Polypropylene composition with improved low temperature impact performance

Abstract

The invention relates to a composition comprising a heterophasic polypropylene and a linear low density polyethylene, a process for obtaining the composition, the linear low density polyethylene, use of the linear low density polyethylene, and an article comprising the composition.

Description

[0001] Polypropylene composition with improved low temperature impact performance

[0002] Field of the invention

[0003] The invention relates to a composition comprising a heterophasic polypropylene and a linear low density polyethylene, a process for obtaining the composition, the linear low density polyethylene, use of the linear low density polyethylene, and an article comprising the composition.

[0004] Technical background

[0005] Providing a material with good balance of stiffness and impact performance is a constant need in many business segments. Especially in the automotive industry there is a constant need for materials with good impact performance.

[0006] However, designing a polypropylene material having reasonable stiffness, good thermo-mechanical properties (high Tm) and high impact performance especially at low temperatures is not trivial.

[0007] Increasing the ethylene content and intrinsic viscosity of the dispersed phase of heterophasic propylene copolymers are common ways to achieve such a performance profile. However, increasing the ethylene content of the dispersed phase in a heterophasic polypropylene is typically not sufficient to significantly increase the low temperature impact performance since the resulting ethylene-propylene copolymers still show reduced mobility at low temperatures (high glass transition temperatures Tg). A possibility to overcome this problem is to add polyethylene or elastomers directly to a heterophasic polypropylene. However, in order to see a significant improvement of the properties, the required amounts of these substances are normally rather high, leading to negative influences on other properties like dimensional stability, stiffness or flowability.

[0008] Therefore, developing materials combining good stiffness, reasonable flow, high melting temperature and good low temperature impact performance are not trivial to achieve. It was now surprisingly found that by designing a composition comprising a heterophasic polypropylene and a linear low density polyethylene, and having a medium ethylene-content of the soluble fraction and specific intrinsic viscosity ratio between the soluble and the crystalline fraction leads inter alia to very good CLTE values combined with very high notched Charpy impact strength at room as well as at low temperatures and good elongation at break, showing a good balance of desirable properties.

[0009] Summary of the invention

[0010] In a first aspect, the invention refers to a composition comprising i) a heterophasic polypropylene; and ii) a linear low density polyethylene (LLDPE); in a combined amount of more than 85.0 wt.-%, preferably in the range of 90.0 to 99.5 wt.-%, based on the total weight of the composition; characterized in that the composition has a total content of units derived from ethylene (C2) in the range of 15.0 wt.-% to 35 wt.-%, preferably in the range of 16.0 to 30.0 wt.-%, more preferably of 18.0 to 28.0 wt.-%, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy; a soluble fraction (SF) and a crystalline fraction (CF) according to crystallisation extraction analysis (CRYSTEX); a soluble fraction (SF) content determined by crystallisation extraction analysis (CRYSTEX) in the range of from 25.0 wt.-% to 45.0 wt.-%, preferably from 28.0 to 42.0 wt.-%, more preferably from 30.0 to 40.0 wt.-%; an ethylene content of said soluble fraction C2(SF), as determined by FT- IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, in the range of from 28.0 to 48.0 wt.-%, preferably from 30.0 to 45.0 wt.-%, more preferably from 32.0 to 42.0 wt.-%; a ratio (iV(SF) / iV(CF)) of the intrinsic viscosity of said soluble fraction iV(SF) to the intrinsic viscosity of the crystalline fraction iV(CF) in the range of from 1.7 to 3.0, preferably in the range of from 1.8 to 2.8, more preferably of from 2.0 to 2.6, wherein the intrinsic viscosities are determined by crystallisation extraction analysis (CRYSTEX).

[0011] In another aspect, the invention refers to a process for obtaining the composition as described above or below, comprising the steps of a) polymerizing a polypropylene homopolymer (H-PP) and an ethylenepropylene copolymer (EPC) successively in the presence of a Ziegler- Natta catalyst system in a multistage process comprising at least two polymerization reactors connected in series, thereby obtaining a heterophasic polypropylene; b) melt-blending the heterophasic polypropylene obtained in step a) with the linear low density polyethylene (LLDPE) and optional additives.

[0012] In a further aspect, the invention refers to a linear low density polyethylene (LLDPE), characterized in that the LLDPE has

[0013] - a MFR2(190°C, 2.16 kg, ISO 1133) in the range of 200 to 500 g / 10 min, preferably of 210 to 450 g / 10 min, more preferably of 220 to 400 g / 10 min; a melting temperature Tm, determined by differential scanning calorimetry (DSC) according to ISO 11357 / part 3 / method C2, in the range of 113 to 127 °C, preferably of 115 to 125 °C, more preferably of 117 to 123 °C; and a density, measured according to ISO 1183-1 :2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 935 to 950 kg / m3, preferably 938 to 947 kgm3, more preferably 940 to 946 kg / m3. In another aspect, the invention relates to a use of the linear low density polyethylene (LLDPE) as described above or below, for improving the impact strength at low temperatures of heterophasic polypropylenes as specified above or below.

[0014] In a further aspect, the invention relates to an article, preferably an automotive article comprising, preferably consisting of the composition as described above or below.

[0015] Detailed description of the invention

[0016] Composition

[0017] The composition of the present invention comprises i) a heterophasic polypropylene; and ii) a linear low density polyethylene (LLDPE); in a combined amount of more than 85.0 wt.-%, preferably in the range of 90.0 to 99.5 wt.-%, based on the total weight of the composition.

[0018] In this disclosure, a heterophasic polypropylene is a polyolefin, in which at least 50.0 wt.-% of the total units of the polymeric components are derived from propylene and that due to its heterophasic nature possesses a matrix phase and a dispersed phase.

[0019] It was found that by carefully designing the parameters of the composition, a good balance of mechanical properties can be achieved with a surprisingly high notched Charpy impact strength at low temperatures.

[0020] Accordingly, the composition has a total content of units derived from ethylene (C2) in the range of 15.0 wt.-% to 35 wt.-%, preferably in the range of 16.0 to 30.0 wt.-%, more preferably of 18.0 to 28.0 wt.-%, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy.

[0021] The term heterophasic describes the presence of a matrix phase, which is mainly composed of crystalline polymers and of a dispersed phase, which is mainly composed of amorphous polymers such as elastomeric ethyl ene-propylene copolymers (EPC).

[0022] Since the composition comprises a heterophasic polypropylene and a linear low density polyethylene (LLDPE), the composition contains crystalline and amorphous polymeric components.

[0023] One method to analyse the amount and the properties of the crystalline and amorphous polymeric components is the crystallization extraction (CRYSTEX) method. This method is described below in the determination methods section. Thereby, the polymeric part of the composition is characterized using tri chlorobenzene (TCB) as a solvent. The obtained crystalline fraction (CF) consists essentially of the majority of the matrix phase, the crystalline part of the LLDPE and, if present, the crystalline part of the dispersed phase, while the obtained soluble fraction (SF) consists essentially of the majority of the dispersed phase, the amorphous part of the LLDPE and, if present, the amorphous part of the matrix phase. Due to the differences in the separation methods of xylene extraction and crystallization extraction (CRYSTEX) the properties of XCS / XCI fractions on the one hand and crystalline / soluble (CF / SF) fractions on the other hand are not exactly the same, meaning that the amounts can differ as well as the properties.

[0024] Generally, the crystalline fraction (CF) content and the soluble fraction (SF) content of a composition only relate to its polymeric components, i.e. without other components, which are insoluble and therefore not part of the dissolution and crystallization cycles as described below in the determination method.

[0025] The crystalline and amorphous polymeric parts present in the composition of the invention are characterized by the crystallization extraction (CRYSTEX) method. The composition has a soluble fraction (SF) content determined by crystallisation extraction analysis (CRYSTEX) in the range of from 25.0 wt.-% to 45.0 wt.-%, preferably from 28.0 to 42.0 wt.-%, more preferably from 30.0 to 40.0 wt.-%.

[0026] Further, the ethylene content of said soluble fraction C2(SF), as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, is in the range of from 28.0 to 48.0 wt.-%, preferably from 30.0 to 45.0 wt.-%, more preferably from 32.0 to 42.0 wt.-%.

[0027] The ratio of the intrinsic viscosity of the soluble fraction iV(SF) to the intrinsic viscosity of the crystalline fraction iV(CF) influences the mechanical properties. For this invention it was found that when the iV(SF) is around twice as high as the iV(CF), a very good balance of mechanical properties can be achieved.

[0028] Accordingly, the ratio (iV(SF) / iV(CF)) of the intrinsic viscosity of the soluble fraction iV(SF) to the intrinsic viscosity of the crystalline fraction iV(CF) is in the range of from 1.7 to 3.0, preferably in the range of from 1.8 to 2.8, more preferably from 2.0 to 2.6, wherein the intrinsic viscosities are determined by crystallisation extraction analysis (CRYSTEX).

[0029] Preferably, the MFR2 (230°C, 2.16 kg, ISO 1133) of the composition is in the range of 5 to 25 g / 10 min, more preferably 6 to 20 g / 10 min, yet more preferably 7 to 15 g / 10 min.

[0030] It is preferred, that the crystalline fraction (CF) content determined by crystallisation extraction analysis (CRYSTEX) is in the range of from 55.0 wt.-% to 75.0 wt.-%, preferably from 58.0 to 72.0 wt.-%, more preferably from 60.0 to 70.0 wt.-%.

[0031] Due to the nature of the crystallisation extraction analysis (CRYSTEX), the combined amount of soluble fraction (SF) content and crystalline fraction (CF) content adds up to 100 wt.-% of the polymeric components. The ethylene content of said crystalline fraction C2(CF), as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, is preferably in the range of from 8.0 to 25.0 wt.-%, more preferably from 9.0 to 23.0 wt.-%, yet more preferably from 10.0 to 21.0 wt.-%.

[0032] The intrinsic viscosity (iV), determined according to ISO 1628-3, of the composition is preferably in the range of 1.5 to 3.0 dl / g, more preferably of 1.7 to 2.7 dl / g, more preferably of 1.8 to 3.5 dl / g.

[0033] The crystalline portion of the polymer components can be further characterised by analysing the crystalline fraction (CF) by differential scanning calorimetry (DSC). This method can provide the melting point of the crystalline portion of the polymer components. Crystalline fractions (CF) having two distinct melting points Tm,i and Tm,2 indicate that there are two different crystalline polymeric components present.

[0034] It is preferred that the crystalline fraction (CF) has two melting points Tm,i and Tm,2, determined by differential scanning calorimetry (DSC) according to ISO 11357 / part 3 / method C2.

[0035] In this embodiment, the Tm,i preferably is in the range of 113 to 127 °C, more preferably 115 to 125 °C, yet more preferably 117 to 123 °C and the Tm,2 is preferably in the range of 160 to 170 °C, more preferably of 162 to 168 °C, yet more preferably of 163 to 167 °C.

[0036] In the following, mechanical properties and relationships of mechanical and intrinsic properties are described, which can also be used to characterize the inventive composition.

[0037] Preferably, the numerical values of the notched Charpy impact strength (NIS), determined according to ISO 179-1 / leA on notched 80 * 10 ^ 4 mm3specimens (specimens were prepared according to ISO 179-1 / leA), at -20 °C in kJ / m2of the composition and the soluble fraction (SF) content of the composition, determined by crystallisation extraction analysis (CRYSTEX), in wt.-% fulfil the following relation:

[0038] NIS (— 20°C) > SF.

[0039] This relation indicates that the inventive compositions have a high impact strength at low temperatures without having to comprise a large amount of elastomeric polymer components.

[0040] It is also preferred, that the composition has a Tensile modulus, determined according to ISO 527-2 (cross head speed for modulus = 1 mm / min; test speed to break 50 mm / min at 23 °C) using injection molded specimens IB prepared as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness), of more than 650 MPa, preferably in the range of 680 to 850 MPa, more preferably of 700 to 820 MPa. In the following, the polymeric components of the composition are described in more detail.

[0041] LLDPE

[0042] The composition comprises a heterophasic polypropylene and a linear low density polyethylene (LLDPE).

[0043] It is preferred, that the LLDPE is a copolymer of ethylene and butene.

[0044] In this embodiment, it is preferred that the LLDPE has a total content of units derived from butene (C4) in the range of 0.5 to 10.0 wt.-%, preferably 1.0 to 8.0 wt.- %, more preferably 2.0 to 5.0 wt.-%, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy.

[0045] Further, the LLDPE preferably has a density, measured according to ISO 1183- 1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 935 to 950 kg / m3, preferably of 938 to 947 kgm3, more preferably of 940 to 946 kg / m3. Preferably, the melting point Tmof the LLDPE, determined by differential scanning calorimetry (DSC) according to ISO 11357 / part 3 / method C2, is in the range of 113 to 127 °C, more preferably 115 to 125 °C, yet more preferably 117 to 123 °C.

[0046] In this embodiment, the melting point Tmof the LLDPE corresponds to the first melting point Tm,i of the composition, thereby indicating that the LLDPE is mainly crystalline and present in the crystalline fraction (CF) of the composition.

[0047] Preferably, the MFR2 (190°C, 2.16 kg, ISO 1133) of the LLDPE is in the range of 50 to 500 g / 10 min, such as 200 to 500 g / 10 min, more preferably of 80 to 450 g / 10 min, such as 210 to 450 g / 10 min, yet more preferably of 100 to 400 g / 10 min, such as 220 to 400 g / 10 min.

[0048] It is also preferred that the intrinsic viscosity of the LLDPE (1VLLDPE), determined according to ISO 1628-3, is in the range of 0.50 to 1.50 dl / g, more preferably of 0.55 to 1.20 dl / g, yet more preferably of 0.60 to 1.00 dl / g.

[0049] Heterophasic polypropylene

[0050] Besides the LLDPE, the composition comprises also a heterophasic polypropylene.

[0051] In a preferred embodiment, the heterophasic polypropylene comprises

[0052] A) a crystalline polypropylene homopolymer (H-PP), and

[0053] B) an elastomeric ethylene propylene copolymer (EPC).

[0054] In this embodiment, the heterophasic polypropylene preferably has a total content of units derived from ethylene (C2) in the range of 10.0 to 30.0 wt.- %, more preferably in the range of 12.0 to 28.0 wt.-%, yet more preferably of 15.0 to 25.0 wt.-%, as determined by FT-IR spectroscopy calibrated by quantitative13C- NMR spectroscopy. Further, the soluble fraction (SF) content of the heterophasic polypropylene, determined by crystallisation extraction analysis (CRYSTEX) is preferably in the range of from 25.0 to 45.0 wt.-%, more preferably from 27.0 to 43.0 wt.-%, yet more preferably from 29.0 to 41.0 wt.-%.

[0055] The ethylene content of said soluble fraction C2(SF), as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, is preferably in the range of from 30.0 to 52.0 wt.-%, more preferably from 32.0 to 48.0 wt.-%, yet more preferably from 34.0 to 44.0 wt.-%.

[0056] Preferably, the heterophasic polypropylene has a ratio (iV(SF) / iV(CF)) of the intrinsic viscosity of the soluble fraction iV(SF) to the intrinsic viscosity of the crystalline fraction iV(CF) in the range of 1.7 to 3.0, more preferably in the range of from 1.8 to 2.8, more preferably from 2.0 to 2.6, wherein the intrinsic viscosities are determined by crystallisation extraction analysis (CRYSTEX).

[0057] In this embodiment, the ratio (iV(SF) / iV(CF)) of the heterophasic polypropylene is preferably very close to the ratio (iV(SF) / iV(CF)) of the composition, indicating that the LLDPE has only a small influence on the intrinsic viscosities of the composition.

[0058] The polypropylene homopolymer (H-PP) preferably has a MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 20 to 100 g / 10 min, more preferably 25 to 90 g / 10 min, yet more preferably 30 to 80 g / 10 min.

[0059] The heterophasic polypropylene preferably has a MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 4 to 25 g / 10 min, preferably 6 to 20 g / 10 min, more preferably 7 to 15 g / 10 min.

[0060] The melt flow rate MFR2 of the polypropylene homopolymer (H-PP) is preferably higher than the MFR2 of the heterophasic polypropylene. In a preferred embodiment, the composition comprises the LLDPE in an amount in the range of 1.0 to 15.0 wt.-%, preferably 1.2 to 12.0 wt.-%, more preferably 1.5 to 10.0 wt.-%, based on the total weight of the composition; and

[0061] - the heterophasic polypropylene in an amount in the range of 70 to 99 wt.- %, preferably 77 to 98 wt.-%, more preferably 82 to 97 wt.-%, based on the total weight of the composition.

[0062] In a preferred embodiment, the composition consists of the heterophasic polypropylene, the linear low density polyethylene (LLDPE) and optionally additives.

[0063] Preferably, the composition comprises the LLDPE in an amount in the range of 1.0 to 15.0 wt.-%, preferably 1.2 to 12.0 wt.-%, more preferably 1.5 to 10.0 wt.-%, based on the total weight of the composition; the H-PP in an amount in the range of 50 to 80 wt.-%, such as 50 to 79 wt.-%, preferably 52 to 75 wt.-%, such as 52 to 73.8 wt.-%, more preferably 54 to 70 wt.-%, such as 54 to 68.5 wt.-%, based on the total weight of the composition; and

[0064] - the EPC in an amount in the range of 20 to 45 wt.-%, preferably of 25 to 42 wt.-%, more preferably of 28 to 38 wt.-%, based on the total weight of the composition.

[0065] In a preferred embodiment, the composition consists of the polypropylene homopolymer (H-PP), the ethylene-propylene copolymer (EPC), the linear low density polyethylene (LLDPE) and optionally additives.

[0066] Additives are commonly used in the composition according to the present invention for stabilization and homogenization. Preferably, the additives are selected from one or more of antioxidant(s), UV stabilizer(s), slip agent(s), nucleating agent(s), pigment(s), lubricant(s), masterbatch polymer(s) and / or anti-fogging agents and combinations thereof. These additives are well known in the polymer industry and their use will be familiar to the skilled practitioner. Such additives are generally commercially available and are described, for example, in "Plastic Additives Handbook", pages 871 to 873, 5th edition, 2001 of Hans Zweifel.

[0067] Any additives, which are present, may be added as an isolated raw material or in a mixture with a carrier polymer, i.e. in a so-called master batch.

[0068] Additives are usually present in the composition in an amount of from 0.1 to 5.0 wt.-%, more preferably in an amount of from 0.5 to 3.5 wt.-%, based on the total weight of the composition.

[0069] Accordingly, in a preferred embodiment, the composition consists of the polypropylene homopolymer (H-PP) in an amount of 54 to 70 wt.-%, the elastomeric ethylene-propylene copolymer (EPC) in an amount of 28 to 38 wt.-%, the linear low density polyethylene (LLDPE) in an amount of 1.5 to 10.0 wt.-%, and additives in an amount of from 0.5 to 3.5 wt.-%, wherein all weight-percentages are based on the total weight of the composition.

[0070] Process for obtaining the composition

[0071] In a further aspect of the invention, a process for obtaining the composition as described above is provided.

[0072] The process comprises the steps of a) polymerizing a polypropylene homopolymer (H-PP) and a ethylenepropylene copolymer (EPC) successively in the presence of a Ziegler- Natta catalyst system in a multistage process comprising at least two polymerization reactors connected in series, thereby forming the heterophasic polypropylene; b) melt-blending the heterophasic polypropylene obtained in step a) with the linear low density polyethylene (LLDPE) and optional additives.

[0073] Step a):

[0074] In the multistage process, the propylene homopolymer (H-PP) is preferably produced in at least one first polymerization step and in at least one subsequent polymerization step the ethylene-propylene copolymer (EPC) is produced in the presence of said propylene homopolymer (H-PP).

[0075] In a particular preferred embodiment, the propylene homopolymer (H-PP) is produced at least in a slurry phase reactor and subsequently the ethylene-propylene copolymer (EPC) are produced at least in a gas phase reactor.

[0076] Accordingly, the heterophasic polypropylene can be typically produced in a cascade of at least 2 reactors, preferably at least 3 reactors, more preferably at least 4 reactors, where the first reactor is a liquid bulk reactor preferably of loop design and all subsequent reactors are gas phase reactors, preferably of fluidized bed design. The number of subsequent reactors is typically not more than 6, preferably not more than 5. Preferably, the heterophasic polypropylene is produced in a cascade of 4 reactors.

[0077] A preferred multistage process is a “loop-gas phase”-process, as developed by Borealis (known as BORSTAR® technology) and is described e.g. in patent literature, such as in EP 0 887 379, WO 92 / 12182 WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or in WO 00 / 68315.

[0078] A further suitable slurry-gas phase process is the Spheripol® process of Basell.

[0079] Preferably, the components produced in the first two reactors are crystallizable propylene homopolymers (H-PP), while the components produced in subsequent third and fourth reactor are a predominantly amorphous ethylene-propylene copolymer (EPC) with higher amounts of ethylene comonomer. Small amounts of crystalline polyethylene can be formed simultaneously with the EPC.

[0080] In a preferred embodiment, the heterophasic polypropylene is obtainable by the process comprising the steps of

[0081] I. Polymerizing propylene in the presence of the Ziegler-Natta catalyst system in a first polymerization reactor for producing a first propylene homopolymer fraction;

[0082] II. Transferring a polymerization mixture comprising the Ziegler-Natta catalyst system and the first propylene homopolymer fraction from the first polymerization reactor to a second polymerization reactor;

[0083] III. Polymerizing propylene in the presence of the Ziegler-Natta catalyst system in the second polymerization reactor for producing a second propylene homopolymer fraction; IV. Transferring a polymerization mixture comprising the Ziegler-Natta catalyst system and the first and second propylene homopolymer fractions from the second polymerization reactor to a third polymerization reactor;

[0084] V. Polymerizing propylene and ethylene in the presence of the Ziegler-Natta catalyst system in the third polymerization reactor for producing a first ethylene- propylene copolymer;

[0085] VI. Transferring a polymerization mixture comprising the Ziegler-Natta catalyst system, the first and second propylene homopolymer fractions and the first ethylene-propylene copolymer from the third polymerization reactor to a fourth polymerization reactor; VII. Polymerizing propylene and ethylene in the presence of the Ziegler-Natta catalyst system in the fourth polymerization reactor for producing a second ethylene-propylene copolymer;

[0086] VIII. Withdrawing a polymerization mixture comprising the Ziegler-Natta catalyst system, the first and second propylene homopolymer fractions and the first and second ethylene-propylene copolymer from the fourth polymerization reactor; and

[0087] IX. Obtaining the heterophasic polypropylene comprising the first and second propylene homopolymer fractions and the first and second ethylene-propylene copolymer;

[0088] The first polymerization reactor preferably is a slurry phase reactor, such as a loop reactor.

[0089] It is preferred that the operating temperature in the first polymerization reactor, preferably the loop reactor, is in the range from 62 to 85 °C, more preferably in the range from 65 to 82 °C, still more preferably in the range from 67 to 80 °C.

[0090] Typically, the pressure in the first polymerization reactor, preferably in the loop reactor, is in the range from 20 to 80 barg, preferably 30 to 70 barg, like 35 to 65 barg.

[0091] It is preferred that in the first polymerization reactor, preferably the loop reactor, a propylene homopolymer is produced. Thus, it is preferred that the first polypropylene fraction is a first propylene homopolymer fraction.

[0092] Preferably hydrogen is added in the first polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR2. Preferably, the hydrogen to propylene ratio (H2 / C3 ratio) in the first polypropylene reactor, preferably the loop reactor, is in the range from 5.0 to 20.0 mol / kmol, more preferably from 8.0 to 15.0 mol / kmol.

[0093] It is preferred that the first propylene polymer fraction has a melt flow rate MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 20 to 120 g / 10 min, preferably in the range of 30 to 110 g / 10 min, more preferably in the range of 40 to 90 g / 10 min. The second polymerization reactor preferably is a first gas phase reactor, such as a first fluidized bed gas phase reactor.

[0094] It is preferred that the operating temperature in the second polymerization reactor, preferably the first gas phase reactor, is in the range from 55 to 85 °C, more preferably in the range from 65 to 75 °C.

[0095] Typically, the pressure in the second polymerization reactor, preferably in the first gas phase reactor, is in the range from 5 to 50 barg, preferably from 15 to 40 barg.

[0096] It is preferred that in the second polymerization reactor, preferably the first gas phase reactor, a propylene homopolymer is produced. Thus, it is preferred that the second propylene polymer fraction is a second propylene homopolymer fraction.

[0097] Preferably hydrogen is added in the second polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR2. Preferably the hydrogen to propylene ratio (H2 / C3 ratio) in the second polypropylene reactor, preferably the first gas phase reactor, is in the range from 60 to 200 mol / kmol, more preferably from 100 to 150 mol / kmol.

[0098] It is preferred that the combined first and second propylene polymer fractions have a melt flow rate MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 20 to 100 g / 10 min, preferably in the range of 25 to 90 g / 10 min, more preferably in the range of 30 to 80 g / 10 min.

[0099] The third polymerization reactor preferably is a second gas phase reactor, such as a second fluidized bed gas phase reactor.

[0100] It is preferred that the operating temperature in the third polymerization reactor, preferably the second gas phase reactor, is in the range from 70 to 90 °C, more preferably in the range from 75 to 85 °C. Preferably, the operating temperature in third polymerization reactor is higher than the operating temperature in the second polymerization reactor.

[0101] Typically, the pressure in the third polymerization reactor, preferably in the second gas phase reactor, is in the range from 5 to 40 kPa, preferably from 10 to 30 kPa.

[0102] In the third polymerization reactor, preferably the second gas phase reactor, a ethylene propylene copolymer is produced. Thus, the third propylene polymer fraction is a first ethylene propylene copolymer fraction.

[0103] The ethylene to propylene ratio (C2 / C3 ratio) in the third polymerization reactor, preferably the second gas phase reactor, is in the range from 200 to 1000 mol / kmol, more preferably from 350 to 650 mol / kmol.

[0104] Preferably hydrogen is added in the third polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR2.

[0105] Preferably, the hydrogen to ethylene ratio (H2 / C2 ratio) in the third polymerization reactor, preferably the second gas phase reactor, is in the range from 20 to 120 mol / kmol, more preferably from 40 to 80 mol / kmol.

[0106] It is preferred that the combined first, second and third polypropylene fractions have a melt flow rate MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 7 to 60 g / 10 min, preferably in the range of 8 to 50 g / 10 min, more preferably in the range of 9 to 40 g / 10 min.

[0107] The fourth polymerization reactor preferably is a third gas phase reactor, such as a third fluidized bed gas phase reactor.

[0108] It is preferred that the operating temperature in the fourth polymerization reactor, preferably the third gas phase reactor, is in the range from 70 to 90 °C, more preferably in the range from 75 to 85 °C. Preferably, the operating temperature in the fourth polymerization reactor is higher than the operating temperature in the second polymerization reactor.

[0109] Typically, the pressure in the fourth polymerization reactor, preferably in the third gas phase reactor, is in the range from 5 to 40 kPa, preferably from 10 to 30 kPa.

[0110] In the fourth polymerization reactor, preferably the third gas phase reactor, a ethylene propylene copolymer is produced. Thus, the fourth propylene polymer fraction is a second ethylene propylene copolymer fraction.

[0111] The ethylene to propylene ratio (C2 / C3 ratio) in the fourth polymerization polymerization reactor, preferably the third gas phase reactor, is in the range from 200 to 1000 mol / kmol, more preferably from 350 to 650 mol / kmol.

[0112] Preferably hydrogen is added in the fourth polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR2. Preferably, the hydrogen to ethylene ratio (H2 / C2 ratio) in the fourth polymerization reactor, preferably the third gas phase reactor, is in the range from 20 to 120 mol / kmol, more preferably from 40 to 80 mol / kmol.

[0113] It is preferred that the combined first, second, third and fourth polymer fractions have a melt flow rate MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 4 to 25 g / 10 min, more preferably 6 to 20 g / 10 min, yet more preferably 7 to 15 g / 10 min.

[0114] Further the combined first, second, third and fourth polymer fractions preferably have a total ethylene (C2) content in the range of 10.0 wt.-% to 30 wt.-%, preferably in the range of 12.0 to 28.0 wt.-%, more preferably of 13.0 to 25.0 wt.-%, based on the total weight of the combined first, second, third and fourth polymer fractions, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy. The combined first, second, third and fourth propylene polymer fractions preferably form a heterophasic polypropylene.

[0115] The preparation of the first, second, third and fourth polymer fractions can comprise in addition to the (main) polymerization stages in the at least four polymerization reactors prior thereto a pre-polymerization in a pre-polymerization reactor upstream to the first polymerization reactor.

[0116] In the pre-polymerization reactor, a polypropylene is produced. The pre- polymerization is preferably conducted in the presence of the Ziegler-Natta catalyst system. According to this embodiment, the Ziegler-Natta catalyst system is introduced to the pre-polymerization step. However, this shall not exclude the option that at a later stage for instance further co-catalyst is added in the polymerization process, for instance in the first reactor. In one embodiment, all components of the Ziegler-Natta catalyst system are only added in the pre-polymerization reactor, if a pre-polymerization is applied.

[0117] The pre-polymerization reaction is typically conducted at a temperature of 0 to 60 °C, preferably from 10 to 40 °C, and more preferably from 12 to 30 °C.

[0118] The pressure in the pre-polymerization reactor is not critical but must be sufficiently high to maintain the reaction mixture in liquid phase. Thus, the pressure may be from 20 to 100 kPa, for example from 30 to 70 kPa.

[0119] In a preferred embodiment, the pre-polymerization is conducted as bulk slurry polymerization in liquid propylene, i.e. the liquid phase mainly comprises propylene, optionally with inert components dissolved therein. It is possible to add other components also to the pre-polymerization stage. Thus, hydrogen may be added into the pre-polymerization stage to control the molecular weight of the polypropylene as is known in the art. Further, antistatic additives may be used to prevent the particles from adhering to each other or to the walls of the reactor.

[0120] The precise control of the pre-polymerization conditions and reaction parameters is within the skill of the art.

[0121] Due to the above defined process conditions in the pre-polymerization, preferably a mixture of the Ziegler-Natta catalyst system and the polypropylene produced in the pre-polymerization reactor is obtained. Preferably, the Ziegler-Natta catalyst system is (finely) dispersed in the polypropylene. In other words, the Ziegler-Natta catalyst system introduced in the pre-polymerization reactor are split into smaller fragments that are evenly distributed within the growing polypropylene. The sizes of the introduced Ziegler-Natta catalyst system as well as of the obtained fragments are not of essential relevance for the instant invention and within the skilled knowledge. As mentioned above, if a pre-polymerization is used, subsequent to said pre- polymerization, the mixture of the Ziegler-Natta catalyst system and the polypropylene produced in the pre-polymerization reactor is transferred to the first polymerization reactor. Typically, the total amount of polypropylene produced in the pre-polymerization reactor is rather low and typically not more than 5.0 wt.-%, more preferably not more than 4.0 wt.-%, still more preferably in the range from 0.5 to 4.0 wt.-%, like in the range 1.0 of to 3.0 wt.-%, based on the total combined weight of the first, second, third and fourth polymer fractions.

[0122] In case that pre-polymerization is not used, propylene and the other ingredients such as the Ziegler-Natta catalyst system can be directly introduced into the first polymerization reactor. The residence times of the polymerization mixtures in the different polymerization stages are adjusted to obtain the amounts of the first, second, third and fourth polymer fractions in the combined first, second, third and fourth polymer fractions.

[0123] Preferably, the first polymer fraction is present in an amount of from 25 to 50 wt.-%, more preferably from 32 to 45 wt.-%, based on the total weight of the combined first, second, third and fourth propylene polymer fractions. The amount of the polypropylene produced in the pre-polymerization reactor, if present, is generally added to the amount of the first propylene polymer fraction.

[0124] Preferably, the second polymer fraction is present in an amount of from 17 to 32 wt.- %, more preferably from 20 to 30 wt.-%, based on the total weight of the combined first, second, third and fourth propylene polymer fractions.

[0125] Preferably the third polymer fraction is present in an amount of from 16 to 31 wt.-%, more preferably from 19 to 29 wt.-%, based on the total weight of the combined first, second, third and fourth propylene polymer fractions.

[0126] Preferably the fourth propylene polymer fraction is present in an amount of from 4 to 20 wt.-%, more preferably from 8 to 16 wt.-%, based on the total weight of the combined first, second, third and fourth polymer fractions.

[0127] According to the invention, the heterophasic polypropylene is preferably obtained by a multistage polymerization process, as described above, in the presence of a Ziegler- Natta catalyst system.

[0128] As pointed out above in the specific process for the preparation of the heterophasic polypropylene as defined above, a specific Ziegler-Natta catalyst is preferably used. The preferred Ziegler-Natta catalyst system of this invention is described in more detail in WO 2016 / 066446 Al, or WO 2023 / 180272 Al, which are incorporated by reference. All preferred embodiments of the Ziegler-Natta catalyst system described in these disclosures are also preferred embodiments of the Ziegler-Natta catalyst system for the present invention.

[0129] Step b):

[0130] In step b) the heterophasic polypropylene obtained in step a) is melt-blended with the linear low density polyethylene (LLDPE) as described above or below and optionally with further additives.

[0131] The LLDPE is preferably produced in a slurry phase reactor, such as a loop reactor. It is preferred that the operating temperature in the slurry phase reactor, preferably the loop reactor, is in the range from 65 to 100 °C, more preferably in the range from 70 to 95 °C, still more preferably in the range from 80 to 90 °C.

[0132] Typically, the pressure in the slurry phase reactor, preferably the loop reactor, is in the range from 2000 to 8000 kPa, preferably from 4000 to 7500 kPa barg, like from 3000 to 6500 kPa.

[0133] Preferably hydrogen is added in the slurry phase reactor in order to control the molecular weight, i.e. the melt flow rate MFR2. Preferably, the hydrogen to propylene ratio (H2 / C2 ratio) in the slurry phase reactor, preferably the loop reactor, is in the range from 20.0 to 100.0 mol / kmol, more preferably from 45.0 to 85.0 mol / kmol.

[0134] The LLDPE is preferably a copolymer of ethylene and butene. Accordingly, butene is preferably also present in the slurry phase reactor.

[0135] The butene to ethylene ratio (C4 / C2 ratio) in slurry phase reactor, preferably loop reactor, is in the range from 7000 to 15000 mol / kmol, more preferably from 9000 to 13000 mol / kmol. The preparation of the LLDPE can comprise in addition to the main polymerization stage in the slurry phase reactor, preferably loop reactor, prior thereto a prepolymerization in a pre-polymerization reactor upstream to the first polymerization reactor.

[0136] The precise control of the pre-polymerization conditions and reaction parameters is within the skill of the art.

[0137] Additives that can be blended with the heterophasic polypropylene in addition to the LLDPE are known to in the art and are described above.

[0138] LLDPE

[0139] In another aspect of the invention, a linear low density polyethylene (LLDPE) is provided.

[0140] This LLDPE can be used to improve the impact strength at low temperatures of heterophasic polypropylenes, as described above, without significantly affecting the iV(SF) / iV(CF), the C2(SF) or the (SF) content of the heterophasic polypropylenes.

[0141] The MFR2(190°C, 2.16 kg, ISO 1133) of the LLDPE is in the range of 50 to 500 g / 10 min, such as 200 to 500 g / 10 min, preferably 80 to 450 g / 10 min, such as 210 to 450 g / 10 min, more preferably 100 to 400 g / 10 min, such as 220 to 400 g / 10 min.

[0142] Further, the LLDPE has a melting point Tm, determined by differential scanning calorimetry (DSC) according to ISO 11357 / part 3 / method C2, in the range of 113 to 127 °C, preferably 115 to 125 °C, more preferably 117 to 123 °C.

[0143] The density of the LLDPE, measured according to ISO 1183-1 :2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, is in the range of 935 to 950 kg / m3, preferably 938 to 947 kgm3, more preferably 940 to 946 kg / m3. It is preferred, that the LLDPE is a copolymer of ethylene and butene. In this embodiment, it is preferred that the LLDPE has a total content of units derived from butene (C4) in the range of 0.5 to 10.0 wt.-%, preferably 1.0 to 8.0 wt.-%, more preferably 2.0 to 5.0 wt.-%, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy.

[0144] It is also preferred that the intrinsic viscosity of the LLDPE (IVLLDPE), determined according to ISO 1628-3, is in the range of 0.50 to 1.50 dl / g, more preferably of 0.55 to 1.20 dl / g, yet more preferably of 0.60 to 1.00 dl / g.

[0145] Article

[0146] The composition of this invention comprising a heterophasic polypropylene and a linear low density polyethylene exhibits a very good balance of mechanical properties and is therefore ideal for use in articles.

[0147] Accordingly, one aspect of the invention pertains to an article, preferably an automotive article comprising, preferably consisting of the composition as described above. Preferred articles are functional elements of the automotive interior and interior trims like pillar trims, dashboard elements, central consoles and the like.

[0148] Examples

[0149] The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

[0150] 1. Measurement methods a) Melt Flow Rate (MFR2)

[0151] The melt flow rate MFR2 of propylene based polymers is measured at 230°C with a load of 2.16 kg according to ISO 1133.

[0152] The melt flow rate MFR2 of the ethylene based polymers is measured at 190°C with a load of 2.16 kg according to ISO 1133. b) Density

[0153] The density is measured according to ISO 1183-1 :2004 Method A on compression molded specimen prepared according to EN ISO 1872-2 and is given in g / cm3. c) Comonomer content

[0154] Comonomer content quantification of poly(propylene-co-ethylene) copolymers Quantitativel 3C { 'H } NMR spectra were recorded in the solution-state using a B inker Avance NEO 400 NMR spectrometer operating at 400.15 and 100.62 MHz for 'H and13C respectively. All spectra were recorded using a13C optimised 10 mm extended temperature probe head at 125°C using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 7,2-tetrachloroethane-t / 2 (TCE-t / j) along with chromium-(III)-acetylacetonate (Cr(acac)s) resulting in a 60 mM solution of relaxation agent in solvent {8} and with approximately 3 mg BHT (2,6-di-tert-butyl-4-methylphenol CAS 128-37-0). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatory oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bilevel WALTZ16 decoupling scheme {3, 4}. A total of 6144 (6k) transients were acquired per spectra.

[0155] Quantitative13C J1H } NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed {7}.

[0156] The comonomer fraction was quantified using the method of Wang et. al. {6} through integration of multiple signals across the whole spectral region in the13C {1H } spectra. This method was chosen for its robust nature and ability to account for the presence of regiodefects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents. For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:

[0157] E = 0.5 (SPP + SPy + SP5 + 0.5(SaP + Say))

[0158] Through the use of this set of sites the corresponding integral equation becomes:

[0159] E = 0.5 (In +IG + 0.5(IC + ID)) using the same notation used in the article of Wang et al. {6}. Equations used for absolute propylene content were not modified.

[0160] The mole percent comonomer incorporation was calculated from the mole fraction:

[0161] E [mol%] = 100 * fE

[0162] The weight percent comonomer incorporation was calculated from the mole fraction: E [wt.-%] = 100 * (fE * 28.06 ) / ( (fE * 28.06) + ((1-fE) * 42.08) ) Bibliographic references:

[0163] 1) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443.

[0164] 2) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30 (1997) 6251.

[0165] 3) Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225.

[0166] 4) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128.

[0167] 5) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

[0168] 6) Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157.

[0169] 7) Cheng, H. N., Macromolecules 17 (1984), 1950.

[0170] 8) Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475.

[0171] 9) Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150.

[0172] 10) Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201.

[0173] 11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253. d) Differential scanning analysis (DSC)

[0174] Melting peak temperatures (TP,m), melting enthalpies (Hm), crystallization peak temperature (TP,C) and crystallization enthalpy (Hc) were measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC was run according to ISO 11357 / part 3 / method C2 in a heat / cool / heat cycle with a scan rate of 10 °C / min in the temperature range of -30 - 26 - to +225 °C. Crystallization peak temperature (TP,C) and crystallization enthalpy (Hc) were determined from the cooling step, while the two melting peak temperatures (Tmi) and (Tm2) and two melting enthalpies (Hmi) and (Hm2) were determined from the second heating step. e) Crystallization extraction (CRYSTEX)

[0175] Note: Crystallization extraction (CRYSTEX) analyses the polymeric part of each component, with non-polymeric parts, such as any fillers or particulate pigments, not contributing to the reported CRYSTEX data presented.

[0176] Determination of crystalline and soluble fractions and their respective properties (iV and Ethylene content)

[0177] The crystalline (CF) and soluble fractions (SF) of the polypropylene (PP) compositions as well as the comonomer content and intrinsic viscosities of the respective fractions were analyzed by use of the Crystex (crystallisation extraction) method. Potential instruments that can be used are Crystex QC or Crystex 42 (Polymer Char; Valencia, Spain). Details of the technique and the method can be found in literature (Ljiljana Jeremie, Andreas Albrecht, Martina Sandholzer & Markus Gahleitner (2020): Rapid characterization of high-impact ethylenepropylene copolymer composition by crystallization extraction separation: comparability to standard separation methods, International Journal of Polymer Analysis and Characterization, 25:8, 581-596).

[0178] The crystalline and amorphous (soluble) fractions are separated through temperature cycles of dissolution at 160°C, crystallization at 40°C and re-dissolution in 1,2,4- tri chlorobenzene at 160°C. Quantification of SF and CF and determination of ethylene content (C2) are achieved by means of an integrated infrared detector (IR4) and for the determination of the intrinsic viscosity (iV) an online 2-capillary viscometer is used.

[0179] IR4 detector is a multiple wavelength detector measuring IR absorbance at two different bands (CH3 stretching vibration (centred at app. 2960 cm’1) and the CH stretching vibration (2700-3000 cm’1) that are serving for the determination of the concentration and the Ethylene content in Ethylene-Propylene copolymers. IR4 detector is calibrated with series of 8 EP copolymers with known Ethylene content in the range of 2 wt.-% to 69 wt.-% (determined by13C-NMR) and each at various concentrations, in the range of 2 and 13mg / ml. To encounter for both features, concentration and ethylene content at the same time for various polymer concentration expected during Crystex analyses the following calibration equations were applied:

[0180] Cone = a + b*Abs(CH) + c*(Abs(CH))2+ d*Abs(CH3) + e*(Abs(CH3)2+ f*Abs(CH)*Abs(CH3) (Equation 1)

[0181] CH3 / 1000C = a + b*Abs(CH) + c* Abs(CH3) + d * (Abs(CH3) / Abs(CH)) + e * (Abs(CH3) / Abs(CH))2(Equation 2)

[0182] The constants a to f for equation 1 and a to e for equation 2 were determined by using least square regression analysis.

[0183] The CH3 / 1000C is converted to the ethylene content in wt.-% using following relationship: wt.-% (Ethylene in EP Copolymers) = 100 - CH3 / 1000TC * 0.3 (Equation 3)

[0184] Amount of Soluble Fraction (SF) and Crystalline Fraction (CF) are correlated through the XS calibration to the “Xylene Cold Soluble” (XCS) quantity and respectively Xylene Cold Insoluble (XCI) fractions, determined according to standard gravimetric method as per ISO16152. XS calibration is achieved by testing various EP copolymers with XS content in the range 2-31 wt.-%. A linear calibration curve is used.

[0185] Intrinsic viscosity (iV) of the parent EP copolymer and its soluble and crystalline fractions are determined with a use of an online 2-capillary viscometer and are correlated to corresponding iV’s determined by standard method in decalin according to ISO 1628-3. Calibration is achieved with various EP copolymers and PP polymers with iV = 2-4 dL / g. The determined calibration curve is linear.

[0186] The samples to be analyzed are weighed out in concentrations of 10 mg / ml to 20 mg / ml. After automated filling of the vial with 1,2,4-TCB containing 250 mg / 1 2,6- tert-butyl-4-methylphenol (BHT) as antioxidant, the sample is dissolved at 170°C until complete dissolution is achieved with either constant stirring or gentle shaking. To avoid sample degradation, polymer solution is blanketed with the N2 atmosphere during dissolution.

[0187] For PP composition containing inorganic fillers or pigments or any other non-TCB soluble polymeric substances removal of these is required. This can be done by hot filtration prior injection.

[0188] A defined volume of the polymer solution is injected into the column filled with inert support where the crystallization of the sample and separation of the soluble fraction from the crystalline fraction is taking place. This process is repeated two times. During the first injection the whole sample is measured at high temperature, determining the iV [dl / g] and the C2 [wt.-%] of the PP composition. During the second injection the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle are measured (wt.-% SF, wt.-% C2, iV). f) Flexural Modulus

[0189] The flexural properties were determined acc. to ISO 178 method A (3-point bending test) on 80 x 10 x 4 mm3specimens. Following the standard, a test speed of 2 mm / min and a span length of 16 times the thickness was used. The testing temperature was 23±2° C. Injection moulding was carried out according to ISO 19069-2 using a melt temperature of 230°C for all materials irrespective of material melt flow rate. g) Tensile Modulus

[0190] The tensile properties were determined on injection molded dogbone specimens prepared in accordance with ISO 527-2 using a melt temperature of 230 °C. Tensile modulus was determined according to ISO 527-1,-2 at 1 mm / min and 23°C. To determine stress at yield and strain at yield, a speed of 50 mm / min. was used. h) Charpy notched impact strength (NISI

[0191] The Charpy notched impact strength was determined acc. to ISO 179-1 / leA on notched 80 * 10 x 4 mm3specimens (specimens were prepared according to ISO 179-1 / leA). Testing temperatures were 23±2° C or -20±2° C. Injection moulding was carried out acc. to ISO 19069-2 using a melt temperature of 230°C for all materials irrespective of material melt flow rate. i) Xylene cold solubles (XCS) content

[0192] The quantity of xylene soluble matter in polypropylene is determined according to the ISO16152 (first edition; 2005-07-01).

[0193] A weighed amount of a sample is dissolved in hot xylene under reflux conditions at 135°C. The solution is then cooled down under controlled conditions and maintained at 25°C for 30 minutes to ensure controlled crystallization of the insoluble fraction. This insoluble fraction is then separated by filtration. Xylene is evaporated from the filtrate leaving the soluble fraction as a residue. The percentage of this fraction is determined gravimetrically.

[0194] 100 where mo is the mass of the sample test portion weighed, in grams mi is the mass of residue, in grams vo is the original volume of solvent taken vi is the volume of the aliquot taken for determination. j) Coefficient of linear thermal expansion (CLTE)

[0195] The coefficient of linear thermal expansion (CLTE) was determined in accordance with ISO 11359-2: 1999 on 10 mm long pieces cut from the core of the same injection molded specimens as used for the flexural modulus determination. The measurement was performed in a temperature range from -30 to +80°C at a heating rate of 1 °C / min and in a temperature range from +23 to +80°C at a heating rate of 1 °C / min, respectively. k) Instrumented Puncture Test (Puncture energy)

[0196] Instrumented puncture test was performed on 60 x 60 x 3 mm3injection-molded plaques at 23°C and -20°C according to ISO 6603-2:2000. The measurement was done after 96 h conditioning time of the specimen at 23 °C, -20 °C and -30 °C. l) Comonomer content LLDPE

[0197] The butene (C4) content of the LLDPE was determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy.

[0198] Quantification of microstructure by NMR spectroscopy (for calibration purposes)

[0199] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymers.

[0200] Quantitativel 3C { ' H } NMR spectra recorded in the molten-state using a Bruker Avance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for ' H and13C respectively. All spectra were recorded using a13C optimised 7 mm magic-angle spinning (MAS) probe head at 150°C using nitrogen gas for all pneumatics.

[0201] Approximately 200 mg of material was packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4 kHz. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification (Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2006;207:382., Parkinson, M., Klimke, K., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2007;208:2128., Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373). Standard single-pulse excitation was employed utilising the transient NOE at short recycle delays of 3 s (Pollard, M., Klimke, K., Graf, R., Spiess, H.W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004;37:813., Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2006;207:382.) and the RS-HEPT decoupling scheme (Filip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005, 176, 239, Griffin, J.M., Tripon, C., Samoson, A., Filip, C., and Brown, S.P., Mag. Res. in Chem. 200745, SI, SI 98). A total of 1024 (Ik) transients were acquired per spectrum.

[0202] Quantitativel 3C { ' H J NMR spectra were processed, integrated and quantitative properties determined using custom spectral analysis automation programs. All chemical shifts are internally referenced to the bulk methylene signal (5+) at 30.00 ppm (J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201).

[0203] Characteristic signals corresponding to the incorporation of 1 -butene were observed (J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201.) and all contents calculated with respect to all other monomers present in the polymer.

[0204] Characteristic signals resulting from isolated 1-butene incorporation i.e. EEBEE comonomer sequences, were observed. Isolated 1-butene incorporation was quantified using the integral of the signal at 39.8 ppm assigned to the *B2 sites, accounting for the number of reporting sites per comonomer:

[0205] B = I*B2

[0206] When characteristic signals resulting from consecutive 1-butene incorporation i.e. EBBE comonomer sequences were observed, such consecutive 1-butene incorporation was quantified using the integral of the signal at 39.3 ppm assigned to the aaB2B2 sites accounting for the number of reporting sites per comonomer: BB = 2 * IcraB2B2

[0207] When characteristic signals resulting from non-consecutive 1-butene incorporation i.e. EBEBE comonomer sequences were also observed, such non-consecutive 1- butene incorporation was quantified using the integral of the signal at 24.7 ppm assigned to the 00B2B2 sites accounting for the number of reporting sites per comonomer:

[0208] BEB = 2 * IppB2B2

[0209] Due to the overlap of the *B2 and *0B2B2 sites of isolated (EEBEE) and non- consecutively incorporated (EBEBE) 1 -butene respectively the total amount of isolated 1 -butene incorporation is corrected based on the amount of non-consecutive 1 -butene present:

[0210] B = I*B2 - 2 * IppB2B2

[0211] With no other signals indicative of other comonomer sequences, i.e. 1-butene chain initiation, observed the total 1-butene comonomer content was calculated based solely on the amount of isolated (EEBEE), consecutive (EBBE) and non-consecutive (EBEBE) 1-butene comonomer sequences:

[0212] Btotai = B + BB + BEB

[0213] Characteristic signals resulting from saturated end-groups were observed. The content of such saturated end-groups was quantified using the average of the integral of the signals at 22.8 and 32.2 ppm assigned to the 2s and 3s sites respectively:

[0214] S =(l / 2)*( I2S + I3S )

[0215] The relative content of ethylene was quantified using the integral of the bulk methylene (5+) signals at 30.00 ppm:

[0216] E=(1 / 2)*I5+

[0217] The total ethylene comonomer content was calculated based the bulk methylene signals and accounting for ethylene units present in other observed comonomer sequences or end-groups:

[0218] Etotai = E + (5 / 2)*B + (7 / 2)*BB + (9 / 2)*BEB + (3 / 2)*S

[0219] The total mole fraction of 1-butene in the polymer was then calculated as: fB=Btotai / ( Etotal + Btotai )

[0220] The total comonomer incorporation of 1-butene in mole percent was calculated from the mole fraction in the usual manner:

[0221] B [mol%] = 100 * fB The total comonomer incorporation of 1 -butene in weight percent was calculated from the mole fraction in the standard manner:

[0222] B [wt%] = 100 * ( ffl * 56.11) / ( (ffl * 56.11) + ((1 - ffl) * 28.05) ) m) Intrinsic viscosity (i V)

[0223] The intrinsic viscosity, iV, of the LLDPE is determined according to ISO 1628-3: “Determination of the viscosity of polymers in dilute solution using capillary viscometers”. The solvent used is decalin at a temperature of 135°C.

[0224] Examples

[0225] Preparation of the heterophasic polypropylene powders

[0226] Catalyst system for heterophasic polypropylenes:

[0227] For the polymerization process of heterophasic polypropylene powders, a Ziegler- Natta type catalyst (ZN1) as used and described for the inventive examples of WO 2016 / 066446 Al, pre-polymerized with vinylcyclohexane to achieve nucleation with poly(vinylcyclohexane) was used.

[0228] Nucleation by prepolymerization with vinylcyclohexane is described in EP 2 960 256 Bl and EP 2 960 279 Bl in detail. These documents are incorporated by reference.

[0229] Polymerization of heterophasic polypropylenes

[0230] The heterophasic polypropylenes (PPI to PP3) were made in prepolymerization / loop reactor / gas phase reactor 1 / gas phase reactor 2 / gas phase reactor 3 configuration. The catalyst systems defined above was used in combination with triethyl-aluminium (TEAL) as co-catalyst and dicyclopentadienyl-dimethoxy silane (donor D) as external donor. Table 1: Polymerization conditions Jbr the heterophasic polypropylenes PPI, PP2 and PP3.

[0231] Preparation of the linear low density polyethylene LLDPE

[0232] Catalyst system for LLDPE For the polymerization process of the linear low density polyethylene LLDPE, a catalyst system as used and described in WO 2023 / 012257 Al, page 16, CAT1, was used. Polymerization of the linear low density polyethylene LLDPE

[0233] The linear low density polyethylene LLDPE was made in a prepolymerization / loop reactor configuration with the catalyst system as defined above.

[0234] Table 2: Polymerization conditions for the LLDPE.

[0235] Additives

[0236] The amount and type of additives used are as follows:

[0237] 0.15 wt.-% antioxidant (Irganox B215FF from BASF AG, Germany; this is a 1 :2- mixture of Pentaerythrityl-tetrakis(3-(3 ’ ,5 ’ -di -tert, butyl-4-hydroxyphenyl)- propionate, CAS-no. 6683-19-8, and Tris (2,4-di-t-butylphenyl) phosphite, CAS-no. 31570-04-4);

[0238] 0.05 wt.-% Calcium stearate (CAS-no.1592-23-0, commercially available from Faci, Italy),

[0239] 0.33 wt.-% Glycerol monostearate (> 90 wt.-%, Dimodan HP FF),

[0240] 0.07 wt.-% Glycerol monolaurate (> 90 wt.-%, GML90)

[0241] 0.8 wt.-% talcum. Preparation of the Compositions

[0242] The inventive and comparative compositions were obtained by compounding the respective components in a co-rotating twin screw extruder (ZSK57) in amounts according to the following table 3.

[0243] Table 3: Weight percentages of the components of the inventive and compxirative compositions.

[0244] Properties of the Compositions

[0245] In the following table 4, the properties of the inventive and comparative compositions are shown.

[0246] Table 4: Properties of the inventive and comparative compositions TEA to IE3 and CE1 to CE5.

[0247]

[0248] CE1 is a composition with a standard C2-content of the soluble fraction (C2(SF)) of roughly 40 wt.-%. This material shows overall an acceptable mechanical performance. However, the low temperature notched impact strength (NIS@-20°C) is only moderate.

[0249] CE2 has compared to CE1 a lower intrinsic viscosity (iV) at comparable ethylene contents (C2(SF)). This lower iV leads to good dimensional stability but inferior impact performance (NIS). CE4 has compared to CE1 a lower intrinsic viscosity (iV), but higher C2-content of the soluble fraction (C2(SF)). The SF content is a bit lower in CE2 and CE3 compared to CE1.

[0250] The other mechanical properties are hardly affected and CLTE is slightly reduced upon the addition of the LLDPE. What can be easily seen by comparing IE1 to IE3 with CE1 is that upon addition of the LLDPE, the impact strength at low temperatures immediately gets improved (NIS@-20°C). Already addition of 2 wt.-% are sufficient to increase the NIS at -20°C from 14 kJ / m2to 38 kJ / m2. If 5 wt.-% or more are added, the NIS increases further and the fracture type changes to exclusively partial break also at -20 °C. If the same LLDPE is “added” to CE2 or CE4 to obtain CE3 or CE5, the effect on NIS is not pronounced, on CLTE a slight reduction can be seen.

Claims

Claims1. A composition comprising i) a heterophasic polypropylene; and ii) a linear low density polyethylene (LLDPE); in a combined amount of more than 85.0 wt.-%, preferably in the range of 90.0 to 99.5 wt.-%, based on the total weight of the composition; characterized in that the composition has a total content of units derived from ethylene (C2) in the range of 15.0 wt.-% to 35 wt.-%, preferably in the range of 16.0 to 30.0 wt.-%, more preferably of 18.0 to 28.0 wt.-%, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy; a soluble fraction (SF) and a crystalline fraction (CF) according to crystallisation extraction analysis (CRYSTEX); a soluble fraction (SF) content determined by crystallisation extraction analysis (CRYSTEX) in the range of from 25.0 wt.-% to 45.0 wt.-%, preferably from 28.0 to 42.0 wt.-%, more preferably from 30.0 to 40.0 wt.-%; an ethylene content of said soluble fraction C2(SF), as determined by FT- IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, in the range of from 28.0 to 48.0 wt.-%, preferably from 30.0 to 45.0 wt.-%, more preferably from 32.0 to 42.0 wt.-%; a ratio (iV(SF) / iV(CF)) of the intrinsic viscosity of said soluble fraction iV(SF) to the intrinsic viscosity of the crystalline fraction iV(CF) in the range of 1.7 to 3.0, preferably in the range of from 1.8 to 2.8, more preferably from 2.0 to 2.6, wherein the intrinsic viscosities are determined by crystallisation extraction analysis (CRYSTEX).

2. The composition according to claim 1, wherein the composition has an MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 5 to 25 g / 10 min, preferably 6 to 20 g / 10 min, more preferably 7 to 15 g / 10 min.

3. The composition according to any one of the preceding claims, wherein the composition has a crystalline fraction (CF) content determined by crystallisation extraction analysis (CRYSTEX) in the range of from 55.0 wt.-% to 75.0 wt.-%, preferably from 58.0 to 72.0 wt.-%, more preferably from 60.0 to 70.0 wt.-%; an ethylene content of said crystalline fraction C2(CF), as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, in the range of from 8.0 to 25.0 wt.-%, preferably from 9.0 to 23.0 wt.-%, more preferably from 10.0 to 21.0 wt.-%; and an intrinsic viscosity (iV), determined according to ISO 1628-3, in the range of 1.5 to 3.0 dl / g, preferably of 1.7 to 2.7 dl / g, more preferably 1.8 to 3.5 dl / g.

4. The composition according to any one of the preceding claims, wherein the crystalline fraction (CF) has two melting points Tm,i and Tm,2, determined by differential scanning calorimetry (DSC) according to ISO 11357 / part 3 / method C2, wherein the Tm,i is in the range of 113 to 127 °C, preferably 115 to 125 °C, more preferably 117 to 123 °C and the Tm,2 is in the range of 160 to 170 °C, preferably 162 to 168 °C, more preferably 163 to 167 °C.

5. The composition according to any one of the preceding claims, wherein the LLDPE is a copolymer of ethylene and butene; has a density, measured according to ISO 1183-1 :2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 935 to 950 kg / m3, preferably 938 to 947 kgm3, more preferably 940 to 946 kg / m3;and has a melting point Tm, determined by differential scanning calorimetry (DSC) according to ISO 11357 / part 3 / method C2, in the range of 113 to 127 °C, preferably 115 to 125 °C, more preferably 117 to 123 °C.

6. The composition according to any one of the preceding claims, wherein the LLDPE has- a MFR2(190°C, 2.16 kg, ISO 1133) in the range of 50 to 500 g / 10 min, preferably 80 to 450 g / 10 min, more preferably 100 to 400 g / 10 min; and an intrinsic viscosity (IVLLDPE), determined according to ISO 1628-3, in the range of 0.50 to 1.50 dl / g, preferably of 0.55 to 1.20 dl / g, more preferably of 0.60 to 1.00 dl / g.

7. The composition according to any one of the preceding claims, wherein the heterophasic polypropylene comprisesA) a crystalline polypropylene homopolymer (H-PP), andB) an elastomeric ethylene propylene copolymer (EPC) wherein the heterophasic polypropylene has a total content of units derived from ethylene (C2) in the range of 10.0 wt.-% to 30 wt.-%, preferably in the range of 12.0 to 28.0 wt.-%, more preferably of 13.0 to 25.0 wt.-%, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy; a soluble fraction (SF) and a crystalline fraction (CF) according to crystallisation extraction analysis (CRYSTEX); a soluble fraction (SF) content determined by crystallisation extraction analysis (CRYSTEX) in the range of from 25.0 wt.-% to 45.0 wt.-%, preferably from 27.0 to 43.0 wt.-%, more preferably from 29.0 to 41.0 wt.-%; an ethylene content of said soluble fraction C2(SF), as determined by FT- IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, in the range of from 30.0 to 52.0 wt.-%, preferably from 32.0 to 48.0 wt.-%, more preferably from 34.0 to 44.0 wt.-%.

8. The composition according to claim 7, wherein the heterophasic polypropylene hasa ratio (iV(SF) / iV(CF)) of the intrinsic viscosity of said soluble fraction iV(SF) to the intrinsic viscosity of the crystalline fraction iV(CF) in the range of 1.7 to 3.0, preferably in the range of from 1.8 to 2.8, more preferably from 2.0 to 2.6, wherein the intrinsic viscosities are determined by crystallisation extraction analysis (CRYSTEX).

9. The composition according to claims 7 or 8, wherein the polypropylene homopolymer (H-PP) has a MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 20 to 100 g / 10 min, preferably 25 to 90 g / 10 min, more preferably 30 to 80 g / 10 min; and- the heterophasic polypropylene has a MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 4 to 25 g / 10 min, preferably 6 to 20 g / 10 min, more preferably 7 to 15 g / 10 min.

10. The composition according to any one of the preceding claims, wherein the composition comprises the LLDPE in an amount in the range of 1.0 to 15.0 wt.-%, preferably 1.2 to 12.0 wt.-%, more preferably 1.5 to 10.0 wt.-%, based on the total weight of the composition; the H-PP in an amount in the range of 50 to 80 wt.-%, preferably 52 to 75 wt.-%, more preferably 54 to 70 wt.-%, based on the total weight of the composition; and- the EPC in an amount in the range of 20 to 45 wt.-%, preferably of 25 to 42 wt.-%, more preferably of 28 to 38 wt.-%, based on the total weight of the composition.

11. A process for obtaining the composition of any one of the preceding claims, comprising the steps of a) polymerizing a polypropylene homopolymer (H-PP) and a ethylenepropylene copolymer (EPC) successively in the presence of a Ziegler- Natta catalyst system in a multistage process comprising at least twopolymerization reactors connected in series, thereby forming the heterophasic polypropylene; b) melt-blending the heterophasic polypropylene obtained in step a) with the linear low density polyethylene (LLDPE) and optional additives.

12. A linear low density polyethylene (LLDPE), characterized in that the LLDPE has- a MFR2(190°C, 2.16 kg, ISO 1133) in the range of 200 to 500 g / 10 min, preferably 210 to 450 g / 10 min, more preferably 220 to 400 g / 10 min; a melting temperature Tm, determined by differential scanning calorimetry (DSC) according to ISO 11357 / part 3 / method C2, in the range of 113 to 127 °C, preferably 115 to 125 °C, more preferably 117 to 123 °C; and a density, measured according to ISO 1183-1 :2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 935 to 950 kg / m3, preferably 938 to 947 kgm3, more preferably 940 to 946 kg / m3.

13. The linear low density polyethylene (LLDPE) according to claim 12, wherein the LLDPE is a copolymer of ethylene and butene with a content of units derived from butene, as determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, in the range of 0.5 to 10.0 wt.-%, preferably 1.0 to 8.0 wt.-%, more preferably 2.0 to 5.0 wt.-%; and has an intrinsic viscosity (iV), determined according to ISO 1628-3, in the range of 0.50 to 1.50 dl / g, preferably of 0.55 to 1.20 dl / g, more preferably 0.60 to 1.00 dl / g.

14. Use of the linear low density polyethylene (LLDPE) according to any one of claims 12 or 13, for improving the impact strength at low temperatures of heterophasic polypropylenes as specified in any of claims 7 to 9.

15. An article, preferably an automotive article comprising, preferably consisting of the composition according to any one of claims 1 to 10.

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