Polymer composition comprising regenerated low density polyethylene for packaging applications

Abstract

The present invention relates to a polymer composition comprising a regenerated low density polyethylene and a linear low density polyethylene, the linear low density polyethylene being a terpolymer of ethylene and two alpha-olefin comonomers and having a density in the range of 915 kg / m3 and above to less than 928 kg / m3. In addition, the present invention provides a monolayer film comprising the polymer composition or a multilayer film structure comprising the polymer composition, and methods of making the same. Furthermore, the present invention relates to the use of a linear low density polyethylene, which is a terpolymer of ethylene and two alpha-olefin comonomers and has a specific range of densities, for the manufacture of a monolayer film comprising a regenerated low density polyethylene.

Description

Technical Field

[0001] The present invention relates to a polymer composition comprising recycled low-density polyethylene and linear low-density polyethylene, wherein the linear low-density polyethylene is a terpolymer of ethylene and two α-olefin comonomers and has a density of 915 kg / m 3 Up to 928kg / m 3 In addition, the present invention provides a monolayer film comprising the polymer composition or a multilayer film structure comprising the polymer composition, and methods for producing the same. In addition, the present invention relates to the use of a linear low-density polyethylene, which is a terpolymer of ethylene and two α-olefin comonomers, having a density within a specific range, for producing a monolayer film comprising recycled low-density polyethylene. Background Art

[0002] Large amounts of waste plastics, such as those from packaging applications, are generated daily. Available strategies for dealing with these waste plastics remain unsatisfactory from an environmental perspective. Therefore, developing concepts for recycling waste plastics is an important area of ​​research.

[0003] Furthermore, attempts to reuse plastics are gaining interest not only for ecological reasons. Recycling also reduces production costs, which is of course another attractive aspect of recycled plastics.

[0004] In light of the above, the polymer industry is committed to including polymers from waste materials in the manufacture of new products, so that waste plastics (e.g., post-consumer recyclate, PCR) can be converted into a resource for new plastic products. However, complicating this process is the fact that products containing post-consumer recyclate (e.g., film structures) often have poor mechanical properties, particularly low stiffness combined with low toughness.

[0005] One known countermeasure is to increase the thickness of the membrane, but this is undesirable for several reasons, as this approach is not only resource-unfriendly but also increases production costs.

[0006] Film structures containing waste plastics are occasionally mentioned in the prior art. For example, International Application WO 2020 / 207940 A1 provides a collation shrink film whose core layer comprises recycled low-density polyethylene. This film is used in packaging applications. However, compared to other film structures, collation shrink films have specific performance requirements, such as mechanical properties.

[0007] It is therefore an object of the present invention to provide a polymer composition comprising recycled low density polyethylene suitable for the manufacture of film structures meeting the general requirements for packaging applications, in particular with regard to mechanical and optical properties.

[0008] Another object of the present invention is to provide corresponding films comprising recycled low-density polyethylene, but without the disadvantages typically associated with recycled materials.

[0009] Furthermore, it is an object of the present invention to identify a virgin polymer suitable for the production of monolayer films which, despite comprising recycled low-density polyethylene, still have excellent mechanical properties. Summary of the Invention

[0010] This object is achieved by the polymer composition according to independent claim 1, the monolayer film and the multilayer film structure according to claim 10, and the use of the linear low-density polyethylene for the production of a monolayer film comprising recycled low-density polyethylene according to claim 15. Advantageous embodiments can be derived from the dependent claims.

[0011] The polymer composition according to the present invention comprises 25 wt.-% to 95 wt.-% of a linear low density polyethylene and 5 wt.-% to 75 wt.-% of a recycled low density polyethylene, relative to the total weight of the polymer composition, wherein the linear low density polyethylene is a terpolymer of ethylene and two α-olefin comonomers and has a density of 915 kg / m 3 and above up to 928kg / m 3 Within the following range.

[0012] The polymer composition exhibits excellent processing properties. Most notably, it offers exceptional performance characteristics, particularly excellent mechanical, rheological, and optical properties. This performance profile allows the polymer composition to be extruded into films using any method known in the art. These films exhibit a good balance between stiffness (tensile modulus) and toughness (dart drop impact strength (DDI)). Furthermore, due to their favorable rheological properties, these films can be produced at high throughputs at typical melt pressures.

[0013] In an embodiment, the polymer composition comprises 35 wt.-% to 85 wt.-% linear low density polyethylene and 15 wt.-% to 65 wt.-% recycled low density polyethylene.

[0014] In another embodiment, the polymer composition has an MFR2 in the range of 0.05 g / 10 min to 5.0 g / 10 min, preferably in the range of 0.1 g / 10 min to 1.0 g / 10 min, even more preferably in the range of 0.2 g / 10 min to 0.6 g / 10 min, measured according to ISO 1133. In addition, the polymer composition may have a density of 920 kg / m3 and above up to 935kg / m 3 and below, preferably 922 kg / m 3 and above up to 930kg / m 3 and below.

[0015] The polymer composition of the present invention can be provided in the form of powder or particles, preferably particles. Particles can be obtained by conventional extrusion, granulation or grinding technology and are an ideal form for the polymer composition of the present invention because the particles can be directly added to the conversion machinery. Particles are different from polymer powders having a particle size less than 1 mm. In addition, the use of particles ensures that the polymer composition can be added to the conversion machinery by a simple online addition method and converted into a film.

[0016] Linear low-density polyethylene (LLDPE)

[0017] The linear low density polyethylene (LLDPE) is preferably a multimodal LLDPE, more preferably a more than bimodal LLDPE, in particular a trimodal LLDPE. Further preferably, the LLDPE is a virgin polymer material.

[0018] In one embodiment, the MFR2 of the LLDPE is in the range of 0.01 g / 10 min to 0.5 g / 10 min, preferably in the range of 0.1 g / 10 min to 0.4 g / 10 min, even more preferably in the range of 0.15 g / 10 min to 0.3 g / 10 min, measured according to ISO 1133. The MFR5 of the LLDPE is in the range of 0.5 g / 10 min to 5.0 g / 10 min, preferably in the range of 0.5 g / 10 min to 3.0 g / 10 min, more preferably in the range of 0.6 g / 10 min to 2.0 g / 10 min, even more preferably in the range of 0.7 g / 10 min to 1.5 g / 10 min, measured according to ISO 1133. 21 It may be in the range of 5 g / 10 min to 40 g / 10 min, more preferably in the range of 10 g / 10 min to 30 g / 10 min, and even more preferably in the range of 15 g / 10 min to 28 g / 10 min.

[0019] The density of LLDPE is preferably 918 kg / m 3 Up to 925kg / m 3 within the range.

[0020] As mentioned above, MFR2, MFR5, MFR 21The density range is related to the LLDPE after extrusion into pellets.

[0021] The two α-olefin comonomers can be selected from the group of α-olefins having 3 to 10 carbon atoms, in particular 1-butene and 1-hexene. Therefore, it is most preferred that the terpolymer formed by ethylene and the two α-olefin comonomers is an ethylene / 1-butene / 1-hexene terpolymer.

[0022] The LLDPE may comprise, relative to the total weight of the LLDPE, 5 to 25 wt.-% of a first ethylene copolymer fraction (A1) consisting of a copolymer of ethylene and at least a first α-olefin comonomer, preferably having a density of 920 kg / m², measured according to ISO 1183. 3 Up to 960kg / m 3 in the range of: 15 wt.-% to 35 wt.-% of a second ethylene copolymer fraction (A2), relative to the total weight of the LLDPE, consisting of a copolymer of ethylene and at least said first α-olefin comonomer, having a density preferably in the range of 920 kg / m 3 Up to 960kg / m 3 and 40 wt.-% to 80 wt.-% of a third ethylene copolymer fraction (B), relative to the total weight of the LLDPE, consisting of a polymer of ethylene with at least said first and second α-olefin comonomers, wherein the weight average molecular weight (Mw) of the third ethylene copolymer fraction (B) is preferably higher than the weight average molecular weight (Mw) of the first ethylene copolymer fraction (A1) and the second ethylene copolymer fraction (A2).

[0023] According to quantitative 13 The content of the second α-olefin comonomer in the third ethylene copolymer fraction (B) is preferably in the range of 15 to 85 % based on the moles of the total comonomer content in the third ethylene copolymer fraction (B), as determined by C-NMR spectroscopy.

[0024] As detailed in the Examples section below, based on the quantitative 13 The total comonomer content of the LLDPE is preferably in the range of 1.5 mol-% to 5.0 mol-%, determined by C-NMR spectroscopy analysis. More preferably, the total comonomer content of the LLDPE is in the range of 2.5 mol-% to 3.9 mol-%.

[0025] According to a particularly preferred embodiment, the LLDPE comprises a first α-olefin comonomer, more preferably 1-butene, in an amount according to the quantitative 130.5 mol-% to 4.5 mol-% as determined by C-NMR spectroscopy; and / or a second α-olefin comonomer, more preferably 1-hexene, the content of which is determined by quantitative 13 C-NMR spectral analysis determined it to be 0.5 mol-% to 4.5 mol-%.

[0026] In addition, the number average molecular weight (Mn) of the LLDPE may be in the range of 8,000 g / mol to 14,000 g / mol, preferably 9,000 to 12,000 g / mol; and / or the weight average molecular weight (Mw) of the LLDPE may be in the range of 150,000 g / mol to 200,000 g / mol, preferably 160,000 g / mol to less than 190,000 g / mol; and / or the z-average molecular weight (Mz) of the LLDPE may be in the range of 750,000 g / mol to 1,000,000 g / mol, preferably 800,000 g / mol to 920,000 g / mol; wherein the molecular weight averages Mw, Mn and Mz are determined by gel permeation chromatography (e.g., as described in the Examples section below).

[0027] The Mw / Mn ratio of the LLDPE is preferably in the range of 10 to 25. The Mz / Mw ratio of the LLDPE is preferably in the range of 4 to 10. More preferably, the Mw / Mn ratio of the LLDPE is in the range of 10 to 20, and / or the Mz / Mw ratio of the LLDPE is in the range of 4 to 8.

[0028] LLDPE-first ethylene copolymer part (A1)

[0029] The first ethylene copolymer fraction (A1) may be a copolymer of ethylene and at least a first α-olefin comonomer. Preferably, the first ethylene copolymer fraction (A1) comprises 5 to 25 wt.-%, more preferably 10 to 20 wt.-% of the LLDPE. The first α-olefin comonomer may be selected from α-olefin comonomers having 3 to 10 carbon atoms. More preferably, the first α-olefin comonomer is selected from 1-butene, 1-hexene and 1-octene; even more preferably, the first α-olefin comonomer is 1-butene. According to a particularly preferred embodiment of the present invention, the first ethylene copolymer fraction (A1) is a copolymer of ethylene and 1-butene.

[0030] The MFR2 of the first ethylene copolymer fraction (A1 ), determined according to ISO 1133, is preferably in the range of 50 to 600 g / 10 min, preferably in the range of 100 to 500 g / 10 min.

[0031] The density of the first ethylene copolymer fraction (A1) is 920 kg / m 3 Up to 960kg / m 3 In the range of 940kg / m 3 Up to 955kg / m 3 within the range.

[0032] LLDPE-second ethylene copolymer portion (A2)

[0033] The second ethylene copolymer fraction (A2) may be a copolymer of ethylene and at least a first α-olefin comonomer. Preferably, the second ethylene copolymer fraction (A2) comprises from 15 wt.% to 35 wt.%, more preferably from 20 wt.% to 30 wt.% of the LLDPE. The first α-olefin comonomer may be the same as the first α-olefin comonomer in the first ethylene copolymer fraction (A1) and may preferably be selected from α-olefin comonomers having from 3 to 10 carbon atoms. More preferably, the first α-olefin comonomer is selected from 1-butene, 1-hexene and 1-octene; even more preferably, the first α-olefin comonomer is 1-butene. According to a particularly preferred embodiment of the present invention, the second ethylene copolymer fraction (A2) is a copolymer of ethylene and 1-butene.

[0034] The MFR2 of the second ethylene copolymer fraction (A2), determined according to ISO 1133, is in the range of 50 to 600 g / 10 min, preferably in the range of 100 to 500 g / 10 min.

[0035] The density of the second ethylene copolymer fraction (A2) is 920 kg / m 3 Up to 960kg / m 3 In the range of 945kg / m 3 Up to 955kg / m 3 within the range.

[0036] The first ethylene polymer mixture (hereinafter referred to as PEM1) comprises a first ethylene copolymer fraction (A1), a second ethylene copolymer fraction (A2) and, optionally, another polymer fraction from a prepolymerization step.

[0037] The total comonomer content of the first ethylene polymer mixture (PEM1) is preferably in the range of 0.5 mol-% to 3.0 mol-%.

[0038] LLDPE-third ethylene copolymer part (B)

[0039] The third ethylene copolymer portion (B) can be a terpolymer of ethylene with a first α-olefin comonomer and a second α-olefin comonomer. Preferably, the third ethylene copolymer portion (B) accounts for 40 wt.-% to 80 wt.-%, more preferably 50 wt.-% to 70 wt.-% of the LLDPE. The first α-olefin comonomer can be the same as the first α-olefin comonomer in the above first ethylene copolymer portion (A1) and the second ethylene copolymer portion (A2). On the other hand, the second α-olefin comonomer is preferably selected from α-olefin comonomers having 3 to 10 carbon atoms. More preferably, the second α-olefin comonomer is selected from 1-butene, 1-hexene and 1-octene. More preferably, the third ethylene copolymer portion (B) includes 1-butene (as the first α-olefin comonomer) and / or 1-hexene (as the second α-olefin comonomer). Even more preferably, the third ethylene copolymer portion (B) is a terpolymer of ethylene, 1-butene and 1-hexene. In the present embodiment, according to the quantitative 13 The LLDPE may comprise 0.5 mol-% to 4.0 mol-% of 1-butene, more preferably 0.5 mol-% to 3.0 mol-% of 1-butene, even more preferably 0.5 mol-% to 2.0 mol-% of 1-butene, as determined by C NMR spectroscopy, and / or 13 C NMR spectral analysis determined that it contained 0.5 mol-% to 4.0 mol-% of 1-hexene.

[0040] According to quantitative 13 The total comonomer content in the third ethylene copolymer fraction (B) is preferably between 1 and 10 mol%, more preferably between 2 and 8 mol%, even more preferably between 3 and 7 mol%, determined by C NMR spectroscopy.

[0041] According to quantitative 13 The content of the second α-olefin comonomer in the third ethylene copolymer fraction (B) is from 15% to 85%, preferably from 20% to 83%, even more preferably from 25% to 80%, based on the moles of the total comonomer content in the third ethylene copolymer fraction (B), as determined by C NMR spectroscopy.

[0042] According to a particularly preferred embodiment, the third ethylene copolymer fraction (B) is a terpolymer of ethylene, 1-butene and 1-hexene, wherein the 13 The 1-hexene content is 25% to 80% based on the moles of the total comonomer content in the third ethylene copolymer portion (B), as determined by C NMR spectroscopy; and 13The total comonomer content in the third ethylene copolymer fraction (B) is between 3 mol-% and 7 mol-%, as determined by C NMR spectroscopy.

[0043] The weight average molecular weight (M W ) is preferably higher than the weight average molecular weight (M) of the first ethylene copolymer fraction (A1) and the second ethylene copolymer fraction (A2). W ).

[0044] The first ethylene polymer mixture (PEM1) and the third ethylene copolymer fraction (B) are preferably included in the second ethylene polymer mixture (PEM2). Preferably, the first ethylene polymer mixture (PEM1) and the third ethylene copolymer fraction (B) constitute and / or consist of the second ethylene polymer mixture (PEM2). The LLDPE may comprise or consist of the second ethylene polymer mixture (PEM2).

[0045] The MFR2 of the second ethylene polymer mixture (PEM2), determined according to ISO 1133, is preferably in the range of 0.01 to 0.5 g / 10 min, more preferably in the range of 0.1 to 0.4 g / 10 min, even more preferably in the range of 0.15 to 0.30 g / 10 min.

[0046] The second ethylene polymer mixture (PEM2) preferably has an MFR5, determined according to ISO 1133, in the range of 0.1 to 2.0 g / 10 min, more preferably in the range of 0.5 to 1.5 g / 10 min, even more preferably in the range of 0.7 to 1.2 g / 10 min.

[0047] The MFR of the second ethylene polymer mixture (PEM2) is determined according to ISO 1133. 21 Preferably it is in the range of 5 g / 10 min to 40 g / 10 min, more preferably in the range of 10 g / 10 min to 30 g / 10 min, even more preferably in the range of 15 g / 10 min to 27 g / 10 min.

[0048] The density of the second ethylene polymer mixture (PEM2) is preferably 900 kg / m 3 Up to 940kg / m 3 , more preferably 910 kg / m 3 Up to 930kg / m 3 , even more preferably 915 g / 10 min to 925 g / 10 min.

[0049] LLDPE-polymerization process

[0050] The process of the present invention for producing LLDPE as described above comprises the following steps (a) to (d):

[0051] (a) polymerizing ethylene with at least a first α-olefin comonomer in a first polymerization step to produce a first ethylene copolymer fraction (A1),

[0052] (b) in a second polymerization step, polymerizing ethylene with at least said first α-olefin comonomer in the presence of said first ethylene copolymer fraction (A1) to produce a first ethylene polymer mixture (PEM1) comprising said first ethylene copolymer fraction (A1) and a second ethylene copolymer fraction (A2),

[0053] (c) polymerizing ethylene, a first α-olefin comonomer and a second α-olefin comonomer in the presence of said first ethylene polymer mixture (PEM1) in a third polymerization step to produce a second ethylene polymer mixture (PEM2) comprising the first ethylene polymer mixture (PEM1) and a third ethylene copolymer fraction (B), and

[0054] (d) extruding the second ethylene polymer mixture (PEM2) to obtain LLDPE.

[0055] Preferably, steps (a), (b) and (c) of the process are carried out in the presence of a Ziegler-Natta polymerisation catalyst.

[0056] The first α-olefin comonomer and the second α-olefin comonomer used in steps (a), (b) and (c) can be independently selected from α-olefins having 3 to 10 carbon atoms and mixtures thereof. Particularly suitable α-olefins are those having 4 to 8 carbon atoms, including mixtures thereof. Particularly preferred α-olefins are 1-butene, 1-hexene and 1-octene and mixtures thereof. The first α-olefin comonomer used in steps (a), (b) and (c) is preferably the same, while the second α-olefin comonomer is preferably different from the first α-olefin comonomer. The polymerization steps can be connected in any order, i.e. the first polymerization step can be carried out before the second polymerization step, or the second polymerization step can be carried out before the first polymerization step, or, alternatively, the polymerization steps can be connected in parallel. However, it is preferred to carry out the polymerization steps in a cascade mode.

[0057] LLDPE-Catalyst

[0058] As already indicated above, the polymerisation steps (a), (b) and (c) of the process for producing LLDPE described herein are preferably carried out in the presence of a Ziegler-Natta polymerisation catalyst.

[0059] Ziegler-Natta catalysts are useful because they can produce polymers with a wide molecular weight range and other desirable properties at high productivity.The Ziegler-Natta catalyst used in the present invention is preferably supported on an external support.

[0060] Suitable Ziegler-Natta catalysts preferably comprise a magnesium compound, an aluminum compound and a titanium compound supported on a particulate support.

[0061] Typical particle supports used in Ziegler-Natta catalysts include inorganic oxide supports such as silica, alumina, titania, silica-alumina and silica-titanium oxide, 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.

[0062] The average particle size of the silica support can typically be between 10 μm and 100 μm. However, particular advantages have been shown to be achieved if the average particle size of the support is between 15 μm and 30 μm, preferably between 18 μm and 25 μm. Alternatively, the average particle size of the support can be between 30 μm and 80 μm, preferably between 30 μm and 50 μm. Examples of suitable support materials include ES747JR, manufactured and sold by Ineos Silicas (formerly Crossfield), and SP9-491, manufactured and sold by Grace.

[0063] 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, with 2-ethyl-1-hexanol being an example of a preferred alcohol. The dialkylmagnesium can be any compound in which magnesium is bonded to two alkyl groups, which may be the same or different. Butyl-octylmagnesium is an example of a preferred dialkylmagnesium.

[0064] The aluminum compound is an alkylaluminum chloride. Particularly preferred compounds are alkylaluminum dichloride, dialkylaluminum chloride and alkylaluminum sesquichloride.

[0065] 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.

[0066] The catalyst can be prepared by contacting the supporting matrix with the above compounds in sequence, as described in EP-A-688794 or WO-A-99 / 51646. Alternatively, the catalyst can be prepared by first preparing a solution from the components and then contacting the solution with the supporting matrix, as described in WO-A-01 / 55230.

[0067] Ziegler-Natta catalysts are used together with an activator (also referred to as a co-catalyst). Suitable activators are metal alkyl compounds, typically Group 13 metal alkyl compounds, particularly alkyl aluminum compounds. Alkyl aluminum compounds include trialkyl aluminum compounds, such as trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, trihexylaluminum, and tri-n-octylaluminum. Alkyl aluminum compounds can also include alkyl aluminum halides (such as ethyl aluminum dichloride, diethyl aluminum chloride, ethyl aluminum sesquichloride, dimethyl aluminum chloride, etc.), alkyl aluminum oxides (such as methylaluminoxane, hexaisobutylaluminoxane, and tetraisobutylaluminoxane), and other alkyl aluminum compounds (such as isoprenyl aluminum). Particularly preferred co-catalysts are trialkyl aluminums, of which triethyl aluminum, trimethyl aluminum, and triisobutyl aluminum are particularly preferred.

[0068] The amount of activator used depends on the specific catalyst and activator. Typically, triethylaluminum is used in an amount such that the molar ratio of aluminum to transition metal (such as Al / Ti) is, for example, 1 to 1000, preferably 3 to 100, in particular about 5 to about 30 mol / mol.

[0069] LLDPE-prepolymer

[0070] In addition to the actual polymerization steps (a), (b), and (c) (i.e., in addition to the at least three polymerization steps described), the process may also include a prepolymerization step prior to the actual polymerization step. The purpose of the prepolymerization step is to polymerize a small amount of polymer onto the catalyst under conditions of low temperature and / or low monomer concentration. Prepolymerization can improve the performance of the catalyst. The prepolymerization step is carried out in a slurry.

[0071] Therefore, the prepolymerization step can be carried out in a loop reactor. The prepolymerization is 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 thereof.

[0072] The temperature in the prepolymerization step is typically from 0 to 90° C., preferably from 20 to 80° C. and more preferably from 55 to 75° C. The pressure is not critical and is typically from 1 to 150 bar, preferably from 40 to 80 bar.

[0073] In the prepolymerization step, the amount of monomer typically makes about 0.1 gram to 1000 gram of monomer per 1 gram of solid catalyst component polymerizable. As known to those skilled in the art, the catalyst particles recovered from the continuous prepolymerization reactor are not all containing the same amount of prepolymer. On the contrary, each particle has its own characteristic amount, and this amount depends on the residence time of the particle in the prepolymerization reactor. Because the time that some particles stay in the reactor is relatively long, and the time that other particles stay is relatively short, the prepolymer amount on different particles is also different, and some individual particles can include the prepolymer amount that exceeds the above-mentioned limit value. However, the average amount of prepolymer on the catalyst is typically within the above-mentioned limit value range.

[0074] As known in the art, the molecular weight of the prepolymer can be controlled by hydrogen. In addition, as disclosed in WO-A-96 / 19503 and WO-A-96 / 32420, antistatic additives can be used to prevent the particles from sticking to each other or to the walls of the reactor.

[0075] If a prepolymerization step is used, the prepolymer is preferably an ethylene copolymer. Any prepolymer component is considered to be part of the first ethylene copolymer portion (A1). Therefore, when determining the proportion, MFR, density, etc. of the first polymer, the prepolymer should be considered to be part of the first ethylene copolymer portion (A1).

[0076] When a prepolymerization step is present, the catalyst components are preferably all introduced (individually or together) into the prepolymerization step. However, in the case where the solid catalyst component and the cocatalyst can be fed separately, it is possible to introduce only a portion of the cocatalyst into the prepolymerization stage, with the remainder being introduced into the subsequent polymerization stage. In this case, it is also necessary to introduce the cocatalyst into the prepolymerization stage in order to obtain sufficient polymerization in the prepolymerization stage.

[0077] 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 polymer composition. In particular, it is preferred that the melt flow rate of the prepolymer is greater than the melt flow rate of the final polymer, but less than the melt flow rate of the polymer produced in the first polymerization stage (i.e., the first ethylene copolymer fraction (A1)). It is further preferred that the density of the prepolymer is greater than the density of the final polymer. Suitably, the density is approximately the same as or greater than the density of the polymer produced in the first polymerization stage (i.e., the first ethylene copolymer fraction (A1)). Furthermore, the amount of prepolymer used typically does not exceed about 5% by weight of the LLDPE, more preferably does not exceed 2% by weight of the LLDPE.

[0078] LLDPE-polymerization step (a)

[0079] Step (a) of the process comprises polymerizing ethylene and a first α-olefin comonomer in a first polymerization reactor to produce a first ethylene copolymer fraction (A1).

[0080] In step (a), a first ethylene copolymer fraction (A1) is produced. The density of the first ethylene copolymer fraction (A1), measured according to ISO 1183, is between 920 kg / m 3 Up to 960kg / m 3 and preferably, the melt flow rate MFR2, determined according to ISO 1133, of the first ethylene copolymer fraction (A1) is from 50 g / 10 min to 600 g / 10 min.

[0081] The catalyst can be transferred to the first polymerization step by any means known in the art. Thus, the catalyst can be suspended in a diluent and maintained in a homogeneous slurry. Particularly preferably, an oil having a viscosity of 20 to 1500 mPa·s is used as the diluent, as disclosed in WO-A-2006 / 063771. Alternatively, the catalyst can be mixed with a viscous mixture of grease and oil, and the resulting paste fed to the first polymerization step. Alternatively, the catalyst can be allowed to settle, as disclosed in EP-A-428054, and the resulting catalyst slurry partially introduced into the first polymerization step. Prior to the first polymerization step, a prepolymerization step as described above can also be carried out, in which case the mixture removed from the prepolymerization step is fed into the first polymerization step (a).

[0082] In the first polymerization step (a), ethylene, a first α-olefin, an optional inert diluent and optionally hydrogen are introduced in such amounts that the melt flow rate MFR2 and density of the first ethylene copolymer fraction (A1) are within the desired ranges.

[0083] Preferably, the first α-olefin is as defined above, having 3 to 10 carbon atoms. In particular, preferred α-olefins are 1-butene, 1-hexene and 1-octene. It is particularly preferred that the first α-olefin comonomer is 1-butene.

[0084] The polymerization of the first polymerization step (a) can be carried out in a slurry. The polymer particles formed during the polymerization are then suspended in a hydrocarbon fluid together with the fragmentation catalyst dispersed within the particles. The slurry is stirred to transfer the reactants from the fluid to the particles.

[0085] The polymerization usually takes place in an inert diluent, which is typically a hydrocarbon diluent such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, or a mixture thereof. Preferably, the diluent is a low-boiling hydrocarbon having 1 to 4 carbon atoms or a mixture thereof. A particularly preferred diluent is propane, which may contain small amounts of methane, ethane, and / or butane.

[0086] The ethylene content of the fluid phase of the slurry may be from 1 mol% to about 50 mol%, preferably from about 1.5 mol% to about 20 mol%, and particularly from about 2 mol% to about 15 mol%. A high ethylene concentration has the advantage of increased catalyst productivity, but a disadvantage is that more ethylene needs to be recovered at high concentrations than at lower concentrations.

[0087] 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 of step (a) is carried out in a loop reactor. In such reactors, the slurry is circulated at high speed along a closed conduit using a circulation pump. Loop reactors are generally known in the art and are exemplified, for example, in US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186 and US-A-5391654.

[0088] If the first ethylene copolymer portion (A1) is produced under a ratio of the first α-olefin to ethylene of no more than about 400 mol / kmol (e.g., no more than 300 mol / kmol), it is generally advantageous to carry out a slurry polymerization above the critical temperature and critical pressure of the fluid mixture. Such an operation is described in US-A-5391654.

[0089] When the first polymerization step (a) is carried out as a slurry polymerization, the step is carried out at a temperature ranging from 50° C. to 115° C., preferably from 70° C. to 110° C., and particularly from 80° C. to 105° C. In this case, the pressure of the first polymerization step (a) is from 1 bar to 300 bar, preferably from 40 bar to 100 bar, and more preferably from 50 bar to 80 bar.

[0090] The amount of hydrogen used is adjusted based on the desired melt flow rate of the first ethylene copolymer fraction (A1) and depends on the specific catalyst used. For many commonly used Ziegler-Natta catalysts, the molar ratio of hydrogen to ethylene is from 10 mol / kmol to 2000 mol / kmol, preferably from 100 mol / kmol to 1000 mol / kmol, more preferably from 150 mol / kmol to 800 mol / kmol, in particular from 200 mol / kmol to 500 mol / kmol.

[0091] The amount of the first α-olefin is adjusted based on the desired density of the first ethylene copolymer portion (A1) and is also dependent on the specific catalyst used. For many commonly used Ziegler-Natta catalysts, the molar ratio of the first α-olefin to ethylene is from 100 mol / kmol to 1000 mol / kmol, preferably from 150 mol / kmol to 600 mol / kmol, more preferably from 150 mol / kmol to 500 mol / kmol.

[0092] The polymerization of step (a) can also be carried out in the gas phase. A preferred embodiment of a gas phase polymerization reactor is a fluidized bed reactor. In this reactor, the polymer particles formed during the polymerization are suspended in an upwardly flowing gas. The gas is introduced into the bottom of the reactor. The upwardly flowing gas passes through the fluidized bed, where a portion of the gas reacts in the presence of a catalyst, while 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 circulating gas to a temperature at which a portion of the gas condenses. After cooling, the circulating gas is reintroduced into the bottom of the reactor. Fluidized bed polymerization reactors are disclosed in, for example, 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.

[0093] According to a preferred embodiment of the present invention, the polymerization of the first polymerization step (a) is carried out in slurry.

[0094] 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.

[0095] Preferably, at least a first α-olefin comonomer is present in the first polymerization step (a), wherein the polymer produced in the first step is a first ethylene copolymer fraction (A1). Preferably, the polymerization is carried out as a slurry polymerization in a liquid diluent at a temperature of 50°C to 115°C (e.g., 70°C to 115°C) and a pressure of 1 bar to 300 bar (e.g., 40 bar to 100 bar (e.g., 50 bar to 80 bar)). The molar ratio of the first α-olefin to ethylene is 100 mol / kmol to 1000 mol / kmol, preferably 150 mol / kmol to 600 mol / kmol, more preferably 150 mol / kmol to 500 mol / kmol, most preferably 180 mol / kmol to 400 mol / kmol. The molar ratio of hydrogen to ethylene is then suitably from 10 mol / kmol to 2000 mol / kmol, preferably from 100 mol / kmol to 1000 mol / kmol, more preferably from 150 mol / kmol to 800 mol / kmol, in particular from 200 mol / kmol to 500 mol / kmol. The MFR2 of the first ethylene copolymer fraction (A1) produced in the first polymerization step (a), measured according to ISO 1133, is preferably in the range of 50 g / 10min to 600 g / 10min.

[0096] In the first polymerisation step (a), the polymerisation rate is suitably controlled to achieve the desired amount of the first ethylene copolymer fraction (A1) in the LLDPE.The polymerisation rate is suitably controlled by adjusting the ethylene concentration in the first polymerisation step (a).

[0097] When the first 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 mol-% to 10 mol-%, preferably from 3 mol-% to 8 mol-%.

[0098] LLDPE-polymerization step (b)

[0099] The second ethylene copolymer fraction (A2) may be produced in the second polymerization step (b) in the presence of the first ethylene copolymer fraction (A1 ).

[0100] The polymerization can be carried out in slurry, gas phase or solution. In the second polymerization step (b), the second ethylene copolymer (A2) is produced in the presence of the first ethylene copolymer (A1). Therefore, the polymer produced in the second polymerization step (b) is a mixture of the first ethylene copolymer fraction (A1) and the second ethylene copolymer fraction (A2), i.e., the first ethylene polymer mixture (PEM1).

[0101] The density of the second ethylene copolymer fraction (A2) is preferably between 920 kg / m3 Up to 960kg / m 3 The melt flow rate MFR2 of the second ethylene copolymer fraction (A2) is preferably in the range of 50 g / 10 min to 600 g / 10 min, and / or measured according to ISO 1133.

[0102] The first ethylene copolymer fraction (A1) is transferred from the first polymerization step (a) to the second polymerization step (b) by using any method known to a 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 means of the pressure difference between the first polymerization step (a) and the second polymerization step (b).

[0103] In the second polymerization step (b), ethylene, the first α-olefin comonomer, an optional inert diluent, and optional hydrogen may be introduced. The amount of hydrogen and α-olefin introduced may be such that the density of the second ethylene copolymer portion (A2) is within the desired range, and preferably such that the melt flow rate (MFR) is within the desired range.

[0104] The first α-olefin comonomer used in the second polymerization step (b) for producing the second ethylene copolymer portion (A2) can be identical to the first α-olefin comonomer used in the first polymerization step (a) for producing the first ethylene copolymer portion (A1). This means that the first α-olefin preferably has 3 to 10 carbon atoms. In particular, the first α-olefin is preferably 1-butene, 1-hexene and 1-octene. Particularly preferably, the first α-olefin comonomer is 1-butene.

[0105] As discussed above in relation to the first polymerisation step (a), the polymerisation of the second polymerisation step (b) may be carried out in slurry in the same manner.

[0106] As discussed above in relation to the first polymerisation step (a), the polymerisation of the second polymerisation step (b) may also be carried out in gas phase in the same manner. Preferably, the second polymerisation step (b) is carried out in slurry phase as described above.

[0107] When the second polymerization step (b) is carried out as a slurry polymerization as in the first polymerization step (a), this step is carried out at a temperature in the range of 50° C. to 115° C., preferably 70° C. to 110° C., particularly 80° C. to 105° C. In this case, the pressure in the first polymerization step (a) is 1 bar to 300 bar, preferably 40 bar to 100 bar, more preferably 50 bar to 80 bar.

[0108] In the second polymerisation step (b) the molar ratio of hydrogen to ethylene is suitably from 10 to 2000 mol / kmol, preferably from 100 to 1000 mol / kmol, more preferably from 150 to 800 mol / kmol, especially from 200 to 500 mol / kmol.

[0109] 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.

[0110] The density of the second ethylene copolymer portion (A2) is controlled by the molar ratio of the first α-olefin to ethylene in the second polymerization step (b). In the second polymerization step (b), the molar ratio of the first α-olefin to ethylene is from 50 mol / kmol to 1000 mol / kmol, preferably from 200 mol / kmol to 900 mol / kmol, most preferably from 400 mol / kmol to 800 mol / kmol.

[0111] In the dimerization step (b) the polymerization rate is suitably controlled to achieve the desired amount of the second ethylene copolymer fraction (A2) in the LLDPE.

[0112] 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 1 mol-% to 10 mol-%, preferably from 2 mol-% to 6 mol-%.

[0113] As stated above, the melt flow rate MFR2 of the second ethylene copolymer fraction (A2), determined according to ISO 1133, is preferably in the range of 50 to 600 g / 10 min, more preferably in the range of 100 to 500 g / 10 min.

[0114] LLDPE-polymerization step (c)

[0115] The third ethylene copolymer fraction (B) can be produced in the third polymerization step (c) in the presence of the first ethylene polymer mixture (PEM1). Thus, the polymer obtained in the third polymerization step is the second ethylene polymer mixture (PEM2).

[0116] Ethylene, a first α-olefin comonomer, a second α-olefin comonomer, hydrogen and optionally an inert diluent may be introduced together with the first ethylene polymer mixture (PEM1) into the third polymerization step (c).

[0117] The polymerization in the third polymerization step (c) is preferably carried out in a temperature range of 50° C. to 100° C., preferably 60° C. to 100° C., particularly preferably 70° C. to 95° C. The pressure in the third polymerization step (c) is, for example, 1 bar to 300 bar, preferably 5 bar to 100 bar.

[0118] The polymerisation in the third polymerisation step (c) may be carried out in slurry. The polymerisation may then be carried out as discussed above in relation to the first polymerisation step and the second polymerisation step.

[0119] The amount of hydrogen used in the third polymerization step (c) is adjusted to achieve the desired melt flow rate for the third ethylene copolymer portion (B). 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 mol / kmol to 50 mol / kmol, preferably 3 mol / kmol to 35 mol / kmol.

[0120] In addition, the consumption of the alpha-olefin comonomer preferably having 3 to 10 carbon atoms is adjusted to reach target density.The ratio of alpha-olefin (total amount of alpha-olefin) and ethene depends on the type of catalyst and the type of alpha-olefin.This ratio is typically for example 100mol / kmol to 1000mol / kmol, is preferably 150mol / kmol to 800mol / kmol.Owing to having used more than one alpha-olefin, the ratio of alpha-olefin to ethene is the total amount of all alpha-olefins and the ratio of ethene.

[0121] The α-olefin comonomer is preferably selected from α-olefins having 3 to 10 carbon atoms or mixtures thereof. In particular, the α-olefins are preferably 1-butene, 1-hexene and 1-octene and mixtures thereof, and particularly preferably 1-butene and 1-hexene.

[0122] The content of the second α-olefin comonomer in the third ethylene copolymer fraction (B) is in the range of 15% to 85% based on the moles of the total comonomer content in the third ethylene copolymer fraction (B).

[0123] As mentioned above, the third ethylene copolymer fraction (B) preferably comprises at least two (ideally only two) comonomers. Particularly preferably, these comonomers are 1-butene and 1-hexene. That is, even more particularly preferably, the first α-olefin comonomer is 1-butene and the second α-olefin comonomer is 1-hexene, i.e., the third ethylene copolymer fraction (B) is a terpolymer, in particular an ethylene / 1-butene / 1-hexene terpolymer.

[0124] The polymerization in the third polymerization step (c) can and preferably is carried out in gas phase.In the gas phase polymerization using Ziegler-Natta catalyst, for obtaining the melt index required for the third ethylene copolymer part (B), the amount of typically adding hydrogen should make the ratio of hydrogen to ethylene, for example, be 3mol / kmol to 100mol / kmol, preferably 4mol / kmol to 50mol / kmol.The consumption of the alpha-olefin with 3 to 10 carbon atoms is adjusted, to reach the target density of the third ethylene copolymer part (B).The ratio of alpha-olefin to ethylene is generally 100mol / kmol to 1000mol / kmol, preferably 150mol / kmol to 800mol / kmol, more preferably 200 to 500mol / kmol.Owing to having used more than one alpha-olefin, the ratio of alpha-olefin to ethylene is the ratio of the total amount of all alpha-olefins to ethylene.

[0125] The gas phase reactor is preferably a vertical fluidized bed reactor. In this reactor, the polymer particles formed during polymerization are suspended in an upwardly flowing gas. The gas is introduced into the bottom of the reactor. The upwardly flowing gas passes through the fluidized bed, where a portion of the gas reacts in the presence of a catalyst, while the unreacted gas is discharged from the top of the reactor. The gas is then compressed and cooled to remove the heat of the polymerization reaction. In order to increase the cooling capacity, it is sometimes necessary to cool the circulating gas to a temperature at which a portion of the gas condenses. After cooling, the circulating gas is reintroduced into the bottom of the reactor. Fluidized bed polymerization reactors are disclosed, for example, 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.

[0126] When the first polymerization step (a) or 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 first polymerization step (a) or the second polymerization step (b) to the third polymerization step (c) as described in EP-A-1 415 999. The process described in paragraphs

[0037] to

[0048] of EP-A-1 415 999 provides a cost-effective method for product transfer.

[0127] The conditions in the third polymerization step (c) are adjusted so that the MFR2, MFR5, MFR 21 and density are within the desired ranges as described above.

[0128] The polymerization rate in the third polymerization step (c) is suitably controlled to achieve the desired amount of the third ethylene copolymer fraction (B) in the second ethylene polymer mixture (PEM2) and the LLDPE, respectively. Preferably, the final LLDPE comprises from 40 wt.% to 80 wt.%, more preferably from 50 wt.% to 70 wt.%. The polymerization rate is suitably controlled 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 from 3 mol-% to 50 mol-%, preferably from 5 mol-% to 25 mol-%.

[0129] In addition to ethylene, comonomers, and hydrogen, the gas may also include an inert gas. The inert gas may 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 thereof. Suitable hydrocarbons having 1 to 5 carbon atoms are methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, and mixtures thereof.

[0130] LLDPE-reactor post-processing

[0131] After the second ethylene polymer mixture (PEM2) has been removed from the polymerization reactor, it may be subjected to a process step for removing residual hydrocarbons from the polymer. Such processes are well known in the art and may include a decompression step, a purge step, a stripping step, an extraction step, etc. Different steps may also be combined.

[0132] According to a preferred process, at least a portion of the hydrocarbons in the polymer powder are removed by decompression. The powder is then contacted with steam at a temperature of 90°C to 110°C for 10 minutes to 3 hours. Thereafter, the powder is purged with an inert gas (e.g., nitrogen) at a temperature of 20°C to 80°C for 1 minute to 60 minutes.

[0133] According to another preferred process, the polymer powder is subjected to a decompression step as described above. Thereafter, the powder is purged with an inert gas (e.g., nitrogen) at a temperature of 50° C. 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%) of a component for deactivating the catalyst contained in the polymer, such as steam.

[0134] The purge step is preferably carried out continuously in a settled moving bed, with the polymer moving downward in plug flow while the purge gas introduced into the bottom of the bed flows upward.

[0135] 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.

[0136] As is well known in the art, after the residual hydrocarbons are removed, the polymer is preferably mixed with additives to form a polymer composition. Such additives include antiblocking agents, slip agents, processing stabilizers, antioxidants, antacids, UV protectants, nucleating agents, antistatic agents, and combinations or mixtures thereof.

[0137] As is known in the art, the polymer particles are mixed with additives and extruded into particles. A counter-rotating twin-screw extruder is preferably used in the extrusion step. Such extruders are manufactured, for example, by Kobe and Japan Steel Works. Suitable examples of such extruders are disclosed in EP-A-1600276. The specific energy input (SEI) during extrusion is typically in the range of 100 kWh / ton to 230 kWh / ton. The melt temperature is typically 220°C to 290°C.

[0138] Recycled low-density polyethylene

[0139] The polymer composition according to the invention further comprises 5 to 75 wt.-% of recycled low density polyethylene (recycled LDPE), relative to the total weight of the polymer composition.

[0140] Generally speaking, LDPE is well known in the art and is usually produced in a high pressure process in a tubular reactor or autoclave.

[0141] In the context of the present invention, the term "recycled low density polyethylene" refers to a recycled polymer material which preferably comprises at least 75 wt.-%, more preferably at least 80 wt.-%, even more preferably at least 90 wt.-% and most preferably at least 95 wt.-% of LDPE, relative to the total weight of the recycled low density polyethylene. Thus, a "recycled low density polyethylene" may comprise only at most 25 wt.-%, preferably at most 20 wt.-%, more preferably at most 10 wt.-% and most preferably at most 5 wt.-% of other (preferably recycled) polymer components, such as linear low density polyethylene (LLDPE), medium density polyethylene (MDPE) and high density polyethylene (HDPE), relative to the total weight of the recycled low density polyethylene.

[0142] Recycled polymeric material is a polymeric material recovered from waste plastic materials derived from post-consumer waste and / or industrial waste. Post-consumer waste (PCR) refers to items that have completed at least their first use cycle (or life cycle), meaning they have fulfilled their original purpose, while industrial waste refers to manufacturing waste that typically does not reach the consumer.

[0143] The opposite of recycled polymeric materials is virgin polymeric materials. Virgin polymeric materials are newly produced materials, particularly those produced from monomer units such as α-olefins. The term "virgin" refers to materials and / or articles that have been newly produced, rather than recycled, prior to their first use. A polymeric material is considered "virgin" unless its source is explicitly mentioned.

[0144] In one embodiment of the present invention, the recycled low density polyethylene (LDPE) is derived from post-consumer waste.

[0145] Preferably, the recycled low density polyethylene comprises ethylene units (C2 units) in an amount preferably of 80.0 wt.-% to 96.0 wt.-%, more preferably of 82.5 wt.-% to 95.5 wt.-%, even more preferably of 85.0 wt.-% to 95.5 wt.-%, most preferably of 87.5 wt.-% to 95.0 wt.-%.

[0146] More preferably, the recycled LDPE has an MFR2, determined according to ISO 1133, of 0.1 to 10 g / 10 min, more preferably of 0.2 to 5 g / 10 min, even more preferably of 0.3 to 1.1 g / 10 min, most preferably of 0.3 to 0.8 g / 10 min.

[0147] The density of the recycled LDPE is preferably 910 kg / m 3 Up to 945kg / m 3 , preferably 915kg / m 3 Up to 942kg / m 3 , more preferably 918 kg / m 3 Up to 940kg / m 3 , most preferably 920kg / m 3 Up to 935kg / m 3 .

[0148] The melting point (secondary melting point) of the recycled LDPE, determined according to ISO 11357, is preferably in the range of 105 to 130°C, preferably in the range of 108 to 125°C.

[0149] As recycled LDPE, NAV 101 products and CWT 100LG products supplied by Ecoplast and Borealis can be used.

[0150] In an embodiment, the content of recycled LDPE is from 10 to 70 wt.-%, preferably from 15 to 65 wt.-%, relative to the total weight of the polymer composition.

[0151] additive

[0152] Polymer composition can include one or more additives. Suitable additives are well known in the art, for example, can be selected from the group consisting of antiblocking agents, slipping agents, processing stabilizers, antioxidants, antacids, ultraviolet light protectants, nucleating agents, antistatic agents and combinations or mixtures thereof. Preferably, with respect to the gross weight of the polymer composition, the content range of the additive is 5ppm to 5000ppm, preferably 10ppm to 5000ppm, more preferably 300ppm to 3000ppm.

[0153] Anti-blocking agents help minimize the interaction of surfaces with each other through adhesion or other forces. Preferably, the anti-blocking agent comprises a compound selected from the group consisting of inorganic compounds (such as talc, kaolin, cristobalite, natural silica and synthetic silica), diatomaceous earth, mica, calcium carbonate, calcium sulfate, magnesium carbonate, magnesium sulfate and feldspar and combinations thereof.

[0154] The slip agent acts as a lubricant, for example, as a lubricant between polymers or between polymers and metals, and is used to reduce the coefficient of friction. Preferably, the slip agent comprises a compound selected from the group consisting of: fatty acid amides, such as erucamide (CAS No. 112-84-5), oleamide (CAS No. 301-02-0), or stearamide (CAS No. 124-26-5), and combinations thereof. For example, the polymer composition may include 300 ppm to 3000 ppm of erucamide.

[0155] However, in the list of optional additives, slip agents are the least preferred. It may even be advantageous if the polymer composition does not include a slip agent.

[0156] Mixtures of stabilizers and antioxidants which may be contained in the polymer composition are commercially available, for example as Irganox B225, Irganox B215 and Irganox B561 sold by BASF.

[0157] Antacids (so-called acid scavengers) are also well known in the art. Examples are calcium stearate, sodium stearate, zinc stearate, magnesium oxide, zinc oxide, synthetic hydrotalcite (e.g. SHT, CAS No. 11097-59-9), lactates, lactate esters, as well as calcium stearate (CAS No. 1592-23-0) and zinc stearate (CAS No. 557-05-1).

[0158] Examples of UV protection agents include bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (CAS No. 52829-07-9, Tinuvin 770) and 2-hydroxy-4-octyloxybenzophenone (CAS No. 1843-05-6, Chimassorb 81).

[0159] Examples of the nucleating agent include sodium benzoate (CAS No. 532-32-1) and 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (CAS 135861-56-2, Millad 3988).

[0160] Suitable antistatic agents are, for example, glycerol esters (CAS No. 97593-29-8), ethoxylated amines (CAS No. 71786-60-2 or 61791-31-9) or ethoxylated amides (CAS No. 204-393-1).

[0161] Any of the above-mentioned additives may be added during the preparation of the polymer composition, or may already be included in any of the polymers used to prepare the polymer composition.

[0162] Single-layer and multi-layer film structures

[0163] The present invention further provides a single-layer film comprising the above polymer composition, or a multi-layer film structure comprising the above polymer composition. The multi-layer film structure may be a two-layer or three-layer film structure. The film is more preferably a single-layer film.

[0164] Furthermore, the thickness of the monolayer or multilayer film structure of the present invention may be 3 μm to 1000 μm, preferably 5 μm to 500 μm, more preferably 10 μm to 250 μm, and even more preferably 10 μm to 150 μm, for example 10 μm to 100 μm, or even 10 μm to 60 μm. The most suitable thickness depends on the requirements of the desired end application.

[0165] The monolayer or multilayer film structures of the present invention can exhibit high dart impact strength (DDI) and stiffness, particularly in the machine direction (MD). The following paragraphs give preferred ranges for these parameters. These ranges are particularly applicable to blown monolayer films of 40 μm. Variations in film thickness and the construction of multilayer film structures may result in parameter changes. This does not mean that other film thicknesses are not encompassed by the present invention. Rather, it means that when formulated at a given thickness, the monolayer film produced from the polymer composition of the present invention preferably has parameter values ​​within the given ranges.

[0166] Preferably, the dart drop impact strength (DDI) of the monolayer or multilayer film structure is in the range of 100 to 450 g, preferably in the range of 150 to 350 g, measured according to ISO 7765-1 on a blown film having a thickness of 40 μm.

[0167] The monolayer or multilayer film structure may have an MD tensile modulus in the range of 220 MPa to 270 MPa and / or a TD tensile modulus in the range of 250 MPa to 350 MPa, the MD and TD tensile moduli being determined according to ISO 527-3 on blown films having a thickness of 40 μm.

[0168] In addition to excellent mechanical properties, the monolayer or multilayer film structures of the present invention may also possess beneficial optical properties.

[0169] In addition, the haze of the monolayer or multilayer film structure may be in the range of 10% to 55%, preferably in the range of 15% to 50%, measured according to ASTM D1003-00, and / or the gloss value of the monolayer or multilayer film structure may be in the range of 5.0 GU to 60.0 GU (gloss units), preferably in the range of 10.0 GU to 52.0 GU, measured at an angle of 45° on a blown film with a thickness of 40 μm according to ASTM D2457.

[0170] Overall, it has been unexpectedly discovered that the polymer compositions according to the present invention are capable of producing films having desirable optical and tensile properties, and which also exhibit significantly improved impact properties.

[0171] method

[0172] The present invention further provides a method for manufacturing the above-mentioned single-layer film or multi-layer film structure, which comprises a film blowing step.

[0173] The films of the present invention can be produced by feeding the polymer composition in granular form into an extruder. For forming films using polymer mixtures it is important that the different polymer components are thoroughly mixed before extrusion and film blowing, otherwise there is a risk of inhomogeneities appearing in the film.

[0174] Therefore, it is particularly preferred that before the components constituting the polymer composition are fed into the extruder, these components are thoroughly mixed and / or blended. For example, this can be accomplished by using a twin-screw extruder (preferably a counter-rotating extruder) before extrusion and film blowing.

[0175] Adequate homogeneity can also be achieved by selecting a film extruder screw design that allows for good mixing and homogenization.

[0176] In addition, since the film or multilayer film structure of the present invention is a blown film, the following conditions apply: blown films are typically extruded through an annular die, blown into a tubular film by forming bubbles, and produced by squeezing the bubbles by rollers after solidification. The film can then be split, cut or converted (e.g., hemming) as needed. In this regard, conventional film production techniques can be used. Typically, the composition is extruded in the temperature range of 160°C to 240°C and cooled by blowing gas (generally air) at a temperature of 10°C to 50°C to provide a frost line with a height of 1 or 2 to 8 times the diameter of the die. The blow-up ratio (BUR) should generally be in the range of 1.5 to 4 (e.g., 2 to 4), preferably in the range of 2.5 to 3.

[0177] use

[0178] The present invention further proposes the use of linear low density polyethylene (LLDPE) for the production of a monolayer film comprising recycled low density polyethylene, the LLDPE preferably being a multimodal LLDPE which is a terpolymer of ethylene and two α-olefin comonomers and has a density between 915 kg / m 3 Up to 930kg / m 3 In the range of 915kg / m 3 to less than 928kg / m 3 within the range.

[0179] Preferred properties of the LLDPE and recycled low density polyethylene are as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0180] Embodiments of the present invention are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.

[0181] Figure 1 is a plot of DDI versus MD tensile modulus for example films;

[0182] Figure 2 is a plot of DDI versus TD tensile modulus for example films;

[0183] Figure 3 is a graph of DDI versus melt pressure for example films. DETAILED DESCRIPTION

[0184] The essence of the present invention will become more apparent through the following examples, which, however, should not limit the scope of the present invention in any way.

[0185] Example

[0186] Monolayer films have been prepared from the following polymeric materials according to the film preparation procedure described below. In addition, the methods described below have been used for evaluation purposes.

[0187] method

[0188] Melt Flow Rate (MFR): MFR is measured at 190°C according to ISO 1133. The load has been indicated in subscript form, i.e. MFR2 indicates that the measurement was carried out under a load of 2.16 kg, MFR5 indicates that the measurement was carried out under a load of 5 kg, and MFR 21 Indicates that the measurement was performed under a load of 21.6 kg.

[0189] The MFR value can be measured or calculated on a sample as described above, for example, calculated from the MFR value measured on a sample as described above in a manner well known in the art. In particular, the MFR value of the third ethylene copolymer fraction (B) can be calculated based on the measured MFR value of the first ethylene polymer mixture (PEM1), the measured MFR value of the second ethylene polymer mixture (PEM2), and the respective amounts of PEM1 and the third ethylene copolymer fraction (B).

[0190] For example, the MFR value of the third ethylene copolymer fraction (B) can be calculated based on the logarithmic mixing law, for example as given by the following formula:

[0191] logMFR PEM2 =w PEM1 ×logMFR PEM1 +w B ×logMFR B

[0192] The MFR value of the second ethylene copolymer fraction (A2) can be calculated in a similar manner.

[0193] Molecular weight and molecular weight distribution: Gel permeation chromatography (GPC) was used to determine the molecular weight averages (Mn, Mw, and Mz), the Mw / Mn ratio (polydispersity index PDI), and the Mz / Mw ratio.

[0194] The molecular weight averages (Mz, Mw and Mn) and molecular weight distribution (MWD) were determined by GPC using the following formula:

[0195]

[0196] For a constant elution volume interval ΔV i , where A i and M i and elution volume V, respectively. i Correlates the chromatographic peak slice area and the polyolefin molecular weight (MW), where N is equal to the number of data points obtained between the integration limits in the chromatogram.

[0197] A high temperature GPC instrument was used, equipped with an infrared (IR) detector (IR4 or IR5 from PolymerChar, Valencia, Spain) and equipped with 3x Agilent-PLgel Olexis columns and 1x Agilent-PLgel Olexis Guard column. 1,2,4-Trichlorobenzene (TCB) stabilized with 250 mg / L of 2,6-di-tert-butyl-4-methylphenol was used as solvent and mobile phase. The chromatographic system was operated at 160° C. and a constant flow rate of 1 mL / min. 200 μL of sample solution was injected for each analysis. Data acquisition was performed using Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0198] The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow molecular weight distribution (MWD) polystyrene (PS) standards ranging from 0.5 kg / mol to 11,500 kg / mol. The PS standards were dissolved at room temperature for several hours. The conversion of peak polystyrene molecular weight to polyolefin molecular weight was accomplished using the Mark-Houwink equation and the following Mark-Houwink constant:

[0199] K PS =19×10 -3 mL / g, α PS =0.655

[0200] K PE =39×10 -3 mL / g, α PE=0.725

[0201] K PP =19×10 -3 mL / g, α PP =0.725

[0202] A third-order polynomial fit was used to fit the calibration data.

[0203] All samples were prepared in the concentration range of 0.5-1 mg / ml and dissolved at 160°C with continuous gentle shaking for 3 hours.

[0204] Comonomer content - quantitative 13 C-NMR spectral analysis

[0205] Quantitative analysis of microstructure by quantitative nuclear magnetic resonance (NMR) spectroscopy

[0206] Quantitative nuclear magnetic resonance (NMR) spectroscopy was used to quantitatively analyze the comonomer content of the polymers.

[0207] Quantitative measurements were recorded in the melt using a Bruker Avance III 500 NMR spectrometer. 13 C{1H}NMR spectra were performed on a spectrometer operating at 500.13 MHz for 1H and 125.76 MHz for 13C. 13 Recordings were made at 150°C using a C-optimized 7 mm magic-angle spinning (MAS) probehead, with nitrogen used for all pneumatics. Approximately 200 mg of material was packed into a 7 mm outer diameter zirconium oxide MAS rotor and spun at 4 kHz. This setup was chosen primarily to meet the high sensitivity required for rapid identification and accurate quantification {klimke06, parkinson07, castignolles09}. Standard single-pulse excitation was used, exploiting the Nuclear Overhauser effect (NOE) with a short recycle delay of 3 s {pollard04, klimke06}, and an RS-HEPT decoupling scheme {fillip05, griffin07}. A total of 1024 (1k) transients were acquired for each spectrum.

[0208] Quantitative 13 C{1H} NMR spectra were processed and integrated, and the relevant quantitative properties were determined based on the integrated values. All chemical shifts were referenced to the main methylene signal (δ+) at 30.00 ppm as an internal standard and assigned according to {randall89}.

[0209] The amount of ethylene used was quantified by integrating the methylene (δ+) sites at 30.00 ppm, which takes into account the number of reported sites for each monomer:

[0210] E=I δ+ / 2

[0211] Characteristic signals arising from saturated end groups were observed. The content of such saturated end groups was quantified by averaging the integrals of the signals at 22.8 ppm [I2S] and 32.2 ppm [I3S], which are assigned to the 2s and 3s sites, respectively:

[0212] S=(1 / 2)×(I2S+I3S)

[0213] Correction for the presence of comonomer units is made based on the number of comonomer units and saturated end groups present:

[0214] E 总 =E+(3 / 2)×B+(3 / 2)×BB+(5 / 2)×BEB+(2 / 2)×H+(3 / 2)×S

[0215] B and H are defined for their respective comonomers. Corrections will be made in a similar manner when there are cases of continuous and discontinuous comonomer incorporation.

[0216] A characteristic signal corresponding to 1-butene incorporation was observed, and the comonomer fraction was calculated as the fraction of 1-butene in the polymer relative to all monomers in the polymer.

[0217] The amount of free 1-butene incorporated into the EEBEE sequence was quantified using the integral value of the *B2 site at 39.9 ppm, which takes into account the number of reporting sites for each comonomer:

[0218] B=I×B2

[0219] If present, the amount of continuously incorporated 1-butene in the EEBBEE sequence is quantified using the integral value of the ααB2B2 site at 39.4 ppm, which takes into account the number of reporting sites for each comonomer:

[0220] BB=2×IααB2B2

[0221] If present, the amount of non-continuously incorporated 1-butene in the EEBEBEE sequence is quantified using the integral value of the ββB2B2 site at 24.8 ppm, which takes into account the number of reporting sites for each comonomer:

[0222] BEB=2×IββB2B2

[0223] Since there is overlap between the *B2 sites of free (EEBEE)1-butene and the *βB2B2 sites of discontinuously incorporated (EEBEBEE)1-butene, the total amount of free 1-butene incorporated was corrected for the amount of discontinuous 1-butene present:

[0224] B=I×B2-2×IββB2B2

[0225] No BBB sequence was observed. The total 1-butene content was calculated based on the sum of free, continuously incorporated, and discontinuously incorporated 1-butene:

[0226] B 总 =B+BB+BEB

[0227] Then, calculate the mole fraction of 1-butene in the polymer:

[0228] fB=B 总 / (E 总 +B 总 +H 总 )

[0229] A characteristic signal corresponding to 1-hexene incorporation was observed, and the comonomer fraction was calculated as the fraction of 1-hexene in the polymer relative to all monomers in the polymer.

[0230] The amount of free 1-hexene incorporated into the EEHEE sequence was quantified using the integral value of the *B4 site at 38.3 ppm, which takes into account the number of reporting sites for each comonomer:

[0231] H=I×B4

[0232] The total 1-hexene content is calculated based only on free incorporated 1-hexene:

[0233] H 总 =H

[0234] Then, calculate the mole fraction of 1-hexene in the polymer:

[0235] fH=H 总 / (E 总 +B 总 +H 总 )

[0236] Calculate the mole percent comonomer incorporation based on the mole fraction:

[0237] B[mol-%]=100×fB

[0238] H[mol-%]=100×fH

[0239] Calculate the weight percent comonomer incorporation based on the mole fraction:

[0240] B[wt%]=100×(fB×56.11) / ((fB×56.11)+(fH×84.16)+((1-(fB+fH))×28.05))

[0241] H[wt%]=100×(fH×84.16) / ((fB×56.11)+(fH×84.16)+((1-(fB+fH))×28.05))

[0242] Further details of this method can be found in: J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201; Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2006; 207: 382; Parkinson, M., Klimke, K., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2007; 208: 2128; Pollard, M., Klimke, K., Graf, R., Spiess, HW, Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004;37:813; Filip, 45, S1, S198; Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373.

[0243] Density: Density was measured according to ISO 1183-187. Sample preparation was done by compression molding according to ISO 1872-2:2007. In cases where the density of a specific part could not be directly measured, it was calculated using the linear mixing rule.

[0244] Tensile modulus: Tensile modulus was measured according to ISO 527-3 on blown film samples with a film thickness of 40 μm prepared as described below under “Film sample preparation” at a crosshead speed of 1 mm / min in the machine direction (MD) and transverse direction (TD).

[0245] Dart Drop Impact Strength (DDI): The dart drop impact strength (DDI) was measured using ISO 7765-1 on blown film samples with a thickness of 40 μm.

[0246] Haze: Haze was measured according to ASTM D1003-00 on blown films having a thickness of 40 μm produced as described below.

[0247] Gloss: Gloss was measured according to ASTM D2457 at an angle of 45° in the MD direction on a blown film having a thickness of 40 μm.

[0248] Melt pressure: During blown film production, the melt pressure is measured directly by a pressure sensor (eg, Dynisco pressure sensor) located at the end of the extruder (roughly corresponding to the final section of the screw).

[0249] polymer materials

[0250] Three types of polymer materials have been produced.

[0251] The first type of polymeric material includes a polymeric composition comprising a linear low-density polyethylene (which is a terpolymer of ethylene and two α-olefin comonomers) and a recycled low-density polyethylene ("LLDPE terpolymer + PCR"). The second type of polymeric material is the aforementioned linear low-density polyethylene ("LLDPE terpolymer only"). The third type of polymeric material is a linear low-density polyethylene LLDPE containing only one comonomer ("LLDPE copolymer only"). The first type of polymeric material is a polymeric composition according to the present invention, while the second and third types of polymeric materials are comparative materials.

[0252] Table 1 below gives a summary of the composition of each polymer material.

[0253] Table 1

[0254]

[0255]

[0256] In addition, the specifications of each component are listed in Table 2 below:

[0257] Table 2

[0258]

[0259] LLDPE components have been produced using:

[0260] LLDPE terpolymer

[0261] Volume is 50dm 3 A loop reactor was operated at a temperature of 70°C and a pressure of 57 bar. Ethylene, propane diluent, and hydrogen were fed to the reactor at a feed rate of 2.0 kg / h of ethylene, 109 g / h of 1-butene, and 5 g / h of hydrogen. Furthermore, a solid polymerization catalyst component, produced as described in Example 1 of EP 1378528, was introduced into the reactor along with triethylaluminum cocatalyst to achieve an Al / Ti molar ratio of approximately 15. The estimated yield ratio was approximately 1.4 wt.%.

[0262] The slurry flow is continuously drawn out and poured into a 150dm 3 The reactor was further fed with additional ethylene, 1-butene comonomer, propane diluent, and hydrogen to a fluid mixture concentration of 6.0 mol%, a hydrogen to ethylene ratio of 283 mol / kmol, a 1-butene to ethylene ratio of 203 mol / kmol, and a fresh propane (diluent) feed rate of 72.4 kg / h. The estimated production ratio was 14.5 wt.-%. The resulting copolymer had an MFR2 of 177 g / 10 min and a density of 949 kg / m 3 .

[0263] The slurry flow was intermittently withdrawn from the reactor and fed into a 350 dm 3 The reactor was further fed with fresh propane, ethylene, 1-butene comonomer, and hydrogen to a reaction mixture having an ethylene concentration of 3.5 mol%, a hydrogen to ethylene molar ratio of 289 mol / kmol, and a 1-butene to ethylene molar ratio of 614 mol / kmol. The ethylene copolymer withdrawn from the reactor had an MFR2 of 258 g / 10 min and a density of 951 kg / m 3 The estimated production mix is ​​23.5 wt.-%.

[0264] The slurry was intermittently withdrawn from the loop reactor and fed into a flash vessel operated at a temperature of 50° C. and a pressure of 3 bar. Subsequently, the polymer was fed into a fluidized bed gas phase reactor operated at a pressure of 20 bar and a temperature of 80° C. Additional ethylene, 1-butene comonomer, 1-hexene comonomer, nitrogen (as an inert gas), and hydrogen were added to the reactor to give an ethylene content of 19.3 mol%, a hydrogen to ethylene molar ratio of 10.2 mol / kmol, a 1-butene to ethylene molar ratio of 92.8 mol / kmol, and a 1-hexene to ethylene molar ratio of 138.7 mol / kmol in the reaction mixture. The polymer yield in the gas phase reactor was 60.6 wt.%.

[0265] The polymer powder was mixed with 1200 ppm of Irganox B561 and 400 ppm of calcium stearate under a nitrogen atmosphere, and then kneaded and extruded into pellets using a JSW CIMP90 twin-screw extruder under a nitrogen atmosphere.

[0266] LLDPE copolymer

[0267] LLDPE copolymers were produced in the same manner as the LLDPE terpolymers, except that the reaction conditions were changed as shown in Table 3 below.

[0268] Table 3

[0269]

[0270]

[0271]

[0272] Table 4 provides the properties of the LLDPE components.

[0273] Table 4**

[0274] LLDPE terpolymer LLDPE copolymer PEM1 <![CDATA[MFR2,g / 10min]]> 258 274 <![CDATA[Density, kg / m 3 > 951 951 Ratio, wt.-% 39.4 39.3 Mw, kg / mol 28.25 27.95 C4, mol-% 1.2 1.1 PEM2 (granules) <![CDATA[MFR2]]> 0.22 0.28 <![CDATA[Density, kg / m 3 > 922.6 920.7 Mw, kg / mol 172.5 171.5 C4, mol-% 1.1 4.7 C6, mol-% 2.2 0 Section B* <![CDATA[MFR2,g / 10min]]> 0.0057 0.0074 <![CDATA[Density, kg / m 3 > 904.1 901.1 Ratio, wt.-% 60.6 60.7 Mw, kg / mol 266.6 264.4 C4 concentration, mol-% 1.02 7.03 C6 concentration, mol-% 3.61 0 (C4+C6), mol-% 4.64 7.03 B C6 / (C4+C6), in mol, % 77.9 0

[0275] *To calculate the properties of fraction B, the PEM1 fraction was collected and analyzed. This enabled the calculation of the properties of the third ethylene copolymer fraction B, more specifically the contents of the two comonomers and their relative ratios. The linear mixing rule was used to calculate the comonomer content and density; the logarithmic mixing rule was used to calculate the MFR2 value of fraction B.

[0276] **Table 4 does not indicate the properties of the second ethylene copolymer fraction A2. However, these properties can be calculated in a manner similar to the values ​​for fraction B. That is, the PEM1 and A1 fractions were collected and analyzed. Density was calculated using the linear rule of mixing; the MFR2 value for fraction A2 was calculated using the logarithmic rule of mixing.

[0277] Membrane preparation procedure

[0278] The polymer materials IE1, IE2, IE3, CE1 and CE2 were converted into monolayer films on a small laboratory blown film line from COLLIN Lab&Pilot Solutions GmbH.

[0279] The production line consists of a screw diameter The extruder consists of an extruder with a diameter of 30 mm and a length-to-diameter ratio (L / D) of 30. The extruder temperature was set at 200°C and the melt temperature was 202°C, and the melt temperature was recorded after the process stabilized for 45 minutes. The extruder was followed by a blow molding head equipped with a diameter The die was annular and had a 60 mm diameter and a 1.5 mm die gap. The line operated at a constant line speed of 7.5 m / min. The bubble had a blow-up ratio (BUR) of 2.5:1 and a frost line height of 120 mm. The film produced had a thickness of 40 μm.

[0280] Membrane sample preparation

[0281] The blown film was wound into a roll and then cut into corresponding sizes for further testing. The test results are shown in Table 5 below.

[0282] Table 5

[0283] IE1 IE2 IE3 CE1 CE2 MD tensile modulus / MPa 257.5 238.1 224.5 262.2 238.7 TD tensile modulus / MPa 340.7 302.8 262.4 340.2 306.2 DDI / g 260 194 192 430 238 Haze / % 47.7 18.7 16.1 73.2 76.4 Gloss 45°MD 12.7 41.1 50.7 6.3 5.7 Melt pressure at 200°C / bar 299 269 315 315 284

[0284] From the results in Table 5, it can be inferred that the polymer compositions IE1-IE3 of the present invention are comparable to the compositions in comparative examples CE1 and CE2, and are even superior in some aspects:

[0285] Overall, the blown films produced using the polymer compositions of the present invention exhibit desirable mechanical properties, particularly a good balance between stiffness (tensile modulus) and toughness (DDI). At the same time, the optical properties of the blown films produced from the polymer compositions of the present invention are improved compared to those produced from comparative polymer compositions. Blown films produced from the polymer compositions of the present invention exhibit significantly lower haze values ​​and higher gloss values. Furthermore, processing conditions are not negatively impacted when switching from comparative compositions to the compositions of the present invention. More specifically, the polymer compositions of the present invention can be processed at 200°C and at melt pressures of the same order of magnitude as the comparative polymer compositions.

[0286] also, Figure 1-3 The charts in provide a visual overview of the results.

[0287] Attached photos

[0288] Figure 1 This figure shows how the balance between stiffness (MD tensile modulus) and toughness (Dart drop impact strength, DDI) changes for the inventive and comparative examples. The ratio of DDI to MD tensile modulus for films IE1-IE3 (including PCR) is significantly worse than for film CE1 (made solely from virgin polymer). However, the DDI-tensile modulus combination for IE2 is nearly identical to that for CE2 (produced using virgin LLDPE polymer). Increasing the PCR fraction to 60 wt.% (i.e., from IE2 to IE3) shows only a slight decrease in tensile properties, while the DDI remains at the same level.

[0289] Figure 2 Similar conclusions can be drawn for the combination of DDI and transverse direction tensile modulus values.

[0290] Therefore, it can be concluded that using a blend of virgin and recycled polymer materials can produce membranes with an excellent stiffness-toughness balance (comparable to that provided by some virgin materials). This provides an opportunity to provide membranes with a lower CO2 footprint.

[0291] Figure 3 It was demonstrated that the incorporation of recycled polymeric materials also had no negative impact on processing conditions such as melt pressure, which can be said to be related to rheological properties. More specifically, Figure 3 The ratio of DDI to melt pressure for film CE2 produced using virgin material is shown to be between the ratios of DDI to melt pressure for films containing 20-40% PCR (IE1 and IE2). Therefore, the output of the production line is not affected when using a mixture of virgin and recycled polymer materials to produce films.

Claims

1. A polymer composition, characterized in that The polymer composition comprises: 25 wt.-% to 95 wt.-% of linear low-density polyethylene and 5 wt.-% to 75 wt.-% of recycled low-density polyethylene, relative to the total weight of the polymer composition, The linear low-density polyethylene is a terpolymer of ethylene and two α-olefin comonomers, and the density of the linear low-density polyethylene is 915 kg / m 3 and above up to 928kg / m 3 Within the following range.

2. The polymer composition according to claim 1, characterized in that The linear low density polyethylene is multimodal.

3. The polymer composition according to any one of claims 1 and 2, characterized in that The polymer composition has an MFR2 measured according to ISO 1133 in the range of 0.05 g / 10 min to 5.0 g / 10 min, preferably in the range of 0.1 g / 10 min to 1.0 g / 10 min, more preferably in the range of 0.2 g / 10 min to 0.6 g / 10 min, and / or a density measured according to ISO 1183 in the range of 920 kg / m 3 and above up to 935kg / m 3 Within the following range.

4. The polymer composition according to any one of the preceding claims, characterized in that The MFR2 of the linear low density polyethylene is in the range of 0.01 g / 10min to 0.5 g / 10min, preferably in the range of 0.1 g / 10min to 0.4 g / 10min, more preferably in the range of 0.15 g / 10min to 0.3 g / 10min, and / or the MFR5 of the linear low density polyethylene is in the range of 0.5 g / 10min to 5.0 g / 10min, preferably in the range of 0.6 g / 10min to 2.0 g / 10min, more preferably in the range of 0.7 g / 10min to 1.5 g / 10min, wherein the MFR2 and the MFR5 are determined according to ISO 1133.

5. The polymer composition according to any one of the preceding claims, characterized in that The two α-olefin comonomers are selected from the group of α-olefins having 3 to 10 carbon atoms, in particular 1-butene and 1-hexene.

6. The polymer composition according to any one of the preceding claims, characterized in that The linear low-density polyethylene has: - a number average molecular weight (Mn) in the range of 8,000 g / mol to 14,000 g / mol, preferably in the range of 9,000 g / mol to 12,000 g / mol; - a weight average molecular weight (Mw) in the range of 150,000 g / mol to 200,000 g / mol, preferably in the range of 160,000 g / mol to less than 190,000 g / mol; - z-average molecular weight (Mz) in the range of 750,000 g / mol to 1,000,000 g / mol, preferably in the range of 800,000 g / mol to 920,000 g / mol; - a Mw / Mn ratio in the range of 10 to 25; and / or -Mz / Mw ratio is in the range of 4 to 10, The molecular weight averages Mw, Mn and Mz are measured by gel permeation chromatography.

7. The polymer composition according to any one of the preceding claims, characterized in that The linear low density polyethylene comprises: - 5 to 25 wt.-% of a first ethylene copolymer fraction (A1), relative to the total weight of the linear low density polyethylene, said A1 consisting of a copolymer of ethylene and at least a first α-olefin comonomer, said A1 preferably having a density of 920 kg / m2, measured according to ISO 1183 3 Up to 960kg / m 3 within the scope of - 15 wt.-% to 35 wt.-% of a second ethylene copolymer fraction (A2), relative to the total weight of the linear low density polyethylene, said A2 consisting of a copolymer of ethylene and at least said first α-olefin comonomer, said A2 preferably having a density of 920 kg / m², measured according to ISO 1183 3 Up to 960kg / m 3 to the extent that - 40 wt.-% to 80 wt.-% of a third ethylene copolymer fraction (B), relative to the total weight of the linear low density polyethylene, said B consisting of a polymer of ethylene with at least the first and second α-olefin comonomers, The weight average molecular weight (Mw) of the third ethylene copolymer portion (B) is preferably higher than the weight average molecular weight (Mw) of the first ethylene copolymer portion (A1) and the second ethylene copolymer portion (A2).

8. The polymer composition according to claim 7, characterized in that According to quantitative 13 The content of the second α-olefin comonomer in the third ethylene copolymer fraction (B) is in the range of 15% to 85% based on the moles of the total comonomer content in the third ethylene copolymer fraction as determined by C-NMR spectroscopy.

9. The polymer composition according to any one of the preceding claims, characterized in that According to quantitative 13 The linear low density polyethylene has a total comonomer content in the range of 1.5 mol-% to 5.0 mol-%, preferably in the range of 2.5 mol-% to 3.9 mol-%, as determined by C-NMR spectral analysis.

10. A monolayer film comprising the polymer composition according to any one of the preceding claims, or a multilayer film structure comprising the polymer composition according to any one of the preceding claims.

11. The single-layer or multi-layer film structure according to claim 10, characterized in that: The dart drop impact strength (DDI) of the monolayer or multilayer film structure is in the range of 100 g to 450 g, preferably in the range of 150 g to 350 g, measured according to ISO 7765-1 on a blown film having a thickness of 40 μm.

12. The single-layer or multi-layer film structure according to any one of claims 10 and 11, characterized in that The monolayer film or multilayer film structure has a machine direction (MD) tensile modulus in the range of 220 MPa to 270 MPa and / or a transverse direction (TD) tensile modulus in the range of 250 MPa to 350 MPa, wherein the machine direction tensile modulus and the transverse direction tensile modulus are determined according to ISO 527-3 on a blown film having a thickness of 40 μm.

13. The single-layer or multi-layer film structure according to any one of claims 10 to 12, characterized in that: The haze of the monolayer or multilayer film structure is in the range of 10% to 55%, preferably in the range of 15% to 50%, measured according to ASTM D1003-00, and / or the gloss value of the monolayer or multilayer film structure is in the range of 5.0 GU to 60.0 GU, preferably in the range of 10.0 GU to 52.0 GU, measured at an angle of 45° on a blown film having a thickness of 40 μm according to ASTM D2457.

14. A method for manufacturing a single-layer film or a multi-layer film structure according to any one of claims 10 to 13, characterized in that: The method comprises a film blowing step.

15. A use of linear low-density polyethylene, characterized in that: The linear low density polyethylene is preferably a multimodal linear low density polyethylene, which is a terpolymer of ethylene and two α-olefin comonomers with a density of 915 kg / m 3 Up to 930kg / m 3 range, and is used to manufacture monolayer films comprising recycled low-density polyethylene.

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