polymerization step, a second ethylene homopolymer is produced in the presence of the first ethylene homopolymer. The first ethylene homopolymer and the second ethylene homopolymer together form a first ethylene polymer mixture. The first ethylene polymer mixture has a molecular weight of 955 to 980 kg / m 3 and a density of 100 to 700, more preferably 200 to 600, most preferably 300 to 400 g / min, as determined according to ISO 1133 (190° C., 2.16 kg). 2 .

[0129] The first ethylene homopolymer is transferred from the first polymerization step a) to the second polymerization step b) by using any method known to the person skilled in the art. If the first polymerization step a) is carried out as a slurry polymerization in a loop reactor, it is advantageous to transfer the slurry from the first polymerization step a) to the second polymerization step b) by the pressure difference between the first polymerization step a) and the second polymerization step b). Thus, the catalyst used in the first polymerization step a) is also transferred to the second step b).

[0130] Into the second polymerization step b) ethylene, optionally an inert diluent and optionally hydrogen are introduced. The hydrogen is introduced in such an amount that the melt flow rate MFR of the first ethylene polymer mixture is 2 and density are within the expected values.

[0131] The polymerization of the second polymerization step b) can be carried out in slurry in the same manner as the first polymerization step a) discussed above.

[0132] The amount of hydrogen in the second polymerization is adjusted based on the desired melt flow rate of the first ethylene polymer mixture, and it depends on the specific catalyst used. For many commonly used Ziegler-Natta catalysts, the molar ratio of hydrogen to ethylene is, for example, 100 to 2000 mol / kmol, preferably 200 to 1000 mol / kmol, and particularly 250 to 800 mol / kmol.

[0133] The polymerization of the second polymerization step b) may be carried out also in gas phase in the same manner as the first polymerization step a) discussed above. Preferably, as mentioned above, the second polymerization step b) is carried out in slurry phase.

[0134] In the second polymerization step b), the molar ratio of hydrogen to ethylene is suitably from 200 to 700 mol / kmol, preferably from 300 to 650 mol / kmol, particularly preferably from 450 to 600 mol / kmol.

[0135] Furthermore, suitably, the polymerisation is carried out at a temperature exceeding the critical temperature of the fluid mixture and at a pressure exceeding the critical pressure of the fluid mixture.

[0136] The polymerization rate in the second polymerization step b) is suitably controlled to obtain a desired amount of the second ethylene homopolymer in the second ethylene polymer mixture. Preferably, the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) of the present invention comprises the second ethylene polymer in an amount of 15 to 35 wt%, more preferably 20 to 30 wt%, based on the total weight of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2).

[0137] The polymerization rate is suitably controlled by adjusting the ethylene concentration in the second polymerization step b). When the second polymerization step is carried out as a slurry polymerization in a loop reactor, the mole fraction of ethylene in the reaction mixture is suitably from 2 to 10 mol%, preferably from 3 to 8 mol%. Thus, the mole fraction of ethylene (in %) in the reaction mixture of the second polymerization step b) may be higher than the mole fraction of ethylene (in %) in the reaction mixture of the first polymerization step a).

[0138] Ideally, the difference in MFR between the first homopolymer and the second homopolymer is as high as possible. 2 than the MFR of the first ethylene homopolymer 2 It is preferred when it is at least 50 g / 10 min higher.

[0139] When the first ethylene homopolymer part of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) has an MFR, measured according to ISO 1133 (190°C, 2.16 kg), of 100 to 900 g / 10 min, more preferably of 300 to 800 g / 10 min, most preferably of 400 to 750 g / 10 min 2 , is preferred.

[0140] In the third polymerisation step c) a second ethylene polymer mixture is formed comprising the first ethylene polymer mixture and the third ethylene copolymer.

[0141] Ethylene, at least one α-olefin having 4 to 12 carbon atoms, hydrogen and optionally an inert diluent are introduced into a third polymerization step c) together with the first ethylene polymer mixture from the second polymerization step b) and the catalyst. The polymerization in the third polymerization step c) is preferably carried out at a temperature in the range of 50 to 100° C., preferably 60 to 100° C., in particular 70 to 95° C. The pressure in the third polymerization step c) is, for example, 1 to 300 bar, preferably 5 to 100 bar.

[0142] The polymerization in the third polymerization step c) can be carried out in slurry.The polymerization can then be carried out along the lines of the first and second polymerization steps as described above.

[0143] The amount of hydrogen in the third polymerization step c) is adjusted to achieve the desired melt flow rate of the second ethylene polymer mixture. The molar ratio of hydrogen to ethylene depends on the specific catalyst used. For many commonly used Ziegler-Natta catalysts, the molar ratio of hydrogen to ethylene is, for example, 0 to 50 mol / kmol, preferably 3 to 35 mol / kmol.

[0144] In addition, the amount of the first alpha hydrocarbon olefin having 4 to 12 carbon atoms is adjusted to achieve the target density. The ratio of the alpha hydrocarbon olefin (which may be the sum of the alpha hydrocarbon olefins) to ethylene depends on the type of catalyst and the type of the alpha hydrocarbon olefin. The ratio is typically, for example, 100 to 1000 mol / kmol, preferably 150 to 800 mol / kmol. If more than one alpha hydrocarbon olefin is used, the ratio of the alpha hydrocarbon olefin to ethylene is the ratio of the sum of all alpha hydrocarbon olefins to ethylene.

[0145] The alpha hydrocarbon olefin is preferably an alpha hydrocarbon olefin of 4 to 8 carbon atoms or a mixture thereof. In particular, 1-butene, 1-hexene and 1-octene and mixtures thereof are preferred alpha hydrocarbon olefins, and 1-butene is particularly preferred.

[0146] As previously mentioned, it is preferred if the third polymer comprises at least two, ideally two, comonomers. 6 -C 20 0 olefins, are preferred, more preferably 1-hexene. Thus, preferably these are 1-butene and 1-hexene. It is also preferred if the higher alpha olefin comonomer is present in excess relative to the lower alpha hydrocarbon olefin comonomer. For example, if 1-butene and 1-hexene are used in the third polymer, preferably at least 60 wt% of 1-hexene and no more than 40 wt% of 1-butene, such as 70 to 90 wt% of 1-hexene and 10 to 30 wt% of 1-butene are present in the third ethylene copolymer, based on the total weight of comonomers present in the third ethylene copolymer. Thus, preferably, the third copolymer contains 70 to 90 wt% of higher alpha olefins and 10 to 30 wt% of lower alpha olefins based on the total weight of comonomers present in the third ethylene copolymer.

[0147] The polymerization in the third polymerization step can and preferably is carried out in gas phase.In the gas phase polymerization using Ziegler Natta catalyst, hydrogen is usually added in such an amount that the ratio of hydrogen to ethylene is, for example, 3 to 100 mol / kmol, preferably 4 to 50 mol / kmol, to obtain the desired melt index of the second ethylene polymer mixture.The amount of alpha olefins with 4 to 12 carbon atoms is regulated to reach the target density of the second ethylene polymer mixture.The ratio of alpha hydrocarbon olefin to ethylene is generally 100 to 1000 mol / kmol, preferably 150 to 800 mol / kmol, further preferably 150 to 300 mol / kmol.If more than one alpha hydrocarbon olefin is used, the ratio of alpha hydrocarbon olefin to ethylene is the ratio of the sum of all alpha hydrocarbon olefins to ethylene.

[0148] The gas phase reactor is preferably a vertical fluidized bed reactor. In the reactor, the polymer particles formed in the polymerization are suspended in the gas moving upward. The gas is introduced into the bottom of the reactor. The gas moving upward passes through the fluidized bed, wherein a portion of the gas reacts in the presence of a catalyst, and the unreacted gas is discharged from the top of the reactor. The gas is then compressed and cooled to remove the heat of polymerization. In order to increase the cooling capacity, it is sometimes necessary to cool the recycle gas to a temperature at which a portion of the gas condenses. After cooling, the recycle gas is introduced into the bottom of the reactor. Fluidized bed polymerization reactors are particularly disclosed in US-A-4994534, US-A-4588790, EP-A-699213, EP-A-628343, FI-A-921632, FI-A-935856, US-A-4877587, FI-A-933073 and EP-A-75049.

[0149] When the second polymerization step b) is carried out in slurry and the third polymerization step c) is carried out in gas phase, the polymer is suitably transferred from the second polymerization step b) to the third polymerization step c) as described in EP-A-1415999. The procedure described in paragraphs

[0037] to

[0048] of EP-A-1415999 provides a cost-effective method for product transfer.

[0150] The conditions in the third polymerization step c) are adjusted so that the second ethylene polymer mixture has a mass fraction of 930 to 950 kg / m 3 , more preferably 935 to 948 kg / m 3 , most preferably 938 to 945 kg / m 3 and a density of 0.5 to 10 g / 10 min, preferably 0.8 to 5.0 g / 10 min, more preferably 1.0 to 3.0 g / 10 min, most preferably 1.2 to 2.0 g / 10 min, measured according to ISO 1183 (190° C., 5.00 kg) 5Preferably the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) is identical to the second ethylene polymer mixture.

[0151] Suitably control the polymerization rate in the third polymerization step c) to obtain the third ethylene copolymer of the desired amount in the second ethylene polymer mixture. Preferably, the second ethylene polymer mixture contains 35 to 75wt%, more preferably 45 to 65wt% of the third ethylene copolymer based on the gross weight of the second ethylene polymer mixture. Suitably control the polymerization rate by adjusting the ethylene concentration in the third polymerization step c). When the third polymerization step c) is carried out in the gas phase, the mole fraction of ethylene in the reactor gas is suitably 3 to 50 mole%, preferably 5 to 15 mole%.

[0152] In addition to ethylene, comonomers and hydrogen, the gas also includes an inert gas. The inert gas can be any gas that is inert under the reaction conditions, such as a saturated hydrocarbon having 1 to 5 carbon atoms, nitrogen or a mixture of the above compounds. Suitable hydrocarbons having 1 to 5 carbon atoms are methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane and mixtures thereof.

[0153] Post-reaction treatment

[0154] When the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) has been withdrawn from the polymerization reactor, it is subjected to a process step for removing residual hydrocarbons from the polymer. Such processes are well known in the art and may comprise a decompression step, a purification step, a stripping step, an extraction step, etc. Combinations of different steps are also possible.

[0155] According to a preferred method, part of the hydrocarbons are removed from the polymer powder by reducing the pressure. The powder is then contacted with steam at a temperature of 90 to 110°C for 10 minutes to 3 hours. Thereafter, the powder is purged with an inert gas such as nitrogen at a temperature of 20 to 80°C for 1 to 60 minutes.

[0156] According to another preferred method, the polymer powder is subjected to decompression as described above. Thereafter, it is purged with an inert gas such as nitrogen at a temperature of 50 to 90° C. for 20 minutes to 5 hours. The inert gas may contain 0.0001 to 5% by weight, preferably 0.001 to 1% by weight, of a component for deactivating the catalyst contained in the polymer, such as steam.

[0157] The purge step is preferably carried out continuously in a fixed moving bed. The polymer moves downward in plug flow and the purge gas introduced into the bottom of the bed flows upward.

[0158] Suitable processes for removing hydrocarbons from polymers are disclosed in WO-A-02 / 088194, EP-A-683176, EP-A-372239, EP-A-47077 and GB-A-1272778.

[0159] catalyst

[0160] The polymerization is carried out in the presence of a Ziegler-Natta olefin polymerization catalyst. Ziegler-Natta catalysts are useful because they can produce polymers within a range of molecular weights and other desired properties at high productivity. The Ziegler-Natta catalyst used in the present invention is preferably supported on an external support.

[0161] Suitable Ziegler-Natta catalysts preferably contain a magnesium compound, an aluminum compound and a titanium compound supported on a particulate support.

[0162] The particle supports commonly used in Ziegler-Natta catalysts include inorganic oxide supports, such as silica, alumina, titania, silica-alumina and silica-titania, or MgCl2-based supports. The catalyst used in the present invention is supported on an inorganic oxide support. Most preferably, the Ziegler-Natta catalyst used in the present invention is supported on silica.

[0163] The average particle size of the silica support is generally in the range of 10 to 100 μm. However, it has been shown that particular advantages can be obtained if the average particle size of the support is in the range of 15 to 30 μm, preferably 18 to 25 μm. Alternatively, the support may have an average particle size of 30 to 80 μm, preferably 30 to 50 μm. Examples of suitable support materials are ES747JR, produced and sold by Ineos Silicas (formerly Crossfield), and SP9-491, produced and sold by Grace.

[0164] The magnesium compound is the reaction product of a dialkylmagnesium and an alcohol. The alcohol is a linear or branched aliphatic monohydric alcohol. Preferably, the alcohol has 6 to 16 carbon atoms. Branched alcohols are particularly preferred, 2-ethyl-1-hexanol being an example of a preferred alcohol. The dialkylmagnesium can be any compound in which magnesium is bonded to two identical or different alkyl groups. Butyl-octylmagnesium is an example of a preferred dialkylmagnesium.

[0165] The aluminum compound is a chlorine-containing aluminum alkyl. Particularly preferred compounds are aluminum alkyl dichlorides, aluminum dialkyl chlorides and aluminum alkyl sesquichlorides.

[0166] The transition metal is preferably titanium. The titanium compound is a halogen-containing titanium compound, preferably a chlorine-containing titanium compound. A particularly preferred titanium compound is titanium tetrachloride.

[0167] The catalyst can be prepared by sequentially contacting the support with the above compounds as described in EP-A-688794 or WO-A-99 / 51646. Alternatively, it can be prepared by first preparing a solution from the components and then contacting the solution with the support as described in WO-A-01 / 55230.

[0168] Ziegler Natta catalysts are used together with an activator, which is also referred to as a co-catalyst. Suitable activators are metal alkyl compounds, typically Group 13 metal alkyl compounds, particularly alkylaluminum compounds. They include trialkylaluminum compounds, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum and tri-n-octylaluminum. Alkylaluminum compounds may also include alkylaluminum halides, such as ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquichloride, dimethylaluminum chloride, etc., and alkylaluminum oxide compounds, such as methylaluminumoxane, hexaisobutylaluminumoxane and tetraisobutylaluminumoxane, and other alkylaluminum compounds, such as isoprenylaluminium. Particularly preferred co-catalysts are trialkylaluminums, of which triethylaluminum, trimethylaluminum and triisobutylaluminum are particularly preferred.

[0169] The amount of activator depends on the specific catalyst and activator. Typically, triethylaluminum is used in such an amount that the molar ratio of aluminum to transition metal (such as Al / Ti) is, for example, 1 to 1000, preferably 3 to 100, particularly about 5 to about 30 mol / mol.

[0170] Core layer (C)

[0171] The core layer (C) according to the present invention comprises:

[0172] B1) Recycled LDPE having a molecular weight of 910 to 940 kg / m 3 and a density of 0.1 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 , and B2) a second multimodal ethylene copolymer (CP2) having a molecular weight of 930 to 950 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 5.00 kg) 5 ,

[0173] Contains at least the first C 4 -C 12 α-olefin comonomer.

[0174] Preferably, the second multimodal ethylene copolymer (CP2) has the same composition as the first multimodal ethylene copolymer (CP1 ) as described above.

[0175] The core layer (C) preferably comprises 30 to 90 wt%, more preferably 45 to 80 wt% of recycled LDPE and 5 to 70 wt%, most preferably 7 to 55 wt% of the second multimodal ethylene copolymer (CP2), based on the total weight of the core layer (C).

[0176] It is preferred that the core layer (C) has a thickness of 5 to 120 μm, more preferably 10 to 90 μm, most preferably 15 to 50 μm.

[0177] Recycled LDPE

[0178] The recycled LDPE preferably has a molecular weight of 915 to 935 kg / m 3 , more preferably 920 to 930 kg / m 3 density.

[0179] Preferably, the recycled LDPE has an MFR measured according to ISO 1133 (190°C, 2.16 kg) of 0.2 to 5.0 g / 10 min, more preferably 0.25 to 1.0 g / 10 min, most preferably 0.3 to 0.8 g / 10 min. 2 .

[0180] The recycled LDPE preferably has a melting point (second melt) determined according to ISO 11357 in the range of 100 to 140°C, preferably 105 to 130°C, more preferably 108 to 125°C.

[0181] As recycled LDPE, the products NAV 101 and / or CWT100LG offered by Ecoplast and Borealis can be used. It is particularly preferred that the recycled LDPE is NAV101.

[0182] High-density polyethylene

[0183] In one embodiment, the core layer (C) may additionally comprise a multimodal high density polyethylene, preferably in an amount of 20 to 60 wt%, more preferably 25 to 50 wt%, most preferably 30 to 45 wt%, based on the total weight of the core layer. Most preferably, the high density polyethylene is bimodal. The high density polyethylene present in this layer enhances mechanical properties, such as stiffness and creep resistance.

[0184] The high density polyethylene preferably has a density of 945 to 970 kg / m 3 , more preferably 950 to 965 kg / m 3 density.

[0185] The high density polyethylene preferably has an MFR measured according to ISO 1133 (190°C, 2.16 kg) of 0.1 to 5.0 g / 10 min, more preferably 0.2 to 2.0 g / 10 min, most preferably 0.4 to 1.5 g / 10 min. 2 .

[0186] The high density polyethylene may contain additives such as antioxidants, processing stabilizers, pigments, UV stabilizers and other additives known in the art.

[0187] Subsurface (S1 and S2)

[0188] The multilayer film according to the present invention preferably further comprises a first sub-skin layer (S1) and a second sub-skin layer (S2), which are respectively disposed between the core layer (C) and the first outer layer (O1) and the second outer layer (O2). In other words, it is preferred that both sides of the core layer (C) are covered with sub-skin layers (S1 and S2).

[0189] Preferably, the first sub-layer (S1) and / or the second sub-layer (S2) comprises:

[0190] a) recycled LDPE having a molecular weight of 910 to 940 kg / m 3 and a density of 0.1 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 ,as well as

[0191] b) a second multimodal ethylene copolymer (CP2) having a molecular weight of 930 to 950 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 5.00 kg) 5 ,

[0192] It contains at least the first C 4 -C 12 α-olefin comonomer.

[0193] The recycled LDPE contained in the first sub-layer (S1) and / or the second sub-layer (S2) preferably has the same composition as the recycled LDPE of the core layer (C). Therefore, all descriptions about the recycled LDPE given above under "core layer (C)" are also preferably applicable to the recycled LDPE of the sub-layers (S1, S2). More preferably, the first sub-layer (S1) and / or the second sub-layer (S2) contains 10 to 60 wt%, more preferably 20 to 50 wt%, most preferably 30 to 40 wt% of recycled LDPE based on the total weight of the first sub-layer (S1) and / or the second sub-layer (S2).

[0194] The second multimodal ethylene copolymer (CP2) comprised in the first sub-layer (S1) and / or the second sub-layer (S2) preferably has the same composition as the second multimodal ethylene copolymer (CP2) of the core layer (C). Hence, all descriptions concerning the second multimodal ethylene copolymer (CP2) given above under "core layer (C)" preferably also apply to the second multimodal ethylene copolymer (CP2) of the sub-layers (S1, S2). More preferably the first sub-layer (S1) and / or the second sub-layer (S2) comprises 20 to 80 wt%, more preferably 30 to 70 wt%, most preferably 40 to 65 wt% of the second multimodal ethylene copolymer (CP2), based on the total weight of the first sub-layer (S1) and / or the second sub-layer (S2).

[0195] It is preferred that the thickness of the first sub-layer (S1) and / or the second sub-layer (S2) is 5 to 100 μm, more preferably 10 to 50 μm, most preferably 15 to 30 μm. It is therefore particularly preferred that the first sub-layer (S1) and the second sub-layer (S2) have the same thickness.

[0196] It is preferred that the blend used for the first sub-layer (S1) and / or the second sub-layer (S2) contains up to 10 wt%, more preferably up to 7 wt% of additives based on the total weight of the blend constituting the first sub-layer (S1) and / or the second sub-layer (S2).

[0197] Most preferably, the first sub-layer (S1) and the second sub-layer (S2) have the same composition, ie comprise the same polymer with the same formulation.

[0198] Heavy duty transport bag

[0199] The present invention further relates to a heavy duty shipping sack (HDSS) comprising a multilayer film as described herein. Preferably, the HDSS comprises at least 70 wt%, more preferably at least 85 wt%, most preferably at least 95 wt% of the multilayer film according to the present invention. Most preferably, the heavy duty shipping sack (HDSS) consists of the multilayer film as described herein, i.e. is made of the multilayer film according to the present invention.

[0200] Example

[0201] A. Test Method

[0202] Melt flow rate

[0203] The melt flow rate (MFR) is measured according to ISO 1133 and is expressed in g / 10 min. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR of polyethylene is measured at 190°C with a load of 2.16 kg (MFR 2 )、5.00kg(MFR 5 ) or 21.6kg(MFR 21 ).

[0204] In the case of the terpolymer (TP1) according to the invention, wherein the terpolymer is produced in a loop-loop gas phase reactor arrangement as given in the Examples section, the MFR of the second loop section is 2 (190℃) can be calculated according to the following formula:

[0205]

[0206] in

[0207] w(A) is the weight fraction of the first annular portion (A), expressed in [wt %],

[0208] w(B) is the weight fraction of the second annular portion (B), expressed in [wt %],

[0209] MFR(C) is the melt flow rate MFR of the polymer produced in the second loop (C) which is the combination of the first loop section (A) and the second loop section (B) 2 (190°C), in [g / 10min] (it is measured),

[0210] MFR(A) is the melt flow rate MFR of the first loop section (A) 2 (190℃), in [g / 10min],

[0211] MFR(B) is the melt flow rate MFR of the second loop section (B) 2 (190℃), measured in [g / 10min].

[0212] density

[0213] The density of the polymer is measured according to ISO 1183-1:2019 (Method A) on compression molded test specimens prepared according to EN ISO 1872-2 (February 2007) and is expressed in kg / m 3.

[0214] Dart impact resistance

[0215] Dart drop impact resistance (DDI) was measured according to ASTM D1709 "Method A" on films having the indicated thickness and produced as described in "Examples" below (blown films with a thickness of 110 μm).

[0216] Tensile modulus

[0217] The tensile modulus in the machine direction and transverse direction (MD and TD, respectively) was determined according to ISO 527-3 on blown films having a thickness of 110 μm at a crosshead speed of 1 mm / min.

[0218] Relative tear resistance (by Elmendorf tear measurement (N / mm))

[0219] The tear strength or tear resistance is measured using the ISO 6383 / 2 method. The force required to propagate a tear on a film sample is measured using a pendulum apparatus. The pendulum swings along an arc under gravity, tearing the sample from a pre-cut slit. One side of the specimen is fixed by the pendulum and the other side is fixed by a fixing fixture. The tear strength or tear resistance is the force required to tear the sample. The relative tear resistance (N / mm) can then be calculated by dividing the tear resistance by the thickness of the film. Films (blown films of 110 μm) are produced as described below in the film preparation example. The tear strength or tear resistance is measured in the longitudinal direction (MD) and / or transverse direction (TD).

[0220] B. Examples

[0221] Material

[0222] Anteo TM FK1820 is a bimodal terpolymer LLDPE commercially available from Borealis with a density of 918 kg / m 3 , MFR 2 It is 1.5g / 10min.

[0223] FB5600 is a bimodal high density polyethylene commercially available from Borealis with a density of 958 kg / m 3 , MFR 2 It is 0.7g / 10min.

[0224] FB3450 is a bimodal polyethylene commercially available from Borealis with a density of 945 kg / m 3 , MFR 2 It is 0.3g / 10min.

[0225] NAV101 is a post-consumer recycled (PCR) LDPE commercially available from Ecoplast with a density of 925 kg / m 3 , MFR 2 It is 0.5g / 10min.

[0226] PPA is a polymer processing aid masterbatch AMF 905, commercially available from LyondellBasell.

[0227] White MB is rutile titanium dioxide NG 8600H 1, commercially available from LyondellBasell.

[0228] TP1 is a trimodal ethylene terpolymer, the production of which is detailed below.

[0229] Process for TP1

[0230] A trimodal ethylene / 1-butene / 1-hexene terpolymer was produced in a loop gas phase reactor unit which was subjected to a prepolymerisation step prior to the first loop polymerisation. The production conditions are detailed below.

[0231] Operating volume 50 dm at 70°C and 57 bar 3 A loop reactor was prepared. Ethylene, propane diluent, 1-butene as comonomer and hydrogen were added to the reactor. In addition, a solid polymerization catalyst component prepared as described in Example 1 of EP 1378528 was introduced into the reactor together with triethylaluminum cocatalyst so that the Al / Ti molar ratio was about 15. The estimated production split was about 2 wt%.

[0232] The slurry flow is continuously drawn out and introduced into a 150dm 3 The reactor was operated at a temperature of 95°C and a pressure of 56 bar. Additional ethylene, propane diluent and hydrogen were further added to the reactor to give an ethylene concentration of 4.7 mol% and a hydrogen to ethylene molar ratio of 306 mol / kmol in the fluid mixture. The estimated yield was 18 wt%. The MFR of the ethylene homopolymer removed from the reactor was 2 It is 195g / 10min.

[0233] The slurry stream was intermittently withdrawn from the reactor and introduced into a 350 dm 3The reactor was operated at a temperature of 95°C and a pressure of 54 bar. Fresh propane, ethylene and hydrogen were further added to the reactor to give an ethylene content of 5.5 mol% in the fluid mixture and a hydrogen to ethylene molar ratio of 563 mol / kmol. The estimated yield was 26 wt%. The MFR of the ethylene homopolymer removed from the reactor was 2 It is 390g / 10min.

[0234] The slurry was intermittently withdrawn from the loop reactor and introduced into a flash vessel operated at a temperature of 50°C and a pressure of 3 bar. From the flash vessel the polymer was introduced into a fluidized bed gas phase reactor operated at a pressure of 20 bar and a temperature of 82°C. Additional ethylene, 1-butene and 1-hexene comonomers, nitrogen and hydrogen as inert gases were added to give an ethylene content of 13.3 mol%, a 1-butene to ethylene molar ratio of 92.1 mol / kmol and a 1-hexene to ethylene molar ratio of 121.8 mol / kmol in the reaction mixture. The estimated yield was 54 wt%.

[0235] The polymer powder was mixed with 1200 ppm Irganox B561 and 400 ppm calcium stearate under nitrogen atmosphere. It was then compounded and extruded into pellets using a JSW CIMP90 twin screw extruder under nitrogen atmosphere. The final properties of TP1 are reported in Table 1.

[0236] Table 1. Characteristics of TP1

[0237] <![CDATA[Measured annular tube 1 MFR 2 (g / 10 min)]]> 195 Including prepolymerization loop 1 (%) 20 <![CDATA[Measured annular tube 1 + 2 MFR 2 (g / 10 min)]]> 390 Ring pipe 2 share (%) 26 <![CDATA[Calculated annular tube 2MFR 2 (g / 10 min)]]> 665 GPR share (%) 54 <![CDATA[Pellet density (kg / m 3 )]]> 940.7 <![CDATA[MFR of pellet]] 2 (g / 10 min)]]> 0.35 <![CDATA[MFR of pellet 5 (g / 10 min)]]> 1.45 <![CDATA[Pellet MFR 21 (g / 10 min)]]> 32.3 Total share (%) 100

[0238] Multilayer film

[0239] All membrane structures were made on the Alpine Hosokawa production line. All membrane structures were produced under the same processing conditions (BUR 2.5:1, thickness 110 microns, die gap 1.5 mm, die diameter 200 mm, output 180 kg / h, low neck height, external bubble cooling).

[0240] The structure of the produced multilayer film is given in Table 2 below, while the composition of each layer is given in Table 3.

[0241] Table 2. Layer structure of the examples

[0242] membrane O1(％) S1(％) C(％) S2(％) O2(％) IE1 15 20 30 20 15 IE2 17 - 66 - 17 IE3 17 - 66 - 17 CE1 17 - 66 - 17 CE2 17 - 66 - 17

[0243] Table 3. Composition of each layer (total film thickness is 110 μm)

[0244]

[0245] Table 4 below gives the properties of the films produced according to the recipe given in Table 3 (measured on blown films with a thickness of 110 μm).

[0246] Table 4. Properties of multilayer films

[0247]

[0248]

[0249] It is a well-known response that adding recycled content to a multilayer structure will reduce stiffness and toughness. However, as shown in Table 3, the inventors found that the multilayer film according to the embodiment of the present invention with recycled content in the core layer even showed higher tear resistance than CE2 without any recycled content and showed comparable mechanical properties. Comparing CE1 with recycled content with the embodiment of the present invention in which the core layer additionally includes TP1, it can be seen that the multilayer film shows better mechanical properties in terms of DDI, tear resistance and tensile modulus.

Claims

1. A multilayer film comprising: A) a first outer layer (O1) and a second outer layer (O2), wherein the first outer layer (O1) and / or the second outer layer (O2) comprises A1) a bimodal ethylene terpolymer having a molecular weight of 910 to 930 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 , containing at least C 4 -C 12 α-olefin comonomer, and A2) a first multimodal ethylene copolymer (CP1) having a molecular weight of 930 to 950 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 5.00 kg) 5 , including at least the first C 4 -C 12 α-olefin comonomers, B) a core layer (C) sandwiched between a first outer layer (O1) and a second outer layer (O2), wherein the core layer (C) include B1) Recycled LDPE having a molecular weight of 910 to 940 kg / m 3 and a MFR of 0.1 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 ,as well as B2) a second multimodal ethylene copolymer (CP2) having a molecular weight of 930 to 950 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 5.00 kg) 5 , including at least the first C 4 -C 12 α-Olefin Comonomer wherein the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) is trimodal comprising: - a first ethylene homopolymer in an amount of 10 to 30 wt%, more preferably 15 to 25 wt%; - an amount of 15 to 35 wt%, more preferably 20 to 30 wt% of a second ethylene homopolymer having an MFR of 1.0% to component a) measured according to ISO 1133 (190°C, 2.16 kg) 2 MFR at least 50g / 10min higher 2 ;as well as - 35 to 75 wt%, more preferably 45 to 65 wt% of a third ethylene copolymer having at least a first C 4 -C 12 α-olefin comonomers; Therein these amounts are based on the total weight of the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2).

2. The multilayer film according to claim 1, wherein the first multimodal ethylene copolymer (CP1) and the second multimodal ethylene copolymer (CP2) have the same composition.

3. The multilayer film according to any one of the preceding claims, wherein the first C 4 -C 12 The α-olefin comonomer is 1-butene.

4. The multilayer film according to any one of the preceding claims, wherein the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) comprises a second C 6 -C 20 0 contains an olefin comonomer, preferably 1-hexene.

5. The multilayer film according to any one of the preceding claims, wherein the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) has an MFR measured according to ISO 1133 (190°C, 2.16 kg) of 0.1 to 3.0 g / 10 min, more preferably of 0.2 to 1.5 g / 10 min, most preferably of 0.25 to 0.80 g / 10 min. 2 .

6. The multilayer film according to any one of the preceding claims, wherein the first multimodal ethylene copolymer (CP1) and / or the second multimodal ethylene copolymer (CP2) has an MFR measured according to ISO 1133 (190°C, 21.6 kg) of 5 to 100 g / 10 min, more preferably of 10 to 80 g / 10 min, most preferably of 20 to 60 g / 10 min. 21 .

7. The multilayer film according to any one of the preceding claims, wherein the amount of the first ethylene copolymer (CP1) in the first outer layer (O1) and / or the second outer layer (O2) is 50-90 wt%, more preferably 55 to 80 wt%, most preferably 62 to 75 wt%, based on the total weight of the first outer layer (O1) and / or the second outer layer (O2).

8. The multilayer film according to any one of the preceding claims, wherein the core layer (C) comprises: a) 30 to 90 wt%, more preferably 45 to 80 wt% of recycled LDPE, based on the total weight of the core layer (C), and b) 5 to 70 wt%, more preferably 7 to 55 wt%, based on the total weight of the core layer (C) of the second multimodal ethylene copolymer (CP2).

9. The multilayer film according to any one of the preceding claims, wherein the C of the bimodal ethylene terpolymer is 4 -C 12 The α-olefin comonomer is 1-butene.

10. The multilayer film of claim 9, wherein the bimodal ethylene terpolymer is an ethylene / 1-butene / 1-hexene terpolymer.

11. The multilayer film according to any one of the preceding claims, further comprising a first sub-skin layer (S1) and a second sub-skin layer (S2), wherein the first sub-skin layer (S1) and the second sub-skin layer (S2) are respectively placed between the core layer (C) and the first outer layer (O1) and the second outer layer (O2).

12. The multilayer film according to claim 11, wherein the first sub-layer (S1) and / or the second sub-layer (S2) include: a) recycled LDPE having a molecular weight of 910 to 940 kg / m 3 and a MFR of 0.1 to 10 g / 10 min measured according to ISO 1133 (190° C., 2.16 kg) 2 ,as well as b) a second multimodal ethylene copolymer (CP2) having a molecular weight of 930 to 950 kg / m 3 and a density of 0.5 to 10 g / 10 min measured according to ISO 1133 (190° C., 5.00 kg) 5 , It contains at least the first C 4 -C 12 α-olefin comonomer.

13. The multilayer film according to any of the preceding claims, wherein the film has a relative tear resistance in the machine direction (MD) of 20 to 250 N / mm, more preferably 25 to 150 N / mm, measured on a 110 μm blown film according to ISO 6383 / 2 and / or a relative tear resistance in the transverse direction (TD) of 200 to 450 N / mm, more preferably 270 to 400 N / mm, measured on a 110 μm blown film according to ISO 6383 / 2.

14. The multilayer film according to any of the preceding claims, wherein the film has a relative tear resistance in the machine direction (MD) of 350 to 580 MPa, more preferably 400 to 550 MPa / mm, measured on a 110 μm blown film according to ISO 527-3 and / or a relative tear resistance in the transverse direction (TD) of 400 to 700 MPa / mm, more preferably 500 to 650 MPa, measured on a 110 μm blown film according to ISO 527-3.

15. A heavy duty transport bag comprising the multilayer film according to any one of claims 1 to 14.

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